There are lots of threads here on what the RX-7 have the potential for....so I thought I would share my first dyno results with the group. I have a 1984 GSL which I have owned for 12 years (so I have invested slowly over the years!!) with a street ported 12A, Light flywheel, Weber 45 side draft carb and a full RB header, pre silencers and ractive muffler.

The results: 106 ft/lb @ 6069 RPM and 134.7 Hp SAE @ 6704 RPM at the wheels. The guy that Dyno'd my car says that the rear wheel HP understates the crank Hp by 20-30 hp - so that mean the car is producing roughly 150-160 Hp - not bad from the 100 Hp in its stock form.

The car is in great shape and I will post some pic for the group later.

 

Well done.

You might be a little under carb'd if that's a big street port.

 

Or a restrictive muffler. Never researched Ractive mufflers before?

 

The difference in power between rwhp and fwhp in a Gen 1 is around 17%. Exact comparisons seem to vary according to the dyno machine. Rotaries seem to have less performance drop than piston engines.There is some interesting comparisons of transmission loss on the RX-8 after some of the power figures put out by Mazda were queeried.

A well tuned street ported 12A can produce around 180fwhp according to some specialist tuners such as Yaw with engine dyno equipment. But then streetports come in various shapes and sizes!

 

Hey I was just wondering what your powerband was like?

I have an sdj header and holley intake, I havent noticed much below 4000rpm yet, but havent had too much of a chance to toy with it yet either.

 

Noice. That's a good number for a 12a.

 

Why do you think 134rwhp is a good number for a streetported 12A?

Perhaps the 45DCOE is the restriction, I would have thought a 48IDA would have been a better choice. A Paul Yaw Nikki was supposed to put out about 145rwhp when fitted to a streetport.

 

i have a 12a thats is bridgeported on the primaries and large street ported on the secondaries and i made 133 rwhp. i'm runnung a road race header and weber 48 IDA. i must need to run better than 12.5 AFR

 

Here is a jpg of the Dyno results (poor quality..but all I have). The red line was the baseline and the yellow line which is hard to see was the after we changed the size of the fuel jet. Also went out tonight and took some pics of the car. (hope these post ok - first time)

 

Most all the streetports now are just the intake. It is recommended that when doing exhaust porting that you use new housings. So you are losing Hp by just doing the intake. Most people don't want to pop for new housings. The old numbers for Hp for a streetport, intake and exhaust were as follows. 12a, 195bhp, 13b,225bhp. This was with a complete header system and a weber carb set up.

 

good #'s.. the car must run good... nice job, and nice car too

 

Yea, now intsall a blower on it!

 

Sweet! I think you have some tuning left to do. I'd bet theres more in that little 12A of yours! Get a WB on it. Or make some 3rd gear to redline pulls, shut off the motor, and check the plugs. I'd bet your leaning out up top. What are U runnign for a fuel pump? Pressure?

From what I've seen with ported motors like yours you should be making power past 6700 rpm? Your curve is falling off very quickly, but is very linear up to that point! What timing are you running? Plugs?

Anyway nice car! Keep us posted.

 

not to get involved in this little quarrel, but RB is prolly trying to sell more by saying it is recomended to replace whatever. if its a piece of ****, then replce it, it its fine, then why bother??

 

Exactly. Why lap side plates if they're good enough? They will wear out faster when the nitrided surface is removed or reduced through the grinding/lapping process. But then again, I'm not trying to make money selling or lapping side plates.

 

I've been looking for more dyno proof. I keep hearing the spark dies after that point. If he has the stock ignition with mildly modified timing or what have you this would prove it moreso.

 

Hi - as far as I know I am running stock timing, plugs and ignition. (would like to upgrade down the road).

 

That's rediculous. The only reason to replace housings is if they show too much wear. Regardless of whether you want to port them or not.

 

I'd suggest doingthe 2nd gen coil mod. It improved my idle a ton and many claim it helps performace. I didn't notice any "seat of the pants" difference but the 600rpm idle rocks! I think with a street port I'd suggest an MSD6AL unit to kee your spark up. It's got the built in rev limiter as well. They can be found used on Ebay pretty cheaply. Also hooking up that WB will tell U everything U need to know! I'm ordering onew for my 1st gen too so I'll keep every one posted.

 

Ok , i clarify this for all you grumpy people,lol. It's recommended to either replace or use only housing in EXCELLENT CONDITION when exhaust porting. And most motors that are torn down do not have housings in excellent condition. Acceptable,yes. And i didn't say don't do it, i'm just quoting what is said about it. I've read too many times about people rebuilding and porting their motors, then a short time later they are having problems. Wouldn't you rather
not take a chance and do it better the 1st time and get more life out of the motor?

 

The thing is, it doesn't matter whether you're porting them or not. Too much wear is too much wear. If they're good you can port them. Saying you can reuse the worn housings if you don't port them and just do the intake shows a complete lack of understanding on your part.

 

When you finally understood what i posted , let me know.

 

When you learn how to communicate try posting it again.

 

This is what you said...

My point is... if the housings aren't good enough to be ported then they're not good enough to be used full stop. Understand?

 

Yes on the post you quoted it is mi-stated by me. That's why i reposted to your quote.
Again i will state the same thing. It is recommended(BY RACING BEAT) that ONLY on EXHAUST porting that you either use NEW housings or ONLY those in EXCELLENT shape).
Housings do not have to be in EXCELLENT shape only within specs and visual inspection to be used for NORMAL STOCK rebuilding. Again it is only a RECOMMENDATION, Sorry it's not my quote but from a reputable engine rebuilder that has been in business for many years.
And my statement that most streetports today are only intake should be that most do it yourselfers choose to do only the exhaust based on research i've done.

Is that more acceptable to you?