This came up with Michael and I were discussing how his MIata did at the Challenge this year. He may correct me but he's running a T5 (3.76 first?) with a 4.10 stock Miata rear. In autocross we had 23 inch tires. In the drags we ran 22 inch rears. For autocross both drivers said they had to switch to third which was unusual as they normally stayed in 2nd. In the drags I felt like I was burning through 1st before switching to 2nd.
So first question. Should a Challenge car be geared to say run the whole autocross course in 2nd? What speed range?
Second question. How do you get your gearing right for the drags. I know with the Q45 I wanted a final ratio of about 10:1 in first but I never could get that and ended up around 12:1. Is there a balance between shift times and ratios? In Michael's Miata I was hitting the traps right at redline in 4th. Is that what you aim for? Or aim for peak power in 4th?
I can't speak to drag gearing (not my area of expertise) but generally in autocross you aim to stay in 2nd all the time. Usually 60mph is a decent goal, but the Challenge autocross is purposely faster most years.
Drag is easy - you can just do some math and mess with ratios to see which combo ends up being faster. I made a javascript calc for this, but don't have hosting anymore. Happy to share if someone else has a spot to put it. You can do it in excel pretty easily though.
Autox is not as easy, but in my experience, mid 60s for 2nd is ideal. (I have never run a challnge course)
Balancing the two above - now that is real tricky.
Keep in mind for the drag race that an extra shift in a MT car can be .2 or .3 sec (or more) really easy. That's time you're not accelerating.
In reply to ProDarwin :
I have webhosing if you want to send it to me. My email is my name @ my name .com.
Robbie (Forum Supporter) said:
Keep in mind for the drag race that an extra shift in a MT car can be .2 or .3 sec (or more) really easy. That's time you're not accelerating.
If you suck at shifting, perhaps.
I'm not positive, but I was working the course this year while the MR2 kart was running, and I'm pretty sure Andy was shifting into 3rd before the end of the first segment (the long portion heading west). And he was one of the fastest auto-x'ers this year.
In reply to AngryCorvair (Forum Supporter) :
I think your older eyes missed the dot in front of the 2 and 3. I could easily see a shift taking 2/10ths of a second. I remember playing with stop watches when I was young and just seeing how fast I could hit the button twice to start and stop it. I could get faster than 2/10ths but not much. Shift would take longer.
In reply to captdownshift (Forum Supporter) :
Using that I think there's no way to avoid third in my mental build so might as well go shorter rear end and make 3rd work for the whole course.
AngryCorvair (Forum Supporter) said:
Robbie (Forum Supporter) said:
Keep in mind for the drag race that an extra shift in a MT car can be .2 or .3 sec (or more) really easy. That's time you're not accelerating.
If you suck at shifting, perhaps.
I can tell you that F-Dat completes a shift in 62 ms. I'll bet you a beer I can shift 4 times (the entire 1/4 mile) in less time than it takes you to crack one off in monzora.
Robbie (Forum Supporter) said:
AngryCorvair (Forum Supporter) said:
Robbie (Forum Supporter) said:
Keep in mind for the drag race that an extra shift in a MT car can be .2 or .3 sec (or more) really easy. That's time you're not accelerating.
If you suck at shifting, perhaps.
I can tell you that F-Dat completes a shift in 62 ms. I'll bet you a beer I can shift 4 times (the entire 1/4 mile) in less time than it takes you to crack one off in monzora.
You've got yourself a bet!
Usually low 60s is the fastest a normal autocross course will hit in 2nd. Sometimes the challenge course can be a little more open. Out of probably 100 autocross events in a Miata I've needed to shift to 3rd at about 2 events. Even then it was faster to bounce it off the limiter instead of shifting twice.
Drag racing there is a reason a lot of guys run a power glide or TH400, shifting isn't moving you forward.
Locally i run the car in third gear. Launch in second usually so i only have to shift once. Third in this car tops close to 70, fourth is mid 90s mph.
