winders

Mark,

Waste of time for whom?? We are having nothing but good and informative discussions on Racer University. The discussions are very high level. If something does not make sense to someone, it gets challenged in a reasonable manner. It gets discussed without the "know it all attitude" you so commonly project. Even from people that probably do know it all!

At Racer University no one is just trying to win arguments. Actually, except where you were involved, there have been no arguments. The goal is to learn and understand. The discussions have been excellent.

I wholeheartedly recommend Racer University to anyone that wants to learn more about racing and high performance driving.

Maybe the best thing about Racer University is that the members can have a technical discussion without your sorry *** ruining it.

Scott

mark kibort

to anyone wanting truth. the high level disucssions had errors for which I was adding the corrections. they were fundamental errors, that I thougth was worth mentioning. I thought you were trying to learn and discuss? certainly didnt see that way considering the errors in your posts, and the fire from which you wrote back.

you made some good points in the "when to shift discussion", why dont we just try and discuss in a way that is not conflictive.

Here is a dyno sheet that describes the point of when to shift a particular engine based on gears spread and power curve shape. this is for a 996 stock, where VR was saying to shift 300rpm early. Sorry, if racer university doesnt want these kind of points brought up where a race can save 10-30 hp for a noteworthy period of time, then what good is it to anyone.

Scott, (winders) here is what even you had said on the "when to shift" thread before it got into a mess (that is the point ive been trying to make for years, yet is contradicted by VR and others that dont have the ability to articulate a come-back, other than "you are wong".

Here is what you said:

To quote some text from the web site I posted much earlier:

Shift to maximize engine POWER, not engine torque! This is *exactly* the same as saying "shift to maximize transmission output torque".

Again, this is only valid if you are trying to maximize acceleration. If you have other concerns, you may not want to maximize acceleration while accelerating.

Scott

KaiB

I like the "high level discussion" point made above.

This is not a high level discussion at all. Its actually very basic and should be simple enough for the casual (hey, kinda like me...) observer to understand.

Mark, you're correct. Your grammar sucks, your presentation sucks and your manners suck...but you're right. Stop fighting so hard, I've learned quite a bit reading you, as well as many others here.

Of course VR is right also - he's always right because Texans always are.

RickBetterley

Thank you for your PM (and sanity).

bobt993

I am only going to share this bit of data once and leave the rest up to those interested to do their own research. I refer to considered experts: Graham Templeman and Buddy Fey. Buddy Fey: "Fastest lap times come when longitudinal Gs immediately before and after a shift."

Two examples unfold depicting holding a gear too long ( to redline). and Shifting too early.

When gearing tightens towards the upper gears it is common for the shift points to lower below redline. (paraphrased for length)

Mark , I prefer to follow the advice of a Pro that is active with ALMS, Grand AM. Rick this will ultimately benefit your question.

Recently I applied some of this at local track where I had set a track record last year at 1:29.2 (but had run 28 flat in qualifying). My best result was a low 27 after two 20mins sessions on last years rubber. Again, I must be wrong or mistaken. I really give up at this point.

KaiB

While you are shifting to each gear you are certainly at less of a mech advantage, but the time lost in the power band of that gear has to be compared to the prior acceleration data before you decide to redline the prior gear.

Bob, would you please re-write this. I've read it until my little head hurts and think I understand exactly, but would like your clarification before I ask a dumbassed question.

mark kibort

Kai, you talk about my grammer and presentation??? this is my biggest problem of conversations on the web. ive said this many times, and Ill say it again. ALL of these conversations with a white board and a beer (or without a beer) would be over in about 3-4 mins. Bobs, comment is the type of comment that is so hard to understand. I think what he means, is what we (I) have been saying all along. you want to maximize hp, so that when you shift , you end up with as much or more hp post shift.

Ill take that as a complement an appologize for the grammer, spelling, etc and if you interpret manners, my excuse is only that I fight fire with fire. now, the only thing VR has going for him is that he is a texan!

Actually, a high level discussion is what we are doing. there is always a confusion with the term. High level usually means , like looking at something at 30,000feet. you dont get the details. Im not going into the details. high level of this discussion is the HP preseverance, gear spacing, and optization for a given track. I was trying to help with information tying all 3 together.

Thanks,

Mark

mark kibort

Bob,
You are interpreting what Fey is saying. I hate to say it, because you are twisting it to say more than I am. The point is, if you have a rising Hp curve, you WILL leave a lot of HP on the table if you shift before redline. Fey knows this and I hope anyone reading this as well. if you have a stock 993, you might be right and look no futher than the dyno sheets Ive posted to prove this point. IF YOU EVER have less HP than you could have, at ANY Point on the track at ANY speed, you will be accelerating slower. Fey knows this (i hope) and I believe Newton before YOU or Fey. trust me, is the LAW!

now you toss out times that you run. well I run 1:36 at laguna on used DOTs and a 20 year old car with 20 year old bushings , with 200 less hp and only 2 seconds less than Tommy Archer backed by a pro team in a new car. So what?? So we both know how to drive?? The point is, that proves nothing. just think how much faster you might be if you did push your car to the limit. Im not saying you are not, but based on your logic and interpetation of Feys comment, you might be leaving time on the table. However, with a 993 HP curve, you might be right.

Again, my only point is to show that there is a real easy way to optimize your HP and performance on the straight areas of the track. take your gear spacing as a % rpm drop, match it to the hp curve and shift at a point that maximizes power , PERIOD. mathematically, it equals the maximum torque and thrust force at the rear wheels. they are inextricably tied together. dont shoot the messenger here. Newton gave us the tools, im just telling you about one.
If you ever shift your car, and end up at a hp less than pre-shift, you will accelerate at a lesser rate. before you respond, just show me a situation where this isnt true. (is it at redline or before redline?? usually, redline, but you need to look at the gear spacing and HP curve to tell! )

by the way, just look at the graph I posted. if you shift early, you can lose near 30hp for a significant amount of time. its regardless of a close ration gear box as you quote Fey on in most cases where race engines have very peaky arcs near peak hp. what he is talking about, is what I mention with the 993 curves. with tight gear ratios and those particular HP curve shapes, yes short shifting can be benificial however, one aspect that needs to be looked at, is the time it take to shift (usually, .3 seconds). during a shift, not only is there a time element, but a deceleration. you always want to build in some extra RPM to increase HP available during any shift sequence.

bobt993

Not interpreting. Quotations are verbatim. The engineering papers are wordy and that is typical. Mark congrats you ran me off this thread. I need to start looking for somewhere else to learn and swap info.

winders

Bob,

I would actually love to have this discussion over on RU. I would like to learn more about using longitudinal Gs to determine shift points.

Scott

Larry Herman

Scott, the thread is there in the discussion forum. It is tagged "Determining the optimal shift points".

mark kibort

thats funny! The quotation might be verbatim, but there are condiitions that you have convieniently left out or not though about. Im just bringing up the point. If you find an example for this not to be true, please put it forward. Ive provided my example on the graph above. in fact, it proves Fey's point and mine. it proves it depends on how close the ratio is before it pays to short shift before redline. another thing, redline is a figure determined by a manufacturer. generally, its a guideline. Where Fey is wrong, is generallizing. On a climbing HP curve with no fall off, or little fall off, like the GT3 graphs I posted. those NEVER pay to shift early and I'M sure Fey would agree, without question! It's just sound math and physics to agree here.

Bob, you quoted from Fey below:

"Two examples unfold depicting holding a gear too long ( to redline). and Shifting too early.

When gearing tightens towards the upper gears it is common for the shift points to lower below redline. (paraphrased for length"
the word "common" in Fey's comment, doesnt need to be interpreted, its implied! if the HP curve dictates a short shift, its true, if it doesnt , its not. what I mean by that, is a climbing HP curve DOESNT warrent a short shift, PERIOD! a curve depicted by your stock 993 hp curve , would.

Scott, seriously, if you do discuss it in your RacerUniversity forum and come up with something other than what I have described. I would love to know if there are any points that would contradict what has been said so far. However, it seems you and I are on the same page on this one anyway, based on what I quoted you about earlier. one thing that might also be looked at, is not only matching pre and post shift HP levels, but something a little more complicated, that of the time spent at the different rpm ranges, as well as shift time. shift tiime alone, will force a later rpm shift.
"longitudinal Gs" ? All this is about maximizing thrust force at all speeds. if you have maxmimzed thrust force, you will maximize "longitudinal Gs". maximizing HP or thrust force, as you were quoted , creates the same net result as you said. Again, they are inextricably tied together.

Yes, and there were some "folks" that talked about the "Noise" created by the engine past max HP and to shift early to maximize acceleration down a straight. However that was quickly proved wrong by anaylsis of the HP curve that was based on a stock 996 ('02).

Its real simple. if you have more hp by leaving it in gear and redlining it, then what is available post shift, redline it. if it doensnt, find the RPM where HP pre shift matches post shift, and shift 100rpm higher to accont for shift times.
If there is any data or calcuation that contradicts this point, I think we all would to see it. (assuming a general arc path of HP , not sawtooth , jagged HP plot)

Larry Herman

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.

Veloce Raptor

Which is pretty much what I said from the beginning, Larry. Some motors just make noise at redline.

winders

Why would I do something completely stupid like that? So I could endure a 5000 word dissertation on how everyone else is wrong and you are right?

I am so glad I don't have to deal with you on RU!!

Scott