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Discussion Starter · #1 ·
Hey guys,

Under full throttle, my fuelling is running fairly well and will hit max RPM however if I'm gently easing the throttle, it will reach around 5,000-6,000rpm at 0.3bar and will hit a limit where it starts popping and throwing some resistance to go further, as if I were hitting the limit at 8,000. At this point, it hits 9-10:1 on the AFR which is way too rich, especially for the amount of load currently on the engine.

Is this, however, the result of it being too rich and thus causing this artificial limit? I am a little reluctant to modify the mapping without fully understanding this as this was how the car was when I bought it. The map seems completely fine on driving gently (without raising the RPM too high under low boost) and under full throttle.

I'm thinking of just tracing exactly where the cell is for when the AFR goes too rich and adding more fuel to the mixture over those cells. I have a custom made det can to listen for det so I wouldn't lean it out too much that it would start pre-detting due to heat.

Thanks!
 

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Discussion Starter · #3 ·
Worth pulling the plugs to check gapping and testing the coil packs? Or do you mean the ignition map? I get no misfires and it pulls fairly well at full throttle, absolutely no issues. I checked the ignition timing in the data log and that seems fairly close to the map settings for each cell.
 

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Discussion Starter · #5 ·
Nah man, imagine hitting your rev limiter but at 6000rpm when gently squeezing the throttle with boost at like 0.3bar as apposed to like full boost at 1.0 bar. That's basically what is happening. If I full throttle, it'll rev fully with no issues at all.

My only guess was that the problem is caused because of the AFR values I see on the wideband being between 9 and 10 at the point of this happening, thus running way too rich.

Any ideas anyone? :)
 

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Discussion Starter · #7 ·
Hey, it's been like this since I bought the car. The throttle position vs ignition in power fc has been set up and looks correct.

I assume if the issue were a TPS vs IGN, I'd see in the map watch trace that the load would be in a higher cell as apposed to mid range where it should be. I would have thought if the throttle sensor were broken, the level of boost would be at a set level no matter how hard I press on the accelerator? If I push the throttle further, the amount of boost increases.

I do have the handheld power fc commander so I could do some diagnostics on that to rule out the TPS.
 

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Sounds like it's overfuelling; popping etc, eventually the AFR gets low enough <9 and the engine basically won't run.

I don't know how the PFC deals with the TPS but that is still a possibility.

Is it a MAF or MAP based PFC?

If it's MAP based maybe there's a fault in the MAP sensor, it is seeing more boost than there really is and adding fuel - at WOT this would be the correct amount of fuel (a stopped clock tells the right time twice a day - and all that) but at low boost it would overfuel badly.
 

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Discussion Starter · #9 · (Edited)
Hey, there's no MAF, it runs a MAP sensor instead and is tuned to the wideband so not using the stock O2 sensors. I have the AFR gauge on top of my dash. I basically see the gauge dipping down to about 9-10 from 14.7 as the car comes onto boost which is too much really across the entire board. Never seen any check engine light on it and I have my tolerances set to extremely low, I.e. 20 knock threshold etc.

I suppose it could be the map sensor. A little research states that I can test the map sensor with a multimeter and just blowing to see if the voltage changes. I'll do this tonight! :)
 

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Discussion Starter · #10 ·
Thinking about it a bit more, there's actually two map sensors so I'll test both, but wouldn't the check engine light come on with idle failure. I'm having none of that, although come to think of it, the cranking ms at 80degC needed changing a while back because it wouldn't start when up to temperature.
 

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Discussion Starter · #12 ·
The map was done when I bought it as it's a third party Apexi Power-FC ECU.

Basically, driving back from squash tonight, it drives beautifully; the AFRs are fine, it gets richer as the turbo comes on but just goes far too rich. Upon data logging some of the values it definitely gets to around 9.5:1 AFR but what I didn't notice was that it actually goes to this when on WOT.

When I initially had the car, I'm pretty certain that it was hitting around 11.5 AFR which is what I'd expect it to be on full throttle. I would have thought that the AFR would be around 12.5 if I'm boosting at around 0.3bar as opposed to 1.0bar.

I have made no modifications to the car other than having a category 1 clifford alarm fitted by a certified installer. Since then the Innovate MTX-L AFR has flashed E9 on start-up but then comes to life and seems to act normal. (E9 is supply voltage).
 

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Discussion Starter · #13 ·
Update..

Tested the MAP sensors with a multimeter, they're both working perfectly so no issues there. Also my data log on the computer is showing valid readings for them so I can't attribute this as the cause.

I'll do a boost leak test tomorrow to check if there's anything up there.
 

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Discussion Starter · #14 ·
Update..

Did a boost leak test, no issues identified.

I will be recalibrating the wideband O2 sensor in the next couple of days and taking a look at the airflow system from the turbo to the intake manifold.
 

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Had several cars do this when there is a small boost leak that does not leak off boost but as soon as you go into boost the amount of air metered and mixed with the fuel isn't what is expected. Therefore because some air escapes more fuel to air so giving a lower AFR reading.
What boost leak tester are you using and what flow rate/pressure are you getting out if interest?
;)
Bob
 

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Discussion Starter · #16 ·
Hey,

I'm using an attachment to the front of the turbo to create the desired pressure. It's probably worth mentioning that I am using map not maf sensors; wouldn't a leak in the intercooler or somewhere else along the way not matter if the pressure is detected in the intake manifold? The fuel map would basically read off at the right pressure, surely?

Thanks!
 

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Discussion Starter · #18 ·
Hey, yes I did. The tuning was whack! Long story short, it's fairly hard to get the Apexi PowerFC d-jetro to have a nice part throttle tune but we managed to get a nice sweet spot where it no longer goes rich and pulls nicely :)

I'd recommend getting a good tuner or going for the Link G4+
 

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Just came across this post, mine seems to do something similar, higher revs its like it hits a wall (not 8000 rpm) sometimes theres big bangs out the exhaust and a cut in power......


Is this more link g4+ boost control gremlins as mentioned>

http://www.gtr.co.uk/forum/506889-r33-turbo-lag-annoying.html#post5242833

<there.

Or something else....


The fun and games continue.....
 
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