Hi guys, I just took 24 lb/hr Rochester Multec II injectors out of my 6E MAF setup and replaced them with Ford-application Denso 24 lb/hr. I had 24 as my injector constants. The car runs so rich now with the Ford Denso's that is smells like a lawnmower. I always see debates on whether or not the Ford 24 injectors are rated at 24 @39.5 psi, or 24@43.5 psi. Can anyone give me a real answer? Also I seem to remember that someone flowing the "24" Multec IIs found they actually flowed more like 22.5 @ 43.5.

Do I need to recalculate the injector constant for the Ford/Denso 24's based on the fact that, at 43.5 psi, an injector rated 24@39.5psi is 26.43 psi? This would make sense why the car runs soooo rich now switching to the Ford/Denso's?

 

I calculate the change to be about 25.1 lb/hr. I think thats what I used in my tuned port setup with the ford 24lb blue-tops.

 

25.2, you're right. I'll try changing the constant and see if it doesn't load up so bad now. I can't believe this makes such a difference. Then again, I do recally the Multec II 24's not flowing anyhwere near advertised when someone tested them.

 

It turns out I'm actually way lean with the Ford 24s. Huh. They are off ebay and supposed to be only a year old. They are showing way low O2 values and the car runs okay, but crappier than it did with the Multecs. Multecs going back in. What the hell?

 

Forget the calcs.

They are rated at 43.5

I have verified this in over 6 cars personally.

Stock to stock a IC of 23.8 puts BLM almost dead on 128 range (+-3)

Also when mine were cleaned and flowed, at 43.5 they were rated very very close to a true 24#.

later
Jeremy

 

3.8 thanks. By the way, where did you get your injectors cleaned and flowed, and what did it cost?

 

Your o2 sensor isn't going south on you is it, maybe its reading lean and the ecm is trying to do its job riching it back up to stoich. You dont have a vacuum leak do you, might have unplugged or cracked a line while doing the injector swap.

Anyway, just some thoughts,

 

Everything on this motor is very low mileage, only a few thousand miles. No vac leaks. O2 sensor is a heated genuine delco sensor that is new. I tried the Multecs and the Fords back to back and got vastly different results. This gives me pretty good reason to suspect the injectors. I just tried richening the Ford injectors up significantly by bringing the inj. constant down and bumping the MAF table up. This seems to have helped a lot, but I don't understand why the Multec II 24 lb injectors don't need this compensation. I think I'm going to put the Multecs back in and send the Ford injectors out to be cleaned and flowed.

 

All Ford injectors are rated at 39.5psi, it even states that in the Ford Racing catalog 9the catalog rounded off to 40psi). I work at Ford & double checked this fact with a coworker in fuel systems, he confirmed that Ford injectors are rated at 39.5psi. Therefore, the correct injector constant is 25.2#/hr if this is a perfect world.

You bought your injectors off of Ebay, who knows what you really have. This is another horror story of Ebay parts,,, NEVER buy electronic parts from an individual on Ebay, only if it is a reliable company stating its a new part.

 

doc, I agree ebay stuff is really sketchy sometimes. For the price, I couldn't pass these up. The part # on them shows they are indeed 24 lb/hr 1993-95 Lincoln DOHC 4.6 and Mustang Cobra 4.6 DOHC. They run like they are 19s. LOL. I don't know what the hell the problem is. I'm going to send one out to a guy who will clean, flow it and check the pattern for $15. If it checks out normally after cleaning I'll send the other ones in. Otherwise I'll get the Multec IIs cleaned and flowed. I know they work fine, they just seem to have a couple loud ones.

 

Ford doesnt make the injector, bosch does. Bosch rated them at 43.5

I had flow sheets from two sets I had cleaned(rich at Cruzin) and friend did the third(at Precision turbo and engine). All came in at 24#(+-.5 depending on the exact set) and which test fluid spec used.

Was at a 43.5 psi.

Maybe the mystery will never end, but after having seen three flow sheets on them and using them in prolly 10-12 cars total, its enough for me.

later
Jeremy

 

Rich cleaned and tested my SVO 30's at 43.5 PSI and they flowed out at 30.5 lb.hr, so I have to agree with Jeremy. Especialyl since someone sent Rich some other ones for testing as well - and they all matched their flow rating at 43.5 PSI ("one bar")