I'm getting my car dyno'ed this Sunday, and I was wondering what you guys think I will pull. There's a rotary meet about 5 minutes from my house, so I figured I would see what it can do. I'm getting one dyno run and one 1/4 mile run. I have an '89 NA that has a rebuilt motor with about 3-4000 Km's on it, a Fidanza 8lb. flywheel, Exedy stock spec clutch, and the aux. ports have been wired open. I had the motor street ported while it was out, but I am still running a stock exhaust with a shitty catback the PO put on so I don't think that is going to help me out any, and it has a leak where the first cat bolts to the downpipe. So I want to see some predictions, and I will post the results on Sunday.

 

Im gonna guess 140rwhp

 

135rwhp

 

120whp max

 

RWD cars lose about 15% hp from the engine to the wheels, right? It's freshly rebuilt so it is hopefully pushing the factory 160 crank hp. 15% of 160 is 24, so I should be getting 136 whp. They also say that a lightweight flywheel frees up 10-12 to the wheels. So is hoping for 145 whp going to be a letdown?

 

Dunno, but my friend who has an immaculate, (65,000k 1989) 240sx recently dynoed 130whp with a cat back, header and an intake.... but he has a truck motor

Anyway, what I'm getting at is, I hope you beat him!

 

Flywheel won't free up 12hp....
I don't see why it would help much. It's basically lighter weight to help with quick revs.

 

you may break 120 on a dynojet, but if its a decent dyno good luck

 

If a street-ported NA can make 190 RWHP with intake and full exhaust, I don't see why a recently rebuilt stock NA can't make at least 135.

 

I think the flywheel frees up hp because it's less weight the engine has to spin. It doesn't create hp in the engine, but rather lets it get more to the wheels. Or so I've heard...

What's the deal with Dynojets? I've heard that there are different types of dynos, Mustang dynos read different than other kinds, etc. Would someone mind explaining that?

 

because of the "Exedy stock spec clutch" I think it will drop 500hp no probs

 

Thanks for that useless post, but I wasn't hinting toward the clutch giving me more hp. I'm just letting everyone know that I don't have an old slipping clutch in there.

 

Show is tomorrow... I'm getting one dyno run and one 1/4 mile run, so I'll fill you guys in when I get home. Any last minute predictions?

 

You guys were all low... 149 hp 115 tq. Update thread can be found here: https://www.rx7club.com/time-slips-dyno-128/update-89-na-dyno-1-4-mile-10-14-a-696562/

I'm just upping this with the link for when it falls off and someone finds it in a search.

 

I'm hoping i don't make that kinda of numbers on my car just check out my sig

 

I hate to tell you, but you're probably not going to make a whole lot more. The stock fuel system is good for about 250 rwhp so I don't think the injectors are doing much. The S4 engines are already down on hp, and also the biggest restriction on these motors is the exhaust, so without that your intake/tb/street porting are not seeing their full potential, if any. If you have an exhaust that's not listed in your sig, then you will definitely make more power than me. But like I said, without it your mods aren't really making as much power as they could. I'm not trying to burn on your car, just stating my opinion.

 

put a straight exhaust on it and a presilincer for the noise and u should get a big difference. also if you remove the sleeves out of the exhaust port, u will get more top end performance. with that done, u should b making atlease 180whp. it seems to me that everyone here underestimate na rotaries.

 

When I got the motor rebuilt the mechanic left the diffusers in because he said that they weren't going to be a restriction for my power goals. If I ever go turbo (highly doubtful) then I will get them removed, but if not then I will probably keep them. And like I said earlier, I'm going with an SDJ Header, Bonez cat and Corksport catback.

 

my motor was streetported, but also the exhaust was ported as well. everything was done at once, so i dont know how much of a difference the exhaust port made, all i know is that my car was fast as hell for what it was. dont know how much hp i was making, but my top end was very strong.

 

My exhaust ports were also ported, but the diffusers stayed in. He ported it for timing, not size so they didn't have to come out.

 

it will still free up ur flow some with them out. anyways how much hp r u aiming for








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I mostly want to do autocross to start off and hopefully get into some hillclimbs so I think that 200 rwhp is plenty for that. Once I do the exhaust I am saving up for coilovers and then I'll probably go standalone to get rid of the restrictive AFM. I think that will get me to where I want to be.

 

hillclimbs should be in the 300 something range....autox is fine with 200.

 

I'm not even sure if there are hillclimb events near me... I'm just starting to try to get into the racing scene. I'm going to try to attend every autox near me in 2008 and talk to some people who do other kinds of racing to see what's going on near me.

 

Just to clear up some misconceptions:
I've seen a 125 rwhp CSP miata smoke the entire autocross field. If you modify the porting in the engine, your autocross class changes dramatically. Most hillclimbs use the SCCA classing.

The AFM isn't as restrictive as people think (its really the air snorkel that is restrictive). Engine creates vacuum, flap (or axial cone in S5) opens from dP, air flows in proportion to engine suckage. Drill 3 1" holes on 'cold side' of airbox - there was a thread on this somewhere.

S5 ECU dumps fuel in at 5500+ RPMs - find a way to lean it out, and you'll find quite a bit of top end. Magic AFR: 13.5 - 13.7 or so on an N/A.