if you want to stay on a budget, then stay stock NA, while doing as much as you can with intakes, exhaust, and a stand alone.

the stock ecu/ harness will hurt you in terms of reliability. a tps breaks. where to fine a new one vs going to vato zone and getting one. its easy.

also, without cracking the engine open, you wont get much power

Ah, Big Daddy Roth...I built more then one of his models.

No, see my posts in this related link:
https://www.rx7club.com/2nd-generati...rboost-293609/

NA power tuning is usually done as described above by j9fd3s, in that you find the max power and then make it just a tad richer.

They are crap, so don't bother. See our EMS forum for products that are more worth the money and proven to perform well on RX-7s, like those from Apexi, Haltech, Microtech, Electromotive, Rtek, etc.

Yeah, my FC felt heavy with the cage when it had the NA engine. My NA 1Gen felt OK with the cage, although the tubing was a smaller gauge and the car itself was about 400 lbs lighter.

The AEM wideband gauge has a pretty good reputation, although I have not tried one. Their EMS was a little sketchy at first because they used their first customers as guinea pigs, but I think they have worked out all the kinks by now.

A really anal retentive professional tuner will put a bung in each header tube and tune your rotors individually, then remove the sensors and screw plugs into the bung holes. The sensors may be O2, EGT, or both. Other tuners may use a single sensor to measure the collected exhaust, a tailpipe probe, or a 4 or 5-gas analyzer. This is why I tell people not to buy anything until directed to do so by their tuner, and even then you should question whether they are just trying to make a sale.

You don't need a wideband, you should only be paying for the bung to be installed in your exhaust, for the tuning, and for the dyno time.

If your tuner makes you buy a wideband from him, tell him to fuck off.

If you want to skip paying for tuning, you can always learn how to do it yourself and just tune it on the street or on the track with your own wideband... except remember that blowing up engines is part of learning how to tune. And in the end you will have gained a valuable skill, but you will not have saved any money.

I'll be selling my 4.30 N/A LSD and Trans with Miata gears locally soon if you're interested.

There was a local guy on the forums here, I think his user was "Solo///M". He was building a GTUs for autocross. It was an S5 car, but he had some success tuning the N/A. You might find some information if you search for his build thread.

Oldie but goodie
https://www.rx7club.com/2nd-gen-arch...dations-31410/

My vote is still a used $100 Apexi SAFC, followed by a dyno tuning session at a good shop (after other minor mods such as intake/exhaust/port sleeves). Bam, done, no need for buying a wideband or blowing the motor learning how to 'tune'. In my case it as maybe $400 total (at Rotary Performance, Garland TX) and 5-6hp gain, with a much smoother curve.

leaner will make more power on a turbo car, but just leaning it out until it pops is a very expensive way to tune a car!

basically the difference between a stock port NA and a turbo, from a tuning point of view, is that the turbo makes a lot more hp out of the same size engine (BMEP). so the combustion pressures in a turbo car will be higher. with higher combustion pressures, you need to worry about detonation, and preignition more.

to combat detonation we can run a richer air fuel ratio, which would loose a little power, but you made up for that loss by bolting the turbo on the side of the engine :)

if you go take a survey of factory turbo cars, the FC and FD's aren't set very rich from the factory.

I am going to start searching all the last recomendations given. In the mean time, quick question.

I have read on these forums that leaning out the mixture on the NA engine improves its power. But for what I have learned over the years, the most power is obtained around 12-12.5 A/F ratio.

If leaning out the engine gets better power, what A/F ratio does a NA engine has stock? Richer than 12???

That depends on the car.

I'm pretty sure the reason you can gain so much from ECU tuning is because stock ECUs are designed to perform safely (and smoothly, quietly, economically, and ecologically) with ANY stock engine, whereas a ECU tuning sets the performance for that specific engine, in that specific car, with that specific setup (Japanese lesson: Japanese tuners call this "gensha awase" which also applies to suspension settings...). But each (stock) car is going to end up with slightly different AFRs, usually in the fairly rich range.

You might also want to get your old injectors cleaned and benchmarked (they come back looking brand new and performing better). It's $100 for four, and it's cheap insurance to make sure the car is running as well as it can.

didn't we just go over that on page 1?

there is no specific AFR figure. widebands are not all accurate, dynos are not all accurate either but they will show increases in power over a specific AFR number. track times will also show improvements, since if the car is running quicker it should be pushing quicker times(straight line).

it depends. the S4's run about 14.4 until 3500rpm, then they dip to 12.2@4k, lean out to 12.8 by about 6k and then go rich after that.

the S5's do the same up to 4k, then they go rich and can hit AFR's in the 10's by redline.

leaning out the S5's has a huge impact in power on the butt dyno. the S4's mixture is reasonable, and you can get a teeny bit of extra power over 7000 by leaning it out right there, but under 7k, it almost wants to be richer.

i agree, going from 11:1 to 12:1 on an S5 feels like 40hp, but going from 12:1 to 12.5:1 feels like 2-3hp, so i usually end up just keeping the S5's running about 12.2 all the way up to redline. i'm sure if it was a race car i'm leaving hp on the table, but in my case these are street cars that need to pass smog.

Valkyrie and RotaryEvolution. I know that it depends on each car and situation, but I was just looking at a ball park figure of what Mazda was trying to achieve for this engine from factory.

Just like j9fd3s listed.


Now, I am surprised to know that the S5 can get more power than the S4 when tweaking the A/F ratio. Specially having into consideration that the 89+ N/A engines have almost 15hp more than 88 and prior!!

notice i said it feels like 40hp. on a dyno its probably 10ish.

the S5 is a little easier to get power from, you lean it out a little, and it makes a huge difference in the seat of the pants.

Yes, I noticed what you said. But 15 extra hp from factory for the 89 + 10 hp from exhaust compared to a stock 88 :)

I think I will leave the A/F for now and will focus on exhaust mods :)

It looks like I cannot edit my own posts... for some reason... So I am rewriting my previous post so it is more understandable.

Yes, I noticed what you said about feeling like 40hp, NOT being 40hp.

I just cannot believe that S5 owners have 15 extra hp from factory, and can get another 10 hp from leaning the mixture. When the S4 cars have less HP and cannot get much gains from playing with the A/F.

So... I think I will leave the A/F games for now so I can focus on exhaust mods and maybe a new ignition system (which I have heard helps a lot as well...)

Thanks!