Is it possible for very large oversize fuel injectors be to run at such a low duty cycle that it would damage the injectors, ECU, or engine?

I planned on new injectors for my supercharged build over this winter but now it seems my current 30lb\hr injectors may be failing after 70K miles of service.

I've had no problems at all running 30lb\hr injectors in my 305 while it's NA at all and if I need to buy new, I may as well get the larger injectors I will be needing with my new ProCharger in January.

I would like to go with Bosch EV14 in the 72lb\hr saturated size as I am planning up to 24psi of boost possibly on an F1 and want the head room so I don't get my duty cycle too high.

After tweaking the bin, would these be fine to run in my current engine until the build over the winter? I imagine so since I'm going to have to get it tuned to idle and run with no boost using these injectors anyway before I can tune for boost with them right lol. I think I just answered my own question lol.

Thanks!

 

I just ordered my AutoProm and I'll be ordering my WB o2 today as well hopefully.

Is anyone else running and have tuned for 72lb\hr saturated injectors? I want to pull the trigger on them today...

 

I have siemens 80 lb/hr saturated on my 401 so far and no problems. Motor hasnt be alive for long tho. Just fired it up last year end of summer and it was stored during winter.

I do not know if underdriving an injector could cause damage to the injector or ecm. I would have thought overdriving them would have a better chance at damage. I'm not sure how the ecm drivers operate.

I dont know what your building but 24 psi on an F1 on a decent bottom end is alot of power...may need more than 72's.

But I would try to tune them as is to see how they act. I have no real issue with 80's on my 401 at idle and part throttle and its not a radical combo. Its a very mild 401" motor. Boost makes it an animal. On motor i bet its a turd.

 

Yeah 24psi is just what I'm overbuilding the engine to handle, I really doubt I would ever see more than 18 or 20 in real world.

 

What are you building? Most setups on 18 psi will flat out haul.

 

my understanding of the injectors is that below a certain duty cycle, the on-off becomes erratic.
in other words, you can only go so low with your duty cycle.
where this is, i have no idea, but i cannot imagine that it would harm an injector to be run at low duty cycles...
if you are worried, you could run two injectors per cylinder, but thats a hassle

 

Just a little 305ci something, I just want it to be overbuilt. I'd cry if something blew up because I tried pushing it harder than it could handle because I was a cheap *** during the build.

 

I was thinking the same thing but I didn't know if it was really true and applied to only a 72lb\hr saturated (hi impendence?) injector or if that was an issue with the bigger ones (low impedence?)...

 

After speaking more with SouthBayFuelInjectors.com they more than assured me that a 72lb\hr injector would idle great as long as the tune is good, even on my little 305ci. I felt so good about it I actually ordered 85lb\hr in the end. I hope these are the last injectors I buy for years lol. Better safe than sorry lol!

 

Probably alittle overkill for a boosted 305 but they should work out ok.

 

If SouthBayFuelInjectors.com was recommending 72lb injectors for your boosted 305, I'd be leery of their tech. knowledge. 72's are good to around 800hp, and 85's around 1000hp. It might be possible to idle/cruise with those large injectors and a 305, but tuning will be a pain.

Orr uses 80lb injectors on his 401 beast. I'm using 60lb on a boosted 350. At idle/cruise I see very low pulsewidths (1.5-1.7) and with 12psi up top, I'm between 50-60% duty cycle. I'm curious what Orr's values at idle/cruise and wot are.

My point is I think you might regret the 85lb injectors and if it's not too late, I'd swap them for something smaller. Jon at fuelinjectorconnection.com was very helpful with providing me the right size injectors for my combo.

 

Right now i'm at 1.2-1.3 ms pulsewidths on my car which is pretty low for a 80lb injector. No idle issues at all. It will idle at 18 to 1 air fuel when the battery voltage drops but normal is around 14.5 when warm. Cold start is richer.
At WOT i've seen as high as 9.4 ms pulsewidth but car is running abit richer than I want to see.

I guess that calculates to about 1% duty cycle at idle and 40% or so at WOT at 5000 rpm. 44% or so at 6000 rpm. So i'm abit overkill for this car. It should be around 700whp on 15 psi now. But I'm not done pushing it. With a tune and abit more boost, maybe some other changes, I want over 800whp. That hopefully will push me closer to 50% cycle. I just wanted to be sure I would have enough injector for whatever I wanted to do with this car. Upgraded heads/cam and turbo for 900+hp will put me more in range of these things.

My regulator is also boost referenced so at 15 psi boost, i should be seeing an increase in injector flow. These injectors were rated at 80 lbs/hr at 3 bar pressure but i've seen others rate them at 83 lbs. At 4 bar, they are sold as 96 lb injectors I think for LSx cars. So I'm in the 92-96 lb injector range with boost and seeing 44% cycle duty peak. Not to bad.