Too rich with the nitrous

[Dave]

Went to the track yesterday. First run all boost at 20psi and 47psi base fuel pressure the A/F was at 11.4:1 for most of the run.

I changed nothing and kicked on the nitrous. .032N2O/.017Fuel jets on a single fogger in the tube. I came out of the whole got into it and blaaaahhh... At least 10.0:1 if not richer.

Took 5psi out of the base fuel pressure. Went to 11.0:1 still broke up a bit in 1st gear though.

Took another 3psi out and she sat pretty at 11.5:1.

So the problem is if I'm driving around with no nitrous I want to be safe and fast with just boost. But say I want to kick the nitrous on. Well I have to get out and change everything before I can make that happen.

Does anyone have any suggestions of a simpler way to control my fuel with the nitrous? Should I perhaps go to a smaller fuel jet and leave my base pressure at 47psi?

Thanks.

[contraption22]

I would say run the smaller fuel jet in nitrous kit. You don't want to have to be changing fuel pressure when running the nitrous. Find the right fuel pressure where your a/f is happy off the bottle, and then jet the nitrous system accordingly.

Jets are pretty cheap. I would get either .016, .015, and .014 jets for the fuel side, and some .033, .034, and .035 for the nitrous side.

Try one jet at a time, one side at a time until you get closer to where you wanna be.

It doesn't hurt to be a little fat, especially on pump gas.

Also remember to take a degree or two out of your base timing when you anticipate running the spray.

This past weekend my knock lite was flickering when I hit the spray. Plugs looked fine, but I took a couple of degrees of timing out and picked up .2 sec because the computer wasn't pulling timing anymore.

[Dave]

Awesome! Thanks man I'll give that a try and see what happens.

[BadAssPerformance]

I would say run the smaller fuel jet in nitrous kit.

It doesn't hurt to be a little fat, especially on pump gas. .

+1

or a larger N2O jet ;)


Also remember to take a degree or two out of your base timing when you anticipate running the spray. .

1° per 25hp

[zin]

Some very sound advice!!:thumb::thumb:

Mike

[Dave]

My Team Leader from our Technical support didnt recommend going away from the manufacturer's recommendations on jet sizes. He suggest installing an AFPR before the fuel solenoid to control flow that way.

Thoughts? I'm going to call Zex tomorrow and see what they say.

[BadAssPerformance]

He said that cuz the jets for an EFI kit are probably rated at ~43psi and with boost you're probably near 70psi? So yes, that is one way to do it.

Potential downsides:

smaller fuel jet - if you spray it without boost (70psi fuel preesuure or whatever its tuned at) it could be a tad lean?

regulator - regulator after 70psi to down to 43psi you may have bubbles?

[contraption22]

I think adding another fpr regulator for the nitrous system would cause uneeded clutter and complication. And in order to get it to work correctly you will also need two fuel pumps, two fuel feed lines, and two fuel return lines.

You still have to jet your nitrous kit taking base fuel pressure into consideration. Fuel pressure under boost is not an issue as far as mixture. The fuel pressure only rises with boost to keep the fuel pressure to manifold pressure differential consistent. It does not rise to richen the mixture under boost.

What I mean is if you have a stock 2.2/2.5 turbo with 55psi of base fuel pressure, at 10psi of boost, you will have 65psi of fuel pressure, but the differential of fuel pressure to manifold pressure is still 55psi. All of the enrichment under boost is handled by the computer fattening the pulswidth of the injectors.

The same will hold true for the nitrous system. You want to keep the fuel pressure to manifold pressure differential consistent.

Ideally, you would have the nitrous pressure also rise with manifold pressure to keep a conistent 950psi of nitrous pressure above manifold pressure, but in reality, 10-30psi of nitrous pressure loss won't cause THAT much of a rich condidtion....

...but 100-500psi of bottle pressure will....

....Which brings up another question. What was your nitrous bottle pressure when you made these test runs? If your bottle pressure is low (half filled bottle, cool day, with no bottle heater) that could richen the mixture quite a bit. You want to try to stay at 900-950psi bottle pressure. That will make it MUCH easier to get a really accurate tune.

Check out this link.
http://www.turbo-mopar.com/forums/showthread.php?t=42497

[Dave]

I think adding another fpr regulator for the nitrous system would cause uneeded clutter and complication. And in order to get it to work correctly you will also need two fuel pumps, two fuel feed lines, and two fuel return lines.

You still have to jet your nitrous kit taking base fuel pressure into consideration. Fuel pressure under boost is not an issue as far as mixture. The fuel pressure only rises with boost to keep the fuel pressure to manifold pressure differential consistent. It does not rise to richen the mixture under boost.

