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Car not revving past 4000 rpm

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Hello all. I have just started the course here and I need some help. I've just completed a build on MY11 JDM Sti Ts and can't get it to rev past 4000 rpm.


Ej207 Block bored to 93mm

Manley H-TUFF Rods

JE asymmetrical pistons

Gsc S2 Cams

Ferrea +1mm valves

Ported Heads

Garrett GT3582 Gen 2 Turbo

Tial 44mm Wastegate

What could be the possible cause of my current issue?

Not enough fuel, not enough air, or the spark is happening at wrong time. Those are the only things that can prevent the engine from accelerating to a higher speed (other than too much load).

Do you have a good crank trigger signal? (use an oscilloscope, or feature within your ECU to verify)

Have you verified the ignition timing with a timing light (make a mark on the flywheel or crank pulley if necessary).

What is the manifold pressure at 4000 RPM? (ie. is there enough air)

What does the wideband Lambda read before it stops reving? (lean conditions could indicate insufficient fuel system capacity - clogged filter?, bad fuel pump, etc)

Does the fuel pressure remain steady? (preferably it would track the manifold pressure)

Thanks for your reply. I have done a few logs with Romraider so I can post those if you wish.

Crank signal is good.

Wideband is at 14.7 before it stops revving.

Fuel pressure is steady.

Another place to start is by asking what you have changed in the calibration to date? It's safe to assume that it revved normally to start with? So what changes did you make to get to a point where you now have this issue. This is why it's so important to start by saving a copy of your stock ROM file so you can revert to that if you strike major issues. It's possible that it is a mechanical issue too but I'd start with the basics. It's quite unusual for a mechanical issue to cause a specific rpm cut out.

14.7 @ 4000rpm seams lean to me. Try adding fuel around 13.5:1

first I must say thanks for the replies guys,,, let me also say I'm not the tuner on my car,,, because I'm now learning,, they're a few issues I've realized

1) the car starts very good from cold and idles at 1200rpm for about 10mins, turns off

2) the car wouldn't start again not till after about 30-45mins after tuning it off from the first start.

3) A log was done and I notice the left intake cam at 10 degrees when idling and the right exhaust cam at 3degs ,,, but when the revs reach about 3800rpm these same cams begins to retard in numbers.

I also have another jdm sti 2.5,,, I did a log on that and find that all the cams were at 0deg at idle,,,, but when the car revs the cams begin to advance,,,

Question I would also ask is if these gsc s2 272 (usdm) cams would work on my JDM ported HEADS??????

What also happens is while the engine struggles to rev under the 4000 ranch it throws a check light code that says 3 and 4 cylinders misfires, these 2 cyl plugs also shows signs of lean mixtures,,,, while 1 and 2 cyl plugs show signs of been black smutty (rich).

Through all these issues the fuel pressure remains at 43psi

The motor is on the stock ECU,,, stock 565 injectors, map sensor, also the 4inch maf tube with stock maf sensor fitted to the gtx3582r gen2 turbo, Vp, ms109 fuel

I'm hoping to use a after market ecu when get the motor running great,,, (syvecs or Emtron) wish I could've use Cobb

This is the latest log of the car so you guys can see what is happening.

Attached Files

Not familiar with the Subarus but Im not seeing the afrs move from stoichiometric. Since you are running OEM ecu, it may be kicking you into limp mode of some sort due to a missing input. Can you pull dtcs?

Furthermore, seems like your coolant temp is rising beyond normal.

Is the tuner looking at the MAF voltages at all? in your log it's flat lined at 0 volts and intake air temp is at -40.

It's as though the MAF is unplugged

Hello again everyone,

Just want to report that I've found the problem why the motor wasn't revving pass 4000rpm

It was the crank gear, a tooth got broken out on the side where the crank sensor would pick up 3 and 4 cyl,,, hence that's why it misfires on those 2 cylinders

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