How low can you go with high-flow injectors?

Skud · Aug 23, 2007

Allright,

So I should be getting my engine back in a few weeks from VT. It's a 302 stroker, stage 2 heads, stage 3 blower cams.

Now, the ultimate goal is a 2.6L Kenne Bell. I posted awhile back about how I'm probably going to need to step up to 24lb injectors. But - when I put the KB on I will have step up again.

So, my question is: Can I purchase an injector NOW that will live happily on my built N/A engine AND will work with the KB in the future?

I actually just bought a set of 60lb Siemens units for a pretty good price, so Ideally I'd like to get them to work, but I'm not getting my hopes up.. At all really.. But - If they would work at a really low pulse width, then that would be cool..

Thanks!!
Riley

showstopper2 · Aug 23, 2007

keep em in your closet..you will need a matching meter and thats still just way too much fuel on a NA car.

Red2000GT · Aug 24, 2007

You should try and be realistic about your ultimate power goals. Yes the 60's may be a good price but the Siemens are a low impedence set,right? So you're going to need an injector driver. There are high-impedence units on the market now up to 50 lbs/hr(maybe bigger but that's the largest i've seen). A good setup with 50's should handle about 600+ crank hp. Now considering that a KB 2.6 will run you about 7-8000$ up here I assume you won't be adding it very soon. If you don't plan on making more than 600 then the 50's and matching meter might be the smarter choice,and cheaper in the long run. They are pretty big but you can get by with them for the time being.

showstopper2 · Aug 24, 2007

the seimens 60's are high impedence and you can now get up to a 75lb from RC engineering high impedence.. thats what I have on my car now.

Skud · Aug 24, 2007

Yes, they are high impedance. I expect to be getting the KB in 6 - 10 months. I don't see why 60s would be any different then 50s . It's all in the tune from what I understand. I'd also rather run a 60lb injector at 60-70 % duty cycle than a 50lb at 80-90. That is if they both do the job the same as well as each other.

I mean, if I'm going to have driveability issues with the 60s then I'd have no issues stepping down to a smaller injector. I just don't know if I can use the 60s before I get the KB. The people who have 60s and 72s - hows your part-throttle, idle, and overall driveability? A blown car with 60s at idle and not in boost is going to be using the same amount of fuel as my car with no blower in the same conditions.

Riley

showstopper2 · Aug 25, 2007

first off do you have the matching meter for the injectors? if you don't then don't bother cause the car will have terrible driveability and you have too long to go that way. I have the 75's and my car is having the final dyno tune next tuesday(had a base tune to get the break in miles on the forged motor). there are definately compromises when running this big an injector. when the car is hot I have to start the motor with the gas pedal to the floor like its flooded. doubt this will go away even after the tune is done. right now the car loads up some at stop signs and I hope that will go away after the final tune is done. what Im getting at is it's no fun driving around with a big injector on a blower car at times so on NA it would be ALOT worse.

Skud · Aug 25, 2007

Ideally, you NEVER want to have a "matched" MAF. You just want a MAF that will not peg for your horsepower and then you work out its transfer function in the tune.

For example, the SCT BA2400, 2800, and all the stock Ford MAFs aren't calibrated to any specific injector. From the tune, the computer knows what voltage the MAF sends for a particular mass of air entering the engine. From that voltage the tune then knows how much fuel to add to maintain the correct AFR.

When you use a MAF matched to a specific size injector you're tricking the computer to reading a lower amount of air entering the engine. Since the computer still thinks it has the stock injectors (19lb or whatever) it will cycle the injector quicker and the end result is that adds less fuel.

When you properly tune a car you tell it that you have 60lb, 30lb or whatever injectors and your MAF transfer function is "xx" and the computer does it all itself.

The hot-start problems interest me though. I'm curious to see if your tuner can get that fixed.

Riley

y2k02 · Aug 25, 2007

The 60lbers will be fine with your setup. You will just have to have a tune to make it run right. My car drives like stock untill I get into it a little bit.

happydood2 · Aug 26, 2007

lol good luck with getting your motor back from vt engines in a few weeks. I waited months after they said it would be done before getting it. And then i find out they subed the motor out to a different company. Hope it goes well for you

Marks5.0! · Aug 27, 2007

LMAO at needing a matching meter, thats old school.

60's will be fine, with a good tune.

SaleenGT2001 · Aug 27, 2007

i'm running 60's and i only have 375hp.

its all in the tune, you'll be fine!

Marks5.0! · Aug 27, 2007

showstopper2 said:
first off do you have the matching meter for the injectors? if you don't then don't bother cause the car will have terrible driveability and you have too long to go that way. I have the 75's and my car is having the final dyno tune next tuesday(had a base tune to get the break in miles on the forged motor). there are definately compromises when running this big an injector. when the car is hot I have to start the motor with the gas pedal to the floor like its flooded. doubt this will go away even after the tune is done. right now the car loads up some at stop signs and I hope that will go away after the final tune is done. what Im getting at is it's no fun driving around with a big injector on a blower car at times so on NA it would be ALOT worse.

Any competant tuner should beable to take care of your hot start problem in your tune........

chrisconsin · Aug 28, 2007

I'm running 42lb injectors with bolt ons and cams, No power adder on my 4.6, and run just fine. so i would hope your built 5.0 motor would handle 60 with the setup your describing...
I'm jealous

Mach1_Marauder · Sep 2, 2007

showstopper2 said:
keep em in your closet..you will need a matching meter and thats still just way too much fuel on a NA car.

Now that's funny as heck!!!

Why are you giving tech advice?

How low can you go with high-flow injectors?

Skud

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