High RPM engine cut out

[bbenny]

Hey im looking for some advice

Last night i installed a HKS2530 with 3" dump on my R32.

The turbo works a treat it pulls so much harder than the standard but i find at around 6,000rpm the engine cuts out completely.

it really freaked me out. I am running the same boost as i was with the std turbo (1bar).

So i decided to remove the bleed valve completely. it doesnt stall anymore at high rpm, but i do find the boost tends to creep above the 0.7bar... somtimes almost to 1bar.

*note: i am running a completely std computer.

so i have a few questions:

1: would the cut out be a fuel cut or something else?

2: is boost creep normal? it never happened with the std turbo.

3: even if i run standard boost is it possible for the car to run lean? does more dense air need more fuel?

any advice/info would be great!

thanks

Ben.

[bbenny]

anyone?

[OVL-747]

im not very up to date with skyline ecu's etc , but with ur new turbo , it may reach the same psi , say 14 , as ur other one did , but the volume of air being pushed in will be far greater , due to the larger comp wheel etc etc etc.

therefore too much air , not enuf fuel , the computer might know to shut itself down before something bad happens , like i said i dont know much about skyline equipment so i am probably off track

[GTS20X]

Cuts out or dies as in no more power, could be maxing out the fuel pump, i had this happen when i fitted my front mount.

[bbenny]

yeah when it cuts out i mean it completely cuts out. like under full load its pulling really hard then all of a sudden nothing... as if i took my foot off the accelerator. it doesnt "die out" as such, it just cuts out very suddenly.

[b2barker]

Sound more like fuel cut from overboost. You are probably not running the same boost after fitting a dump pipe. ie. Less back pressure=higher exhaust speed=more boost.

The solution is to lower boost until it doesn't happen, OR get a fuel cut defender combined with refueller (AFC or piggy back) to make sure you are not leaning out up top. Maybe the TSI which does both.

[bbenny]

OVL-747... i have heard this before but get confused. i always though 14psi would be 14psi regardless of the type of turbo as pressure is pressure ie psi = pounds per square inch so regardless of what is producing that pressure it is infact the same pressure (does this make sense?)

however i do understand a bigger turbo will produce that equal pressure but the air will be much cooler. and cooler air is more dense...

so when ppl tell me that my turbo is producing the same pressure but pushing more air is that what they mean?

[OVL-747]

yes 14psi is 14psi , but there is a greater volume of air being pushed in , still at 14psi though.

its very similar to an oil pump , take and rb30 and an rb30t pump , they both have the same oil pressure , but as the turbo pump is bigger it flows that wee bit more oil , needed for turbo etc but still at the same pressure

[OVL-747]

Originally posted by bbenny

so when ppl tell me that my turbo is producing the same pressure but pushing more air is that what they mean?

yes - thats why it is extremely common to "hiflo" a turbo , basically , the larger wheels can push a larger volume of air , but it still enters at 14psi.

the more air (mixed with proper fuel setup of course) means greater combustion = more power.

but in ur case id say the computer may be sensing too much air , not enuf fuel so it cuts out intermittently.

[jnr32r]

Bbenny, I seem to be experiencing the same problem, just put in my 2535 and it does something very similar at about 1 bar it reaches full boost at ~3500rpm and then seems to bog down till it reaches ~6000rpm and then goes hard till rev limiter.

I can hear the turbo working hard but it doesnt seem to pull as hard as it should.

I boosted to 1.4 bar and when it reached ~4500 it fully cut out like when you hit speed limiter, so im tending to think it would have to be not enough fuel going in....

Might get it Dyno tuned and see how it goes maybe then get a bigger fuel pump...

[bbenny]

I dont seem to find mine ever bogging down, when it hits full boost it goes hard all the way to cut out.

well ive booked some dyno time this friday. so ill let you know how it all goes.

[BryanB]

doesn't the stock ecu cut fuel out if run more then 14.something psi boost? i dunno but it sounds like a fuel cut to me...

[rob77]

Some sort of fuel and boost cut I'd say. Stock ecu's are a pain for it. I run my td06-20g at around 12psi, because if I go higher my stock ecu will probably do a boost/fuel cut, plus my fuel system needs upgrading. But on 12psi it pulls like a bitch to the redline.