Rb25det Cut Off

[Bronx]

hey, just wondering what kind of fuel cut off the NEO enigne uses? does it stop the fuel pump or does it stop the injectors when overboosting or the so called "fuel cut"

if im using the 2 stage solenoid, my engine goes alright till about 4,5k rpm, after that the full boost kicks in and it just makes loud popping noises, and stops accelerating. now if i bypass the 2 stage solenoid by just removing it and connecting the pipes together, full boost kicks in at about 3k rpm and the loud popping noise kicks in there.

but as soon as i get to about 5,5-6k rpm i get full boost again and the car just flies till it hits the limiter.

now i havent had time to do the trick with grounding the fuel pump continually to supply the full 12v, but apparently that fixes it.

so just wondering if the fuel pump stops pumping, the injectors stop or if, like the supra, it stops the spark plugs from firing.

what would get around this? im looking at either getting a nistune or buying a power fc.

guessing the power fc will remove of it, but will the nistune?

cheers

Jean

[mad082]

so you are only running stock boost levels? what other mods do you have?

if it is stock boost and the rest of the car is pretty stock then it doesn't sound like you are hitting any sort of boost cut (as it generally doesn't result in a missfire in the skylines). it sounds more like either your coils are stuffed, or your spark plugs are, or both.

how old are the spark plugs, and do you know what type, gap and heat range they are?

[Bronx]

whole car is stock, everything is brand new dont know the exact gap, i think it was .8mm not too sure, only other thing i have is a 3" dump and catback system.

its the engine in the s2 stagea, but same ecu etc.

actually the above is true, but only at certain times, i can go past those revs perfectly if i only use 3/4 throttle, this only happens when its hot and i use full throttle, if air outside is below 20dC and i use full throttle, it kicks in a bit later, around 5k-6k rpm.

but i dont know why it dont happen after 6krpm? after that i can kick it as hard as i want, no misfiring nothing.

[Bronx]

oh yes, and also to mention, this may be really weird, but at full throttle i can rev all the way through if im not in gear but in neutral. so just parked, and gearstick isnt in gear, i can put foot to floor and no stuttering, just perfect revs and boost. kinda weird??? some other cars i know have had that too

[mad082]

reving in neutral is totally different to reving in gear while moving. the mapping used by the ecu is different for starters.

so are the coils brand new as well as the spark plugs?

[Bronx]

coils and sparks are about 6000km old.

this is really upsetting me, the frustrations!!!

[LeCoq]

change ur spark plugs and re gap it to a certain mm , ask the guy that sells the spark plugs

[Bronx]

i shall get it all done tomorrow, see if my mate has a 2nd set of coils for me to try out too

[Bronx]

fixed the problem, the dealer said they changed the sparkies, but they didnt, they are burned through to the sh*thouse, so changed them with some NGK's and daaaaaaaaamn, car is very very fast now.

but coils are still newish, so drew the lucky straw

[Galois]

Or just put the wrong plugs in. Glad it worked out mate, misfire absolutely suck!

[Bronx]

nah, they didnt change the plugs, they had holes fired into the bottom. they were really used out. luckily it all got fixed, i got some iridium IX and i was done with it. if i could have had extra time i would have loved to check out pulseplugs though. 130 bucks for all 6. wonder how they would go

[Galois]

There are horrific stories on here of people using a plug that was too hot and it looks burnt out and destroyed after a few hundred km. One guy melted his after one flat out tin to 180km/h.

A lot of sau users use coppers because

1 They're cheap

2 Changing every 5000km means that they're constantly fresh and being inspected

3 There are HEAPS of stories of iridiums lasting only 3000km

4 Copper has a slightly better spark but also wears more quickly (hence the high change rates)

I use bosch plats myself and change every ~5000km, or a bit after. 6 for $38 for 1.1 gapped, and $44 for 0.8 gapped.

[Bronx]

well, for the iridium, i didnt actually pay anything, the mechanic that had them is a really good friend of mine so he gave them to me. but daaaaaamn, gotta drive carefully.

so i guess after about 5000km ill change to pulseplugs to see what they are like.

[Galois]

Sorry mate, I just re-read my post, should have mentioned there are also plenty of people who get 40000-100000km out of iridiums. Luck of the draw really. A mate of mine spent weeks hunting a misfire on his soarer, spending hundreds replacing parts, including coilpacks, and it turned out to be the 3000km old iridiums. He was not impressed lol.

But anyways, you'll know as soon as the plugs start going off mate, it'll mis a bit at idle and high boost.

I'd keep the iridiums until they had a problem, you might be lucky

[rondofj]

hEY BRONX,

I have a similar prob on my 34GTT, I have 3inch full turbo back zorst, pod filter in custom cold air box, boost set to 12psi with manual boost controller, short shift kit and thats it. Dunno if my ECU has been programmed to handle this boost by previous owner. Anyways my issue:

My car revs sweetly all the way to 4800ish rpm ( full boost of 12psi kicks in at around 2500-3000rpm). Then from 4.8k to around 5200-5400rpm I get that sort of popping sound u talking of and no acceleration, like the car has suddenly become NA, dunno what boost it is on at this point, but theres just no feeling of boost/turbo at this band. Then from 5400 to 6800rpm the car REALLY flies - constant 12psi and smooth revving all the way ( it still never hits the 7000rpm redline but cuts off around 6800rpm???) Why dont I k\hit 7rpm?

It really bugs me as to why it ( the flat spot / NA feeling and popping ) happens on this 4.8-5.4k rpm band ONLY, do you guys recommend I do the plugs - NGK Iridiums?? I'm sure its not the coil packs.

I'm gona do a proper FMIC and NIstune next year though.

cheers RON

[rondofj]

And yeah as you said, in neutral, it revs freely to 6800rpm without the strange popping / interferrence, but I guess the ECU maps are different in neutral as opposed to in-gear.

[Bronx]

like advised before, check your sparks, thats my best guess even if your car seems to go a bit past the 12psi, i think facotry max was 15psi? it can still get blowout. found the best gap for that amount of psi is .8mm.

check it out and post back, or if your sparks are fine and set correctly, it could be your fuel pump not being able to deliver at that high boost and rpm.

if you need any help, im in sydney so i can help you with anything you need

cheers

Jean

[mad082]

won't be fuel pump otherwise it would get worse above 5400rpm.

the popping/flat spot can be caused by 2 things. 1 will be weak coils or spark plugs. also about that rpm (4500) the VCT changes over. this can cause a bit of a flat spot

[Bronx]

woops, yeah, forgot to mention the coils. didnt know the VCT kicks in at 4500... cool, one more thing to add tot he knowledge list

[mad082]

pretty sure it actually turns off at 4500rpm. it turns on at 1500rpm. or is it the other way round? i can't remember