Honestly, first is more or less useless....
When I ran my Miata in 2017 I ran through first gear very quickly on the drag strip and that was with the stock rear and transmission. It's geared for 140 HP to feel good on the street and the extra power just runs you through the gear that much quicker. The clutch was suspect so I never did try a 2nd gear launch. I probably should have, at least on the final run. The autocross was twistier that year and it could run the whole course in 2nd. Not a lot you can do about it.
In reply to Stampie (FS) :
Were you running "my" drag slicks? If so, what ET?
In reply to DeadSkunk (Warren) :
I think they came from Robbie and it did 14.274 @ 94.85.
Stampie (FS) said:
In reply to ProDarwin :
I have webhosing if you want to send it to me. My email is my name @ my name .com.
I lied, I can't find it :(
I could re-make it in Excel if there is interest. I think I even did it or something similar for Duster's Miata before.
In reply to Stampie (FS) :
That's over 4/10ths quicker than I went. Cool. The car seems to have worked well.
In reply to DeadSkunk (Warren) :
It did. It's an awesome Miata.
I try and design te autocross course to be as close to what you might see at a national-level SCCA Solo event as possible. With that size lot, that means the courses will stay shorter time wise, because to cram a 60-second course on that lot would require it to be tight and choppy, and ain't no one like that mess.
So using typical national SCCA design standards, I shoot for slowest corners in the high 30s to low 40s, fastest straights in the high 60s for the fastest cars.
A LOT of cars these days are using 3rd gear in autocrosses. A good portion of the hot-hatch contingent, as well as ND Miatas, tops out at or below 60 in 2nd gear. So third gear, or riding the limiter, is fairly common for modern cars. The Civic Type R we had at the event was on the limiter for a good 2-3 seconds on the opening straight on this year's course.
So, back to the original question. When I have the choice—not limited by rules or lack of parts availability—I shoot for a 68-70mph 2nd gear, with good acceleration as low as 35mph. Given the choice, I'll ride the rev limiter at 67 rather than bog at 34, since your average speed will be higher if you can erase that lower speed quicker.
But that's not always easy for peaky cars without much torque. In those cases I think you have to start looking at maximizing acceleration from like 40-55, and if you know you're going to ride the limiter for a while, short shift. So in otherwords, if you know you're going to be geared to low to use 2nd everywhere, lean in to using third and spec for that.
JG Pasterjak said:
I try and design te autocross course to be as close to what you might see at a national-level SCCA Solo event as possible. With that size lot, that means the courses will stay shorter time wise, because to cram a 60-second course on that lot would require it to be tight and choppy, and ain't no one like that mess.
So using typical national SCCA design standards, I shoot for slowest corners in the high 30s to low 40s, fastest straights in the high 60s for the fastest cars.
A LOT of cars these days are using 3rd gear in autocrosses. A good portion of the hot-hatch contingent, as well as ND Miatas, tops out at or below 60 in 2nd gear. So third gear, or riding the limiter, is fairly common for modern cars. The Civic Type R we had at the event was on the limiter for a good 2-3 seconds on the opening straight on this year's course.
So, back to the original question. When I have the choice—not limited by rules or lack of parts availability—I shoot for a 68-70mph 2nd gear, with good acceleration as low as 35mph. Given the choice, I'll ride the rev limiter at 67 rather than bog at 34, since your average speed will be higher if you can erase that lower speed quicker.
But that's not always easy for peaky cars without much torque. In those cases I think you have to start looking at maximizing acceleration from like 40-55, and if you know you're going to ride the limiter for a while, short shift. So in otherwords, if you know you're going to be geared to low to use 2nd everywhere, lean in to using third and spec for that.
Can you tell us what the CTR ran? I was out working the course when it did a few laps, and I wasn't quite close enough to see the time board.
If I have to wait for the challenge issue, that's cool too.
