Is porting for power a myth?

Any form of normally aspirated power mods.
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Re: Is porting for power a myth?

Post by Ryan Rotary Performance » Wed Dec 05, 2018 9:31 am

I think this thread concludes that porting does make more power, albeit more difference on a 4 port than a 6 port engine :)

viewtopic.php?f=205&t=78656

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Re: Is porting for power a myth?

Post by ChrisHolmes » Wed Dec 05, 2018 1:50 pm

Less ports = more driveable power!
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Re: Is porting for power a myth?

Post by Ryan Rotary Performance » Wed Dec 05, 2018 2:22 pm

ChrisHolmes wrote:
Wed Dec 05, 2018 1:50 pm
Less ports = more driveable power!
I actually think the 4 Port, once its had our magic, is the better road car, only if coupled with the 6 speed box. We can also put the 4 port engine in the 6 Port Chassis with no issues.

The 6 Port engine on the other hand will make a better track car. (for now)

All this is subject to our 4 Port stage 2 modification which I think will see the 6 port become redundant come rebuild time for many.
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Re: Is porting for power a myth?

Post by warpc0il » Wed Dec 05, 2018 4:41 pm

Many builders choose the 4-port engine as the basis for FI installations.

Turbo or supercharging makes the original intake redundant and pressurisation means that you can flow more than enough air without the extra ports and their complexity. Most also keep the 5-speed 'box because they believe it to be stronger; at least for handling torque if not higher revs.
All replace the rear stationary bearing for the 231-specification part.
Some replace the flywheel and counterweight for 231-spec parts, but that's mainly because you can't get (most of) the performance clutch options in 192-fit.
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Re: Is porting for power a myth?

Post by PeteH » Wed Dec 05, 2018 6:05 pm

The 5 speed box is basically the RX-7 box (I think). Does that mean the 5 speed clutch is also the RX-7 clutch? If so, I don't understand the lack of high performance clutches. You'd have thought there would be some serious clutches out there for the tuned RX-7s...? What am I missing? :-k
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Re: Is porting for power a myth?

Post by warpc0il » Wed Dec 05, 2018 6:16 pm

The clutch has more to do with the engine/flywheel than the gearbox.

This means the Renesis 192 clutch is not the same as the RX7

The 5-speeds boxes are also more different than people think.

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Re: Is porting for power a myth?

Post by Szerelem » Sat Jan 05, 2019 11:59 am

Whats the consensus on japanese tuning options and ports, im sure its very similar to UK? Actually the mass depreciation in the UK lead to readily available engines which has given us some of the best rebuilders and researchers around in my opinion.

Anyway those in the know check out
seems the Fujita Engineering FEED car is already 219bhp straight away, but the weird thing is to my layman eyes i'm sure none of these cars are full bridged. Amemiya (Not in this video) but they claimed 250ps , 240+bhp which has to be balderdash....right?
I've always been curious about what they are doing internationally, knowledge is power etc. But as I say above, i think given any opportunity the rebuilds and specialists we have here in the UK are some of the best around.

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Re: Is porting for power a myth?

Post by warpc0il » Sat Jan 05, 2019 12:12 pm

Don't forget that the Japanese use a different calculation for power than the rest of the world, which is why the 4-port is rated at 210 in JDM but 192 everywhere else.

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Re: Is porting for power a myth?

Post by 13Black » Sat Jan 05, 2019 12:15 pm

And different dynos read differently and different operators will probably get somewhat different results and different days may produce different figures and....

Yeah can we all stop getting hung up on numbers thrown around that various dynos spit out - it's not what they're for, for good reason.
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Re: Is porting for power a myth?

Post by Szerelem » Sat Jan 05, 2019 3:24 pm

warpc0il wrote:
Sat Jan 05, 2019 12:12 pm
Don't forget that the Japanese use a different calculation for power than the rest of the world, which is why the 4-port is rated at 210 in JDM but 192 everywhere else.

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Really? Man thats crazy :-k

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Re: Is porting for power a myth?

Post by Szerelem » Sat Jan 05, 2019 3:27 pm

13Black wrote:
Sat Jan 05, 2019 12:15 pm
And different dynos read differently and different operators will probably get somewhat different results and different days may produce different figures and....

