This probable a stupid question but whats the measurement of a stock throttle body and would upgrading it gain power????

 

You won't gain much with a bigger throttle body in a NA or common turbo application. You can polish it a bit to gain something very little that you definitely won't notice though
I don't remember the diameter at hand, sorry.

 

think 75mm, and no unless you went boosted with a good tune, ^^ kinda what he said

 

In the inner circles of those very smart and experienced people who have tested and tried things with the Renesis you will find the stock intake system (the entire system) has very little room for improvement. There are a small handful of very, very smart engine builders who have worked with willing customers to try things and have come to this same conclusion: A very sensitive harmonic frequency exists within the stock Renesis system that if disrupted or changed yields less than current flow and it makes less power.

This is only going to make sense to a few people on this forum. I can share with you that I've had discussions with some of these guys as they themselves have tried that which has worked on past 13B ported RX7 engines with the Renesis and come up empty. Personally, I think one of the reasons this occurs with the Renesis is the multichambered intake with its various runners, runner lengths, valves, and actuation of these valves at different rpm. I have spent a fair amount of time with acutating these moves in difference sequence and at different rpm in search of legal racing hp and have always come back to the stock design (+/- a few rpm change). These engines like velocity, not volume.

Here is a rudimentery explanation of what I'm referring to.

http://en.wikipedia.org/wiki/Helmholtz_resonance

If it were me, I would measure what you currently have, make your swap/test your idea and then measure again and honestly compare your findings. I beleive you'll come to the same conclusion.

 

What you said is mostly true Eric, however there is still work that can be done. Overboring the throttle body won't give good results, polishing it a bit will. Of course there are minimal increments to be had there that are less than noticeable.
We played a lot with the intake manifold. We have built some longer and shorter upper intake manifolds and the results are fun to watch and study.
My favorite combination is that of a polished and port matched lower intake manifold with worked APVs, stock upper manifold and AEM\Ms intake, power curve wise.

 

Thanks for the info just 1 last question even if I upgraded the throttle body to 90mm with a cold air intake it still won't gain noticeable power?

 

i believe your air/fuel will be so outa wack, and very unstable on a tune..

 

you can also check rotarygod's long winded posts on Helmholtz tuning and the rx-8. Basically there isnt much in the way of improvement you can find and much you can easily screw up.. you can move the power curve around for various performance reasons but not much else.

 

Thanks every 1 so it not worth it really basically

 

[QUOTE=bse50;3868504]What you said is mostly true Eric, however there is still work that can be done. Overboring the throttle body won't give good results, polishing it a bit will. Of course there are minimal increments to be had there that are less than noticeable.
We played a lot with the intake manifold. We have built some longer and shorter upper intake manifolds and the results are fun to watch and study.
My favorite combination is that of a polished and port matched lower intake manifold with worked APVs, stock upper manifold and AEM\Ms intake, power curve wise.[/QUOTE

Is there a RX8Club thread on your findings with data?

 

I don't think so, maybe there's something I said in BDC's old throttle body porting thread. Since i don't do it with business in mind i barely talk about this stuff
I may have some pictures on my old pc though, feel free to PM me your email and i'll send them to you!
We're talking about marginal gains anyway. less than 3 g\sec for the polished and smoothed out throttle body so nothing spectacular and within sensor error i'd say.

 

Screwing with the throttle body wouldn't screw up your MAF voltages. Not in any major way at least. I'm pretty sure it would be well within stock limits.

You might get a little throttle response, but if the throttle body isn't a restriction in itself, then opening it up won't get you more power.



I have done throttle body smoothing on a couple of different cars, and the results were pretty good. Granted, they had a pretty good step on the inside of the bore, and a 5mm or so lip going from the intake to the throttle body. Smoothing those out gave a nice increase in low RPM power, but they felt the same up top. It was a nice mod for free though.








Mmmmmm... Helmholtz resonation.... Mazda did do a very good job of tuning the RX-8 to the max.