402 stroker injector recomendations?

[Bruce Melton]

I have a LS2 402 on order and want to be ready with some "safe" sized injectors. The motor should make ~ 550 FW. I ran SVO 30s on my old (now deceased) head and cam (420RW) motor at ~80%.
I like Bosch Ford injectors, do we think the Ford 42s (or 36s>43#) which make ~50# would be a good safe choice? Or is there a better choice? I will be running MAF, LS6 intake and 236-242 cam..

Appreciate your thoughts,

Bruce

[Tordne]

I was plannign on running FMS 42lb injectors in the Iron block 408 I was going to order (sad story)

42's are pretty big for a NA motor.

Side question. Don't you recon the 402 will flow more than 511 grams/second of air, and therefore max out the MAF?

[Bruce Melton]

I think it will be close on MAF but I am running a LS6 with ported TB not a FAST and I have not heard of that being issue. Gives me something more to worry about though, Thanks.

[superls1]

You probably already know this:

BSFC x HP / # of Injectors = Lbs/hr rating of injector @ 100%

BSFC - Brake Specific Fuel Consuption; it is a measure of how 'efficient' the engine is at converting fuel to HP; the lower the number, the more 'efficient' the engine is; I use .45 for the LSx engines
HP - use crank HP (estimate if not exactly known)

So, assume 550HP at the crank (or 468RWHP assuming ~15% drivetrain loss):

.45 x 550 / 8 = 30.93 lbs/hr

Remember, this is 100% duty cycle, and you want some margin of safety. So, shoot for 85% max duty cycle. Therefore, divide by .85

30.93 / .85 = 36 lbs/hr

Let me know if I can help.

FYI, the C6 Z06 has ~40lb/hr injectors. I have used both the Ford 36# (43 @ 58psi) and the Racetronix 42# (48 @ 58psi) in some 402 applications. I have good results with both.

[Bruce Melton]

You probably already know this:

BSFC x HP / # of Injectors = Lbs/hr rating of injector @ 100%

BSFC - Brake Specific Fuel Consuption; it is a measure of how 'efficient' the engine is at converting fuel to HP; the lower the number, the more 'efficient' the engine is; I use .45 for the LSx engines
HP - use crank HP (estimate if not exactly known)

So, assume 550HP at the crank (or 468RWHP assuming ~15% drivetrain loss):

.45 x 550 / 8 = 30.93 lbs/hr

Remember, this is 100% duty cycle, and you want some margin of safety. So, shoot for 85% max duty cycle. Therefore, divide by .85

30.93 / .85 = 36 lbs/hr

Let me know if I can help.

FYI, the C6 Z06 has ~40lb/hr injectors. I have used both the Ford 36# (43 @ 58psi) and the Racetronix 42# (48 @ 58psi) in some 402 applications. I have good results with both.

It seems if you get the LTFTs in the -5 range it runs the injectors beyond the equations, or is that just my experience? My old motor sucked up all the SVO 30s could pump @80-85%. If the LS7 is using 40s it seems 43 would be damn close? The stock LS2 is now 32 or 33# I think.
Better safe at 50 (42s)???
BTW -I almost had a nervous breakdown over cam selection.

[superls1]

BTW -I almost had a nervous breakdown over cam selection.

What's the lift and LSA?

RE the injectors: There have been a few posts lately of people talking about injectors being too big. Obviously, if you are trying to fill a dixie cup you don't want to do it with a fire hose. But, it seems that most people can tune 40-50lb/hr injectors without much issue.

[Bruce Melton]

What's the lift and LSA? 238-242/605-610/113 LS-X

RE the injectors: There have been a few posts lately of people talking about injectors being too big. Obviously, if you are trying to fill a dixie cup you don't want to do it with a fire hose. But, it seems that most people can tune 40-50lb/hr injectors without much issue.

Well I would rather have them be too big than get heavy on the duty cycle. The problem is there is such a huge gap in pulse width between idle and WOT @7K the low end will be hideously out of control. This engine is designed to favor torque over hp but as a road race engine it will see a fair amt of sustained high rpms.
I have a guy holding a set of 36s for me but--

[redhardsupra]

according to my own spreadsheet:
http://redhardsupra.blogspot.com/200...readsheet.html
a 408 running at 13:1AFR and 7000rpm, will do just fine with 42s running at 58psi, leaving you with a nice margin of error.

[Bruce Melton]

according to my own spreadsheet:
http://redhardsupra.blogspot.com/200...readsheet.html
a 408 running at 13:1AFR and 7000rpm, will do just fine with 42s running at 58psi, leaving you with a nice margin of error.

Did I do this right? I assume you meant SVO 42@~50#?
Thank you, nice spreadsheet!

[redhardsupra]

yup, about right. this is for ballparking not precision work anyway, especially that injectors only come in certain sizes