What I mean is if you have a stock 2.2/2.5 turbo with 55psi of base fuel pressure, at 10psi of boost, you will have 65psi of fuel pressure, but the differential of fuel pressure to manifold pressure is still 55psi. All of the enrichment under boost is handled by the computer fattening the pulswidth of the injectors.

The same will hold true for the nitrous system. You want to keep the fuel pressure to manifold pressure differential consistent.

Ideally, you would have the nitrous pressure also rise with manifold pressure to keep a conistent 950psi of nitrous pressure above manifold pressure, but in reality, 10-30psi of nitrous pressure loss won't cause THAT much of a rich condidtion....

...but 100-500psi of bottle pressure will....

....Which brings up another question. What was your nitrous bottle pressure when you made these test runs? If your bottle pressure is low (half filled bottle, cool day, with no bottle heater) that could richen the mixture quite a bit. You want to try to stay at 900-950psi bottle pressure. That will make it MUCH easier to get a really accurate tune.

Check out this link.
http://www.turbo-mopar.com/forums/showthread.php?t=42497

Really great advice! I don't know the bottle pressure. We just slapped the nitrous in in hopes to never use it unless we had to to make some extra power. Such as last weekend. ;)

Thanks again for all the help guys.

[zin]

Really great advice! I don't know the bottle pressure. We just slapped the nitrous in in hopes to never use it unless we had to to make some extra power. Such as last weekend. ;)

Thanks again for all the help guys.

Get a bottle pressure gage, they are pretty cheap and will go a LONG ways toward tuning/making power! If you find the pressure is low too often, then invest in a heater, but do get the pressure up where it should be before trying to tune out any "extra" fuel. If you gotta go the super cheap route, slap a stick-on aquarium thermometer onto the bottle and warm it to 85-90*, that will give you the 900-950PSI you want. It'll probably still be a little rich as the tune is for 40PSI, but it will get you a lot closer and making good power. After that, you can decide if you need to lean it out.

Mike

[puppet]

Dave ... how much of a shot are you introducing? If it's not too much ... less than 80HP you might just try a dry shot. (ducks head)
Our injectors should be able to keep up with this I'd think. You can't go nuts though. You have to keep it within reason.

[Dave]

Get a bottle pressure gage, they are pretty cheap and will go a LONG ways toward tuning/making power! If you find the pressure is low too often, then invest in a heater, but do get the pressure up where it should be before trying to tune out any "extra" fuel. If you gotta go the super cheap route, slap a stick-on aquarium thermometer onto the bottle and warm it to 85-90*, that will give you the 900-950PSI you want. It'll probably still be a little rich as the tune is for 40PSI, but it will get you a lot closer and making good power. After that, you can decide if you need to lean it out.

Mike

I'll grab one next year. I spent all my allowed discount this year at work. :thumb:


Dave ... how much of a shot are you introducing? If it's not too much ... less than 80HP you might just try a dry shot. (ducks head)
Our injectors should be able to keep up with this I'd think. You can't go nuts though. You have to keep it within reason.

Just a 55 shot for now. I don't want to risk going lean otherwise I would try that. I know it's all about the extra fuel anyway, so I would like to make it work that way. Next year I plan to run an even bigger shot. Not sure if Dad will go to a direct port setup instead like I would want to. It would sure be nice for even distribution though.

Either way, next year is sure gonna be fun. :love:

[contraption22]

Dave ... how much of a shot are you introducing? If it's not too much ... less than 80HP you might just try a dry shot. (ducks head)
Our injectors should be able to keep up with this I'd think. You can't go nuts though. You have to keep it within reason.

I STRONGLY recommend against a dry shot on a turbo engine.

If you were to put a zeiner diode, or cutout raiser on your car so the MAP sensor sees no more than 15psi of boost, then raise your boost to 25 without adding any fuel, it would be about the same as running an 80hp dry shot.

Small dry shorts work great on N/A motors, especially those with MAF sensors.

[Dave]

I STRONGLY recommend against a dry shot on a turbo engine.

If you were to put a zeiner diode, or cutout raiser on your car so the MAP sensor sees no more than 15psi of boost, then raise your boost to 25 without adding any fuel, it would be about the same as running an 80hp dry shot.

Small dry shorts work great on N/A motors, especially those with MAF sensors.

We are bleeding the MAP now. I think that's one of the biggest issues with how the van performed this season. It should have gone a lot faster.

[zin]

I STRONGLY recommend against a dry shot on a turbo engine.

If you were to put a zeiner diode, or cutout raiser on your car so the MAP sensor sees no more than 15psi of boost, then raise your boost to 25 without adding any fuel, it would be about the same as running an 80hp dry shot.

Small dry shorts work great on N/A motors, especially those with MAF sensors.

