May 1, 2008
James Y. Gleasman, chief executive officer of Torvec, Inc., announced today that Torvec is a proud sponsor of the RIT Formula SAE Racing Team’s F16 to be unveiled at RIT’s “Imagine RIT: Innovation and Creativity Festival” to be held at RIT’s college campus on Saturday, May 3, 2008.
The F16, which will be showcased to the public beginning at 11:30 a.m. at Building 04 (SAU Loop) is the college’s entrant in the Formula SAE and Formula Student Germany competitions. RIT’s racing team chose to replace the Torsen differential it had previously used with Torvec’s more efficient, lighter and less expensive IsoTorque differential to enhance the handling and safety of the car.
May 5, 2008 - Update
We at Torvec would like to congratulate RIT’s Formula SAE Team on a wonderful unveiling and demonstration at RIT’s Imagine Festival this past weekend.
Each year a new car has to be designed and fabricated from scratch. To design this year’s car was particularly difficult since last year’s car was 7th out of 120 in the Nation. The list of items that had to be designed is impressive and here are a few:
- Custom Chassis
- Custom Brakes
- Custom Suspension
- Custom Electronic Launch Control
- Custom Speed Encoders for Braking & E-Launch Control (not heat sensors)
- Custom Drive Sprocket & Chain (more efficent & lighter then ring & pinion)
- Custom Wheels
- Custom Carbon Fiber Steering Wheel
- Custom IsoTorque Differential
Over the past week members F16 Team worked around the clock, assembling and polishing the F16. With hundreds of spectators in attendance, the F16 preformed beautiful, and looked spectacular at its début. The students have been great to work with and are eager to learn. Torvec is very happy to continue is relationship with RIT and wish the team great success in the SAE competition in Detroit. Some of the team members’ impressions of the IsoTorque™ are as follows:
Overall, I was very impressed with the IsoTorque differential. I noticed
three major improvements over our existing Torsen Type II. First, corner
exit acceleration and traction was much improved. Power could be applied
much earlier ( just after the apex ), and full throttle was achieved much
sooner. Secondly, when power was applied, the car's cornering radius
tightened. This helped the skid pad event. It was obvious that the engine
power applied to the outside rear wheel helped yaw the car around the
skidpad. Lastly, when the car lifted an inside rear wheel, the wheel did
not spin up, like our Torsen would, but spun at the speed of the outside
wheel. We obviously try to keep all the wheels on the ground, but it is
nice to not be limited by inside rear wheel lift in the tuning process.
-Ryan Baldi
From first hearing about the IsoTorque and what it promised, I was excited as well as a bit skeptical. That being said, I mentioned on more than one occasion that if it does at least half of what it is claimed to do, it will be better than what we've got. I feel that being the Vehicle Dynamics leader for the RIT Formula SAE racing team, as well as an Autocross and Endurance driver has put me in an interesting position to experience how the IsoTorque operates from both a tuning standpoint and also from a driving standpoint
I do not feel that the standard Torsen differential (be it type 1 or type 2) is all that bad, I also do not feel that viscous or clutch type limited slip differentials are bad either, and neither is your standard open differential found in most passenger cars. However, they all have very distinct advantages and drawbacks, and in a racing atmosphere it certainly doesn't take long to find out what those are. I'm not going to get into each one individually, since this isn't about the drawbacks of every other differential on the market, but I will say that these drawbacks all have to do with the operation of the differential itself.
My first real experience with the IsoTorque from a Vehicle Dynamics standpoint was immediately after it was installed and the car was still on stands. I noticed the rear wheels moved very freely and independently of each other, exactly the way an open differential would. This made me wary and interested in seeing how the IsoTorque would work if the inside rear wheel were to lift off the ground. It just so happened that we put the IsoTorque first in the car on the same weekend that we really started tuning our dampers. As a fairly standard exercise, we put the dampers at the limits of their range to see what the car feels like when you know the dampers are set overall too stiff and too soft. This exercise helps both myself and the test driver see and feel, respectively, what that does to the handling of the car. The first thing I noticed when the dampers were set to full stiff, was the car was lifting an inside rear wheel off the ground, which is not particularly surprising. The second thing I noticed was that the engine, nor the lifted inside rear wheel were revving up. In fact, it looked much like a kart running a solid rear axle. The next thing I noticed was that as the driver got on the power on corner exit, his line tightened up and the car yawed just a little bit more into the corner, but without sliding out. Things were looking promising for the IsoTorque.
