I was at Putnam Park over the weekend. At turn 7, the slowest turn on the track, I was downshifting the ITR to second gear in the braking zone. The extra power going through the turn was nice, but I ran out of revs just past the track-out point and had to upshift. As a general rule, given the short time in the lower gear, is it worth the time/power lost in shifting for the extra power in the turn, or would I have been better off just leaving it in third?

Click here for a track layout of Putnam Park.



[Modified by nsxtcjr, 2:09 AM 4/23/2002]

 

I say it's ok to downshift if you approach a turn and you're still moving too fast. You need the engine braking so it's ok to downshift into 2nd. Then punch out hard and shift into 3rd.

 

Unless it is a race I would leave it in a gear that is easier on the equipment.

I have found that leaving it in the higher gear (3rd most times) translates to a smoother line thru a turn and better focus on finding a 'better' line (carry more speed rather than generating it).

At CMP...
Turn #11 can be taken in 2nd... but you are shifting into 3rd and then right back into 2nd...

I tried leaving it in 2nd (rev limiter a bit too long for my taste).
3rd gear = falling on my face trying to find torque.

Pic. ("S" shaped section on the lower left side of the pic) http://www.cmpracetrack.com/images/track.gif

Keeping the car in one piece is a deciding factor for me.

Willis

[turn # edit]


[Modified by Willard, 8:31 AM 4/23/2002]

 

Sorry, but I disagree with this. Brakes are designed to slow the car down much more efficiently and smoothly than engine compression. If you're still moving too fast to make the turn, brake more.

 

If you're already in the process of turning, you DO NOT want to hit the brakes during the turn. In fact you want to bring the car back on line with more throttle, that's why you should downshift back into the powerband. And punch out of the turn. Hit the brakes to slow you down as much as possible BEFORE entering the turn, not during the turn.

 

Forgive me, but I can't think of ANY reason to allow your engine to slow your speed. Brakes are much cheaper than clutches. I'm a rookie, but I do know that much. I believe that's where Ken was coming from...

 

To answer the original question, I make the decision based on RPMs further down the track. I try the downshift (assuming I don't think it is so high that it could damage the engine) and look at my RPMs at a pre-determined spot on the straight following the turn in question. If they are higher than they were without the downshift, I'll take it. If it isn't higher, or is VERY close, I won't do it to save the equipment.

Matt

 

A dyno plot of your motor will help determine the answer.

 

Agreed.

Once you turn in, as you rightly point out, you should be accelerating, not braking.

Now, to get back to the downshifting discussion...

 

No, it won't. A dyno plot tells you the optimal shift points. In the ITR, the fastest acceleration results from shifting at redline. But that doesn't answer the question about the trade-off between added acceleration in the lower gear vs additional time spent shifting down and up again.

 

I had this experience at Summit Pt T1. Going through it in 3rd was smoother to be sure, but waiting for the car to reach 6000rpm after exiting the turn felt like an eternity. So I tried taking it in second - there was a lot of power but I would reach the top of the gear while I still had the wheel turned. On the 2-3 shift, the car would skip off to the left a little once the clutch was released. It bugged me at first but I did realize it helped me track out to the kerb where I needed to be.

But, in most cases a more experienced driver would be carrying way more speed into the turn to begin with, and therefore wouldn't need to shift down. I rode with Will(ard) at VIR and this was basically confirmed. He downshifted a lot less than I did but was way faster.


[Modified by Ross, 12:23 PM 4/23/2002]

 

That says it all.


If you're going for time, on a Type R you should not be below 5.5K anywhere (6K if possible). A little over 5K in 2nd is ok on the track.. but you are still loosing some time to another car that can jump out of that turn better with more mid range power. You actually loose very little time upshifting if you do it quickly, while downshifting is done while braking anyway, so no matter if you need to do 3 downshifts or 0 downshifts while braking, it should not slow you down at all since you are in a braking zone to begin with. More shifting is harder on the equipment and motor, but coming out of a turn in a shorter gear at 7K-7.5K is ultimately faster than being stuck at 5.5K in a taller gear in a peaky motor such as ITRs and GSRs.

 

pick a reference point on the following straight to check your speed. One lap try it in 2nd gear, the next lap leave it in 3rd. What's your speed at the reference point. That's how you decide.

That's exactly what I do everytime at CMP, unless it's a time trial

 

If it's a corner that's between gears, try staying in the higher gear and focus on being smooth and carrying more speed through the corner.

The corner at Mid-Ohio that leads into Thunder Valley (can't remember the #) is a good example... 4th gear feels too low in revs but 3rd puts you at redline near the exit. After some practice the data showed that I picked up a LOT of time through that one corner by not downshifting.

Seat time in a low horsepower (ITC, etc.) car forces you to learn a lot about momentum. When you don't have much horsepower to begin with... the downshift doens't help you much!

 

While driving a Civic Si in the Grand-Am Cup race at California Speedway a few weeks ago, I faced the same dilemma on a couple of turns. In this case, since the engagement of VTEC made such a big difference in acceleration, downshifting into 2nd was the answer – even though I had to shift up at a point on the track that wasn’t the most comfortable. It felt faster (not always a sure sign of speed), I found it easier to keep up with traffic, and my lap times fell.

You’re right about downshifting in order to slow down – don’t. Use the brakes to slow the car, downshift to be in the correct gear to accelerate out of the turn.

 

Braking and turning is known as trail-braking, and as long as you know how to do it correctly you should. Use the brakes to slow the car, not the engine.

In regards to the original question, stay in the higher gear if you're unsure, but if you can manage it go for it (as someone else mentioned). Another thing to consider is where does this turn lead to? A long straight or another slow corner? If it's the former then there would be more to be gained from downshifting, and if it's the latter then it might be better to go with staying in 3rd and concentrating on keeping speed through the corners. Just make sure that you're in the right gear for the corner before the next straight.