Intake/Exhaust Pressure Ratio's - what's the big deal?

[Shadow]

I'm still surprised that no one has really touched the subject on twin scroll stuff.

Twin scroll = Way more $'s and time to make it worth doing + a Vast amount of knowledge to do it Right. Most twin scroll set-ups will suffer and get destroyed on the top end by single scroll turbo set-ups. IF I thought it was worth it, I would have gone that route looking for the Best response on the street.

So for now, anything under 700WHP and there are single scroll turbos that work just fine.

[ShadowFromHell]

What kind of gauges/setups are you guys using to monitor drive pressure? Just a normal boost gauge? What about heat? Ive got a boost only 40psi gauge I bought for my diesel I never used. Would that work? What about the heat?

[acannell]

What kind of gauges/setups are you guys using to monitor drive pressure? Just a normal boost gauge? What about heat? Ive got a boost only 40psi gauge I bought for my diesel I never used. Would that work? What about the heat?

Im using a pressure sensor but a gauge should work just fine. To deal with heat you can connect the gauge/sensor via a section of copper tubing to the point on the exhaust you want to measure. The tubing acts as a heat sink. I used a pretty short section which might be a little too short. Perhaps a longer section would be more appropriate. You are measuring pretty slow pressure changes so it shouldnt matter.

I have mine measuring pressure right after the head port so it doesn't tell me how much the manifold, turbo, swingvalve, or exhuast pipe are individually contributing, but it does tell me what the "pressure ratio" is from boost to exhaust pressure. Not at the valve seat but at least as near as I can at the moment. Good enough to ballpark the situation I think.

http://www.turbododge.com/forums/f4/...ml#post3571297

[zin]

Put a loop in the copper/metal line going to the gauge, it helps to isolate the heat.

Mike

[Reaper1]

Twin scroll = Way more $'s and time to make it worth doing + a Vast amount of knowledge to do it Right. Most twin scroll set-ups will suffer and get destroyed on the top end by single scroll turbo set-ups. IF I thought it was worth it, I would have gone that route looking for the Best response on the street.

So for now, anything under 700WHP and there are single scroll turbos that work just fine.

I don't agree with this at all. Why is a twin scroll so much harder to do? If you are trying to keep the stock type exhaust manifold, then yeah, I agree. But, if you are going to go to a twin scroll then chances are you are also going to make a custom header. To make one for a twin scroll versus a single scroll only takes planning and not converging all of the tubes into one outlet like a typical header collector.

There are different ways to set-up the wastegates on twin scroll turbos. Maybe that's where you are thinking this gets complicated/expensive versus a single scroll. Having said that, the wastegate set-up doesn't have to be any more complicated than a single scroll. The most obvious way to do it is use 2 external wastegates. Yes, this is complicated, expensive, heavy, bulky and arguably not needed. This sort of set-up will be found mostly on money-is-no-object, b@lls-out, probably sponsored, full tilt race car. Think over 1000whp as a base for something like this. A twin scroll can absolutely be set-up with a single wastegate just like a single scroll. This is not only acceptable, but is done quite a bit for all of the reasons I just listed. Lastly there is the internal wastegate option, however very few twin scroll turbos have an internal gate, and only the BW EFR seems to be the only twin scroll performance option that I can remember off the top of my head.

Twin scroll turbine sections have the potential to outperform a similar single scroll turbine. However, there are still trade-offs and there isn't a direct correlation between what size twin scroll will give the best performance over a single scroll (meaning a decrease in spool time and keeping the same top end). From what I've read the "rule of thumb" is that you can typically run 1 size larger AR twin scroll than the single scroll size you would typically run. To put that in TM terms: if you are running a single scroll .63, you could run a .84 twin scroll (in theory) and get better spool while keeping the top end. Obviously in practice this will be different, but most of the reviews I've seen of people that have switched to a twin scroll have nothing but good things to say.

Please keep in mind that running a twin scroll turbine on an exhaust header/manifold designed for a single scroll will not net a performance gain (be very general here). You HAVE to run a manifold/header designed for a twin scroll turbine.

[85boostbox]

When I get home I will type on an actual computer. But Chris I agree with what you said.

[Shadow]

I don't agree with this at all. Why is a twin scroll so much harder to do?

if you are going to go to a twin scroll then chances are you are also going to make a custom header.

The most obvious way to do it is use 2 external wastegates. Yes, this is complicated, expensive, heavy, bulky and arguably not needed. This sort of set-up will be found mostly on money-is-no-object, b@lls-out, probably sponsored, full tilt race car.

