3rd, 4th, 5th gear engine cut?

[Cool Hand Luke]

I recently went for a top speed test in my car, even though it has a 180km/h speedo (In closed course test conditions only). However it has this annoying, and slightly suvere engine cut at 7500rpm in 3rd, 6000rpm in 4th, 6000rpm in 5th, which is around 220-230km/h. Is this normal, the speed cut or something? If so, i thought it would be quite gentle, and at 180km/h. Its like you turn the ignition off for around 6 or 7 secs, then fires back up. Happens the same revs in those gears each time, so it wasnt a random thing.

[Lozza150]

it's called Rev limiter...... 7200 rpm max.....that is a violent shudder

Speed Limiter:

the car should go duuh dsuuh duuh duuuh duuuh duuuhh when 180kph

more of a strong vibration shudder......

Well that's what i feel.... on the track

[R31 POWER]

Is the speed wire cut.

[Cool Hand Luke]

Dont know what the speed cut wire looks like...

I know what a rev limiter is Rev limiter is at 8000rpm on an rb20, and it doesnt change from gear to gear, also when you hit the rev limiter it doesnt shut down the engine for around 5 - 10 secs.

[Dr_Drift]

Could be maxing out the AFM and it flows more when you load it down in higher gears... how much boost are you running?

If your hitting 230 ish that's way past the factory speed cut on the ECU and i would say that either, A: whoever installed the RB20 in your 180SX didn't hook up wire 53 (Speed sensor to ECU), or B: Your ECU's been chipped and the limiter removed (if this is the case it shouldn't air flow cut)

Doc.

[Lozza150]

Just checking

it could be Boost cut...as said above......

[RB20LagWagon]

Only from reading z**m and my own experience you cant chipp out the Mass air cut, though i dont have the speed signal connected either, but i have a mines ecu which has the limiter removed.

Id go for the mass air / max afm cut.

[Cool Hand Luke]

Hmm.. when you say 230 at the wheels, KW or HP? It wont be puttting out 230kw, at the moment i have these mods:

RB25 turbo @ 14psi

3" turbo back exhaust, with seperate dump

PWR FMIC

Pod Filter mounted behind front bumper

Stock un-chipped ecu

Stock afm, just taken rear mesh off but did it before that came off

It has also happened in 2nd gear, when i was doing a burnout up a hill, it was revving between 7500-8000rpm and was pinned for a 10 secs or so, its pretty dangerous because the engine just shuts down for around 5-10secs then takes off again. Also my BOV leaks around 1bar, not sure if this would cause a problem but im going to get another one.

[Guest Theone]

Sounds like fuel cut to me.

Check that u r not overboosting. It could be a faulty wastegate actuator/solenoid.

Get it sorted or u'll bend yr rods !

[Dr_Drift]

Originally posted by Cool Hand Luke

Hmm.. when you say 230 at the wheels, KW or HP?

I was actually refering to your speed.... If you can go past 190 km/h (some 180 speed cuts are a little off) then either your speed sensor wire #53 is not hooked up, or it's chipped.

[Cool Hand Luke]

If i ran a diagnostics wouldnt it say if wire 53 was not hooked up? If it isnt hooked up what will it do? Also if the AFM is maxing out, why? I was told it would be good to a bit over 200rwkw, and cant see that my car would be making that much power. Ive been curious if it had been chipped before, because i have problems with detonation at 5700-6500rpm, but if i run octane boost it is fine. Just guessing that it was mapped for japanese fuel, not ours.

[Dr_Drift]

Luke,

53 won't come up in diagnostics, RB20 AFM can max out around 170 rwkw, does it happen more on colder nights ?? Open the ECU and post a photo....

Doc.

[Cool Hand Luke]

Do you mean take the kick panel off and take a photo, or take the ecu apart and take a photo of its insides? As for the cut, i guess so. But it will cut out in 3-5th gears any time.. Ive only reached 6000rpm in 4th and 5th at night, and ive only had the car for a few months so its always been cold. But it has cut out in 2nd early morning last week.

[Dr_Drift]

Luke, take a photo of inside the ecu, all you need to do is unscrew the top plate with 4 screws.

If you hit it in second it may be air flow cut....