Boost Psi for 750rwhp

95 imp · 08-07-2019, 12:14 PM

First off, I know it isn't a cut in stone thing. Variables like cam/heads/exhaust etc. are going to affect the actual numbers.

That being said, what are the typical psi numbers for an otherwise stock motor to hit 750 on LT's?

Or, is a cam change mandatory to hit it?

Also, I asked somewhere else, what's the cc difference between LT1 and LT4 heads? Or, the new CR with the 4's heads on the 1's pistons?

Rlhay2 · 08-07-2019, 12:39 PM

Cam change is likely necessary just to meet the fuel needs.

95 imp · 08-07-2019, 12:53 PM

Quote:

Originally Posted by Rlhay2

Cam change is likely necessary just to meet the fuel needs.

Forgot about the fuel lobe.... grrrr….

laynlo15 · 08-07-2019, 01:10 PM

I guess first off, are we talking about a Camaro with A8 or stick? What blower do you intend to run? Way to many variables to talk about till you give us an idea. What fuel are you going to run, you'll need LT4 fuel system, maybe some Meth/water, etc. My stock motor made over 750 on 16.5 lbs of boost, ring lands didn't like it after 180 passes down the track and that was on race fuel and some meth/water combo. Numbers for these cars are all over the place depending on what your boosting with. Do you own a Camaro?

Umbriel · 08-07-2019, 01:21 PM

I know the LT4 fuel system with a 32% cam and SMG auxiliary isn't enough for an F-1a at 12 pounds. I am having to go either bigger DI or secondary port.

KingLT1 · 08-07-2019, 01:44 PM

Quote:

Originally Posted by Umbriel

I know the LT4 fuel system with a 32% cam and SMG auxiliary isn't enough for an F-1a at 12 pounds. I am having to go either bigger DI or secondary port.

Seems odd. Plenty of other setups have ran that boost with that fuel system with no issues. I would be curious to know the AFR your tuner is targeting.

Umbriel · 08-07-2019, 01:51 PM

Quote:

Originally Posted by KingLT1

Seems odd. Plenty of other setups have ran that boost with that fuel system with no issues. I would be curious to know the AFR your tuner is targeting.

He said the injectors were out of fuel at 12 psi so he couldn't go any further. I trust him completely, he has been tuning for a long time. If you watch the video of Hellion Turbo installing their first kit the tuner that they fly out to tune it is my tuner. I have no idea what he was shooting for he just said it was out of injector so I believed him and started looking for other options.

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*Joshinator99* · 08-07-2019, 02:01 PM

Quote:

Originally Posted by Umbriel

He said the injectors were out of fuel at 12 psi so he couldn't go any further. I trust him completely, he has been tuning for a long time. If you watch the video of Hellion Turbo installing their first kit the tuner that they fly out to tune it is my tuner. I have no idea what he was shooting for he just said it was out of injector so I believed him and started looking for other options.

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If the rail pressure dropped, that would cause the injector pw to be an issue. What was the rail pressure when you hit your injector limit?

Umbriel · 08-07-2019, 02:07 PM

Quote:

Originally Posted by Joshinator99

If the rail pressure dropped, that would cause the injector pw to be an issue. What was the rail pressure when you hit your injector limit?

I didn't ask him any details honestly, he said everything was good up until the injectors including rail pressure and the injectors just couldn't keep up.

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G2K · 08-07-2019, 02:35 PM

Quote:

Originally Posted by Umbriel

I know the LT4 fuel system with a 32% cam and SMG auxiliary isn't enough for an F-1a at 12 pounds. I am having to go either bigger DI or secondary port.

Weird a close friend of mine ran 1K hp on his setup for along period of time F1A lt4 stuff.... he did have meth tho... NOW he's in the process of the +45% inj and LPE high side... he wants 1200hp.

Umbriel · 08-07-2019, 02:36 PM

Quote:

Originally Posted by G2K

Weird a close friend of mine ran 1K hp on his setup for along period of time F1A lt4 stuff.... he did have meth tho... NOW he's in the process of the +45% inj and LPE high side... he wants 1200hp.

Yeah my tuner said I had meth it would be no problem, I just don't want to run a meth kit.

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G2K · 08-07-2019, 02:38 PM

to the OP like laynlo15 said, there just way too many variables and many ways to obtain this 750whp target... but you'll definitely need fuel one way or another because none of the LT1 stuff will be sufficient. Based on what you get will determine the PSI amount needed anywhere from 9-15psi again, too many variables.

95 imp · 08-07-2019, 02:44 PM

Quote:

Originally Posted by laynlo15

I guess first off, are we talking about a Camaro with A8 or stick? What blower do you intend to run? Way to many variables to talk about till you give us an idea. What fuel are you going to run, you'll need LT4 fuel system, maybe some Meth/water, etc. My stock motor made over 750 on 16.5 lbs of boost, ring lands didn't like it after 180 passes down the track and that was on race fuel and some meth/water combo. Numbers for these cars are all over the place depending on what your boosting with. Do you own a Camaro?

