Any hints regarding the speed range and gearing for CM at Lincoln?
Thanks,
Dick
CM85
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Any hints regarding the speed range and gearing for CM at Lincoln?
Thanks,
Dick
CM85
Dick,
I don't think anyone can give a solid answer because it comes down to personal preferences. Do you want to make 3rd gear your top gear or do you possibly want to sacrifice a bit but be able to stay in second.
I can't recall my top speed last year and my DL1 traces are lost somewhere. I think they may in my laptop. I'll take a look. But low 70s would be a very reasonable expectation for top speed in CM.
FYI, Babb and Johnson designing the courses this year.
Jim
Jim,
I'm concerned that with the current grip levels (tires and surface) that my "tall second gear (66 mph at 6800 rpm)" approach will hurt me on too many sites, especially Lincoln if I get there in a couple of years. Therefore, it may be time to really learn how to reliably shift between second and third. My transmission has the appropriate Taylor mods so it is just "me" that needs training/practice.:confused:
FYI the reason improved grip is relevant to me is that my favorite car setups tend to oversteer and it was pretty easy to get inside wheel spin exiting a corner . . . hence not much point in shorter gearing. I realize that with better grip, overall speeds will be up . . . unless the coures are tighter to compensate.
My current third gear (78 mph) would be fine for any fast straights with the 66 second but probably too tall if I run a shorter second and have to upshift more often.
Dick
CM 85
Bump!
Looking to change the gearing of the Mondiale... Currently we top out in fourth on a regular basis.
Last years Nationals courses were similar to what we typically have for courses in SoCal.
Top speeds? What's normal for a CM ford, try to gear for running second gear on most courses with occasional fast section in third? use all four gears?
Mk9. 10:31 Ring & Pinion. All speeds at 7000 rpm
1st: 13/37 53 mph
2nd: 15/36 63 mph
3rd: 17/35 73 mph
4th: 18/32 85 mph
Hopefully someone running the 9:31 R&P (or lower) will offer up their selections as I find the 10:31 really limits your choices.
I'm planning on the following with my 9:31, but we'll see what it is like once I put it in.
13:37 - 48 mph
17:34 - 68 mph
18:32 - 76 mph (and maybe a 19:32 instead?)
20:31 - 88 mph (I think this is what I'll end up with for 4th, and I don't think it will matter.)
Speeds are a 7,000 rpm.
I'm pretty sure that the 2nd currently in the car is a 16:36 and we're running out of 2nd gear everywhere. I'll find out for sure when I open the case for the first time here soon.
Andy
Thanks guys, now I need to get out to the trailer and see what R&P is in the car. Then what gear sets I have to work with.
The Mondiale has 9:31 R&P. Haven't opened up the gearbox to see what gears are in it.
Between what is already in the transmission and the five useful gears (16/36, 18/34, 18/32, 20/32, 20/31) in the spare parts box we should be able to get a good setup.
Good to see what you guys are running. I have 9/31 in the 90VD w/ an LD200 trani and I have 13/37, 16/35, 17/38. But I have yet to try it all out.
Mark
Does anybody set up the internals so that your 3rd-4th are the gears you actually would use? Launch in first, shift to "3rd" then the gates used are straight up/down.Quote:
Originally Posted by Dick R.
Assuming a 4 spd gearbox.Quote:
Originally Posted by Daryl DeArman
Why versus doing the same thing in 1st and 2nd? What do you do for fast straights?
Also, you would have a very weak 1st gear . . . even if the ratio would fit in the 3rd gear position of a Mk 9.
Dick
I'm thinking you need 3 gears; 1 to launch and 2 while at speed. The two used while at speed would be easiest if they were straight up/down in the gate position. Afterall you are looking for hundredths right?
Ah ha. :o That I understand. I think it really depends on the typical min/max corner/straight speed on your typical sites. Unfortunately (track racers please stop laughing . . . :D ) "we" don't get to test/practice/drive the course to determine the appropriate gearing for that day. Normally we don't even get to see a map except at major multi-day events like Nationals. At those events we certainly could use experience to optimize the gearing for one or both courses after walking the course the day before.Quote:
Originally Posted by Daryl DeArman
FYI I used to see many local courses which had 1st gear pivots and 90 + mph straights.
