Well we know wont do any scavenging .... Just wondered if increasing the pulse strength of outers and decreasing the siamese would help reduce backpressure as there wouldn't be as much interference.

 

Well where are you going to block it off and how are you going to control it? For NA it won’t have the ability to overwhelm the EGR carryover effect that’s likely to occur as the exhaust pulses into that closed center port chamber area that then hit’s whatever is blocking it and bounces back in the opposite direction.

What you’re experiencing may just be a result of how your manifold is configured, which isn’t necessarily anything like an NA manifold. Again, NA with zero-overlap timing is a whole different ball game ...

 

Wasn't talking about blocking anything ...... just changing the port timing on the outers so they open sooner and fitting a normal equal length header. My thought is that it may lessen the turbulence at the merge . You then have two stronger pulses from the outer ports timed so they don't interfere and much reduced pulses from the siamese.

 

How do you intend to “change the port timing” on an NA engine then? If you mean porting them to open sooner then again, this isn’t a turbo engine and as per the one tuner who is already porting NA engines this way in an attempt to make the engine breath better, that’s a losing game NA imo because it only dumps combustion energy into the exhaust system early rather than converting it into work pushing the rotor around. Without overlap scavenging it’s wasted of energy; figuratively and literally.

I actually am completely confused by what you even mean now because unless you block the siamese port with something that can be opened later, which you’re doing with a wastegate, then there’s no chance of the port gases not interfering with each other If you mean pipe the siamese completely separate of the outer exhaust ports that was already tried and failed a long time ago.

 

I'm not talking a huge amount ...it only took 4-5mm earlier opening on my setup to make a huge difference. I could scarcely believe it that a small change like that would make such a big difference.
So I don't see that amount losing any power whatsoever ....... and there could be a slight gain in getting the gas out easier

 

Forget about wastegates and blocking things .................. the change I'm talking about is just to the outer ports ............... nothing else. Do I need to sketch it ?

 

Because you have a TURBO! It’s the energy you’re dumping early that’s driving the turbin. You don’t have than NA. With zero overlap it’s even better. Gale Banks was making 1000 hp V8 turbo street engines back in the 70s and 80s by decreasing camshaft overlap while opening the exhaust valve early (along with high lift rollers). Nobody knew how he was doing it for a long time because they were using NA cams with high overlap and sending boost out the exhaust rather than creating more power output

 

Exactly! But in an N/A Renesis ....... you have four distinct pulses and the pulse from the siamese interferes with the pulse from the outer port of the same rotor ...... What if you could reduce that interference ?
The huge benefit i saw in my turbo setup makes me think that this very small change has a big effect on the exhaust pulse dynamics and maybe there is a benefit N/A as well!

 

No, you have two distinct pulses with a third branch merging a partial stream of the two together. You’re not looking at it properly in your mind’s eye. Which again, with zero overlap it has nothing to do with any of that. You opened the exhaust port earlier and that is the energy driving the effect you’re seeing with a turbo.

 

You don't think the pipe coming from the siamese has two distinct pulses as well ? The siamese carries 35-40 % of the gases out of the engine ...that is significant.

You are probably right in that it wont make any difference. But then again ........................... just maybe ...........................................

 

It’s the same pulse as in the outer pipes, just co-mingled in the siamese branch. I still think you don’t fully grasp why zero overlap makes that meaningless relative to common NA header theory.

 

Well go ahead and show me your results then , not going there myself.

 

I want to thank both of you for continuously contributing to this forum. The knowledge you both have compiled by earning it in the real world,and then posting it here, is incredibly valuable. I am so grateful that we have thinkers and experimenters here, who still wrestle with the problems and potential of this engine, and are willing to take the time to post.Those who care can learn a great deal from you both.

 

Well you keep saying that....................... and don't seem to grasp.................................. that I'm not suggesting there will be any kind of scavenging effect. Zero overlap or not .... less backpresssure means more power, otherwise we'd all still be running stock exhaust ...right ?

