:O learn something new everyday!

 

Yep me too !
pedanic = http://dictionary.reference.com/browse/pedantic.

 

I remeber coming across this video several weeks ago. It makes plenty of sense for a 4 port to reach those numbers like MM has mentioned. The only thing to do is for someone to be willing to put their 4 port to the test.....

 

Its not pedantic at all.
Turbos like the 307x increase in efficiency as you increase the Pr (up to a point).
It would rather move 400 g/sec at 21 PSIG than 14 PSIG.

 

thats what i keep telling people. someone that blows a motor, try out some diff apex seals maybe.. esmeril (maybe they are actually durable who knows). use a 3071r or a BNR turbo so you can eliminate the usual bottlenecks of that stock turbo. get new injectors. dyno a 12psi run and a 15-16 psi run.. Add meth injection and you will see that little motor make POWUH!! as some of ya'll say.

 

Yes , I know .

But , Take a 6 port and a 4 port , both with the 3071 ,at 7500 and 300whp .

The 6 port will be at 9psi (ish)

The 4 port will be at maybe 12 psi (guess)

So how do we get 12psi on the 4port ?
We close off the wastegate some more via boost controller (or mechanically) .

Sure the turbo may be in a more efficient part of its range but we have created more backpressure to do it ..............

 

Not quite.
As the Pr increases that slight amount, the efficiency of the compressor goes up, so the need for additional turbine pressure is almost completely negated.
This is the art of turbo selection.

 

/\ by that logic we would be better off without the aux ports . Why don't you just block yours off and see how you get on ?

 

Been there, done that. That's the GReddy trick, remember?

With the GT3071, there is no noticeable difference in power with the APV closed or open. In fact, I've moved the opening point on my setup up to 8200 RPM just to get it out of the way of the knock ranges and as a trick to lean out the upper fuel map.
That does get rid of the little "bump" that happens when it opens at its normal 6250. I don't open the VDI at all.

 

Yes I remember the Greddy trick well . I did a lot of testing on that very thing.
When I did it I found power dropped away significantly above 7000ish . To get that back you would need to dial in more boost (IE close off the wastgate ) which was the whole point of my argument earlier .

 

And the net flow through the system was?
I think you may still be missing the point - You are still equating boost with flow.

"Backpressure" is not a real value. Net flow negates "backpressure".
Look at it this way - what would be your net flow with no "backpressure"? How about with infinite "backpressure"?

 

Was it not you who once said the best system you could design would have zero boost pressure at maximum flow ?

 

I personally would like to try for 300whp, after which I will be satisfied and will most likely not try for more. While I would like to try for that 300whp my two trusted advisers, Jeff and Ray have to agree that I have a reasonable chance and that my car is setup for the challenge. I have relaxed this winter and not really pushed for more HP.

 

do you have the larger pullies from pettit?

 

Phil you avatar is 2 years out of date. You are using the 8" pulley, correct?

 

Yes I have the larger pulley from Pettit........Ray and I were working on a special pulley that may help.

Avatar is changed....................Yes I am using the largest pulley that Pettit offers. If Ray wants to climb in here and explain the "special pulley" it would be nice since it's his design.

 

So had the Renesis been FI while being developed, all the way to pos, do you think those valves would've been there still? I've always thought they were mainly good for N/A, based on how the intake pressurizes air. Seems like from the beginning they knew what they were going to do. Which in part scares me about the mixed info we've been getting about the 16X. I would like to see a rotary turbo from the factory. If not turbo at least 350hp.

 

They saw the problems from the FD, which was quite largely in their design with the turbo system *miles of vac lines couldn't EVER be a good idea.*, along with the heating issues....they decided to push as much out of the engine NA as possible. And the fact they got this high is quite an amazing feat *feet?*, I'd say.

I'd rather have a nicely tuned and RELIABLE NA car before a Turbo.

 

In a given system boost and flow are very closely linked -almost a linear relationship until the turbo drops out of its range and backpressure starts to build exponentially.
So boost IS relevant as a variable . Until you change something in your system of course .

Yet any good textbook on the subject will point out the negative effects of having too much backpressure as a proportion of boost pressure . Even if flow is increased there is a point where too much backpressure is a concern .


BTW . It was me who suggested to people it was a good idea to fit the Greddy blocking plate and you who initially advised people not to .
There's some irony for ya !
Thread on it here:
https://www.rx8club.com/series-i-major-horsepower-upgrades-93/greddy-turbo-owners-make-sure-you-fit-your-blocking-plate-164382/

 

you have a good point. and they got damn close to the same stock performance of the rx7 with no turbo

 

You are still not looking at what is causing the net decrease in flow.

 

OK - I'm with you now .

The decrease in flow is caused because the wastegate actuator is designed to adjust pressure . Reduce the flow capabilities of the motor and the wastgate still provides the same pressure - but flow is reduced .
So not opening the Aux. port means flow is reduced - pressure stays the same . Tweak the wastegate arm (or boost controller) to bring up the pressure and get back to the flow you had originally but at a more efficient Pr.

However I still think you will have more backpressure at the wastgate roughly in relation to the increase in pressure on the compressor side ...

All this has reinforced something else to me - making power is more about the turbo than the engine .

I'm switching to a four port setup as from now .

BTW - I think was on the right track when I started the blocking plate thread , I just got lost in trying to make too much power with too small a turbo .....