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Force Fed Mopar
02-27-2015, 01:12 AM
How much better is 2-bar for drivability? And how far can you push it boost-wise? I know I have run 16psi on stock injectors and a 2-bar before on a MP StageII GLHS cal with no fueling problems. I'm assuming 18psi would probably be pushing it too lean for comfort?

Is a 2.5-bar a good compromise between the two? I've been debating putting the Lebaron back to stock 2-bar and injectors since after 18psi on a stock head you get into the realm of diminishing returns. 5DIGITS and some other have been convincing me to go down on boost and up on timing as long as I insist on running a stock swirl head and T2 Garrett on pump gas (93 Octane). I plan on doing the #4 cooling mod also to even out timing and knock sensitivity.

I'll probably do a E85 or race gas tune though also, which will allow me to run the higher boost levels without knocking. In which case I can still take advantage of the 3-bar. But, I dont know if it'll gain enough even then to be worth it. So I'm thinking the 2.5-bar would be a good compromise. Thoughts?

bamman
02-27-2015, 01:50 AM
Simply put, if you want to go over 15 psi of boost, you need a three bar sensor and a custom tune for it.

Drivability can be the same. What you will run into is how to fuel the motor without detonating.

At a minimum you'd need:
A three bar map sensor.
+20 injectors
A custom tune scaled for the three bar map, injectors, and higher boost.

Keito
02-27-2015, 06:17 AM
[QUOTE=
I'll probably do a E85 or race gas tune though also, which will allow me to run the higher boost levels without knocking. In which case I can still take advantage of the 3-bar. But, I dont know if it'll gain enough even then to be worth it. So I'm thinking the 2.5-bar would be a good compromise. Thoughts?[/QUOTE]

Technically wouldn't the benefit of E85 be to allow you to run more timing, not more boost.(Since it's 105ish octane)

tryingbe
02-27-2015, 09:02 AM
2 bar map sensor see ~14.7 psi MAXIMUM. If your engine run 30psi, guess what the sensor see? 14.7psi. No way the computer will put more fuel and pull timing for anything above 14.7psi.

Tape of map sensor has NOTHING to do with drive-ability, tune does. I've been using 3 bar map for years and AJ been using 4 bar map sensor. Use whatever map sensor to match whatever amount of the boost you want to run.

shadow88
02-27-2015, 09:42 AM
2 bar map sensor see ~14.7 psi MAXIMUM. If your engine run 30psi, guess what the sensor see? 14.7psi. No way the computer will put more fuel and pull timing for anything above 14.7psi.

Tape of map sensor has NOTHING to do with drive-ability, tune does. I've been using 3 bar map for years and AJ been using 4 bar map sensor. Use whatever map sensor to match whatever amount of the boost you want to run.

This is totally correct. However my personal findings with 3 bar tunes make me want a factory 2 bar and add the fuel myself. The only way I would want a 3 bar is to do it myself, which I don't want to put the time into.

tryingbe
02-27-2015, 10:01 AM
I used a TU Cal once, waited forever for it and engine didn't even last at 12psi.

After that I always tune myself, fastest turn around and safest method I know of.


http://www.thelostartof.net/tryingbe/dodge/omniproject/tune/partthrottle.JPG

ShelGame
02-27-2015, 10:44 AM
2 bar map sensor see ~14.7 psi MAXIMUM. If your engine run 30psi, guess what the sensor see? 14.7psi. No way the computer will put more fuel and pull timing for anything above 14.7psi.

Tape of map sensor has NOTHING to do with drive-ability, tune does. I've been using 3 bar map for years and AJ been using 4 bar map sensor. Use whatever map sensor to match whatever amount of the boost you want to run.

Actually, the sensor won't even see 14.7. The stock 2-bar sensor goes out of range at about 14.5psi.

- - - Updated - - -


I used a TU Cal once, waited forever for it and engine didn't even last at 12psi.

After that I always tune myself, fastest turn around and safest method I know of.


http://www.thelostartof.net/tryingbe/dodge/omniproject/tune/partthrottle.JPG

STILL using MP Tune 1?

- - - Updated - - -


This is totally correct. However my personal findings with 3 bar tunes make me want a factory 2 bar and add the fuel myself. The only way I would want a 3 bar is to do it myself, which I don't want to put the time into.

Personal findings from when? Recently?

It's not that hard to setup a 3-bar cal these days. Check the 'Class' threads in the EFI sections...

- - - Updated - - -

All of the above considered, a 2.5 BAR MAP is a good compromise if you only want to run ~18psi boost.

Force Fed Mopar
02-27-2015, 11:00 AM
I do all my own tuning, and am well aware that the 2-bar doesn't read over 14.7 psi. I'm just looking at things that might increase the drivability and mpg. Not that I have any real problem with it now, but it is a daily so any increase is good.

