Smogrunner

iTrader: (5)

Hey Shiv or Paul,
Could you expand on the Nurburbring stuff? Sounds really interesting, but maybe a little off topic. What was your time and where could I go to compare it to other times of similar cars?

metaphysical

iTrader: (3)

Well, I'm not saying I disagree or doubt you Paul (or Shiv, but your opinion doesn't matter ). I just have a hard time believing that there is one way to do this. Well, I guess we'll soon find out how your car does against Robi's and RRE's.

chronohunter

iTrader: (1)

I was there with BMW a couple of weeks ago with some BMW N.A. people two days of blissful (for those riding with me frightful) driving. The M3’s were defiantly tuned there they felt so at home at any speed. Did you know that the slowest corner there is 3rd gear! You are just flying everywhere. Good times

*edit: I just re re-read it and notice you asked for lap times. You can't actually do a complete lap at speed except for the "industry days" so we had to slow passing the pits. They do of course have a way of estimating laps. They thought I was quicker than what the BMW drivers do there which is an 8:22. I by no means am an expert there but the high speeds and jumping do fit my "adventurous " driving nature I would love to drive the shop car there and go for the record of 7:32 for a street car. I just want Shiv to Ride for a lap (Scream girlyman scream )

chronohunter

iTrader: (1)

Then like I suggested go forth and learn. We will obviously never convince you here. You need more of a knowledge base to visualize this stuff from some different sources. It's good that you question. Come back from the mountain top and tell us what you think. One last hint; you cant bend the laws of physics you can either ignore them (RRE) or use them (everyone else)

GT35REVO

I hear that, just like people who goto the track with a CRX and KILL vipers with over 800WHP. It's driver man 100%, I watched Peter of RealTime racing at NSXPO a few years ago take a 100% STOCK NSX and beat over 200 other NSXes with every mod made for the car, stock pads as well lolrof. Peter is a unreal driver I think.

chronohunter

iTrader: (1)

PD is my Guru. We used to work togeather with Skip Barber and I learned a lot from him. Tons of respect

GT35REVO

The best thing about him is he's funny. He also gave rides in the RealTime NSX, now that is a race car, but for 400k it should be lol. He runs hard springs, like 1000 in the front and 800 in the back I think.

chronohunter

iTrader: (1)

A very dry Sienfeld like sense of humor, very funny.

hagakure

iTrader: (2)

Shiv makes a good point here. Would antone here argue with Karl Malone or John Stockton about the most effective way to set screens or play proper defense? There is certainly a time to consider the source of any type of knowledge or mastery. This is one of them, in my opinion.

Percy

ez76

iTrader: (5)

Let's see if I have read this right so far.

There is some ideal line of least curvature around any given track. Any deviation from that line is "wasted" motion in a sense.

A car's ability to travel that line (or the best approximation to it given practical considerations) is limited by the lesser of effective front and rear grip.

So assuming the most efficient use of weight and friction for braking and acceleration, then any set-up that reduces grip at either end of the car, is by definition going to be slower, because it cannot navigate that line as fast as the same car set up with max. grip at both ends (it will have more "wasted" motion).

chronohunter

iTrader: (1)

We only drive maximum radius on very high speed corners for all others you want to do most of your cornering early to gain exit speed

Yes, but remember you can alter that grips proportioning (that's where the driver can make a difference)

exactly

siegelracing

I'm an engineer. Georgia Tech, the MIT (or Harvard) of the South. Acutally I believe Georgia Tech's mechanical engineering program always outranks Harvard's. Maybe not always Stanford or Cornell, but always Harvard. I don't have near the resume that Chrono does, but I own, and have read and re-read almost every driving book ever written. I quite literally have an entire bookcase of nothing but driving and vehicle dynamics books.

Not that I have lived in the written word, I also was a factory driver for a shifter kart team. Granted you don't have the shock set-up, but we traveled the country running in some of the most competitive events ever run in North America. Competitive as defined by 45 competitors covered by maybe 1.5 seconds in qualifying. Yes that means if you are 1.5 second off the leader's pace, you start (if you make the main) in 45th. My best run ever was after a "qualifying position based on when you registered" run from 69th to 7th in 11 laps. If the chain hadn't broken I would have caught at least 4th, but 62 passes in 11 laps was a blast and a half.

Anyway, I have been setting up, racing, driving, and instructing in cars for a while now, and I am looking at possibly 3 teams to work with as race engineer. It seems like Robi has done quite a bit of track work. But I, like Chrono have yet to see even an attempt at an explanation of how it would not be faster to utilitze trail braking.

