Go Back   Third Generation F-Body Message Boards > Tech Boards > TBI
Sign in using an external account
Register Forgot Password?

TBI Throttle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.

Welcome to ThirdGen.org!
Welcome to ThirdGen.org.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!


Reply
 
Thread Tools Search this Thread
Old 04-16-2005, 09:20 PM   #1
Senior Member
 
Join Date: May 2001
Location: SE TN
Posts: 364
Car: 85 TA, 90 Formula
Engine: Stock 305 TPI, 302 4bbl TBI
Transmission: Stock 700R4, T-5
Axle/Gears: 3.27 BW, 4.27 Dana 44

Classifieds Rating: (1)
425hp TBI injectors

Could someone comment on my calculations. This is from info I have collected from various sources including the TGO boards. I chose numbers that lean towards a worse case as far as psi requirements.

1. (425x.5)/(2x.85)=125

425=hp
.5 =BSFC
2 =# of injectors
.85 =duty cycle
125=injector size required @ 13psi


2. (125/80)x(125/80)x13=31.7 psi
(125/90)x(125/90)x13=25.1 psi

This is the desired inj.(125) divided by available inj.(80 or 90), squared and then multiplied by original psi to yield required psi for the available injector.

With 30psi being the often stated limit, 425hp requires the 90s. Working the number back for the 80s would limit them to 413hp and 464hp for the 90s.
Breazlan is offline vBGarage Page   Reply With Quote
Old 04-17-2005, 03:31 AM   #2
TGO Supporter
 
Join Date: Jan 2003
Location: Australia
Posts: 492

Classifieds Rating: (0)
I created this excel sheet a while ago, you may find it useful...

http://users.bigpond.net.au/ben_p/co...ctorsizing.xls
ben73 is offline vBGarage Page   Reply With Quote
Old 04-17-2005, 10:12 AM   #3
Senior Member
 
Join Date: May 2001
Location: SE TN
Posts: 364
Car: 85 TA, 90 Formula
Engine: Stock 305 TPI, 302 4bbl TBI
Transmission: Stock 700R4, T-5
Axle/Gears: 3.27 BW, 4.27 Dana 44

Classifieds Rating: (1)
Good, the stuff I ran into is good info then.

Do you have a calculation that describes idle quality? I have seen on here that bumping up the injectors hp capabilty (size and pressure) has an adverse effect on low end fueling.

Also, any formula for injector longevity per increase in psi?
Breazlan is offline vBGarage Page   Reply With Quote
Old 04-17-2005, 04:06 PM   #4
TGO Supporter
 
Join Date: Jan 2003
Location: Australia
Posts: 492

Classifieds Rating: (0)
I run my 90 lb/hr injectors at 18psi, i suspect they will be at 20psi when i finish tuning. The PW at idle is short, but still controllable. There's a short discussion on that topic here: http://www.thirdgen.org/techbb2/show...hreadid=290728

I can't comment on injector lifespan, but i haven't had a problem..
ben73 is offline vBGarage Page   Reply With Quote
Old 04-17-2005, 07:03 PM   #5
Senior Member
 
Join Date: May 2001
Location: SE TN
Posts: 364
Car: 85 TA, 90 Formula
Engine: Stock 305 TPI, 302 4bbl TBI
Transmission: Stock 700R4, T-5
Axle/Gears: 3.27 BW, 4.27 Dana 44

Classifieds Rating: (1)
You probably will have an easier time controlling idle with a 383 as it natuarally can use the fuel. Imagine a smaller engine that needs your level of top end fuel trying to idle on your setup. Would you say it would be difficult or are you not that close the the limit with the 383? Going to 20 psi should make it worse too.
Breazlan is offline vBGarage Page   Reply With Quote
Old 04-17-2005, 09:23 PM   #6
Senior Member
 
Join Date: Jan 2002
Location: Red Deer, Canada
Posts: 812
Car: 89 Shortbox
Engine: 350 Vortec
Transmission: 700r4

Classifieds Rating: (0)
Ran my 90# injectors @ 20+ psi, couldn't get great performance though, put on a 750 cfm carb (jetted down) and it was like bolting on another 75hp.
__________________
1989 1500 Truck SB, 350 ci, 750 cfm Performer (RIP ported 454 tbi), Comp 222/226 @ .050 with .500 lift 114 deg LSA, 10.7 to 1 CR, Ported Vortecs, Flow Tech Headers, Edelbrock Air-Gap RPM Intake, 1.6 rollers, Custom UVEPROM, Walbro 255 pump, MSD Ignition, Dual 3" Dynomax, 3.73 posi, 700r4, Stage 2 Shift Kit, Vette Servo, cheap 3000 stall.

Shooting for high 13's (mid 13's corrected)

2001 Dodge Cummins 3/4 SLT Leather,Loaded, 39" mudders, 525hp & 1200 ft/lbs.

2001 ZR2 Blazer Loaded, K& N and chip. 31" mudders.

1989 Shortbox
Low C1500 is offline vBGarage Page   Reply With Quote
Old 04-17-2005, 09:23 PM
ThirdGen
1992 Camaro




Paid Advertisement


Reply

Go Back   Third Generation F-Body Message Boards > Tech Boards > TBI

Tags
425hp, formula, injector, injectors, size, tbi, upgrade
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

 


1982 Camaro '82 || 1983 Camaro '83 || 1984 Camaro '84 || 1985 Camaro '85 || 1986 Camaro '86 || 1987 Camaro '87 || 1988 Camaro '88 || 1989 Camaro '89 || 1990 Camaro '90 || 1991 Camaro '91 || 1992 Camaro '92


All times are GMT -5. The time now is 12:34 AM.


Powered by vBulletin® Version 3.7.5
Copyright ©2000 - 2012, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.5.2
All content copyright © 1997 - 2012 ThirdGen.org. All rights reserved. No part of this website may be reproduced without the expressed, documented, and written consent of ThirdGen.org's Administrators.

Emails & Contact Details