A twin scroll can absolutely be set-up with a single wastegate just like a single scroll. This is not only acceptable, but is done quite a bit for all of the reasons I just listed. Lastly there is the internal wastegate option, however very few twin scroll turbos have an internal gate, and only the BW EFR seems to be the only twin scroll performance option that I can remember off the top of my head.

However, there are still trade-offs and there isn't a direct correlation between what size twin scroll will give the best performance over a single scroll (meaning a decrease in spool time and keeping the same top end.

Please keep in mind that running a twin scroll turbine on an exhaust header/manifold designed for a single scroll will not net a performance gain (be very general here). You HAVE to run a manifold/header designed for a twin scroll turbine.

You've already answered your own Q bro

My HE351 internally gated turbo and stock exhaust mani vs anything you build twin scroll. You will spend at least 4x as much $'s, 4x as much time installing and 4x as much time getting all to work properly IF you chose everything right in the first place.

So like everything else, I'm Not saying it can't be done And work well. Just not worth the time and effort to Me, when I can build something so simple that Works at least 90% as good as the Best you could ever hope for out of a twin scroll set-up.

[Reaper1]

I agree that this (sticking with a single scroll and stock exhaust manifold) seems to work for you. You have the skills it seems to eek out every last drop of potential out of the stock exhaust manifold. Very few can do that and even by your own admission it isn't the easiest or best way to accomplish making power. Remember, the discussion is about why the intake/exhaust pressure ratio is such a big deal and it has morphed into how to mitigate the compromises to accomplish a more efficient pressure ratio.

More and more people are building or are having custom headers built nowadays in our community, so I believe that taking a look at the twin scroll option is not only valid, but more pertinent than it ever has been for us. On top of that it gives a whole new slew of options for turbine housings and just might help fill in some gaps in compromises, namely spool time versus top end flow. Does it make sense for everyone? No. Do I think that a twin scroll set-up would make a huge performance difference with the Charger? No. However, dismissing it totally as an option because single scrolls work is kind of limiting.

As far as a single scroll working 90% as well as a twin scroll....I buy that...but that last 10% might just be what puts me that car length ahead or lets me get on power that much sooner out of a corner. Do I honestly believe I'm on that level? LMAO...HELL NO (helps to have a running car to be on any kind of competing level)! However, it is a valid point, regardless of how far fetched.

[acannell]

You have the skills it seems to eek out every last drop of potential out of the stock exhaust manifold.

Where things get interesting is what exactly was done to do that. I would think the following components would be the most relevant:

-head
-intake
-swingvalve
-turbo
-camshaft

And in Shadows, case, from what I gather:

-head = G head with very light port work and +1mm valves
-intake = Heavily modified intake, but essentially just BIG
-swingvalve = Custom swingvalve modified to be BIG
-turbo = holset, not sure if the wheels in it are special or not
-camshaft = off-the-shelf F4

These would seem to be fairly straightforward modifications. I'm not saying Shadow does not have extra-ordinary skill, on the contrary, I would say his Charger is a prime example of resourcefulness and efficiency of $$$ and effort. He is very frequently describing his strategies as being the least effort requiring and the least $$$ requiring. So I dont see how whatever it is he did to use the stock manifold is somehow beyond the scope of what others could duplicate, besides the fact that people seem to ignore what hes telling them lol

More and more, Shadows build is seeming to me to be more and more pragmatic and doing away with unnecessary fantasies that so many people seem to think are absolutely required. From that perspective I think we should be looking at his Charger as a model for how to build a very fast race car with the absolute minimum wasted skill and effort. The skill in this case is knowing where to put the scalpel and cut away the fat.

[GLHS60]

Well said!!

Thanks
Randy

Where things get interesting is what exactly was done to do that. I would think the following components would be the most relevant:

-head
-intake
-swingvalve
-turbo
-camshaft

And in Shadows, case, from what I gather:

-head = G head with very light port work and +1mm valves
-intake = Heavily modified intake, but essentially just BIG
-swingvalve = Custom swingvalve modified to be BIG
-turbo = holset, not sure if the wheels in it are special or not
-camshaft = off-the-shelf F4

These would seem to be fairly straightforward modifications. I'm not saying Shadow does not have extra-ordinary skill, on the contrary, I would say his Charger is a prime example of resourcefulness and efficiency of $$$ and effort. He is very frequently describing his strategies as being the least effort requiring and the least $$$ requiring. So I dont see how whatever it is he did to use the stock manifold is somehow beyond the scope of what others could duplicate, besides the fact that people seem to ignore what hes telling them lol

More and more, Shadows build is seeming to me to be more and more pragmatic and doing away with unnecessary fantasies that so many people seem to think are absolutely required. From that perspective I think we should be looking at his Charger as a model for how to build a very fast race car with the absolute minimum wasted skill and effort. The skill in this case is knowing where to put the scalpel and cut away the fat.

