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All those things have an impact for sure . But It's not till you compare what the renesis exhaust is doing vs a PP exhaust that the huge disparity becomes obvious. At this point I believe the theory holds . And any attempts to make 400plus would benefit from bearing it in mind.
I agree with the exhaust port disparity. Not mentioned that I see, is how the exhaust port tapers off toward the closing point. IMO it actually closes sooner than you proposed because once the rotor face gets to that point (the carbon build-up shelf), which is well before the rotor passes the actual port end, the flow is more or less already cut off to a negligible value. What really makes the difference imo is that the RX7 exhaust port can be seriously modified wrt both flow and timing, which the Renesis exhaust is extremely limited to do much other than open it earlier. Even that is a minimal improvement, but would work towards relieving the excessive dynamic pressure issue.
However zero overlap with high compression rotors already results in a high dynamic operating pressure, particularly at high rpm, which is one of the reasons an NA Renesis excels without any fancy exhaust tuning magic. A turbo will exacerbate that for sure without some other way to compensate for it. It’s a shame that they didn’t invest in a wider center housing and appropriate e-shaft etc. rather than the seriously compromised siamese port arrangement. It probably would have made more sense to have instead done a partial/small exhaust p-port there instead, along with a full depth apex seal. Which seems to be the direction they took with the more recent patents that were filed several years ago.
I agree with the exhaust port disparity. Not mentioned that I see, is how the exhaust port tapers off toward the closing point. IMO it actually closes sooner than you proposed because once the rotor face gets to that point (the carbon build-up shelf), which is well before the rotor passes the actual port end, the flow is more or less already cut off to a negligible value.
Yeah , but there is still some open port on the side after the "carbon build up shelf" is sealed off and the scallop on the side of the rotor does a little to keep that area flowing as long as possible . But it's still very small and there is still plenty of exhaust gas to expel at that point. It has no chance at elevated mass flow rates.
Running a large turbine must help somewhat , but even with zero backpressure in the manifold (aka supercharger) I believe the issue will still arise .
Sorry for a late bump (again). I watched a video on HPA about a twinscroll flange that had a wastegate hooked upto one side of the scroll. This was to increase the response time at much lower rpm. As RPM increased, the wastegate opened up, free'd up the exhaust, and made full use of the twin scroll. Another wastegate was used to divert exhaust gases to regulate boost.
Brett, For the price of another ruined housing, you could probably get MnM racing or HPR to Peripheral port an exhaust in your housings + make an evenly split 5 into 2 exhaust manifold, and using the method above could still help with your turbo response.
The idea overlooks the effect of what splitting the exhaust into multiple streams results in. Instead of wasting time and resources on boil and bubble, swapping in an REW will outperform such an engine without such toil or trouble.
You could do the exact same idea on an REW even, but it be a lot easier and cheaper to implement than a 5-port nightmare.
Might be a worthwhile idea to try in that alternate case, just that all this Renesis hybrid stuff has never panned out to mean much. More than a few have been built, never to be heard from or seen again. That tends not to bode well because there’s always a bunch of projected conjecture leading up to the build about how great the results are going to be. Even the one turbo deal a few years back involving one particular aftermarket company turned out a bit ho-hum. They could have achieved those numbers easily on an REW imo. So why bother?
I think bridging the exhaust ports would resolve your issues.
Initially Mazda moved the exhaust port further away from the seal (towards the centre) due to heat causing water seal failure but they kept the port the same size; Increased exhaust flow (through porting or increasing the exhaust size) lowers the exhaust temps, so bridging might actually make it more reliable?
I realize there probably isn't any templates, just a thought.
I think bridging the exhaust ports would resolve your issues.
Initially Mazda moved the exhaust port further away from the seal (towards the centre) due to heat causing water seal failure but they kept the port the same size; Increased exhaust flow (through porting or increasing the exhaust size) lowers the exhaust temps, so bridging might actually make it more reliable?
I realize there probably isn't any templates, just a thought.
Yes ...that's a good idea . But if you get hold of an iron you will see there is no way to do it without going straight through the water gallery. Then if you weld up the gallery to enable it, you would remove cooling where it's needed and overheat the port surround.
