wrxfc3s

I haven't modified the engine managment yet. So everthing is stock in that arena.

My question: Since I have tons of boost available and almost any amount of full boost available around 3300RPM. Why can't I just install bigger secondaries and be done with it?

I would think I could run 12-14psi w/ the bigger injectors on factory managment and not go lean. Given the timing is another issue. But is my thinking a reality? I bought an old HKS AIC about 3 years ago that I never installed. What is going to happen if I put the injectors in adn run it. I was thinking 720cc or 800-900cc range. Can someone point me in the right direction?

Felix Wankel

You'll run it too lean before the secondaries even come online.

gsracer

This is a pretty general statement. Why not go for 720's all around?

Bambam7

Idle would be way too rich, as well as across the entire throttle range when not at full boost. It would be popping and hesiating all over the place.
You'd need an S-AFC or standalone to manage that, It can be managed, but there wil alwyas be little anomolies while starting and driving that may creep up. (with a piggyback anyways, maybe not a standalone)

OF course you need a bigger fuel pump. Definately a Walbroor comparable. Apparently the pump will hits it's service ceiling before the injectors are maxed out.

Going lean with the factory computer and bigger injectors isn't the issue- though the factory ECU does limit injectors by placing a conservative 60% duy cycle on them. The issue is maintaining proper AF ratios and drivability when the injectors are in- it'll run too rich- since obviously the computer is verying the injector pulsewidth according to it's programming, assuming it's using stock injectors!
Running too rich under part throttle is the problem, easily solved with an S-AFC. Or boost/fuel computer.
And additional injector is a lot of work and managing for this.
I'm not too sure what you were really asking, but this is my answer.

gsracer

I should have been more specific. I assumed that anyone going with a full to4 is going to have the walbro as that's usally one of the first fuel mods. I'm also a hardcore stand alone guy so the band aid safc is out of the question. Assuming therefore that the fuel pump can keep up with the demand of the injectors and you have a stand alone, e6k, microtech etc... why does it seem like most people leave the primaries stock and go for monster 1600cc secondaries with custom rails??

I'd be scared of running lean before the secondaries kicked in at 3800. Then again I guess it all depends on what size turbo you are running and you would expect it to spool off the line. But even then there could be cases in fourth and fiffth on the highway where you would be running just the primaries before the secondaries came online, all a full to4!

rx7_turbo2

I'm not really sure what you're saying. If you run stand alone you canm set how the secondaries come on, be it manifold pressure or RPM based, so 3800 is no issue.

If you are trying to run 1600cc secondaries with the stock ECU the car will bog as soon as 3800rpm hits.

I will be running 720cc primarys and 1600cc secondaries and I anticipate no problems tuning the Microtech to handle them. Last weekend I witnessed a 10AE with a Wolf3d v.3 running that setup and while there was some initial problems it is now running better and safer than ever.

I am a firm believer now that the best thing you can do for your 2nd gen RX-7 stock or not is to yank the factory ECU, it's old technology and causes nothing but headaches.

Felix Wankel

gsracer

doh! Ok I see where I err'd in my train of thought. Stock ecu is gone so no 3800 rpm pre set secondary activation.

rx7_turbo2

That among other things is a major perk to standalone units. Some operate differently than others and I am no expert on all the EMS out there but I would hazard a guess and say the majority have ways to stage additional injectors.

bl|nk

2 weeks and counting and mine goes bye bye headaches hopefully.

rx7_turbo2

I know I can't wait. I have seen so many 2nd gens run so much better once the stock ECU is gone.

wrxfc3s

I was wanting to put bigger injectors in place of the secondaries. If I match boost to fuel then I should be OK, or at least I thought. I can control boost before 3800 somewhat. I just want to run around 14psi without changing management. The RX7 is now the 3rd car in a line that gets upgraded. I have the WRX and mustang in front of it now. I tried selling the damn thing and no one wanted it. but that's beside the point.

I figured if I put at least 720cc on secondaries I could turn the boost up to around 13ish and be somewhat OK. I realize it would lean out there for a sec but not enough to be a big deal since it's relatively lower boost goal. I've run 11psi a couple of times but not through all gears just first and second. I have a huge front mount IC 8x24x3 core and straight 3" exhaust on this booger. If I have to I will throw the crappy ECU away and get a new one. I just have better places to spend $1000 right now.

What's the cheapest aftermarket ECU available right now that'll do the trick. I'm not fond of putting the SAFC on there because of the status of the wiring as it is.

rx7_turbo2

You can't treat this car like the others you mentioned, there is NO room for error. One mistake and pop the motor's toast and shelling out that grand doesnt look so bad. Look at Microtech, Haltech, Wolf, AEM, Greddy eManage, there are alot of options.

chris_stampe

Microtech is probably the cheapest full ems available.

wrxfc3s

How much and where to buy?


I was thinking, what if I use the AIC to run the secondaries and move the stock ECU injectors out somewhere else?


That seems doable, no?