r_towle
Mar 15 2003, 05:24 PM
So,
I want to stop shifting so much at the Autocross.
What gears would you all recommend???
Rich
ChrisReale
Mar 15 2003, 06:15 PM
Not a professional answer (ill leave that to the "others"), but a friend of mine has a taller 3rd gear. While I spend about 95% at high rpm's in second, he used 3rd almost the whole way through. I think it also depends on the course layout. Just bring like 3 tranny's and bolt them on as neeeded
Somebody else will have a better idea, but thats a start
Zeke
Mar 15 2003, 06:42 PM
In that case, Chris, I think you're friend has a shorter 3rd gear (closer to 2nd than yours), otherwise he'd be traveling a lot faster thatn you on the course. I hear a shorter 3rd gear is the hot ticket. Maybe 4th as well leaving 5th for the freeway. On my race car, I've shortened 3rd, 4th and 5th. We'll see how it works.
J P Stein
Mar 15 2003, 07:57 PM
I would like an A or B first. We are pretty much SOL with 2nd. My only solution is to either shift to 3rd or put in the 7300 rpm chip.....that's good for about 30 feet more.
I don't have any problem with my 3rd (stock 4 banger gearbox). It doesn't drop the motor off the cam, so... what the hell.
You may be able to tell that I seldom get into 3rd at out local AXs. I agree, tho, it does complicate things......but not enuff for a 904 mainshaft.
Maybe larger diameter rear tires?
ChrisReale
Mar 15 2003, 08:50 PM
Zeke, he IS going faster than me, by about ten f'in seconds! He runs GTU. I could have it backwards though!
J P Stein
Mar 15 2003, 09:13 PM
QUOTE(ChrisReale @ Mar 15 2003, 06:50 PM)
Zeke, he IS going faster than me, by about ten f'in seconds! He runs GTU. I could have it backwards though!
Well.......comparing your stockish set up against (as I understand your class structure) a GTU car is a bit absurd......then there is the driver (no offense
). What's the seat time comparo?
ChrisReale
Mar 15 2003, 09:22 PM
we dont run together, we just shoot the shit before, during and after. I have a total of five runs under my belt, he has a few years under his.... :cursor:
Dave Cawdrey
Mar 15 2003, 09:26 PM
So, 5 or 10 minutes, huh chris
ChrisFoley
Mar 15 2003, 09:27 PM
Try building an engine that has a higher redline and a wider torque band instead.
If the rules allow alternate gears, they must allow engine mods too, no?
OTOH, a taller first gear, as J.P. mentioned will get you at least through the first turn before shifting.
ChrisReale
Mar 15 2003, 09:35 PM
He has a 1.7L with big bore, 22mm torsion bars, different tranny, 22mm sway bar, 225 rear springs, and hoosiers.
I have a stock 2.0L with stock bars, 22mm swaybar 180# rear springs and F'in all season yokohamas!
Im going to steo up to 21 or 22mm torsions, stick with my tire size. That way I can stay in P1.
It may take me a few years and a feew rebuilt butts (sitting on seat without cushion so my fat head and helmet can fit) but I am young and determined and greedy, so one of these days....
Im curoius what Brad has to say about racing trannys.
J P Stein
Mar 15 2003, 10:11 PM
QUOTE(ChrisReale @ Mar 15 2003, 07:22 PM)
we dont run together, we just shoot the shit before, during and after. I have a total of five runs under my belt, he has a few years under his.... :cursor:
He,he.....thas what I figured.
3-4 seconds from the car.....the rest is operator error
NOBODY is competive the first time out (write, if you're an exception)....or the first year or 2. Track guys come out with a big Johnson and....oops....the excuses flow like beer....."I got lost" is a good one "My car ain't set up for this" is another. I've used them both (tho I'm not a track guy). Everybody nods and says "Sure"... which really means "This guy won't be back".
My latest one is "I'm workin' on it".....which really means "I'm learning to do this". I'll hang with that for a while.
