Ben, what intercooler are you running on your setup?

 

I think he's running the SAAB

 

Saab 900. It's small compared to what I see on others' cars. Probably adds a little more intercooler lag too.

Oh, I'm running an MSD Sebring to pull timing. It pulls a max of 6°.

 

If you're not running massive boost and aggressive timing a Saab 900 IC should be just fine. Have you seen the size of a stock WRX intercooler? Yeah, and it's running 13.7 psi. I have a Saab 900 intercooler and I'm pretty sure it'll be just fine for my purposes.

 

So, you fellas with Bipes units: what RPM map do you use? I'm using the 2500-3800 RPM map, but I think I'll try the 3000-4000 RPM map.

 

I'm not running massive boost (figure no more than 10.5 tops, incl i/c loss). I'm not running agressive timing (13° pulling 6). And it wasn't hot out. I had detonation on 93.

I have not had detonation under "normal" driving conditions; I had to red line 1,2,3. It's possible I guess that my car doesn't like the Shell gas from the last fill up. I usually get Amaco, but the Shell was convienent.

 

Or are you running out of fuel?

 

more fuel isnt always the answer high egts are indicative of fuel burning in the exhaust tract not in the combustion chamber, lean mixtures dont skyrocket egts like you would think rich ones do.

 

Don't think so because I can wind out 3 without detonation. It's when I go 1-2-3 that it happens. Might have been a fluke, I haven't repeated the test. The math shows that my injectors have enough flow potential (but it's close) and I've got a 190 lph hp feeding them. AFR shows rich.

Dunno. EMU or MS with 560s is on the horizon.

Ben

 

Actually, I'd say that's fairly aggressive timing. You're running only three degrees less advance than a stock car, while forcing over 60% more air in the car than stock.

If it happens after a run up through a few gears, but not while winding out merely one gear, than your on the ragged edge of audible detonation (you may be getting some inaudible detonation even in the one-gear-pulls), and the intercooler is getting heat-soaked to the point of audible detonation on the longer pulls.

That's a timing issue.

 

Winding out 1st (if you can really call it that) and 2nd are pretty different than going all the way in 3rd. You are in boost a lot longer. I suspect that your intake temps are simply getting too high, and your IC wasn't keeping up maybe. Pull more timing.

Either that or you have a fuel delivery issue. Maybe the pump is running out of steam when you run high boost for a prolonged amount of time. Do you have a fuel pressure gauge in the car?

Jay

 

So, to follow-up:

I had actually been running more timing retard than I remembered. I have a base of 12�° pulling 8° in the 2500-3800 RPM range. A bit much for the 7-8psi I've been running, maybe, but it had been working fine that way for some time.

So I experimented this weekend with pulling only 5°, and was met with a decent amount of pinging once the full 8psi was attained. Even at 6°, there's still a touch of ping if it overshoots and hits a little over 8psi. So, at the 7.0-8.0psi level, it would seem 6° is running very close to detonation, and may even have some inaudible detonation.

Granted, this is with a relatively small MX-6/Probe intercooler, but it's bigger than the Saab (probably roughly similar to the 2nd-gen RX-7 intercooler), so I have no idea how Ben, for example, is running 9psi through a Saab intercooler and pulling only 6-7° from a base of 13°; I would think you'd be getting some pretty good ping.

And, Magna, even with your water injection setup, I would think you'd be getting at least some inaudible ping, what with no timing being pulled and no A/A intercooler, at 12psi of boost. You've gotta be on the ragged edge.

 

I don't have any problems if I wind out 3 from a roll to rev limiter. No detonation. So I don't think I have a fuel delivery issue. It's a walbro 190 hp, so it should have headroom. I would say it's more likely heat soak.

For grins n giggles, I could snap in my super cool MAC fuel injection pressure set (it literaly pops in) and go for a ride.

 

From looking at your mods, I'd suspect your car at 7-8 psi makes more power than mine at 9 psi.