after highway pull, ecu detuning/boosting low rpm/low power on accel

[Coombsy]

Try cleaning your MAF...stock computer should be able to handle that boost level. Although if it has a nistune on it, it could have been poorly tuned.

What is your air/fuel ratio at WOT? Should be no leaner than 12.5:1

If your air fuel seems to be good, you could try pulling more timing out mechanically until your consult cable arrives.

Try turning the base timing down 5 degrees.

[Dragon Humper]

Yea...it just means the spark curve was a little aggressive. From what I have read the Nistune factory computers are still overly sensative to knock and have a total hissy when it happens. You may be able to turn down the sensativety on it right in Nistue (bonus). Ultimately though, you will need to pull some timing out, or run a gallon of Tolulene with every tank if you don't want to give up the power.

You can start weening the motor off of the C12 by adding 94 bit by bit keeping track of the amounts to see where the threshold is. If you get down to a small amount, like 5%, then little things like keeping heat in check with a 62deg thermo and not heat soaking the car too much can make it work.



Jon.

[evolution23]

Yea...it just means the spark curve was a little aggressive. From what I have read the Nistune factory computers are still overly sensative to knock and have a total hissy when it happens. You may be able to turn down the sensativety on it right in Nistue (bonus). Ultimately though, you will need to pull some timing out, or run a gallon of Tolulene with every tank if you don't want to give up the power.

You can start weening the motor off of the C12 by adding 94 bit by bit keeping track of the amounts to see where the threshold is. If you get down to a small amount, like 5%, then little things like keeping heat in check with a 62deg thermo and not heat soaking the car too much can make it work.



Jon.

What about meth injection? car runs great until im in 4th/5th and on the throttle a bit so maybe that could be a simple solution?

[Coombsy]

I think you should just solve the actual problem rather than applying expensive band-aids, lol.

Get the consult cable, fix the timing map. Also try cleaning your MAF.

Maybe whoever initially tuned the motor was running better fuel or something.

[evolution23]

I think you should just solve the actual problem rather than applying expensive band-aids, lol.

Get the consult cable, fix the timing map. Also try cleaning your MAF.

Maybe whoever initially tuned the motor was running better fuel or something.

Nah i know the shop that tuned the ecu before i bought the drive train (wont be "that guy" and name them) but they typically do sh!tty work. This was probably their way of "fixing" the issue while creating 2 problems that would need fixed a month down the road.

And where i am right now (middle of butt fcuk no where) there's no one i know of that can tune the ecu so ill probably just install a meth kit for the time being so the ecu isn't kicking out on me every time i hit the highway, and then when i move back down to Vancouver area ill get a buddy i know to hook it up to nistune and fix the mapping as i have absolutely NO idea how to actually tune..im just getting the consult cable for monitoring purposes.

As for the MAFs, they were cleaned the day before i put the car back on the road about a week ago, this issue was happening last year before i parked it and it was still happening after. So it is not a MAF issue or a misfire issue or boost leak, fuel pressure, filter, etc.. Not my first skyline so i made sure to check all the typical issues before creating this post.

Alternatively..i could install a boost controller and turn it back down to about 7psi until i head back down south. But who wants less power?? lol. But the issue will be properly fixed sometime this summer as it isn't a major concern of mine anymore now that im confident i know what the issue is and how to temporarily fix it, and how to properly fix it.

But thanks everyone for the input, it was greatly appreciated!

[Coombsy]

Then dial your ignition timing back mechanically until the problem stops. Much cheaper and easier than installing meth.

[evolution23]

Then dial your ignition timing back mechanically until the problem stops. Much cheaper and easier than installing meth.

I kinda want to run meth anyways so I'll still be installing it (part of my future build that may or may not ever happen). But I'll retard the timing a few degrees and see what happens. Still have 1/2 a tank of 98 left so it'll be a week before i do that still.

As for my AFRs, I'm seeing it only rise to 13.2 until over 5000rpm, then it'll rise to about 12.8, then slowly increase to 12.4, which was the highest reading I saw before letting off. Would probably rise a little more but I ran out of road, this is with 98 in the tank so no knock. Will have to wait until next week to do anything with just 94 in the tank again.

[Coombsy]

Should definitely be running richer than that at full throttle...that's part of your detonation problem. Most of the problem is probably in the timing map though.

[evolution23]

Should definitely be running richer than that at full throttle...that's part of your detonation problem. Most of the problem is probably in the timing map though.

Hmm well when I head down south I'll have it all fully retuned. But for now I'll fiddle with the timing and see about meth.

[Skym]

Alright so.

ran 2 gallons of C12 (108 octane) with 30 Litres of Chevron 94..if my math is correct thats approximately 98 octane. Then did a highway run (of course on a closed road) and the car pulled at 11psi all the way through, and again, and again. Did NOT pull my timing or kick the ecu out, and it runs damn amazing.

My theory...

When the previous owner removed the boost restriction, the fuel mapping was not adjusted for the extra boost, thus causing the car to run a little lean from 7psi ~ 12psi causing (detonation?) knock which my ecu then goes in to limp mode and retards my timing.

Does that sound like my issue? Simply needs retuned for the added boost?

Yes. The lean A/F ratio wouldn't have helped. The higher octane fuel has a higher resistance to knock, but depending on how lean the Air/Fuel ratio is, timing to suit, it doesn't stop the engine knocking when run a engine very lean, even with stock ignition timing.