posted on August 22, 2012 23:00
Turbosmart Time Attack FC RX-7
by Khiem Dinh
Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing. All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.
The FC is the middle child in the RX-7 family meaning it doesn't get quite as much love as the other two. The 1st generation FB was a pure sports car that really introduced the rotary to North America while the 3rd generation FD was (and still is almost 20 years after its introduction) sex on wheels. The FC was designed to be a little softer than the FB, but it was still a better performance car all around with an independent rear suspension and rack and pinion steering. Of course, you could also buy the FC with boost! For the 2011 World Time Attack Challenge, the boys down under at Turbosmart decided to show that the FC is a highly capable car even with a simple build.
The car originally was owned by a nice older Greek lady and was bought from her with the intent of having a fun street/track car which could also be used for product testing. Rotaries put out a lot of heat and therefore provided the perfect testbed for pushing components to the extreme. After competing in various rallys, hill climbs, circuit races, etc, the car was entered into the 2010 Superlap event at Eastern Creek. The Time Attack bug swooped in and bit the team convincing them to take the car off the street and convert it into a proper track-only vehicle to compete in the 2011 WTAC. This was the result.
|Yes, there is still a rotary under the hood! This makes Eric happy. Go-fast boost is provided by a Garrett T04Z which combines a big 63trim, 84mm compressor wheel with a 76trim, 74.2mm turbine wheel. Rotaries do not like back pressure at all as back pressure can lead to detonation and spitting apex seals out the exhaust ports. Therefore, a turbo for a rotary typically has a larger turbine wheel matched with a compressor as compared to a typical piston engine turbo. This 13B FC3S engine was built by Pac Performance specifically for E85. The build included being dowelled along with a bridge port. Rotaries make a lot of power per pound of boost compared to typical piston engines; the 13B actually behaves pretty similarly to a Honda F20C in a S2000 which has one the highest volumetric efficiences of any car piston engine in production. This rotary is putting out a healthy 600hp at 18psi of boost.
|Take note of the intake tube going to a sealed box. Thermal management under the hood is critical, so pay attention to all the heat shielding and wraps used; heat shields or wrap are used on the turbine housing, between the turbo and engine, around the fluid reservoir on the firewall, on the wastegate dump tube, compressor outlet, and the water line to the turbo just to name a few places. The exhaust manifold, dump tube and intake manifold are also ceramic coated by Hi Octane Racing to further manage the heat issue. Also check out all of the sweet Murray clamps! That's some more serious race car stuff.
|Regulating the wastegate flow is a Turbosmart Pro-Gate50 featuring a 50mm valve of course.
Thursday, August 23, 2012 2:40 AM
It's a little disturbing how similar this build is to my Nurburgring FC build...and comforting at the same time. The main hoop base plate only looks partially welded, what's with that? I do think I'll be borrowing their wing mounting technique, as I have the same wing.
Thursday, August 23, 2012 3:21 AM
I wonder why the two kickers coming down from the main loop are not welded onto the shock towers (the FC has HUGE shock towers, so it shouldn't be too hard to tie in all the triangulation).
They're welded onto the flat floor instead. Anyone has any explanation?
Thursday, August 23, 2012 4:51 AM
My guess is a WTAC rule restricting number of points that can tie into the suspension mounting locations. That's just a WAG (wild ass guess) though.
Thursday, August 23, 2012 10:03 AM
What's kind of interesting to me in a way is that the "standard" rotary turbos seem to always work out to being on the larger trim side of things... 60-1s at 60 trim, the T04R/Z at 63 trim, etc. Or is that more just a matter of the larger trim turbos being more optimal at the lower boost levels most rotaries are running at? Anyone know what the inducer/exducer on CART turbos is like?
Also, I like how the power number is pretty similar to that of the Garage Revolution car from last year. 600 vs 650hp, but at 4psi less boost. Even if those numbers are just at the flywheel (they pretty much have to be) that's doing pretty darn well.
Thursday, August 23, 2012 1:06 PM
I'm in love with this car already, simple and fairly light at the same time. Engine bay still looks a bit cluttered though (not sure I could do better with a race-spec turbo rotary but I've never tried either).
Friday, August 24, 2012 3:22 AM
I wonder why there is no ducting for the rotors? Rules, or because the track isnt brake intensive?
I wonder what kind of diff they are using in that stock pumpkin.
Friday, August 24, 2012 10:36 AM
From the Turbosmart guys:
With regard to a couple of the questions, the main hoop is fully welded to the floor, it's just that the base plates have a fold in them so there is no gap. In the photo it looks like a big hole.
With regard to tying the cage together we got someone to do this for us but the result was not what we wanted so we cut it out again.
We will be fixing this up in the future.
Friday, August 24, 2012 12:13 PM
Remember that this is not so much a race car as it is an R&D car. Our CEO and staff also just happen to really like racing as well ;-)
There is a ton of sensors and wiring for datalogging most everything. There are also multiple un-used fittings and flanges for mounting various products on for testing.
It is a dyno/load cell on wheels.
Even our daily drivers are fully outfitted with dataloggers.
Sunday, August 26, 2012 10:16 PM
RotaryKnight: I suspect that since its a Time Attack car and only needs to go around the track a lap or two that it does not need brake ducts.
Tuesday, September 04, 2012 7:37 PM
awesome FC stuff, Marty keep us in the loop on all that hotness down under!
Monday, April 14, 2014 2:29 AM
Can anyone identify that specific model APR wing?
Also, I'm curious as to what their alignment settings are and also why they chose to go with a 255 on an 8.5 wheel, I would have thought it would have been more effective on a 9 or 9.5, even if they had to add more front camber to get it to clear the fenders.