6-port turbo...can someone give me a torque lesson?
 

alrighty...
i'm gonna try building a 6 port turbo engine. s5 front and rears with t2 rotor housings, 3rd gen rotors with 3mm seals (just cuz they're already machined or i wouldn't bother). this is gonna be powered by a pair of td05's with clipped turbines--non sequential to start, then hopefully i'll find someone to build a manifold to run them sequentially.

here's what i'm going for.. torque--or at least as much as i can get from a rotary.
should i use the smaller primaries from the n/a, or use a t2 intermediate? other than cleaning up the runners, port timing on the primary and secondary ports will be stock... the 5th and 6th ports will get severely gouged...

so instead of going for 500 hp with 300 lb tq, i wanna try to get it balanced---like 400/400 or whatever... so who knows how to build torque?

let's put it this way... who has the most torque and how did you get it?

my take is that this will probably have more to do with balancing port work and turbo choice rather than just using the 6-port

any input will help...

mild streetport (particularly the primaries)
higher-than-stock-turbo compression (suggestion: choose the 9.4:1 instead of the 9.7:1 rotors)
oil and cooling mods
choose a smaller turbo (maybe a T3/T4 hybrid or something) - i'm not familiar with the size of a TD-05
good EMS and appropriate tuning
and ...
the discipline to know that you're not going to go chasing HP numbers later on with a setup you set up for torque

that's probably what i would do ....

as stated in the original post:
3rd gen rotors,
twin turbo.
stock primary and secondary port timing
all the other mods go without saying...

thanks for the input, but can you please read the post next time?

i read the post. i saw your plan and i made suggestions of things i'd change based on your goal of torque. really simple. if you're hell-bent on using that setup and not changing anything to suit your request, then you need to rephrase the question because it's not a question of building it (which is what you asked), it's a question of tuning it.
don't need this ... good luck with whatever you choose. hope someone can help.

If you want TORQUE, then you don't want a turbo, you want a supercharger.

Most turbo's only start working at around 2Krpm - you can use smaller ones in multiples, but that means more space needed, and more underbonnet heat. Superchargers will work even at idle if you want them to

As said before MILD porting is the key to keep torque, all you need ot do is slightly increase the ports to allow the supercharger/turbo to force in more air more efficiently

actually, i think a turbo will make the best torque....the sc just puts it down low.

i was under the inpression that the best torque is made from not shoving more air in, but keeping the velocity high--so stock port timing on the primary and secondaries... the auxilliary ports are the ones i'll gouge out for the top end power--since they won't be opened until the upper rpm range anyway.

diabolica...i didn't meanto piss you off dood.

you said use a smaller turbo like a t3/t4....the tdo5 is quite a bit smaller than that, so you contradicted yourself.

i can't use the higher compression rotors and make my power goal on pump gas--not safely anyway.

anyway, sorry for pissing you off... i just felt that the suggestions you made didn't really relate to the question i asked. my apologies

But what's the use of having torque if it's up high in the rev-range? To be of any use (read: to beat V8s) it HAS to start low in the rev-range. Plus it will make it much more driveable if it's available from idle

sequential twins should put it down low enough..

that's the idea behind the stock pri. and sec. ports....keep the velocity high to build the low end power. the aux ports probably won't get opened until AFTER peak torque....but that's only a guess right now.. i won't know for sure until after i tune it

You probably want something that spools quickly, like a TD-05 or a GT28. IMO, high-rpm boost is going to be pretty much useless once your auxiliary ports open. The opening of the tertiary ports is going to lengthen the duration of the intake stroke. Turbocharged rotaries do not like this. They want the ports to close as soon as possible to avoid compression problems.

[QUOTE=badfish229] IMO, high-rpm boost is going to be pretty much useless once your auxiliary ports open. QUOTE]

can you explain this a little better? i was under the impression that a longer duration would build top end power... all the streetports i've done seem to peak higher than their stock port counterparts (all other things being equal)

From what I have heard, port overlap is excellent for making high-rpm power. Having zero port overlap would limit how much boost, therefore power you will be able to create. You might be able to open the auxiliary ports at full-boost to maximize power. Us RX-8 owners face a similar problem.

I believe with lapped ports, low-rpm power, as well as driveability, is sacrificed for high-rpm power. This can be good for a race car, but, for a street car, this could be an issue, especially for those of us who want a street/track car.

I am not against lapping ports, however :).

why would less overlap limit the amount of boost you are able to create???

guys are making 400ish to the whels on stock ports, so i'm sure that goal won't be incredibly hard to reach. i want to keep the overlap low to preserve the low end power, but extend the duration of the auxilliary ports to enhance the top end power...

i think i may end up using an n/a intermediate--moderately ported, but without the early opening. i think the 3rd gen ports have less overlap, but i don't think i could use that intermediate unless i got really REALLY creative with mounting the engine.

maybe 360-370 hp/tq would be a bit more realistic for a power goal.. i could always tear it back down and try something else if it doesn't work out the way i want.

As I stated earlier, it is not advisable to leave the ports open for too long. This could create reversion at low engine speed. Too much reversion may lead to a failed emissions test. And, I'm sure us rotary owners could use a break ;).

Port overlap is like camshaft overlap. Piston engines that have overlapping characteristics have terrible idle and low-speed driveability. I remember a kid in high school who owned a 600 hp Cobra. You could tell that this engine had a high-performance cam. This is an extreme case, as the car easily died in idle. Rotary engines can experience this as well with too much port overlap. I believe the problem lies in the valves/ports being open for too long. My theory is that the intake velocity is slowed with a larger port. Having a slow intake velocity may make it difficult for good combustion; velocity is directly proportional to the mass flow rate. This may explain the difficulty associated with low-rpm use; the low intake velocity leads to low vacuum, which leads to difficult combustion.

Port overlap, however, is not a bad thing. With more overlap, you could turn up the boost. This leads to excellent high-rpm power. For some, this can be a good thing. This is a main reason why peripheral ports are so great for making insane power. With p-ports, you could have as much port area as you want. Side ports on the other hand, are limited by the coolant jackets and side seals. You can street, bridge or monster port a rotary, but you are still going to be limited by those two parameters.

Keeping port overlap to a minimum can save on street-ability. Also, I believe I mentioned that you could open the auxiliary ports at full-boost. Perhaps that method could be used to create the maximum power. IMO, the point is to keep port timing to a minimum for usable street power. But, if you feel like turning up the boost, perhaps more port overlap may be due.

I wonder if it is possible to create at least 1000 rwhp with zero port overlap.

cool, but like i said--i'm not advancing the intake timing, i'm only extending it. reversion isn't caused from the port being open too long, it's more of a port-overlap, backpressure thing.
since the port timing won't be advanced, the extended duration will provide CLEAN air, and may actually reduce reversion, while at the same time, giving more top end power.

think of it as having just a little bit of the characteristics of a miller cycle engine--just not as drastic.

Damn. I haven't heard anyone mention the Miller Cycle in a long time :).

Is there a relation between reversion, overlap and backpressure?

yea,
early opening on the intake=overlap=more reversion
backpressure =more reversion

in terms of the miller cycle, i most likely won't open the port all the way into the compression stroke--that was more of a reference as to where the port duration would come from...late closing, rather than early opening.