Just a quick note: A dry system is probably the best type of system you can run, BUT a "dry system" is NOT a "nitrous only" system, which is what I think you are referring to. In that case, I totally agree, a nitrous only system can be very dangerous as you are depending on there being "extra" fuel available to cover the shot of nitrous. It can be done and made to work very well (think Pro Stock ;)), but is far from a beginner's system.

A "dry" system is simply a nitrous system that injects nitrous only into the into the air intake piping, with the extra fuel coming from the injectors when the system is active. These systems generally work by either boosting the fuel pressure above normal (the most common), which can be difficult to properly pull off on a turbo engine as the boost pressure "eats up" most of the available "extra" pressure the fuel system can deliver.

The other way a dry system will get the fuel it needs is via the computer, either by tricking it, say by blowing super cold nitrous through/across the car's MAF (mass air flow sensor), or switching the coolant sensor's feed through a resistor to indicate -50*, both of which make the computer add the extra fuel, or by some other trigger that switches the map in the computer to one set-up for nitrous (extra fuel, less timing, RPM limits, etc).

With that established, the reason a "dry system" is generally better than a "wet system", is that the fuel will never make it through the intake system in an even manner and can result in lean backfires that can be both spectacular and destructive. Always fun to see (if it isn't your stuff).

The best way to go is almost always direct port, it gives the best tune-ability and distribution, but is also the most difficult to install and typically more expensive.

Sorry to write a book here, but a dry system is the most misunderstood, so I like to educate when I can.

Mike

[8valves]

Or have an AEM or equivelant EMS on the car that adds additional injector pulsewidth when the nitrous is triggered, and can be varied over boost and rpm just like a typical fuel map. Works like a charm!

[zin]

Or have an AEM or equivelant EMS on the car that adds additional injector pulsewidth when the nitrous is triggered, and can be varied over boost and rpm just like a typical fuel map. Works like a charm!

...or by some other trigger that switches the map in the computer to one set-up for nitrous (extra fuel, less timing, RPM limits, etc).

That's kinda what I meant by this part, but since many of us do their own cals I should have specifically mentioned stand-alones. There can be some trouble though as some have the capability, but don't "support" the feature as DFI (or whatever they are called today) patented ECU nitrous enrichment/control. I don't know if that is still an issue or if AEM licenced the rights... Whatever the deal is, it seems like the stand-alone would be the best way, if you can afford it.

Mike

[puppet]

Or have an AEM or equivelant EMS on the car that adds additional injector pulsewidth when the nitrous is triggered, and can be varied over boost and rpm just like a typical fuel map. Works like a charm!Like this or a tweak in the calibration.

[Ondonti]

Megasquirt does all that.


Ding ding ding mike! I don't think people who lack understanding of the purpose of a 1:1 base regulator should give advice on tuning nitrous (whatever dude was advising him).

[Ondonti]

Megasquirt does all that.


Ding ding ding mike! I don't think people who lack understanding of the purpose of a 1:1 base regulator should give advice on tuning nitrous (whatever dude was advising him).

[88_pacifica]

double post

[88_pacifica]

...or by some other trigger that switches the map in the computer to one set-up for nitrous (extra fuel, less timing, RPM limits, etc).

That's kinda what I meant by this part, but since many of us do their own cals I should have specifically mentioned stand-alones. There can be some trouble though as some have the capability, but don't "support" the feature as DFI (or whatever they are called today) patented ECU nitrous enrichment/control. I don't know if that is still an issue or if AEM licenced the rights... Whatever the deal is, it seems like the stand-alone would be the best way, if you can afford it.

Mike

Man, you'd think this Mike character works with nitrous applications every day or something.... :confused: :thumb:

[puppet]

Still wonder if our cals could be programed for this. It seems like it would just be a small bit of tweak in injector DC when nitrous is activated. The 55 jet would be divided up between (4) injectors. A little like the "switch" in the S60 cal for high boost? Has Rob(shelgame) been talked to about this?
Hardware? ... maybe a solenoid switching between a second FPR set for corrected fuel pressure?

At any rate .. this is a ton better than flowing fuel -(trying to)- in our manifolds.

Mike ... I wasn't suggesting Dave inject the nitrous and cross his fingers. You're right, that would suck.

[Dave]

Still wonder if our cals could be programed for this. It seems like it would just be a small bit of tweak in injector DC when nitrous is activated. The 55 jet would be divided up between (4) injectors. A little like the "switch" in the S60 cal for high boost? Has Rob(shelgame) been talked to about this?
Hardware? ... maybe a solenoid switching between a second FPR set for corrected fuel pressure?

At any rate .. this is a ton better than flowing fuel -(trying to)- in our manifolds.

