Hey guys,

For a winter project I'd like to do a head, intake & cam on my 8.1. My biggest concern is duty cycle of stock injector. Since this is for my boat it will be running WOT quite a bit and I don't want to max out the injector. So my questions are how big are the stock injectors? What size injector should I get? And what duty cycle is a good safety marging. This H/C and intake combo has already resulted in 525hp and 600 ft lbs. Any guru's out there?

TIA!

 

I would buy the MSD injector plug ends 12.00 dollars and get the 60lb Motron injectors then you will have enough injector for almost anything you do and duty cycle won't even be a problem to worry about and if you do more mods later you won't have to buy injectors again. You will have to change the ends and put small spacers and longer bolts for the fuel rails or you can get the 8.1 marine injectors and hope the duty cycle does not become a problem.

 

Ive got the stock 8.1 truck injectors in my 5.3 and honestly I cant see them supporting 400+ safely. Even in my 5.3 they are around 100 duty cycle at 6200 rpms. I would go with crash and get the 60 lbers or at least the ever popular SVO injectors, you will need pigtails for just about any of them.
Ls1tech has alot of good posts and a sticky in the tuning section.
I talked to delphi about these injectors and they refered me to page 25 of thier catalog might give them a call and see if they have some that are a simple swap out instead of having to use pigtails

 

The 8.1 marine injector is bigger than the stock 8.1 truck injector. GM rates the marine injector @ 43 lbs but that is at GM pressure they are really a 36 lb @ 43 lb of fuel presssure and I think the stock 8.1 truck is like a 30 lb at 43 lb fuel pressure so maybe a marine injector is all you need.

 

Do you guys think I would see any benefit for the switch to bigger injectors on my truck given my mods? If so would the 8.1 marine injectors be sufficient. Sorry to hi jack the thread. Thanks

Alex

 

The 8.1 marine injectors would be good for you plus no mods are needed they bolt and plug right in.

 

I would have to disagree here. The injector will bolt right in, but you have to have your tune changed to accommodate them. You will gain nothing with bigger injectors unless you "need" more fuel. If your current injectors are supplying the required fuel and staying with in there suggested duty cycle, then larger injectors are not needed and will not benefit you, which I would say they are with your mods.

 

The 8.1 marine injector (43lbs/hr) should support that if its NA without much difficulty. They have been proven to 500 RWHP (aprx 575 to 600 FWHP) on FI. NA requires less fuel. If its forced induction then 60's might be needed.

 

I would check the duty cycle and go from there, thats why I said the marine injectors. If you don't need them then you just plain don't need them. Time for a little logging, the real way to know for sure.

 

So what I am hearing is that I may need them? I can have my buddy scan the duty cycle with his hptuners. Then have westers tune for them. Anyone know where to get aset of these 8.1 marine injectors? thanks

Alex