jonboyb

Long story short...my 1.5 GTE swapped car with a PT76 got a little lean dynoing on 550's above 14-15 psi (dual Wabros and about 45 psi static fuel pressure). PO put in an upgraded fuel rail and 95 lb injectors but the piggyback systems (Apexi Neo, BCC, etc) just can't handle injectors that big. Once you hit 12+ psi it would just go pig rich (10:1 and richer) and studder. Not violent at at, more of an unusal sound and flat power. No bucking, etc.

Anyways...fast forward to now. Put in some 75's and brought the AFR's back in to a leaner (but still plenty safe 11:1 range) but still have the same studder. I've never attempted a pull until the car has had PLENTY of time to warm up, but today a buddy wanted a ride and as soon as I felt the temps were sufficient I hit it. It blew my mind! Third gear the rear tried to pass the front and it pulled super clean. Did a couple more pulls with the same results, but then after a few miles of driving and heat up time, the studder came back like normal.

Now it seems my fuel issue is actually more of a temperature issue. Of course first on my list is to switch out coils and ignitor with my 94 2JZ-GTE car, but is there something else I should be looking into. What could bring on the studder only after a full warm-up cycle??? I've felt fuel/boost cut on my 94TT....but this studder is NOWHERE near as violent. I've tried various plugs and gaps thinking I was blowing out spark.....but I don't think that's it. Any help would be greatly appreciated.

RyanV

iTrader: (9)

What was your lowest Plug gap? Maybe its dli time...

jonboyb

Tried gaps as low as .025 and plugs as cold as BPR8's. For the life of me I can't figure out why it pulls perfect until it's up to full temp and has some time to heat soak underhood (it's done it multiple times now). Plugs shouldn't do that (nor would bad coils) so I'm hoping it ties to the ignitor.

As a side note, tried a different ECU and checked the coolant temp sensor. All is well on those fronts. It's a Soarer harness so no MAS to worry about either.

Ali SC3

iTrader: (10)

running 11:1 is very rich and you may get a studder unless you beef up the ignition or close the gap.
I had a similar problem and with new plugs with a close gap took care of half of it.
the other half was reducing my fueling to the 12:1 range.
double check your air temps and see if the sensor is getting heatsoaked.

bryan767

iTrader: (6)

im experiencing the same thing, but my engine is almost stock!... i think it has something to do with a sensor..

RyanV

iTrader: (9)

Trying the other coils sounds like a good idea too!

hyjaxx

iTrader: (1)

On that setup you definitely need to be running an MSD- try a 6AL. It's not going to be your ignitor. Did you swap out Ecu's or EMS's? I don't like Alphabet soup at all- the rpm increments are crap and it's not going to give you the features you need to tune properly. But...toss an MSD in, try to lean out your map to bring it closer to a 12.0, re-swap plugs. Try a hotter heat range than the 8's you have in right now and start with a standard gap- coppers. Is your fuel press staing constant during the whole pull?

jonboyb

There's absolutely no need for a colder plug than an 8 in a 600HP JZ. We've run almost double that on JZ's and BPR8's. COld start is difficult with an 8 on my SC300.....I'm pretty sure it wouldn't happen with anything colder.

Anyways....put my 7's back in gapped .030 and threw the coils from my Supra in it.....PROBLEM SOLVED. Looks like one coil had a crack and now it runs perfectly clean. Picked up 5 psi of boost too which is not a good thing. 20 psi on pump with the PT76 is disaster waiting to happen. It's only a 38mm WG and apparently just can't regulate the PT76 (no shock there). Going to throw my spare 46mm WG on....set it to 15 psi....and call it a day.

I will say that at 20 psi, the tires were fighting a lost cause....BIG TIME Still way too rich but I'm kinda glad it was with the boost spike.

RyanV

iTrader: (9)

**** man, that's awesome news!! I need to call you.

I had a feeling it was a coil issue when you said 'gets up to temp'

...and the hairline cracks can open up the arc can cause major misfires type issues

edit- coil issues are so common that people have picked up whp just from installing a new set in 1j or 2jzgte

jonboyb

Yep....as soon as I got the clean pull before it had time to get to full temp I knew it had to be spark or a weird CLT sensor/ECU issue. GOing to insulate the coils with heat-shrink and hope I don't have to buy a set

hyjaxx

iTrader: (1)

Very naiiiice! Glad you got it fixed! I was wondering which one it was going to be!

jonboyb

I actually found a sucker to ride with me today to watch the boost and wideband for a few pulls. For all the doubters about running big turbos due to excessive lag, the PT76 builds 2-3 psi by 2200-2300, starts REALLY ramping around 3500, and the wastegate opens at 4700 when I hit 21.3 psi boost. It should be noted that the time to go from 3500-4700 rpms when the turbo really gets going is almost negligible. While yes it's certainly laggy compared to many other turbos, it's not nearly as bad as argued on other boards If I didn't have this silly 99 SC400 rear diff with uber high gearing this car would be an ultimate street sweeper. As it sits with the high gears I need the Autobahn to do a 3rd gear pull....LOL.