My 20v 2.5 stroker track day ur quattro

[DamoM]

So have you got any experience of mapping this exact turbo on an I5 Dmitri?

I am really keen on seeing a comparative dyno plot but so far, despite asking several people, I have seen nothing.

[prj]

Ok and please excuse my ignorance but what is the point of adding more boost, getting detonation, having to retard the ignition to compensate which results in you gaining virtually no more power? Surely you are better off leaving the boost at the level it was at in the first place?

You were correct up to the point where you said "gaining virtually no power".
The break even point on a 7.6:1 CR motor is definitely not 25 psi on these engines.
On your motor the break-even point would be somewhere closer to 40 psi in the midrange, where adding more boost will not make more power. This is assuming 98 RON pump gas. On race gas it would easily take more boost.
The stroker I linked is running 38 psi in the midrange, which was it's break-even point, as adding more boost (up to 42 psi) did not result in more power anymore.

Even a bone stock I5 with stock pistons and stock head keeps making more power all the way to about 31 psi, until you hit octane limit.

Haven't mapped a GTX3071R, have mapped plenty GT3076R's, and the manufacturer flow rating and compressor maps are similar - so there is no reason why you'd make what you're making, seeing as no one else seems to have trouble getting GT3076R performance with earlier spool from the GTX3071R.

[diesel des]

sounds like something simple not right like plugs or something. you shouldn't of had det issues. not at that compression. have you checked to see what pressure loss you have across the intercooler and also what inlet manifold temperature was. I think something simple is causing you the issue.

[AndyP]

My CR is not far off 10:1 and I run 22psi on a normal GT3071 with no det.

[DamoM]

My CR is not far off 10:1 and I run 22psi on a normal GT3071 with no det.

What power do you have?

[prj]

Andy, I doubt you have 10:1 CR...
Stock is around 9.

Regardless - this is all speculation here without proper logs.
Shouldn't be that hard to make with a standalone ECU

My reply was prompted by "I don't see how people make more than xxx power" - and the answer is, they run more boost. For 1.7 bar your results are as expected. If you're running it flat though, then you're missing out as this is not a top end turbo.

[DamoM]

sounds like something simple not right like plugs or something. you shouldn't of had det issues. not at that compression. have you checked to see what pressure loss you have across the intercooler and also what inlet manifold temperature was. I think something simple is causing you the issue.

Plugs look good. Intercooler pressure drop is virtually zero (we measured it after we installed it at 30psi). We have a 'before and after intercooler' temp gauge and inlet temps are good at only 10 degrees over ambient. They climb to 70 degrees before intercooler on full boost.

[A80Avant]

Andy, I doubt you have 10:1 CR...
Stock is around 9.

Regardless - this is all speculation here without proper logs.
Shouldn't be that hard to make with a standalone ECU

My reply was prompted by "I don't see how people make more than xxx power" - and the answer is, they run more boost. For 1.7 bar your results are as expected. If you're running it flat though, then you're missing out as this is not a top end turbo.

Andy has pistons that ended up having less dish on his stroker and he measured it at 10.1 . It was JE mistake

[DamoM]

You were correct up to the point where you said "gaining virtually no power".
The break even point on a 7.6:1 CR motor is definitely not 25 psi on these engines.
On your motor the break-even point would be somewhere closer to 40 psi in the midrange, where adding more boost will not make more power. This is assuming 98 RON pump gas. On race gas it would easily take more boost.
The stroker I linked is running 38 psi in the midrange, which was it's break-even point, as adding more boost (up to 42 psi) did not result in more power anymore.

Even a bone stock I5 with stock pistons and stock head keeps making more power all the way to about 31 psi, until you hit octane limit.

Haven't mapped a GTX3071R, have mapped plenty GT3076R's, and the manufacturer flow rating and compressor maps are similar - so there is no reason why you'd make what you're making, seeing as no one else seems to have trouble getting GT3076R performance with earlier spool from the GTX3071R.

I would agree with what you say if one of those individuals was prepared to post their dyno plot. :banghead:

[AndyP]

What power do you have?

It's never been on a dyno, but according to Vas's Racelogic performance box, it's got around 320whp.

[prj]

Well, I just posted a dyno plot of someone making way more power and torque than you at 38 psi on a higher compression ratio than you on a 2.5 stroker.
According to your logic his engine should be in pieces and running anything more than 25 psi is impossible.
Sorry, but what you write does not line up with the 100 odd I5's I've mapped, that's all.

[A80Avant]

It's never been on a dyno, but according to Vas's Racelogic performance box, it's got around 320whp.

With misfires which make the graph cut out A LOT. Pretty soon, once some springs of mine are made we will check Andy's car again

[AndyP]

Andy has pistons that ended up having less dish on his stroker and he measured it at 10.1 . It was JE mistake

It's either that, or the head I used had already been skimmed, which I didn't check. A static compression test gives around 200psi, which according to the back calculation formula I found on-line that is around 9.9:1.

[AndyP]

If you are in any doubt about det, use water/meth injection. It's a comparitvily cheap mod for the S2, I know Dmitri like the Aquamist HFS-3 which is quite expensive but I use the Devils Own which is about half the price. It does not have all the features of the HFS-3 but it's still a good system.

[prj]

While water meth is good, with a 7.6 CR there's deffo something else going on...

Also, if you use meth injection without a failsafe, you can not map specifically for it, only use it in small amounts...

Because if something happens to your meth kit you are gonna melt your engine otherwise. That's the main thing why I use Aquamist on everything.
Don't get me wrong, any meth injection system is going to result in massively lower IAT's, better cylinder filling and more power. But I think in this case it won't do much...