Disappointing Dyno Result

[s2_bo]

If knock sensors are plying up then the ECU will normally kill the boost control till you switch ignition off and back on..
Atleast thats what happened when mine went..

[KaraK]

Spoke to Andy about this earlier, suggested cleaning all connections and checking for leaks - peak boost was ~1.1bar so definitely not right!

There was a scooby on the dyno that ran 250, as it ran similar figured at his last run that's a pretty good benchmark. The car is definitely down ~50bhp and the same in ft/lbs I'd say...

There is a known coolant leak so my suggestion is get that checked - hopefully it's the HG - sort it all out and make sure it's airtight, no codes etc when put back together make sure it's seeing a solid 1.4bar and get it back on the dyno.

The scooby in question was mine, first time I've had it dyno'd but the guys at the RR are scooby specialists and suggest that my 253 was pretty much spot on for a PPP'd car and it was more or less what I was expecting as well.

The key thing for me is that the S2 has always had a noticeable edge over the scooby on the road and that has been absent lately.

[martinjs]

I thought you had a suspect head gasket leak? or did you fix it already?

[Billman]

Instead of wasting time and money on dyno runs (except when mapping), get a Racelogic Performance Box and measure in gear acceleration like 60-90mph instead.
Alternatively, just use Vagcom and log the time it takes from 4200rpm to 6500rpm in 3rd gear. Even the £10 vagcom copies will do this just fine. This is the so called FATS test that is extensively used by the B5 crowd. Very accurate, repeatable and costs nothing. In addition, a huge database of times exists, so it is easy to judge performance level.

Where is this list with times??

[Ross]

@Karak - now you have a PPP... how many times you gonna change the Scooby?!

[Sonic]

@Karak - now you have a PPP... how many times you gonna change the Scooby?!

Until he stops crashing them

[KaraK]

@Karak - now you have a PPP... how many times you gonna change the Scooby?!

I've had this one for a couple of years now, to be fair I only had to get rid of the last one because it got driven in to!

[EspenW]

Where is this list with times??

http://fats.audi-quattro.org/

http://www.mrctuning.com/fatsview.php?carselect=B5 S4

http://www.mrctuning.com/fatsview.php?carselect=B5 RS4

http://www.mrctuning.com/fatsview.php?carselect=S2/RS2

[Sonic]

Cheers for the comments guys, some good things to check for.

The result is in flywheel bhp not wheel, that was my first thought, but as Karak mentioned his is producing ~250bhp and there is no way that's wheel hp.

I've complained the car has felt as if it's missing it's "edge" over the past couple of months, last time i was at the 'ring in August it just didn't quite feel right, so really this just confirms what my butt-dyno said all along.

As Karak said, this backs up recent real-life tests where i'm not unable to overtake him, which isn't usual

I do have a known problem with the head, and the car is due for a head rebuild to resolve this, but the results are far lower than i'd expect just from a small coolant leak in the head.

The MAF and boost are the places to look i think. I shall persist!

In the meanwhile, here is a video of the runs - http://www.youtube.com/watch?v=PilfDZdJdog

And the graphs i had printed:

BHP/Boost pressure. You can see it peaks at just above 1.1 bar @ ~3500rpm, and then slowly drops off. With v-stream homefry mode i'd expect more than this, and the boost gauge in the car confirms exactly what the dyno has said.



BHP/torque (ft/lb). Again, expecting more



BHP/Lambda. You can see it begins to run lean when the turbo kicks in.

[EspenW]

I'd say AFR looks pretty normal: stays at 11.8 from approx 4K to 5K, then goes up to right under 12.5 at around 6K.

[UrS4boy]

With boost peaking at only 1.1 Bar and then trailing off to 0.6 Bar (wastegate spring pressure), it seems to me like either the N75 isn't working or there is massive wastegate creep. That or boost leak (but it must be a split hose that opens up slowly, otherwise, if the leak was abrupt, the ECU would go into limp mode).

[europeanme]

There is a known coolant leak.

Andy, I had the exact same thing when Dest organised the RR session in Wellingborough last year....i had a coolant leak and my power was disappointingly low...244 if memory serves and was expecting over 270....

The guy who did the run said this could effect the running and ultimately the power...

at least when your out on the road and it doesn't feel right, you aren't imagining it...but when it does put a smile on your face it is what it is all about at the end of the day...

[Rusty]

WG spring pressure at redline is not 0.6 bar, it's ~0.3 if setup correctly, dropping from ~0.4 at WG crack. I've done some testing on the standard spring and a stock turbo car.

If there was a big leak then the lambda (AFR) would be out and the overboost correction would cut in every now and again. The AFRs sound correct for Paul's setup. I'm not sure what version I tested but I experienced issues with back to back runs so worth checking to see if this was remedied. The car felt like it was holding back and the times 0-60 and 30-60 agreed, being slower than the stock homefries.

Sounds like some VAG Com work will help to identify what isn't being measured correctly. As before, altitude sensor is worth a look as I'm sure that can drop boost a lot if it thinks you're above 2000m.

[Billman]

What happens if the wg membrane is bad? The wg would lead and thus not providing enough boost.

[Rusty]

Other way round, blown diaphragm = more boost as it is the boost that opens the WG, not shut it! Not a fail safe system