[Reaper1]

What you don't see or know about Shadow's set-up is exactly what is done. You could throw that same combination together and only make 300hp. The combination is VERY important, but just as important are all the details into that combination. I could be wrong, but for some reason I remember there being several iterations of his exhaust manifold. Now, does it work well because it is hogged out, or because of some little tricks done to the runner entrances and the collector area? How balanced are the cylinders (meaning that clearly they are all running well enough, but how far from optimal are they running as a result of using the stock manifold)?

Head porting...we all know there's more to this than just making the holes bigger. What work was really done? What about the chambers?

The intake, turbo, and such are all well documented.

Now, the real difference....the actual tune in the computer. Simply saying it's "x-stage" or it was done by "x-person" means squat. Every car and every combo has different needs. Again, you could build the spitting twin to Rob's car and it STILL will require some slight tweaks that are different from his car and they STILL won't perform exactly the same.

Rob has been refining his car, his tune, and his set-up for a long time. I'm not calling Rob out or bashing him at all. I am not saying that his set-up isn't a good template to follow. However, a person needs to understand WHY his set-up is the way it is; he has the goal of going the fastest he can on as many stock or modified stock parts as possible....only changing parts out as needed for reliability, wear, drivability, or weight. It really is the epitome of doing the most with the stock parts in our community (that I know of). However, that doesn't mean that there isn't easier or better (not necessarily cheaper) ways to accomplish the same thing. Just because something uses the stock parts and is cheap doesn't mean it was easy. There's a reason there isn't a ton of 500hp TM's running stock exhaust manifolds.

[acannell]

What you don't see or know about Shadow's set-up is exactly what is done. You could throw that same combination together and only make 300hp. The combination is VERY important, but just as important are all the details into that combination. I could be wrong, but for some reason I remember there being several iterations of his exhaust manifold. Now, does it work well because it is hogged out, or because of some little tricks done to the runner entrances and the collector area? How balanced are the cylinders (meaning that clearly they are all running well enough, but how far from optimal are they running as a result of using the stock manifold)?

Head porting...we all know there's more to this than just making the holes bigger. What work was really done? What about the chambers?

The intake, turbo, and such are all well documented.

Now, the real difference....the actual tune in the computer. Simply saying it's "x-stage" or it was done by "x-person" means squat. Every car and every combo has different needs. Again, you could build the spitting twin to Rob's car and it STILL will require some slight tweaks that are different from his car and they STILL won't perform exactly the same.

Rob has been refining his car, his tune, and his set-up for a long time. I'm not calling Rob out or bashing him at all. I am not saying that his set-up isn't a good template to follow. However, a person needs to understand WHY his set-up is the way it is; he has the goal of going the fastest he can on as many stock or modified stock parts as possible....only changing parts out as needed for reliability, wear, drivability, or weight. It really is the epitome of doing the most with the stock parts in our community (that I know of). However, that doesn't mean that there isn't easier or better (not necessarily cheaper) ways to accomplish the same thing. Just because something uses the stock parts and is cheap doesn't mean it was easy. There's a reason there isn't a ton of 500hp TM's running stock exhaust manifolds.

Its not clear to me what your conclusion is. That someone planning a 500hp build should add the expense, complexity, and reduced reliability of a tubular manifold when theres proof that isnt required? How does that make sense? How is that easier? You dont suddenly reduce the requirement to tune or tweak because you bolt on a tubular header, if anything you need to have an even firmer grip on whats going on and be prepared to do even more trial and error testing to get it to work right. Or at least, the argument could equally be made in that respect until proven otherwise.

In other words all the stuff Rob may or may not have done to the Charger comes with the territory at that power level, I dont think there is enough data to attach it specifically to using a stock exhaust manifold.

