Changing Injectors in FAST EZ-EFI version 1 throttle body

[Hoffbug]

Is there a video or online tutorial on how to properly change injectors on the FAST EZ EF
I throttle body?

[Hoffbug]

Are the injectors themselves just a interference fit with the O-ring ?
Is is as simple as just taking the Allen screws out of the fuel rail and removing it.. Then pull the injectors straight out?

[silver_bullet]

Been trying to find something..
. No luck so far...

[Hoffbug]

I've been thinking ahead that 39 lb per hour injectors might be beter suited to the little Olds engine. FAST sells them .They are high impedience LS7 style Injectors.

[silver_bullet]

I believe that you are on the right track!

[Hoffbug]

Anyone know the name of a real live person who works at Comp Performance Group is knowledgeable about FAST EZ-EFI? In general I seem to get "scripted" answers when I e-mail tech centers.

[SuperBuickGuy]

oh boy.... Plastic Fantastic 1 had EZ-efi - that was the biggest frustration.... my favorite from that time was locating the O2 sensor - no one wanted to commit where it should be located....

as for interference fit, I think so.... that's also how Holley TBI injectors fit in place... and they leak... a lot.

[anotheridiot]

we have been looking for the sniper injectors, no matter what place I contacted they just say to send it in. Cant believe nobody has started tearing this stuff apart yet.

[Hoffbug]

I tried to call CPG today to find out if the injectors that they retail are in fact direct replacements for the ez-efi version 1.

I waited 1 hour on hold. (I just put the phone on speaker). No one ever picked up.

[Hoffbug]

So my latest round of thinking has me at 50 lb per hour injectors..

If I'm very optomistic my little 218 CI engine should bee 200 HP.. so let's figure 225 to add some room.

225 HP x .5 BSFC = 112.5 lbs per hour. / 4 injectors = 28.125 lb per hr injectors.

EZ EFI wants you to run their Version I at 43 PSI.. The injectors are rated at 58 PSI so you have to convert.

43/58=.741. So if a 39 lbhr injector is rated at 58 you multiply by .741 to get the rate at 43psi.

39×.741 = 28.89 lbhr..

I think I might be better at going with 50 lbhr Injectors.

50× .741= 37.05 lb hr.

at 80% Duty cycle would be 29.64 lbhr.. a pretty good match for my high estimate of needing 28.125 lbhr to support my overestimate of 225 HP..

If I figured this right it should be way better suited to my small cube application than the 88 lbhr Injectors that come standard on version 1.


anyone see holes in how I'm figuring?

[Hoffbug]

The stock 88 lbhr Injectors are rated at 60 psi . If I convert to 43 PSI they become 60lbhr Injectors..I don't think they would ever get over 40% Duty cycle in my application

[Hoffbug]

In a previous email conversation ( yes Ive been at this project for a while) it was suggested by a FAST tech rep that I run the system at a lower pressure than they suggest in the manual... (30 psi instead of 43psi) to "keep it from running rich and over fueling ".

At the time this didn't make a lot of sense to me. But now it appears what they were suggesting was in an effort to lower the pound per hour rating of their standard injectors to try to better match the horse power level of my engine..

This whole idea of swapping to smaller injectors came from the fear that running an injector designed for operation at 58 PSI at a lowered 30 PSI might affect the operation and spray pattern quality of that stock 88lbhr injector . Let alone the almost zero duty cycle at part throttle.

[SuperBuickGuy]

now you hit on my biggest frustration with the EZ-EFI.... you cannot reprogram tables, what is on the system is what you get - thus when you tell it to add or subtract fuel via tuning via the O2 sensor - the system will take your "advice" then tell you to stuff it and do whatever it wants (programmed). I really question whether you'll be able to make it run correctly once you change injector sizes - it's a system for people who have a basically stock motor, great vacuum and want something that is plug and play - when you plug and play it won't play nicely because you're not within the narrow parameters of the design. While I believe you can get it running with those injectors, I think in the end you'll replace the computer with something you can program like an MS2. Once you get that running well, you'll move the MAF sensor off the throttle body and further upstream. Then you'll replace the throttle body with a stock GM TBI to resolve yourself of the leaks...

and I apologize for my view, but I'm pretty jaded at the EZ system because of its physical limitations and the fact that their customer service is about the same as before.... it is a good learning system, it really is, but it's limitations are pretty substantial.

[Hoffbug]

Your input is duly noted... I could just put a carb on it and call it a day. I broke the cam in with a 390 Holley that I still have.

It's my understanding that my version of EZ-EFI is upgraded from early releases...( an upgraded ECU with the handheld?)

There is an "other" provision to enter your own values for the injector quantity (4) and size/flow data. I'm hoping this would swing the fuel maps enough to get a ballapark to start the learning process.

Like everything with this project it's a ways out yet. But I'm getting closer and closer .

Sure would be nice to have a live knowledgeable person to talk to at FAST.

[Hoffbug]

Another half hour on hold today with no one picking up...Being tech center guy must suck.