What is the Max RWHP on stock injectors?
Registered User
Joined: Mar 2003
Posts: 676
From: palmview, TX (RGV)
Quick question for you guys that run the stockers over 350RWHP, what fuel pressure do you run and do you still use the stock pump? can the stock pump really support the extra fuel pressure needed to feed 400 RWHP like some of you guys mentioned? I thought the fuel pump would only support so much pressure, and that's why most guys dont recommend in-line pumps with the stock unit.
Registered User
Joined: Oct 2001
Posts: 584
From: NC Burlington
You must have increased the fuel pressure sky high or the numbers are standard and not SAE. Seen 430 rwhp on 28's that had the fuel pressure set to 60 psi and personally made 465 on 30's but 427 rwhp on 24's is a new one for me.
Frankly I like the post that said 370-390 rwhp in a six speed being time to start thinking about larger injectors but I've seen a numbers of cars making 400 rwhp or just a little over/under with 24lb injectors. In the "old days" replacing the injecters was never a thought so that's all we used was stock.
My 97 SS was making in the mid 390 range and the injectors went static around 6000 rpm. When we went to 30 lb injectors it didn't make any more power. In hindsite we probably could have just bumped the fuel pressure up some and the net result would be the same.
Hindsite is usually close to perfect, it's looking ahead that gets a little blurry.
Frankly I like the post that said 370-390 rwhp in a six speed being time to start thinking about larger injectors but I've seen a numbers of cars making 400 rwhp or just a little over/under with 24lb injectors. In the "old days" replacing the injecters was never a thought so that's all we used was stock.
My 97 SS was making in the mid 390 range and the injectors went static around 6000 rpm. When we went to 30 lb injectors it didn't make any more power. In hindsite we probably could have just bumped the fuel pressure up some and the net result would be the same.
Hindsite is usually close to perfect, it's looking ahead that gets a little blurry.
Administrator
Joined: Nov 1998
Posts: 71,116
From: Hell was full so they sent me to NJ
The 0.07 multiplier is a "rule of thumb" for getting the "ball park" size based on flywheel HP. It was derived by assuming a BSFC of 0.476 #/HR/HP and an 85% DC. A well-tuned engine, with efficient combustion chamber design can approach 0.45 BSFC and some people seem to get off on seeing how close to 100% DC they can push them. And all this assumes that the injectors are operating at the same fuel pressure they were flow rated at.
If you can do 0.44 on the BSFC and want to risk 100% DC, your up to 453 flywheel HP on a stock 24.9#/HR injector.
Remember also.... the dyno numbers you see are typically corrected to SAE or "standard" conditions. If you tested on a hot humid day, with a poor barometer, your engine did not actually produce the numbers on the dyno sheet. So you need to look at the UNCORRECTED dyno numbers when you are evaluating the injectors.
For the guy with the 93... your stock injectors are 22 #/HR, not 19.
If you can do 0.44 on the BSFC and want to risk 100% DC, your up to 453 flywheel HP on a stock 24.9#/HR injector.
Remember also.... the dyno numbers you see are typically corrected to SAE or "standard" conditions. If you tested on a hot humid day, with a poor barometer, your engine did not actually produce the numbers on the dyno sheet. So you need to look at the UNCORRECTED dyno numbers when you are evaluating the injectors.
For the guy with the 93... your stock injectors are 22 #/HR, not 19.
Thread Starter
Registered User
Joined: Oct 2002
Posts: 2,277
From: Orange Kounty, Kalifornia
I tried the formula but it is only based on Engine Size, Max RPM, and at WOT. The formula doesn't have a calculation for HP consumed (Fly or Rear).
https://www.camaroz28.com/services/calcs/pwcomp.shtml
If using stock 24# injectors, consensus seems to indicate up to 370-390 RWHP with the fuel regulator adjusted to higher PSI. Anything higher may max the Duty Cycle and incur potential injector lock up.
https://www.camaroz28.com/services/calcs/pwcomp.shtml
If using stock 24# injectors, consensus seems to indicate up to 370-390 RWHP with the fuel regulator adjusted to higher PSI. Anything higher may max the Duty Cycle and incur potential injector lock up.
Thread
Thread Starter
Forum
Replies
Last Post
dbusch22
Forced Induction
6
Oct 31, 2016 11:09 AM
stockssn2o
Parts For Sale
14
May 25, 2015 08:54 AM