Guest szlash280z Posted January 21, 2004 Share Posted January 21, 2004 Ok, I was running my car at 10PSI, no intercooler installed, air temp was around 50*F or less. My friend and I were in the car driving it to lunch, and on a long stretch of cop free road I punch it. I am revving it full bore as if I was at the track, when the boost was coming on I hear the slight rattling sound from the engine bay. It has been doing that for a while now, but I thought it was something external, or my shitty re-rebuilt turbo clanking because of all the torque and vibration. So I am around 5000 RPM in 5th and still gunning it when it dawns on me that the rattling is probably not good, it was probably detonation! So I back off at 135ish indicated MPH (my tires are stock size and my speedo is cogged correctly with my 3.90 rear, verified previously by the Jacksonville Sherrifs department at around 75 indicated and 75 on the radar, thank you officer.) Anyway, the rattling wasn't loud like I had imagined detonation should sound like. So I miss diagnosed it. when we get to the restaraunt I have my buddy get out and tell me if we were smoking on decel. Yup. Not as much as when the turbo went out before though. I drove it home with the boost controller removed, and guess what? Yup, no rattling sound at all at 6psi. So it was detonation. I tested my compression and it was at around 110 to 120 on all cylinders. I don't have leakdown equipment. I probably damaged my rings slightly. Oh well, the rings were probably crap to begin with so I'll drive it around anyway. When I take out the engine this time to fix that, I will be able to fix my radiator support that is all rusty and paint my engine bay. So good comes from bad! the car still runs great, so I might not have done much damage. Maybe the injectors I got were not TURBO injectors? It should have been able to run at 10 PSI especially with the air temp being that low. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted January 21, 2004 Share Posted January 21, 2004 Detonation can occur even if there is enough fuel delivered. If you are forcing too much mixture in, you can get detonation if you dont have sufficient octane or timing. Also, detonation isnt always loud. Additionally, I dont see how ambient temp would make much of a difference. Even if it was the difference between 80 and 50, that is only 30 degrees. While that seems like a lot, when you are dealing with forced induction, it really is only a small percentage of possible temps. Quote Link to comment Share on other sites More sharing options...
Guest szlash280z Posted January 21, 2004 Share Posted January 21, 2004 I agree with that. Maybe I was running too much initial advance? how much would that affect it? it could have been as much as 30* initial advance. the 83ECCS calls for 24*, and I set it around there but it was hard to read. Should I retard the initial timing a bit? Quote Link to comment Share on other sites More sharing options...
Jersey Posted January 21, 2004 Share Posted January 21, 2004 You should have been able to run 10 like you said without detonation. I'm not sure what your setup is but, i would make sure your boost gauge is correct and also find out what's happening to your fuel pressure in boost situations. Hopefully the injectors are fine. Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted January 21, 2004 Share Posted January 21, 2004 I wouldnt go adjusting the timing just yet. Normally the problem you are having comes from the fuel igniting before the spark fires. That is not a problem of being too advanced. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted January 21, 2004 Share Posted January 21, 2004 That's why I wont stay on the boost for very long... 10psi is a lot to run w/o an intercooler, and if you're setup is near stock, I have noticed a pattern, on my own and other mostly stock zxt motors that I've seen dynoed, that above 5000rpm the stock zxt fuel system starts to lean out pretty dramatically... at about 13:1 A/F ratio at 5000, which most people will tell you, is to lean for running boost (optimum is considered to be about 12:1). This is usually attributed to the weak stock fuel pump, which was never designed to supply 10psi @ 5000rpm worth of fuel. Also the intake air is just getting way too hot if you're on it that long, regardless of ambient temp. If you're just running the 1/4, something real short like that, it should be fine. However, I had asked a long time ago about the possible issues of doing a 'top speed run', flooring it for a long period of time, w/o an I/C, and was basically advised, don't do it and I think the general consensus was not to hold WOT w/o an I/C for more than 15 seconds or so. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted January 21, 2004 Share Posted January 21, 2004 If you're using a stock turbo, tou're asking for trouble w/o an intercooler. A T3/T4 will lower the temp a good bit - my '83 has hit 15psi (weather chabge w/manual boost controller) w/no sign of detonation. Of course the cooler air temp helped here... Quote Link to comment Share on other sites More sharing options...
fl327 Posted January 22, 2004 Share Posted January 22, 2004 I think you should pull the timing back some. What are spark plug gaps at? 10psi is doable on factory fuel, but you have to adjust it some. Before the fmic i was running 9psi on factory fuel, and it ran good and mean like that. I would check out fuel system too, fuel pump and all that jazz. I would doublecheck the fuel injectors as well. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted January 22, 2004 Share Posted January 22, 2004 I always got away with 9 psi without an intercooler with no issue, 10 was asking for trouble. I would make sure I had a better fuel pump in there, and you should probably be using a rising rate FPR at that point as well. Also, you do know if you have any oil getting into the combustion chamber, that can cause detonation, and using fuel injector cleaner will also lower your octance. So be careful. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted January 22, 2004 Share Posted January 22, 2004 I read somewhere that a common rule of thumb is that any time you go raising boost over the factory setting, you're supposed to retard the timing 2 degrees for every 1psi of boost increase, so going by that you should back your timing down to 18* BTDC. That seems a little excessive to me, will make around town driving suck, but the moral is that if you are raising boost (and 3 psi is a lot for no I/C and stock EFI) that you definately SHOULD back the timing down a bit. I run mine at 18* but my motor calls for 20*, not for 24* (it's an 81 motor) and I do run 10psi and have never heard it ping, nor have any signs of ping, even when I dynoed it on a warm day (pinging shows up on a dyno as a very erratic hp and torque line), and figure if it's gonna ping a dyno would be the place it would do it since it puts a lot of load on the engine and there is much less cool air blowing past it since you're not moving. Back it off 2-4* and see what happens. Quote Link to comment Share on other sites More sharing options...
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