The only way to measure your progress is to pick a consistently fast guy and start working at improving your times vs his. Get the car set up and leave it alone for several events(or the whole season). Then it's just driver.
Chris:
You're right.
1st is good for about 60-80 feet....tain't enuff, sometimes. When that is the case, I've been short shifting as soon as the rear tires hook up.....just to get it done with. I haven't come up with a good launch sequence other than to abuse the trans. One of these days there's gonna big this big BANG :toilet: and I'll be needing a new 901.
ChrisReale
Mar 16 2003, 03:03 AM
QUOTE(J P Stein @ Mar 15 2003, 08:11 PM)
. Get the car set up and leave it alone for several events(or the whole season).
err...umm...cant comprehend this statement... system overload....malfunction...... :toilet:
Dave Cawdrey
Mar 16 2003, 03:38 AM
QUOTE(ChrisReale @ Mar 16 2003, 01:03 AM)
QUOTE(J P Stein @ Mar 15 2003, 08:11 PM)
. Get the car set up and leave it alone for several events(or the whole season).
err...umm...cant comprehend this statement... system overload....malfunction...... :toilet:
Its like tellin' a crack head to not smoke all summer
Dave_Darling
Mar 16 2003, 12:43 PM
QUOTE(J P Stein @ Mar 15 2003, 08:11 PM)
NOBODY is competive the first time out (write, if you're an exception)....or the first year or 2.
Locally, Scott Winders showed up to the Zone 7 AutoX school (same one I attended) and by the beginning of the next season, was an instructor and a consistent top-10 finisher.
One or two of the people B has built cars for have wound up very competitive in their first year.
The common denominator, I think, is motorcycle racing. They didn't road race or autoX, but the fine art of balancing a motorcycle on the ragged edge of control teaches you some very good reflexes and skills. And a good mindset.
...Hmm, so in a way those weren't 1st-year drivers, were they??
As for the original question--
The easiest way to change your gearing is to change your tire sizes. Taller tires will make your gearing taller, shorter tires will make your gearing shorter. Taller gears will lose you some torque but you won't have to shift as often; shorter gears will gain you some torque but you will have to shift more frequently.
If I were you, I'd just drive the car.
--DD
Brad Roberts
Mar 16 2003, 01:39 PM
I'll answer in more detail later:
Take off in second and bog the motor. Keep both hands on the wheel for the first turn.
B
r_towle
Mar 16 2003, 04:13 PM
Ok,
I'll be more descriptive.
I short shift to second ASAP. first in the 914 is only good till 13 mph, so basically useless.
the problem I have is that the courses are set up to keep the 911 drivers coming back, so they are fast courses.
This means that I must redline second, or shift to third. I would like a second gear that goes a little faster, or a second/ third gear combo, where I can short shift to third and keep it there through a 180, and back down a long straightaway.
I have listened to another 914 in our club, and he can stay in third an alot slower than I can...
I was just wondering if there is a standard swap to accomplish this.
So to recap,
Option A is a second gear that is for higher speed (not sure if that is taller or shorter)
Option B a second/ third set that are closer to each other to enable staying in third at slower speed.
BTW, I am really asking if this can be done, and what do I need to buy???
Thanx
Rich
TimT
Mar 16 2003, 04:27 PM
Option A is a toughy,
second gear is part of the input shaft. so to change second you have to get a 904 input shaft, and a taller second gear. Porsche did make a few different ratio input shafts so getting another is an option, but they are expensive too.
Option B is the way to go. find out what gears you have in the gearbox. then "build" your ideal gear box. Often you can shift gears around use 4th as 5th,3rd as 4th, and buy a shorter 3rd.
The 4th and 5ths in hat come with the cars are comprimises, and usuallu much to tall.
If you have a Z 5th gear, that is good for about 145 at 700rpm, but you will never see that in a ax, and you wont use it on most racetracks either.
