Dangers Of Running Manual Injectors With Auto Ecu???????

[91tizzy]

JUST PIG RICH???? I hope so...car never has issues and is spoolin great with the 13g and the profec b set at 14 pounds.....thought that it was runnin rich cause i only get about 20mpg on a good day but the plugs are white though

 

[Avionixx]

I wonder if there is a difference actually, the VFAQ says they do, but I can't imagine it could be that big of a difference.

 

[91tizzy]

i figure the timing might be a little off between the two due to some load variations but as far as fuel is concerned I agree....just so i dont have to worry about being lean....one would think that with the 450's in the car when the ecu thinks it has 390's that it would be rich....like i said the plugs are white but never have an issue....could the ecu be tryin to lean the car out if its seein too much fuel across the board? I dont really care if it is as long as it isnt runnin lean.....btw i am in the process of getting a eprom for the car regardless but just wonderin for the inbetween time till I get link

 

[redline2k6]

i ran 450s on a auto ecu and a 14b at 15psi no problems at all with a 2g mas was a little on the rich side but nothing to extreme

 

[tbonitz301]

I would say your just going to run rich. There's 60cc difference between the manual injectors(450's), and the auto injectors(390's).You should be fine. But i have to ask why?You can find a set of 390's for like 50 bucks

 

[91tizzy]

because just like redline did I have a 14b and three inch exhaust going on the car and still want to run 14 pounds or so....previous owner actually installed the 450's because the 390's were clogged (yes I checked for head gasket issues before my purchase) but anyway's this is what I figured so thanks guys

 

[91tizzy]

hey redline can I ask what the car ran with the 14b? Im shootin for low low 14's at least with my shiftbox that Im ordering

 

[1992awdlaser]

You will be flowing 13% more fuel than needed. It will have the same side affects that overrunning the fpr will have. The extra fuel will wash down the cylinder walls. This will eventually contaminate the piston rings, which will require a rebuild sooner than needed.

 

[steve]

Because of the difference in base fuel pressure there is only about 20cc difference between the auto injectors and the manual ones. So only about a 5% difference. The auto injectors are run at about 390cc and the lower base pressure of the manual caused the 450 injectors to actually be about 411cc.

 

[Blindsey]

If you are that worried about it switch to a manual ECU. Timing is a little different. I have one for 50 shipped.

 

[1992awdlaser]

Because of the difference in base fuel pressure there is only about 20cc difference between the auto injectors and the manual ones. So only about a 5% difference. The auto injectors are run at about 390cc and the lower base pressure of the manual caused the 450 injectors to actually be about 411cc.

Steve is right about what he said. But, you are still going to be flowing 13% more fuel than needed unless you lower the fuel pressure on your car to the manual fuel pressure of 37.5.

 

[91tizzy]

Im wondering when I am richest cause It hazes when Im at foolboost(according to my buddies that are always BEHIND me) but the plugs are NOT showin any signs that its running rich...if anything it looks like its lean by the plugs....oh well Im not all that worried about it cause I figure once the 14b goes on there I will have plenty of air for that added fuel and like I said I am planning on getting link within the next month but I was just curious about yalls thoughts cause I didnt find anything on this by searching...

 

[91tizzy]

anyone have a stock manual fpr they would like to cut loose of for a small fee?

 

[steve]

Steve is right about what he said. But, you are still going to be flowing 13% more fuel than needed unless you lower the fuel pressure on your car to the manual fuel pressure of 37.5.

Yep, I missed what the OP was doing.

The way I read the question the OP has a manual car with a manual FPR (36.3 psi) and manual injectors (450cc) but an automatic ECU that expects 42.7 psi fuel pressure and 390cc injectors. I'll include the numbers in case people don't follow how you came up the answer.

The effective flow rate of the manual setup is:

SQRT(new pressure/old pressure) * old flow rate

SQRT(36.3/43.5) * 450 = 411.08 cc/min

The effective flow rate of the automatic setup is:

SQRT(42.7/43.5) * 390 = 386.4 cc/min

Adjustment = (old flow rate / new flow rate) - 1

386.4 / 411.08 - 1 = -0.06 = -6%

So ignoring the differences in timing and fuel maps between the two ECUs, the automatic ECU will deliver 6% more fuel when running in a manual car that it would have in an automatic car.

But putting the 450s into a automatic without changing the automatic FPR (the actual question here) gives:

SQRT(42.7/43.5) * 450 = 445.84 cc/min
(386.4 / 445.84) - 1 = -0.1333 = -13%

Sorry.

 

[91tizzy]

steve is the man and yes just for clarity it is a automatic car with a stocker turbo and 450's with stock auto ecu and stock auto fpr...

 

[1992awdlaser]

Yep, I missed what the OP was doing.