Mike ... I wasn't suggesting Dave inject the nitrous and cross his fingers. You're right, that would suck.

From speaking withj Chris at TU his cals will have a function to cobtrol nitrous and alky among other awesome features.

[bradp]

Believe me Mike (Zin) has more credentials than ANYONE else here and maybe in the country when it comes to nitrous applications on vehicles. How many years now Mike have you been working with Mike Thermos?

[puppet]

From speaking withj Chris at TU his cals will have a function to cobtrol nitrous and alky among other awesome features.
That would be the way to go with a conservative shot. The way you have it running now tuning will be a real ----- ... with the tank below pressure it would be near impossible to get it right.

[zin]

Still wonder if our cals could be programed for this. It seems like it would just be a small bit of tweak in injector DC when nitrous is activated. The 55 jet would be divided up between (4) injectors. A little like the "switch" in the S60 cal for high boost? Has Rob(shelgame) been talked to about this?
Hardware? ... maybe a solenoid switching between a second FPR set for corrected fuel pressure?

At any rate .. this is a ton better than flowing fuel -(trying to)- in our manifolds.

Mike ... I wasn't suggesting Dave inject the nitrous and cross his fingers. You're right, that would suck.

Somewhere in a thread far far away, I laid out what features would be desirable in a custom cal, I agree that it seems easy enough to do, but since we are essentially hacking the code, it might not be as easy to get results as it may appear. I certainly am not the guy to make this happen! I can tell you what you want to have, but making it so... Well, that's out of my league!

Mike

[zin]

Believe me Mike (Zin) has more credentials than ANYONE else here and maybe in the country when it comes to nitrous applications on vehicles. How many years now Mike have you been working with Mike Thermos?

Started @ NOS in 94, then Holley/NOS, then Earl's, then Nitrous Supply... Damn it has been a while! :nod: Too bad the automotive aftermarket isn't a place to get rich... for that you have to get into construction, right?

Mike

[bradp]

Started @ NOS in 94, then Holley/NOS, then Earl's, then Nitrous Supply... Damn it has been a while! :nod: Too bad the automotive aftermarket isn't a place to get rich... for that you have to get into construction, right?

Mike

LOL:lol::lol:

[Ondonti]

If I felt like editing my pos TM server double post I would have it say "+1 mike marra"

[puppet]

If I felt like editing my pos TM server double post I would have it say "+1 mike marra"Don't be so hasty ... the injectors should be able to offset the 55shot. As far as cylinder pressure goes .. he'd have that issue regardless. If Chris and Co. can make this happen in code, that'll be outstanding.

[contraption22]

I think it would be a great idea on provided that you have the extra head room in injector pulswidth to make it work without sacrificing idle quality, and two, you don't mind burning a chip and/or calling up who ever burns your cals and have them mail one to you everytime you want to jet up or down.

For me, if I want to change from a 50 shot to a 75 shot or 100 shot, it costs me about $10 in jets and 5 minutes in time to do that, all myself, at the track. Between passes. Even in the staging lanes.

[puppet]

Good points ... guess we'll have to see how this is going to be implemented in code.

[8valves]

I think it would be a great idea on provided that you have the extra head room in injector pulswidth to make it work without sacrificing idle quality, and two, you don't mind burning a chip and/or calling up who ever burns your cals and have them mail one to you everytime you want to jet up or down.

For me, if I want to change from a 50 shot to a 75 shot or 100 shot, it costs me about $10 in jets and 5 minutes in time to do that, all myself, at the track. Between passes. Even in the staging lanes.

I guess we'll all know what Mike is up to under his hood in the lanes before the next round of quick class!! HAHAHA!

[contraption22]

I guess we'll all know what Mike is up to under his hood in the lanes before the next round of quick class!! HAHAHA!


Yeah I have some plans for next season. A better intake manifold setup for direct port nitrous is on the list, as well as possibly a stronger bottom end and maybe a bigger turbo.

[8valves]

All great except then you'll have 4 times the jets to change, so your time will have easily increased another 5 minutes of down time! :-P

[puppet]

Brings up another good point, on this topic ... maybe Mike(zin) can address.
Individual cylinder tuning. I seems to me that a common (manifold, pre-manifold .. whatever) injection point of nitrous is better in that it saturates the air with O2 prior to CAT sensor(s). This also leaves just a fueling issue to balance cylinder to cylinder.

Since wet injection systems use the nitrous to atomize the fuel upon injection they are/have been "married" to each other whenever/wherever placed in the tract. Now in Mike M's case, he'll be tuning each cylinder for balance. Can/would that tuning operation go much easier separating the two components?

