R32 GTR Lean popping hesitation issues. Plaese help I'm going insane.

[needavdub]

Oh god I hope it isn't that...

[needavdub]

Actually, would that get worse as the boost was increased? Or is it based solely on RPM? Because my problem is definitely worse the higher I turn up the boost.

[Dragon Humper]

That could be easily tested, just turn down the boost to about 5psi and try it again. I wouldn't think that valve float would cause a leanout though, at least on the ex. side. 13 to 1 is getting in the pucker zone, I am in the 12.2 to 12.5 range but I always run 98+ octane fuel. 13 is an NA power benchmark, 12 is a boosted benchmark.

I am really leaning towards a fuel issue, spark snuffing would give you a rich cond. Have you checked the FPR yet? I would see if it is refferencing the boost and matching it pound for pound. The diaphram could have ruptured, you can test that really quick by pulling the vacuum hose off and putting it back on over and over, the idle should speed up and slow down as you do that.


Jon.

[Skym]

Old stock FPR can cause problems after fitting high lph fuelpumps. Saw that on a R33 GTR.

Engine should stumble at idle when FPR vacuum hose is removed as fuel pressure rises 7.1psi or so.

Can monitor fuel pressure on dyno.

[needavdub]

Well I don't have access to a dyno, would it be wise to just replace the FPR with a nismo or Tomei unit seeing as I already upgraded my pump? I've been leary to do this because I always worry about putting "adjustable" things on my car and not knowing how to set them.

[craftz]

Set adj. adjustable fpr to around 43.5psi at idle with vacuum hose diconnected. This is for rb20,someone please correct me if it's different for rb26

[Skym]

As far as I know, stock fuel pressure is around 35.5psi on RB20, RB26 and with vacuum hose removed, roughly 7.1psi higher. With vacuum hose removed, it's same fuel pressure before starting engine where there's no vacuum from engine.

From what I understand, with adjustable FPR you fit fuel pressure gauge (compound gauge?) on hose between fuel rail, fuel filter. Then adjust bolt on FPR before? starting engine to suit factory specifications (35.5psi + 7.1psi = 42.6psi) or 10psi higher (52.6psi) if want more fuel to go through injectors (remove fuel via ECU retune).

Also clogged fuelfilter could be another cause, as some rarely change that (change every 20,000km or less). Or fuel pump is mounted higher on bracket in fuel tank and starves fuel pump of fuel when fuel tank is low.

[needavdub]

Well I'm going to try to check my fuel pressure this weekend, but I'll probably buy a new fpr just for good measure. And I replaced the filter when I changed the pump 500 miles ago. So that should be good, also it does it with a full tank as well.

[speedfreak]

Maybe you should borrow another set of coils.
It's possible one of the new coils is faulty.

[needavdub]

Maybe you should borrow another set of coils.
It's possible one of the new coils is faulty.

I've thought about that, but I don't know anyone with a set to just borrow. And I sold my old ones.

[DarkCaporaL]

I'd make sure it's not a faulty coil while they are still on warranty.

[Dragon Humper]

You won't go lean with a spark issue, don't even bother to check that. You are looking at a fuel supply problem. Set your pressure at 3bar with the vacuum hose removed, 3bar is an industry standard (43.5psi). Your missing and popping is most certainly a lean miss (not enough connectivity in the spark gap to cross it) because of a lack of fuel. I was at about 14.2 to 1 with my high boost miss in my "good fuel" thread.



Jon.

[needavdub]

Well I have a Nismo Type-A adjustable FPR on the way, so once that gets here I'll install it and set the base fuel pressure at 43.5psi at idle with the vacuum line removed. I guess I'll go from there.

[needavdub]

Well I hooked up the fuel pressure testing gauge, with the stock FPR I was at 46psi at idle with the vacuum line off, it drops about 8psi when I put the vacuum line back on like it should. I taped the gauge to the windsheild and did a few pulls down the street, it jumps up to about 60psi under full boost. So I think I've eliminated fueling being an issue. I finally got around to to doing a boost leak test. And I found a pretty major one where my HKS SSQ is, the piping was leaking on both sides at the couplers and the seal between the pipe and the BOV itself was leaking pretty bad too. The previous owner just used cheap regular hose clamps so I got some heavy duty diesel truck "t clamp" style ones to replace them with as well as a new O-ring for the BOV/pipe seal. I'm really hoping this was my problem all along, I'll keep everyone posted with the results.

BTW, if you're doing a boost leak check, brake fluid bottle do the trick quite nicely for blocking off the intake piping.

[Skym]

Had it leaking at stock BOV flange on my car (leaking sound was coming from that area) due to reusing stock gasket that was crushed (seal part). Replaced with Synapse BOV that has O rings, problem solved.

Also another area to check is camcover seals. Amazing that when they are not leaking, how much better the engine feels, performs.