posted on July 16, 2012 19:00
Under Suzuki’s Scorch Racing S15-The DIY Time Attack Otaku
By Ellie Nikolova
Do you remember Under Suzuki from the winter time attack season here in Japan?
Under is Tomohiko Suzuki’s nick name, which came from the car’s prior understeer problems and his status as a self funded privateer. Suzuki san is the builder, owner and driver of the all-carbon Scorch Racing S15 Silvia, the fastest privateer time attack car on Tsukuba Circuit. Suzuki is aiming for victory this year in the WTAC (World Time Attack Challenge). He finished 5th
last time and he is determined to become World Champion. With the RE Amemiya RX-7 and Top Fuel S2000 participating, the Cyber Evo back in the game and of course MotoIQ’s own Team America Skyline GT-R BNR32, it is going to be one very tough fight for sure!
|The Scorch S15 is the fastest privately owned time attack car around the Tsukuba Circuit. We have always liked this car's well balanced beauty and simplicity, getting speed with step by step refinement over brute force.
|The Scorch S15's front aero has some influence from aeromaster Andrew Brilliant we think. We can see some of his signature design cues. The higher center and upward bend of the front splitter is not a mistake. It makes the splitter less pitch sensitive, a good idea on a production based race car that runs on tires that prefer to be softer sprung than race slicks. The Scorch S15 has a lot of chassis movement due to its softly sprung, DOT radial based race tire friendly suspension and the splitter shape keeps downforce more consistent as the car, pitches, squats and rolls. You can't see it but there are diffusers in the front belly pan ahead of the front tires leading to the wheelwells to make more front downforce. Usually front downforce and front aero balance is more difficult to get than rear downforce in a production based race car. We understand that the Scorch S15 actually has a lot of front grip and the latest developments have been focused on increasing rear downforce and aero grip.
|The Scorch S15 is a very simple car at heart. No pedal boxes, long steering columns and rear set seats. The unibody is largely unaltered. The interior doesn't look like a high buck time attack car but a well sorted and clean club racer.
|A Racepak digital dash and data logging system is used. For engine management a HKS V-Pro is used in conjunction with a lot of stock stuff so it helps if the dash can be independent of the engine management with its own sensors and wiring.
|The S15 is staged first on pregrid. You can see the upraised center section of the splitter better here. Also note the extensive hood venting. This helps the air exit from the intercooler, oil cooler and radiator which improves aero by forcing air to flow over the car and reduces drag by reducing trapped air underhood.
|The passenger side footwell holds an Odyssey PC925 dry cell battery, the relocated fuse and relay box and the V-Pro engine management system. You can see the sequential shifter for the Holinger RD65 six speed tranny. Surprisingly the stock steering column is retained.
Monday, July 16, 2012 1:23 AM
Interesting on the spring rates.... I wonder if it's due to a limitation in tire choice. Going overly stiff may just cause the car to skip around depending on the tire construction, so maybe softer is better in this case.
Monday, July 16, 2012 3:20 AM
@spdracerut: I was surprised too to read 12K up front and only 10K in the rear. If I'm not mistaken Advan 050's biggest tire is 295, maybe that 's why....
I'm surprised the cage doesn't extend thru the firewall onto the shock towers. That creates some unwanted flex.
Those nickel-plated Brembo brakes are to die for. Replacing the stock pedal with some adjustable Tilton/AP Racing maybe it would help Suzuki to shave some 10th's of his time.
I'd like to know more about those funky looking wing-plate shape...
Monday, July 16, 2012 6:35 AM
Gotta love the efforts of the underdogs. I have to wonder now... I know Yoshi Suzuka is doing consulting work nowadays... it's seeming like more and more people are trying to do tunnels and stuff for downforce solutions, what would be more fitting than to have the designer from the Nissan GTP days contributing?
Monday, July 16, 2012 7:55 AM
I read somewhere about the differences between Japanese and American chassis philosophy. Over here, we believe you should make a chassis as stiff as possible, which would include tying a roll cage into the shock towers. The Japanese, however, believe that some chassis flex is a good thing, which is why they don't usually tie the cage into the shock towers.
Monday, July 16, 2012 9:44 AM
I have been following Under Suzuki and Takemura's blog for a few years. They documented pretty much everything along the build. The S15s cage is tied to the front strut towers and there is no rear diffuser(at least not a proper one). The flat piece you see above the exhaust is just a brace that connects those massive side venturis.
Monday, July 16, 2012 10:47 AM
the Cylinder head is fron a SR20VE engine. im suprised there is no mention of this :(
Monday, July 16, 2012 12:46 PM
"The SR20DET pumps out 800 ps @ 8000 rpm which is about 680 hp."
800ps is about 789hk i think, not 680
Monday, July 16, 2012 1:56 PM
The VE head makes sense. THe 800ps is probably crank, which translates into roughly 680whp and that's well within the range of a GTX3582.
