Question about my dyno graph (4AGTE)

[Pure-SX]

Chatting with gunmetal about clutches. We got to talking about my ae92 levin with a 4agte. I have owned the car for like 2-3 weeks now. Having a look at the dyno sheet gunmetal raised a few questions.

Why is the power falling off so badly after 6500 ?
Also why does the boost not sit flat at the set point like it climbs from say like 16 to 18 PSI over the 5000 to 8000 rpm rev range I suspect that if you were getting the 20 psi at 6500 you might get another 20 kw ?
Possible restrictions?

Specs and dyno sheet as follows:

Engine:
Ae101 4AGZE Block
40 Thou Overbore
P.A.R. Conrods
Ae101 LSD Close Ratio Gearbox (E58-11c)
Wiseco 8:0:1 Low Compression Pistons
TRD Piston Rings
Lightened and Counter-Balanced 4AGZE crank
Custom 4puck Ceramic Clutch
ARP Conrod and Head Studs
Cometic MLS Head Gasket
Ported and Polished 4age Head
HKS Valve Springs
HKS 264 Cams
Ferrera Valves
Precision SC50 450HP Dual Ball Bearing Turbo (T3/T4 hybrid)
Tial 38mm Waste-gate
Tial Blow Off Valve
3inch Custom Exhaust
3inch Yum-Cha Cannon
High Mount Manifold (HPC Coated)
Custom 3 inch Dump Pipe (HPC Coated, Heat Wrapped)
600x300x78 Front Mount Intercooler (2.5" from IC to throttle, 2" from turbo outlet to IC)
Pod Filter
680cc Injectors
M&W Digital Ignition
Haltech E8 ECU
Toyota 1JZ Coilpacks
Walbro 550HP Fuel Pump

On BP 98 Pump Fuel at 20psi.. no timing advance and conservative tune made 205kw at the front wheels.

Any ideas as to anything?

Sorry for image size, had to resize it alot smaller to fit in, and couldnt upload to photobucket.

P.S Driving the car it makes 20psi at about 5000rpm and carrys it all the way to the redline(8300 rpm) I also do not have a flow curve for the turbo.

Any help / suggestions would be greatly appreciated.

[GUN METAL]

cmon guys can someone give him a hand hahahaha


Have you been able to get a pressure curve for your turbo ?

As i said i know jack shyte about turbos.

But comparing these curves may give some ideas, i hope Shane doesnt mind and i am sure he could offer some suggestions

One of his curves from the 4A dyno thread



What i am guessing from yours is that its quite a bit larger turbo than this one and something is seriously going on with the power drop off so quickly


Shane can you confirm the gearing or the equivilant RPM on this curve please

[legend]

u can see that it starts at 5000 rpm peaks at 6500 maybe plugs leads or fuel

[abently]

You need more cam.... and a better tune. If you need an explanation justifying why, just say the word and I'll put up an explanation over the weekend if no one else does so before-hand.

[Pure-SX]

I don't see why I would need bigger cams, I remember the previous owner saying about a little fuel dump up higher in the rev ranges. Can you explain why the car needs more cam.

When I get back home I will be taking it to my mechanic/tuner to chat about a few things.

[oldcorollas]

better tune for sure, but i would be interested to know why you think it needs more cam.. when it is only finally hitting boost at 4800..

to me it seems the shape of the graph shows you have a "problem" as opposed to a "non-ideal mechanical setup"...

what plugs/gaps are you running/
what do you mean "no timing advance"? do you mean no timing retard? in which case the top end (after the weird peak) could be detonating?

[Pure-SX]

To be honest not sure which plugs are being used. Also with the timing I believe it to be just set to 0.

Just after a few possibilities and a few things to talk to my tuner about.

P.S I am not 100% familiar with the car as I have only had it for about 2 weeks.

Will hopefully be getting it on the dyno up here and checked out and a possible slight retune

[GUN METAL]

abently i would like to see the explantion as well please.

I really cant see more cam helping either.

To me something very strange is going on the boost is fairly stable and its reving over 8k

wheel/ clutch slip on the dyno ? something strange with fuelling ????

I dont know i have never seen a curve like it.

[Pure-SX]

I would guess the power should continue straight up and not dip, unless as gunmetal said the clutch or wheels are slipping or there is a fuel dump of sorts.

Previous owner said that there is a fuel dump up high just to make things safer.

[abently]

Get the car tuned to 30psi. May cost an extra hour of tuning but will also save your Engine if boost over-shoots one day for no reason. Secondly if Boost doesn't taper off down to 25psi or lower by 7500rpm then you need more cam or cam gears.

And no it is not going to ping with a 8.1 CR... but any competent Tuner should also be listening for Knock electronically.

[Pure-SX]

Sorry to ask the question, but why would boost taper off?

And by more cam do you mean bigger cams or more timing?

[big_zop]

Because of a limit in flow - he would appear to be suggesting cams but can also come from a number of other resctrictions (or multiples of) such as head flow, inlet/exhaust manifold and wastegate design (effective scavenge of all runners, no sharp bends, separated from main exhaust a decent distance?), intercooler, exhaust, turbo compressor/turbine efficiency.

Increasing boost through the rev range is most likely due to an incorrectly sized (ie - too small) wastegate but graphs i have seen arent as gradual as yours.

If the clutch was slipping, woulnt the load on the engine be reduced enough to reduce the boost generated?

There does appear to be a lot of isses once the engine is on boost and again could be a number of things. The list of your parts utilised would not appear to show any glaring hole so may not be obvious or easy to find - so i would be skeptical to blame them but there is the potential that something is wrong. It could be that the spark is being blown out - you havent mentiond the gaps being run. Or the alternator not able to keep up with the demand. What were the AFRs like?

I would probably start at the tune first, look at how much time has been spent on that area as you should at least have a smooth curve and the consistent dops above 6500 seem to suggest more than wheelspin.

[Pure-SX]

Will be going into my tuner on Saturday to have a chat with him, will let everyone know what transpires.

The only stand out restriction I can see is the intercooler pipe between the turbo outlet and the IC is only 2".

[-GT-]

I'm with OC, timing, plug gaps, tune... it doesn't need more cam, plenty of stock cam'd 4A's are able to hold boost all the way up. Also, why does your highest boost plot (I'm assuming that's boost?) fluctuate so much up top?? I'd be looking into that too.

When you say you think the timing is just set to 0, do you mean the dizzy advance? Set base timing correctly, and check tune on a dyno. Also look into your plug type and gaps, you're running a fair bit of boost - what ignition system are you running, factory? I don't know how capable they are, have a look around at similar setups and see what they're running.

And get efficiency maps for your turbo, find out where it is operating.

[big_zop]

Diameter of the pipe isnt everything, its the transitions (at pipe joins, welds and changes in diameter) curves and diameter of them, inside finish of the pipe. These make a much bigger difference than the actual diameter itself.

And with a small engine/turbo combo may be more than enough. And its also worth to note that smaller pipes lead to higher velocities so may help with response (probably not measurable in all but extreme cases - say 4in vs 2in)