General Stock 2G ECU Capabilities

[jpfrk2001]

Question about the stock ECU capabilities?
Will the factory ECU read and accept a 3 BAR MAP?

1997 GSX stock.

The way it works, the 3 BAR just widens and expands the voltage out put based on pressure input.

Basically a 2 Bar goes from -14.7 to 14.7 lbs of boost. So the voltage output would be 0.1V to 5.0V across the range.

A 3 Bar just widens that range.

Of course I will be going 440 CC injectors and a larger 3" turbo back exhaust.

When I swapped to a 12.5 lb spring, The ECU gave no hiccups about it.

I want to achieve a 320ish hp at the crank on stock block/turbo. I will have a wideband and boost guage to keep check on things of course.

I already have a K&N cold air, 12.5 lb spring WG actuator. I want to go 16lbs boost, larger 3" exhaust turbo back, 3 BAR MAP on Stock ECU

15 years ago I did something similar on a Chrysler ECU factory NA. I just swapped to a 2 BAR MAP, 3" exhaust, larger fuel injectors, 8 LBS of boost with a turbo. this was a OBDI system. It took it fine.

 

[pauleyman]

Well for starters you already have 450cc injectors.

 

[jpfrk2001]

Well for starters you already have 450cc injectors.

OK,

So what about the stock ECU with a 3 BAR?

450 CC is good for 300 at the crank based on the Math

I would hate to spend the money, swap the MAP, start up the motor and see the ECU start freaking out.

I guess I could just try it. Don't do any boost increase. Just do an experiment and see what happens.

I would guess that the engine would immediately lean out(but going to say 600CC should control that). Then I would have to depend on the internal learn feature to auto correct over time. IF THAT WORKS, then proceed with the exhaust, let the system learn, THEN swap over to a 16 to 17 lb spring.

Just go slow, one change at a time. Don't rush it.

 

[Vegas Smith]

I don't think that would work because each sensor's voltage equates to a certain psi. For example, your 3bar might be reading 5v (35psi or whatever on your car) and it's telling the ecu 5v and the ecu is thinking that's 21psi or whatever because it believes you're running a stock sensor.

 

[jpfrk2001]

I don't think that would work because each sensor's voltage equates to a certain psi. For example, your 3bar might be reading 5v (35psi or whatever on your car) and it's telling the ecu 5v and the ecu is thinking that's 21psi or whatever because it believes you're running a 2bar.

That's why I am thinking if I stick with the stock injectors on a 3 BAR, the engine would lean out. The engine may not even run. It would crank and come to life, but would then die and shut off due not enough fuel. UNLESS the O2 sensors would help aid and tell the ECU to add fuel.

This is all in theory, in 2007 I put a turbo system on a 1993 Jeep YJ 4.0 motor. This was a stock, MPFI, Sequential system. I simply went with a 2 BAR MAP, Larger Fuel injectors to match proposed HP output, AEM wideband to monitor.

The motor Ran just fine on the stock ECU. Now this was a factory OBDI Chrysler ECU. It would run 8lbs of boost no problem at around 13.0 AFR which I know is lean at that time. I just ran High octane fuel.

I was helping someone else going forced induction on a similar motor/jeep. He swapped out to the 2 BAR MAP, but DID NOT change out injectors. His engine would not run.

I do have knowledge and understanding of tuning and how mechanical changes can affect the ECU tune in running the car. I have another platform in my shop on Holley EFI running a Terminator X system that will be turbo charged as well.
So worst case, I spend money on a 3 BAR, larger 600CC injectors to cover for the change in Voltage outputs at different parts on the graph and hope.

 

[Vegas Smith]

I've never owned a 2G, but I think the mdp (stock map) references boost or something to the ecu. It's not a full-blown speed density operation so maybe you could get away with it? Maybe someone else can chime in. Not to bash your idea for the project but it seems like a waste of time and energy unless you just want to try it for fun.

 

[jpfrk2001]

Thanks Vegas,
Yeap, I just want a fun Daily Driver. I really like turbo systems. I don't mind being a Guinea pig. Worst case, I just swap out the MAP and see how the ECU behaves. I will just do one Mod at a time.

I'll post my results.

 

[RWD4G63]

So worst case, I spend money on a 3 BAR, larger 600CC injectors to cover for the change in Voltage outputs at different parts on the graph and hope.

That's not how any of this works. Get ECMlink or a Link G4X plug-in and do it the right way. The map sensor is a reference sensor, the ECU adjusts fueling based on the MAF reading, which is why it can adjust for a mild increase in boost on stockish sized turbos. Trying to cobble things and 'trick' the ECU is just doing it wrong, and a recipe for hurting things.

 

[pauleyman]

Thanks Vegas,
Yeap, I just want a fun Daily Driver. I really like turbo systems. I don't mind being a Guinea pig. Worst case, I just swap out the MAP and see how the ECU behaves. I will just do one Mod at a time.

I'll post my results.

The existing solutions to add power are so good and so cheap nobody bothers. Ecmlink will do all that you require plus allow room to grow. Cheap is a relative term but still. I've been in this game 30 years and I've not seen anybody successfully try what you are suggesting. I have seen other hacks to fool the computer. You won't just alter fuel maps if this works (and I suspect it wont) but you change timing maps. Guys have switched out mass airflow sensors in a 1g and lied to the ecu. In a 2g if you try a different MAP I would guess it will conflict with the existing MAS. As pointed out these cars are not speed density from the factory.

 

[jpfrk2001]

ok all, will do.

I wont do any hacking. So I will just stick with Max 14.7 lbs of boost. I don't want to hurt this engine.

Thanks for the input and guidance. That is what I was wanting.

 

[pauleyman]

ok all, will do.

I wont do any hacking. So I will just stick with Max 14.7 lbs of boost. I don't want to hurt this engine.

Thanks for the input and guidance. That is what I was wanting.

You are not limited to a max of 14.7. That's not how the ecu does things. Ecu limits based on airflow mass. Mass will be different based on incoming air temp and what turbo you are running. Pressure is only part of the equation. The number the ecu cares about is MASS. In winter you will flow more mass for the same pressure. Also true for a larger turbo. You will flow more mass for the same pressure. Stock ecu will limit mass and you will know it when you hit it. Ecu cuts fuel and it is violent. You also will not hit higher hp on a stock 2g turbo. t25 simply will not flow enough. You can keep cranking the boost up but you just heat up air and don't flow any additional mass on a t25.