Brettus

iTrader: (2)

Would like to see that dyno if you have it ?

JETS3T8

I’ll have to go through the screenshots of the pulls and match it up to the logs, won’t be soon but I’ll try to get to it.

With or without the dyno chart though these logs clearly show that my setup doesn’t suffer from high emap issues like yours does. Regardless if it’s at 7700 or 9000+, making power or not, the hot-side needs to be addressed and approached much differently on side port exhaust motors.

What you’re trying to accomplish by trying to build a responsive turbo street/strip setup with a broad power band is almost definitely going to require operating at a minimum of 1 to 2 imap/emap back pressure ratio or more. HP Academy has a great write up about emap and mentions how oem’s are able to achieve such amazing low to mid power and response by running at insane imap/emap ratios. But the backpressure and egt’s at those ratios is really tuff on a motor. Piston motors and pp exhaust rotaries can better withstand these conditions but the renesis can’t due to the exposed side/corner seals.

Reducing back pressure to close to or less than 1 to 1 with a larger a/r housing and running an open exhaust are a few ways that “might help” get any sort of long term reliability from setups over 400+WHP...yes at the expense of responsiveness, a broad power band and limited application but that’s price you gotta pay for power & reliability from an MSP...imo

If anyone can figure out how to achieve a reliable high HP, responsive setup with a broad power band it’s definitely you or Team. Or at least get as close as possible to it.

Good luck.

Brettus

iTrader: (2)

Emap/imap going down at high rpm just doesn't make any sense to me (big turbo or not) ...unless power (and mass airflow) was dropping away badly. Possibly the only counter to that might be the compressor moving into a much more efficient part of its map.

TeamRX8

iTrader: (25)

That’s what I was attempting to explain earlier. I’m sorry if it came across the wrong way. My only intention was to express a difference of technical opinion and explain the why of it. Which I’m not always the best at choosing my words or reigning in expressing them.

However, as per other recent discussions elsewhere, the new Garrett with it’s higher compressor efficiency is going to help if you can keep the engine there wrt flow/pressure. Otherwise running far out to the right of the map with comp efficiency dropping and emap increasing as in many previous turbos, then the two together are going to work against the desired result.

My observation is there’s a lack of understanding among some people about VE in general, and relative to the Renesis in particular. Regarding the Renesis; when the SSV opens the secondary ports; there’s a VE change. Then another VE change when the APV ports open. Then another VE change when the VDI opens on an NA engine, but not on a turbo engine because any chance for a resonant effect from it is cancelled by intake pressurization. There are other things going on that make for good VE on an NA engine that either aren’t necessary or can even inhibit VE on a turbo engine. To the point above on the dropping emap, that’s a big turbo and was likely operating on the far left side of the compressor efficiency zone, but progressing toward it would be my hypothesis too.

There are changes on the Landspeed engine relative to that. I might try to tackling it a bit different that was done here, but in that regard everything is massive enough that it’s likely moot. Back in another thread (Mazdatrix hybrid maybe) where I was posting up results from other engine/turbo combinations to demonstrate a point about boost level vs output, people clearly didn’t understand the results any more than why they were what they were. As was posted then, it’s not just misunderstood here, but also not understood well over on the other forum too. Even the aftermarket more or less duplicates what was and still is rather than considers why that may not be necessary now.

I apologize for being cryptic about it, but in time prefer to prove it in action rather than theorize it clearly beforehand. When I started the 4-port thread, this understanding or number of other things that have been posted in the last 6 - 12 months didn’t exist. It’s been evolving over time, and more so recently. There’s no genius or superiority involved, just the natural evolution of learn, grow, and build upon that to reach higher still.

all imho ...
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JETS3T8

Yep. It has everything to do with efficiency. Both the compressor and turbine moving into higher or more optimal efficiency. And to a lesser degree but also a contributing factor is the benefit of the larger wheel’s inertia at higher rpm.

With GTX4294R emap never exceeds imap, it reaches 1 to 1 between 4700rpm to 5100 then imap/emap ratio drops below 1 to 1. No power loss.

On the GTX5533R, from 3000rpm to 5200rpm imap/emap ranges from 1 to 4 to 1 to 1, then from 7000rpm and up it goes below 1 to 1.
Efficiency, inertia & rpm 👍

I don’t expect anyone to take my word for it, just refer back to the dyno charts I already posted.
From approx 7K to 7.4K there’s an increase of 75-100whp where emap is below 1 to 1.

And don’t get so caught up with “below 1 to 1”, the point and focus should be to get as close 1 to 1 for power, longevity and reliability with the MSP.
Period.

Brettus

iTrader: (2)

Ok, well maybe I spoke too soon an this thing will do as you say . If so it may open our eyes to some new possibilities for this engine.

Brettus

iTrader: (2)

Interested to know if you put the scalloped rotors in for these latest dyno runs?

JETS3T8

Nope. The rotors in there now are the same as the ones posted on IG. No scallops.

TeamRX8

iTrader: (25)

https://www.rx7club.com/old-school-o.../#post12452407

strokercharged95gt

Wow

TeamRX8

iTrader: (25)

.

Brettus

iTrader: (2)

In that case ....after some head scratching and revisiting your old posts re the cutoff seal omission.....I'm thinking that small detail (in combination with the EMAP/IMAP being less than 1) is having more of a positive effect than I initially imagined!