Another option is to keep the stock fifth ( so you can still drive on the freeway and keep the rpms cool), throw away the existing fourth, move 3rd to 4th, and get a shorter 3rd..
you have lots of options just depends if you want to make a dedicated ax car, or a car that will still see some street use..
<<<
mskala
Mar 16 2003, 04:35 PM
Rich,
Some people were saying it in a roundabout way in their
messages; You can't change second gear in a 901 trans.
It is part of the mainshaft. To change it, you have to buy
the '904 mainshaft', which allows changing 2nd gear ratios.
And I assume you mean 31mph in first, I can do about that.
I can only get to 52mph in second with 205/50 tires and a
6300 redline.
Mark S.
'70 914-6
J P Stein
Mar 16 2003, 05:56 PM
I watched a 914 w/alloy Buick at the last AX.
He did 2nd gear launches. I figure he has about (maybe more ) the same torque than ulf...he claims about the same hp. I was not impressed.
In a heads up drag race, I would put a bus length on him using 1st with my car. When the trans is nice and warm, I can bang off 2nd pretty quick. I short shift (when necessary) to get both hands on the wheel before the first turn.
Mark:
52 mph @6300?
Humm, what's the link to CDs gear chart? I wanna do some figuring on my car.
ChrisFoley
Mar 16 2003, 06:10 PM
Mark's numbers closely match what my speed graph tells me for 23 inch tall tires.
J P Stein
Mar 16 2003, 06:52 PM
I wasn't doubting him, just a bit surprised.
I was doing some calcumulating and came up with about the same thing. I was going faster than I thought.
7300 rpms with 23.5 inch dia tires in second comes out to a bit over 60 mph.....38 in 1st. I've been known to.....ahem... bounce off the limiter while trying out a new course. I need one of them shift light thingys.....a big RED mofo.
Bleyseng
Mar 16 2003, 06:53 PM
Chris, you must be talking about Jason or Chris...can't remember who drives the white 914 or the blue 914.
For Bremerton the shorter tires are great! Drop down to 205x50's and you will see what I mean. I have put switching 3rd gear on the list when I go thru my extra tranny but that isn't happening soon.
I agree with DD to just bring and run what you have instead of changing the car all the time. Seat time will let you learn how to make the car faster. Later on you can improve the car to how you want it to drive.
If you watch Chris and Jason they both drive very smooth and effortless and don't seem to be going fast at all until the time is posted! They beat alot of 911 with twice the hp all the time.
I'll be there this Saturday even if it rains.....probably will too!
Geoff
ChrisReale
Mar 16 2003, 07:02 PM
Yup, its Chris. He is actually my girlfriends parents neighbor. Small world...well at least in West Seattle
Bleyseng
Mar 16 2003, 08:08 PM
Ahh the blue car is nice, very fast too. The story he tells is his grandfather setup/built it.
What size tires are you running?
Geoff
ChrisReale
Mar 16 2003, 08:28 PM
This season Im just gonna beat the shit out of the Yoko's I have on. 195-60-15. Id like to find a set of Mahle's so I could mount dome 205'50's on. Prolly Kuhmo Victo's. Yea, his grandfather was the one who had it, and I believe he and his dad rebuilt the engine
Brad Roberts
Mar 16 2003, 08:36 PM
I have a wicked Excel gearchart that shows shift points and lists all the 901 available gearsets. If anybody would like me to put it on the server..I would be more than happy too. You can plug in any RPM and any ratio to "achieve" what you want.
B
TimT
Mar 16 2003, 09:11 PM
Brad do you have the excel sheet from Stomski? or another one? I have 2 different excell apps for 901 gears, and was going to offer them up to the site.
( I developed neither, just would have to credit the authors)
Brad Roberts
Mar 16 2003, 09:17 PM
The one I have is from a friend of mine who raced a GT2 914 in SCCA. He is a computer engineer (David Ferguson) I was getting tired of doing all the math on my own and voiced this to him.. he told me he had a sheet and that I could share it since he sold the car and all the parts.
