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The pulses from the two rotors should still exist.
Afaik NO!
If you combine 2 rotors or more than 4 cylinders the pulses will delete each other.
They have to be seperate for I think 240° of crank angle at least to remain.
I made for my 8374 a very short manifold which is only possible with IWG, so pulses are super strong
And this is boost curve in 1st gear, boost builds from 2500rpm
Last edited by PatrickT; 01-23-19 at 02:55 AM.
Reason: added pcs
If you were to make something like a large 3 port orbital spool valve (think of a 3 inch by 3 inch cylinder with an offset port cut the shape of a steam pipe bend through it, just need to ensure it is alway open from exhaust port to one or both sides as it transitions) you could have something that presented a pretty much standard pipe section in divided mode and could join the two rotors cleanly at low rpm while adding almost no additional manifold volume that sat in/on the manifold side/between manifold and any split pulse turbo rather than the nasty poppet valve of a conventional wastegate. I was considering drawing something up myself (if i can't find something suitable in an industrial process valve catalog) as a test just with a split pulse 35R before moving to a 9280 later on.
Has anyone ever tried one of these. I haven't gotten to the point of actually looking at a specific turbo and comparing to an EFR or spoil valve, but reading about how it works.
Mostly diesel truck applications. So maybe this is only sized to be beneficial for much higher than street FD boost levels (Typically less than 18ish psi).
Yes, the diesel VGTs have been used on a couple rotaries- you can find some on youtube.
Some issues.
1)
Spool on a rotary is largely defined by the compressor wheels surge line because there is so much exhaust energy available.
Example, EFR 8374 with standard fixed exhaust geometry can already surge the compressor from spooling up too fast.
So, there has been great response (how fast the turbo spins up and max boost per rpm available is achieved), but little improvement in spool (how much max boost/torque is available at any rpm).
2)
Variable geometry exhaust means variable exhaust manifold pressure for any set rpm and exhaust manifold pressure affects the high overlap rotary engine Volumetric Efficiency greatly.
That means, it is really impossible with a full VGT turbo to correctly map the ECU to what the engine needs for fuel and spark without some additional inputs.
Exhaust manifold pressure compensation could be used like in the native diesel application.
Using Air Flow Meter input in addition to MAP input could be used instead or in addition to EMP sensor.
However, with the on/off of the "quick spool valve" style VGT you are fine with traditional ECU inputs/mapping as long as you have a set rpm the on/off transition occurs at.
3)
These stock diesel VGT turbos are small internally and huge externally. They are only ~400rwhp turbos on a rotary and too big externally to be used as twins.
4)
They use VGT as the crutch to spool and so don't use other technology like Gamma Ti exhaust wheels or even ball bearing centers.
An EFR 7670 without VGT will put them to shame in a much more simple package.
Turblown-
What is the smallest exhaust wheel you are planning that these housings can be machined to?
Can you divulge what the single and combined A/Rs are you are shooting for on this exhaust housing?
Ironically, because of compressor surge limits and Gamma Ti exhaust wheel max RPMs I think this design will work best on the smaller EFR turbos or if designed for large single A/R (like 1.00) and huge combined A/R (like 2.0) to accentuate high rpm power instead of trying to accentuate low rpm power with regular 1.00 A/R combined and half that for the single scroll A/R.
Unless the goal is just transient response where the gate is closed down to one scroll in vacuum and opens as boost comes in. In that way it should work great on the bigger turbos to improve driveability even more.
Unless you are pushing methanol boost levels or running a big full PP drag car I don't think many people are likely to approach critical speed on the 80mm turbine if using the new 74mm inducer compressor (9280). I think that will be the best implementation of the quick spool, hopefully be similar or slightly better to build boost than a conventionally set up 9180 with significantly more headroom.
You are right about the max RPMs for the 80mm Gamma Ti exhaust wheel.
What I was thinking is we know the 80mm Gamma Ti exhaust wheels are too fragile to exceed BW recommended RPM by pairing with a smaller compressor.
