posted on September 10, 2013 13:31
Some people, especially MotoIQ readers, like doing things the hard way. After capturing the 2007 and 2008 driver's championships, 2008 manufacturer's championship, and amassing six wins, six poles, twenty six top fives, and thirty one top tens in the highly competitive Speed World Challenge GT series with their Porsche 911 GT3s, K-Pax racing decided it was time for a challenge. For the 2009 season, K-Pax partnered with Volvo – the company that brought you standard seatbelts, curtain and side airbags, and other safety items – to race the S60 in GT. Because when you think of alternatives to Dodge Vipers, Porsche 911s, and Corvettes, you immediately think of the Volvo S60. Randy Pobst of K-PAX, a MotoIQ reader and contributor, stays true to the MotoIQ spirit of doing things the hard way.
That's not to say the Volvo S60 is a slouch. Powered by a turbocharged 2.5L engine routed through a Haldex AWD system, the Volvo S60 was designed to compete with the sport sedans offered by other manufacturers. Volvo teamed with K-Pax to show that the S60 packed the punch necessary to compete with the sports sedans and cars featured in the Speed World Challenge GT class. What it lacked in slippery shape, it would make up for with exit traction and turbocharged torque.
AWD to power through shrubs!
The Speed World Challenge series is designed to get recognizable cars you and I could buy (pending funding, of course) to race each other on a relatively level playing field. By carefully scrutinizing the results of each race to consider how each vehicle's rule set is affecting its competitiveness, World Challenge rules makers are constantly striving to achieve parity. With the varied field, this is not an easy job as proved by the early dominance of the Cadillac CTS-V a number of years back. Rules makers limit weight, inlet restrictors, maximum RPMs and other modifications to keep things even. Still, all cars generally retain their inherent flaws and strengths to make for interesting tactics. The Corvettes and Vipers are well balanced and pretty good at higher speeds due to power and aerodynamics, the 911s are kings under braking and mid-late corner speed, and have one of the smaller frontal areas in the series, making speed towards the end of the straights a definite strength. The Volvo? Being the only AWD car in the series and toting prodigious turbocharged power to overcome sedan heft and comparative brickiness, the Volvo is the absolute king of the standing start and low speed corner exit. As car owner Jim Haughey aptly puts it: "P1, turn 1."
In a series featuring Audi R8s, Dodge Vipers, Corvettes and other sports cars, the K-PAX S60 makes up for Sedan brickiness and heft with turbocharged power and AWD traction.
Wednesday, September 11, 2013 7:33 AM
Wow, been wanting to see a writeup on those for a while. I'll have to look at it indepth later for more details and more comments, but thanks a lot for this. Just as a comment, the Ohlins TTX dampers are twin-tube, but not in the same way most Konis and most KWs are twin-tube. They actually explain it pretty well if you look it up; it's a cool idea to solve some traditional monotube issues.
Wednesday, September 11, 2013 8:23 AM
Nice article. A comment and a question:
-That radiator swirl pot looks more like an oil reservoir for a dry sump.
- I would have thought a nose heavy car would need more downforce at the rear. Can you explain the theory?
Wednesday, September 11, 2013 10:31 AM
@ Dan: I'll look it up for sure. I looked on their site for more info, but it was mainly marketing jargon. Got a cool link?
@ Wrecked: if you look carefully at it in the photo towards the bottom on page 6, you'll see a big honkin' coolant hose coming out of it.
For downforce: a nose-heavy car wants less downforce out back. Downforce adds grip, and the last thing a nose-heavy car needs is more grip in the back for the sake of handling balance. Randy wants the car to be as close to a "drifter" as possible. As the great Paule used to tell me all the time: "loose is fast, don't be a p-ssy."
Wednesday, September 11, 2013 11:42 AM
How heavy is the engine block and the transmission?
oem spec or their spec.
any pictures available of their exhaust system and t-case?
Wednesday, September 11, 2013 11:52 AM
Site ate my post; google "ohlins ttx fluid circuit" and look at the user manuals. I'll do another post when I'm not on my phone at work.
Wednesday, September 11, 2013 12:30 PM
@ awdu13: Not sure on drivetrain weight.
No pics of the exhaust or t-case, sorry. Both are pretty buried, and we were snapping pictures in the pits while they were working.
Wednesday, September 11, 2013 12:57 PM
Is this a rare example of an awd car limited to front weight bias?
Wednesday, September 11, 2013 1:08 PM
Most front engined AWD cars are nose heavy. This one is transverse engine, which makes it especially nose heavy.
Wednesday, September 11, 2013 2:28 PM
I have been told in the past to keep the aerodynamic balance similar to the weight distribution in order to maintain predictability of the handling.
Wednesday, September 11, 2013 3:12 PM
Any details on the radiator sprayer reservoir and system?
Wednesday, September 11, 2013 3:39 PM
@ blops: dagnabbit, I meant to include info on that, but ended up getting sidetracked on other cool things for the car.
No shots of the sprayer, but they aren't allowed to use it during qualifying, and cannot have more than 6 gallons of water.
Wednesday, September 11, 2013 6:03 PM
@ Rockwood, Re: Downforce. That seems so obvious now that you say it. More downforce on the rear will make it push more.
Why does the coolant reservoir line need an Earl's filter?
Wednesday, September 11, 2013 6:03 PM
http://performanceshock.com/TTX40_TTX46MT_Owner_Manual.pdf About what it says on the URL. Good diagrams for the TTX40 Mk2 around page 12.
