So I read http://www.fc3s.org/ and the article on the APEXI AFC and at the end it says I'll need a air/fuel gauge or egt gauge to see if I'm running too rich. The SIXTY FOUR DOLLAR QUESTION.....what figure on a multi-meter constiutes too rich? Ain't gonna buy a air/fuel meter if I can help it. My multi-meter seems to read millivolts just fine. I'm thinking (almost bought 'em once) 680's to put in the secondaries. I have 550's there now and at wot read 80mv. This is a 1987 N/A. True blue duals and K and N (not a great performance enhancer in my humble opinion, relative to the exaust upgrade). Perfectly working aux actuators and stock perfectly working acv and air pump. Oh. The wipers work good too, eat your heart out.

 

LEAN RANGE: Four red LED's (.050 to .249V)
STOICHIOMETRIC RANGE: Ten yellow LED's (.250 to .749V)
RICH RANGE: Six green LED's (.750 to 1.000V)

This is the setup for the autometer A/F gauge, cut from their website (http://www.autometer.com/hp/index.html) which explains the working of the A/F meter.
Given you are running at .8, that would constitute a rich condition, but not by much. Bringing that down to about .5 would get you a bit more power....so would lightening up by removing your wipers
AN A/F meter is only 40 bucks or something... It's worth it.

 

What an air head I am. I've been refering people to that web site for some time now. Shoulda taken some of my own advice. But, that brings up a point. If I get a APEXI AFC, then I'll be able to lean out the mixture. Right? At least thats what I get out of the Apexi AFC article on the fc3s.org site. Fact is since I'm getting .8v at wot, its hardly worth putting out 300 bucks for a afc. Please don't write me and tell me the o2 sensor is not reliable at wot and that I need to get the engine on a dyno and get a four wire sensor. I have read that and it makes sense, to some large degree. I'm just gonna have to work around that. By the time I spend that kind of money I can do the turbo swap for the same hp. Oh! Lightening up the car by removing the wipers? Thats gonna happen the next time those things fail in any mode whats so ever. Rainex will be the replacement. You can rely on that stuff, unlike Mazda's wiper switch and relays.

 

I will be getting bigger injectors..... probably 680s. with those I am pretty sure an AFC would be a requirement.
I am not sure how much better tuned your engine could be with the AFC, since it would only be correcting it to a minimal degree, maybe 5-10 horse?? But I have had no first hand experience with them... So I can't really give an opinion. It does however, open up the door for more future modifications. (and they look cool...)
At least you aren't running lean. Boom.

 

I realized just a few minutes ago that I lied on the first post. That .8v was this morning with the turbo. I just got in the 87N/A and went out Interstate 20, Benbrook exit, slight uphill grade, 7300 in forth, meter was reading .65. From that I think 680's is the way to go without a doubt. So much to buy, so little money. I'll have to start playing the lotto again I guess(talk about a losing idea). By the way its a real joy in the n/a doing 7300 and climbing due to well balanced tires, great alignment and just a real solid feel. Now the turbo is just the opposite above 100. Just not safe. Got Tokico shocks but still gonna buy new ball joints and tires. Cars generaly just have a different feel. So I hear that there is a cutoff on a n/a somewhere above 7500. Is this just a rumor or is it a real deal?

 

I don't know about earlier years, but in my 90, (wether or not the rev limiter is functioning, who knows) I rev to 90000 beofre I shift in first.. no buzzer or anything.... in my 88, I do recall a buzzer after redline, so I assume three is a fuel cut somewhere after that... can't tell you when though....maybe around 7500.....

 

Thanks for the info BamBam......I envy the later models with the lighter rotors. I know my car will pull over 8000, but I have some doubt about how many times I can get away with that. Its possible I read some misinformation about an ignition cut on these cars(not to be confused with turbo fuel cut, please, talking N/A). Must be misinformation if your pulling 9000. Anybody out there with a 86-87 that pulls 8000 on a regular basis?

 

If your car is an n/a why do you think you'd need bigger than 550cc/min injectors? TII's have 550s all the way around and you can get about 220-240hp out of them with the stock fuel pump. I don't know what you can get out of them with a FPR and a bigger fuel pump.

I'm sure your na isn't running out of injector capacity with 550s.

I had 2 680cc injectors in my 87 TII without a AFC or anything and let me tell you it KILLED driveability. Once the secondaries kicked in the car would noticably loose power, depending on the gear (boost changes in 1,2 and 3rd) it would start cutting out around 5500-6500rpm. I put in the stock 550s again and my 1/4 mile times dropped from 14.8's to 13.9's. Better yet was the improvement in driveability.

Jeff
87 TII, now tipping the scales at 2580lbs
93 R1

 

turbo jeff......I'm like the character Johnny Rocco (played by Edgar G. Robinson) in the movie Key Largo(Bogart movie). I want more. I have 550's in the secondaries, and like I said, the meter reads .65v at wide open throttle. Car runs darn fine. Either Mazdatrix or Racing Beat recommend 680's in the secondaries. The .65 leads me to believe that since I'm doing just fine with 550's, why not go bigger until I find what the limit is. One thing I do not understand in your post. If you had 680's in the turbo and it was killing the performance, why did you not get a afc? That is what Dave Gibson recommended when I said I had 550's in the n/a. Said I was probably running rich and killing the performance and that with a afc I could tune it so it would not be running to rich. Curious. Also, I'm taking Racing Beats advice and not putting them in the primaries. Talking 87N/A here.

 

Sorry, I didn't tell you why I didn't go with the AFC. I building this TII for the $2002 challenge by Grassroots Motorsports. Since I only have $2002 to spend on the entire car I can't spend the $350 or whatever the AFC is. With a manual boost controller and the 680s I was running like 12psi until 3800 rpm when the secondaries would kick in and the boost would fall to 7-8 then build slowly to 8-9 psi. It would pull pretty hard in certain parts of the powerband but 1st and 2nd gear sucked because I had to shift at 5500-6000rpm. Wasting time at the begining of the 1/4 mile can't be made back.

Bottom line is bigger isn't always better, sometimes it is worse. Since the 550s can support pretty decent hp then you might/probably don't need larger injectors.

Back in '98 a friend of mine ran a 14.098@98mph in his 88 TII with only a 2.5" downpipe, presilencer and a HKS intake (HKS filters suck for filtering...). His TII was stock otherwise, stock cat-back stock everything else. Now if a n/a weighs less you'll need less power to do the same run, if 550s support that fast of run on a TII don't go bigger.

Jeff
87 TII 13.9
93 R1 13.59

 

According to the Rx7.com fuel calculator, 460cc in primarys and secodarys should be good for 236hp at the flywheel at a 85% duty cycle.

On my car, a new fuel pump, fuel filter, and cleaned all the injectors made a world of difference. Infact, i'm i'm reading rich with all my mods, while using the stock injectors (Read sig bellow.)

My dad (long time drag racer/hp junky) thinks that my FC feels like its putting out over 200+hp. I say 190-200, but i've been driving it for awhile...and cars seem to get slower the more your use to em. Atleast they do to me.

Just my thoughts, and Rx7.coms fuel calculator. CJ

 

PP13bnos.......the fuel calculator says at the bottom that the stock ecu duty cycle is 48-63 max, so the 85 you stated does not apply to me with a stock ecu. Thanks for reminding me of the Rotary Performance site and the fuel calculator though. Every little bit helps. http://www.rx7.com/cgi-local/2ndgencalc.cgi