I didn't see that as getting personal ... just stating reality of the situation.
As for why I think it works that way ............. because with this twin scroll design, whatever flow comes out of the left hand port is a set amount. It is possible for higher internal pressure in the chamber to send more flow out the Siamese side but given the restrictive nature of that port ....it's not really going to do that much.

So if you accept this you realise that, if the flow from the left port isn't EXACTLY half of what is required to power the turbine, there will be a backpressure imbalance. If the right side has high backpressure the way to redress this imbalance is to decrease the flow through the turbine and increase wastegating. I did this by fitting a smaller AR turbine hsg. and got the result expected.

 

Quote :"That lower flow in the long path is now resulting in less restriction getting there as a result. That’s the backpressure difference you noted."

I have to admit that I originally thought the high backpressure was for the same reason you stated above. Well, mostly the tight radius 90 degree turn but a little of what you said as well. Luckily I've been there before and was able to look past that and realise that was only a minor part of it.
I explained the major issue in the previous post but you didn't seem to get it . From what you are saying about flow paths , it sounds like you haven't figured out what flow is going where . There are no long flow paths.

There is no Mr Angry ...not sure where you got that notion?

 

I'm trying to get my head around how that is working. With both center ports and the front port going into the one scroll with the Wastegate. And the rear port going into the other scroll, I'm trying to figure out how the flow will go.
With the gate closed the rear rotor will dump into both... so about 2/3 into turbo and 1/3 into other scroll. The front rotor will be dumping 3/3 into front scroll with 1/3 from the rear rotor. The back pressure will likely force more into the rear port and increase flow through that port into the turbo... but what is it going to do with heat at the siamese port if it isn't flowing out like normal. When does the gate tend to open?

With the gate open there will be increasing flow out the wastegate and less flow into the front scroll.... but where does the balance point occur where things even out?

I guess without a wastegate position sensor and EMAP in both scrolls it will be an unknown.

 

Yeah ...sounds like you nailed it. Around 65-70% of the total goes into front scroll except when the WG opens and then it's roughly even between front/rear scrolls and wastegate. That aspect of it definitely isn't perfect and I've had to make a compromise to try even the flow distribution out by fitting a smaller AR hsg. It's certainly not something I'd attempt to sell in this form as it does require a balancing act where even the flow of the rest of the system will also affect the outcome.

However , for me, I kinda like playing with that kinda thing and like the idea that by getting it right I end up with the broadest power band possible. Maybe .................the broadest ever seen on a Renesis
If anyone else were to attempt it I'd be recommending a single scroll turbine housing for sure.

As far as the Siamese goes ..... I think it will end up flowing less than normal as it doesn't have a very good exit into the log , but I'm not concerned with that one bit as the sleeve is a weak point so less flow will have a positive effect on its longevity.. The Main focus is to get really good flow through both outer ports . AT peak rpm/flow, where it matters, this design does that better than anything else ...IMO

 

Side note on the Siamese sleeve :
Most don't realise how much air actually goes through it ! Based on my experience and observations , I would put it at approx. 40% of the total flow of the engine. Looking at the restrictive design of it you would think that impossible , but I believe there is a venturi effect present that increases flow. As the velocity through it is so high there is certainly no possibility that air can ever backflow into the opposing chamber so that aspect isn't a concern for me.

And further to this :As with any venturi ,it will reach a point (quite quickly relative to the other port) where more flow is impossible. Another good reason to favor the outer ports vs the Siamese as this new design does.

 

Just wondering if you had considered a matching Siamese barrier in the manifold the center exhaust port so the rear center flow only combined with the rear side and the front center flow combined with the front center to the different scrolls. How might that affect the low end spool up? Initially I can see how that might cause problems with the waste gating since only the front rotor would flow to the wastegate when open.

 

There really isn't an easy way to do that and if it was possible I'd have to wastegate from both sides to avoid a massive imbalance. If I were building a new system from scratch , I think I'd get one of those new 'G' series Garretts and go single scroll. Those are supposed to spool up really well and make big power from a small package which is ideal for a low mount on the Renesis.

 

Had another run on my fav. windy road after the latest changes.
The faster spoolup has made it even better than it was. What I really like is the near instant onset of boost at mid range rpms . Hard to quantify but it really does improve the driving dynamics.

 

Something like this :

 

There were a few things I didn't like about the old manifold design ... the biggest being packaging . It was a very tight fit and it compromised on ground clearance. Aside from that it worked great . Made good power with good spoolup. Your criticism of it over flow restriction was not borne out by any measure that could be put on it and was basically............ wrong!

The reason I decided to build this new manifold was because I had an idea that I thought could be worthwhile. And when I get an idea like that it's like an itch that I have to scratch. Your assessment of this new design is roughly 80% wrong and only 20% right. I can only put this miscalculation down to your lack of experience. You sit at your keyboard with your big brain thinking you can evaluate it without the proper experience .... being an engineer I thought you would have learned this lesson years ago. I saw the design you proposed for your setup. It's a shame you never tried to build it because it may have given you some appreciation for what you are trying to school me on. It was very obvious to me that it actually couldn't be built the way you proposed so just as well you canned the idea.

 

Check out this for further relevant info on the above discussion :

https://www.rx8club.com/series-i-maj...1/#post4926639

 

Seeing as you don't listen to what I'm saying , perhaps a diagram might help you see it.



So comparing front scroll to rear 34/30= 1.13
That's 13% more flow through the front than the rear with the 1.06 vs roughly even with the 0.83.

 

Not overly worried about what's happening before the WG opens . My logs aren't showing anything too alarming.
I'm talking about peak power/rpm only , obviously the percentages do change as it goes up the rev range.

