too high of duty cylce??

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May 16, 2022 | 11:03 AM

toddrparr

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too high of duty cylce??

I have a set of stock 6.0 (LY6) injectors that are the 27 lb model. The motor is lightly modified, LS3 intake, 224/238 .575/.600 cam and flat top (10.1) pistons, long tubes, nothing special. I am hitting 100% duty cycle at ~5000 Rpm on a full throttle pull, AFR target is 12.0 and it runs at 12.9 when I hit 100% duty cycle.

1st question - how much, if any, hp is this costing?
2nd question - I have a brand new set of DEKA 80s on the shelf, would that be overkill or can I tune for them?

Car will eventually have a turbo, currently collecting parts.

May 16, 2022 | 11:43 AM

AJT_LBA

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From: GA

well that fact that your tapping out at 5k rpms is hurting you a good deal. Maxing out your injectors is not good for the injectors or your engine. Put the 80s in, you can tune for their size.

May 16, 2022 | 12:33 PM

theunderlord

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From: Seattle

100% is not the plan man. 80% is probably the max most people will tell you is in the correct range.

May 16, 2022 | 01:06 PM

toddrparr

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thanks for the input!! I'm running the Holley Terminator and it looks like injector tuning is pretty straight forward. Probably better to put the injectors to use than have them sit on the shelf.

May 16, 2022 | 01:19 PM

theunderlord

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From: Seattle

Quote:

Originally Posted by toddrparr

thanks for the input!! I'm running the Holley Terminator and it looks like injector tuning is pretty straight forward. Probably better to put the injectors to use than have them sit on the shelf.

Yup, Holley makes it easy with putting the injector data in. Check out having them flow tested before you put them in too, cheap info to have in case one or more have issues. The last episode of Finnegan's Garage (called "Blew up the Hemi, now how do we fix it") has him down at a guys shop having his injectors flow tested and ultrasonic cleaned, and watching them talk about the problems they were having with tuning a couple cars because (unknown to them) they had some injectors not working properly.

I think he said the guy charges like 25 bucks per injector, which sounds cheap considering how hair pulling it is to try and get a car to run right with a mismatched injector. Especially when your entire car is running off of one O2 sensor.

Last edited by theunderlord; May 16, 2022 at 02:45 PM.

May 18, 2022 | 09:02 AM

beau.

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From: Jefferson, LA

Another vote to toss those 80lbers in. Since you have them, it's a no-brainer.

You're at or near the limits of your fuel system at 5k RPM. The higher the RPM, the less time your injector has to inject fuel into the combustion chamber. You can expand the capabilities of your fuel system (reduce duty cycle) by increasing size of injectors or increasing base fuel pressure. Since you have 80lb injectors, you should toss them in and start tuning/logging with them.

May 18, 2022 | 09:05 AM

toddrparr

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tossed in the injectors yesterday and did a heat cycle. The car is running at my targeted AFRs, at least in park... revs great! Haven't had time to drive it yet, I will report back.