Lq9 turbo best compression
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Stock lq9 is 10:1 I believe , so if the stock stuff is in good shape I would use it but keep the timing low. Denman's usual starting point of 14°@14lbs for pump gas I would reduce to 10°@14lbs to start out read plugs /knock sensors go from there. If I was determined to build I'd still choose the lower 9-9.5 ratio though - for your power goals. Easier to tune and if more power required just add more boost. Did you change plans from the lm7? Or starting another project?
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Stock lq9 is 10:1 I believe , so if the stock stuff is in good shape I would use it but keep the timing low. Denman's usual starting point of 14°@14lbs for pump gas I would reduce to 10°@14lbs to start out read plugs /knock sensors go from there. If I was determined to build I'd still choose the lower 9-9.5 ratio though - for your power goals. Easier to tune and if more power required just add more boost. Did you change plans from the lm7? Or starting another project?
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Verdad Gallardo TECH Enthusiast
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Yeah I found a complete lq9 with 6l80e for cheap so decided to build this instead as the lm7 I have which is mainly block and heads with a few other parts but not worth the hassle. I have all the parts saved for my lm7 build for future so now I need to restart with this. Lq9 has just over 300km on it.
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ha ha , when I read 300km on it l thought daamm that things brand new (I'm Canadian ) lol. I'm guessing you mean 300,000 miles ? If this is the case I would probably like to take that apart and check it out . Don't be surprised if it doesn't need much , maybe rings ,bearings ,t-chain,cam,springs, valve seals,lap valves. It's really going to depend on it's previous life and maintenance. My lq4 had 180,000 miles and I didn't touch it , other than cam , springs seals . Boosted for 7500 miles now ,no issues. Start checking it out - see what you find . Did you hear it run ? I don't anything about 6l80e other than a 4:1 first gear and not sure how that would work , would depend on the application. Someone can prob chime in about 6l80e
Last edited by Dylan72; Apr 1, 2020 at 12:04 AM.
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Mine was 290,000 km ,was probably maintained pretty well. There's 1100 pages of info on here , I browsed through and read anything that was close to my project and goals, lots of info here and the sloppy mechanics wiki page, also check the stock bottom end and reliability sticky. Just saying that what you have already might be just fine for your goals and that it's been done by many on this forum. Trying to save you money and time -you'll need the money for tires and a cage probably lol. Sloppy has a video of putting the hd2 kit in a 4l80e , it's not too hard.
I'd leave cr stock. 9.5:1 or 10.0:1 is plenty enough to spool the turbo and still leave a decent tuning window. For probably 90+% of us, that will provide enough horsepower on the street to get you into lots of trouble. Unless your looking for a class specific racing build, your more than fine and should have more than enough power.
I’m no professional, but here’s my opinion based on what I just did. So I had a 10.7:1ish ls1 in my gto. Pump 93. I could only run 11 degrees of timing at 11-12psi and if I added one more degree I’d pick up knock in my scanner and I could hear it clatter when I shifted to 3rd gear. So based off of that, I wanted to run higher boost (I broke a piston in the 5.7 from detonation, I leaned it out to 11.7 afr and it clattered and I didn’t let off) so I built a lower compression 5.3. Same cam. Same heads. Same intake. Turbo. Everything except engine size and compression. New motor is 9.4-9.5:1. I’m running 15psi, 14-15 degrees timing. Feels about 100hp stronger. I ran it on 19.6psi (accident lol) the other night, 14 degrees, 93 pump and it didn’t clatter nor did my log pick up knock.
My take: higher compression will work, however, it’s more dangerous and the line you may cross from safe to dangerous....is much thinner than with lower compression. I feel like the lower compression allows more boost, more timing and more power. I could probably run 87 octane on 8-10psi.
Just my .02
My take: higher compression will work, however, it’s more dangerous and the line you may cross from safe to dangerous....is much thinner than with lower compression. I feel like the lower compression allows more boost, more timing and more power. I could probably run 87 octane on 8-10psi.
Just my .02
TECH Enthusiast
Joined: Feb 2020
Posts: 734
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I’m no professional, but here’s my opinion based on what I just did. So I had a 10.7:1ish ls1 in my gto. Pump 93. I could only run 11 degrees of timing at 11-12psi and if I added one more degree I’d pick up knock in my scanner and I could hear it clatter when I shifted to 3rd gear. So based off of that, I wanted to run higher boost (I broke a piston in the 5.7 from detonation, I leaned it out to 11.7 afr and it clattered and I didn’t let off) so I built a lower compression 5.3. Same cam. Same heads. Same intake. Turbo. Everything except engine size and compression. New motor is 9.4-9.5:1. I’m running 15psi, 14-15 degrees timing. Feels about 100hp stronger. I ran it on 19.6psi (accident lol) the other night, 14 degrees, 93 pump and it didn’t clatter nor did my log pick up knock.
My take: higher compression will work, however, it’s more dangerous and the line you may cross from safe to dangerous....is much thinner than with lower compression. I feel like the lower compression allows more boost, more timing and more power. I could probably run 87 octane on 8-10psi.
Just my .02
My take: higher compression will work, however, it’s more dangerous and the line you may cross from safe to dangerous....is much thinner than with lower compression. I feel like the lower compression allows more boost, more timing and more power. I could probably run 87 octane on 8-10psi.
Just my .02