Basically once you get past 18 psi, you start getting diminishing returns from the boost due to timing retard. And the factory timing slope is pretty close to the max for 93 octane. You can go up a little higher below 10, but at 15 psi 2-3 degrees over stock brings audible knock. There is still a good increase in power from 15 to 18 psi though. Increasing to 21 or so still increases power but not as much. Which is why I was considering a 2.5-bar map, to gain some resolution and still be able to tune properly up to 20psi.

shadow88
02-27-2015, 11:01 AM
Personal findings from about 4 years ago. As far as setting up my own 3 bar, like I said, I don't want to put the time into.

Force Fed Mopar
02-27-2015, 11:06 AM
Personal findings from about 4 years ago. As far as setting up my own 3 bar, like I said, I don't want to put the time into.

If you have a stock head, you can pretty much scale for injectors (if +40's then scale for 58lb), 3-bar and set timing tables to match the MP cal and you are good to go.

bamman
02-27-2015, 11:18 AM
One of the reasons the timing is retarded by the computer is because of knock. You must address this issue before you can make more power. One way to address this issue is to increase fueling. Another is to cool the air coming into the engine with an intercooler, or a better intercooler.

As far as resolution of the map sensor, I think I understand what you are saying. Something along the lines of say a hypothetical 100 bar map sensor reading 4.1 volts which equates to 15psi when 4.2 volts which equates to 39.3 psi versus a 2.5 bar sensor reading 4.1 volts which equates to 15 psi versus 4.2 volts equating to 15.2 psi?

If you are worried about the computer not having an accurate grasp of what the boost is with a higher scale map sensor, in this case a 3 bar sensor, don't worry. Drivability will not be a concern. Just go with a three bar sensor and you will be good. The cost of a good quality three bar sensor is cheaper than trying to find or custom make a 2.5 bar sensor (last I checked that is.)

ShelGame
02-27-2015, 12:39 PM
As far as resolution of the map sensor, I think I understand what you are saying. Something along the lines of say a hypothetical 100 bar map sensor reading 4.1 volts which equates to 15psi when 4.2 volts which equates to 39.3 psi versus a 2.5 bar sensor reading 4.1 volts which equates to 15 psi versus 4.2 volts equating to 15.2 psi?


The resolution issue is related to the limitations of an 8-bit computer. The MAP signal is digitized into 8-bits. That gives 256 'steps' for each 5v signal. So, if you have a 2-bar MAP, that is 29.4psi (total) divided into 256 steps, gives 0.115psi per step. This is the smallest increment of MAP change the computer can 'see'.

With a 3-bar MAP, that smallest step is larger. 44.1psi / 256 = 0.172psi per step. The concern is really in vacuum, not boost. This change in step size (or resolution), means that small vacuum changes can be missed resulting in fueling errors and drive-ability problems. Which can be made worse by 'big' cams and porting work. That can usually be 'fixed' by small adjustments in the O2 feedback values.

EDIT: Copied this post to the Turbonator Tuning Wiki

ShelGame
02-27-2015, 12:45 PM
Personal findings from about 4 years ago. As far as setting up my own 3 bar, like I said, I don't want to put the time into.

I like to think we've come quite a ways in 4-5 years. At least in the DIY side.

going4speed
02-27-2015, 01:54 PM
Omnipower map sensor is giving me good results.

OmniLuvr
02-27-2015, 08:06 PM
Technically wouldn't the benefit of E85 be to allow you to run more timing, not more boost.(Since it's 105ish octane)

that's what the octane rating is in a "test" engine, actual results vary, locations also vary. also, because of the extra volume of fuel, there is additional cooling occurring giving more knock resistance. so you can run more timing AND more boost AND more compression!!! I did all 3...

going4speed
02-27-2015, 08:47 PM
Running a boost button 3 bar +20 inj stage 3 on the lancer and it runs like a top

So much so that I trust it as the wife's daily :thumb:

bamman
02-27-2015, 11:13 PM
The resolution issue is related to the limitations of an 8-bit computer. The MAP signal is digitized into 8-bits. That gives 256 'steps' for each 5v signal. So, if you have a 2-bar MAP, that is 29.4psi (total) divided into 256 steps, gives 0.115psi per step. This is the smallest increment of MAP change the computer can 'see'.

With a 3-bar MAP, that smallest step is larger. 44.1psi / 256 = 0.172psi per step. The concern is really in vacuum, not boost. This change in step size (or resolution), means that small vacuum changes can be missed resulting in fueling errors and drive-ability problems. Which can be made worse by 'big' cams and porting work. That can usually be 'fixed' by small adjustments in the O2 feedback values.

