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Dyno Disappointment


dbgeek
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Cliff notes: dyno your car to expose any issues and make sure you aren't lean. Take spares - DME, MAF, TPS

 

Gentlemen,

 

I wanted to share some of my experience of some dyno time yesterday. It would appear that my car has a bad component somewhere that keeps the car from going into the WOT map. The result is that my car is running lean at WOT, whether running an aftermarket chip or the stock chip.

 

-My car has something wrong with it that keeps the DME out of the WOT map, thus none of the tuning they tried really affected the runs with the exception of removing the speed limiter.

-Fuel pressure is 46psi rising to 56psi under load, which is what was expected.

-Removing the headlight intake changed nothing. E46s are affected by the airflow through the box, so it was worth a try.

-Swapping the throttle body (and attached TPS) changed nothing.

 

I spoke to a friend of mine who does tuning and has lots of experience with BMWs. From here, we’re betting that it isn’t the TB or TPS. We are thinking that the MAF may be bad, dirty, or otherwise compromised. The only other factor is the DME itself – if the reference voltage isn’t correct, the TPS and MAF will not return the correct signals. Remember that this car is of unknown history, so all parts are fair game for suspicion.

 

I have ordered a replacement MAF, and I have the old (non-Spec3-legal) DME. Once I have all of the pieces, I will head to a local dyno to verify AFRs as-is, with replacement MAF, replacement DME.

 

How many of us have the same issue? Would you send me your dyno showing stock AFRs? You can remove the plot/numbers of hp and tq if you want – I’m more interested in knowing where the AFRs should be. Then I will know when I have fixed the issue.

 

This is important because if a Spec3 car isn’t reaching the WOT maps, the BW tune will do nothing but remove the speed limiter – continuing to run lean.

 

Thanks

Peter

 

PS - stock power tested in 5th was 170/170 ish

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Wow I have a lot to learn. (TPS is throttle position sensor, right?)

 

I'm wondering if this is affecting me. Noob racer issues aside, I did notice how others were pulling on me on SP's long straight.

After I get the oil leak fixed, it'll be off to the dyno and I'll let you know I have two of everything accept the DME (which is a 1995 MY btw)

 

This maybe a noobish thing but I'll just to throw this out there...I mentioned my possible power issue with a SpecE30 guy and he mentioned that he had to file down a bump stop behind his throttle pedal because it was not allowing him to get to WOT. Do we have a similar issue? Maybe the WOT map isn't being activated because the throttle isn't actually open fully.

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We verified the pedal (and throttle) cable was opening the throttle plate fully. By hand...

I will be probing lots of things with my electrical meter when I get a chance, mostly to verify TPS signal and MAF signal.

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Nick, I hope you don't mind, I cross-posted it here.

Notice that you are very lean - even leaner than my car, which means you have an issue.

I'll ask for permission to post mine.

 

This is on the mobile dyno at VIR last March with a stock exhaust and paper filter of unknown age. That is of course prior to my weekend ending money shift in October... I've got the corner weights down there at the bottom of the chart too!

 

DynoChart.JPG

 

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Wait wait wait.

 

Do not use the AFRs from the dyno that Nick was on.

 

I have used that Dyno and the AFR readings are not accurate. When I was on there recently, it showed my vehicle to be running in the 18:1 range, which we all know would have caused meltdown. I promise you that if those reading were correct, Nick would have more than blown his headgasket by now, let alone exploded the whole motor.

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Wait wait wait.

 

Do not use the AFRs from the dyno that Nick was on.

 

I have used that Dyno and the AFR readings are not accurate. When I was on there recently, it showed my vehicle to be running in the 18:1 range, which we all know would have caused meltdown. I promise you that if those reading were correct, Nick would have more than blown his headgasket by now, let alone exploded the whole motor.

well then... every dyno I've been on had accurate AFRs, so I assumed that was the case.

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