Ok guys, I got my intake, got my exhaust, saving up for my headers, and i'm looking to see what to do next. My local Rex Mechanic is all about Bigger secondary injectors and a "Fuel Pressure switch", How much gain doyou guys think i would get from bigger Injectors?? i dont care about HP numbers, i just wanna know if it will be Noticeable. And this fuel pressure switch he's taking about is a switch he hooks up, that when its flipped it ups the fuel pressure. he says the combo of the two make a nice high rpm boost.... what do you guys think? any other recomendations on what i should do next? BTW i have an 87 gxl.. NA..
-thanks

ben

 

Well, seeing as how the RX-7's run rich as it is, most people would probably recommend getting some sort of "piggy back" ecu such as a S-AFC to tune your existing injectors. If later on down the road you need more, you can upgrade to tii injectors or something, but unless you go forced induction or something, you will probably never be able to fully utilize your stock injectors. BTW, a S-AFC is only $200-$250 depending on where you look.

 

Bigger injectors?

I'm not clear on the subject but don't you only need them if your stock fuel injectors cannot provide adequate fuel for more air? On NA, I think you would need larger injectors only if you're in the 200+ HP range.

I think larger injectors are mainly for the turbo guys running more PSI than stock. Of course, this is just my theory. I'm still new to the rotary engine but just speaking from experience with piston engines. Please correct me if I'm wrong.

 

Get a new mechanic. Seriously.

 

You don't need bigger injectors if you have a N/A, unless it's ported. You can buy a SAFC, which might give you a few HP if you tune it right, but I wouldn't even bother.

 

More fuel does not make more power. More air makes more power and you need more fuel to safely have more air. (pretty broken down, but true) ACTUALLY, the less fuel you have, more lean you run, the more power you will make. If the more fuel, the more power...drag guys would have it easy. Just get the BIGGEST pumps and injectors and you would be good to go.

 

Sounds like your mechanic is either a nutjob who smoked crack thorugh his mechanic courses, or is trying to rip you off like mad.
Maybe a combo of the two? Either way he's incompetant.
Bigger injectors are almost never needed on an N/A, even ported ones.
Running a little leaner on an N/A (tuned properly!!) Can yeild more power than the stock fuel programming. This can be done with the S-AFC.
I wouldn't trust any mechanic that DOES NOT work at an rx-7 only shop. Dealerships- nope. Tuffy- that's a joke, etc. I've heard so much bullshit that has poured out of them They may know how to fix regular and simple problems, but anything more complicated means "New engine!" and they don't know *** about performance. There are exceptions of course, but I'm sure many of the experts on this board will agree with me.

Oh, did I say your mechanic is a nutjob?

On a side note.. fuel pressure switch??? This has to be some kind of bypass or a little solenoid relating to the fuel pressure regulator... anyone have a clue? Wouldn't mind boosting the rail pressure a good chunk (I now have a walbro) to get my injectors flowing more than spec.. I don't want to have to buy new ones.. this sounds logical, but I've never heard anyone apply it to the rx7's fuel system, probably because the REGULATOR IS MECHANICAL!!! What's wrong with this mech????

 

I read that and kinda laughed. Just learn to tune with and S-AFC and you can get the same effect, but better. Instead of having 2 different fuel pressures, you can change the fuel map based upon throttle positions, RPM, etc.

 

These are words of wisdom, heed them well.

If any mechanic says "bigger injectors will boost power", turn and run. Fast...

 

Not necessarily. I agree with what Ryde_Or_Die said, but sometimes it is legitimate to increase injector size to get more power. the problem with this case is that it just doesn't apply to a NA except in very extreme cases.

 

Larger injectors are only required if the current ones can't flow enough to maintain adequate A/F ratios. If the current injectors are big enough, bigger ones will make no positive difference whatsoever. This "mechanic" couldn't be more wrong in saying bigger injectors will boost power.

 

No ****, I'm with Josepi, get a new mechanic.

 

Yes, but that is obvious. Like I said, you only need larger injectors to safely make more power when you have more air. Extra fuel is not what creates extra power. Lots of people think getting larger injectors is going to magically give them more HP, I guess since all the cars that are fast have larger injectors and pumps.

 

You mean to tell me that my 1600cc secondaries and my 1300cc primaries aren't giving me 500 hp more?!?! DAMN IT!!! Next you're gonna tell me that my NOS sticker doesn't give me 50 more hp... man.. And I thought my Honda friends were just being cool guys and letting me in on their secrets!

-Kanaida

 

LOL!