5.3 popped at 7psi, why?
09-10-2012, 10:13 AM
#1
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5.3 popped at 7psi, why?
Hello,
'06 100k mile all stock 5.3 with KB front mount MP70. BB tune, truck was running great on a MAF tune at 7psi. Idle, part throttle, full throttle, everything was great, steady 11.3ish AFR on the wideband in boost.
Driving down the highway, maybe 75 degree outside temp, passing a few cars at full boost once in awhile, but otherwise driving normal (75mph). Have a 29x12x2.5 intercooler right behind the grill. Went to pass a another car and it only hit 4psi boost and made a weird sound, looked in the mirror and sure enough, the blue smoke trail of death. Got it home, #1 cyl has a squished electrode, and 3 and 5 have no compression.
Running 91 octane, pretty much all that's available here. I should mention that the MAF is preturbo, and I have yet to relocate the IAT sensor. I thought however that I would be safe due to highway driving, intercooler up front, and low, infrequent boost.
I've attached a log, it isn't when the engine blew, but not long before. Tune also attached.
Any input? Bad fuel maybe? It's at 17* timing which the tuner said was pretty safe. I picked up another long block already for $300, so fortunately not real expensive, just labor intensive!
PS, 44# injectors and walbro 255, if either of these were insufficient, you would see it go lean, correct? Thanks guys.
'06 100k mile all stock 5.3 with KB front mount MP70. BB tune, truck was running great on a MAF tune at 7psi. Idle, part throttle, full throttle, everything was great, steady 11.3ish AFR on the wideband in boost.
Driving down the highway, maybe 75 degree outside temp, passing a few cars at full boost once in awhile, but otherwise driving normal (75mph). Have a 29x12x2.5 intercooler right behind the grill. Went to pass a another car and it only hit 4psi boost and made a weird sound, looked in the mirror and sure enough, the blue smoke trail of death. Got it home, #1 cyl has a squished electrode, and 3 and 5 have no compression.
Running 91 octane, pretty much all that's available here. I should mention that the MAF is preturbo, and I have yet to relocate the IAT sensor. I thought however that I would be safe due to highway driving, intercooler up front, and low, infrequent boost.
I've attached a log, it isn't when the engine blew, but not long before. Tune also attached.
Any input? Bad fuel maybe? It's at 17* timing which the tuner said was pretty safe. I picked up another long block already for $300, so fortunately not real expensive, just labor intensive!
PS, 44# injectors and walbro 255, if either of these were insufficient, you would see it go lean, correct? Thanks guys.
09-10-2012, 11:17 AM
#3
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Could be a combination of too much timing, your iat sensor positioning and that small intercooler. The actual iat's could've been up to 60-80 degrees hotter than your iat sensor was reading
09-10-2012, 11:28 AM
#4
I would be that the IAT's were even higher than 80 degrees above what it was reading. That is one of the problems of not relocating the IAT. There would be nothing to tell the timing to back off when the IAT's are climbing. Also if you had a leak in the inlet pipe after the MAF and before the turbo, it would lean things out.
When mine let loose I was running 12 psi with a radix, and my IAT's were in the 230 range. I was really pushing it with timing too at 19.
When mine let loose I was running 12 psi with a radix, and my IAT's were in the 230 range. I was really pushing it with timing too at 19.
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09-10-2012, 12:24 PM
#8
09-10-2012, 12:31 PM
#9
Same page with these guys on the AIT being an issue. Another thing to look at is the tune. Since you was on the highway, you likely had a good load on the turbo and boost in lower rpms. Easy to get detenation down there with stock like timing, even more so with 91 oct fuel.
