Weird dyno graph, does anyone know what it could be?

[Mazman]

Ok, ill post the dyno graph i have.

I have been having this problem for a while now, and cant seem to fix it.
Changed fmic, exhaust manifold, 4"dump/mid, and now im just posting it out for others to see and maybe someone has had a similar situation, well, im hoping anyway.



The RED line is after adding a few more degrees on a dyno day recently, the BLUE line is what i came at the dyno day with before touching the timing.

As you can see, as i hit FULL boost, the power curve just dies! it flattens out and runs flat all the way to redline, instead of still climbing up.
The flattening part is at about 5500rpm, just when i hit full boost, so im not gaining anymore power after that 5500rpm.
Boost is at 26psi.

Its a toyota supra jza80
Turbo is a gt4202, motor is untouched.
850cc and 044 pump, 75% duty cycle, wideband at steady reading.

Anyone with idea's?
Every other dyno ive seen doesnt go flat like this, so i dont think its the cams, maybe valve springs weak?
Im running out of idea's

[fixeruperer]

we had a supra on the dyno and it had crower 272 cams but standard valve springs at about 550hp at similar boost it was doing the same thing, we replaced the valve spings and it fixed it making around 640hp at 28psi.

wheel spin can look like that aswell.

[Devils]

Wow thats interesting!

I had a car do something similar to that but the power line looked more like the boost line does on your graph "spiky".

Turned out to be an ignition problem, gapped the plugs down a touch and checked all the motor earths etc and it was fine until we tried to turn the boost up a bit more from 14 to 16psi... turn it back down to 14 and it was fine.

Dont think that is your problem but just thought I'd add to the possibility!

[mrshin]

Got a dyno graph with lambda plotted as well? That might help in picking up issues with ignition, valve springs, etc. But for now I'm voting for springs.

[-GT-]

Yeah my first thought was stock valve springs too - surely somebody out there has some definitive experience with 2J stock valve springs and boost thresholds; is 26 psi the limit??

Otherwise, as above, start working through ignition breaking down issues. What plugs and gap are you running?

[The Real Roadrunner]

first of all put it on a dyno where the guy who's using it knows how to plot a run.

secondly im thinking valve float may be the prob but id also be logging about 5 other things at the same time to make a more educated guess.

thirdly how much extra timing did you add? and why is the boost lower and coming on later on the 405kw run?

cams are probly starting to restrict you also.

cheers
linden

[Mazman]

This AFR graph shows it running good, but its from another day and another dyno, with less power, due to very low timing.

this is the dyno before i changed the fmic and exhaust manifold, but was running the exact same setup on everything else and exact same boost 26psi.


another different dyno, also before the fmic and exhaust, same boost 26psi.



I dont have the plot of the new dyno with AFR, but my wideband is showing me high 11's

[fixeruperer]

when the boost comes up the power goes down and vicer versa, looks like float.

does the tuner have electronic ears on it ?

[Mazman]

-GT-
im running new coil packs and hks dli, plug gapped to .6mm
People have been running much more boost then me with no spark issue's.

The real roadrunner,
It was a dyno day only, so there was no time for such a thing.
Previous dyno tune by hitman (wich you see on the graph i posted just then-race solutions) has been very dissapointed, so ive since then tried doing it little by little myself, checking other peoples timing and so on.

On that day, the boost was 27psi, but when changing the timing and fuel a bit, it came down to 26psi so it must of affected it a bit.

ill show you teh timing maps:

This is hitmans map wich was 323kw.


this is the 405kw run map:

a fair bit more timing.

[The Real Roadrunner]

you may be going abit overboard with 19deg at 26psi (this is an assumption and i havn't heard it on the dyno so im not 100%)

there are alot of variables that would be needed to be checked but i still think springs will be abit on the soft side for that boost. (gen3 3sgte ones shit the gear @22psi 7200rpm)

cams would be on the list of things to do also for a variety of reasons.

the only thing i would suggest really is to find a competent tuner that is capable of sorting this out for you.

(there's a couple i could recommend but id chat with you personally b4 doing so)

cheers
linden

[BigWorm]

I've heard of a 2J doing this once before at about the same power levels (although it doesn't seem to be a common problem), & was fixed with new/better springs. It was Jay Ducas' stock looking blue Cressy over here in Adelaide, it was making good power until a fuel pump died resulting in the untimely death of a piston, and once it had new second hand bottom end & better fuel system it did the same thing on the dyno. A set of valve springs latter & it was making up to 450rwkW.

So, that's another vote for valve springs from me.

[The Real Roadrunner]

the one main contributer for me thinking springs is that in every graph (even the low power ones) as soon as it htis 25psi it all turns to poo.

but at this power level a set of cams and gears will do wonders for midrange/drivability (well thats my opinion anyway)

cheers
linden

[GriZZly]

Tried running say 20psi and seeing what happens at the same rpm? does it continue building power past 5500 or just drop off at either 20psi or 5500 as before..

[Mazman]

Tried running say 20psi and seeing what happens at the same rpm? does it continue building power past 5500 or just drop off at either 20psi or 5500 as before..

funny you should ask this.
Here is a run from hitmans tune back when no upgrades to cooler and exhaust, with low timing numbers.
Its only at 19psi!... but have a look, same thing, 5500rpm, full boost reached and boom, power flat/drops!



Surely valve springs are ok at 19psi? this is why im confused and at first thought it was something else, due to low boost but same problem, and didnt think it was valve springs.
I always thought it was the tune, very low timing numbers are also not a good thing!

But now with much higher timing numbers, im getting much better power but same curve.
You cannot feel this on teh street, i have not known about it until it was put on teh dyno.

The real roadrunner,
timing can/should be able to go even higher, i have methanol/water injection running at such boost, i only run 20psi with 98 fuel.

thanks for all the feeback so far, hope to narrow it down eventually.
Would like to see what it can do without going cams, but if that curve is a result of cams/springs, then ill have to change it, would rather not touch the head until im ready for some headwork.

[The Real Roadrunner]

ahh, didn't know about the water injection.


cheers
linden