Forced Induction Superchargers | Turbochargers | Intercoolers

Boost question as it relates to cubic inches.....

Thread Tools
 
Search this Thread
 
Old Nov 5, 2016 | 10:38 AM
  #1  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default Boost question as it relates to cubic inches.....

The 454ci LSX that uses the 2300 SC'er makes 840 HP.

This engine:

If that SC'er was removed and dropped onto a 370ci engine.......same compression as the 454ci......same exact car otherwise.

Would it make more power at the same psi output?

.

Last edited by LS6427; Nov 5, 2016 at 11:42 AM.
Reply
Old Nov 5, 2016 | 10:47 AM
  #2  
lurker1978's Avatar
Staging Lane
 
Joined: Mar 2007
Posts: 55
Likes: 0
Default

No. Boost PSI is just a restriction measurement. If you ran the same pulley combo the smaller engine would make more boost . If you lowered the boost numbers to be equal the larger engine would make more power.
Reply
Old Nov 5, 2016 | 12:37 PM
  #3  
gtfoxy's Avatar
TECH Enthusiast
 
Joined: Apr 2009
Posts: 723
Likes: 4
Default

Then you have to look at the compressor efficiency at the different pressure ratio & air mass flow.
Reply
Old Nov 5, 2016 | 04:53 PM
  #4  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

Originally Posted by lurker1978
No. Boost PSI is just a restriction measurement. If you ran the same pulley combo the smaller engine would make more boost . If you lowered the boost numbers to be equal the larger engine would make more power.
So 7psi on a 454ci will make more power than 7psi on a 370ci...?

Its obviously true.......I'm just curious why people are saying that I should of built a smaller cube engine than my 390ci so I can make more power with a given size single turbo.

I plan to use the biggest baddest T4 flanged mid frame turbo, which people say is the S484. But why will it make more power on a 366ci than on my 390ci...?

Why are people saying I should have built a smaller cubed engine for boost...?

.
Reply
Old Nov 5, 2016 | 04:55 PM
  #5  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

There's nothing I can do now...my 390ci is in my car.......

I was hoping to make 1,200 RWHP through my 4L80E........T4 flange, mid frame.

I have 2 weeks to choose a turbo. It also must fit the Huron Speed V2 A/C single turbo kit.

.
Reply
Old Nov 5, 2016 | 04:56 PM
  #6  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

Its just odd that the 454ci is only on 7psi and its only about 400 HP away from my 1,200 RWHP goal. But with my 390ci I will need to run 19psi to make near 1,200 RWHP.......maybe 20-21psi.

.
Reply
Old Nov 5, 2016 | 05:03 PM
  #7  
lurker1978's Avatar
Staging Lane
 
Joined: Mar 2007
Posts: 55
Likes: 0
Default

The reasoning they say your engine is too big is the added exhaust flow of the larger engine will cause back pressure issues that will cause it to run out of steam earlier than that same turbo would on a smaller engine.
Reply
Old Nov 5, 2016 | 06:29 PM
  #8  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

Originally Posted by lurker1978
The reasoning they say your engine is too big is the added exhaust flow of the larger engine will cause back pressure issues that will cause it to run out of steam earlier than that same turbo would on a smaller engine.
Ok......well, I hope I can hit at least 1,000 RWHP with an S484, 91mm compressor/84mm turbine.

Thanks.

.
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-1

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-2

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-3

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-4

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-5

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-6

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-7

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-8

10 Camaros You Should Never Buy

 
story-9

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo
Old Nov 5, 2016 | 06:37 PM
  #9  
stevieturbo's Avatar
9 Second Club
 
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Default

All aspects of the build needs matched.

Say a GT3076 might make a very usable 600hp on a 2.0 4 cyl motor.

But that same GT30 on a 6.0 and it would be *****. Well..it might feel good from 1-3000rpm lol
Reply
Old Nov 5, 2016 | 07:46 PM
  #10  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

Originally Posted by stevieturbo
All aspects of the build needs matched.

Say a GT3076 might make a very usable 600hp on a 2.0 4 cyl motor.

But that same GT30 on a 6.0 and it would be *****. Well..it might feel good from 1-3000rpm lol
Yea, I see. I just didn't understand why my 390ci is gonna hurt me so much over a 370ci. I mean 20 cubes...doesn't seem like much.

.
Reply
Old Nov 6, 2016 | 04:17 AM
  #11  
stevieturbo's Avatar
9 Second Club
 
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Default

Originally Posted by LS6427
Yea, I see. I just didn't understand why my 390ci is gonna hurt me so much over a 370ci. I mean 20 cubes...doesn't seem like much.

.
It may not be much, it just depends where it may push the compressor etc on/off it's efficiency map etc But your original question was comparing a 454 to a 370. That is a huge difference

If you want a bigger motor then just go for the bugger motor...it's always easy to bolt on a bigger turbo later.
Reply
Old Nov 6, 2016 | 07:13 AM
  #12  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

Originally Posted by stevieturbo
It may not be much, it just depends where it may push the compressor etc on/off it's efficiency map etc But your original question was comparing a 454 to a 370. That is a huge difference

If you want a bigger motor then just go for the bugger motor...it's always easy to bolt on a bigger turbo later.
Thats the thing...I have the Huron Speed single turbo kit......the biggest turbo I can fit with this kit is the S484 with race cover.