[Shadow]

FTR, the Holset turbo is an HE351 with both stock compressor and turbine wheels, albeit the turbine wheel has been clipped. (I believe it was 7 deg but would need to double check)

[OmniLuvr]

Its not clear to me what your conclusion is

basically, shadows setup WORKS! but at what cost? higher octane fuel, and a skilled enough tuner to make sure things don't go real bad once your above 3 bar! the second is a biggie!

im basically copying his setup, but hopefully will be able to make some sort of log/? header to move the turbo towards the drivers side a little more.

but since robs "intake" is custom, many might not have the same result, or because rob ported his own head (I think) then people again may not have the same result. same also goes for the stock ported log header...

the reason robs setup works so good is because it is "matched", the parts he chose, and chose to do the way he did work well with eachother.

1. holset turbo- they work very well at high pressure ratings, also flow well, has a 4" dump swingvalve, and a small enough turbine/housing that it also spools well.

2. lightly ported head AND combustion chamber(that part is important I believe)- the head will flow better than stock, easier to match ports, don't have to worry bout going into coolant chambers or destroying a $1250 dollar head if something catastrophic fails, and the fact that he has very little removed from the combustion chamber leaves more of a squish/quench area to help prevent detonation

3. modified intake- seriously, its not that crazy actually, he raised the roof, put his own elbow on it, did some port work and made the runners slightly shorter. he could have actually done much more to it, but then it might out flow his head... might...

4. ported exhaust- well, this thing just works, ported big enough the match the flow of the other parts, keeps pressure up to help with spool, but obviously flows enough to make 500 hp.

the big deal is to see what happens when he changes something in his setup next, your intake manifold may change everything? it could make more power at less intake psi, but the drive pressure may remain the same. so he "could" make 5xx hp at 30 psi but still be at his 38 psi drive pressure? then would a header benefit? im sure, and he has already stated that it will help now. id say the time for a header is when you have access to one or can afford it, plain and simple...

[Force Fed Mopar]

I thought he had a well ported head with larger than +1 valves? It is a bathtub head right?

[OmniLuvr]

I thought he had a well ported head with larger than +1 valves? It is a bathtub head right?

pretty sure only +1 valves, yes g-head with a small amount of deshrouding, and the head is ported "well" ( ), but i wouldnt say it was hogged out massive ports, basically what i would call "stage 3"?

[Shadow]

pretty sure only +1 valves, yes g-head with a small amount of deshrouding, and the head is ported "well" ( ), but i wouldnt say it was hogged out massive ports, basically what i would call "stage 3"?

Couldn't have categorized it better myself!

[Reaper1]

Its not clear to me what your conclusion is. That someone planning a 500hp build should add the expense, complexity, and reduced reliability of a tubular manifold when theres proof that isnt required? How does that make sense? How is that easier? You dont suddenly reduce the requirement to tune or tweak because you bolt on a tubular header, if anything you need to have an even firmer grip on whats going on and be prepared to do even more trial and error testing to get it to work right. Or at least, the argument could equally be made in that respect until proven otherwise.

In other words all the stuff Rob may or may not have done to the Charger comes with the territory at that power level, I dont think there is enough data to attach it specifically to using a stock exhaust manifold.

the time for a header is when you have access to one or can afford it, plain and simple...

^This!

[acannell]

the time for a header is when you have access to one or can afford it, plain and simple... ^This!

^This!

But does that strategy realistically help anyone? You could say that about pretty much any upgrade. When people are planning builds there are constraints of time and money and decisions have to be made. I guess what Im looking for is the justification to spend the time/money on a tubular header when you could be spending it on many other more critical things, for an engine build in the 500hp region. Its a chunk of change and is not without its risks and additional work.

If tubular headers were $150 there wouldnt really be a discussion. But they are more like twice that at least arent they? I think onerippinturbo2 is making some nice looking ones in that price range IIRC. I suppose the price for an entry-level tubular header that qualifies as significantly above-and-beyond a ported stocker would be a good number to know in this discussion.

Im not saying people cant come up with any reason to justify anything they want to do with their cars, and my hat is off to them. Its all for fun anyways. But I would like to see the price-of-entry for 500hp get forced down and down and down as much as possible for our cars. And it seems like Shadow has provided us with a great example in that specific regard, by eliminating the cost of a tubular header.

In the same way that, thankfully, the following things are apparently not needed for 500hp: billet connecting rods, $1500 cnc ported heads, 9,000rpm, 60psi, 0.6" lift etc...the more things we can get on the list of "not needed" for a power level that is "very high" the better IMO. I think its reasonable to say a majority of TD/TM'rs will have more fun if that bar gets lower and lower and lower.

[Shadow]

A Proper tubular header would be more in the 800.00-1500.00 range, depending on turbo location