Yeah can we all stop getting hung up on numbers thrown around that various dynos spit out - it's not what they're for, for good reason.
It was just the quick example i could pull from memory, im actually 95% in the "how it feels" camp over the actual math, ive just always been curious to japanese tuning methods vs uk development. How they have approached porting the Renesis, as it seems there is still some kind of thin veil of mystery around it, although maybe its just the language barrier.

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Re: Is porting for power a myth?

Post by cib24 » Sat Jan 05, 2019 3:46 pm

Szerelem wrote:
13Black wrote:
Sat Jan 05, 2019 12:15 pm
And different dynos read differently and different operators will probably get somewhat different results and different days may produce different figures and....

Yeah can we all stop getting hung up on numbers thrown around that various dynos spit out - it's not what they're for, for good reason.
It was just the quick example i could pull from memory, im actually 95% in the "how it feels" camp over the actual math, ive just always been curious to japanese tuning methods vs uk development. How they have approached porting the Renesis, as it seems there is still some kind of thin veil of mystery around it, although maybe its just the language barrier.
No, there isn't any unique difference between how shops in Japan, Aus, NZ, USA or the UK port the renesis. If there was a way to extract more power without going to a peripheral exhaust port setup then it would have been figured out by now.

Just enjoy the Renesis for what it is but don't try to make any significant power out of it with porting. It doesn't really work.
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Re: Is porting for power a myth?

Post by Eddie_r32 » Sat Jan 05, 2019 3:53 pm

cib24 wrote:
Sat Jan 05, 2019 3:46 pm

Just enjoy the Renesis for what it is but don't try to make any significant power out of it with porting. It doesn't really work.
My full RRP bridge was worth every single penny
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Re: Is porting for power a myth?

Post by Szerelem » Sat Jan 05, 2019 4:13 pm

Thanks for the info,
I do enjoy my rx8 for what it is, great fun. :thumleft:
I wasn't posting looking for some miracle from the east porting bible, it was just a curiosity to see and compare their approach.

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Re: Is porting for power a myth?

Post by 13Black » Sat Jan 05, 2019 4:27 pm

Have to bear in mind that the grey one in the video has some kind of aftermarket ECU it seems, and a shorter diff. One of the white ones appears to be very standard but making good peak power, however the yellow one is quite down but still very stock it seems. No mention of how old and used they all are, how good their ignition is, if they're otherwise healthy etc. The rest of the Japanese is all Japanese to me so who knows what else they're divulging.

They only list the peak power too, which is somewhat useless as all you're displaying is how much power it produces across about 200 revs... which is about 1/20th of the range you're actually using.

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Re: Is porting for power a myth?

Post by delta0 » Mon Jan 07, 2019 8:33 am

Szerelem wrote:
Sat Jan 05, 2019 3:24 pm
warpc0il wrote:
Sat Jan 05, 2019 12:12 pm
Don't forget that the Japanese use a different calculation for power than the rest of the world, which is why the 4-port is rated at 210 in JDM but 192 everywhere else.

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Really? Man thats crazy :-k
They use JIS standard and we use DIN (~95 DIN = 105 JIS). That is why the 250ps is 228bhp here.
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Re: Is porting for power a myth?

Post by Dr. FrankenRex » Mon Jan 07, 2019 9:06 am

Who cares about power when your car BRAPS?!
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Re: Is porting for power a myth?

Post by Velocity_Dan93 » Mon Apr 08, 2019 12:50 am

Dr. FrankenRex wrote:
Mon Jan 07, 2019 9:06 am
Who cares about power when your car BRAPS?!
8) 8) 8) me
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Re: Is porting for power a myth?

Post by Dr. FrankenRex » Mon Apr 08, 2019 9:02 am

I mean, don't get me wrong, I wouldn't say no to both...

That said, the theory is that the brap-a-liscious-ness of the Race Extension is that it can deal with higher temps, meaning more reliable FI applications on a full renesis platform.
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Re: Is porting for power a myth?

Post by Velocity_Dan93 » Mon Apr 08, 2019 9:43 am

Dr. FrankenRex wrote:
Mon Apr 08, 2019 9:02 am
I mean, don't get me wrong, I wouldn't say no to both...

That said, the theory is that the brap-a-liscious-ness of the Race Extension is that it can deal with higher temps, meaning more reliable FI applications on a full renesis platform.
I might know the location of a spare greddy turbo kit if you’re looking to experiment :P
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Re: Is porting for power a myth?