[zin]

Brings up another good point, on this topic ... maybe Mike(zin) can address.
Individual cylinder tuning. I seems to me that a common (manifold, pre-manifold .. whatever) injection point of nitrous is better in that it saturates the air with O2 prior to CAT sensor(s). This also leaves just a fueling issue to balance cylinder to cylinder.

Since wet injection systems use the nitrous to atomize the fuel upon injection they are/have been "married" to each other whenever/wherever placed in the tract. Now in Mike M's case, he'll be tuning each cylinder for balance. Can/would that tuning operation go much easier separating the two components?

You've got some good points, but in the end, putting both the nitrous and fuel into the runner is your best bet. With this configuration, you are all but assured that they will go into the cylinder they are sprayed towards.

The CAT is so slow that it I often wonder if it serves a useful purpose! Also, air temp sensors tend to add timing when they are cold, so that isn't a "feature" we'd want to exploit, thankfully they ARE so slow as to not create issues with systems that do "hit" them.

Nitrous will flow through the intake in pretty much the same manner/flow path as air (it is only slightly heavier than air), but that also means that if there is a flow balance problem with the intake, it can be amplified when the nitrous is on.

So far as the nitrous and fuel being "married", that lasts about as long as things are moving in a straight line, once it has to turn, fuel tends to drop out or splatter against the outside curve of the runner or other part of the intake, the more severe the turn, the more "loss" of fuel will occur. Then you have liquid fuel running through the intake. While not generally harmful in itself, the liquid fuel doesn't burn properly, effectively making things leaner, even though the proper lb/hr of fuel was injected. Most of the time, these "wet" systems have enough extra fuel from the system and the engine's injection to cover a lean hole and prevent a backfire or other damage. But the bigger the hit the less coverage you have and the more likely you are to have a lean-out/backfire. This is also why I generally recommend switching to a direct port system around 75-100 HP, which is about the point where distribution of fuel can start to become a real problem. It is also the point at which the smallest fuel jets will not be too much fuel. At 40+ PSI, even a .014" jet flows a lot of fuel!

We did do some experimenting with injection of the fuel in the runner with the bulk of the nitrous in the plenum, which made good HP, but was difficult to tune and still required gaseous nitrous at the nozzle to atomize the fuel. Exactly why it made better HP was never proven, but is thought to be due to two things, cooler/denser charge in the plenum allowed "more stuff" to get through the intake, the other is that the streams of nitrous pointed down the runners accelerated/entrained air improving the volumetric efficiency... But, in the end, the complication and marginal improvement of the system caused it to be abandon.

Hope that helps more than confuses!

Mike

[8valves]

Very interesting indeed, thank you Mike.

I've often been curious on dual power adder setups if the mixed nitrous/fuel flow changes based upon pressure in the intake. My basis of this comes from a higher pressure differential throughout the system, as in differences between center plenum to inside of tight radius, etc.

I wonder if that could also play role in distribution of the mixture? I know Dart has a wet flow bench that is amazing to see function, and the distribution of the fuel flow changed based upon depression setting IIRC. Certainly a high PR engine might have a similar effect?

Just thinking out loud I suppose.

[zin]

Very interesting indeed, thank you Mike.

I've often been curious on dual power adder setups if the mixed nitrous/fuel flow changes based upon pressure in the intake. My basis of this comes from a higher pressure differential throughout the system, as in differences between center plenum to inside of tight radius, etc.

I wonder if that could also play role in distribution of the mixture? I know Dart has a wet flow bench that is amazing to see function, and the distribution of the fuel flow changed based upon depression setting IIRC. Certainly a high PR engine might have a similar effect?

Just thinking out loud I suppose.

Any time we have a pressure differential there will be potential for flow un-balance. The differential has to come from something, either a restriction, turbulence, etc. Any of those things could turn the air/mix in an unpredictable direction, resulting in uneven cylinder to cylinder distribution.

I don't know if the pressure level will have a major effect on how the system performs, the higher pressure should make the fuel less volatile reducing it's desire to atomize, but we also tend to have a good deal of heat in the charge air so that may be canceling out this effect, at least to some extent.

It is pretty cool to watch fuel "materialize" when vacuum goes away. One day I'll build my own "wet flow" bench just so I can play around with this kind of thing... Now, where did I leave my winning lotto numbers....:D

Mike

[Dave]

You've got some good points, but in the end, putting both the nitrous and fuel into the runner is your best bet. With this configuration, you are all but assured that they will go into the cylinder they are sprayed towards.

The CAT is so slow that it I often wonder if it serves a useful purpose! Also, air temp sensors tend to add timing when they are cold, so that isn't a "feature" we'd want to exploit, thankfully they ARE so slow as to not create issues with systems that do "hit" them.