 

There’s not any backpressure occurring from what you think is the cause of it. That’s something that only exists in you’re head. Go back and look at my original header. It’s totally the opposite of your idea. Again, I only went to a multi-tube design now for material heat expansion flexure. Otherwise all that other header theory stuff is completely out the window, but like everyone else you just can’t let it go ...
.

 

Ok ...... I do get what you are saying .
But if there is one thing I've learned over and over from all my experimentation with this damn engine , it's that things hardly ever turn out how I expect them to. I did find out however, that changing the outer exhaust port timing has a major effect on pulse dynamics. Of all the things I tried that was the only one where I saw a big change.
Even though I think you are probably right , If I were building an N/A engine, I would still try it.

 

well of course, because again, with a turbo it’s an entirely different scenario; it’s highly dependent on how the energy is transferred to the turbine. That doesn’t exist on an NA engine. It just has to be as free flowing as possible, which the pulse timing has no influence on. That’s entirely a scavenging resonance effect.

 

I guess that's what I don't understand ............. if pulse timing improvements can improve scavenging .......why wouldn't it decrease back-pressure ?

 

Well don’t get upset because there’s not really any other way to say it; that’s the difference between thinking you know something and actually understanding it

 

Brettus, are you thinking of trying to keep the trough of the pulse from R1 matched up with the peak of the pulse from R2?

I agree that this isn't possible without equal length primaries. I also don't know how you accomplish this with the siamese port regardless of manifold configuration.

Also, I'm guessing that Team is saying that if you can keep flow restriction low enough, trying to manipulate pulse timing will be a wasted effort because it won't make a difference big enough to be measured without incredibly expensive analytical equipment.

 

I’ll repeat myself again; that’s a resonance feature to enhance scavenging. Scavenging isn’t possible without timing overlap. It otherwise has no influence on backpressure. Again, the header manifold design I built in 2006 is the exact opposite of what’s being proposed. Just as the OE manifold is. I’m entirely convinced that the Mazda engineers recognized this. All the resonance on the NA engine occurs on the intake function. Why would they invest so much resources into the intake and ignore the exhaust if there was value there? Occam’s razor is slicing you into shreds ...

 

Yah, I'm pretty sure you two are debating two different concepts.

Brettus is probably thinking that two pulses arriving at the merge at the same time would create a momentary high backpressure as the two peaks combine. Setting them up to be out of phase such that peaks and troughs line up instead would (in theory) prevent this. This isn't about scavenging (where overlap on the exhaust and intake phases allows the exhaust pulse to help pull in extra intake charge) so much as about fine tuning little theoretical details and seeing if any beneficial effect can be teased out of the noise (no pun intended).

Team is wondering why anybody is talking about resonance because scavenging isn't possible.

I think Team's point about Mazda engineers having wrung all of the performance possible out of a production design still applies. If getting the exhaust pulse phase perfect made a meaningful difference, Mazda probably would have included it in their production design.

 

Pretty sure you both lack a full understanding. Really nothing more for me to add. Opening the exhaust port earlier is self defeating for NA imo. You want to invest all that into a new engine and reap the rewards then happy unicorn hunting.

 

This feeling is mutual.
It's interesting to see how your confidence in your own superiority gets in the way of your understanding of others and the ideas they are trying to present. You're so busy trying saying how correct you are and getting frustrated that people don't simply accept your brilliance that you end up pretty close to the region of "not even wrong". You're arguing a different point. It would be a straw man except it doesn't really even resemble what Brettus is saying.

(And see how I typed all these things without a single "****", "****", or "Goddamn"? Aren't you proud of me?)

 

Well put ,that's it exactly.
Obviously , if there was a reduction in backpressure it wouldn't be as effective were scavenging possible , but there must still be a small gain there.
I can see Team has gotten impatient and is now resorting to his usual tactic of belittling all who would defy his magnificence so not much point debating this any further.