EDIT: Copied this post to the Turbonator Tuning Wiki

That is a great way to explain it. Have people actually reported many driveability problems though? I hear a lot of success stories with a three bar map and still having 30+ MPG that I didn't know this was an issue. It does put into perspective as to why a 2.5 bar map sensor would be beneficial.

ShelGame
02-27-2015, 11:23 PM
That is a great way to explain it. Have people actually reported many driveability problems though? I hear a lot of success stories with a three bar map and still having 30+ MPG that I didn't know this was an issue. It does put into perspective as to why a 2.5 bar map sensor would be beneficial.

I'm not sure if it's been confirmed to be a problem or not. There are a lot of cars running 3-bar MAPs with NO driveability problems (hell, there are cars running 4-bar MAP's on the street with no problems). Then, there are some that do.

I think it's important to note that there ARE bad 3-bar MAPs out there. If you got yours for $20 off eBay, and it runs like crap, just be aware that it could be the MAP sensor. I have one of these and plan to document the issues with it. It actually can be compensated for with the cal. But, it's probably not for everyone.

I'd really like to get into making my own 2.3, 3, and 4-bar MAP's. Just too many other irons in the fire right now.

Force Fed Mopar
02-28-2015, 03:09 AM
One of the reasons the timing is retarded by the computer is because of knock. You must address this issue before you can make more power. One way to address this issue is to increase fueling. Another is to cool the air coming into the engine with an intercooler, or a better intercooler.

I realize this. My AFR's are 11-11.5, I have a water-to-air intercooler. I've fairly successfully tuned the car on the 3-bar setup for the last 3 years. It runs reliably as my daily driver, runs 9.24@80mph in the 8th, and gets 30+ mpg if I keep my foot out of it.

I'm not saying the car has any real drivability problems as it is. What I'm wanting to do now is basically micro-tune it, for lack of a better term. I'm planning on refreshing the engine soon, and when I do I will be doing the #4 cooling mod, as it has been proven to equalize cooling and knock sensitivity across the cyl's. Then wire the wideband output through the factory computer, so I can log it in MPScan and the computer can calculate the narrowband from it. Also plan on adding a wideband knock sensor and a pressure port in the exhaust manifold.

There may not be any real noticeable gains from the lower map sensors, but you never know til you try. I have seen some of the older Mopar techs mention that they preferred 2-bars for their street manners.

shadow88
02-28-2015, 06:16 AM
I like to think we've come quite a ways in 4-5 years. At least in the DIY side.

I hope things have come a long way in that time, because the first controller didn't start the car and the second had so much ignition advance it broke the insulation off the spark plugs and damaged the pistons, head and turbine wheel. I figured after that, a third effort wasn't going to be awarded to the programmer.

ShelGame
02-28-2015, 08:33 AM
I hope things have come a long way in that time, because the first controller didn't start the car and the second had so much ignition advance it broke the insulation off the spark plugs and damaged the pistons, head and turbine wheel. I figured after that, a third effort wasn't going to be awarded to the programmer.

Gack. Was that me?

tryingbe
02-28-2015, 08:45 AM
STILL using MP Tune 1?



I am using MP tune 2, but I don't feel like updating all screen shots.

ShelGame
02-28-2015, 10:37 AM
I am using MP tune 2, but I don't feel like updating all screen shots.

Lol, gotcha...

shadow88
03-01-2015, 01:45 AM
Gack. Was that me?

I spent many many hours tuning the mega squirt system on my old turbo neon. Also many runs made with the factory 2 bar in my shadow with "caveman" cold start injectors to get the perfect a/f ratio and ignition advance. So I know how difficult it is to get a tune correct. To get it right the first time is unlikely, and the second time is almost as unlikely, but at the cost to repair the damage, I had to go back to my tried and true caveman ways.

Yeah, that damage came from your smec.

mopar-tech
03-01-2015, 08:04 AM
Also many runs made with the factory 2 bar in my shadow with "caveman" cold start injectors to get the perfect a/f ratio and ignition advance.

I debated wading into this thread the few times it popped up and thought I'd chime in finally.

When Gus introduced me to the cold start injector method I thought it was impossible and crazy but after using it for some time and running my own car on the dyno several times I'm convinced it is a viable alternative. You think this is caveman? Gus's turbo Mustang had a kit from Art Carr on it and the fuel enrichment was adjusted by turning a brass valve in a fuel line that was plumbed into the carb hat. That's just the way it was from Art Carr and the damn car ran like a scalded dog.

My advice for anyone looking to run a cold start is to get a cal with the overboost shut down so they don't have to fool with diodes, get a good cold start valve with a quality switch (I had a light on the dash to verify operation too) and limit the boost to 20-25 psi if running a stock turbo and intercooler. They car will be pretty safe with pump gas and a riot to drive. I ran 12's with what I mentioned above (I used a diode instead AND 30 psi) and it was perfectly safe.

More than one way to skin a cat.