| that the PRVR system wasn't hooked up properly and you aren't generating proper fuel pressure under boost. If it ran lean because of that condition it is still hard to imagine that the head gasket blew as it normally melts pistons first. The head gasket is a very uncommon failure due to running lean or detonating and it usually only seen when an engine overheats as the heads will warp up and cause the gasket to lose its compressive seal and then the gasket will fail very shortly after. For the forum: This is a copy of one of my original emails to Matt about putting together a program for his odd-sized injectors and what will be necessary in order to ensure things are right: Matt,
#2 is a base theoretical program which was mathematically adapted from a 370cc stage3+ program. #1 is the same program, but only the fuel delivery has been modified to add more fuel. #3 program has had fuel deliver modified to add less fuel than #2. You will need to take the car to a dyno with a wideband O2 sensor and make 3 pulls with chip #2. You are looking to see what the A/F ratio is doing and it should drop to around 11:1 - 11.5:1.
*If you find that the program is a little richer than you want, say 10.5:1 or lower, you should go to program #3 which will deliver less fuel and bring your A/F ratio up to around 11:1-11.5:1.
**If you find that the program is leaner than you want, say above11.5:1, you should go to program #1 which will devlier more fuel and bring the A/F ratio down to around 11:1-11.5:1.
There is enough variation between the programs to make a half-point of change in A/F. You really need to be sure that you check for any boost leaks in your intake system before you go to the dyno. You can do this by pressurizing the entire intake piping at the mass-air sensor "T" connector. There is also a device you will need to accomodate a pressurized test and there was someone on twinturbo.net selling them.. Check on the forum for one. You should not dyno before you have ensured that there are no leaks as a leak will throw your A/F ratio off considerably.
Once you get your car back together, you should thoroughly read and address any issues found from my 6 P's post on twinturbo.net.. It is in the FAQ section of the forum, here is the direct link to it:
[ http://twinturbo.net/net/viewmsg.aspx?forum=technical&msg_id=81399 ]
The program #2 was mathematically derived based on the injector flowrate of 450cc and running 11:1 A/F. This process produces results to within about 0.5 A/F. The 6 P's post details various tests such as a fuel pressure test, which might be the cause of your existing problem but that could be hard to determine now. If you can still run the car, put a fuel pressure guage on it to test what it is running. If you can't run the car, get a detailed diagram of the PRVR system and thoroughly inspect the hoses and connections to it. If there is a problem there, it will run very lean under boost. Here is a followup email:
I got the chance to drive the car hard today for the first time with the new chip! and it works great .. it pulls very hard, no audible detonation (I think I am boosting around 12psi, Greg Dupree put the boost jets for me, no after market boost gauge yet)
The car is extreemyl smooth at idle, I can't tell if the car is running or not, even if I put my hand on the shift knob .. ideling is smooth with no shaking what so ever. If the injector value is lean, it will not run smoothly at idle or while cruising. It will run smoothly and idle smoothly if it is running somewhat rich. It sounds to me that it wasn't until you began raising the boost that the problems manifest themself. If we put the idea out of the picture that it overheated and the head gasket was as a result of running lean, it wouldn't have been running as well as it was before boosting. In this case it appears to me like you dont have adequate fuel pressure and it was running lean on the top. And then this was a following email.. I wanted to give you some updates on the chip. I wont be able to Dyno the car for 2 more weeks, it run fine for the first few days, but couple of days ago I try to see how the boost goes, but the car is sort of quietly back firing, ( if I could it call it that way) in the exhaust at idle and also when I pass 5K RPM, it feels like the car sputtering or I can say cutting off. So now I try not to push too much on the gas and not to go to WOT to avoid that problem. Today I went again and pulled all the plugs out to check the gap, they are only 2 week old, they are one step colder that stock .. they all looked like new, nothing abnormal .. the gap seems to be around 1mm or 0.04. I checked all the hoses again to make sure nothing is loose and disconnected after my new injectors and connectors installation.. everything checked out OK .. I am not sure what’s going on. Also the auxiliary fan keeps coming on and off .. which never happened to me before. If you have any advice I would appreciate it, I am tempted to swap the chip with # 3 .. better be safe even if it run richer. Thanks and have a nice end of week end Matt You mentioned that the auxiliary fan keeps kicking on and off. When the car exceeds 217 degrees, the ECU will turn the auxiliary fan on. You didn't mention there being white smoke coming out of the tailpipes which is indicative of a head gasket failure so it looks like it was just overheating at that point. I'm at a loss as to what exactly what caused the problem as there are a lot of variables and the potential candidates go beyond the work I did for you, although the ECU is still a potential source but I think there are other possibilities that stand out more. It would have been nice to have taken it to the dyno to verify how it was running - we likely would have prevented this problem.
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