I am looking for opinions on how low of timing can be run on average before EGT's get dangerous. I know every setup and car is different, just looking for input. I have an IX with a BBK Full turbo and Kelford 272's, with all other bolt ons. I have posted threads in the past about all sorts of false knock but now I am coming to find out that my knock is REAL and audible. To get rid of knock sums I have to lower the timing all the way down to 1 degree at peak tq and only 7 degrees at redline(7600)!! I know that sounds crazy but the car WILLNOT take anymore, and there is no boost leaks at all and the cam timing is dead on. AFR does not seem to have a huge effect on knock sums either, Im running 11.0 right now and it still wont take more than 7 degrees up top. I have been able to up the boost to 25 and maybe more without getting anymore knock so I think I can bring my power back up with boost. Im just concerned that the timing might be to low and could cause harmful EGT's. This is all on crappy Arizona 91 octane.

Thanks!!!

 

I haven't done much tuning on pump personally, but my AMS tune was 0-1* peak load and 7-9* closer to the top... so you may not be that far off.

 

Thanks for the input

All opinions welcome!

 

You guys get the same crappy 91 that we have here in Vegas, and to be able to run 26 psi with no knock is a pretty impressive feat. FYI on my 8 turbo with a 10.5 hotside I was running 1-2 degrees at peak, rising to 7 degrees by 7500. This was on 23 psi.

 

Yeah we do, Im glad to see Im not the only one running this low of timing.

 

search around there is another thread somewhere just like this with lots of input. I remember posting in it. The answer really depends on your application. If you're just streeting the car don't go lower than 1 degree advance and you'll be fine. If you're tracking (road course) don't go lower than 5-6 degrees. If you go lower while tracking you will melt components such as turbo.

 

Who has ever melted a turbo? I would suspect in terms of EGT the only thing to worry about is just overall heat which would contribute to knock. Not heat that would contribute to melting components.

I think around 0 degrees at peak torque is normal. I can't say I've ever seen a map where the car is intended to be driven at negative timing daily.

For the past two years I run about 0-1 degree at peak torque, 2 bar, crap fuel, 35r / 2.4l. I don't feed back too much timing up top. Every engine is different though and cams I think play a big role in that. Obviously boost taper does as well if your on a stock turbo.

To give an example, I have a friend with HKS 272's, Buschur 2 litre longblock, and stock IX turbo. He runs around 1.8 bar and a lot of ignition advance. I have another friend with built 2 litre, Revolvers, and a Green and at the same boost level runs very little timing. The Green/Revolver car is a bit faster even though it runs way less timing. I think cams play a big role.

 

My car doesn't like timing either. Stock I was getting 12-13 counts of knock at pk torque (which I think is fairly normal). Now with cams, exhaust, and intake I had to pull timing down to 0-1 at peak torque, and I would still occasionally get some knock. It's mostly gone now though (I am running pretty rich at that point, usually in the low 10s since I just disabled lean spool). So we'll see how it turns out once I get the AFR sorted out.

 

Thanks guys, thats what I needed.

 

my car likes timing a lot on the lame gas we got here i really dont understand it....

i run peak @ 3/4 degrees and 14 up top with 26 down to 21 on 93 octane (could be less).

 

what do u mean dont go lower than 5-6degrees when road racing? u mean at peak torque? how would u accomplish that if u cant advance that high? i mean, when roadracing and shifting at redline i land the next gear at the 5-6 degree "cell", is that what u mean? sorry its hard to explain my question

 

Just because the timing map seems low doesn't necessarily mean that combustion peak is late of target (13-15° ATDC). Now if your octane limited, that is a different case. But think of whats going on here, your increasing the charge density signifiacantly over stock with the BBK, especially at redline - so 7° BTDC spark lead and therefore flame kernel speeds are much faster and you just might be closer to MBT than you think. Again, this is assuming there's no octane induced knock, which there probably is to some degree.

If your tuning with pump fuel there's less room to advance to MBT with a powerful AFR so you might have to add some fuel. Anyhow, if you are in fact a good degree late of MBT the exhaust valves can get too hot and cause preignition.

 

Aren't you guys a little too focused on trying to run XX boost instead of trying to figure out where the car is actually the fastest? Tune the car well at say 20 psi, 22 psi, 24 psi, etc then go to the track and do several runs at each boost pressure. You may just find that on a smaller turbo, the lower boost actually makes the car just as fast, but greatly reduces the stress on everything.


Crcain, so you wouldn't be worried about burning an exhaust valve up?

 

I still seem to get a few counts at 7000 up alot of the time, so does dropping it down to 6 at redline seem out of hand? Thanks for your input, I understand what your saying and agree.

 

I'm the last person to comment on this type of stuff.. but I just don't think there is much evidence of exhaust stream components failing. And wouldn't you get det from the exhaust valve getting so hot before it melted?

But I totally agree with 03'.. do what you can to find out if the car is actually faster or not. DLL, checking the elapsed time between two rpm points, vbox, gtech, track etc. Always good to have feedback like this when tuning especially when finding the ideal compromise between boost and timing.