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Ok, so now let’s take it to the next level. In summary of the previous post I made regarding Renesis port timing relative to the 13B REW, Mazda mostly advanced the phasing of the intake and exhaust ports in the combustion cycle.
Where the REW exhaust port closed at 48 deg ATDC, on the Renesis it closes at 3 deg BTDC; advanced 51 deg
Where the REW primary port opened at 45 deg ATDC, on the Renesis it opens at 3 deg ATDC; advanced 42 deg
Where the REW secondary port opened at 32 deg ATDC, on the Renesis it opens at 13 deg ATDC; advanced 19 deg from about 4000 rpm and up
Just for clarity, the Renesis APV port opens at 38 deg ATDC
Let’s start with the unmodified Renesis engine. It has no overlap between the exhaust port closing at 3 deg BTDC and the primary intake opening at 3 deg ATDC; a 6 deg separation. Whereas the REW port closes at 48 deg ATDC and the primary intake opening at 45 deg ATDC; 3 deg overlap. The one critical aspect of this that’s different between the two is the position of the rotor. When Mazda advanced the intake and exhaust phasing on the Renesis, it now occurs right around TDC; where the combustion chamber of the rotor is at it’s minimum volume. Whereas on the REW and earlier 13Bs it’s happening about 45 deg later when the volume is expanding for the intake cycle to take place. This is a big deal, especially for forced induction.
So think about a turbo REW which at some point is going to have exhaust back-pressure. Even though the exhaust port stays open for 48 deg past TDC, the rotor combustion chamber is expanding as the exhaust port opening is becoming smaller. So the net combustion chamber pressure is decreasing at the point the primary intake port is opening, helping to minimize back-flow into the intake system.
Rotor position and expanding chamber volume as 13B intake port opens
On a Renesis though, this same event is taking place right around TDC when combustion chamber is at a minimum and pressure is highest. Even though there is zero overlap, any remaining pressure in the combustion chamber when the exhaust port closes will be released into the primary intake port 6 deg later which for all basic purposes is still TDC. The pressure is not relieved into an expanding volume like on the REW. On the Renesis, it will instead be immediately released into the primary intake port.
Renesis is still essentially at BDC with minimum chamber volume when intake port opens.
Those of you who understand my Renesis exhaust manifold theory can perhaps better grasp why I had stressed that it was best to get the exhaust gasses out with the least amount of resistance/back-pressure. You can’t scavenge a closed chamber; the Zero Overlap condition, and the exhaust port closes slowly at the end with an every decreasing opening area. Some people theorized you could pulse tune a wave to hit at the closing, but because of the actual conditions that will never work. It can only occur if the port could be instantaneously shut from below ing widely open right as the pulse hits. Even then it’s still trying to pull a vacuum on a closed chamber. They don’t understand the difference between the energy of the pulse and the energy required to pull a vacuum. It simply can never happen. Nobody was listening when they were told that.
So that’s NA. What about FI on the Renesis? Well it’s the same thing. Any back-pressure that’s trapped in the combustion chamber when the exhaust port closes is immediately released into the primary port 6 deg later. Even if you think a way around that is to fill/block the primary port, the secondary port opens only 9 deg later. The rotor has progressed around some towards the intake cycle, but is still so close to TDC that it won’t be a huge difference, but it might offer an advantage. I had thought with a blocked primary port maybe combined with modifying the UIM to allow limited flow from the primary port runner over to the secondary runner, which would then transition to full secondary runner flow when the SSV opens, might be worth investigating. Still unsure on that though.
However, once we pair 13B rotor housings with Renesis plates to form a hybrid the impact is huge, as noted before. Not only is the exhaust port still open when the primary port opens at 3 deg ATDC, the secondary port opens only 9 deg later from 4000 rpm up, and even the APV has some overlap too from 6000 rpm up. Even though the combustion chamber is expanding, both the intake and exhaust ports are open at the same time for a very long period. There’s a lot of combustion gas dilution and back flow into the intake because of too much overlap too early in the intake cycle and imo all the results bear this out. This is why I stated previously that using a big turbo with a large A/R turbine housing and higher rpm range is the only way 13B housings with Renesis plates will ever work. That’s pretty much how it’s done with a P port intake and forced induction on a rotary.
Great find posnake . Really good that he did the video ....it clears up a few things and really does show the idea has merit.
A few things :
1/I totally believe the 435whp but kinda skeptical about the 11psi .... would like to see that repeated. Going back in the thread they talk about 14psi so dunno where he got 11 from. https://www.rx8club.com/series-i-maj...7/#post4025674
2/ As I've mentioned in the past ...the spoolup is terrible (turbo wasn't that big either) . Which is ok for a race engine but needs to be considered if it's for a street car.
