Fuel Injector upgrade
 

I've been advised to upgrade from my original 550cc Primaries to 850s all around because of the mods to this new engine I have. The injectors are a different overall length and it was suggested to me that I may need to add a washer or some kind of spacer to the 850s to fit properly in the Primary spot.
Can anyone tell me if this is true or not? And if so, where would this spacer have to go?
It's Sunday and I'd like to get things back together without waiting until Monday to talk to the shop that built my engine.
Thanks...

Do not use any kind of washer or spacer. The rail needs to be milled down for the injectors to fit. This needs to be precisely done or they will leak. There are several vendors selling the modified rails. You will also need to re tune the car.

Yeah, I was going to suggest that spacers aren't enough because the diameters are different at the o-ring.

Dave

We used a belt sander to take it down evenly about an .125 inch. Came out very even and clean. You can do it slowly and take quick breaks to check how the injector seats with the o-ring unitil it seals good. Only takes a few minutes...

Say what? On the injector or the aluminum?

In either case, you will not even come close to the proper surface finish and tolerances to make the o-ring seal reliably.

I see injector o-rings like brakes. Darwin sorts out the cheapskates.

Dave

what are your mods that are requiring 850cc primarys?
what ecu are u running?

Thanks for the input, but has anyone actually done this?

:lol: :lol: That is great stuff right there..... :lol: :lol:

Anyways I was also going to ask why you wanted to go with 850cc primaries. Another, maybe better option would be for you to keep the 550cc primaries (maybe get a new set or have yours gone through to insure they work properly) and go with a new rail and 1600cc secondaries. That will suppourt up to 400rwhp with a good suppourting pump. Plus it will be WAAAAY easier to tune than 850 primaries.

Surface finish? Tolerances? C'mon Degeesaman... it pretty easy stuff.:) Just shave down the aluminum rail a bit (how did you think I was saying injector?) I even pressure tested the fuel system over 75psi and it was fine. And believe me I'm not a cheapskate (spent over $60k on my ride and I do most work my self ), it's just that it's too easy to do this on your own.

For anyone who wants to picture what is going on here: The stock primary rail is a two a piece design. One part is what the injectors sit in and the injector o-ring seals at the bottom of this piece. The other part is a sorta cap that goes over the injectors and holds them down with two bolts to keep the injectors sealed. All your doing is giving the shorter 850cc injectors more room to go down in the first piece and seal well by taking a bit off the top of the rail.

Whoever wants to do it on their own needs to make sure you don't go more than an .125 because if the injector sits too low the fuel flow won't fully be flush with the side feed of the injector. Again, a steady hand and a sander will do it in a couple minutes. And actually the finsh was super smooth and straight like it was made that way.

If anyone is NOT comfortable shaving down the rail a bit on your own, then send it out.

Edit: By the way, I would not do two O-rings (raising the injector), it will cause another point of possible failure.

I just looked up pics of the injectors and I was mistaken. I thought the secondary and primary had different sized o-rings and different diameters at the o-rings, so that your modification was somehow related to the diameters. Are the o-rings set at the same distance between them?

Now I understand that you're simply shaving down the rail to allow the secondary to sit at the proper depth. Obviously that's not dangerous to do with a belt sander.

Dave

For a second I thought maybe I was being a cheapskate...haha. ;)

Btw, for anybody that wants to send it out, I believe Garfinkle was doing these for like $5 back in the day. Worth a shot asking him...

Thanks a lot everyone. Some good information there.
It was suggested to me as an afterthought as the car has been difficult to tune since the new engine install. First it was a surging idle, then after some tuning and diagnostics the idle stabilized but the engine would stall out at times and be reluctant to start. Fuel Px Reg. was suspect, as were the original injectors. During the engine change I had the injectors cleaned and checked and they tested fine. But there was a suspicion that they were perhaps opening slowly, or closing slowly or late, or who knows what. 15 years and 93,000 miles of baking on a hot engine raised enough doubt to warrant replacing them. Better late than not at all.
I wanted to upgrade to 850cc all round because of the performance and reliability mods incorporated into this engine. I didn't say "Money is no object" or "I want to have the fastest RX-7 in town". I just said "I want a little more power, and it would be nice if it lasts".
So, apart from the Efini Y Pipe, Bonez Cat and Downpipe, Greddy Elbow that I had to start, the engine mods are as follows; Street Porting, '99 Spec Turbos, 3mm Apex seals, High Px Fuel pump, High flow Oil pump and Oil Gallery mods, Greddy Stock mount intercooler, Cold Air Intake, Ceramic coated and clearanced Rotors, Dowell Pinned Block, Power FC, Controller, and Datalogit.
It ran great (except for the idle)with the original injectors for a good break-in period, but the nagging idle issue finally wore me down and I had to do something about it. If it had idled with the original injectors I wouldn't be here now, but since I have to change them I might as well upgrade. The 850cc seem like an easy upgrade, or are they?
I've compared the 550cc and 850cc side by side and I can see the difference in length and I can see where each of them line up in the fuel rail. I understand the planing of .125" off the top of the Primary rail to drop the injector lower into the rail. It seems like an easy fix and I can most likely have it machined tomorrow if I need to. I just wanted to get the car back together and take advantage of the great weather we have right now, not be taking it farther apart.
I'll talk to the shop that built my engine tomorrow and see what they recommend. I'd rather not go for 1600cc injectors and a new fuel rail. I had to draw the line a while back as I'm waaaaay over budget as it is.
I would like to have said "I want the fastest RX-7 around, money is no object." Wouldn't we all.....
Thanks,

Ron

It is well documented on the forum that 850cc primarys dont work well with the Apexi Power Fc, it creates some tuning issues mainly due with low rpm and at idle.
do a search in the Power fc forum if u wanna know more.

with your mods i would say your safe to run the stock injectors, i ran a similiar setup previously at 14lbs of boost and would see 85-90% injector duty. This is deemed safe by some and not by others, i believe it is safe but thats another topic for discussion. i would try it for the ease of tuning.

like stated above 550/1600 is ultimately the way to go if your are eventually gonna desire more power, u would then need to purchase a seperate rail and fuel pressure regulator. if u wanna provide a lower margin of injector duty with your current setup, 1300cc secondarys would be a good option, i believe they bolt right in to the stock secondary rail so no further peices are necessary.

are you sure about 1300cc's bolting right into the stock fuel rail?

^^yes in the secondary rail.
heres a link to prove it


http://www.rx7store.net/product_p/ni...o%201300cc.htm

Good deal!

Hey, I was also reading one of your old threads about your modified 929 MC...good stuff! Whatcha charge for that?