Post by Dr. FrankenRex » Mon Apr 08, 2019 9:45 am

Haha, cheers for the offer, but I'm waiting for Josh to be the guinea pig this time. I was guinea pig last time :lol:

Unless you're offering it on loan to play with... ;)
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Re: Is porting for power a myth?

Post by Velocity_Dan93 » Mon Apr 08, 2019 9:54 am

Still debating if it going to have to be used on mine if I don’t get the numbers I want :twisted:
Maybe later this year we could figure something out, all about R&D/ pushing the limits
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Re: Is porting for power a myth?

Post by PeteH » Mon Apr 08, 2019 11:01 am

Well, there's only one way to prove that Dan...... 8)

Before you do though. Braps come from overlap. That means, the exhaust port and intake port are both open at the same time (something the OE Renesis specifically avoids). My understanding is that this means the pressurised intake is regularly "opened to atmosphere", and some of the FI boost is therefore lost directly down the exhaust port. I'm no porting expert, but I think the general plan with boosted porting is to ovoid overlap, and not extend the opening duration very far either (basically, rather conservative porting). You don't need "pulse tuning", and you can just let the boost do the work. I think the port to concentrate on is the exhaust, which needs to be opened as early and as wide as possible. In a Renesis I think this means running the port walls perilously close to the water galleries, which is why all big power rotaries run peripheral exhausts.

On the subject of the Greddy, this is very much at odds with a Bridgeport. The Greddy cannot push enough air to support more than about 220 to 240bhp. It can help a stock Renesis produce this power as low as 6000rpm, but after that point the power curve is flat, and the torque drops massively. So, just as the Bridge is wanting to get into it's stride the turbo is running out of puff. And, since the Bridge is actively bleeding boost at low revs, it will destroy the Greddy's one party trick (mid-range torque). A seriously bad idea imho.
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Re: Is porting for power a myth?

Post by Velocity_Dan93 » Mon Apr 08, 2019 11:13 am

PeteH wrote:
Mon Apr 08, 2019 11:01 am
Well, there's only one way to prove that Dan...... 8)

Before you do though. Braps come from overlap. That means, the exhaust port and intake port are both open at the same time (something the OE Renesis specifically avoids). My understanding is that this means the pressurised intake is regularly "opened to atmosphere", and some of the FI boost is therefore lost directly down the exhaust port. I'm no porting expert, but I think the general plan with boosted porting is to ovoid overlap, and not extend the opening duration very far either (basically, rather conservative porting). You don't need "pulse tuning", and you can just let the boost do the work. I think the port to concentrate on is the exhaust, which needs to be opened as early and as wide as possible. In a Renesis I think this means running the port walls perilously close to the water galleries, which is why all big power rotaries run peripheral exhausts.

On the subject of the Greddy, this is very much at odds with a Bridgeport. The Greddy cannot push enough air to support more than about 220 to 240bhp. It can help a stock Renesis produce this power as low as 6000rpm, but after that point the power curve is flat, and the torque drops massively. So, just as the Bridge is wanting to get into it's stride the turbo is running out of puff. And, since the Bridge is actively bleeding boost at low revs, it will destroy the Greddy's one party trick (mid-range torque). A seriously bad idea imho.
If i hit figures in the middle of that range I’ll be happy :)
The greddy is a pile of @ss tbh. Needs an extra support bracket on the manifold to say the least ! That being said, it’s the best bolt on fi upgrade for the rx8 available, just doesn’t play well with anything else lol. I think with the BNR upgrade to the greddy kit it would be capable of much more but then I’d run into heat issues which I really don’t wanna do. Despite my in the name of science approach I’m really sentimental about the engine and now the last thing I want it to blow it up.
From what I’ve read and experienced, a street port is the best port you can get. Much better drivability and it would play nicer with the turbo. I can’t say if I could go back and do it all any different but for me street>bridge
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Re: Is porting for power a myth?

Post by ChrisHolmes » Mon Apr 08, 2019 12:21 pm

When rebuilding my SC engine I am intending to leave my port shapes as original and just clean up the runners smoothing the curves. The current irons ports are RB outline but very steeply angled into the runner, or out depending on your outlook!
I will also be checking the exhaust port to RB manifold transition area for any “steps”
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