Your first statement is far from the truth... ive proved here, many things well beyond a shadow of a doubt, where many just don't want to believe what they have "seen" or thought they have seen. (i.e. times gained for certain mods, where the other variables were much more dominant and discounted)
If im wrong, im the first to concede. being proved wrong or not having all the answers is a good thing, because when you find them, you are smarter and can spread the word.

you said, im off by a "couple of inches" for the later DP tires. I said 26" for the GrAm tires , so your saying the DP tires are 28" and this means old GT tires are 27"? I believe that . I have a set of some WCGT tires I cant fit , as they are 315x680 and are in 27" range.

I agree with you, that there is a big value in getting the right gearing for the real fast tracks. (where speeds are above our California 140mph top speeds... sans cal speedway). but once you get the top speed right, you should be good down low without too much fuss. again, there are trade offs with gears especially since all straights are not the same length. it is complicated to asses the gains of a change, unless you have a way to analyze the hp optimized over an entire lap.
many club guys care more about the longevity of their engines, so that comes into play too.. (not always willing to run the engine near redline, where needed to maximize HP over a lap or for an entire race.)

Back to your "facts" If you are off a little on the diameter, and you are looking for top speed, wouldn't the larger diameter back down the RPM.. say you were redlining before, going lower in RPM would be probably still in the max hp range , (unless you had an engine where max HP equaled redline, then you are right) None the less, sure at these speeds, 1/2mile per hour based on gear optimization could be a big deal... my only retort to that would be that many club guys might not be dealing with that kind of speed and accuracy of gearing.

Now going to sebring or Daytona, yes I would agree you need to optimize the gearing to hit the top speeds. most can as for other tracks, they don't even get close to top speeds. at road America for example, with my HP, I was only able to get to 155mph and just touching the rev limiter 3 times a lap. however, with any more hp my gear box would be useless, so I would need a 2.75 vs the 2.2 rear end. it would change all the other ratios too , but like I mentioned the averaging of HP through the gears would generally work out for most all turns with little downside.

I guess my response was back to what you said to Scott (to get back on track) you said he has the wrong gears for his tracks because he has a slow upshift time . (which made little sense) this we both say is not due to his gear set up, but engine inertia and other characteristics, not gearing or his shifting ability.

 

I often post for the same way to open the discussion. If there are "some" that have BTDT, and youre right, it can save a lot of time. However, in most cases, some of the things Ive brought up there were not clear answers, but a lot of feed back through the discussion worked up to the right answers collectively.

 

Why does every single thread with this certain common denominator go this way?

 

Because someone posts a comment that drives it that way.
If people stop posting their beliefs as facts, these threads wouldn't diverge to side debates.
Let me summarize. the old gear boxes and engine's, as cool as they were in their day, have no comparison to today's' technology and cannot be shifted as fast as today's gear boxes and more modern technology.
it has to do with many factors, not relating to gear ratio matching to a track, nor, shifting abilities.

When GTgears wrote this, it started the ball rolling. people can post whatever they want, but when they do, and IF they are not right, they better expect further discussion. its all discussion dave, don't worry about it... its like you think all of these discussions have to be pure , in case a million years from now aliens discover this thread and will be judging the human race by it..... heres a bit of additional knowledge... it doesn't matter. its all just a bar discussion written on the internet.......... and, sometimes folks can learn a few things along the way.... that's all.

WHAT WAS SAID ORIGIANLLY by GTgears :

Quote:


Originally Posted by winders View Post

With a 915, that may be true for a downshift, but for an upshift, waiting for the synchro to do its job is what slows everything down....by several times. Unless, of course, you don't care about synchro life.
then GTgears said:
Sounds like your gear ratios aren't right for your engine.

 

Mark,
I told Scott privately yesterday afternoon that I was just giving him a hard time. You've taken a razz as a serious comment. Scott and I have discussed his gearing at length over the last couple of years. You say clubbers don't really get into this stuff but Scott is a perfect example that they do. He doesn't have the deep pockets of a pro team but he takes his GT class air cooled racer seriously. It may run the old 915 gearbox but he has optimized it as best he can for where he runs. Given how long and hard he personally has examined gearing I thought it was funny to suggest that maybe he messed it up. Humor doesn't always transfer via the internet.

 

It is actually not that difficult with a simple data acq system. If you have the RPM trace and either log gear position (or can remember it) you can calculate tractive effort and then iterate gearing to optimize acceleration potential.

 

Thanks, Matt!!

My gearbox is great and is full of your products. I suspect there is a correlation there! But I really do wish you would complete your G50 synchro conversion for 915 project and productize it. I'll even test it for you on the track and in races...for free!!

I do have to agree with you though that you can make an educated guess on gear setups, but you really don't know if it is right until you have run the car at the track in question in race conditions. You can't just plug the numbers into a computer and be sure you are getting it right. Getting the gears right is going to be more critical on some tracks than it is on others. Of course the type of engine makes a big difference too. Perfect gearing is going to be much more critical for a peaky 2 liter than it is for a torquey 3.6 liter.

Here is what I wrote that started much of this:

Leh pretty much proves my statement when you watch him driving an RSR with a balk ring transmission which I assume is a 915. His downshifts are significantly slower in the RSR. It is not surprising consider the 4 decades between the transmission designs.

Scott

 

Mark, this was not said with any animosity, but you did this very thing in the thread about steering, but were/are unable to see or accept it as such.

 

Well, ya know, someone has a lot of free time since they were relieved of their duties as Chief Engineer and Lead Technical Expert for Penske Racing

 

We-e-e-e-ll guess I /OP ought to take responsibility for asking some dumb Qs...Regrets offered all 'round compadres. Signing off now. Thx all for sharing thoughts and respectful discourse.

 

Sleep with one eye open, my friend. Oh, BTW, don't eat sushi in a shark tank.... jus sayin...

If you just want some good-humored banter, ask about optimizing tire pressures....

 

I was giving them the benefit of the doubt....its actualy very easy.. there are some that still cant understand the HP curve.
manual integration of the Hp curves, is pretty easy just by eyeballing it. watch some video and keep a stop watch handy and you can get 90% there

As I have taken mine as well. Ive been doing it for quite a bit longer, but remember seeing Scott when he first started showing up in his car, how focused he was. I admire anyone that is taking this stuff seriously and spending the time to raise their own bars continually .
if this was a private joke between you and him, I missed it sorry. I was defending his position.

accept what?? the anecdotal evidence?? most here don't even know what that means. again, ive been in sports a long time, and certainly long enough to know that when training folks, just because some old successful (driver, golfer, skier , etc etc) is good by doing things a way that is not conventional, it doesn't mean its ok and needs to be taught. any coach worth anything, knows this . So, that discussion was filled with testimonials of "greats" doing things in a way that is really not ok for 99% of beginners to be taught, or allowed to do. my opinion, and thats what the discussions are for.

and all of this is exactly right.... right up to the "peaky HP " which is correct for it being more sensitive to gear ratios on a high speed track. "torque" ? all assume you mean , "flatter" HP curve.

Yeah, and all the beliefs and in and about the use of Nitrogen .