As title states ahould i be concerned about boost or hp on the engine? 14-17 psi duable on a stock ls3 longblock on e85 with plenty of fuel through a ti-trim? when is boost an issue? which one should i be worried of first boost or hp?

 

Run 16 on mine

 

Ran 16 psi on my LS2 with a Paxton 1500. Made 760 whpr for 8 years. Drove it like I stole it, raced it regularly. Retired the build because I wanted much more power.

I have seen many LS3s making 800 come out of ECS without issue and live long lives. The secret to longevity is good fuel, good tune, and regular maintenance.

 

so boost numbers to a point is irrelevant? The tuner i previously tuned with said 12-13 psi max after that it would crack the pistons rings but he wants instead to cam the engine to make more hp but my dilemma is hp is cylinder pressure doesn't matter how its obtained so lets say 800hp through 16 psi should be the same as 12 psi cammed right? Same stress on the engine internals

 

Yes.

Cylinder pressure is relevant, boost is not. The only thing that cares about boost is your couplers/intake manifold/etc. Most of those are good for 30+psi. The motor doesn't care if it is 15psi or 30+. During compression it is seeing 500-800+psi so do you think it cares about 10 or 15psi? It is the cylinder pressure it cares about.

You can make 800rwhp on 8psi and your pistons/engine are under more stress than 700rwhp on 15psi.

You deserve an award or cookie for actually getting it. Amazing how sooo many people can't get this basic concept.

 

alright since the big boys answered my doubts i feel more at ease thank you guys so much

 

Good info in here.

 

Your compression ratio and boost pressure determine static cylinder pressure which is how much pressure is developed at TDC without ignition . 11:1 CR @ 8psi might have the same static pressure 9:1 CR @ 20psi and same HP potential, so as unreal said, boost is irrelevant, it's cylinder pressure that makes or breaks an engine, Not static pressure, but pressure during combustion which increases the harder the engine works

The magic or destruction happens in the tune. The tune determines max dynamic cylinder pressure which can peak over 2000psi during combustion at heavy loads and you better have the bottom end to support it or expect cracked pistons, bent rods, maybe get lucky with just a blown head gasket. The real question is how much max dynamic pressure can the bottom end take.

My opinion for a stock LS3 bottom end is 12psi with no meth on 93, 14 on corn, no more than 10* spark above 300g/s. If you can generate more boost than that, just put a restrictor on the inlet which only affects the max boost level.

 

Good info here. I was just in this same situation. After my dyno tuning session the tuner said my cylinder pressures were way to high on my stock bottom LS3 and stated I needed to go back to a stock size balancer (was running a 8" Powerbond) and a 4" blower pulley immediately (was using a 3.8"). This was on a Ti A&A kit with 91 pump gas (no ethanol content) making 14 pounds of boost and came in at 640 HP detuned to keep cylinder pressures lower.

I have made the pulley changes and will be putting 93 octane in the tank (up to 10% ethanol) and going back for a fine tune. Not sure which pump gas is better, the 91 which is straight fuel or the 93 that has some ethanol content, or if it even matters?

 

My theory on pulley size is forget about boost numbers altogether...Size the HB and SC pulley to run the blower speed 10% over the manufacturer's max speed at your max target motor RPM. Then see where boost levels are at.. Too high?, then start bleeding at max or restrict the inlet. Either way keeps the benefit of boost coming in quicker at lower RPMs.

Side effect is higher IATs and slight parasitic HP loss because SC is being overdriven, then vented to atmosphere but that only happens at MAX RPM. Probably best not for a daily though and sure there are other negatives to doing this

I'm interested in seeing how different my car runs when they get rid of the E10 adder which I think is onlu used in the winter here in the Northeast

 

Is this accurate?
In short - 93 E10, slightly better.
93 E10 = higher octane, more potential power due to potentially more T advance AND cylinder charge temperature slightly lower (more fuel shot in due to lower BTU value in the E10/93) ie more power? MPG (not that any one cares) would be less due to slightly additional "fuel" required/used so benefits from higher volume of fuel charge = cooler temps?
91 pure hydrocarbon = higher BTU (less fuel charge used) so more energy per volume of fuel = better MPG but less power due to less cooling effect & lower octane ie less timing in tune?
The only reason I mention MPG is to relate the fuel charge used (inj size) - certainly not not cuz MPG matters.
If above true, then e85 = more power cuz higher octane = more potential advance + more charge fuel required because its low BTU value, but that means the additional fuel charge keeps temps relatively low=more power again? Substantially Lower MPG from additional charge fuel volume required.

ETA; as a side note, E content used to vary widly, especially when they first started using it. E is added at the truck (or used to be), and wasn't blended at the exact % always. Chevron used to be able to blend at 5.7% e and make the CARB specs. Now the Fed mandates 10% e in most metro areas, and Chevron had to change to 10% e. Ethanol notification on pumps, regions its used in and laws (and emission regs) vary state to state. Point is, it's hard to determine EXACTLY when - or exactly what % E is in our fuel. In CA, we are on CARB phase IV or higher gasoline blending recipes. Lower sulfur, aromatics, olefins, etc than the *other* 49 states have. And those blend specs are evolving and new specs are coming for CA. It's getting more & more difficult to be 100% confident of what is the "gasoline" at the pump. <Stepping down from soap box now>