duowing

I've been driving my 280 lately, and for some reason it feels kinda slower than it used to be. I don't know if it actually is or not, I'm not noticing any vacuum leaks, everything seems to be in order, vacuum readings are normal. I need to go through and make sure the clamps for the J-pipe and everything are tight. A/F gauge doesn't display overly rich under full throttle. Maybe it's just that I'm realizing the L28ET is a bit slower in comparison to my 87' VG30ET?

Maybe it's time to up the timing from 20* and up the boost to 10.

NismoPick

Stock boost level? No IC? Time to update your ride.

duowing

The only update I have is the Z31 ECU/MAF swap. So you're probably right.

NismoPick

Getchoself a thick IC and electronic boost controller (or a good mbc if your are strapped for cash).

10psi makes a huge improvement over the stock ~6.5psi.

lww

What's the average temperature up there in Ohio? You'd be amazed at the difference warm ambient air has on a non-intercooled turbo car.

duowing

Lately it's been about mid-70s to mid-80s. It varies from day to day. I do remember last fall when it was starting to get cold out, how on the cold nights the car suddenly felt quicker.

snwbrderphat540

thats.... cause a stock ZX turbo is slow. lol. its shoulda felt slow from the start. pffft.... you kids!

duowing

Hmm...I wonder if my Ignition is possibly going bad? Last night when started the car, it started fine, but had a moment or so where it kinda dropped revs and such until it caught and then went back to normal. I usually never have this problem from a cold start. Only from restarting when warm, where it'll idle super low or flatout die without opening the throttle some. Although the Z31 ECU isn't throwing any codes.

JhnRX7

I have been experiencing this exact same issue with my N/A. Have you found a solution yet?

duowing

Not yet, I have a few leads on this, but it seems like no one is really sure.

duowing

Alright as far as the restarting goes, I'm leaning towards heat sink in the fuel rail. That and the fact that the check valve in my fuel pump leaks. Anyway, after doing a bunch of fuel pressure checks I've noticed that immediately after a good drive and full warm-up my pressure drops on shutoff about 2-4 psi or so. Within a few moments you can watch the pressure gauge slowly rise back to 30 psi. This is indicating that there's probably too much heat getting to the fuel and basically causing it to expand and raise the pressure.

NismoPick

Are you still using the stock rail? Unless you are just letting your car idle, hood closed, hood vents covered, no radiator fan, and it's 100+ degrees outside, it's not likely heat sink. Replace your fuel pressure reg.

lww

I think you mean heat "soak". A heat sink is a device the dissipates excess heat. Heat soak is when heat has built up enough that it affects it's performance.

hellraZor

from the reserch on the net every 11'F = 1% change in HP

duowing

actually yeah I meant heat soak. One thing I do know is even though I've done the manifold gasket, like alot of other people it doesn't seal perfectly even though I have all 6 studs and such. I ran seafoam through and got some white smoke coming up and out from the mating areas of the exhaust. I wouldn't be surprised if that contributes some extra heat.

I was posting about this on ZCar and a few people were telling me that it sounds like heat soak in the rail. Especially with the way that once the car is warmed and immediately shut off you see a pressure drop and within a few moments the pressure starts rising again. I know my fuel pressure regulator is working correctly. Followed the procedure to test it. It sounds like my Fuel Pump check valve needs to be replaced as well.