Dick
That 1-3 shift would kill you, much better off having the more natural & instinctive 2-3 and subsequent 3-2 downshift.Quote:
Originally Posted by Daryl DeArman
That 1st to 3 would kill you why? You need to do it once. vs. how many times you need to do the 2-3, 3-2 thing?
If you could have a dog leg 1st, ala an older Porshce, it might work, but w/ an integral first gear that is not an option. If you go w/ a slide on first in the location of second you'll be too tall and lose too much acceleration of the line, plus have a weak gear prone to breaking.Quote:
Originally Posted by Daryl DeArman
You have approx 45 seconds to do everything perfect in an auto-x run; to achieve this you must minimize driving errors. On today's national level courses you generally need three usable gears and many have gone 'short' and are using all four w/ a top speed in the mid-80's.
Got it. I was thinking integral 1st, who cares what you put in the position of 2nd, then 3rd and 4th would be the gears you actually utilize after launch, unaware that three or four gears are being utilized on national level courses.Quote:
Originally Posted by PCalhoun
Lots of options and lots of trade-offs. All of us who have been doing this a long time have sorted out what works for us. Use DA to see what is really happening in regard to longitudinal accel or throttle position and how long a shift REALLY takes. Where in a corner can you actually go to full throttle compared to when you will need to shift? Can you enter a corner as well if a down shift (one hand off the wheel) must be added to the process given our "shorter than F1" braking zones? Where on the typical autocross "not straight straights" will the upshift typically be needed (one hand off the wheel again)? Then try to pick gearing that optimizes the trade-offs. If you are so inclined you can even "do the math" to actually calculate the "ET" for different typical straight lengths, entry speeds, and gearing options. Just don't forget the coasting time during upshifts.
Dick
CM 85
Bringing this thread back, as I'm now thinking about gearing.Quote:
Originally Posted by Jim Garry
Jim, I ran my car a fair amount this weekend and, with a 15/36 second and unknown third, I was hitting the rev limiter early in short acceleration zones and kept wishing for a taller second. So, I'm considering my options...
With the torque characteristics of the motor in my car, which also has a tri-y header with what appear to be pretty long primaries, I'm kind of leaning towards a 17/34 second, but am concerned that I'll be out of luck on turnaround elements. Maybe 16/35 second and 18/34 third?
Also, what is the "right" rpm drop between gears?
I don't mind shifting, but my times were faster this weekend bumping the rev limiter more than I wanted than they were shifting...of course, I was using the clutch, being it was my first day in the car.
With time, you'll make those shifts faster.. PM me your email, and I'll send you a pretty useful excel gearing chart. Originally Calhoun's.
Thanks, Nick. Mark (Mervich) actually sent me the spreadsheet this morning. The biggest question I have is whether to go with a 16/35 second or 17/34. The 15/36 I have now, with a 54mph ceiling, is not working for me.
The 15/36 is very low. I tried it for awhile way back when. Not too useable. My memory these days is pretty bad but I'm pretty sure that the last few years I was using a gear between the two you are considering. I can look it up when I get home if you'd like.
< Also, what is the "right" rpm
< drop between gears?
IMHO, the RPM drop isn't such an important factor for Solo as compared to RR. Driveability should be the primary consideration. Upshifting takes more time that you may think. Leaving it in gear often improves times by a surprising amount. I used to think it didn't matter much because a Hewland can be shifted so smoothly it feels fast. But looking at the DL1 data I had showed me I was wrong. So gearing short may not be wise but YMMV.
And I agree that with a high second gear, turnarounds could be problematic. You may end up having to use 1st gear, which of course means an extra upshift where others aren't doing so.