When the driver pulled in and we did our standard debriefing, he did not mention anything about the inside rear wheel lifting, I had to bring it up. On mentioning that the inside rear was lifting he replied with "It was?" and proceeded to say that he hadn't even noticed it, and upon further thinking about it, realized that at only one point had he had any indication of that behavior, but it was to such a minor extent that he hadn't even realized that the inside rear had been lifting off the ground, and trust me when I say it was lifting off the ground quite a bit. This bit of information was very interesting to me, considering how well the IsoTorque differentiates with no load on it. I realized at this point that the IsoTorque can, at the very least make up for deficiencies in suspension and/or chassis design and tuning. That's not to say that the car doesn't require tuning, but a setup which would normally be bad with a limited slip differential and catastrophic with an open differential, is more or less inconsequential with the IsoTorque.
My next experience with the IsoTorque is as one of the privileged few whom get to feel it as a driver. At first I can say I didn't really notice a difference. It behaved similarly to the Torsen we normally run, on the lines I normally drive. Knowing what it is supposed to do, however, I started playing around with getting on the throttle earlier in corners and immediately noticed a difference. After driving it a bit more and learning what it likes to do, I noticed that lines through corners should be changed to accommodate the way the IsoTorque works. The place I really noticed it was in low speed, off camber corners where the car tends to understeer, giving just a little bit of throttle, even if it's just the slight amount to keep from scrubbing off speed, I could literally feel the torque bias to the outside wheel and yaw the car just a little bit more to tighten up my line. As I modified my line for the IsoTorque, I found that if I got it 'right' my apex would be extremely late in the corner because of how well the IsoTorque can put the power to the ground and how it helps to tighten the line. I'm not saying that's the optimum line for the IsoTorque, but that's the line I ended up with. I'm sure as I become more and more experienced with it, my line will continue to be modified because of how much more speed I can now carry through the corners. The initial indication, however, is that the line it likes is a bit more of a squaring off of the corner. The key is that to 'square the corner' off, you would put the power on, almost as you start turning, as opposed to the standard 'square off' where you brake, turn, power. It seems like it's more of a brake, turn + power.
All that being said, I'd like to mention how the IsoTorque can affect a power-on oversteer condition and high speed corners. Most of where I noticed it was in low speed corners, where the power application is a greater magnitude relative to speed. At this point, I can't say I noticed it doing anything out of the ordinary in high speed corners, but the car did feel planted and kept a very true line, particularly on corner exit. I cannot comment on how much this is due to the IsoTorque and how much is due to the suspension setup. I do suspect that with experience, I will be able to brake less and be on the power more through relatively high speed maneuvers, as the IsoTorque will aid in keeping a tight line. As far as power-on oversteer and an outright slide or 'drift' goes, I can say it is an extremely linear breakaway. My experience with other differentials is that they tend to make a car understeer up until the limit of the rear tires is reached and then they let go. Even with a nicely tuned car, this behavior is evident to some extent. With the IsoTorque, even at the slightest addition of power it increases the rear slip angle. It is completely linear relative to throttle position and power application. If you give it a little bit of power, it tightens up your line, and as you progressively add throttle, it progressively slides the rear end out more. At a certain point, this becomes a slide or 'drift' as you have exceeded the grip of your rear tires, but it comes very smoothly and extremely controlled. This is an extremely useful behavior, since if you give it just a little bit too much throttle, it doesn't just kick out, it slides just a little bit more and you can feel that you're no longer putting the power down as effectively. Just waiting a second for the corner to widen up just a little bit more (since this almost always happens on corner exit) will let everything come back in line right where it wants to be. And if you happen to really overdo it and throw the thing into a full blown drift, there is no drama, it is just smooth, it goes out smooth, it slides smooth, and it comes back smooth. On that note, if you want to light up the rear up and whip the car around (sometimes advantageous after a spin) it will do that too.
In conclusion, the IsoTorque does not defy physics. It does not give you rear steering. It will not magically allow you to stomp the throttle at the apex of the corner without kicking the car out. What it does do is provide smooth, linear control of the slip angle of the rear end of the car. In small degrees, this can tighten up your line, in large degrees, this can be a full on drift. The one thing that is constant is that it is a perfectly linear relationship with throttle position. It does, very simply, just what you want it to do when you want to do it. At this point, I do not have a single complaint with the operation of the IsoTorque. I look forward to exploring the dynamics of this differential further and finding out the finer details of it's operation and searching for those places on the track where I can give it just a little bit more throttle just a little bit earlier to tighten my line up just that little bit more to get me that last little bit of speed.
-Martin Iwanowicz
RIT FSAE F16
Vehicle dynamics leader.
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