What rwhp power should a na 12A streetport achieve?

Does anyone have any dyno results?

 

With a crap stock Nikki that needed a rebuild, I hit 113 rwhp @ 7400 rpm or so...I don't know if the Forum still has the attachment, but I doubt it seriously since it lost all the alternator pics with the move...

 

180ish

 

depends, if u street port a stock motor, dont expect all that much, maybe like 20-30 at most, but with a holley 600cfm carb and a racing beat header, 180-200 hp should be what u get on a good day.

 

If tuned right, it will have 180-200 flywheel hp. Which is probably around 150-170 rwhp.

 

The engine I am thinking of porting is the 1985 12A as used in some export markets, with 10 degrees more porting than the USA specs, which produces 112hp in stock form. With bolt on mods such as a good header and a modified Nikki as Sterling recommends it currently has about 126rwhp.

My thoughts are to open up the inlet ports by some 17 degrees and the exhaust ports ten degrees, thus having a moderate sized 'streetport'. The question relates to what sort of rwhp it will then get.

 

y ask us? u said ur gonna do it, so wen u get it done, how bout u tell us...

 

Well from all Ive seen and read (minus the bs claims). It really depends on ..............
a- What port template, specs you use- Mild, RB, monster port.
b- How good a job you do.

 

Carl, I fully agree with the impact of your parameters.

The USA spec 12A has very conservative porting. Where Maxda specs were an extra 10 degrees of porting {mild}
the engine produced an additional 12hp. A decent carb modification and exhaust system brings this up to about 150-155hp.

As far as I can see going from US specs to RB spec porting adds about another 30hp. Giving a total of 180-185hp. The problem is these are all claims and flywheel performance. What I am hoping to get is rwhp dyno figures so you can compare outputs in practical terms when you are tuning.

What I would love to really know is the porting specs of the 10B engine. In stock form it produced 128hp which was detuned to under 100hp for the US market by smaller ports and restricted carb jetting.

 

Well, not to rain on your parade, but having some numbers really wont mean much. First, every dyno is a little different, and even pulls on the same dyno on different days will yield varying numbers. Also, every car is different. Different gearing, trans, tires etc will throw the numbers off too. And so is the amount of friction in the driveline different from car to car. Your better off with FWHP numbers to remove alot of this from the equation, but then that would defeat your purpose for the numbers. Are you shooting for a specific rwhp number? Or is it more of a "Im in the range cause my numbers are close to the numbers I got off someones dtno sheet"? Too many variables, youll end up comparing apples to oranges that way IMHO.

The advice I see the most about SP is go as big as you dare, youll regret being conservative. Ask/search this in the tech and performance section, youll see what I mean. Not having first hand knoweledge with building different size SP engines, I can only pass on what Ive read from people with more experience.

 

With streetports, how much does it affect its drivability. Is it harder to drive as a daily driver, and does ur gas milage go from little to none?

 

Again, it depends on the porting. SP isint a set thing. Theres every kind from mild to wild, just like cams in a boinger.

 

BigJim, Plaese post if you find a good streetport template.I plan on porting one out and am not sure which one to use. It will need to be streetable but I ant power out the ying yang.I had a 578lift w/308 duration on my big block,Everyone said it was not streetable but it didn't bother me.It was a little tricky though.

 

Carl, I would love it to rain on my parade! Due to drought we are on tight water restrictions so washing a car at home is illegal.

Seriously, thanks for your advice. What I was looking at was the power obtained from say a RB streetport as against the cost of porting which would require a stripdown. Here that would be about US$1700. I expect to add about 30fwhp from my present set-up.

I fully agree on dyno differences the Australian ones give about 90% of the US results. Variability by climate conditions can be significant especially as where I am now 20 degree C differences during the day are normal.

I started a thread on streetport specs bue there was no useful reply. It seems to be a trade secret!

 

normal street port + 44 IDF weber carb + RB headers = 150HP? or more
thanxs

 

Here's some real world experience. I had a 12a streetport for several years. For comparison, the intake ports were slightly bigger than the Racing Beat template. The exhaust ports were rather mildly ported.

Streetporting increases intake and exhaust timing as well as increasing volume of the ports. Streetporing will therefore lower torque.

When it was stock ported when driving in normal day-to-day traffice I shifted @ 3000rpm. With the streetport I shifted @ 4000rpms. I think the rpm at which I was making peak torque was higher with the streetport. If the motor had bigger exhaust ports, there would be less torque and it would hit peak torque @ a higher rpm. BUT it would make more horsepower. I do wish I had done that, the tradeoff is acceptable for me.

Gas mileage will generally go down some with a streetport. Especially if you are on the gas pedal a lot. The way I view it, if you have a streetport, you might as well use all it has to offer!

 

From all I hear, the RB is on the mild side. I havent had anyone post their specs either. Guess it is a trade secret and I bet, Pineapple, RB, and the rest all do it a little differently.

 

Carl- this is about all the porting data I have for the 12A. other than RB there is no source of templates.

US spec 12A
IO 32° ATDC
IC 40° ABDC
EO 75° BBDC
EC 38° ATDC

European/Australian S3 specs[1984-5]
IO 32° ATDC
IC 50° ABDC
EO 75° BBDC
EC 48° ATDC

Racing Beat "Street Port"
IO 25° ATDC
IC 60° ABDC
EO 84° BBDC
EC 48° ATDC

Based on this I have no idea how mild or wild the RB port is, just it is the most common one used for streetporting.

 

Kick this around in the tech and performance section, bet youll get more milage there. I've seen many different port styles. Judge Ito uses a straight across top to his ports. Ive also seen pics of some monster SP's kickin around the net.

http://www.rotaryengineillustrated.c...-ports101.html

 

With the streetport I got on my 84' RX-7 GSL-SE...I reached 197HP.