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Hi,
Is the theory Rich AFR on spool and lower timing correct or ?
read both sides of argument.
what do you dial in from cruise, part and high map(pre boost) with AFR and timing.
my 5.7 sbe M6 is set to 11.5 at 105kpa...leaving power or good safety margins....?
only boost to 8psi
regards
gav
As high as timing as you can get will give you a better spool under all circumstances - with one very narrow exception.
The mantra on low timing, lots of fuel really comes from a specific boost building tune. This type of tune though, you have to retard timing so much (like -10 to -20 deg) that you are actually sending the fireball out the exhaust valve (which is why you add fuel). This will build boost very quickly, but it should only be used connected to a lag button or some sort of launching scheme. Otherwise, just ignore it, it is for a very niche boost-building circumstance or engines that have half your cylinders.
Just keep you timing as high as you can go and a/f around 13.5-14.0 (ramp to 11.5 once boosted) and you will build boost quicker for a street car.
As high as timing as you can get will give you a better spool under all circumstances - with one very narrow exception.
The mantra on low timing, lots of fuel really comes from a specific boost building tune. This type of tune though, you have to retard timing so much (like -10 to -20 deg) that you are actually sending the fireball out the exhaust valve (which is why you add fuel). This will build boost very quickly, but it should only be used connected to a lag button or some sort of launching scheme. Otherwise, just ignore it, it is for a very niche boost-building circumstance or engines that have half your cylinders.
Just keep you timing as high as you can go and a/f around 13.5-14.0 (ramp to 11.5 once boosted) and you will build boost quicker for a street car.
This is what Pat G did for my tune on my rod/piston LS1 S484 combo.
Everyone I've showed the tune to has commented that the timing is very aggressive out of boost and the assumption is that it's to light off the turbo which for being a big *** 84mm it lights off pretty fast.
Thought I remembered you are on the China GT45 turbo too, right? Those are notorious for slow spool, even when all the tune parameters are “happy”. Its just a heavy wheeled dinosaur of a turbo.
If you are only running 8psi… that’s a pretty bad match turbo wise. A much smaller S36xx clone would run circles around it spool wise and make more power per pound. So would man other cheaper units.
78/75 would likely be an upgrade from what you have and may be the cheapest option. But those wheel specs aren’t inherently great either. Ideally you want the exh wheel larger than the compressor. It’s also more turbo than is needed if the plan is to stay at 8psi.
You want just enough turbo to meet your goal. A 65mm ptrim exh wheel paired to a 60-70mm compressor would work ok and still be dirt cheap w china clones. The s366 I rode along with in a 5.3 was alight switch and crazy fun. It as a 66/73 turbo with a .81 t4. Ran well and was well into the 550whp territory. Suuuper snappy. ITs what i'd want with a manual trans.
People do timing retards to light off big turbos, a buddy just went through that, when he was an S483 it lit off fast and now that he's an s494 it needed some work to light off. And it has to leave higher on the 2 step.
If you only want 8psi, yes. Guys are making 20+lbs with those units on LS setups. But it would be better than a 78/75 spool wise. Its all a tradeoff, the bigger you go the slower it will spool. You trade response for big power potential. But if you never plan to use that potential… no need for a larger turbo as you are leaving response on the table.
I’d be looking for around a 66mm compressor unit with a p-trim 65mm or larger exh wheel. VS racing sells a 67/65 and a 61/65 for 319 shipped last I spoke to them. Have to email and ask about their “p-trim” line of turbos.
No, they are much smaller than the Gt45. The only issue i've seen with the S366 clones is a few have what look like clipped ceiling fan blades for turbines and are total junk.
You don't want to see daylight between your turbine blades like these clones. I'd ask to see a shot of the turbine blade. Otherwise.... that is probably fine. Def better than the Gt45
Before you automatically ASSume that you need some crazy fuel or timing in spooling region, at least try mapping the engine normally first to see how it responds. Large V8's don't usually struggle to spool a turbo like a smaller 3L engine. If you run normal fueling (lambda ~0.86 @ 100kPa, 0.8ish or less above that) and spark to good torque without knock, there should be a ton of energy in the exhaust to spool a turbo.
Hi,
yes have mapped engine out of boost a lot and had to back off in certain areas one or 2 degrees due to knock. Having seen any knock at all in boost though yet which I suppose is good.
regards
gav
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Timing and AF on spool M6 5.7 LS1 
