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I'm curious what you guys would recommend for the setup in my sig on just 91 octane. Low compression 4.8, 11 blade billet 475, 83mm T4 1.10AR. Right now I'm at 12psi, 14º, 11.2-11.5 AFR and it hauls freaking ***, wondering what you guys think.
PS - Currently, my IATs barely even move under boost. I've got a 31x12x4" intercooler up front.
Last edited by 67Firebird455; Apr 10, 2016 at 11:30 PM.
I'm running 16 degrees at 12 PSI. Not relying on the water/meth at all at that point.
My setup is similar to his. Almost identical turbo and intercooler. He has low compression 4.8, and I have a 10:1 5.3. A 70/30 mix of water/meth has saved my engine on almost a dozen occasions.
I run 22-24 PSI on this setup on pump gas and a 70/30 mix with 12 degrees of timing above 14 PSI. I've got 30 PSI and went super lean (15:1) almost a dozen times thanks to boost controller issues. Compression is still 185 PSI in every cylinder, pistons look perfect. Never even found a hint of KR on the logs.
Why not add water/meth injection?
Its probably the single smartest thing I've done with my build.
I plan to pal. I have the alky control with two M15 nozzles but no reservoir yet and have been hot rodding around just having a blast driving the car for the first time in 13 years on pump gas only. Just wanted to know your guys' thoughts since this thing is so low compression.
I'm running 16 degrees at 12 PSI. Not relying on the water/meth at all at that point.
My setup is similar to his. Almost identical turbo and intercooler. He has low compression 4.8, and I have a 10:1 5.3. A 70/30 mix of water/meth has saved my engine on almost a dozen occasions.
I run 22-24 PSI on this setup on pump gas and a 70/30 mix with 12 degrees of timing above 14 PSI. I've got 30 PSI and went super lean (15:1) almost a dozen times thanks to boost controller issues. Compression is still 185 PSI in every cylinder, pistons look perfect. Never even found a hint of KR on the logs.
Every setup will vary. I'd start out at 10* set your boost level. Then add a degree with a new plug in your hottest cylinder. Make a pass and immediately read the plug. (no idle/cruise time) If you up the boost drop timing back to 10* and start the process over.
Low compression motors will usually need a tad more timing.
@Forcefed86 - You ever run yours on pump only? You had/have 317's on yours too right? I'm curious what us low-compression, small-displacement guys are getting away with 'safely' boost-wise. I can't imagine 15psi being an issue with IATs under control on 91 with 12-13º timing. I was adjusting my boost controller last night and logged a 15.4psi spike into 3rd gear that settled to 14.5 and got no KR. This was at 11.1-11.2 and 13º. I see what people are talking about with getting boost, it's addictive. I have my controller set as low as the gate will allow and see ~7psi, flip the switch and hit 14.5-15psi.
What I really need to do is quit being a lazy *** and get the alky control setup in this pig.
No, always ran E85. I’d assume your safe as well. But I’d Pop in a new plug and make that pull again and read it. It will let you know for sure. For the cost of an alky control kit you can almost pick up the $560 MS3. Then you’d have even better control over the alky injection and 100 other handy options.
i have a 370 9 to 1 compr .i run pump 93 15 psi 16deg of timing from 4400 to shift at 6200 .i think.. just my opinion cam shaft has a lot to do with it my 228/232 lot of duration compared to most turbo cams .dont build as much cylinder pressure allows me to get away with 16deg on pump along with 9 to 1 i 317 heads also
No, always ran E85. I’d assume your safe as well. But I’d Pop in a new plug and make that pull again and read it. It will let you know for sure. For the cost of an alky control kit you can almost pick up the $560 MS3. Then you’d have even better control over the alky injection and 100 other handy options.
Damnit, I already have the Alky kit. I bought it from a buddy that went E85. How long of a pull would you recommend? I obviously can't be going 120+ on country roads for very long, haha.
Damnit, I already have the Alky kit. I bought it from a buddy that went E85. How long of a pull would you recommend? I obviously can't be going 120+ on country roads for very long, haha.
Damnit, I already have the Alky kit. I bought it from a buddy that went E85. How long of a pull would you recommend? I obviously can't be going 120+ on country roads for very long, haha.
As long as your comfortable with then... Should really pop in all new plugs and do a quick blast. Then pull over and pull all the plugs immediately. Find your hottest cylinder indicated by the heat mark on the ground strap. Then next time you can just cycle a new plug in and out of that cylinder when tuning. Take a hand full of plugs to the track with you and do the final tuning there.
As long as your comfortable with then... Should really pop in all new plugs and do a quick blast. Then pull over and pull all the plugs immediately. Find your hottest cylinder indicated by the heat mark on the ground strap. Then next time you can just cycle a new plug in and out of that cylinder when tuning. Take a hand full of plugs to the track with you and do the final tuning there.
Great, looking at possibly hitting the track next month. Will try and see if I can get some preliminary plug-checking out of the way in advance here, just need to find a road nearby. Appreciate you taking the time!
I am absolutely not an expert, but it didn't blow up yet, so….I copied this from Matt & chopped off the top of the curve to match my setup.
5.3 (LM7), truck intake, stock compression, L33 head gaskets, LS6 cam, 706 heads, HX55 (about 65mm compressor) with the smallest turbine housing Holset offers.
mix of a little 87 & mostly 91 octane, zero knock recorded, tr6 plugs @ .018 gap. AFR varied from 11.3 - 11.9 during three dynojet pulls. I "think" this is a very conservative timing curve, even for a 300K mile engine. N
Last edited by twinturbo496; Apr 18, 2016 at 05:16 PM.
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Boost/Timing 91 Octane only 