I don't think that the point of Max front grip can be made too much. Almost every production based race car will do everything they can to get max fron grip, and then balance the rear to match. Robi, your question about the outside front is certainly valid. The VAST majority of students that I have are happy to try and drive "through" a push problem. They will let that outside front just cook. Like Chrono said, trail-braking adds download to that outer front, thereby increasing its grip CAPACITY, which at a given load means you are working the tires less.

The corner entry over-steer is blast of a way to drive. It's is undoubtably more fun than running a more "stuck" line, but it's not faster. I have driven plenty of vehicle that had corner entry oversteer. It's a blast, turn-in, flat the gas and counter-steer through the corner. Some were pretty fast, in fact I won a number of races with them, and they would sometimes show pretty even tire temps, but having the rear over the slip angle of peak grip CANNOT be the fastest way round.

I guess that's another point to make. A pnuematic tire has an interesting plot of slip angle versus grip. Grip increases with slip angle quite linearly to about 6 degrees (different for different tires). Then it starts to round off, then there is little hump from say 6.6 to 6.8, then it rolls into a quick drop. This is one of the things that seperates Michael Shumacher from the rest of the world. The best of the best operate entirely on that little hump. Plenty of people can play from 5.8 to 7.2, no problem, never too out of shape... BUT playing over the drop-off means 2 things; 1, you do not have as much grip as one the peak, therefore you CANNOT (physics here guys) be going as fast, 2, you are cooking your tires faster than the guy who is at the same grip level over on the lower side of slip angle.

Taken to extremes, the pitch it in, tail-out driving style is basically rallying. While again, probably the most fun you can have, and crazy quick on loose surfaces in a relatively unkown corner, it's just not faster on pavement. Even the rally guys will tell you, the more unsure of the corner they are they farther they pitch it, the better they know the corner, the less they have to kick the tail. This argument doesn't play directly to the trail-braking argument, but it's late here, and I'm tired

siegelracing

I get it now, y'all are all from out West, where it's early. Cool, when I get up tomorrow morning it'll be like 3 am for y'all. Yeah. Paul we need to get together some time. You should come out here next Thursday, I've got a new Legacy GT, 2 STi's, 2 EVO's, a Cayenne Turbo and a 911 TT for you to play with.

jj_008

iTrader: (8)

As a fellow mechanical engineer I also concur with Siegelracing and Chronohunter. BTW this is a great thread. All we need now is some hard data of a car trail braking and not trail braking. Maybe make some pretty graphs. Oh, do I love data acquisition. The numbers shall set you free!

robi

iTrader: (24)

Look at a sprint car, watch a tarmack rally, or open European rally cross. they back 'em in let the car rotate early (no brakes during the rotation phase) pick-up the throttle and use the Forward traction to pull the car into the apex while driving the car off the corner NOT sliding it (kind of like tying a ball to a string to get higher g-forces) Every event we have gone to is full of EVO's so our times are against other well driven and well set-up evos the only time we lost was to a big turbo with a pro driver driving (Damn you Scott!) We added the BR stage V and beat that EVO (but they had an ignition gremlin as did we thank goodness for murphy! theirs was worse..) and every other big turbo EVO we have had the chance to race on the same track the same day..and beat 5 big-turbo cars with the stock turbo, (SSC/SS time attack) flashed, with the AFC... Keep drawing your chalk board lines, gaze thoughtfully at your engineering degrees and continue confusing the innocent with Auto Cross 2nd gear smoke and mirrors...I just went over the datalogs @ streets of willow the TIGHTEST track we run and I drop below 60 mph 3 times for a total of 4.958 seconds on a 1:12 second lap..so all this "time I've been wasting".... ie not trail braking when entering slower corners, is contained with in 6% total lap time and in reality 1% total lap time (time I was under braking for these second gear "slow" corners) so I can get a 50% improvement (I'm good ;-) No? so that's 0.1 second... Man you guys go in for mental ************ (you can get more than this differential by pulling the passanger seat). PS every Big turbo evo we've tested against trail brakes and after 2 laps their times DROP by over 5% (so I guess I've still got 4% in the bag) on my in-car timing by which time they point me or John by to do to us as we have done to them...(Stay in our mirrors and "harrass" us) my times go back to 5% faster (well maybe a bit more) and they of the overheated front tire group disappear... yeah yeah I know they were all rank beginners (like Tarzan in the 460 hp XS engineering EVO at the Time attack what a beginner! me in my stock turbo Stage IV). Oh in the skyline Tarzan Kicked all us US guys collective BUTTs so I think he was without doubt the best driver there in a car he knows but the USDM EVOs are different from the JDM EVO's he drives over there.)