Given that, in my latest endevours with the G30-660, I still hit 'the wall' as far as maximum power goes we still need a solution to that....... what you are doing may well be a work around and well suited to your particular goals but not really a practical solution to the the issues I raise in the '450' thread.

Perhaps the scallops (on exhaust side only) would be more practical as a solution ...................

TeamRX8

iTrader: (25)

Not saying it won’t have any effect, but it’s not the reason the wall is being hit. Perhaps go back and review the recent series of comments again. Or at least it seems that maybe you possibly either forgot them or perhaps didn’t fully digest them.

Understanding that he has mostly stock intake and exhaust ports (street ported; close to stock, but not modified much) without scalloping, though lower compression 13B rotors. What else is different then? Dare I suggest that some of it is “the same thing” as per the other thread, though there are other substantial differences as well given the particular goal.
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Brettus

iTrader: (2)

Team
That's your opinion based on your armchair observations. That's all it is ..your opinion .
When you have some results of your own (or can show other credible evidence) ................I'll start believing you.

Obviously there are several factors in play here, that you don't see in a normal Renesis, that contribute to the results we are seeing.
My opinion on what's happening :
1/Low compression rotors .... this obviously helps with detonation resistance but it's only having a relatively small effect on peak power.
2/EMAP/IMAP less than 1 .........this is having a major effect on power generated but on it's own would still not yield the result we have seen.
3/Ethanol/Methanol injection ..........obviously a major benefit both with detonation resistance and power generation.
4/Removed cutoff seal creating overlap.............The final piece in the puzzle which I believe (when combined with 2) is another major benefit to peak power due to evacuation of spent exhaust gas at top dead center.
I spent some time this morning with a rotor,side plate and housing trying to figure out how this was working. It took me some time but I did eventually see it ... took me totally by surprise!!!

TeamRX8

iTrader: (25)

the same armchair opinion you threw out in those comments that Richie then agreed with?

that’s just an excuse; we both know it’s you and your refusal to accept anything and everything from me. Of all the charity that has shared with the RX8 brothers here over the years, only one has ever refused; multiple times. You’ll never accept anything from me until you change what’s within your own heart. Saying otherwise is not truthful.

To exercise my armchair further; for this particular application I don’t believe the gas seal as so important due to grasping the results with a better understanding of the goal. I think the things you shrugged off above are important. If what you say is true, then removing those seals from your own engine should be easy enough, right? Based on my recent discussions with Pettit Racing about their REW rotors modified with a custom gas seal, I would not recommend doing it. Just the same, best wishes for a positive result to prove Mr Armchair wrong if you decide to pursue it.

Brettus

iTrader: (2)

I'm just throwing my opinion out there ...same as you are doing. I just make the armchair comment because ............... AFAIK that's reality.

Agreed

If you had read what I said above (post no. 562) you would already know that I wouldn't be prepared to remove the cutoff seals.

TeamRX8

iTrader: (25)

perhaps, I’ll study it more when I’m not half asleep

Brettus

iTrader: (2)

Whoever came up with the idea of removing the seal to create overlap deserves some credit IMO. The way that is working (I think) is like nothing we have ever seen before - very clever idea.

TeamRX8

iTrader: (25)

we discussed that when the thread restarted and what you stated above was never claimed. Without putting in a set of same having the seals and seeing the result I question whether it can stated like that as a fact beyond question. Understand that it leaks everywhere in the full combustion cycle as opposed to true overlap occurring only at the transition between exhaust and intake. Where is the highest pressure point and what happens then? Well that would occur at the early part of it being ignited, but where it goes ...

so it’s leaking everywhere all the time and what is the true low pressure point? According to Pettit, it goes into the oil and sump ...

Brettus

iTrader: (2)

No def. wasn't trying to state it as fact ...... Just an opinion.
But as you know ... overlap and low EMAP can create some interesting results so it's certainly not beyond the realms of possibility.

Whether it goes into the sump or back into the exhaust doesn't change the fact that : when the groove is adjacent to the intake port as it opens, it has a pressure lower than the intake pressure. And that means : exhaust laden air from chamber at higher pressure is likely to track around and fill the groove.

TeamRX8

iTrader: (25)

is it that, or an “armchair opinion for me, but not for thee” viewpoint attempting to justify a proposed theory that now seems to be in question? After all, it’s not like you have any direct experience/data with lower compression 13B rotors both with and without the gas seal.

It reminds of a story about a kid trying to justify why he needs a Red Ryder BB gun for Christmas; if you’re not careful, you might shoot your minds-eye out.
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Brettus

iTrader: (2)

Oh boy .............

Jose Zuma

So, to summarize this, the theory behind those power levels are:

• Low eMap.
• Removing cutoff seal .
• Good fuel

So, running the FD rotors is not worth after all? (except from the low comp point of view).

Brettus

iTrader: (2)

IMO
Yes... it's definitely well worth it , I probably understated the benefit above - my apologies for that.

Jose Zuma

Knowing this, let's put things together....

Sideports with all the stuff mentioned in this thread seems to point us to higher whp. Now, my question would be, will peripheral exhaust port add some extra bonus here?
IMO turbo should spool better plus possibly increasing the lifespan of the side seals?