just a heads up to interested parties that the aforementioned issue has an excellent tech writeup on the RX6b. lots of variants and i note that while there are no compressor maps all the variants run well at boost levels considerably above one bar. while i am a garrett fan i have a friend who has had a very good experience w his RX6b... and not even water cooled.

btw, i really like Dsport as it does have a fair amount of engineering oriented material.

howard coleman

 

Thanks good info! I might have to raise the psi on my RX6B

 

Yeah saw that article...very interesting stuff. And I concur, there's some excellent techie stuff in there on occasion! I came away with the conclusion that there are better options out there for the rotary but there are more than a few who believe in those ultra-small (by GT series) turbines.

 

there is an interesting rotary related comment in the article.

the hot side of the rx6b has only one turbine wheel size but has 7 hot housing sizes. according to the article only the two largest (P25 and P27) fit the rotary. the sizing is cast into the rearward facing section on the turbine housing.

i have personal experience that the rotary likes big hot housings. i run two TO4s and started last year w 2 .48 hot housings. i was getting as much as 65 psi of pre turbo backpressure. i now run .82 housings and have 17 psi of backpressure at one bar.

i digitally log pre turbo backpressure...

so i suggest you that have rx6b's check your housing size and let us all know what you have.

howard coleman

 

RX6a: TCW76 + P27
RX6b: TCW77 + P27

 

I've had my rx-6 at 20psi with no problems so far. The little thing just won't quit. It's defiantly not as efficiant than a t66,t78 at those boost levels but I can't get over the lag of them turbos.

 

according to the Dsport article the rx6b measures:

cold side

82 X 61mm or 3.22 X 2.4 inches
solving for area 8.14 X 4.52
that's 6.33 sq inches average area.

very close to the GT35 that measures 6.35 sq inches average area.

the GT35 flows around 60-65 lbs/min so the cold side of the RX6b should be in that vicinity.

the interesting metric is the cold/hot ratio.

the RX6b w only one sized (small v the cold wheel size) hot wheel appears not as competitive especially for the rotary.

hot side:

62 X 57mm or 2.44 X 2.24 inches
solving for area 4.68 X 3.94 sq inches
that's 4.31 sq inches average area.

cold to hot ratio= 6.33/4.31= 1.46!!!!

the cold side is much larger than the hot side. ratios generally run from 1 to 1 (R85 for example) to 1.28 for the GT42. (obviously there are various iterations of each of these turbos which changes the ratio) generally the ratio is around 1.1 to 1

most people feel the rotary needs a bit more exhaust sizing than a piston engine which makes the smallish RX6b turbine wheel even more of an issue.

my purpose is NOT to knock the turbo. i have a friend who runs it and it runs well. i just find the metrics interesting. according to the article the turbo runs well into the 30-38 psi range and can make 550-600 fwhp!

at his point either the article is wrong or the turbo is being held back by it's smallish turbine wheel. w a cold side similar to the GT35 it should make 60-65 lbs/min and make 600 rear wheel piston hp, not 550-600 flywheel piston hp.

since the cold side wheel is virtually the same size as the GT35 and it flows 60-65 lbs/minute that should translate to approx 600 rw piston hp. you need to divide it by 1.3 to get to rotary rwhp... approx 460 rotary rwhp max.

anyone want to chime in as to what they have dynoed w the rx6b.... also, in light of the statement that the turbo is most efficient around 30 psi it would be interesting to hear from anyone that has run high boost. i know i can search and will find lots but it would be good for the thread.

howard coleman

 

i had a friend buy one of these kits right when it came out, in mid 2000. we put the kit onto a 95 fd with a stock motor, and the m2 medium intercooler. it also came with a "pre programmed" power fc. kit did 342rwhp@10-11psi right out of the box, spooled like the stock twins.

the thing i remember is the HEAT from it. i think it was worse than the stock twins.

 

i made 380rwhp on crappy 91 octane with the rx6 =)

 

I was always curious as to what the true capabilities of this turbo were. I know that the Apex'i FD that runs in D1 is using an RX6 turbine. And they say that it puts down 450whp. Of course I have no idea if that's true or not, but that is what they are saying. They ran one of the AX series turbines for about half of the '04 season IIRC, but then switched over to the RX6 because they liked the way it spooled better. Just thought I'd throw that info in there.

Zach

 

It's a good turbo, mine survived three blown motors and has around 40k on it right now with no signs of wear...

All the other parts like the manifold and downpipe are well made too...

 

The only problem is I don't think that they make kits for the FC. And aren't those kits expensive as hell?

Zach

 

I was under the impression that the Apexi' D1 car used the AX75. I even has sticker on the car that say "Apexi AX Series Turbine"

 

They used to use the AX series turbine but then switched back to the RX6 in the 05 season

 

Yeah, I had a nice conversation with the team mechanic at the D1 back in December. He explained that they liked the RX6 turbine better because it had better response and gave them a flatter, more usable torque curve throughout the rev range.