Nitrous will flow through the intake in pretty much the same manner/flow path as air (it is only slightly heavier than air), but that also means that if there is a flow balance problem with the intake, it can be amplified when the nitrous is on.

So far as the nitrous and fuel being "married", that lasts about as long as things are moving in a straight line, once it has to turn, fuel tends to drop out or splatter against the outside curve of the runner or other part of the intake, the more severe the turn, the more "loss" of fuel will occur. Then you have liquid fuel running through the intake. While not generally harmful in itself, the liquid fuel doesn't burn properly, effectively making things leaner, even though the proper lb/hr of fuel was injected. Most of the time, these "wet" systems have enough extra fuel from the system and the engine's injection to cover a lean hole and prevent a backfire or other damage. But the bigger the hit the less coverage you have and the more likely you are to have a lean-out/backfire. This is also why I generally recommend switching to a direct port system around 75-100 HP, which is about the point where distribution of fuel can start to become a real problem. It is also the point at which the smallest fuel jets will not be too much fuel. At 40+ PSI, even a .014" jet flows a lot of fuel!

We did do some experimenting with injection of the fuel in the runner with the bulk of the nitrous in the plenum, which made good HP, but was difficult to tune and still required gaseous nitrous at the nozzle to atomize the fuel. Exactly why it made better HP was never proven, but is thought to be due to two things, cooler/denser charge in the plenum allowed "more stuff" to get through the intake, the other is that the streams of nitrous pointed down the runners accelerated/entrained air improving the volumetric efficiency... But, in the end, the complication and marginal improvement of the system caused it to be abandon.

Hope that helps more than confuses!

Mike

:eek:

Awesome knowledge here. I often wondered this myself... a lot of companies, I know, don't recommend a Wet shot if the fuel is going to be distributed through the intake manifold. I suppose my biggest comparisons are those of carb'd setups. IE a nitrous plate, or even the carb itself distributes fuel through the intake. Such as a dual plane might have would have more turns than anything other carb'd intake manifold.

Zin, any thoughts here?

Also, when going to a wet shot do you leave the jetting the same per nozzle? Say, right now we have a single fogger wet nozzle rated at a 55 HP shot. If we want to keep it a 55 shot but in a direct port 4 cylinder application, do we just simply divide the jetting in 1/4's? Or how does that work?

[zin]

:eek:

Awesome knowledge here. I often wondered this myself... a lot of companies, I know, don't recommend a Wet shot if the fuel is going to be distributed through the intake manifold. I suppose my biggest comparisons are those of carb'd setups. IE a nitrous plate, or even the carb itself distributes fuel through the intake. Such as a dual plane might have would have more turns than anything other carb'd intake manifold.

Zin, any thoughts here?

Also, when going to a wet shot do you leave the jetting the same per nozzle? Say, right now we have a single fogger wet nozzle rated at a 55 HP shot. If we want to keep it a 55 shot but in a direct port 4 cylinder application, do we just simply divide the jetting in 1/4's? Or how does that work?

The big difference between a carb'd intake and our EFI intakes is that the carb'd intake was designed from the start to flow fuel, and so they tend to have more gradual bends and transitions, in an effort to keep the fuel in suspension, but since an EFI intake is not expected to have fuel going through it, they tend to have much tighter, and complex runners. Since nitrous is very close to air as far as weight goes, it follows very closely, not so much for fuel. I like to use the school bus(fuel) vs. Ferrari(nitrous) analogy, in a straight line at 60mph, not much difference, they'll both stick with each other, but, that hairpin curve coming up? well, at 60MPH the Ferrari is going to make it, but that school bus? Well, lets just hope there weren't any kids on board! Now, design the track to accommodate the school bus and everyone is happy, but design it for the Ferrari and that bus is going to be balled-up in short order!

As for jetting a single to a multi-port system. You'll need to divide the flow AREA to the 4 (or however many) nozzles. There is a formula to do this:

Jet size X Jet size, then square rooted, and then divided by the number of nozzles to be used. As an example: split up an 82 jet to 8 nozzles. 28 x 28= 784, square rooted= 28 So, eight 28 jets will have the same flow area/hp as a single 82 jet.

OK, now for the cheat!:eyebrows: For 4 cylinders ONLY, just divide the single jet in half!

Mike

[Dave]

Thank you. Makes great sense. :)

[contraption22]

Mike (ZIN),

To bring back an old thread,

Is there any way to make a dry shot work without completely reengineering our fuel systems, short of a custom cal?

[zin]

Mike (ZIN),

To bring back an old thread,

Is there any way to make a dry shot work without completely re-engineering our fuel systems, short of a custom cal?