This fragility may also show itself when subjected to the harmonics produced by too high a rate of acceleration up to the max recommended RPMs. I don't think the ball bearing cartridge is as good at damping the harmonics as the standard bearings in the usual VGT turbos.
Imagine the 9280 with this Turblown VGT exhaust housing sporting a 1.00 A/R primary position and 2.00 A/R secondary position- that would help a semi p-port rotary push the compressor closer to its limits!
I don't think rate of acceleration will have a significant impact if people have been using ignition cut rev limiters and antilag already in terms of impulse or imparting vibration to the totaring assembly. It's just radial/hoop stress due to inertia at speed, lower exhaust temp will have a marginal impact.
I would guess Elliot is aiming at something like 0.7 area to radius of each volute so it comes out close to the largest factory housing?
Imagine the 9280 with this Turblown VGT exhaust housing sporting a 1.00 A/R primary position and 2.00 A/R secondary position- that would help a semi p-port rotary push the compressor closer to its limits!
I actually had a functioning (sort of) VGT setup on a 13B 5 years ago using a Holset HE351VE. They have a 60mm compressor inducer and 60mm turbine exducer, not exactly stellar for a rotary, but good for 350ish whp.
I was controlling the VGT rather crudely with a spring-preloaded air cylinder with open and close pneumatic ports, a solenoid, and a small pressure accumulator w/ some check valves. The solenoid was controlled with a digital output from the ECU, so the only tuning option was change the open/close setpoint or add more preload, set the minimum AR size with a bolt/jam nut on the lever arm, and adjust the preload on the air cylinder.
Granted, this was 5 years ago and I was using an archaic Megasquirt MS2, I was very hardware limited – no monitoring turbine speeds, eMap, ect to make tuning changes.
What it did do well – at the small A/R setting (default for low RPM/low boost) it was QUIET. With a 3” exhaust and nothing but a Borla XR-1 muffler, it was quieter than my full Racing Beat 3”. Because I had the accumulator, I could store pressure and actuate the air cylinder when the engine wasn’t in boost. Which was neat because I could open the VGT at idle if I wanted the car loud or quiet. Pretty pointless but a cool party trick I guess.
With the VGT cranked down hard to get max spool, It would surge the little 60mm compressor, but the eMap would actually open the VGT before the air cylinder. It definitely felt choked out at high RPM. It also made drivability really jerky because it would come it to boost fast and abruptly. Fuel mileage also sucked.
Ultimately, I went to an EFR 9180 and it had better drivability, better torque past 3500, and made about 200whp more.
I think having a medium sized primary A/R and a giant secondary A/R would be great for the larger EFR turbos like the 9280.
Any update on these? After my wedding, I plan on doing a refresh/upgrade to the FD and selling my old setup. I'm interested in the iwg and the variable housing option. This honestly sounds like the most ideal setup for me on paper (same power if not more than my 6766 with an even broader powerband), plus the simplicity and reliability of an iwg setup.
Any update on these? After my wedding, I plan on doing a refresh/upgrade to the FD and selling my old setup. I'm interested in the iwg and the variable housing option. This honestly sounds like the most ideal setup for me on paper (same power if not more than my 6766 with an even broader powerband), plus the simplicity and reliability of an iwg setup.
Our variable EFR housing is EWG only. Its took complicated to use with an IWG setup, and probably make boost control even harder under certain conditions.
Currently deciding between the 8374 and the 8474. My only reason for leaning towards the 8374 is the surge line is shifted to the left more than the 8474. But if the 8474 doesn't have a surge issue and it can perform at high boost, i know which one i am getting!
Im realllly excited to see these results. The new EFR turbo seems like it'd be exactly the evolution of the already amazing turbo the hardcore racer is looking for... a potential game changer for the modded 13B
Originally Posted by Turblown
Guys at HPAcademy are buttoning up the V mount at the moment, then its dyno time!
01-22-19, 05:31 PM
