TaylorSea4

Again, I feel compelled to chime in what Matt has already stated. I will not believe these inflated "fishin' tale" numbers unless I see them myself. Cyrus' car seems pretty hot, and his GPS claim of 176 sounds pretty honest. I KNOW how hot Red1's car is, and even though he roached his clutch, we figure he'll best the chipped car (also running The Mile last weekend) by at least 10mph (roughly 150-55 through the traps). Aero's DO come into play too. I can sit there and show you how an F-150 Lightning can hit an estimated 135 mph with its gearing or whatever, but talk about hitting a WALL. For the record, a Lightning was trapping at 118mph last weekend.

GRANTED, this is through the traps at only 1 mile, which does bring acceleration into the equation. The black chipped car hit the traps at 146 last weekend. Can it go faster. OR COURSE, but The Mile stresses getting there at much at the end result. And Brain said it best; all this with NO kids, curbs, mini-vans, cops, or dip**** drivers.

gilwong

Alot of top speed depends on gearing which is the limiting factor with the 951. Lots of cars with 350rwhp hitting 180 and 190 top speeds. Namely 993TT, 996TT, 996GT2, 996GT3, any current Ferrari. Now getting to 200, that's going to require some huge horsepower.

Diver944

On Sunday Oct 31st there are a whole bunch of guys in the UK trying to top 200mph down a 2 mile runway through a radar trap. 30 cars in total including modified GT2s, modified 996TT, 993TT, F40, TVR, Aston Martin, Lambourghini, Lotus, Maserati, Ultima. The last time they did it one Ruf Turbo hit 200mph exactly with quite a few others in the high 190s

Automotive Nirvana

Jeff F

Hi Guys:

I ran the green 951 at Texas Mile that Taylor was talking about. It ran 147 on Sun. (with my wife driving) while I drove the 928 at exactly same speed. From my old drag race days, it is all about the tires, as far as adjusting final drive ratio and top speed is concerned.

It was still accelerating, after barely shifting into fifth at 3/4 mile when going through traps.

At those speeds, it is also all about pushing air, and having the horsepower--not torque--to do it.

You can easily figure you theoretical top speed based on tire diameter, and a few simple calculations, based on rpm you think you can/should run.

Tire circumference, or rollout, is 2 x pie x r, or two times 3.1415926 times the radius of your tire. Do the math and the conversions, figure your final drive ratio in fifth gear, and you have your theoretical top speed at your theoretical or actual top rpm. For top speed runs, you can really choose your tires and you fine tune your final drive.

Here's the trick. You have to match your theoretical top speed to your peak horsepower--not torque--rpm to get top speed. For example, I was going through the traps at 5,250 rpm in 5th gear at 146. That is almost 1,000 rpm below peak horsepower for that car. I would have gone faster if I:

1. Had smaller diameter tires that put me closer to peak horsepower, or,

2. Had more power to allow me to rev higher toward peak horsepower.

-That's what I plan to do next time.

The guys that are going 180 at 7,250 rpm, I bet are past their peak horsepower. They are leaving speed on the table. You want to be at top speed at the rpm where you are making peak horsepower. You can adjust this significantly with tires. The guys making extreme power probably need gears.

Jeff

1996 951 2.8 (lots of extra stuff)
1997 928s4 (some extra stuff)
1992 968 cab-mostly stock and staying that way

TaylorSea4

Thanks for the "experienced" report, Jeff. Just outta curriosity, what color green IS your car? We had several amatuer discussions everytime you came by on course. Loved that exhaust, too, dude. See ya next time around when my bud's clutch is up to the job...

porshhhh951

Yeah top speed is all about hp not tq.... thanks for the much more technical side of things...I learned some stuff by your post.

oh and change your sig. Or do you have the only 96 model 951?lol. Not to mention the 97 928

BTW why don't you post on the turbo and turbo S board more often.

DDP

ok...so you are all doing this on stock brakes???

hosrom_951

Yes

jsonnen

Brembo 4-pots are stock...........whats the problem?

FSAEracer03

4 pots at all corners clamping 12" rotors... not too bad for stock, huh?

They're a lot better than you give them credit for.

Jeff F

Hi and Thanks Guys:

I read this board as much as I can, and am learning from you folks as I go. Being an old V8 racer, I am new to 951s and the world of forced induction (although I know my way around a nitrous bottle--those days are past).

Like on the 928 board, I try to post when I can offer something useful from my background and experience. Again, usually I just read and learn.

I am not a computer guy. Usually I am in the field, with a cell phone. My screen time is limited. Also, I am still learning Rennlist posting protocol--avatar, signature, etc.

A race like Texas Mile is really quite facinating. It is effectively two races in one. The first is the first quarter mile. You are really accelerating mass here. Torque and area under the curve (you dyno guys know this) really comes into play here. You really want to be going as fast as you can at the end of the first "race" to put you in good position for your second "race", the last 3/4 mile. Shift technique (especially with a turbo, you don't want it to unspool too much during delay), as well as shifting points is important. You want to rev to or near redline (depending on what yours is), even if it is past peak horsepower, because you will land closer to peak horsepower in the next gear--advantage. You can soft-start your car, it doesn't make much difference and none of us want to break them carelessly. The first "race" is about weight, the lighter the better.

