Crank pulley effect on boost? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Lounge For casual talk about things unrelated to General Motors. In other words, off-topic stuff. And anything else that does not fit Section Description.

Reply
 
 
 
Thread Tools Search this Thread
Old 03-29-2007, 11:49 PM   #1
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Mar 2007
Posts: 91
Thanks: 0
Thanked 0 Times in 0 Posts
O 16581 72452 5 is on a distinguished road
Default Crank pulley effect on boost?

Figure you guys will be of some help, i'm doing a custom supercharger set-up on a BMW with an M62 purchased from here (which is mainly why i signed up).

I'm doing a junkyard set-up and couldn't find much for a pulley that would work, a Dodge Durango one practically bolted up, but it'* huge in comparison to the 9psi pullies.

Sooo, does the size of the crank pulley have a huge effect on boost?

I'm not looking to hit over 12psi.
O 16581 72452 5 is offline   Reply With Quote
Old 03-29-2007, 11:52 PM   #2
Senior Member
Certified Car Nut
 
Join Date: Mar 2003
Posts: 12,432
Thanks: 0
Thanked 0 Times in 0 Posts
J Wikoff is on a distinguished road
Default

Yes. It will affect how fast the belt moves, which will affect how fast the SC pulley turns, which affects boost.
J Wikoff is offline   Reply With Quote
Old 03-30-2007, 12:06 AM   #3
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

12psi?

What'* the compression ratio on that motor?
willwren is offline   Reply With Quote
Old 03-30-2007, 12:10 AM   #4
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Mar 2007
Posts: 91
Thanks: 0
Thanked 0 Times in 0 Posts
O 16581 72452 5 is on a distinguished road
Default

9.2:1

12psi would be the max i want, i actually want to keep it under 10, but with this pulley i doubt it'* an option, i know it'll effect boost, i want to know by how much though, a general ratio.

Say, 1 inch bigger diameter crank pulley = 1psi.

I know there'* the internal gearing factor and supercharger pulley size that come in to play, but i know there'* formulas for it. I actually have one, but i don't know the number for the internal gear ratio.

Is there a larger pulley junkyard available i could use? I'm not sure how it bolts to the supercharger, maybe something from say a water pump or alternator in a junkyard?
O 16581 72452 5 is offline   Reply With Quote
Old 03-30-2007, 12:15 AM   #5
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

9.2:1 with 12psi? BOOM.

Even with iron heads, and I bet it'* aluminum. KaBOOM.

We have no idea what your crank pulley diamter is, so we can't help you. Sounds like something for the BMW forums.

There is no internal gear change in a supercharger.

This section of the Forum is for 3800 supercharged or turbo (or nitrous) topics. I'll move your topic to the Lounge for you, but I can tell you that you're way in over your head on this one. Nobody in their right mind would stuff 12psi into a BMW with that compression ratio unless they had a 5k budget to START with.
willwren is offline   Reply With Quote
Old 03-30-2007, 12:40 AM   #6
Senior Member
Certified Car Nut
 
Join Date: Mar 2003
Posts: 12,432
Thanks: 0
Thanked 0 Times in 0 Posts
J Wikoff is on a distinguished road
Default

If you can tell us the effective diameter of your crank pulley and what pulley is on the SC, we might be able to guesstimate the boost. But we'd need to know your engine displacement as well.
J Wikoff is offline   Reply With Quote
Old 03-30-2007, 01:07 AM   #7
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Mar 2007
Posts: 91
Thanks: 0
Thanked 0 Times in 0 Posts
O 16581 72452 5 is on a distinguished road
Default

12psi isn't **** for a BMW'* engine. =\

4-500whp is usually what people shoot for on the stock engines, 600whp has been done a few times with head bolts.

Anyway, best i can do for measurements is a picture. I'm using this car for a learning experience, i have a spare motor tucked away for it. I've turbocharged a motor so i have the idea behind boost, but i want to learn the supercharger way, i've had alot of fun with this project so far. I'm asking about crank pulley relation because you guys seem like you'd know a little more about superchargers, BMW guys tend to stick to turbos (for good reason), but i felt like a different approach to forced induction for the learning experience, not the end result.

The pulley shown gives 9psi, the red line is roughly the size of the pulley i have installed.

O 16581 72452 5 is offline   Reply With Quote
Old 03-30-2007, 01:19 AM   #8
Senior Member
Certified Car Nut
 
Join Date: Mar 2003
Posts: 12,432
Thanks: 0
Thanked 0 Times in 0 Posts
J Wikoff is on a distinguished road
Default

Well over 12 psi is my guess. That red circle is a lot bigger then the crank pulley.
J Wikoff is offline   Reply With Quote
Old 03-30-2007, 01:19 AM   #9
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

Compression ratio and cylinder head material have a whole helluvalot to do with boost. I gaurantee you the guys doing this are doing alot more to their engines than you have planned, but seriously, I don't know jackshit. So don't listen to me. Sounds like you have it all figured out, so go for it.

In fact, just like everyone else here, it looks like you can make all your calculations on SC drive ratio from a picture of a crank pulley.

Can we get serious here now?
willwren is offline   Reply With Quote
Old 03-30-2007, 01:28 AM   #10
Senior Member
Certified Car Nut
 
Join Date: Jun 2003
Posts: 15,928
Thanks: 0
Thanked 0 Times in 0 Posts
BonneMeMN is on a distinguished road
Default

Cylinder head design, quench area, engine cooling systems, timing, how the boost is applied, are all important as well. If BMW guys are running 12 psi regularly without issues, then follow their advice. An m62 seems like more work though then other boosting methods, turbo, CSC, etc..
BonneMeMN is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Boost Control Solenoid Maintenance and Boost Control Actuator Test for low Boost* Toddster Trouble shooting + Test Procedures 0 03-21-2009 07:24 PM
Snowball effect much? repinS Lounge 24 03-23-2005 02:26 PM
KR's effect on MPG? Glasuan Performance, Brainstorming & Tuning 5 12-26-2004 12:32 AM
neat little effect......... robmpulse Your Ride: GM Pictures & Videos 4 11-14-2004 08:40 PM
The mechanical "domino effect" scottydl General GM Chat 6 06-06-2004 12:24 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 01:12 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.