What displacement?
Thread Starter
Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
What displacement? Given the following;
- · Block, 12571048, 5.3l aluminum Gen IV with Darton sleeves, bored to 4.125”
- · Vortech Ti pulleyed to push 17 – 18 PSI @ 7,500 red line
- · Ported LSA heads
- · Appropriate cam & valve train
- · Stroke can be 3.622” (387 CI), 3.75" (400 CI) or 4.0” (427 CI)
- · 11:1 compression ratio
- · 1 7/8” long tube headers
- · High flow cats
- · 3” mid pipes and exhaust3” Borla S-Type mufflersE85 through 1,350 cc injectors pushed by 3 X Ti 274’s
Last edited by SteveJewels; Aug 24, 2022 at 02:23 PM.
Not super familiar with sleeved blocks but I'd probably lean towards the smaller cubic inch deals, 387 or 400ci if you're gonna be all in by 7,500 rpm.
Ideally whatever keeps the piston in the cylinder bore, short strokes rev better too.
Is that blower gonna be big enough for any of those combos, says its rated at 950hp?
I'd look at the 387 and build it for an 8K redline at least, why limit yourself on rpm when you're building it anyways?
Ideally whatever keeps the piston in the cylinder bore, short strokes rev better too.
Is that blower gonna be big enough for any of those combos, says its rated at 950hp?
I'd look at the 387 and build it for an 8K redline at least, why limit yourself on rpm when you're building it anyways?
How do you know what psi the blower will produce when you don't know the size of your engine? As ci goes up, your boost goes down, with the same amount of power (same amount of air).
What is the intended purpose of the vehicle the engine is going into?
What is the intended purpose of the vehicle the engine is going into?
Thread Starter
Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
Most people have an engine and add a (hopefully the right size) supercharger. This is the same exercise but in reverse.
Vortech publishes a Max Boost: 26 PSI and a Max Flow: 1,400 CFM so 17 - 18 PSI should not be difficult with the right size engine.
Once you have determined the optmimum displacement you try different pulleys to achieve 17 - 18 PSI of boost at red line.
I am running a Ti on my LS3 now and using a boost controller to limit boost to 9.5 PSI which results in 747 WHP @ 6,350 RPM. I can use the same concept to limit boost to 17 - 18 if that needs to be done.
If the displacement is too large I would not get to 17 - 18 PSI. If the displacement is too small it will hit 17 - 18 PSI too early and will waste the potential of the supercharger as I am doing now. I want to choose the displacement while I have the opportunity to do so.
Staging Lane
Joined: Aug 2022
Posts: 92
Likes: 8
Try to compare blower impeller speeds instead of boost pressure.
Im going 402 with my ecs 1500 (ti trim), with Ls9 heads. Somewhat of a similar build to yours. My ls3 took a **** pushing 800whp. My pulley setup was stock lower hub 8" (I believe) and 3.47 upper. I was around 13lbs. Going to keep it the same and see where she ends up. I'm either going to keep the same pulley, or pulley down.
At some point the blower becomes less efficient, and generates more heat. If I can recall if I did a 3.33 pulley with my stock hub, I'll be around 56k/57k RPM on the blower and was going to be around 14ish lbs of boost (over spinning.
Im going 402 with my ecs 1500 (ti trim), with Ls9 heads. Somewhat of a similar build to yours. My ls3 took a **** pushing 800whp. My pulley setup was stock lower hub 8" (I believe) and 3.47 upper. I was around 13lbs. Going to keep it the same and see where she ends up. I'm either going to keep the same pulley, or pulley down.
At some point the blower becomes less efficient, and generates more heat. If I can recall if I did a 3.33 pulley with my stock hub, I'll be around 56k/57k RPM on the blower and was going to be around 14ish lbs of boost (over spinning.
Last edited by MarshmallowMan; Aug 24, 2022 at 09:32 PM.
Thread Starter
Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
Try to compare blower impeller speeds instead of boost pressure.
Im going 402 with my ecs 1500 (ti trim), with Ls9 heads. Somewhat of a similar build to yours. My ls3 took a **** pushing 800whp. My pulley setup was stock lower hub 8" (I believe) and 3.47 upper. I was around 13lbs. Going to keep it the same and see where she ends up. I'm either going to keep the same pulley, or pulley down.
