The perfect 13bmsp exhaust port
 

PROJECT ROSEBUD

In the interest of science, and stimulating argument, I would like those here who feel so inclined to post here.

The premise:

It has been widely regarded as truth that the Renesis side exhausts are, eh, sub-optimal.

For either more HP, or better power through the gear, or a streetable combo of both.

If you had the ability and the resources, how would you change them? If you could cast or machine your own irons, or modify stock irons to whatever shape you wanted?

You must keep the same drastic 90 degree bend, side ports only, and a stock exhaust manifold must be able to bolt up. ( I know it is not the best for power. Just for consistency of argument. ) Stock rotors and seals, and seal "tracks".

The reason I am asking is that there has been a lot of back and forth on this over the years, and a lot of thought also.

I am hoping to get some good input, maybe something that no one has thought of yet. Maybe something we can eventually use?

Fire away, fellas!

Why are you saying "you can do whatever you want" but then limiting it to the side exhaust ports? I'd rather have fancy rx7 billet plates cut for the rx8 intake and use rx7 housings and see what happens. That said, I doubt it does much considering nobody is doing hybrid builds anymore. How about using a first gen rx7 center plate? Get rid of the troublesome siamese port, then play with the porting characteristics again from scratch.

A couple of things:
- widen the intermediate iron and/or place the siamese ports above one another rather than side by side to give the turn a gentler radius and widen the port itself. Adjust outer ports to match.
- cut a second exhaust port in the iron face for egr and overlap, controllable via a valve. Analagous to the aux intake ports. This gives you exhaust timing control similar to VVTLi. I don't know if it ultimately helps power but it could help emissions/driveability. EGR may be bad for deposits though.

Ok, well thank you for your input. But what would you do with the side ports to improve them, like I asked above?

That's good. Thank you.

Can't think of any way of improving them given the boundaries you set . The fact that they work pretty well up to double N/A mass flows is testament to how good the existing design actually is. As an example ..... my turbo 8 makes the same or better power than an REW with same sized turbo at same boost all the way up to 400whp. After that it's game over however.

If the centre iron could be wider and have an insert the same as the outer port ...that's an obvious improvement . But you said same manifold so ....no dice on that idea.

gonna call you on that claim; let’s see the examples you think prove it.

I'll do that ...so long as Kevin is ok with me polluting his thread . Kevin ?

Call it a brag if you like but it is relevant to his thread so less polluting than your post above ...or indeed this post.

This is not pollution at all. The idea that the port design in not inadequate is a fresh look. Let's go!

You two remind me of something...What could it be...

https://cimg4.ibsrv.net/gimg/www.rx8...9be0794e6c.jpg

LOL... whom is whom?

First up I looked up GT35R dynos on The RX7 forum. This is the same turbo as mine.


1/RESuper : https://www.rx7club.com/single-turbo...gt35r-1029909/
Gt35 T3 352whp@14psi
https://cimg3.ibsrv.net/gimg/www.rx8...3fcf6cdba8.png

2/TurboR1 GT35 1.06AR :https://www.rx7club.com/single-turbo.../#&gid=1&pid=1
431whp @ 16psi

https://cimg4.ibsrv.net/gimg/www.rx8...9555d2ebdc.png


3/Smg944 :https://www.rx7club.com/single-turbo...-gt35r-593681/
427whp @ 15psi

https://cimg9.ibsrv.net/gimg/www.rx8...016fa576ac.png

4/Jason GT35 0.82AR :https://www.rx7club.com/single-turbo...r-dyno-754690/
405whp@16psi
https://cimg7.ibsrv.net/gimg/www.rx8...0514f4a9f9.png

5/ FourtyOunce GT35r stock ports
397whp@16psi
No dyno but here is link to thread : https://www.rx7club.com/single-turbo...-ports-462634/

Now lets look at my results with a GT35r 1.01AR . I've actually dynoed my setup many times over four different dynos so may as well post from each dyno so there is no suggestion of my dyno being too optimistic.

1/PPRE 396whp @ 13psi
Note: this was first ever dyno when setup was very restricted as compared to now . To get max. power I needed to rev the engine out to higher rpm than the other dynos.

https://cimg4.ibsrv.net/gimg/www.rx8...b6c13050a6.jpg

2/HPR
415whp@16psi
386whp@13psi

https://cimg3.ibsrv.net/gimg/www.rx8...2e5817b5cc.jpg

3/Te Rapa automotive
418whp@15psi

https://cimg6.ibsrv.net/gimg/www.rx8...0b4d5e8d33.jpg

4/Dyno Power
420whp@15psi
https://cimg5.ibsrv.net/gimg/www.rx8...8ec056cf8b.jpg

First .... just to quote myself to show what Team actually called me out on : "As an example ..... my turbo 8 makes the same or better power than an REW with same sized turbo at same boost all the way up to 400whp. After that it's game over however."