Stick.

Probably a procharger D1x

Ported heads, valves, exhaust (intake on a pro) and cam are all going to change boost psi. So, I'm asking for an apple to apple comparison, or as close as possible, to try and theoretically figure out where I need to be.

Fuel depends on the FCR. You can't force an engine to drink a fuel it doesn't like for very long. And it would be backwards to say I'm running 91 octane and want 800 hp. Only place I know that can make a combo like that work is Fantasy Motorsports. The fuel is what I trying to figure out. But I need to have a ballpark FCR. That means I need a ballpark psi. The volume vs octane tightrope, IMO, is what is killing these motors.

So, for example, (assuming a 2400 +/- elevation) you were running a FCR around 23/1. That needs hella octane to not detonate. Either in the gas, E, meth, or all 3. (For reference, a Duramax diesel is only 17.5/1)

What I trying to say is I want XXX hp and what do I need to make it happen within a particular engine. I do not want to just throw money and tears at it based on a guess.

Does it really matter what I own? Or what car I put a motor in? I thought this was a brotherhood type thing. I'm not trying to bust anyone's balls. Sorry if it comes across that way. I'm just trying to figure out the best way to hit my goals with what is available and I'm asking the peeps in the group to share some hard earned knowledge while I give some of mine and we all become better.

So, back to the topic.... Was the 750 @ 16.5 bone stock except for lt4 fueling? What octane fuel?

95 imp · 08-07-2019, 02:56 PM

Quote:

Originally Posted by G2K

to the OP like laynlo15 said, there just way too many variables and many ways to obtain this 750whp target... but you'll definitely need fuel one way or another because none of the LT1 stuff will be sufficient. Based on what you get will determine the PSI amount needed anywhere from 9-15psi again, too many variables.

It seems like the LT4 stuff is borderline too. I'm trying to figure out how to fuel it with the right octane and volume.

I'm not particularly fond of the meth route. IMO, it's a weak link and can toast an engine too easy. That leaves the injectors/pumps. E needs volume that they can't supply. Final option is gasoline. I need a theoretical octane to see if I need race gas or I can blend my own and make it happen.

Or if the CR just needs to be dropped before I trash a block and slugs.

08-07-2019, 12:14 PM	#1
95 imp Dumb Ass Deluxe Drives: A Tricked Out Mountain Bike Join Date: Jun 2019 Location: Arizona Posts: 1,963	Boost Psi for 750rwhp First off, I know it isn't a cut in stone thing. Variables like cam/heads/exhaust etc. are going to affect the actual numbers. That being said, what are the typical psi numbers for an otherwise stock motor to hit 750 on LT's? Or, is a cam change mandatory to hit it? Also, I asked somewhere else, what's the cc difference between LT1 and LT4 heads? Or, the new CR with the 4's heads on the 1's pistons?

08-07-2019, 02:38 PM	#12
G2K @Blackmamba_1LE Drives: 2017 1LE Join Date: Jun 2017 Location: South Florida Posts: 787	to the OP like laynlo15 said, there just way too many variables and many ways to obtain this 750whp target... but you'll definitely need fuel one way or another because none of the LT1 stuff will be sufficient. Based on what you get will determine the PSI amount needed anywhere from 9-15psi again, too many variables. __________________ Florida High Performance: H/C Whipple LME 377 900WHP

08-07-2019, 12:39 PM	#2
Rlhay2 Drives: 2017 ZL1 Join Date: Mar 2014 Location: DFW, TX Posts: 310	Cam change is likely necessary just to meet the fuel needs.

08-07-2019, 01:10 PM	#4
laynlo15 Drives: 2022 Lt1 A10 Join Date: Nov 2015 Location: clark, mo Posts: 8,882	I guess first off, are we talking about a Camaro with A8 or stick? What blower do you intend to run? Way to many variables to talk about till you give us an idea. What fuel are you going to run, you'll need LT4 fuel system, maybe some Meth/water, etc. My stock motor made over 750 on 16.5 lbs of boost, ring lands didn't like it after 180 passes down the track and that was on race fuel and some meth/water combo. Numbers for these cars are all over the place depending on what your boosting with. Do you own a Camaro?

08-07-2019, 01:21 PM	#5
Umbriel Drives: 2016 Camaro SS Join Date: Sep 2018 Location: Bartlett, TN Posts: 1,121	I know the LT4 fuel system with a 32% cam and SMG auxiliary isn't enough for an F-1a at 12 pounds. I am having to go either bigger DI or secondary port.

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