DaveB

We are stumped and are calling on the wisdom of the masses. Here is the scenario.

New S5 engine build.
New S5 wiring harness
Known good S5 ECU
Known good OMP

Car runs great in monsoon conditions first race weekend

Car goes for new programmable ECU and falls on its' face. It acts as if there is a "rev limiter" at 5500 RPM.

Here is what has been done:

Replaced known good ECU
Replaced known good OMP.
Checked fuel pressure at 40 lb/in2
Checked all other sensors with substituted RTEK ECU. All sensors check fine on a dyno run.
All plugs look good.
Timing checked at factory spec
New seals and grommets on injectors

Anyone have any ideas, or need more information? If you find the answer, you win the prize.

Gorilla RE

iTrader: (1)

So you put in a Stand alone ECU and the car falls on it's face?

DaveB

We put in the RTEK programmable ECU for a pull to datalog all the sensors. It is a modified stock ECU that acts like a standalone. We added 10% fuel at 5500 RPM which is exactly opposite of what normally happens and it still fell on its' face. I should be leaving for the IT Festival today. Looks like it isn't going to happen......

C. Ludwig

iTrader: (27)

I'll wade in here with Dave for a description of the problem. I put the engine together for Dave last year. He took some time installing it and made one race earlier this year. The entire race was run under caution because of torrential rain and he can't be positive he had ever loaded the car above 5500 rpm before this past week when we had it on the dyno. Under no load it revs cleanly to 7k+.

The car is an ITS prepped FC with S5 components. Fuel and ignition system is completely stock. He brought it down last week and we were going to sit it on the dyno, baseline the stock ECU, install the Rtek and tune it.

First pull with the stock ECU and we hit what amounts to a rev limiter at 5500 rpm. At that point the engine picks up a very smooth and stable misfire. Just like rev limiter. Won't rev past 5500. At 5500 rpm the fuel trace shows very lean. It's like the fuel is being shut off....or it's just reading very lean because of the misfiring.

First thing we did was install a fuel pressure gauge. We have a stable 40 psi rail pressure up to and through the misfiring. So it's not a fuel supply issue. Next thing was spark. We have good spark on all 4 plugs and properly timed up to and through the misfire. The plugs are fresh and clean. So...if we have properly timed spark and we have compression then the problem is fuel related. Since we have pressure then it's an injector or ECU issue.

Next thing we did was swap in the Rtek. The Rtek ECU produced the same results with one exception. The point at which the engine began to misfire was moved up to 6500 rpm. Nothing else changed. With the stock program in the Rtek the fuel curves laid over the stock ECU exactly up to the point the stock ECU began to misfire. We logged all relevant sensors through the Rtek and nothing was given a reading out of the ordinary. Nothing like the AFM, TPS, MAP sensor, etc. suddenly crapping out at a certain point. Next thing we did was add fuel beginning at 5500 rpm just to see what would happen. The fuel curve richened up right to the point where it began misfiring but the result and point of misfire was still the same. Before adding fuel with the Rtek A/F was in the low 13 range at the point of misfire so it's not getting too much fuel at that point and drowning the spark. After adding fuel A/F dropped into the 12's with the same result.

Put the stock ECU in and began probing the injectors to see what happened. Unfortunately to noid light we were using was giving nothing for results. We probed the secondary outputs directly at the ECU and got nothing. So the secondarys aren't firing right? Well then we unplugged them all together and made a pull. The fuel curve leaned out an appropriate amount from 3500-ish up to 5500 where it hit the limiter again. Telling me the secondarys had been working even though the noid light (confirmed good BTW) wasn't showing a pulse at all.

At that point the only thing I could even think was an OMP problem. Even though I've experienced the actual limp mode and it's characteristics are nothing like what is going on here. We packed it in for the day defeated. Dave took the car home and swapped in the known good OMP and ECU and took the car for a test drive. Same results... Ideas?

j9fd3s

iTrader: (3)

i had one car (s5 t2) that didnt turn on the seoncdary injectors unless the fpr solenoid was plugged in.

results were kinda similar you yours, afr was in the 12's at low rpm, and as it passed 3500 it would gradually lean out, being a turbo car we'd shut it down instead of pushing.

put the fpr solenoid in, and bingo, afr was in the 12's all the way up to 8500.

it did have an fcon in it, but not sure if that made a difference or not

easy to try anyways