Injector Duty Cycle

[rob nolan]

I was out driving my car today and ran some test on the Direct Scan everything else seem to be working fine. On pump gas my injector duty was at 85% at 17 pounds of boost. My fuel pressure was at 43 psi and i am running 55 pound injectors. So is it about time to stept up to a set of 72s. As for the turbo i am running is a TE45a.

Thanks,
Rob

 

[Two Lane]

THREE CHEERS

Rob,

Good decision!

You'll never regret it and your motor will thank you!

 

[rob nolan]

Re: THREE CHEERS

Originally posted by Two Lane
Rob,

Good decision!

You'll never regret it and your motor will thank you!

Thanks, Two Lane did you go up to 72s also.

 

[rob nolan]

So do you think i might as well go for the 83s then or with the 72s.

 

[TurboTR]

72's, unless you plan to go faster than about 135 in the 1/4.

TurboTR

 

[azgn]

I don't think pump gas duty cycle means much....it'll try and add fuel when what you need is more octane or reduced timing or both

not saying bigger injectors is necessarily a bad idea but you haven't even approached the capacity of 55's at 17 lbs....my car makes better than 500 rear wheel hp and the duty cycle on the 55's is no where near 100%....what I found was, I needed more pump (volume)....a double pumper solved any fuel shortage

if you upgrade, you must upgrade the pump to at least a double pumper or those big injectors will become a huge problem

 

[rob nolan]

Originally posted by azgn
I don't think pump gas duty cycle means much....it'll try and add fuel when what you need is more octane or reduced timing or both

not saying bigger injectors is necessarily a bad idea but you haven't even approached the capacity of 55's at 17 lbs....my car makes better than 500 rear wheel hp and the duty cycle on the 55's is no where near 100%....what I found was, I needed more pump (volume)....a double pumper solved any fuel shortage

if you upgrade, you must upgrade the pump to at least a double pumper or those big injectors will become a huge problem

I've got a ATR double pumper on there now.

 

[Steve Wood]

Is the car running lean? It should not be with those injectors, double pumpers, and 17# of boost.

Duty cycle does not mean much without some means of measuring A/F.

 

[Chris McDade]

I went 10.63 with 50lbs injectors. I don't know what the duty cycle was. I just switched to 83's. If you plan on running 10.50's or faster than yes I would consider getting bigger injectors. The 55's will get you into the 10's easy.

You must have good fuel, good timming and slicks

Good Luck

 

[bruce]

Originally posted by rob nolan
I was out driving my car today and ran some test on the Direct Scan everything else seem to be working fine. On pump gas my injector duty was at 85% at 17 pounds of boost. My fuel pressure was at 43 psi and i am running 55 pound injectors. So is it about time to stept up to a set of 72s. As for the turbo i am running is a TE45a.

Are you going to be taking another leap in the engine department?.
You can run at 90% and still take the fuel pressure up some from where you are.

Limit Engineering shows 55s as the suggested size injector for the 45As.

 

[rob nolan]

Re: Re: Injector Duty Cycle

Originally posted by bruce
Are you going to be taking another leap in the engine department?.
You can run at 90% and still take the fuel pressure up some from where you are.

Limit Engineering shows 55s as the suggested size injector for the 45As.

Sorry guys my boost was at 19 psi not 17 psi hit the wrong button. No i'm more less done in the engine department. The only thing i need is a 3600 stall converter and the tranny freshin up thats about it. I'll take the fuel pressure up a little and see where i'm at from there. Thanks for all the replys

Rob

 

[azgn]

your combo is very much like mine........only differences are cam and I run 1.65 roller rockers.....in good air, you should be able to run 125++ and not push the duty cycle of 55's (my car weighs 3715)

 

[Two Lane]

Duty Cycle

Originally posted by Chris McDade
I don't know what the duty cycle was.

Chris,

Don't be embarassed by that...very few people have even heard of DC, much less how it's measured, its importance, etcetera.

Your latest set of injectors have given you a nice safety margin, and that's great!

 

[Kansas T]

Originally posted by azgn
if you upgrade, you must upgrade the pump to at least a double pumper or those big injectors will become a huge problem

Just curious what sort of problems your talking about. I'm looking into an injector upgrade aswell.

 

[rob nolan]

I just want to say thanks to everyone that has posted a reply back to me.
I'll go ahead and keep the 55s in there but i'll keep a close eye on it. Then i'll up grade down the road if need to. Just need to save $$$$ on freshing the tranny up and a converter.

Thanks,
Rob