This is where people are saying I would make more power if I had a stock cubed or a 370ci engine........

I was trying like hell to persuade Modular Turbo/CBR to make me one of their Twin Turbo kits.......but they can't.

.
Reply
Old Nov 6, 2016 | 07:19 AM
  #13  
stevieturbo's Avatar
9 Second Club
 
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Default

In general...bigger engines make power power. That really is a general rule.

But...a smaller motor might allow you to make more efficient use of the turbo....and another but, it will also require more boost to do so.

I've said it countless times, don't be afraid of boost, boost isnt a killer...but of course the engine package needs to be capable of running that boost. If fuel/CR etc allow it, wind then yes there is a chance that the smaller motor might get better results. But when there are so many variables elsewhere, there is no simple answer.

You could have a 390 with shitty heads and cam that will make less power everywhere than a 370 with a great head/cam package. So it's not all about engine size, it's very much about airflow.
Reply
Old Nov 6, 2016 | 07:48 AM
  #14  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

Originally Posted by stevieturbo
In general...bigger engines make power power. That really is a general rule.

But...a smaller motor might allow you to make more efficient use of the turbo....and another but, it will also require more boost to do so.

I've said it countless times, don't be afraid of boost, boost isnt a killer...but of course the engine package needs to be capable of running that boost. If fuel/CR etc allow it, wind then yes there is a chance that the smaller motor might get better results. But when there are so many variables elsewhere, there is no simple answer.

You could have a 390 with shitty heads and cam that will make less power everywhere than a 370 with a great head/cam package. So it's not all about engine size, it's very much about airflow.
Well I'll be running full time E85 so thats a plus. My cr will be at 10.8:1. I want to see what 18psi will make.

Also, I'm going to see what it makes with my terrible 1998 LS1 ported heads that only flow 304 cfm@ .600.

Then maybe I'll get new heads that flow much better to see what gains I can get.

.

.
Reply
Old Nov 6, 2016 | 12:21 PM
  #15  
lmt0705's Avatar
TECH Fanatic
15 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (7)
 
Joined: Apr 2006
Posts: 1,709
Likes: 3
From: buffalo NY
Default

Durability is an issue as well, that big bore means think cylinder walls
Reply
Old Nov 6, 2016 | 03:29 PM
  #16  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

Originally Posted by lmt0705
Durability is an issue as well, that big bore means think cylinder walls
Thin walls for what...the 454ci....?

.
Reply
Old Nov 6, 2016 | 07:44 PM
  #17  
JoeNova's Avatar
Restricted User
 
Joined: Mar 2014
Posts: 7,192
Likes: 109
From: Ohio
Default

Originally Posted by LS6427
Its just odd that the 454ci is only on 7psi and its only about 400 HP away from my 1,200 RWHP goal. But with my 390ci I will need to run 19psi to make near 1,200 RWHP.......maybe 20-21psi.

.
The 840 or whatever they rate that at is flywheel hp, not WHP. Its closer to 700 at the wheels, not 840.
Reply
Old Nov 7, 2016 | 06:11 AM
  #18  
ddnspider's Avatar
10 Second Club
20 Year Member
Liked
Loved
Community Favorite
iTrader: (26)
 
Joined: Aug 2004
Posts: 14,628
Likes: 1,778
From: FL
Default

Its about efficiency of the turbo. The smaller c.i. of the motor would put you in a more efficient area of a given turbo. That large of a c.i. motor and I would be running a T6 turbo, not a T4.
Reply
Old Nov 7, 2016 | 06:18 AM
  #19  
Old Geezer's Avatar
TECH Senior Member
iTrader: (3)
 
Joined: Jun 2004
Posts: 5,639
Likes: 71
From: GA, USA
Default

A visit to the compressor map[s] would help you see the effects......
Reply
Old Nov 7, 2016 | 03:12 PM
  #20  
LS6427's Avatar
Thread Starter
Banned
iTrader: (2)
 
Joined: May 2008
Posts: 11,289
Likes: 13
From: South Florida
Default

Originally Posted by ddnspider
Its about efficiency of the turbo. The smaller c.i. of the motor would put you in a more efficient area of a given turbo. That large of a c.i. motor and I would be running a T6 turbo, not a T4.
T6 on what....a 454ci...?

Or my 390ci?

Nobody builds a single turbo kit that retains A/C that fits a T6 turbo....A/C is a must for my car. So Huron Speed makes a T4 mid frame turbo kit which is what I have......

.

Last edited by LS6427; Nov 7, 2016 at 06:34 PM.
Reply



All times are GMT -5. The time now is 07:48 PM.

story-0
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-1
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-2
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-3
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-4
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-5
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-6
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-7
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-8
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-9
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE