993 gear ratio advice
05-02-2011, 01:48 PM
#46
Rennlist Member
Hey, Scott, you don't have to deal with him here either. I just put him on Ignore. Makes things so much easier. You still see his nonsense when someone quotes him in a response, but that is easy to deal with.
05-02-2011, 01:55 PM
#47
I will probably do that. I did it before, but curiosity got the best of me and I just had to see what crazy stuff he was posting. It's kind of like watching a train wreck. You want to turn away but you just can't.....
Scott
05-02-2011, 02:36 PM
#48
Rennlist Member
like VR, you never seem to post any factual information. its tough to discuss anything with you. I made a point. Yet, all i have got back from anyone close to a fact in disagreement is a quote, misinterpreted by Bob from a knowledgable source. Bottom line, power curves are just an easy way and very accurate way to find shift points, if you know the curve and know the gear spacing. (straight line acceleration, again! not to add any variables that VR jumps to when he is proven wrong....... like.........."oh, i meant, in the middle of a shift, ahh, when i cant shift at redline, and .... ah,... the track is wet and fulll throtttle will upset the balance......and....".. you know that kind of stuff.
Nothing more nothing less. Yet no one will be able to discount this easy shortcut to find shift points based on this simple technique. If you can, which I dont believe you will because from your quote, you already posted you agree with me by what you wrote, just write it here and give an example where this technique doesnt work.
05-02-2011, 02:46 PM
#51
Rennlist Member
)Now, what you just stated clearly and concisely is 100% correct in my book. Everything depends on the output of the motor, and the spacing of the gears. The HP in most stock motors falls off well before redline, but a long ratio box forces you to "wind it up" because of the significant drop in RPMs (and HP) after the shift. If you have a short gear box with a small drop in RPMs, it is entirely possible to shift before redline and still stay at a similar hp in the next gear. Yes, you can calculate it all out, or you can just prove it with longitudinal G measurements.
my point was there is no need to prove it with longitudinal g measurements, because the HP curve will indicate the exact same thing. this is not that common, even with a close ratio gear box (Not short , but close ratio is what you meant, i bet) its possible, yes, but it takes a curve like you describe to make a short shift pay any dividends. usuallly, these would be a portion of bone stock engines. most race engines, probably not. again, easy to prove and see.
05-02-2011, 03:34 PM
#52
Nordschleife Master
Rick,
What you have there in gearing is a common budget approach for the G50/20 that I am not particularly fond of. What they have done is worked around your fixed 2nd gear ratio (which is on the shaft and unchangeable) and reused what was your stock 3rd gear in the 4th position. Then they plugged in replacement 3rd, 5th and 6th gears from there as new replacement gears. It makes for the funky RPM drops that Bill Verburg has higlighted with his charts.
In a perfect world, you would have a 993 Cup shaft where you can change second gear and make it an 80mph gear like others have suggested. But you can't. So the solution is generally to shorten up 3rd even a bit more than what you currently have in there. You put in something like a 1.65 or even down to 1.70 so that you are minimizing the number of times you are shifting below 3rd and crossing out of the 3-4 shift axis and into 2nd. 2nd ends up only being used on the one or two slowest corners on the track, otherwise you spend most of your time on the 3-4 axis and going back and forth between those two gears.
And that stock 3rd 1.407 gear in 4th, is still technically too tall of a gear ratio and can be shortened up by several positions as well. Probably 1.429 is what I would look at doing there.
Your 5th and 6th gears are a touch shorter than I would usually want to see on a 993 like yours, but gears are expensive, and if you follow the suggestions of bobt993 with the slightly larger tire and slightly higher redline, then you can probably get away without altering them. On this particular gearbox, you best gains in lap times and acceleration are going to be found in changing out those 3rd and 4th gears. HP and drag don't allow your vehicle much more than another 10mph straightaway top speed on all but the longest tracks. I'm guessing that whomever put that box together either had an engine that revved upward of 8000rpm or just assumed they'd never run their car at somewhere like Mosport or VIR.