Sure, the trick is to keep the boost pressure consistent. In a non-cal application, you'll most commonly, need to boost the fuel pressure above "normal", this adds the extra fuel for the nitrous. The amount of HP/nitrous is limited by the amount of fuel you can get though boosting the pressure. 80-85PSI is pretty much the max you can go, though some have gone higher, I think it is a good compromise with safety and max HP.

You need to test to see what your maximum fuel pressure is when @ full boost, then we can see what kind of "overhead" we have for adding nitrous. I'd start small, something like a 28 jet.

This is small enough to potentially do something but small enough to ensure we can't hurt anything. At the same time, it gives us an idea as to how much fuel we have to work with.

The best way to tune is by spark-plug color/indications. But, that method of cutting the engine off clean, isn't too kind to turbos, so a wide-band O2 is the next best thing. 10.5-11:1 is typical for heavy nitrous/turbo applications, but I would expect this application would prefer something in the 11-12:1 range. And, I would still look at the plugs for any signs of detonation, which is more likely to hurt an engine than running lean...

Another way to get the needed fuel is to fool the computer into adding extra fuel by modifying the coolant temp sensor's signal into making the computer think it's -20* out.

The first way I mentioned is the easiest, as there is a kit made to do just this, the NOS 05115, made for 5.0L Fords, though it can be made to work on anything using a vacuum/boost referenced fuel pressure regulator.

The second method is how we did our Neon (05182nos) and the Viper kits (05180nos). They worked great, but are a little more involved, but not too much.

Interestingly, you could do both!! Of course, you'd need a top-notch fuel pump to do it!

If anyone would like to know more, feel free to PM me or we could start a new thread...

Mike

[puppet]

What about a 3 way solenoid valve plumbed into the fuel return line? One leg on the valve can be restricted with a jet ... raising the fuel pressure. Could be switched with the nitrous system. Boost requirements stay proportional.

[zin]

What about a 3 way solenoid valve plumbed into the fuel return line? One leg on the valve can be restricted with a jet ... raising the fuel pressure. Could be switched with the nitrous system. Boost requirements stay proportional.

That's pretty much what the normal system does, but the problem you would run into is that a simple restricter jet won't maintain a particular pressure. It will spike it, but as the injectors open more and more, you'd loose more and more pressure, at a point that you need it the most. Boosting fuel pressure via the fuel regulator involves pressurizing the regulator, just like boost does, but to a higher degree, and without the counterbalancing pressure of boost, resulting in a "step-up" type of pressure increase, one that stays constant regardless of the injector flow rate (assuming an adequate fuel pump/system).

Now, if you put a Grainger type check valve in the line as the restricter "jet", it would work in the same way as the commercial system, adjusting the amount of by-passed fuel to maintain whatever pressure it was set to. One difference would be that the pressure the regulator's diaphragm sees from the fuel pressure boost would not be "balanced" by pressure on the "air" side of the diaphragm, which might be detrimental to it's longevity... But it would work.

Mike

[contraption22]

Started a new thread here.

http://www.turbo-mopar.com/forums/showthread.php?p=651196#post651196

[Dave]

I'm going to start playing with this soon. Problem is I don't know how much smaller I really can go with a 55shot. Per Zex, the fuel jet is .17". They only go down to .15". Not much smaller. I may try another brand which allows a smaller fuel jet............................................... ........

OR...........................

Bigger nitrous jet! :evil: :nx:

Mike, any thoughts on a maximum safe amount with a wet shot through an EFI manifold? I'd imagine no fuel in the manifold is best but I'd like to hear your thoughts? I'm mostly concerned with even distribution once we get to a bigger shot.

And we're getting a computer flashed for it... I'm thinking retarding 2* of timing for our current 55 shot? Venolia pistons with a stock CC G-head... I forget the static compression of that setup though. :confused:

[Dave]

Shabump?

[zin]

I'm going to start playing with this soon. Problem is I don't know how much smaller I really can go with a 55shot. Per Zex, the fuel jet is .17". They only go down to .15". Not much smaller. I may try another brand which allows a smaller fuel jet............................................... ........

OR...........................

Bigger nitrous jet! :evil: :nx:

Mike, any thoughts on a maximum safe amount with a wet shot through an EFI manifold? I'd imagine no fuel in the manifold is best but I'd like to hear your thoughts? I'm mostly concerned with even distribution once we get to a bigger shot.

And we're getting a computer flashed for it... I'm thinking retarding 2* of timing for our current 55 shot? Venolia pistons with a stock CC G-head... I forget the static compression of that setup though. :confused:

Your pretty much on target with your assumptions, dry is better than wet. Incidentally, if you go dry, you'll want to inject the nitrous just after the intercooler, this gives the maximum time for the nitrous to cool and mix with the air ensuring as even a mixture as the intake manifold will allow.

