Inject size formula? anyone remember?

[SITHV6]

a while back i was surfing around a few of our turbo buick friendly sites when i had stumbled onto a formula to figure out what size of injector you needed vs your horsepower output ....it had to do with number of cyliders you run with a few divisions and multiplication tables. i had written it down but had lost the formula...just wondering if anyone knew what i was talking about. it helped me realize my combo i was running required 72's and nothing less TIA

 

[ChrisCairns]

Originally posted by SITHV6
a while back i was surfing around a few of our turbo buick friendly sites when i had stumbled onto a formula to figure out what size of injector you needed vs your horsepower output ....it had to do with number of cyliders you run with a few divisions and multiplication tables. i had written it down but had lost the formula...just wondering if anyone knew what i was talking about. it helped me realize my combo i was running required 72's and nothing less TIA

http://www.rceng.com/technical.htm

(Remember to change the B.S.F.C. to .60 for our cars and multiply by 6 (cylinders) instead of 4 as used in the examples.)

 

[strikeeagle]

HP divided by 12 = PPH for each injector.

Example:

600 HP / 12 = 50 PPH

This assumes a BSFC of 0.5 - some claim conservation - but close enough.

 

[SITHV6]

OUTSTANDING!

Outstanding! thanks Chris and Strike! this will help out friends with their turbo applications, not to mention they measure their injectors in CCs heh.

 

[bruce]

What ecm are you running?.

Those equations are somewhat off, when you really try to impliment them, IMO. Since none of them account for Accleration Enrichment. Again, IMO, if you want to double the stock HP, then you'll want to double the injector size if your using a stock ecm. With some of the aftermarkets, they are more fudgible for AE.

There's more to EFI then just WOT. I've run 30s, 40s, 55s, and 60s all with stockish engines, and so far the larger the better. In the days of the old style chips were everything was just run static, the strategy was just set the injectors to stay on, and then regulate the boost to get the best performance. Trouble was the time period between operating normally, and goind static could be bad enough to blow headgaskets. As evidenced by some guys that have headgasket collections.

 

[JDEstill]

An alternative to those charts you could also use this little spreadsheet:
http://pages.prodigy.net/buickv6/CarStuff and pick quick inj pw calc.xls

It does not, as Bruce says, take into account any extra you might require for AE or similar. It should be pretty self explanatory, just put in your setup and pick an injector size to get you to 80% or so duty cycle.

John

 

[SITHV6]

Originally posted by bruce
What ecm are you running?.


dont know if the question was asked towards me...but i'm going to be using the stock ECM with modded drivers and Translator plus with extender chip.

 

[bruce]

Originally posted by SITHV6

Originally posted by bruce
What ecm are you running?.
dont know if the question was asked towards me...but i'm going to be using the stock ECM with modded drivers and Translator plus with extender chip.

Yes, I was asking you what your running.
Then I'd strongly suggest basing your injector size on your expected HP compared to stock. ie figuring the 300 PPH injectors were good for 245 HP, then to make 490 HP would take 60 PPH injectors.

Or just get 60s. They have excellent manners and there's some good chips out there for them. They also save doing the ecm driver swap. The 60 Extender's are really close to perfect in one car that I ran my WB on that was using them.

60s are also getting to where you might need a double pumper to keep them well fed if your using them to their max..

 

[SITHV6]

you sure 60"s?

Originally posted by bruce
Yes, I was asking you what your running.
Then I'd strongly suggest basing your injector size on your expected HP compared to stock. ie figuring the 300 PPH injectors were good for 245 HP, then to make 490 HP would take 60 PPH injectors.

Or just get 60s. They have excellent manners and there's some good chips out there for them. They also save doing the ecm driver swap. The 60 Extender's are really close to perfect in one car that I ran my WB on that was using them.

60s are also getting to where you might need a double pumper to keep them well fed if your using them to their max..

i pretty much maxed out my current combo of 40lbs. injectors with a 190ltr pump(hot wired) stock cam and TA49 stock ecm with KB hotflash chip and according to the popular sliding speed calculator my 1/4 mile speed was saying i was at 498HP at 3500 lbs. which pretty much pointed a finger at my fuel system was at its maximum. since then i had changed to a PTE 218/218 cam, forged 30+ pistons, billet main caps and was going to upgrade to 72's and a TE45A with an xp double pumper. my biggest concern at present was to go to a trans+ or ME-R...i have a plethora of other stuff to help support 600+ HP

 

[bruce]

Re: you sure 60"s?

Originally posted by SITHV6
upgrade to 72's and a TE45A with an xp double pumper. my biggest concern at present was to go to a trans+ or ME-R...i

A 45 can use the 83s if your wanting to actually use all the 45a has to offer.
If your wanting to go that fast, you might want to use both. The Tranlator dumps the stock MAF, and the ME-Rs have run into the 9s.