B
TimT
Mar 16 2003, 09:23 PM
Yea ferguson wrote the excel app I got from stomskis site. a link to a gear calculator would be cool.... it doesnt take up much server space either..
Brad get me a icon or gif I can use from my site.. Ill post a link to here
campbellcj
Mar 16 2003, 10:01 PM
Count me in for the spreadsheet
If my budget ever recovers from all the brutality in the last year, I will dive into the trans (LSD, 904 mainshaft, gears, cooling mods)
Brad Roberts
Mar 16 2003, 10:07 PM
Chris,
I' have a 901 I can sell you. I'm going to a WEVO 915 before summer. Its the one I built last year for the tube car using a new Guard LSD (80%) It has 4 races on it with a mild 3.0 in front of it.
Tim,
You can use the logo on the front page of the website:
Brad Roberts
Mar 16 2003, 10:11 PM
Oh.. email me the Ferguson gearcal... I have it on a computer at the shop that is turned off right now.
B
campbellcj
Mar 16 2003, 10:15 PM
QUOTE(Brad Roberts @ Mar 16 2003, 08:07 PM)
I have a 901 I can sell you. I'm going to a WEVO 915 before summer. Its the one I built last year for the tube car using a new Guard LSD (80%) It has 4 races on it with a mild 3.0 in front of it.
Let me know when it becomes available. I still haven't gotten the six in the car and the trans is not gonna happen until after that. Too many friggen bills in my life lately. Damn job and finances always get in the way of the important stuff...
Brad Roberts
Mar 16 2003, 10:21 PM
I didnt figure you where in a hurry. I'll even gear it for your engine. It should be close right now.
B
campbellcj
Mar 17 2003, 12:28 AM
Yeah but the big question is, will I keep driving the car mainly at the "short" tracks like Streets of Willow or partial Buttonwillow, or the longer/faster ones like Willow? Seems like gearing would be pretty different. I don't even know about the NorCal tracks yet; haven't ventured up there (soon though.)
Mike T
Mar 17 2003, 08:53 PM
Here's my setup in my green car.
weight =1776 lbs
engine = Chevy 2.8 V6 approx 190 hp, 180 torque
tires = 23" Goodyear slicks
transaxle is internally stock except for 3rd gear, it's a close ratio(shorter) 1.41:1 I got by using a stock .071 5th gear set and switching their positions on the shafts where the drive becomes the driven gear. I've been using it this way for 3 seasons and it works great. Speeds in 2nd and 3rd at 7k 58mph and 77mph Good for most local autocrosses. It's actually like having a gearbox with a choice of two 2nd gears.
I can launch in 2nd and if the course warrants it, shift up to 3rd and just leave it. You don't want to shift too much on course, wastes time.
I learned about this trick on the old dgi.net Renegade forum. I remember some of you from there. I think. Did one of you tell me about this 5th/3rd gear switch?
Mike T
Brad Roberts
Mar 17 2003, 10:27 PM
I didnt tell you, but we call this gear flip "KA" in the industry since they never actually made that ratio. This is THE cheapest way to get a shorter third.
I'll start a new thread.... for the downloadable gears stuff I have.
B
Lawrence
Mar 18 2003, 09:17 AM
Yeah.. post it, please. I'd certainly be interested.
-Rusty
porsche735
Mar 18 2003, 07:19 PM
The trick is thus:
Stock trans is:
1st 3.09=A
2nd 1.89=F 39% delta from 1st
3rd 1.26=N 33% delta from 2nd
4th 0.93=V 27% delta from 3rd
5th 0.71=ZD 23% delta from 4th
Do this:
1st 3.09=A
2nd 1.89=F 39% delta from 1st
3rd 1.41=KA 25% delta from 2nd (swapped 5th)
4th 1.08=R 23% delta from 3rd (swap 4th around)
5th 0.79=Z 26% delta from 4th (swapped 3rd)
This gives you a beautifully spaced gearbox (once you get out of 1st)
Do it, it's great....
