Hi everyone,
Ive got a strange set of problems that i would like some opinions on so i will explain in as much detail as possible.
My FJ20 was tuned over 2 years ago after it was built and it made 395HP at 17psi. A few weeks ago i took it back to the dyno to give it another power pull just to be sure everything was sweet. As i rocked up to the dyno, i put a new set of plugs in it just because it hadn't had plugs for 2 years. Anyway it made 394HP so everything was fine and i was satisfied.
I took it to the drags 2 weeks ago and on the first pass it felt like what was a fuel surge just before the line so i shut off and rolled over.
I was concerned that i had hurt the engine so i did 1 more pass short shifting a little earlier and still did the same MPH, this time without the fuel surge so i figured everything was ok.
Paranoid, i took it back to the dyno to do another pull to make sure everything was all alright. The first run it only made 375HP followed by 370HP on the second pull. Boost was also coming on later by about 500rpm but holding 17psi when it came on. We figured something was wrong so did a comp test straight away on the dyno which came out with all cylinders between 185-190.
Satisfied with that, Next we put a pressure tester on the front of the turbo and pressurised the system, the only thing that we could hear leaking was what was sounding like the inside of the external gate. Strange..
While the plugs were out, we inspected them which showed that 1,2,3 were fairly even, but 4 was very rich. (possible plenum design, see photo below)
Anyway, so we cleaned them and got straight into the power pull.
The first run, boost came on super late, by over 1000rpm and then went on to pull 395HP again, followed by a backup run at 391HP.
I pulled the plugs again and number 4 was definately rich still, but the power was back.
I have no idea why this has all happened and i know its a hell of a story, but if anyone has any ideas i would like to know. The only additional thing i can think of is that it was stalled backing onto the dyno and flooded, and took a while to get it started. Perhaps fouling a plug? but i dont know.
So to recap.
Boost on late - hissing noise in external gate. (turbosmart pro gate 48mm)
Power down but picked up with clean plugs.
1 rich plug - wondering if plenum design isn't very good.
Flooded before initial runs, could the plug have fouled causing lack of power?
Best pics i have of plenum
Thanks for the input,
G