The way I read the question the OP has a manual car with a manual FPR (36.3 psi) and manual injectors (450cc) but an automatic ECU that expects 42.7 psi fuel pressure and 390cc injectors. I'll include the numbers in case people don't follow how you came up the answer.

The effective flow rate of the manual setup is:

SQRT(new pressure/old pressure) * old flow rate

SQRT(36.3/43.5) * 450 = 411.08 cc/min

The effective flow rate of the automatic setup is:

SQRT(42.7/43.5) * 390 = 386.4 cc/min

Adjustment = (old flow rate / new flow rate) - 1

386.4 / 411.08 - 1 = -0.06 = -6%

So ignoring the differences in timing and fuel maps between the two ECUs, the automatic ECU will deliver 6% more fuel when running in a manual car that it would have in an automatic car.

But putting the 450s into a automatic without changing the automatic FPR (the actual question here) gives:

SQRT(42.7/43.5) * 450 = 445.84 cc/min
(386.4 / 445.84) - 1 = -0.1333 = -13%

Sorry.

I figured that you read it wrong. I had to double check after your firt post just to make sure I read it correct. The only way I thought it was an auto is since he mentioned 13g.

steve is the man

Yes he is.

 

[steve]

The only way I thought it was an auto is since he mentioned 13g.

That's what finally clued me in also.

 

[91tizzy]

I figured that you read it wrong. I had to double check after your firt post just to make sure I read it correct. The only way I thought it was an auto is since he mentioned 13g.

Sorry for not being clear at first guys I did forget to mention that its an actual auto car in the first post

 

[DroopYeyeS]

I am running a VERY similar setup right now. I have a '91 a/t that looks to me like the previous own has done an engine swap for some reason ( propably timing belt). Point is I also have 14b with 450's, and I do believe the fpr is from a manual as well. On this setup my logger says I'm running lean on the FTRL, 100% FTRM, and rich on FTRH. I put the GM maf & maf-t on it to try to tune out the lean condition on the FTRL, and rich on FTRH. No luck on this idea. So I next went ahead and installed an safcII that I had to see if it would help. Now with this installed doing the base setup that I have seen, more times than I can count, on here the car is still very lean on FTRL and rich on FTRH. I then tried to ADD fuel, this started to cure my issue. I still don't have it totally ironed out yet so I'd love to hear your results.

 

[steve]

On this setup my logger says I'm running lean on the FTRL, 100% FTRM, and rich on FTRH.

This is classical symptom of a boost leak.
Under vacuum extra air is drawn in unmetered causing the ECU to see lean feedback from the O2 sensor because there is more air than expected reaching the cylinders. Under boost metered air leaks out causing the ECU to get rich feedback from the O2 sensor because less air made it to the cylinders.

 

[91tizzy]

so im under the assumption that a manual fpr will help zero me out more fuel wise?????...some gracious person has offered me one so i think Im gonna switch them out and see how she takes it...im still a little leary it sounds like i need to do a boostleak test as well because the plugs look a little on the lean side....had a tester and was ready to do it but moved away temporarily so looks like thats on the front burner. Thanks everyone

 

[1992awdlaser]

so im under the assumption that a manual fpr will help zero me out more fuel wise?????...some gracious person has offered me one so i think Im gonna switch them out and see how she takes it...im still a little leary it sounds like i need to do a boostleak test as well because the plugs look a little on the lean side....had a tester and was ready to do it but moved away temporarily so looks like thats on the front burner. Thanks everyone

It will help solve it. It is not going to solve it completely since the ecu is set up for the 390's. It will be flowing the 6% extra fuel mentioned earlier by Steve.

I have seen plugs look lean even when the car was running the stock fuel curve, which is quite rich. The way to know is with a wideband or by watching the o2 sensor volts you can guess pretty close to what the air/fuel ratio is.

 

[Blindsey]

I don't know why you don't just switch to a Manual ECU. You can get a NON Eprom for really cheap. As soon as i switched out the ECU in my Auto it made a world of difference.

 

[91tizzy]

My reason being is that Im purchasing a 87 turbo regal and dont have 50 bucks to spend on the manual ecu right this second but I dont want the fact that the car is runnin rich ruin my piston rings prematurely...car has been set up like this for the past five thousand miles and I was thinking that I could be one step closer if I picked up a manual fpr that someone had layin around and swap them out now for dirt cheap being that I would eventually need to do that anyway even once I can afford a manual ecu....where can I find a manual ecu for dirt cheap???

 

[dikdiamond]

You could try a salvage yard,but good luck. I bought my manual ecu off this sites classifieds for 150,and that is pretty cheap for one with rebuilt caps. I bought the fpr off of Ebay for 20 bucks,you can try a salvage yard for that too.