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cammed, geared, and blown
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Discussion Starter #1
After a quick search, I still have a question.
I will be installing a KB 2.6h in the near future...I have it ready and waiting.
I have 39# injectors that came with it (the blue Cobra ones), but I'm thinking I may need larger ones for my setup.

Mods:
long tubes
4.10 gears
comp 127500 spr cams/springs/phaser limiters
KB 2.6H with gt500 tb, ported inlet, 4" air intake tube, intercooled, 8 rib.
KB boost-a-pump
should be around 9 psi...stock short block and all.
Goal is around 460-480 rwhp.

The only reason I'm considering larger injectors is that my tuner was a little concerned that 39# would be maxed out.
Any input is appreciated.
 

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They have fuel injector size calculators. They take into consideration displacement, expected hp., RPM's, etc. you shouldn't exceed 80%-85% duty cycle. That is maxed in my book.
 

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KILLER
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1,722 Posts
I used 39#'s for 460hp/15lbs boost and my tuner didn't say I was close. With a boost-a-pump you should have no issues.
 

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cammed, geared, and blown
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Discussion Starter #4
They have fuel injector size calculators. They take into consideration displacement, expected hp., RPM's, etc. you shouldn't exceed 80%-85% duty cycle. That is maxed in my book.
Ok...link?

I used 39#'s for 460hp/15lbs boost and my tuner didn't say I was close. With a boost-a-pump you should have no issues.
Thanks!
 

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When I originally installed my Whipple at 10psi Kevin MacDonald at JPC Racing told me to order it without the injectors (39's) and to go with GT500 injectors which were 52lb. He said there were about 10 good reasons to use the 52's. Kevin is one of the top 3 valve tuners in the world.
 

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KILLER
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Heres a good chart that shows the # required for a N/A and S/C motor. It says you would need a 42# for 448hp on a S/C'd motor and still be at 80% DC. Going off the chart, 39#'s will work, but you will be close to maxing them.

Fuel Injector Sizing and Horsepower Limits

 

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Just go with 63# injectors, if you decide to build the motor down the road you won't have to replace them. Plus there the same price, that's what I did when I was putting down 525 rwhp
 

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I should data log my injector duty cycle. I'm running 34#'s and producing 480 at the wheels through an automatic which is almost 600 hp at the crank. I think I probably am on the edge of safe if not over the limit.
 

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cammed, geared, and blown
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Discussion Starter #10
What brands of injectors should i be looking at? Is there a down side to going with 60# if 52# is adequate, like driveability issues or fuel pump limitations (i do use a bap)
 

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There's no down fall to having bigger injectors, like I said they could come in handy down the road for u. Driveability will be the same as if you had 39's , I had them in for almost 2 years with zero issues.
 

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cammed, geared, and blown
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Discussion Starter #12
^ thanks. Your car is a beast! Might need to update your 1/4 time lol.
 

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Haha thanks. It will be a while before I can update that lol I gotta get it running first
 
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With the larger injectors it just takes a more experienced tuner to deal with throttle tip in issues. There are tables involved with the software and the pcm that go into much more detail than a lot of tuners are aware of.
 

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Having too big of an injector can cause tuning complications in that if your not using the full range of its capacity it makes it more sensitive to minor adjustments. this may make it more difficult for your tuner to dial it in. But I think if you don't go way overboard you shouldn't have an issue.
 

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cammed, geared, and blown
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Discussion Starter #16
I'm thinking 60# are in my future...
What brand of injectors are you supercharged guys using?
 

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Sieman Deka 63lb USCAR High Imp Injectors from lethal performance. $399

I ran these on my old setup with zero issues.
 

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cammed, geared, and blown
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Discussion Starter #19
I ordered the Sieman Deka 60lb injectors. Found a deal....$350. I put my 39lb cobra injectors in the classifieds if anyone is interested.
Thanks everyone.
 

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Will your wire connectors hook right up or will you need adapters?
 
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