And on that topic, 3 and 4 are the high wear gears anyways. You spend more time in 3rd and 4th than most anything else and when they get the box apart they are the gears most likely to be showing significant tooth wear, especially that short 1.632 3rd gear. For anything we make that is 1.632 or shorter in 3rd, we put a 50 hour motorsports life on it. I know that sounds really short, but we're really conversative and we also really only count that as actual "race" hours. So, if you spend a weekend with 3 hours of practice time, 30-45 minutes of qualifying, two 30 minute spring races and one 1 hour enduro, I would call that 2 1/2 hours of race life, even though you physically ran it twice that many hours. So for some people it's easier to just call them 100 hour gears. But the shorter the 3rd gear gets, and it starts to get down to 19 or 20 teeth on the idler, they get worked hard and wear fast.
Just some food for thought withouth getting bogged in that other mess. I've got no comments on the rest of that side conversation.
What you have there in gearing is a common budget approach for the G50/20 that I am not particularly fond of. What they have done is worked around your fixed 2nd gear ratio (which is on the shaft and unchangeable) and reused what was your stock 3rd gear in the 4th position. Then they plugged in replacement 3rd, 5th and 6th gears from there as new replacement gears. It makes for the funky RPM drops that Bill Verburg has higlighted with his charts.
In a perfect world, you would have a 993 Cup shaft where you can change second gear and make it an 80mph gear like others have suggested. But you can't. So the solution is generally to shorten up 3rd even a bit more than what you currently have in there. You put in something like a 1.65 or even down to 1.70 so that you are minimizing the number of times you are shifting below 3rd and crossing out of the 3-4 shift axis and into 2nd. 2nd ends up only being used on the one or two slowest corners on the track, otherwise you spend most of your time on the 3-4 axis and going back and forth between those two gears.
And that stock 3rd 1.407 gear in 4th, is still technically too tall of a gear ratio and can be shortened up by several positions as well. Probably 1.429 is what I would look at doing there.
Your 5th and 6th gears are a touch shorter than I would usually want to see on a 993 like yours, but gears are expensive, and if you follow the suggestions of bobt993 with the slightly larger tire and slightly higher redline, then you can probably get away without altering them. On this particular gearbox, you best gains in lap times and acceleration are going to be found in changing out those 3rd and 4th gears. HP and drag don't allow your vehicle much more than another 10mph straightaway top speed on all but the longest tracks. I'm guessing that whomever put that box together either had an engine that revved upward of 8000rpm or just assumed they'd never run their car at somewhere like Mosport or VIR.
And on that topic, 3 and 4 are the high wear gears anyways. You spend more time in 3rd and 4th than most anything else and when they get the box apart they are the gears most likely to be showing significant tooth wear, especially that short 1.632 3rd gear. For anything we make that is 1.632 or shorter in 3rd, we put a 50 hour motorsports life on it. I know that sounds really short, but we're really conversative and we also really only count that as actual "race" hours. So, if you spend a weekend with 3 hours of practice time, 30-45 minutes of qualifying, two 30 minute spring races and one 1 hour enduro, I would call that 2 1/2 hours of race life, even though you physically ran it twice that many hours. So for some people it's easier to just call them 100 hour gears. But the shorter the 3rd gear gets, and it starts to get down to 19 or 20 teeth on the idler, they get worked hard and wear fast.
Just some food for thought withouth getting bogged in that other mess. I've got no comments on the rest of that side conversation.
05-02-2011, 03:34 PM
#53
Lifetime Rennlist Member
Since RacerUniversity was brought into this discussion, I need to clarify a few things.
Kibort said it is just like Rennlist and he had a trial membership. Neither is particularly true. RacerU does use forum software but anyone who looks at the 'forums' can quickly see that virtually all of those areas are NOT discussion forums, they are read-only 'Classrooms'. Our model is to present material as short courses and we have a single discussion area to discuss those courses and closely related topics. As far as paying for the same thing that is here, that is nonsense and Kibort never had access to even see what we fully offered. Paid membership is to get access to the higher level courses as well as the course discussion area after the preview (the only thing Kibort got to see of the member areas was a preview of course discussions).
We also have a coaching area (iCoach), that Kibort never had access to, so he is fully unqualified to pass judgment on that area too.
Our small membership fee gives access to GradSchool level courses and course discussion.
As to behavior, we are focused on education. We have some guidelines on behavior so that we can all learn and will not tolerate people who are committed to disrupting the process for others. Mark K, and a few others, were told very politely, even before we activated their accounts, that certain behaviors that we had seen on other boards we not appropriate for RacerU and they would not get the normal warning escalation in those areas.
To the credit of all but one person, they fully bought into the model of RacerU and gladly adhered to what we were building - they understood that we were education focused and not trying to build a general community like Rennlist.
Mark K did not and was the first to receive a Meatball Flag (our warning) for posting the same thing 3 times in the same thread and even quoting himself. He did not change his behavior to match our expectations (and last time I checked, he was not paying for the hosting, development or any other part of RacerU so we get to set the rules). He is the only person to have been banned from RacerU and while he is free to claim a lack of 'freedom of speech' etc, I am free to respond when he misrepresents what RacerU consists of.
As far as Kibort's vast knowledge being lost on RacerUniversity because we are closed minded, I will simply point out some of the credentials of our faculty and users:
F1 Starts, dominance of Indy Lights, F3 and other pro racing. Multiple people who won the British FF championship. ALMS prototype and GT experience, GrandAm, IMSA, etc, etc, etc. Multiple SCCA National champions.
Coaches who are currently chief instructors of well recognized racing schools, coaches who have earned their livings for many years and even coached a former WDC, professional race engineers, professional race car designers, pioneers in the use of simulators for driver training, pioneers in the use of data for driver development and much more. These coaches, race engineers and designers have led teams to professional wins, amateur wins, and general education about driving and the cars we drive.
Somehow, I think we can muddle along without Kibort's expertise.
RacerUniversity is very different than Rennlist or other discussion forums because we are NOT a discussion forum. We feel that our existence enhances places like Rennlist and I plan on remaining a participant in both places.
Kibort said it is just like Rennlist and he had a trial membership. Neither is particularly true. RacerU does use forum software but anyone who looks at the 'forums' can quickly see that virtually all of those areas are NOT discussion forums, they are read-only 'Classrooms'. Our model is to present material as short courses and we have a single discussion area to discuss those courses and closely related topics. As far as paying for the same thing that is here, that is nonsense and Kibort never had access to even see what we fully offered. Paid membership is to get access to the higher level courses as well as the course discussion area after the preview (the only thing Kibort got to see of the member areas was a preview of course discussions).
We also have a coaching area (iCoach), that Kibort never had access to, so he is fully unqualified to pass judgment on that area too.
Our small membership fee gives access to GradSchool level courses and course discussion.
As to behavior, we are focused on education. We have some guidelines on behavior so that we can all learn and will not tolerate people who are committed to disrupting the process for others. Mark K, and a few others, were told very politely, even before we activated their accounts, that certain behaviors that we had seen on other boards we not appropriate for RacerU and they would not get the normal warning escalation in those areas.
To the credit of all but one person, they fully bought into the model of RacerU and gladly adhered to what we were building - they understood that we were education focused and not trying to build a general community like Rennlist.
Mark K did not and was the first to receive a Meatball Flag (our warning) for posting the same thing 3 times in the same thread and even quoting himself. He did not change his behavior to match our expectations (and last time I checked, he was not paying for the hosting, development or any other part of RacerU so we get to set the rules). He is the only person to have been banned from RacerU and while he is free to claim a lack of 'freedom of speech' etc, I am free to respond when he misrepresents what RacerU consists of.
As far as Kibort's vast knowledge being lost on RacerUniversity because we are closed minded, I will simply point out some of the credentials of our faculty and users:
F1 Starts, dominance of Indy Lights, F3 and other pro racing. Multiple people who won the British FF championship. ALMS prototype and GT experience, GrandAm, IMSA, etc, etc, etc. Multiple SCCA National champions.
Coaches who are currently chief instructors of well recognized racing schools, coaches who have earned their livings for many years and even coached a former WDC, professional race engineers, professional race car designers, pioneers in the use of simulators for driver training, pioneers in the use of data for driver development and much more. These coaches, race engineers and designers have led teams to professional wins, amateur wins, and general education about driving and the cars we drive.
Somehow, I think we can muddle along without Kibort's expertise.
RacerUniversity is very different than Rennlist or other discussion forums because we are NOT a discussion forum. We feel that our existence enhances places like Rennlist and I plan on remaining a participant in both places.
05-02-2011, 04:53 PM
#54
Rennlist Member
Right on the money, Sunday.
05-02-2011, 05:26 PM
#56
Rennlist Member
Tell Bob Rouleau.
05-02-2011, 06:24 PM
#57
Rick, taking from Matt's suggestions here's a ~140mph stack. I didn't make any attempt to chose from std gearsets and just plugged in some ratios. If this is close to what you are looking for we can look into gearsets that are actually available.
05-02-2011, 07:10 PM
#58
Nordschleife Master
Bill,
What I was susggesting was using the 285/30/18 R6's mentioned earlier in the thread for a larger rolling diameter, and keeping his existing 5th and 6th. (1.227 and 1.063). Even without a raised redline it gets him to just shy of 137mph, and if he bumps it 200rpm to 7000, he's over 140. I just don't think the problems in how this box is stacked right now reside in 5th and 6th. The issue gears are 3rd and 4th.
What I was susggesting was using the 285/30/18 R6's mentioned earlier in the thread for a larger rolling diameter, and keeping his existing 5th and 6th. (1.227 and 1.063). Even without a raised redline it gets him to just shy of 137mph, and if he bumps it 200rpm to 7000, he's over 140. I just don't think the problems in how this box is stacked right now reside in 5th and 6th. The issue gears are 3rd and 4th.
05-02-2011, 07:28 PM
#59
Bill,
What I was susggesting was using the 285/30/18 R6's mentioned earlier in the thread for a larger rolling diameter, and keeping his existing 5th and 6th. (1.227 and 1.063). Even without a raised redline it gets him to just shy of 137mph, and if he bumps it 200rpm to 7000, he's over 140. I just don't think the problems in how this box is stacked right now reside in 5th and 6th. The issue gears are 3rd and 4th.
What I was susggesting was using the 285/30/18 R6's mentioned earlier in the thread for a larger rolling diameter, and keeping his existing 5th and 6th. (1.227 and 1.063). Even without a raised redline it gets him to just shy of 137mph, and if he bumps it 200rpm to 7000, he's over 140. I just don't think the problems in how this box is stacked right now reside in 5th and 6th. The issue gears are 3rd and 4th.
the 265/35x18 I used in all the above charts is speced @25.3 but has an actual loaded rolling height of ~24.6
I don't have the loaded rolling height data for Hoosiers, Sometime this summer when I switch over I'll be able to get that info.
I was under the impression that Rick was looking for a little more top end.
I'm sure that he is much faster than me but in my car w/ 265/35x18 MPSC and a g50/30 I run out of 4th just before the end of the esses(awkward place to shift to 5) and run out of 3rd just before T6(laces) so I shift from 5 to 4 for the inner loop and leave it in 4 till the short chute from T6 to T7(if it wasn't for that awkward shift point just before 6 I'd use 3rd), everything else is comfortably in 3 and 4
993s just don't respond well to extra rpm, even my 3.8RS engine is much better if I shift ~ 6600 or so and even lower at times