Calculating boost from pulleys
Thread Starter
Joined: Jun 2005
Posts: 334
Likes: 76
Car: 91 Formula
Engine: 5.0 tpi slow
Transmission: WC t-5
Calculating boost from pulleys
Got a vortech t trim i picked up. Goin on a standard sbc. Its a 72 tooth crank pulkey and 29 tooth on the charger. Anyone know the aproximate boost range that should be? I know theres othe factors. Just tryin to get an idea
Thread Starter
Joined: Jun 2005
Posts: 334
Likes: 76
Car: 91 Formula
Engine: 5.0 tpi slow
Transmission: WC t-5
Re: Calculating boost from pulleys
Lower pulley looks to be 7.00 tooth to tooth. 7.53 overall lip to lip. charger pulley measures 2.86 tooth to tooth and 3.32 total lip to lip
Last edited by 2slow5.0; Jan 27, 2019 at 02:13 PM.
Joined: Sep 2003
Posts: 25,895
Likes: 429
From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: Calculating boost from pulleys
If i did this right, that pulley ratio means 7/2.86 is 2.447. Blower pulley is moving 13461 rpm at 5500 engine speed. Vortec t trim v1 is said to have a 3.45:1 ratio gear. So thats over 46000 rpm blower speed which according to map, thats 2-2.1 pressure ratio. Thats roughly 14-15 psi
Thread Starter
Joined: Jun 2005
Posts: 334
Likes: 76
Car: 91 Formula
Engine: 5.0 tpi slow
Transmission: WC t-5
Re: Calculating boost from pulleys
If i did this right, that pulley ratio means 7/2.86 is 2.447. Blower pulley is moving 13461 rpm at 5500 engine speed. Vortec t trim v1 is said to have a 3.45:1 ratio gear. So thats over 46000 rpm blower speed which according to map, thats 2-2.1 pressure ratio. Thats roughly 14-15 psi
Trending Topics
Thread Starter
Joined: Jun 2005
Posts: 334
Likes: 76
Car: 91 Formula
Engine: 5.0 tpi slow
Transmission: WC t-5
Re: Calculating boost from pulleys
Last edited by 2slow5.0; Jan 27, 2019 at 08:19 PM.
Joined: Sep 2003
Posts: 25,895
Likes: 429
From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: Calculating boost from pulleys
Eh thats not a bad cam to be honest. Usually with a blower i would spread the exhaust duration out some. I’ll have to see what shelf grinds are out. I know comp has that 224/236 cam for nitrous/blower
Thread Starter
Joined: Jun 2005
Posts: 334
Likes: 76
Car: 91 Formula
Engine: 5.0 tpi slow
Transmission: WC t-5
Re: Calculating boost from pulleys
im not skeered of gettin a custom grind. Im just pretty cam stupid. I am runnin short travel retro hydro rollers too if that matters. Im tryin to collect as many parts as I can before I tear it down
Joined: Sep 2003
Posts: 25,895
Likes: 429
From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: Calculating boost from pulleys
Yeah for a peak hp around 6000, a 224/230 on a 113 would work well. The 224/236 could also work which is comps blower cam
Thread Starter
Joined: Jun 2005
Posts: 334
Likes: 76
Car: 91 Formula
Engine: 5.0 tpi slow
Transmission: WC t-5
Re: Calculating boost from pulleys
I think 224/236 to peak out closer to 6500. Hogged our super ram with a welded/ ported base to step up to the 1206 port size. It’s seen 7k on the current setup. Obviously power doesn’t go that high but pulls to 6500 nice
Last edited by 2slow5.0; Jan 27, 2019 at 09:34 PM.
Joined: Sep 2003
Posts: 25,895
Likes: 429
From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: Calculating boost from pulleys
Yeah more rpm may be more boost too lol depends on a few things but good intercooling and running rich is key. Sneak up on the rpm to see where boost goes. Thats what makes blowers nice, boost curve is predictable and repeafable
Re: Calculating boost from pulleys
I believe with cog pullies, you divide the crank pulley tooth count by the blower pulley tooth count.
72/29=2.48 (pulley ratio)
X blower ratio
X engine RPM
= impeller speed
So 2.48 (pulley ratio) x 3.45 (blower ratio) x engine RPM (5500) = 47,058 impeller RPM
72/29=2.48 (pulley ratio)
X blower ratio
X engine RPM
= impeller speed
So 2.48 (pulley ratio) x 3.45 (blower ratio) x engine RPM (5500) = 47,058 impeller RPM
Joined: May 2008
Posts: 867
Likes: 1
From: pawtucket RI
Car: 1986 iroc
Engine: alum. head 350 supercharged
Transmission: 6speed
Axle/Gears: ford 9in 3.90 35 spline moser axles
Re: Calculating boost from pulleys
For some reason beyond me, the unit of measurement for cogs is metric. And to calculate impeller rpm, the same formula is used as with ribbed pulleys, except pulley diameter is not used. Instead, the number of teeth is used. The formula:
(Crank tooth #) x (engine rpm) x (blower step-up ratio) / (Blower tooth #) = Impeller rpm
(Crank tooth #) x (engine rpm) x (blower step-up ratio) / (Blower tooth #) = Impeller rpm
Senior Member
Joined: Jan 2008
Posts: 631
Likes: 7
From: Massachusetts
Car: 86' IROC
Engine: Supercharged 350
Transmission: T56
Axle/Gears: 3.45
Re: Calculating boost from pulleys
Last edited by 86CamaroDan; Mar 18, 2019 at 04:51 PM.
Thread
Thread Starter
Forum
Replies
Last Post
BHR
Engine/Drivetrain/Suspension Parts for Sale
6
Mar 27, 2015 09:20 AM
Paint-it-Black
Engine/Drivetrain/Suspension Wanted
8
Nov 30, 2007 05:42 PM
I-Roc with my Z
Tech / General Engine
12
Jan 21, 2005 03:34 PM