 

You did can it ... for the reason you just gave. Did you really want me to mention the big C as your reason for doing so?



It's only you that I give that attitude to ...no-one else. Consider that I detest bullies and people that put down others and ask yourself why that might be.....

 

Too much txt in your last reply for me to be bothered with but I will pick out that snippet.
I'd point out that I disagree with people all the time and am known to be quite argumentative just as I'm sure you are.
The difference I see is that I don't put people down when they know less than I do about something , I'll put my point of view forward but try to be respectful at the same time. As such I can count on one hand the number of times people have threatened me in my entire life .......

 

I feel that this was a bad RX8club "culture", maybe set by MM, that's really annoying. Its put more time and effort into mocking people, and insinuate own supremacy, than actually pointing them i the best direction. I believe it inhibits development, and is not good for anything except filling individuals ego.

 

Just have to say, I love how you do opposite of what "everyone"(including me) thought was the best direction, I'm impressed. Proving it right isn't going to be done in one night... I tap out how you came to think this is a good idea.

 

Thanks man - appreciate that . I NEVER would have even contemplated trying this if I hadn't learn't so much with the other (totally unconventional) manifold design. I kept looking at that design trying to work out how to get a more direct shot into the rear scroll. After lying on my back for hours staring at it ............ it finally came to me. Then even more hours spent trying to work out how to do the wastegate then a lightbulb moment on that as well. That plus the realisation that ...the siamese just needs somewhere to go ..... it really doesn't need a good exit path.
The result : the absolute simplest design you could possibly imagine.
It does seem to me that others are somewhat underwhelmed by it though. Perhaps I need to put it on the dyno and make 400 with it ....?

 

Nah, man. Not here. Big kudos on the product of many hours, $$, sweat, trials & errors.

It's simple, tight, ease of R&R. Well done. I've a kit that works pretty well ,...otherwise I'd be contracting you to fab one for me.


That'd be keen to see too.

 

Personally I'd really like to see the numbers at a pressure (relatively)safe to "slap on" a stock block on easy accessible fuel as well, then "forget it", trackdays or not. Is memory serving me right if I say 10psi/0.7Bar, 12psi is pushing your luck?

Another thing, it would be interesting to see the difference in boost pressure profile between 2nd and 4th or 5th gear, but a VD would suffice in this regards.

 

I moved on by deleting what I didn’t consider relative or not conveyed clearly

but will say the following and let it stand on it’s own regardless to any counter replies, everyone can decide for their self what they think is going on.

When backpressure is introduced, the impact on flow is not necessarily as perceived

Which due to phase timing of the two rotors, there is a period when the exhaust cycle between them overlaps with the siamese port being open on both rotors at the same time; as the exhaust cycle on one side is closing (lower pressure) the exhaust cycle on the other rotor is opening (higher pressure). What occurs in the NA configuration during this overlap period is not the same as when turbine backpressure is introduced.

I disagree with the flow percentages being estimated. It’s important to understand they are only estimated. It’s equally important to understand they’re not fixed values either, but will vary by engine rpm, the distribution of pressure as influenced by the manifold flow paths, the turbine A/R, the turbo impeller size configuration and so forth.

In particular, my perception of the comments is that the impact of A/R relative to the distribution of pressure and flow between the two turbine scrolls; which will be determined by the configuration of two divided paths of the manifold, and how it will affect those flow percentages is not being fully realized. Even though a net manifold pressure value may be detected and recorded, we can’t forget that the pressure of the combustion gasses from each rotor is essentially a pulse with it’s own variation of high to low pressure relative to the exhaust port open-close cycle.

The design is simple, but perhaps too simple. It’s my belief that keeping the three ports on separate flow paths is the way to go. One example of this is the RX8Performance turbo system manifold as JCB is using on his RX8. That design is based on an open V-band turbine though. The way to address it with a divided scroll is to accept that we can never fully separate and isolate the exhaust streams due to the shared siamese port. Be that as it may, I still believe keeping the three port flows separate with a dual scroll turbine housing has value. It’s how the middle siamese pipe is configured and joined at the divided turbine flange that will determine how well it works.
.

 

I'm currently running it at 12psi on pump gas and it's producing in the order of 360+ whp and 260lb/ft torque. However ....I wouldn't be confident holding it there over summer. Just from previous experience. I have nothing to suggest ,so far, that it's any better or worse than the previous setup in that regard though. Pretty sure 10psi would be very safe though and we'd see 330-340 whp. Can do some Vd logs if you like , or were you wanting to see dyno plots?
I can show you some boost profile logs I already have in 2nd and 3rd .... 4th is too fast for me to attempt.

 

And Team . I don't want to start another argument right now. I agree with some of the above and disagree with some of it as well.But we've already hashed most of it out.
What I would say is : Until you start trying this stuff yourself your mind will be closed to the realisation that things don't always work out the way you think they should.

 

Was just curious to see difference in turbo threshold, VD should give that answer pretty clear.

I think you'll get pressure earlier if you floor it in a high gear, compared to 2nd gear, since RPM isnt climbing as fast. For a dragrace that does not matter much, but say that we get pressure 3-500RPM earlier in 5th, it means it will feel even quicker for everyday driving and cruising. This difference is noticeable in my other car, but thats only 1.75l.

 

I get it B, not looking for agreement or discussion. It was only to try and restate my views clearly whether incorrect or not after getting rid of the previous comments. There’s no doubt your method works well.

Wish there was more to compare against it since there simply aren’t that many successful Renesis turbo configurations. JCB is about the only other lowmount even close. It’d be interesting to see what that system could do with a slightly smaller 6062 over the 6266 to hit that output and manifold pressure target.