I actually did try something once along those lines , but it did nothing . The hole was too small to be effective. Plus it created other issues as mentioned.
So this is being plastered all over the net atm so may as well address it before I get called out:
So yeah , this setup made 550whp at 30 psi which obviously exceeds my theoretical max. , by a wide margin. Obviously my theory was flawed ...not entirely wrong IMO, but certainly wrong in the sense of what maximum horsepower can be achieved.
As far as what this does prove , is that you can obviously make more power than 450whp ....................but you certainly can't do it with any kind efficiency. At that boost pressure you could expect at least another 100whp if the engine was running efficiently. The fact that it didn't blow up I would put down to three things : high octane fuel (E85) , a monster turbo (1600 piston hp capable) and the fact that even though the pressure at the end of the exhaust stroke is going to be really high(which reduces efficiency) ..... the total volume that can be carried over is still relatively small in relation to the expanded volume.
As can be seen from the dyno .... there is really no useable power band so far (less than 1000rpm) . Hopefully they can do better in future sessions.
as we discussed before, there’s no reality between that and a practical turbo setup.
If you watched the video they still have a lot of tuning work ahead of them. Those FD rotors without cutoff seal addition have to be bleeding a lot of exhaust gases back into the intake. Which alcohol fuel is going to be more tolerant of, but it still impacts performance potential as you noted.
the hybrid comment is noteworthy; they found out the hard way ...
otherwise when Elliott starts opining projections, I need to take out my barrel of salt
.
It'll be interesting to see if the motor stays together, because it looks like it only made 550 wheel for about a half second. Does anyone have the full dyno sheet where we can see RPMs?
I'm rooting for this guy, but I'm a bit skeptical on the longevity of this motor as its a lotta air to push through those exhaust ports. Either way, I hope this is pushed until failure so we can learn the absolute maximum potential.
Wow.... I can't imagine what its like to drive. Lag lag lag lag and roasted tires.
I'm not saying it isn't a small powerband, but it's worth mentioning he has tall gearing as this car is built to be a top speed car. His goal is 250mph so although his power band seems small he isn't ripping through the RPM range at as fast of rate as a stock setup and it is being built with one goal in mind.
I'm not saying it isn't a small powerband, but it's worth mentioning he has tall gearing as this car is built to be a top speed car. His goal is 250mph so although his power band seems small he isn't ripping through the RPM range at as fast of rate as a stock setup and it is being built with one goal in mind.
You still need to get to the power band somehow ...... with less than 1000 rpm to work with you just can't get to that sweet spot after each gear change without an ultra close ratio gearbox and dozens of gears.
They are going to try Nos next to spool up the turbo sooner .......... but when I put the numbers on the Garrett compressor map .... it looks like it's already operating on the surge line (meaning there actually isn't anyway to flow more air at that boost level and lower rpms). Will be interesting to see if they can get enough improvement to make a worthwhile power band. I wouldn't be putting any money on that notion myself.
You still need to get to the power band somehow ...... with less than 1000 rpm to work with you just can't get to that sweet spot after each gear change without an ultra close ratio gearbox and dozens of gears.
They are going to try Nos next to spool up the turbo sooner .......... but when I put the numbers on the Garrett compressor map .... it looks like it's already operating on the surge line (meaning there actually isn't anyway to flow more air at that boost level and lower rpms). Will be interesting to see if they can get enough improvement to make a worthwhile power band. I wouldn't be putting any money on that notion myself.
For sure, all I was getting at is that once in that power band he will be hanging out there longer than a typical Rx8 setup. Hopefully they can broaden it and keep upping their numbers, sounds like they still have a long ways to go, it will be interesting to follow nonetheless.
To go 250mph, how many seconds of WOT are required 30, 40, 50????? Yikes
From what I could see from the dyno ...they were having to coax it up the rev range extremely slowly without going wot till the very end . Possibly due to surge problems with the compressor
01-21-2020, 09:05 PM
That's some petty, baiting BS right there. 