The second "race" is all about horsepower and aerodynamics. Think about it. You have accelerated mass (your car) in only 1/4 mile to 110 to 125 mph. You now have 3/4 the race left to only increase 30, maybe 40 mph (for you extreme power guys). Things are happining fast, and ground is sucked up at an alarming rate. Aerodynamics. Mirrors folded in. Wipers removed in my case. (The day prior they were flapping on the windshield). Things like ride height, bottom pan, and even skinny tires help. Remember, wind resistance increases exponentially-squared--with speed. It takes serious, serious horsepower to go seriously fast. Good aerodynamics really help with this, even such detail as waxing the car.

My post is getting long. Will address exhaust and color to follow. Thanks again for all I am learning from you folks. I appreciate it.

Jeff F
1986 951 2.8 (lots of extra stuff)
1987 924S4 (some extra stuff)
1992 968 cab (mostly stock and staying that way)

Red1

Jeff is really spot-on about this. You want to have a clean 1/4 mile, to set you up effectively for the finish.

The pisser for me last weekend was the slipping clutch. The car was shaking like a Parkinson's patient in a hurricane as I'd cross the line. Since everything from tires/wheels/bearings front and rear are new, of course the only thing I hadn't done yet was the clutch. We'll be ready for another try at it next spring.

The 951 under normal circumstances will still be accelerating at the 1 mile mark. I still think I can improve the times we've managed as 951 representatives so far. I have all winter to spin wrenches in preparation for the next go at it.

It was nice meeting you Jeff, as well as Mr. Brooks. It was kind of funny he seemed to be as enamored of my car as I was of his.

Any Texas boys that haven't gone down to that really should go. The event is actually more fun that it might seem, the pits are full of cool modified cars, and the backroads coming home are downright twisty and a hoot to drive. I think Taylor would back me up on that.

theedge

I was running out of road pretty quick as you can imagine, so I might have been starting to lift off the throttle already when she took the pic lol.

Jeff F

Red & Taylor:

Pleasure to meet you guys too. As Andy and I are old ex-drag racers, we really appreciate that event, and your guys interest and representation in it.

Interestingly, Texas Mile isn't a drag race. There is no reaction time, or time at all, and start technique isn't all that important. Hence, you do not have to beat up your car. That is contrary to popular belief. Many Porsche guys say "I'm not going, I am not going to drag race my car." That is pure baloney. Andy has LOTS of circle track experience, and I have some as well. We both know that autocross, DE's and SCCA/PCA events are much harder on our cars than those such as Texas Mile. Brakes, Tires, oil starvation (mine was a past victim of a lunched motor due to #2 rod bearing at a PCA autocross).

We both loved your car, and thought you would smoke us easily. Andy has talked about moving up to a Turbo S. I am moving toward bringing mine back to that configuration. It was seriously fast at one time in racing form, and was downgraded for autocross use before I owned it. We could smell your clutch in line behind you at the start--and figured something was amiss. If not for that, you would have toasted us--both of us figured you at ~155.

Brakes. Yes stock, except for slotted rotors and pads from Paragon. Turbo brakes are awesome, and Turbo S (Like Red's) are Big Blacks, and are spectacular. I should know, I have a set on my S4, and they are responsible for bringing that beast down from speed in fine fashion with about 500 lbs. extra weight.

Back to tires: You can do so much tweaking with them. I moved from 275/40/17 on the 928 to 285/40/17, and gained diameter and rollout. It put my speedo dead on. I could have gone to 285/45 (or 50)/ 17 if I wanted more. Tire Rack.com has all the measurements on line. Obviously, you have to balance style, sidewall flex/cornering, fit, etc. in all of these compromise decisions.

We deserve a real Porsche and Rennlist showing at Texas Mile in April. Those folks try really hard, put on a superior event, and it would be a fine get-together.

Jeff F
1986 951 2.8 (++)
1987 928S4 (+)
1992 968 cab. (B&B)

Someone design me a new sig, and I'll take it. THX.

TaylorSea4

Jeff, at the Spring event we need to consolidate the Porsche's under 1 tent/canopy. Maybe even get a Texas Greaseslinger flag to fly, eh, Brian? Greaseslingers UNITE!

Yes the roads in and out are twisty. Brian and I caravanned out with his 2 buds in their GM F-bodies. He slowed for a 35mph turn to give us enough distance to ROMP on it behind the lead car, dove in on boost and proceeded to impress the crap outta me. We DROPPED his buddy in the 422 TA behind us, and I was truly spellbound by his car's ability to corner SO flat, so composed. Later, Brian showed my why you DON'T want to enter a corner OFF boost (neither flat OR composed).

Brian and Jeff got it right, though. I don't know WHY more guys don't show for this event. The cars are WAY cool, plus it's fun to laugh at the people who can't shift (BWAAAAAA- BWAAAAAAAAAAAAAAAA- buuuuu...) to save their lives. I REALLY expected to see some hot-**** 930 drivers, but I suppose they were too busy polishing their $50,000 ***** extensions (corner-balanced to make the drive to grocery store better, I suppose).