Monday, July 16, 2012 3:23 PM
My Favorite S15, I can't wait to see what he pulls with the new aerodynamics. Is it really still a SR20DET when it has a VVL head on it?
Monday, July 16, 2012 7:21 PM
Trying to confirm the VVL head now
Monday, July 16, 2012 7:26 PM
if you look at the front of the motor you can see its a VVL the bolts are on the outside of head since there no clearance for the CAS on the RWDs. also you can see that intake manifold is flat against the head and he is using a 20v valve cover which only fits on FWD sr applications.
Monday, July 16, 2012 9:54 PM
Kenku Andrew Brilliant understudied Yoshi Suzuka in Japan. It seems they work togethor, I read in an interview.
Tuesday, July 17, 2012 1:02 AM
Which explains why the front aero looks like it was designed by Andrew.
Tuesday, July 17, 2012 2:58 AM
Front cage tubes.
Takemura san clearly stated it has stroked 2.2L+VE head..though in Japanese.
The brace between side vents.
Tuesday, July 17, 2012 8:26 AM
Er, let me be more clear... to my knowledge I don't think Yoshi Suzuka has had a hand in any time attack cars much less this one; I just think it would be cool if he did. I just kind of admire what he did with the limited resources he had; Electramotive built their own scale, moving floor wind tunnel, and most of the Nissan GTP cars were developed on it.
Also, I'm not saying any of this to speak against Andrew Brilliant, it's simply a matter of knowing some things in (and being heavily impressed by) Yoshi Suzuka's resume and not knowing Andrew's aside from him being mentioned on various time attack stuff... and I'm sure most of us here will agree that that doesn't really show off a designer's chops as well as a prototype car where they have a lot more freedom.
Tuesday, July 17, 2012 9:46 AM
I am almost positive I read on another site that Andrew Brilliant was doing the aero work on this car.
Tuesday, July 17, 2012 11:56 AM
Ellie just confirmed from Suzuki-San that the head is an SR20VE 20V P11 head. The 20V is an awesome head, the ports are quite different and flow better. I have one lying around and it sort of reminds me of a K20A head. It's rumored that the engineers that designed the 20V head went to Honda and designed the K20A head.
Tuesday, July 17, 2012 12:05 PM
Makes sense about the 20V head and K20 head. From the dyno numbers I've seen of the SR20 w/20V head, they put out similar (though maybe a bit lower) horsepower per boost level numbers as K20s/F20Cs.
My rough hierarchy of head flows from bad to good: WRX/STI ~ SR20 > 4G63 > 4b11t > SR20 w/20V > K20/F20.
Tuesday, July 17, 2012 12:29 PM
The EJ207 heads seem to do a lot better but... ugh. Speaking as a WRX owner, it just bothers me how the things don't flow worth a damn compared to most of their competitors. The smallest of the engine family has a 92mm bore, the valve sizes are reasonable and heck, even bigger than the K-series... but they just don't seem actually flow.
At least there's apparently enough meat in the suckers to somewhat fix that.
Tuesday, July 17, 2012 5:56 PM
Kenku, Andrew Brilliant here.
I am sure that Suzuka san would love to do a time attack car if the right one came along. He is just as fond of no rules designing as I am. To be frank, time attack stuff is sort of my hobby and I like it because it is fun. The bread and butter of an Aerodynamicist really cannot be time attack cars or you will be in the poor house for sure. Suzuka san's specialty is wind tunnel development, my specialty is CFD. I think that while those two compliment well for us, to date I dont think there have been any wind tunnel development projects in TA. There is Nakajima at voltex, he does some ex post facto and limited wind tunnel in the Mie University trainer wind tunnel. They test a few concepts. While Nakajima is obviously a smart guy and I find his concepts refreshing.. its a totally different sort of development compared to highly evolved highly tested and refined wind tunnel projects like an LMP car.
If you dont use a tunnel or CFD its sort of a test of you as an aerodynamic theorist, how well you can guess at what the air will do? Supercomputers process that question normally. Perhaps as time attack evolves I can get him excited and involved in something.
Tuesday, July 17, 2012 9:10 PM
Hah, wow... I love that this is a place where people actually involved in cool stuff just pop in.
It's actually really interesting some of the ways that aero in the timeattack stuff is evolving; there's not a heck of a lot of classes that actually allow more or less unlimited aerodynamics. It's slightly frustrating too, in that I have things of my own that I want to try, but not the resources to do them. I'm willing to be that's true even for people fielding cars, though.
Also, part of me has to wonder about the future of time attack if resources devoted to it get to where there is wind tunnel development being undertaken. I can't imagine, for example, the Windshear facility in the US is very cheap to rent.
Thursday, July 19, 2012 4:53 PM
Mike,can you confirm if this motor is sleeved? Seems like awfully a lot of power for stock sleeves, at 87mm bore.
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