In synopsis, what happens is the shock piston, in the inner tube, is solid - no shims, holes, etc. The fluid displaced goes to the end of the inner tube which, unlike Koni-etc-style twin tubes is open to the outer tube. The fluid then turns 180 degrees and goes to what I'm going to call a bulkhead - it sits between the two sides of the outer tube, so that all the oil flow from compression or rebound has to go through it to get to the other side. All the valving is in there - in fact, the shim stacks are under the adjusters.
By doing that, it gets a lot easier to have the adjusters work properly - it's a bleed valve and preload on the shim stack and they're both right there. You can also revalve the shock entirely without taking it apart or even necessarily off of the car. Most importantly though, because moving the shock either way has all of the force generated through compression, it needs far less gas pressure to avoid cavitation, and thus has less seal drag. See, conventional monotubes on the compression stroke have the pressure drop across the piston result in the chamber on the rod side of things having pressure drop... and if it drops lower than the gas pressure, voila, cavitation. There's workarounds like base valves and canisters with flow restriction, but the TTX design just gets rid of the problem entirely.
Dynamic DSSV and Koni 2822s work the same basic way too, as far as I can tell. Nice pieces of kit, wish I could afford to play with them.
Wednesday, September 11, 2013 10:35 PM
Pretty much the exact same Volvo you can buy off the local dealer. Except little things right?
Wednesday, September 11, 2013 11:45 PM
I hope no one thinks that I am being a jerk, but there is one slight error in the description of the TTX damper. The small tube you described as a High speed blow off is if fact the gas reservoir. Due to the thru-rod design the res can be very small, however you still need to account for oil volume change due to heat. And even thought the TTX design uses a pressure rise to generate force it still needs some gas pressure to work correctly. Typically 5bar is used, however I have tested down to 1bar and seen little to no negative effect.
Ohlins does make a High speed blow off kit for that strut, but that one is not fitted with it.
@dan You are correct the Dynamic DSSV, Koni 2822 and also the Sachs formula matrix all use the same working principal. They just go about controlling the flow in different ways. From what I was told Sachs was the first manufacture to produce a truly 4way damper using this type of design...at lest that is was the Sachs engineer who designed it told me.
Thursday, September 12, 2013 7:19 AM
I think Quantum might have one too; thought I saw something in Race Tech a while back, but could be mistaken. Regardless, I remember that the opinion of some of the engineers was that it was a pretty logical way to move to do things; "we could fit all the adjusters down the shaft but it would get silly so why not put the valving here?"
How do they work at higher shaft speeds? From where stuff with the external valves showed up first (F1, high-aero stuff, etc) I always suspected that it was also optimized to deal with relatively small shaft displacement and high spring rates, and wondered how the valving concept would cope with stuff with softer springs and more movement like street or rally. The valving seems like it's a lot smaller than conventional monotubes and like it would hit a maximum flow... or is it just a case of just running appropriate valving?
If it's not obvious, I just spent a lot of time studying what's publicly available of this stuff.
Thursday, September 12, 2013 9:53 AM
@ Dan and Boots (shitty Shrek character? ;-p): thanks for the input, very much appreciated. And boots, while you may very well be a jerk, pointing out honest mistakes isn't one of them to me.
Now, if you argued an opinion with me, then yeah, you're a jerk! ;-p
@ tyndago: Note that I said recognizeable, not showroom stock. ;-p
Thursday, September 12, 2013 10:06 AM
@ Boots, updated the article. Thanks again!
Thursday, September 12, 2013 12:23 PM
@Rockwood - we have actually raced against them. In another form several years back in World Challenge GT - 2006.
They have some pretty crazy engineering in them by now.
Thursday, September 12, 2013 11:37 PM
@Dan You are right, Quantum does make a damper that uses the same principals.
I have heard of cases that will cause the a damper of this type to "hydraulic lock". of note the engineer that told be was working on a small formula car (Pro Mazda). If you look at the end of the TTX40 manual Ohlins gives a Vmax and Fmax for the damper. To combat the potential problem Ohlins and most of the others will ether use a shimmed main piston for super high speed blow off or as Rockwood mentioned Ohlins has a 5th external adjuster that will open a flow path that bypasses the adjuster assembly when I high speed event takes place. Both the TTX46MT and TTX40 can be configured with the 5th adjuster.
As far as how they work on bigger GT type or street cars....really good!! Both the ALMS GTC and Grand Am GT class leading cars use these type of dampers. Along with BMW team RLL in ALMS GT (Ohlins or Dynamic) , all of the Porsche 911 RSR's come equipped with them (Sachs), the Ferrari 458 (dynamic) oh and the car this great artical is about:)....just to name a few.
I personally fit them to Honda S2k (ohlins TTX36), Audi, BMW M3...really anything. the first comment is typically "Wow this thing is compliant!" They work very well and offer a far better compression range of external adjustment than a standard Mono-tub.
I really love this stuff too and I am very lucky to get to work on dampers for a living.
@rockwood very glad to help. thanks for giving use such fantastic content. there is no other place the web (that I have found) that covers racing they way you all do.
Friday, September 13, 2013 3:20 PM
Saaaweet! Very cool article. I have been a fan of Pobst for years and years now, but never had a chance to get a good in depth look into the cars he drives for Kpax.
It is amazing how far they take these Volvo sedans. Very impressive. I wish Volvo had people working for them that would create a good performance car for the street. Available to the masses.
It seems like they always have their priorities wrong when they make "performance" versions of their cars. I enjoy following their racing progress, and have tons of respect for the cars they run at the track, but it seems like nothing they do with racing trickles down to their street cars.
The Polestar has decent upgrades, but with only 2000 global units made, the Polestar is very rare (only 500 are coming to N. America) ... and it is still not a big performer.