Simplified Summary :
RX7s
1/ 352@14psi
2/ 431@16psi
3/ 427@15psi
4/ 405@16psi
5/ 397@16psi

Renesis :
1/ 396@14psi
2/ 415@16psi
386@13psi
3/ 418@15psi
4/ 420@15psi

Analysis :
As I mentioned , after 400whp it's game over for the Renesis due to port timing issues I've gone over in previous threads. The above results suggest it's pretty even up to slightly over 400whp. After that we know the REW starts to really shine. What is really interesting is the numbers in the 10-13psi range. This is where the Renesis is really happy and can actually outshine the average REW engine.

Did not expect that :o

Yes ...that's what I said and that's what I meant. It's called comparing apples with apples. But just for you here's a modern turbo as well at same boost level. Bit of an unfair comparison with a bigger turbo but it still stacks up
EFR8374@14.5psi ....402whp
https://cimg1.ibsrv.net/gimg/www.rx8...5fc344d685.png

Also, lets not gloss over the thread topic and why I even mentioned the above. The point being , up to a certain mass flow the Renesis exhaust ports aren't as bad as people think.
Point made ...now stop squirming Team .

Are you talking about Landspeed with the massive turbo on e85 and nitrous ? If you think that setup breaking 450 is a valid test of my theory then you really are out of touch with reality.

Getting back on topic.
Kevin : this is something I tried a couple of years ago. As my turbo setup utilised the siamese port to work with the wastegate I was able to evaluate whether it actually flowed more than stock. I found that the boost creep I was getting reduced by 1.5-2psi at peak rpm. So conclusion is ...it does flow better than stock. Whether that would make any difference in an NA scenario .... don't know.

https://cimg6.ibsrv.net/gimg/www.rx8...119f7487db.jpg
https://cimg1.ibsrv.net/gimg/www.rx8...1068d5176d.jpg

Apple to apples is comparing a gt3582 with a gt3582 .... What reality are you talking about?
And the only point of the post with dynos etc was defending my initial comment ...which, unless your head is so far up where it shouldn't be that you can't see it, I did . Comprehensively.

Even doubling the center iron size wouldn't add as much flow as the extra exhaust port on the housing, which as you said won't do it. In that case, what happens if you just eliminate the side exhaust in favor of periphreal? What happens if you dramatically change the side exhaust timing? Would either of those have more of an effect than just increasing flow on the current ports?

I have to say I'm really disappointed. I guess part of me hoped that maybe you knew something interesting that would be helpful.
I'll just say this straight up ... there is no cross contamination issue. There are other issues with the Siamese but that's not one of them.
How do I know this ?
1/ The Renesis makes great power N/A ...more than any other before it (in stock trim)
2/At double atmospheric pressure (under boost) the Renesis makes double the power it makes NA .... if there was a cross contamination problem ..would this happen?
3/ As evidenced in the above dyno charts the Renesis does just as well as a stock REW engine under boost (up to the point it falls over). If there was a cross contamination problem ..would this happen?
4/That thing you seem to think you don't need to figure this stuff out : Experience (oh wait ...you saw something in a Mazda video .....chuckle)
Did you know i've tested :
The sleeves pictured above
Sleeves with no divider (yes none , zero , nada , nothing)
Sleeves with every flow path to the opposing chamber sealed off (except for the one to the manifold of course)
Maybe four or five other iterations of Siamese sleeve trying to find some majic.
A completely blocked off Siamese port

The only time I've EVER seen a REDUCTION of power was when the entire Siamese port was blocked off. You may recall that my first turbo manifold did this (until the wastegate opened) . There was a perceptible loss of power (not much , but enough to notice) before the wastegate opened. I rectified this by changing the design to allow the gas to escape into the manifold rather than backflow into the combustion chambers.
Other than that I've never detected a decrease (or increase) in power due to any of the tests I've done. Edit : I did see a very small loss with no divider at all ...barely measurable.

So other than a video where you see a glimpse of the opposing rotor through the exhaust port (because there wasn't a sleeve there). Have you got anything to support your theory?
Some tests maybe? Some reason to suspect there actually is some kind of issue there?

Brett,

Interesting.When you tried the siamese port (conjoined to be PC) with no divider, or a limited divider, did you try it NA as well as FI?

But I wonder if without the deflector, one chamber would blowtorch the rotor of the other at some points in the cycle. So maybe a longevity issue was resolved with the port insert deflector? It seems obvious that could occur.

No ..never tried it NA . Actually on reflection , I'd like to ammend that by saying ...with no divider there was no major loss of power . I actually do remember seeing a very small loss in one iteration where the divider did not fully cover the line of sight between the chambers ...barely measurable. I didn't leave it that way long enough to see if there were long term effects as I suspected there would have been.

DUH ! of course that was why it lost power ... I didn't think I had to spell that out for you !
I've actually never seen you squirming so hard as you are right now. But I know there is no way to get anything past your armour plated noggin so it's pointless taking this discussion further. You are making assumptions based on no information. When you do have something definitive, do come back and put me straight.

That's like saying . Newtons' theory of gravity was based on apples ...don't ever try it with bananas because it wont work!
Do you think I just blindly plug numbers into that program without considering the differences that might be present between the two brands?