BLOZ UP Posted May 26, 2012 Share Posted May 26, 2012 I went to the dyno earlier this year and made 240hp at 18psi. Dyno guy swore he heard lots of detonation. I think he's BSing because I have, what I think, is really conservative timing. I gave him the benefit of the doubt since he's been doing this for a while and has worked with a lot of Zs. I pulled a couple degrees in the high load areas. The car would also not rev more than 5200 rpms on the dyno. Can't say if it does that on the road, haven't been watching the tach while flooring it. Anyway, so I finally got some time today and did a compression test. Got it warmed up (actually I went out and beat on it on low boost), opened the throttle and let it churn for about 3 compresses (judging from compression tester jerks) on each cylinder. I did some cylinders twice to confirm. What I saw surprised me: 157 170 (first time was 175) 155 167 160 175 (first time was 175) I get single digit MPG. I make zero power. It reaches ~75% DC on my 550cc injectors on low boost (170hp). It smokes a lot--mostly on decel (oil burning, valve/valve seals?) I don't see or hear any massive boost leaks--because it would have to be massive to vent 200HP worth of air, right? The last test I did was eons ago, before the motor swap I believe, it was about 140 each cylinder and then one was 90. Can't say if I did it at WOT or even warmed it up. Too long ago. So what gives? Will really retarded timing lose that much power? I don't see how valve seals can vent that much. I ask because I have a JY engine of unknown condition (in true Z31 style), so not sure if it's worth the hassle of swapping it in if I can just replace valve seals/increase timing/whatever. Here's the timing I ran on the dyno. 18psi = 230kpa 12psi = 180kpa 9psi = 160kpa I also may have a very restrictive exhaust. I have a resonator that Summit advertised as "straight-thru" but it is actually a chambered POS. 1.5" or so tubes within it that it has to navigate through. I have some Vibrant replacements. Not sure how that results in 200hp less though. Not sure why I posted in the Newb forum either. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted May 28, 2012 Share Posted May 28, 2012 Most likely not blown up, a leakdown would be irrefutable that it's not blown up. Your timing looks somewhat conservative, but I'm not familiar with VG's. Quote Link to comment Share on other sites More sharing options...
johnc Posted May 28, 2012 Share Posted May 28, 2012 Dyno guy swore he heard lots of detonation. I think he's BSing Why would you think that? What benefit does he gain by lying? I can think of a lot of benefits to him from telling you the truth. I get single digit MPG. I make zero power. It reaches ~75% DC on my 550cc injectors on low boost (170hp). It smokes a lot--mostly on decel (oil burning, valve/valve seals?) I don't see or hear any massive boost leaks--because it would have to be massive to vent 200HP worth of air, right? After reading this I tend to believe what the dyno operator said. Sounds like your tune needs a lot of work. Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted May 28, 2012 Author Share Posted May 28, 2012 Why would you think that? What benefit does he gain by lying? I can think of a lot of benefits to him from telling you the truth. Because there are so many rattles at various RPMs, he'd have to be pretty good to single out engine detonation. After reading this I tend to believe what the dyno operator said. Sounds like your tune needs a lot of work. That's very true. But I made sure that the tune was rich and retarded. The graphs from my datalog and the dyno confirm that it was 11.5 or richer. Quote Link to comment Share on other sites More sharing options...
johnc Posted May 28, 2012 Share Posted May 28, 2012 You can get detonation even with a rich mixture. Low fuel octane, hot spot in the combustion chamber, etc. Retarded ignition timing tends to heat up the combustion chamber. Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted May 28, 2012 Author Share Posted May 28, 2012 Huh. I did not know that. I'll definitely work on the tune. I've already made the < 100 kPa areas nearly identical to what the stock ECU has. One likely contributor to my problems is that my 1 year old fuel pump just died the other day. I suspected it earlier but my fuel pressure never dropped, until now. But if it has been on it's way... Quote Link to comment Share on other sites More sharing options...
Chemicalblue Posted May 29, 2012 Share Posted May 29, 2012 Because there are so many rattles at various RPMs, he'd have to be pretty good to single out engine detonation. It was detonating louder than the rattles. Plus the detonation doesn't sound like a rattle, its very distinct. They don't fly Brice all over the world to tune race cars because hes just "ok" at tuning, take some advise from the guy. Id do a leak down so you know where you stand. If you need some help making pulls let me know. Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted June 4, 2012 Author Share Posted June 4, 2012 Because there are so many rattles at various RPMs, he'd have to be pretty good to single out engine detonation. It was detonating louder than the rattles. Plus the detonation doesn't sound like a rattle, its very distinct. They don't fly Brice all over the world to tune race cars because hes just "ok" at tuning, take some advise from the guy. Id do a leak down so you know where you stand. If you need some help making pulls let me know. Alright, alright. I'm going to need to put it on a dyno to tune cell by cell shortly. Quote Link to comment Share on other sites More sharing options...
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