At some point the blower becomes less efficient, and generates more heat. If I can recall if I did a 3.33 pulley with my stock hub, I'll be around 56k/57k RPM on the blower and was going to be around 14ish lbs of boost (over spinning.
Im going 402 with my ecs 1500 (ti trim), with Ls9 heads. Somewhat of a similar build to yours. My ls3 took a **** pushing 800whp. My pulley setup was stock lower hub 8" (I believe) and 3.47 upper. I was around 13lbs. Going to keep it the same and see where she ends up. I'm either going to keep the same pulley, or pulley down.
At some point the blower becomes less efficient, and generates more heat. If I can recall if I did a 3.33 pulley with my stock hub, I'll be around 56k/57k RPM on the blower and was going to be around 14ish lbs of boost (over spinning.
The stock harmonic balancer diameter is 7.625" I think.
I have an Excel worksheet where I calculate the CFM output of the supercharger at various speeds based on Vortech's published maximum output numbers of 1,400 CFM and 28 PSI. Last night I calculated engine CFM at various RPM to do as you suggested.
Last edited by SteveJewels; Aug 29, 2022 at 04:51 AM.
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Staging Lane
Joined: Aug 2022
Posts: 92
Likes: 8
Op. Here's a link from correct to calculate the blower RPM and pulley combo. 7.8 is the crank pulley size for ls3. Should be v1-v7
https://vortechsuperchargers.com/pag...eed-calculator
https://vortechsuperchargers.com/pag...eed-calculator
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Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
I keep hitting dead ends.
Vortech spec's maximum capacity of the Ti in CFM but does not indicate the pressure at that rate.
Vortech spec's the maximum pressure the Ti and generate but not the CFM at that pressure.
You need to know CFM @ PSI to size the blower/engine combo. As restriction increases, PSI goes up and CFM goes down. As restriction decreases, PSI goes down and CFM goes up. Ignoring intake, head valve, and header flow, as you increase engine displacement CFM goes up and PSI goes down and as you decrease engine displacement CFM goes down and PSI goes up.
The sweet spot I am looking for is to be close to 18 PSI at redline. IF the displacement is too large I won't get to 18 PSI and if the displacement is too small I will hit PSI before redline and leave CFM and HP on the table.
For 374 CI at 17 PSI @ 7,500 the CFM is 1,750
For 387 CI at 17 PSI @ 7,500 the CFM is 1,811
This assumes 100% volumetric efficiency which doesn't happen.
Found a VE calculator, just need to get some MAF readings to start crunching numbers.
Why do I have 18 PSI as a goal? This is the point where the efficiency of the blower drops off. You can push it to higher pressure but you are not gaining much power because of the heat generated.
I talked with Doug from ECS at the Corvettes at Carlisle last week. He said the a guy making the most power a 1,500/Ti has it on a 427 but he is spinning the daylights out of the blower. I am going to keep it to around <60k.
Vortech spec's maximum capacity of the Ti in CFM but does not indicate the pressure at that rate.
Vortech spec's the maximum pressure the Ti and generate but not the CFM at that pressure.
You need to know CFM @ PSI to size the blower/engine combo. As restriction increases, PSI goes up and CFM goes down. As restriction decreases, PSI goes down and CFM goes up. Ignoring intake, head valve, and header flow, as you increase engine displacement CFM goes up and PSI goes down and as you decrease engine displacement CFM goes down and PSI goes up.
The sweet spot I am looking for is to be close to 18 PSI at redline. IF the displacement is too large I won't get to 18 PSI and if the displacement is too small I will hit PSI before redline and leave CFM and HP on the table.
For 374 CI at 17 PSI @ 7,500 the CFM is 1,750
For 387 CI at 17 PSI @ 7,500 the CFM is 1,811
This assumes 100% volumetric efficiency which doesn't happen.
Found a VE calculator, just need to get some MAF readings to start crunching numbers.
Why do I have 18 PSI as a goal? This is the point where the efficiency of the blower drops off. You can push it to higher pressure but you are not gaining much power because of the heat generated.
I talked with Doug from ECS at the Corvettes at Carlisle last week. He said the a guy making the most power a 1,500/Ti has it on a 427 but he is spinning the daylights out of the blower. I am going to keep it to around <60k.
