Thoughts on this dyno graph, is my power being restricted?

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After having a read of the 'Very dissapointing dyno on a gt42/supra ' thread and after just recently getting my car onto the dyno. I think i have the 'similar' sort of problem.

It is making okish power, but the main concern that the tuner says is there is a restriction somewhere. As the sudden power change just after max torque hits and then its a linear line all the way to redline. The only reason its making power is because the large turbo is fighting past the restriction.

Personally i think it is a my intercooler, as it is a very small 2" thick core with ordinary tanks. But what else could cause a restriction like this?

Car in question is a Turbo Hilux 3RZ-FE, with GT35R and custom everything.

[myne]

What happens when you reduce the boost? How does the torque curve change?

Reason I ask, for some reason I have the gut feeling that it's valve springs.
The intercooler cant be helping, but my gut seemed to go straight for that, so yeah... Scientifically unproven!

But regardless, if you reduce the boost, the point that the power drops should climb a bit higher - that is if it is a restriction. Meaning the curve should change meaningfully, and thus allow you to figure out the root cause - be it simply the IC, igntion or valves.

Does the boost sharply increase at the point that the torque dips, or does the wastegate/bov suddenly open a lot wider?
I ask this because that's an obvious pointer to an inlet restriction. If the air is piling up, the boost should rise, or there should be an obvious sign of boost modulation.

Does the AFR go a bit wonky? If I recall, a shaky AFR is a classic sign of valve spring issues.

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but if it was valve springs, it'd fall on its face and not make any top end power....?

tuner didn't make any mention of what it was like with less boost... I assume it is similar.

[myne]

thought of more *edited previous post*

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AFR is rock steady, doesn't rock around. and its at 11.5:1 at 14psi
No spiking, its a 44mm TiaL wastegate, once it gets to boost, it opens up. Doesn't spike on the road either. (unless you call 0.05bar a spike...)
Tuner said there was no valve float/bounce.

Other things that have been suggested is the grunter style stock cams im using....

[Joshstix]

What revs does that graph go to?

I can't quite get my head around how your torque numbers can be increaseing as revs are increasing but the power graph seems to be falling. Since power is pretty much torque x revs any time both of those increase there should be a corresponding increase in power.

I'm confused.

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Rev limit was set to 5800rpm.

Its making excellent torque, but as been said, not making the power it should be. Only reason it is making the torque that it is, is because the big turbo is pushing thru the restriction.

So far the main suggestion is that the intercooler is the major airflow restriction, and will be upgrading it to a 4" thick jobbie of ebay.

[Joshstix]

The thing is power and torque are directly related.

If you make X torque at Y revs then you are making Z power.

You can't be making good torque and not be making the amount of power that corresponds to that torque at the revs it's being made.


Edit

Hang on I'm reading your graph all wrong the higher line is your torque numbers, doh. The maths still stands though.

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I already know that there is a correlation between those

HP = (Tq x RPM)/5252

Which doesn't add up.

[Joshstix]

That's what I'm saying though. The maths doesn't care about you intercooler or any kind of restriction. To make more power it has to either make more torque or more revs. I think the fact that the torque graph has been plotted so prominantly on the graph makes it look like it's making better torque than it really is.

It does definately look like it's falling over once it hits peak torque due to flow restriction of some kind though. The 3S tends to do this due to two causes either the tiny turbine of the CT26 if it's still in use or head flow on engines with bigger turbo's.

[-==L=a=N=c=E==-]

thanks for that, makes a little more sense now.

Well if it is a flow restriction then, what else could it be other then Intercooler and Cams. Thats the main thing im trying to get at.

[Joshstix]

Sorry mate I really don't know the 3RZ well enough to give you an informed answer on that one. Actually if I'd read your graph correctly the first time I don't think I would have replied to this one at all, no need to clutter it up on you.

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i don't expect anyone to be an expert, since not many turbo 3RZ's are around, just out there trying to get some opinions on what it could be. Thanks anyways.

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For anyone else interested......

topline is torque, bottom line is hp (max hp of 304.6)

redline was 5800rpm.
approx RPM calculated
48kph = 2100rpm
62kph = 2707rpm
76kph = 3320rpm
90kph = 3950rpm
104kph = 4550rpm
118kph = 5150rpm
132kph = 5760rpm

[-GT-]

Combination of the two? Might just have to replace one and see the difference? Obviously intercooler is cheaper and easier.

You seem inclined to think the cooler is a restriction, but without seeing it i can't really offer an opinion. As to the cams (and possibly head flow), is the 3rz a tourquey, low-down work-horse type engine? If it is, that would suggest cams and head are designed to make torque low in the rev range and as such will be a restriction to high end power.

Start with the cooler and see what improvements you get?

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The cooler is 650x300x55 with ordinary end tanks on it.
The 3RZ is a truck motor, so yes designed to make heaps of torque.
I suppose there is only one way to find out.

[oldcorollas]

hmm, you are losing 10% torque from 4000-5700 ish..
if it was flat, it would be all you could hope for

for power, cos you are losing torque, the poer could be 10% higher at max rpm... but it doesn;t look that bad
from 4000 to 5700, you are increasing flow (hp) by 33%, whereas ideally, you would increase by 43% maybe (assuming you are making max torque at 4000)

11.5 is fairly rich.. could the boost + rich mixture be making it harder to ignite?

if you hit cams limit, it should drop off faster. if you hit valve float, it should be similar.. fast change with rpm.

it could be a number of little things adding up, but you are getting 75% of the increase in power from 4000 to 5700 that you could/should be getting..

oh, before you go all spendy on a new IC... measure the pressure drop across it (ie from the piping before and after it) if not much pressure drop no need to replace (unless temps go up)

actually, it would be very informative to hook up two pressure gauges, one to each side of IC, and give it a bootful.. if one goes up faster than the other, then it has issues..

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hrrrrm, getting so many differing comments so far.

For reference, this is the original dyno graph of the car in its prime. I sent this to the tuner to show that the graph is practically showing a similar type of curves. But his not convinced.



So who am i to believe.... getting quite conflicting reports so far.

[oldcorollas]

that second graph was done in 4th gear?
you could try to overlay them... (i just tried, and they are similar shape, but new one loses less up top)

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i worked it out that its done in 3rd gear, and the revlimit is higher (i think its 6500rpm...)