blower motor base compression ratio - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 08-23-2007, 07:12 PM
fbodyfreak's Avatar
Who loves burnt rubber
 
Join Date: Dec 2005
Location: TN
Posts: 30
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
blower motor base compression ratio

Can anybody tell me what the best starting compression ratio on a sbc with a 6-71. What is the lowest compression I can run and still be able to start the engine and run 91 pump gas. I understand boost pressures can be changed.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 08-23-2007, 07:48 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,788
Wiki Edits: 326

Thanks: 742
Thanked 956 Times in 806 Posts
If I were building one today, I'd build it 8.0:1 to 8.2:1, depending on the parts combination.
The more static compression ratio you build into the motor, the less boost you can run.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 08-23-2007, 08:24 PM
Registered User
 
Last photo:
Join Date: Jul 2007
Location: norcal
Age: 58
Posts: 762
Wiki Edits: 0

Thanks: 1
Thanked 2 Times in 2 Posts
i agree with techinspector, aruond 8-1 for street. basic rule with blowers is the lower the compression the more boost you can run and the more power you make.
with a blown motor you are shooting for the same compression as a na motor but with lower compression you have more volume at tdc that the blower can force extra AF into to bring the compression back up more AF= more power.
example:
10-1 normally aspirated
8-1 compression, blower raises compression 2 points= 10-1
7-1 compression, blower raises compression 3 points= 10-1
6-1 compression, blower raises compression 4 points= 10-1
4-1 compression, blower raises compression 6 points= 10-1
each one of these put more mix in the chamber than the one above it and produces more power than the one above it.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 08-23-2007, 08:31 PM
fbodyfreak's Avatar
Who loves burnt rubber
 
Join Date: Dec 2005
Location: TN
Posts: 30
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
blower compression ratio

what compression ratio would be optimal to use a decent amount of boost and still run 91 octane fuel
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 08-23-2007, 08:51 PM
Registered User
 
Last photo:
Join Date: Jul 2007
Location: norcal
Age: 58
Posts: 762
Wiki Edits: 0

Thanks: 1
Thanked 2 Times in 2 Posts
Quote:
Originally Posted by fbodyfreak
what compression ratio would be optimal to use a decent amount of boost and still run 91 octane fuel
read inspectors and my post above and figure it out, as we said a lot of guys run around 8-1. there is no such thing as an optimal compression and decent boost describes nothing, that like me asking "i have a glass of water in front of me, how much water do you think is in the glass??" read my post above until you understand it. pick a compression and use the blower boost to raise it up.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 08-23-2007, 09:26 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,726
Wiki Edits: 0

Thanks: 3
Thanked 346 Times in 343 Posts
You'll make the most power on pump gas with a 6-71 with the least amount of ignition retard using a 7.5:1 cr and 12lbs of boost.

Water injection will allow more compression,boost and timing on pump gas.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 08-23-2007, 09:57 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,788
Wiki Edits: 326

Thanks: 742
Thanked 956 Times in 806 Posts
See this chart from Blower Drive Service, it will give you the max boost for pump gas at a given static c.r.
For instance, at 8.0:1, max 8 lbs of boost.......
http://www.blowerdriveservice.com/techcharts.php
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may 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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
compression ratio compared to compression PSI squids1 Engine 14 12-28-2010 11:36 PM
Compression Ratio with 64 cc heads & Federal Mogul Sterling 345np Houman SS '70 Engine 9 05-01-2005 11:42 AM
Lower compression for blower Jim69Mustang Engine 6 01-13-2005 01:32 PM
compression ratio on blown sbc? Marcus Engine 2 09-19-2003 01:09 PM
Overheating?? & Question on blower ratio? chamz_16_2003 Engine 4 08-27-2002 01:05 PM


All times are GMT -6. The time now is 01:58 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.