I can see what you're saying and in my case where I have a running engine with a procharger on it, it makes sense to just click up the boost a bit. But when I start building more of a max effort setup I don't see any reason why I wouldn't want to maximize everything I can.

 

The benefit of 317's is lowering compression to run MORE boost....not because they flow so much better lol. Doing it again I wouldn't even do an LS6 intake. The entire intake tract is pressurized and much of the gain of an intake is from additional plenum volume.....which doesn't do a whole heck of a lot in this instance. I, however, would do valve springs as theyre cheap insurance.

 

Boost and octane have no direct correlation to each other. I've tuned smaller engines that made 40 PSI on 93 octane before.
Higher pressure raises the boiling and flash points of gasoline.
Pressure DOES decrease the autoignition temperature, but we'll get to that at the end.

And boost being a measurement of restriction is a bit of a misunderstanding. It is a measurement of resistance on the compressor, not the engine. You could run heads/intake with 6" wide ports and a 10" throttle body that poses ZERO restriction to flow, but you're still going to be making boost if the compressor inlet is pulling in more CFM than the engine can pull in by itself.

THE MOST IMPORTANT THING: airmass determines power/torque production.
If boost was a measurement of restriction, it would be highest before the valve, and would drop afterwards once entering the cylinder.
Whether boost is 25 PSI in the intake manifold or 5 PSI in the intake manifold, if the end result is the same amount of power, its because the airmass and boost pressure in the cylinder was the same, regardless of what it was in the intake manifold (as long as the camshaft and static compression ratio are the same). Since autoignition doesn't occur in the intake manifold, pre-cylinder pressure is completely irrelevant to knock/autoignition/octane, etc. You might increase the chances of a tuning error using a wider spread of the fueling/spark tables, or complications involving excess heat, but that's easily dealt with.

Long story short, heads/intake or any other pre-cylinder flow restrictions you might have will have NO effect on chances of knock with pump gas, because the cylinder pressure will be the same for a given power level, meaning that pressure's effect on autoignition temperature doesn't apply.

You want to change something that will allow you to make more power on less boost with a direct effect on your chances of knock with pump gas? Camshafts are the exception to the rule.
Everything else, you're literally throwing your money away.

 

^I'd love 2 particular individuals on here to get in here and reply to that post with their podcast crap.

 

 

Oh I know. I got into an argument about boost vs. cylinder heads with 2 geniuses on here who refused to listen to logic and math and only listened to podcasts and haven't built a boosted LS in their life. Would just love to see them argue with Joe's post. Comical.

 

See and that's interesting because it seems like there's two camps for these opposing ideas.
One camp says just add boost while the other camp encourages increasing airflow throughout the engine via heads, cam, intake etc.
I don't think saying you can push 40 lbs. on pump gas with a 2.0L engine is an applicable comparison since I don't know any LS guys doing that.
The consensus seems to be 12-14 lbs. on a 9.5:1 compression LS using pump fuel only is about as far as you want to go safely.
So wouldn't it make sense then to have as much flow as possible being fuel and boost limited?

 

@ OP, you are running a stock cam now?

I'd do a boost cam, you need better springs and LS6 intake.

 

Entirely dependent on the setup. SBE? Forged motor? 93 or E85 pump? Also depends on backpressure and island efficiency. When you're running 6 psi, doing heads and intake is a waste of money compared to running 20 psi on pump.

 

 

What I said was in relation to spending money on induction to reduce boost pressure because of fueling.
Making 800 horsepower on the current setup at 8 PSI with TFS220s and a FAST or MSD 102 is going to be the same detonation wise as just swapping pulleys and making 800 horsepower at 12-14 PSI.

Power production is something else entirely. The shape of the curve and RPM peaks will be changed. Those should be your main reasons for upgrading. Since the LS1 and LS6 intakes have very similar curves/peaks, there is basically no real advantage to swapping except wallet weight reduction.

I don't know where the 12-14 PSI recommendation came from unless it was 10 years ago. I could see it being used as a rule of thumb for limiting power to keep the rods alive, but definitely not for keeping it pump gas friendly.
I maxed out the billet S475 and deka 80s on 93 with a 10:1 5.3 at 26 PSI with zero knock retard.
Don't be a afraid of boost. The ONLY thing working harder with high boost is the thing that's producing it.

 

Ah okay, I see what you're saying and it makes sense.
Cylinder pressure for a given power level is the ultimate determining factor which is what I've heard from others as well.
I'm sure you agree there's enough good and bad info out there that you have to be careful what you take in lol.

 

Yep the engine has never been cracked open. Originally I was going to go to a more boost friendly cam, but I'm planning on romping on the stock motor all summer and doing something forged when it pops or next winter whichever comes first and max out the D1. With that in mind I think it makes sense to buy parts (if they offer some benefit) that I can carry over should I punch a hole in one of the pistons. An 8-rib upgrade and ls6 intake *seem* to fit that bill..


So basically yeah I want to do a cam, but after this thread and some more research I think I'd like to wait until my power goals are much higher than somewhere close to 500whp.

 

This thread has me re-thinking my life! I feel now I should just get a turbo setup on my stock 6.0 and call it good!

 

Okay then, I'd do an LS6 intake and a new set of valve springs.

 

this is prob one of Confucius's very first famous quotes.
basicly its poetry.
i will live by this.

 

This is the route I'm going, I've got an LS6 intake in the mail from a member, and we'll toss a set of more budget conscious springs on at the same time.

 

Thanks for the enlightening post Joe. That's what I'd always thought in my head that cylinder pressure is what determines the knock threshold of a particular setup . My only other question is as you raise boost , the drive pressure also goes up , which would cause pumping losses to be higher in case of a turbo and in a superchargers case the parasitic losses from driving it harder would go up , do you think in that case to produce X amount of HP at say 8psi would have lower cylinder pressures due to less parasitic losses than say 16 psi .

 

Yeah, drive pressure goes up and there are small pumping losses.
You're talking about very very small increases in cylinder pressure, because once the exhaust valve is closed, you're back to relying purely on intake air to provide cylinder pressure.
Most of the increase would come from the slight increase in cylinder pressure that remains during overlap. Then the exhaust valve closes and you rely on intake air to do the rest of the job.

We're talking 0.5 PSI max to compensate for pumping losses. It just ties into my previous argument. Run more boost until you hit your goal.
The boost number shouldn't be the worry, it should be the power you're trying to reach. As the supercharger guys say "Who cares about parasitic loss when my goal was 800 and I made 800".

 

This is interesting. I'm currently considering my options for a "future build". I'd really like to have a Pro-Charger, but I already swapped the heads, cam, and intake. I wish I would have started with the Pro-Charger.

How much wheel hp are you making now? According to my research, the P1 and Vortec kits make about 500 whp on stock motors. I wasn't sure if the D1 made any more. I figured the P1 would make around 580 whp with a cam/intake swap. What is your goal?