Chris Kolstad
1973 914 2.0L (bummer stock ratios in my class, BP)
Brad Roberts
Mar 18 2003, 07:46 PM
Chris,
how did the time trial go ??
B
mskala
Mar 18 2003, 10:09 PM
QUOTE(porsche735 @ Mar 18 2003, 08:19 PM)
Stock trans is:
1st 3.09=A
2nd 1.89=F 39% delta from 1st
3rd 1.26=N 33% delta from 2nd
4th 0.93=V 27% delta from 3rd
5th 0.71=ZD 23% delta from 4th
Except if you have a -6 trans, then
Stock 6:
1st 3.09=A
2nd 1.78=GA 42% delta from 1st
3rd 1.22=O 31% delta from 2nd
4th 0.93=V 24% delta from 3rd
5th 0.76=ZA 18% delta from 4th
same final drive 4.43
If I calculated correctly
Mark S.
'70 914-6
porsche735
Mar 19 2003, 02:06 PM
Brad,
The Time Trial and HSDS went great. The weather actually cooperated with us. Friday was 3 sessions dry and 1 session wet (funny watching the newbies spin like crazy after getting fast after 3 sessions).
Saturday was basically dry. Sunday was really wet in the morning. I had fun, and I am not kidding, passing EVERY car in the red group. And that's on bald Kumhos (we corded them prior to the time trial). It's nice to have an equalizer for our low horsepower cars. The weatehr dried up after the first session and it was great. We started to get sprinkles around time trial time, so they caled them off and went to practice instead. We went once more until we really had no tread left and exposed about a 6 inch patch of cord. You know, running on corded tires is a lot like running in the rain. We were still putting down 2:19's on corded tires.
So, no times, but a great weekend....
chris
TimT
Mar 19 2003, 03:46 PM
FWIW I have AFKQV in my 911's box. My 914 has shorter gears dunno which though, someday Ill open the box up and find out.
campbellcj
Mar 19 2003, 04:07 PM
There are too many Chris's on this board...
I guess I will just have to start going by my middle name:
JOHN
r_towle
Mar 19 2003, 05:56 PM
I like the sounds of this KA route.
So, what do I buy for this.....and where!!!
I am not clear on swappping fifth??
Please explain...
Thanx
Rich
Bleyseng
Mar 19 2003, 07:17 PM
We know who you are Campbell whether it's Chris or John or somethingelse....
Geoff
Mike T
Mar 19 2003, 08:33 PM
QUOTE(r_towle @ Mar 19 2003, 03:56 PM)
I like the sounds of this KA route.
So, what do I buy for this.....and where!!!
I am not clear on swappping fifth??
Please explain...
Thanx
Rich
I used the 5th gear right out of the same trans. A friend did it for me. Another local 914er. We used 5th to replace 3rd and stuck the old 3rd, reversed, in the 5th gear spot. 3rd was now 1.409:1 and 5th was 0.793:1. Since I never see 5th gear in this car it was just expedient to do it that way. Works good, is cheap to do. I like it.
Mike T.
porsche735
Mar 19 2003, 09:24 PM
Rich,
As I said, no gears to buy. All you do is move 3rd to 5th and swap the pinion and drive gears. Flip 4th pinion and drive gears and use the old 5th in the 3rd location swapping the pinion and drive gears. It is really very easy to do. I have a brand new transmission that I have done this to if there are any takers...
Chris
Brad Roberts
Mar 19 2003, 09:35 PM
I normally use the terms (Drive and Driven gears) this normally makes it a little clearer for people to understand. I say Drive gear and they can figure out that is the input shaft gear. Driven being the pinion shaft gear.
B
Brad Roberts
Mar 19 2003, 10:52 PM
Richard,
We flip 5th gear to make a new shorter 3rd gear. Think of fifth as a overdrive gear. Now flip it (make the drive gear of the two a driven gear) This now makes a underdrive for 3rd. You physically take the driven gear and put it on the input shaft making it the new 3rd drive gear.
Got it ??
B
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