Jim, I'd be interested in comparing notes... Using both maxQ, and the mph trace from the AIM, very rarely can I see where my shift points are. If I see a change in the slope, it's from a botched shift. Typically, I have to overlay my RPM trace to see..Quote:
Originally Posted by Jim Garry
I'm sure there's a loss of acceleration with making a shift. Has to be, I just wish I had better data showing me that time loss. I'd then like to calculate the acceleration loss from being in a taller gear, without losing the time shifting.
I remember someone at a grissom event walked over to my car, looking it over. Finally, he looked at me and asked. "where are the paddle shifters in this thing." I smiled, and pointed at the level. He responded, "there's no way your making those shifts as fast as I hear with that lever!" That particular event had a set of offsets just after the start. Flat, but with shifts up into 4th.
My car was set up for road racing when I purchased it. My former first gear is now my forth gear (85 MPH). First gear fixed (43 MPH). My second gear is pretty tall and all the courses we've driven on so far, seems to be sufficient. Right now I'm agreeing with Jim and want to limit shifting.
I've toyed with the idea of using placing my present forth gear in the third position and duplicating my second gear in the forth spot just in case we have to use third on a faster course. The shift back to second (forth) would be straight pull. For most autox courses, I'm planning on sizing second so that third is used in only rare cases. I could be wrong, but using my butt dyno, it seems the car has more pulled lower in the RPM range.
Of course my opinions should be taken for what they are.....given by a relative noob who hasn't yet dialed the car in.
> I'd then like to calculate the acceleration loss
> from being in a taller gear, without losing the
> time shifting.
Not everyone will agree with this but from my point of view, since so many autocross courses on the national level contain big sections of speed-maintenance, there isn't much accel to be lost. There's more time to be lost by having to shift.
> He responded, "there's no way your making those
> shifts as fast as I hear with that lever!" That
> particular event had a set of offsets just after the
> start. Flat, but with shifts up into 4th.
:)
Absolutely sounds like that. At one point some years back, I was using a 12:38 first, a 15:36 second, a 17:something third and a very short fourth. There was a very narrow airport site in eastern NY that forced a really, really tight 180 at the end of the runway. At this one event, it lead onto a pure straight. I probably could have left the car in second but I wanted to go thru the gears that day. Bang, bang, bang. And a course worker came in and asked if I had a sequential transmission. He was shocked when I pointed to the H pattern. But it's possible that had I left it in 2nd for the 180 and then shifted directly to fourth for the long straight, I might have been quicker to the next braking point. Can't prove it though.
My point though is that our Hewland shifts do sound awfully fast. I love the sound and feel of going thru the gears. That's why I was blown away when I saw the amount of time elapsed between gears. And my co-driver also had the identical time between shifts. This was over many events until I went to longer gears and quit shifting.
Another thing to take into consideration is that as the car gets better dialed in and the driver gets better, the gear needs get longer because now you're going thru the turns faster.
So...a couple of different ways to approach this question, I'm gathering.
I'm thinking I stick with what I have, for now, which will give me more opportunities to practice my shifting. I've been autocrossing since '05, all in cars where you basically grabbed second and stayed there, and when I did road race, it was in a Formula Vee, where you basically grabbed fourth and stayed there...well, a few third gear downshifts, but you get the idea...the only time I've done lots and lots of shifting w/o clutch was racing motorcycles and I don't think that skill is going to help much with this deal!
One data point:
I made one shift on each course at Solo Nationals last year, 1-2. My East Course times are proof that you don't need to rip through the gears to be quick. I used the same philosophy when I drove a B Stock S2000 (I went back to first less often than nearly everyone else), and it served me well there, too.
My final gearing for last season with the 9:31 final drive:
13:37
17:34
19:32 (didn't use)
4th... does it even matter?
I wouldn't go any taller than a 17:34 for second gear unless you want to shift back into first on occasion. I wouldn't got shorter than that unless you want to shift to third. East Course was about as big of a speed range as I think the car could handle in a single gear.
Andy
I'll know what gears are in it soon and then determine what to do. With the 15/36 second, it is entirely possible it has a 17/34 or 17/33 third. If that's the case, I can use third as the primary and have second for pin turns or turnaround elements, right? In which case, I need a 4th gear with about a 80mph ceiling for the occasional "high speed" situation, I guess...4 gear set up.