3/Comment about less heat in exhaust area being good for longevity - great point.
4/Totally agree re the studding ....... although I use dowells which aren't quite as good. More turbo guys need to take on this advice.
5/The small amount of porting shown(not the BPs) ..I believe is effective for a small N/A gain .
There’s nothing impressive about the high rpm/narrow output seen here and it only exemplifies my explanation. If you really understood the what I posted then the boost pressure is no surprise at. Of course it’s low; it leaks air like a sieve with nothing to hold it back and of course the powerband is high and narrow for the same reason. That wouldn’t be fun to drive around town in either. Being forced to a forward top mount isn’t helping. None of that will likely penetrate the tungsten-filled skulls here though. Glad it’s not my money being thrown down the drain.
If you really understood the what I posted then the boost pressure is no surprise at. Of course it’s low; it leaks air like a sieve with nothing to hold it back and of course the powerband is high and narrow for the same reason.
If you had thought about this some more , you would also be questioning the 11psi claim.
Firstly ...how big was the turbo? Couldn't find any info on it but it would have to be a monster to flow that kind of air at 11psi with any semblance of efficiency. The turbo in the pics looks pretty small so......
Next ...... if air is leaking through the engine as you suggest ........... how the F*** does it make any power ? You do realise that air has to go through combustion to make power right ? And if it is leaking through ...... how much extra air would the turbo have to flow to service that? ... see previous point.
Then there is the fact that all previous posts in this thread suggest it needed 14psi to get 410ish whp (see my link above)..... How does that magically drop to 11 and then make even more power?
BTW ..... for years Turblown were claiming their Renesis top mount GT35 kit was making 420+whp on 11psi as well. I called BS on this and was ridiculed , yet many years later they come out with the efr8374 kit and needed 20psi to make the same power (albeit without the APVs). Figure that one out !
if the town you live in doesn’t have any traffic lights or other considerations to keep you constantly below 35 mph maybe, unless you think screaming around in 1st gear is fun
I recommended the 9180 for a reason. 435 whp is only about 57 lb/min. A TD-61 can do that at 1.75bar. Or just barely, but I only emphasize it as a single point. plenty of turbos can do that and more. It’s not a small turbo, the issue is it’s not big enough. I suspect most people here don’t understand rotary port timing in general, overlap even less so. Let’s rehash it again; the primary Renesis port opens at 3 deg ATDC compared to the REW primary which opens 42 deg later. The Renesis secondary isn’t much better opening at 13 deg ATDC compared to the REW secondary opening about 20 deg later. i explained all this before. It has no lowend power and then finally catches on at high rpm. Why do you think that is? Let me just say that rotary overlap with turbo is not new. It’s just not understood very well by some people as seen in the comments being made.
With the factory peripheral exhaust port overlap can’t be avoided; it can never be zero regardless of where the intake ports are placed. Or at least not and have sufficient timing flow for performance. Because in order for that to happen theyd have to be located where the rotor is in the compression phase. it would be blowing back into the intake or other chamber instead. That’s the issue with peripheral ports. There’s only 90 deg of intake timing phase, but a triangular rotor results in the apex seals being spaced 120 deg apart. There will always be overlap with a peripheral port so all you can do is try to minimize it. Except when you add it to Renesis plates, which have the intake ports phased to open way earlier it does the opposite of that. This motor then has bridgeporting too. Compounding it further still.
435 whp is only about 57 lb/min. A TD-61 can do that at 1.75bar. Or just barely, but I only emphasize it as a single point. plenty of turbos can do that and more. It’s not a small turbo, the issue is it’s not big enough.
The 57lb/min seems a little light given your insistence that there is a heap of air "leaking like a sieve". Where did you think that extra air would come from .... out of a unicorns butt!?
But lets assume that is the real number anyway and it was the TD-61 at 1.75PR (not bar) as you say. I looked up the compressor map for that turbo and found yeah ...it could do it, but it would be operating off it's efficiency island by a fair margin ..maybe at less than 50%. Do you realise what that means in terms of heat generated? Doesn't that sow a seed of doubt in your mind over the 11psi claim?
The rest of your last post is just repeating and regurgitating a wall of text, seemingly as a method of confusing people ...cuz there's very little in there of any relevance.
I'll leave you with a repeat of my own seeing as you didn't address it last time : "Then there is the fact that all previous posts in this thread suggest it needed 14psi to get 410ish whp (see my link above)..... How does that magically drop to 11 and then make even more power?"
Brettus, you couldn’t be more wrong. Stop acting like you’re an expert on me, what I know or don’t know, what I’m doing or not doing, who I may or not be doing it in consultation with, and so on. I spelled a lot of it out for you and everyone else and that’s still not good enough. Where has anyone ever laid out the Renesis port timing in this manner before? It was right in front of everyone’s face all these years too. I didn’t have to publicly post it up either.