As to max HP with a wet system... That's a bit of a loaded question!:o I've seen some folks get away with things that they really shouldn't have, but if I had to throw out a number, I'd say somewhere in the 100HP range, and no higher... Direct port will cure this problem as it is a question of distribution more than anything else, assuming the bottom end is built to handle the abuse. The number 1 issue with these systems (single point wet), is that the fuel won't get to all the runners evenly. At low HP levels, say 30-50HP, there is enough "extra" fuel from the injectors to "cover" a lean hole caused by the poor distribution. The problem is that as the system is jetted up and up, the amount of "cover" fuel stays the same, which inches that cylinder closer and closer to a backfire... So, that's why we will advise someone to either go direct port, or keep it smallish.

As you probably already know, a 50HP combo on a turbo car can easily pan out to be 75HP or so at the wheels due to the added intercooling and boost efficiency.

You are on the right track regarding adjusting the tune-up, and the timing seems fine too...

A little side note about ignition timing: All engines make best power when they develop peak cylinder pressure around 15-20* aTDC. This is true for just about every spark engine you'll deal with. We often run the total timing in the 35* (bTDC) range in order to achieve peak pressure in the 15-20* range. Nitrous is unique in that it chemically adds oxygen, more oxygen means you can burn more fuel, but since the ratio goes higher (N2O has approx. 14% more O2 than air), the burn rate also goes up. This faster burn means we need to light the mixture later to still achieve the peak pressure at 15-20* aTDC, to what degree depends on how much nitrous is added, and to a lesser degree, chamber design, etc.

We have found that retarding the timing 2* per 50HP of nitrous added, will pretty much guarantee that the timing won't be too much, in fact, it will likely be substantially less than it could be. Most will find best power with 1-1.5* retard from the engine's best "motor-only/non-nitrous" timing.

It is worth noting that the reason we start with more retard than needed is that it will result in only a loss in power and response due to the peak pressure happening latter, say 20-25*aTDC. Too much timing, just like with a turbo or supercharger (or NA for that matter!) will kill an engine faster than anything else you can do, short of a stick of dynamite or a .50BMG round!

Mike

[Dave]

Your pretty much on target with your assumptions, dry is better than wet. Incidentally, if you go dry, you'll want to inject the nitrous just after the intercooler, this gives the maximum time for the nitrous to cool and mix with the air ensuring as even a mixture as the intake manifold will allow.

As to max HP with a wet system... That's a bit of a loaded question!:o I've seen some folks get away with things that they really shouldn't have, but if I had to throw out a number, I'd say somewhere in the 100HP range, and no higher... Direct port will cure this problem as it is a question of distribution more than anything else, assuming the bottom end is built to handle the abuse. The number 1 issue with these systems (single point wet), is that the fuel won't get to all the runners evenly. At low HP levels, say 30-50HP, there is enough "extra" fuel from the injectors to "cover" a lean hole caused by the poor distribution. The problem is that as the system is jetted up and up, the amount of "cover" fuel stays the same, which inches that cylinder closer and closer to a backfire... So, that's why we will advise someone to either go direct port, or keep it smallish.

As you probably already know, a 50HP combo on a turbo car can easily pan out to be 75HP or so at the wheels due to the added intercooling and boost efficiency.

You are on the right track regarding adjusting the tune-up, and the timing seems fine too...

A little side note about ignition timing: All engines make best power when they develop peak cylinder pressure around 15-20* aTDC. This is true for just about every spark engine you'll deal with. We often run the total timing in the 35* (bTDC) range in order to achieve peak pressure in the 15-20* range. Nitrous is unique in that it chemically adds oxygen, more oxygen means you can burn more fuel, but since the ratio goes higher (N2O has approx. 14% more O2 than air), the burn rate also goes up. This faster burn means we need to light the mixture later to still achieve the peak pressure at 15-20* aTDC, to what degree depends on how much nitrous is added, and to a lesser degree, chamber design, etc.

We have found that retarding the timing 2* per 50HP of nitrous added, will pretty much guarantee that the timing won't be too much, in fact, it will likely be substantially less than it could be. Most will find best power with 1-1.5* retard from the engine's best "motor-only/non-nitrous" timing.

It is worth noting that the reason we start with more retard than needed is that it will result in only a loss in power and response due to the peak pressure happening latter, say 20-25*aTDC. Too much timing, just like with a turbo or supercharger (or NA for that matter!) will kill an engine faster than anything else you can do, short of a stick of dynamite or a .50BMG round!

Mike

Good stuff like always, Mike! :thumb:

Thanks again. Onwards we go with the bottle then!

[zin]

Good stuff like always, Mike! :thumb:

Thanks again. Onwards we go with the bottle then!

Thanks! Happy to help!

Mike