rx8frank

I know that mazda did an excellent job with their intake and exhaust port with the renesis...but can the ports be again improve in some way to give more hp ???
Is there anyone here who did a successfull porting on their renesis ???

rotarygod

It would be very hard to make the Renesis intake ports appreciably larger. You can't go outwards at all as you'll lose a corner seal to the hole and you can't go inwards as you'll cross an oil seal track. There isn't any point in porting downward as flow is terrible in this direction. This means that you can only go up which is closing it later. You can't do much here either but a little bit. For the most part you should just go in and clean up the roughness a little bit but as for port size, not much can be done or is needed. The Renesis intake ports are 40% larger than those in the last 13B so they need to severely port their engines just to get up to what the Renesis comes with stock! Mazda has for the most part maxed out the porting on the Renesis.

The exhaust ports are what need some work. The shape is terrible for flow. I have no doubt that we will see gains when these are worked on but as of yet there has been nothing truly changed about them by anyone. At least no one that has reported on the effects of it.

A few engines have had some port work done to them. one that I can think of was turbocharged so it's hard to say what improved from porting and what improved from boost. Another one was naturally aspirated and while it picked up a lkittle power, it wasn't tuned properly. We don't have much solid evidence as of yet.

rx8frank

Well thanks I kinda expected the answer but we never know some poeple makes miracle
And for the exhaust port I agree with you... I think the flow kinda goes 90 degrees or something. But don't a fine tuned aftermarket exhaust manifold would help???

Philip_SA

I agree, there is not much to do rather than if you do have it open then just clean it up and make sure all fit perfectly. manifold to motor etc, no missmatch.
I heard a maximum of about 6-8Hp with porting, (the bit that can be done) thats it.

just do the add ons, revi, exhaust, flywheel, and I say Microtech Lt12 for engine management, because I know what it did for my RX7 turbo 2 years back


Philip

guitarjunkie28

hey, the few i've ported the exhaust on are not only getting more power, but better fuel economy as well! there's good things to be had with the porting, but most of it is runner work-instead of enlarging the port oriface tremendously.

Sapphonica

My GReddy 8 is ported, and as RG said, most of the work went into the exhaust ports.

However, the 18g turbo shipped with the GReddy kit flows only a small fraction of what the engine is demanding, especially at higher RPMs. Power actually drops off after 7500 RPM.

Once I get a sufficient turbo bolted on, then we'll have a reasonable data point on power gains. It's obviously flowing a LOT more, and I'm making 8# of boost well below 3000 RPM.

rx8frank

Did you ported your exhaust before having the greddy kit ??? If yes, at the time did you see a big difference???

Sapphonica

No, I ported after getting turbo'ed as part of an engine rebuild.

rx8frank

Did you try to adjust your wastgate to controle the flow

rotarygod

Frank, if you want to quote someone, it's easier to just look at their post and then go down to the bottom right corner of it and click the "quote" button. That will automatically insert the quote into your response.

dgrx8

can u be a little more specific as to what work was done to these 8's? also, how much is the cost of labor for this?

Sapphonica

Of course. With the wastegate actuator rod tightened all the way AND 100% duty cycle on the boost controller valve, boost drops off. The turbo simply can't supply the cfm the engine is capable of flowing.

Also, we had to lower the duty cycle a bit because the turbo was making nasty sounds when we were pushing it that hard.

The cool thing is that its obvious to us all that the porting increased the flow capacity quite a bit.

evilmiata

Sapphonica, would it you describe your modification more as smoothing/blending, or actually hogging out swathes of metal?

guitarjunkie28

just search around in this forum-there are a few threads on it.

the porting is cheap, but it entails an engine rebuild and r&r...that's the expensive part. i have one done on the stand, though. i was gonna use it in a 2nd gen rx7, but i can do trade-ins with it.

rx8frank

Yes I know I guess I did something wrong this time usually it works

mike1324a

Ive heard of an estimate from a shop who specializes in rotaries and porting, this might be a little exaggerated, but they said 20% more power with a proper tune. I havent seen any real evidence if this is true though.

F22C1

What about Bridgeporting to both intake and exhaust? Are there coollant passages in the way?

guitarjunkie28

20% is pretty optimistic, unless they're talking about a p-port.

bp'ing the exhaust is out of the question.

mike1324a

I thought it did too but if it is agressive maybe its possible. Im not a porting pro tho. But if it makes 180 to the wheels and 20% of that is 36whp equaling 216 to the wheels. Now considering how much power the 8 is supposed to have that doesnt seem as far fetched but again, im not a pro tuner.

guitarjunkie28

maybe if they're comparing a bone stock rx8, with the factory computer running the afr's in the 11's to a ported motor with an ems and exhaust... i could see 20% out of that.

mike1324a

^^^ Thats what they were saying.