Again, it’s the NA manifold scenario all over again. Believe and post what you want, but don’t expect me to carry on a conversation with you over those kind of silly posts.
Just add this though; I contacted Mazdatrix about this exhaust flange in 2015 and had the good fortune that they more or less blew me off on it. My understanding then wasn’t what it is now.
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As far as I'm concerned the ONLY thing in contention here is 435@11psi so:
"Then there is the fact that all previous posts in this thread suggest it needed 14psi to get 410ish whp (see my link above)..... How does that magically drop to 11 and then make even more power?"
Give me a satisfactory answer to that question........... please.
I really haven’t followed the history on this closely. If that’s accurate then my suspicion/guess is the turbine side of it. The more overlap, the less turbo manifold pressure friendly it is. And this engine has a lot of overlap.
But I was only coming back to post this for anyone else who thinks they can prove something with this combination.
I really haven’t followed the history on this closely. If that’s accurate then my suspicion/guess is the turbine side of it. The more overlap, the less turbo manifold pressure friendly it is. And this engine has a lot of overlap.
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Well read up then because you you are dismissing my argument without all the facts! I'm at a loss to see how your explanation answers the question. One day it needs 14psi to make 413 ...the next it only needs 11psi to make 435...... Same engine -same turbo as far as I know(but could be wrong on that). I'm actually stunned you of all people can't see the anomaly there.
Next question...... because you never answered it :
"The 57lb/min seems a little light given your insistence that there is a heap of air "leaking like a sieve". Where did you think that extra air would come from .... out of a unicorns butt!?"
The point here being ...you can't say it only uses 57lb/min to make 435 AND it "leaks like a sieve" ...the two things are mutually exclusive. Either .........................it only uses 57lb and doesn't leak ..... or................ it uses way more than 57 and does leak ! Which is it ?
sigh, I’m entirely ok with you believing it’s me who is lost, and also the same for anyone else who wants to jump in and be joined at the hip with you.
Hilarious!
Now have a look at a real life one for same turbo from a respected member on the rx7 forum:
Blue T11 "Here is the initial dyno at 26psi boost.
I have the 13psi springs in the wastegate because I want to be able to run low boost on pump gas and then turn up the boost on race gas.
The low boost wastegate springs are probably a contributing factor on the boost fade this set up has. It hits peak boost fast, but then fades down. We turned up the manual boost controller and both peak boost and faded boost rose about the same so we went ahead with the tuning session.
Final dyno (shown) is 26psi peak boost and fading to ~20psi from memory."
Edit : actually I see you have posted several times on that thread so you obviously were aware of it. You should check the first post in particular again though and then look at the result you posted above and ask yourself if 12.5 looks legit.
Yes, that’s BlueTii’s REW engine and yes, I’ve commented a lot on his setup and am well familiar with it. The dyno graph posted above is somebody else’s REW engine configured differently that I never presented before.
So no, you don’t understand as I’ve attempted to explain multiple times now and as a result have made an incorrect conclusion. It is legit and Blue Tii both acknowledged and understood the difference as such. In fact, a number of the most experienced and knowledgeable people on RX7Club also understood and accepted the results. Elliott (Turblown/Turbosource) was also involved in the discussion.
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Yes, that’s BlueTii’s REW engine and yes, I’ve commented a lot on his setup and am well familiar with it. The dyno graph posted above is somebody else’s REW engine configured differently that I never presented before.
So no, you don’t understand as I’ve attempted to explain multiple times now and as a result have made an incorrect conclusion. It is legit and Blue Tii both acknowledged and understood the difference as such. In fact, a number of the most experienced and knowledgeable people on RX7Club also understood and accepted the results. Elliott (Turblown/Turbosource) was also involved in the discussion.
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So what WAS done to the engine to get these magical results ? How about some links to all this understanding and acknowledgement ?
Ok ... I found it . Turns out it had a half bridge (most likely street ported as well but no mention of that) .
Comparing with the results of Ludwig in the thread I linked above where he made, with the same turbo, 420ish at 20psi with E80 on a stock port engine. Plugging that information into matchbot I found the stock engine needed a Ve of 95% to achieve that result. To get the same whp (allowing 60hp drivetrain loss) at 12.5psi on the half bridge engine required a Ve of 120%. EMAP would be around 30psi and inlet air temp around 110F . Both of those things are hugely detrimental to good Ve , especially when there is big overlap present. Is this realistic ? A Ve improvement of 26% ................ I don't think so .
I think what we have here is one of those results that you see every now and then where all the stars were in alignment . A small Ve gain from porting , an optimistic dyno a pessimistic boost gauge and a big dose of overenthusiastic optimism.
09-08-2020, 02:33 PM