But you may not hit 18psi though on a larger engine, as I'm sure you know psi is a factor of resistance of flow into the engine.
Big cubes mean less boost but more power generated.
My current LS1 has an S484 with all 3.5" intake piping into a 105mm TB into a Vic Jr intake, I have a hard time believing that 10 lbs. of boost into that engine will be equal to 10lbs into a typical 7875 setup with 2.5-3" piping and a stock intake.
Volume has to play a roll as well I have to imagine, if your blower moves the volume then the psi shouldn't matter.
I'm only running 10lbs. in my current setup but it sure feels faster than anything I've had up to this point and that must be because the volume of air the S484 moves relative to the boost or PSI.
I could be wrong on all this of course, grain of salt and all that lol.
Big cubes mean less boost but more power generated.
My current LS1 has an S484 with all 3.5" intake piping into a 105mm TB into a Vic Jr intake, I have a hard time believing that 10 lbs. of boost into that engine will be equal to 10lbs into a typical 7875 setup with 2.5-3" piping and a stock intake.
Volume has to play a roll as well I have to imagine, if your blower moves the volume then the psi shouldn't matter.
I'm only running 10lbs. in my current setup but it sure feels faster than anything I've had up to this point and that must be because the volume of air the S484 moves relative to the boost or PSI.
I could be wrong on all this of course, grain of salt and all that lol.
Thread Starter
Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
Unfortunately I don't know as I haven't dyno'd or raced it at the track yet but it'll blitz 150 mph on the street easily.
My old six speed car was 700whp and felt fairly quick but I think that's largely due to the manual, this thing feels faster, it revs to 7,500rpm like a rocket and just doesn't stop pulling.
If I had to guess its probably around 700 maybe 750whp, hoping it'll make 800whp at 14-15lbs. on pump gas is the goal.
If you intend on staying with the current blower permanently then you need less cubes as evidenced by dude over spinning the blower on the 427, some blowers become total heat pumps once they get pushed out of their efficiency ranges, can't speak to the Vortech.
If it were me I'd look at going 400 or 427, use the current blower, pulley it down until it makes whatever it'll make at 60K keeping it in that 74-75% efficiency range (probably 800ish whp as Marshmallow Man stated) and then if you want more, buy a bigger blower down the road.
I do know the smaller the pulleys get and the harder you lean on it, the more belt slip will become a issue, more cubic inches makes power production easier.
Not like it won't make good power either way.
My old six speed car was 700whp and felt fairly quick but I think that's largely due to the manual, this thing feels faster, it revs to 7,500rpm like a rocket and just doesn't stop pulling.
If I had to guess its probably around 700 maybe 750whp, hoping it'll make 800whp at 14-15lbs. on pump gas is the goal.
If you intend on staying with the current blower permanently then you need less cubes as evidenced by dude over spinning the blower on the 427, some blowers become total heat pumps once they get pushed out of their efficiency ranges, can't speak to the Vortech.
If it were me I'd look at going 400 or 427, use the current blower, pulley it down until it makes whatever it'll make at 60K keeping it in that 74-75% efficiency range (probably 800ish whp as Marshmallow Man stated) and then if you want more, buy a bigger blower down the road.
I do know the smaller the pulleys get and the harder you lean on it, the more belt slip will become a issue, more cubic inches makes power production easier.
Not like it won't make good power either way.
Thread Starter
Launching!
Joined: Sep 2008
Posts: 222
Likes: 46
From: Dayton, OH
I would like very much to do 400. With a 4.125" bore, a 3.75" crank would give me 400 and still could be spun pretty good. An 8k redline with a 7.5k shift point should give me some room to stretch it out.
If I don't hit the bullseye on displacement I would rather be a little over than under.
In related news, I found someone today to build a short block for me. He's backed up but it will give me a place to store the block while I figure out the rest of the puzzle.
Steve @RED said he would have the sleeving done sometime next month.
If I don't hit the bullseye on displacement I would rather be a little over than under.
In related news, I found someone today to build a short block for me. He's backed up but it will give me a place to store the block while I figure out the rest of the puzzle.
Steve @RED said he would have the sleeving done sometime next month.