So I built a really nice NA engine over the past year https://ls1tech.com/forums/generatio...ls2-build.html and Im very happy with it so far. Someone asked me about boost and I was like hell no not with my compression but then it got me thinking..

What would it take to actually run boost on this thing. I know the quench is very tight at .036 so if I bump it up to .051 it should bring me to 11.36:1, how feasible is it to run low boost, something like a D1X at say 10-12# on pump gas? Maybe spraying meth? Obviously many variables.

 

Keep the fuel right and you will be fine.

 

My L92 SBE has 10.5:1 on 11 psi and runs great. LS3 guys run LSA superchargers all the time and they run fine in the 11:1 range. Just get your tune right.

 

Ya exactly guys boost LS7's all the time, they make good power with boost. On pump and meth I ran up to 20PSI or so on 11:1, then I switched to E85 for 30. If you are going to run E85 I would just leave it alone and boost it

 

There is a thread on FeeB active right now and some folks are being snarky in their replies "ain't just about compression it's all about cylinder pressure" but they don't post anything really helpful for the OP. Maybe one of you guys could talk about cylinder pressure.

Smart friends tell me on the regular less quench tightens up the tuning window.

 

My opinion I would keep boost around 10-12 max on 93 but with flex or E85 you can go crazy. Just bad instances where you can get a bad tank of pump gas.

 

Tighter quench actually reduces the chance of detonation. Tune it like you normally would, read the plugs and give the engine what it wants. Not many people have tools to measure cylinder pressure, but I'm sure everyone on FeeB does

 

My brothers lsx454 was 12.2 to 1 and ran north of 20 psi on e85. Made almost 1100 wheel . Never had an issue but good fuel is the key

 

And I was worried about my little 10.4:1 motor on pump gas..... Still broke a piston at 11-12psi tho! and 11 degrees of timing. afr was 11.6-11.8:1 so it may have been a little lean.

 

just curious, what would you consider good afr at that level.....I've gotta 370" lq9 with 64cc ls3 heads and a lsa supercharger , I'm hovering around 11.15:1 compression and around 11-12psi as well, I have my afr commanded at 11.5 under boost and I'm at 18° timing....wot no boost, terminator x set to pull 1° per lb of boost.....I'm still trying to find the sweet spot on timing, and afr do you think I should bring it up to 10.5??? Sorry to hear about your piston.....did a ring land give up the ghost?

 

i've found the happy spot on my motor is 11.2-11.4afr up to about 13-14psi and i'll get to 10.5-10.8afr at 20psi.
so if you are at 12psi, you have only 6 degrees of timing? I think it should take 8-10 degrees at the boost.
I broke a top ring land.
If i had to do it all over again, i would have added the washer fluid injection as a safety. Mine is super simple, 5gph nozzle being fed by my washer pump injecting preturbo after 15psi. Stock piston motor i'd probably spray it at 8psi. It does help.

i think if you put your afr at 10.5 at that low of boost, its going to kill power. 11.2 is safe and wont kill much power.

honestly I feel like afr isnt a "one size fits all". This is what i go by, and I just figured this out on my own:

1-2psi 11.8:1
2-6psi 11.6:1
7-8psi 11.4-11.5:1
9-14psi 11.2:1
15-17psi 11.0:1
18-20psi 10.8:1
22-24psi 10.5-10.6:1

roughly thats what i shoot for to be on the safe side. I'm no professional, but going by this I've been safe and trouble free for the past couple years. I do drive the car alot and get on it every chance I get.

 

I'd need to check my tune again, but I know I'm running 18* of timing at 11 psi and I believe my AFR is around 12-12.5:1 I have knock sensors enabled in my tune with Terminator X and it had no signs of knock. My tuner said that if I wanted I could bump the timing up a few more degrees. But I was only shooting for 600 whp and we had already hit 633, so I just kept it there where it was happy. I should also mention that I gapped my rings per Mahle's instructions for a supercharged car. .024/.026 top and bottom. I've been reading a lot about what fails on the LS cars when boosted and the common thread seems to be ring lands.

OP if you aren't properly gapped, I would suggest addressing it now before something breaks.

 

no way your afr is 12-12.5 unless you are direct injected.

******anyone reading this****** DO NOT think you can get away an afr that lean on pump gas. Unless its direct injected OR you like spending money on broken parts!

 

I'm in comiefornia and only get shitty 91 so I kinda screwed there, but my average boost range out of my lsa supercharger is around 10 lbs given all the other mods I had when I was N/A......I've logged 15lbs once and 19.5 lbs once , I gotta 2.45" pulley but I know that those 15lbs and 19.5lbs had to be bad map sensor readings because I cannot recreate that kinda boost again, I'd like to sustain 13/14lbs boost, but with my 230/220-117+4 cam and long tube headers with full 3' exhaust and 11.15:1 compression I don't think it's gonna happen, will timing being off by 1° make it so I can't make that high of boost or does that not matter and I should consider a more restrictive exhaust. ......I just don't know what would make my datalogs show 15lbs or 19.5 lbs......just those single times, the bypass valve is hooked directly to manifold vacuum and not the snout, and I made sure it was properly adjusted, I'm sure the 19.5lbs was a fluke and I definitely don't wanna be that high but 14/15lbs I think that is doable and could possibly actually be a true reading. .....I just seem to be chasing my tail trying to see that 15lbs again.....but with that said at my average 10-11lbs I have the afr set at 11.5 under boost. .....maybe I should fatten it just a hair???

 

Did he say he was on 93 pump gas? I see lots of guys run 12's on E85 pump fuel with a lot more boost than that, I'm not a fan of it but people do it and get away with it.


That's mega safe and on a turbo often results in slower spool. I don't get into the 11's AF until after the turbo is singing, same with timing don't put it in the dirt the second you crack 101KPA, makes for a more responsive combo.

 

he didn’t say. And I assumed the op was referring to using pump fuel when he was asking his original question. So to keep someone from breaking their motor, thinking they can get away with that lean of a mixture….so I felt it my duty to warn anyone. My guess is it was a typo or misunderstanding from the poster and tuner. No damn way I’d ever run an engine that lean on boost.


and I’d much rather be safe and leave a little power on the table than be right on the edge and leave engine parts on the street!


And I agree...too rich will hurt the spooling of the turbo....but not a supercharger......unless a d1x is some sort of turbo I didnt know of

 

My rings were gapped for up to 250 of nitrous, I believe .026/.028 were the the numbers I saw on the paper work. As much as I'd like to run E85 it's almost non existent up here in the north east unless you buy the expensive VP stuff etc. I know they say tighter quench is more resistant to detonation but when is the quench too tight? I know quite a few nitrous guys and they all run pretty loose .060+ on the quench and say not to go tighter.

 

Worth mentioning IAT in the same sentence as boost, timing and AFR in relation to detonation. ECT worth knowing too since it will impact fuel limit and detonation.

 

is this on 93

 

Yes, I have only run 93, sorry I should have mentioned that.

I can't comment on e85 yet because i have no experience with it.