Hey guys, im trying to figure out what to do about my fuel system to get the most out of my 99 spec twins. After using http://www.maxcooper.com/rx7/how-to/...tem/calcs.html it seems like I can go with 4x 850cc or 2x 1300cc. The fuel pump has been taken care of with a supra tt unit already.

Soooo, what would be the best overall setup for the injectors and why?

Thanks,
Chris

 

You should be fine with 1300cc injectors. Just make sure you have it tuned properly. Get 1600cc injectors if you want to be real conservative.

 

If you've got a PFC I say go with 4x850cc, you will keep regular idle with no issues and that much fuel will support 390rwhp. That's the setup I had on my last car, which had 99spec twins.

 

4 X 850's is cheaper but most of us run the 2 X 1300's. Make sure you have all your injectors cleaned a flow tested. RC Engineering charges $25.00 an injector. Cheap insurance.

 

Of those two choices, I would use 550/1300 I think since it's direct drop-in. IMO, if you want to do it right - go 550/1600 (but this adds a few hundred to the cost of course!)

 

Guy's he's in Cali, no 1600s....

Either way will work...I think four 850s would actually be more reliable but harder to tune and install.

 

im about to do the same to my 99 spec, have the supra pump and fuel pressure regulator ordered, but cant decide what setup to use too, is the 850cc to primaries not a direct drop in?

 

You have to get your primary fuel rail modified for the 850s to drop in.

 

I am running a PFC and Kan will be tunning the car in May. So im mostly looking at whats going to be more reliable and cheaper to set up. I do plan on having my injectors cleaned as well.

 

FWIW, I'm running 1200cc secondaries with the Supra pump and they max around 75% (i think, been a while since I looked) running 14.5psi and ~300rwhp on a Kan tune.

 

can i confirm 1200cc secondaries (top feed) are a direct drop in?

 

edit [ side feed ]

 

yes, 1200 and 1300 are drop ins for secondaries.

 

just get your stockers bored out by RC.

 

I'm running 4x850cc injectors on a Steve Kan tuned PFC to 14.4-lbs. of boost.

Idle is perfect. I have the Supra fuel-pump.

I like it. I had Steve tune it for reliability, not outright HP.

As such, it gets about 6 MPG on the track and about 9-10 MPG in town.

:-) neil

 

id go with my setup.

I got 550cc for the primary
1600cc for the secondary.

Im making 478 @ 17lbs and getting 300miles on a full tank.

Going with small injectors will just enable you to have enough fuel but as long as you have close to the same setup as mine you wont have to worry about changing you injectors again when you go for the bigger horsepower goals and only worry about your fuel pump

and my idle is around 1200rpms on a extreme street port setup

 

^I run what you have and like it.

 

Anybody have idling issues with 850 primaries and 1300 secondaries?

 

i havent experienced the 850 primaries but i was told that it makes the idle real rough meaning adjusting to a higher idle to deal with the 850's but i will admit that that setup rx7 rage is better for small to medium turbos (twins, to4E, t60-1)

 

I initially had 850cc primaries...didn't like the idle quality (streetable though), so I swapped them. After tearing down the block (13k mi later), I found my "aftermarket" solid corner seals wore grooves around the irons; lowering compression...I probably could have tuned around the 850cc's if I had a solid block.

 

No problem with my 850cc in the primaries at idle thanks to Steve Kan. And it is under 900 RPMs.

:-) neil

 

frogot to add that those bigger secondarys are going to require a different fuel rail

 

Hey Neil, did you have to get a new fuel pressure regulator? And also, did you get the drop-in 850s for the primaries? Thanks!

 

No new fuel-pressure regulator was needed, especially since I replaced all the fuel-system "wear" items.

The 850's are NOT a drop-in replacement, I had a local machine shop mill off I believe it's 1/8-inch (check archives to be sure) for about $30.

There is an RX7club member who'll do it for like $5 or $10 dollars, but with shipping $$ and the downtime, $30 was well spent.

Also, I used all new VITON O-rings that were properly lubed during installation to avoid pinching, and was careful not to lose the spacer.

:-) neil

 

Thanks Neil, but do you think I'll need a new regulator? Is it safe to just get one or is it just excessive overhead?