Looks like good advice Andy. :thumbsup:Quote:
Originally Posted by ahowe
Andy,Quote:
Originally Posted by ahowe
Great info (says the guy who uses a 17:34 second :D)
What were your approximate max revs in second?
Thanks,
Dick
Andy,
Great data, thanks. I am curious about your experience on last years Nationals courses. Did you find they had similar speed extremes? Did the east course have a higher max speed, and the west course a lower slow speed?
East was more open, but had two tight/slow places (well tight in a Mustang anyway). West was a slalom fest except for one spot it wasn't, and then it was pretty wide open (up the hill to the finish complex). We banged the rev limiter on the east course, and lugged one corner on the west.
Thanks!
Doug
P.S. - not that I have any intentions of changing anything on the car, but I am new and very curious.
P.P.S. - funny that those courses are still mostly locked into my head after 6 months.
Yeah...I can remember the courses at Lincoln clearly, too...mostly from the perspective of looking out the side windows, as Mark's STX car had a rear bar seizing in the bushings, leading to lots of "unintended slip angle" :eek:
So, on gearing, I guess my question is why not run the 17/34 as third? There is one additional upshift, but the thrust in gear equation might more than offset the loss of longitudinal acceleration on the 2-3 shift early in the run. Second gear, at a 15/36, could be the bail out option for turnarounds and other really tight stuff, but third would be the primary gear used.
That's why.Quote:
Originally Posted by mwood
You'll be giving away time to other drivers who don't have to make two shifts to get to the gear you're going to use. And you won't see any corners on a National course that will require you to downshift from a 17:34.
Last year's results at Lincoln seem to indicate the extra shift wasn't a bad trade off?
But, for all I know, it could have been mostly down to being able to run Kevin's crazy slalom intensive course in a short 2nd gear, going out, then grab a taller 3rd for the second half of the course, coming back...if you follow what I'm saying.
One data point is, basically, not to be relied on. But, it is still interesting...to me, anyhow!
On the West Course, the key was momentum. There was no high speed section or low speed section. At least when we drove it on Thursday. The surface was too squirmy. Ideally, I'd have had a slightly shorter second gear - 17:35 or 16:34 - to give me better acceleration everywhere on the course. This course also gave you no place to shift - it was slalom central. My result on this course was not gearing related... I sucked all by myself. My co-driver was substantially faster (but dirty).
The East Course had the wide speed range. The slows were slower and the fasts were faster. I actually raised the rev limit on the engine to make sure I didn't run out of revs coming into the bus stop. The limit was moved to 7200 and I'd guess I used 7000 of it, maybe 7100, at that one spot on the course.
Disadvantages: The slow speed corners (East's first turn around and series of 90's) would have benefited from a lower second gear, but the low revs made the car very drivable at corner exit. I knew I was giving up acceleration off of each corner, so I focused on smooth and making the most of what I had.
Advantages: Not shifting between gears made the back section of the East really easy to drive. It was a slow 90 into a flat out pair of lane changes. All I needed to do was steer. The fast 90 after that was in the fat part of my 2nd gear - I just rolled off at turn in and then back on and down the straight.
Andy
This has been very useful to me:
http://www.apexgarage.com/tech/gear_ratios.shtml
Attached "Gearing.xls" spreadsheet that I use to compare/contrast up to three different gearbox selections...
Quote:
Originally Posted by Jim Garry
Oh my,
This is what I've been talking about in the other thread. This is great to hear Thanks Jim.
Ben
Interesting to hear about CM gearing. In FM we were seeing very high 70's on the slalom course( west), and crossed the finish low 80's on the east.
What were you guys seeing for speeds?
With my 16/35 2nd(max 60mph) I have been bouncing off the rev limiter a bit more lately. Does this mean I am getting faster? Only at a couple of American AutoX Series events has the course been fast enough for 3rd. Maybe someday I will be fast enough to need a 17/34 2nd:)
Mark