Driving Directions to El Mirage Dry Lake

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No, Greenwood kit was not allowed. If I had run a record speed with the greenwood kit - it would have been disallowed. i can run all I want with the kit - but it is not legal for records.

The car came with the kit - it just took me a while to find the time to remove it!

 

density altitude - much higher due to heat - on sunday at el mirwge which is 300 ft in elevation - the Density altitude started out about 4800 ft and was over 5800 ft at the end of the meet!

At Bonneville - altitude about 4200 - a little heat easily puts you over 7000 ft.

Next El Mirage is July 15th - i'll be looking for you!

Carl

 

Hey Kinky and Ken,
check this out some guy using an off the shelf cheap GPS unit as a poor mans data logger - you can see the route of his run and return - and a log of speed - second by second. I will do this from now on!

http://www.landracing.com/forum/inde...;topicseen#new

Carl

 

Kinkajou type el mirage lake rd into google maps and the get the satalite veiw......Big azzed grey spot.


My pretty much stock eng/bodied 92 6 spd has gone 150.... twice now actually and felt pretty damned good at speed... wasnt there very long (seemed like a minute... probly only20-30 seconds)..... just takes too long to get from 135ish to 150... and it seemed like forever for every mph over 147

Anyway the car felt stable, I did not detect front lift

I'd love to take it somewhere I didnt have to lift..*cough* legally.... I wont do it around here anymore. Too damned stupid...got more to lose now.

 

-- windtunnel tests showing about 150 lbs of lift at ? 120 mph?. --
Back calculating 150 lbs @ 120 mph, would give a CL (Lift Coef) = .21
That would calculate out to 234 lbs @ 150 mph, 337 lbs @ 180 mph, and 416 lbs @ 200 mph .... of front end lift.
Base front spring rate, for an 88, is 92.6 lbs/in @ the wheel.
Than front end lift in inches .6 @ 120mph, 1.3 @ 150mph, 1.8 @ 180 mph, and 2.25 inches @ 200 mph.
How far does it have to go up before the driver "feels" it?
Seams to me, Stock body - stock ride height, gets less stable at speed not more (like any vehicle with a positive lift coef).

Now stock body modified ride height and rake, is totally different story, I agree.
Sonny Parks, on the forum here, is running insane speeds with a stock body car, but he has the front so low I don't think he even runs a front spoiler.


Well, time to get up off my "recliner chair" .. and jockey off to bed

 

I'm converting to btuh from HP sapped by the tires. (Otherwise known as btu/hour.) Both are units of power, or energy per time. The tires cause drag loss mainly due to the compression cycling that goes on as it rotates with weight on it. This drag loss translate to heat which must be expelled. Bend a bic pen back and forth over and over quickly then feel the heat it puts off, it can be enough to burn your fingers.

The HP generated by the engine powers the car. Some is lost in the drivetrain (friction, heat), some in the tires (friction, heat), some lost to aero (friction, air movement, heat)

 

I don't use a 4.5 inch tire, but yes, it would be less.

It is never a fixed percentage, it varies based on RPM, fluid temperature, power output, etc.



MVMA data says 19.4 sq ft for the early C4. All the Cd's I've ever seen listed were .34, or .33

at 200 mph:

4640 rpm, 68 hp tire loss, 375 hp aero loss, 522 fwhp needed to overcome it and 15% drivetrain losses.

It's not a formula, but a simulation I developed in college. I used it to predict top speed, 1/4 mi times, and everything else using gear ratios, tires, aero, and a dyno curve. Also to optimize shift points.

 

Don't put words in my mouth. I said air under the car creates lift. Getting rid of it reduces lift. Increases downforce. Same thing, I won't argue semantics. It also improves the Cd by deflecting air away from all that crap, just like the fairing on a large semi truck, or a camper shell on a pickup. The increase in frontal area is minimal compared to the Cd and stability improvement. I don't know that you can accurately consider the space under the car as open area anyways... being that close to the ground causes deflected air to create more drag than it otherwise would.

You won't find many of them published, here's a quick google search:

Honda Insight = .25
Lexus LS sedan =.26
Audi A6 sedan = .28
Camry = .28
Nissan 350z = .29
07 Hyundai Entourage minivan = .31
05 Mazda MPV minivan = .34

And I didn't say anything about 20 yr old vans. They weren't designing for low Cd then. They were boxes.

Yes.

That hints at how big of an advantage they are. I bet jet engines aren't allowed either.

 

that's a good pic of my car.

i do have a factory front air dam on it (i didn't in the pic obviously) and the bottom of the center section is less than 1/2 an inch off the ground. I do have it nice and low. that is an easy way to limit the airflow under the car, and to improve the CD.

I've got about 900HP, and according to my calculations using the tire/wheel height, my gears, etc, I should be able to go about 217mph in a mile if i turn 7200rpm. if i turn higher rpm, which i should be able to if i can get there, i could go quite a bit faster... I just don't know if i have enough power and traction to do it in a mile.

see ya,
sonny

 

Sonny, if you can get me a dyno curve, I'd be happy to run your car through my sim to check 1/4 mile, 1 mile, top speed, shift points, etc.

 

YUP that sounds like the faa...

 

i appreciate the offer, however, i suspect that you would need a lot more info than just the dyno sheet that i don't have available... and i think there are too many variables to be able to actually simulate anything and try to be accurate...

 

If you had a dyno sheet I'd take you up on that challenge. Shift delays, clutch dumps, aero and tire losses, etc. I can do a 1/4 mi pass within 2 tenths or better.

 

One of the best things you can do to a C4 is eliminate the parachute in the back end...a rear diffuser sealing off the car from the passenger bowl to the rear bumper would do wonders.

Working on one now, but won't have it installed, or have any results until July.

That said, my currently stock-bodied car is quite stable over 150, even over the "hump" at Mosport (taken at 120-130). The car is lowered, however, which may help.

I'm also missing the front air dam due to a lawn mowing session, I'm sure that's not helping me as the air blasts directly into my front tires at speed.

 

scary fast ,
You are right - that whole spare tire area becomes a great big scoop. I just finished the fairing (or panning) of the whole area - I'll see if i can shoot you some photos.
Amazing - the engineer types keep insisting the front ends of these things will fly - and the applied guys - guys who actually go these speeds - don't seem to have any problems with front end lift!

How could that be - we all know engineers are always correct!

Thats the difference between engineers and scientists - engineers build based on their predictions - assuming they can calculate all variables.

Scientists in the other hand gather all the info they can find - make a prediction as to what will happen - then they actually bother to go out and test their prediction - they are not sure they know all the variables - so they test - and look at test results to reshape their predictions and to learn more.

Engineers don't need to do that - they know everything already!

Yah - I know - I'll go put on my Nomex - the genius engineers who reside here are loading up to come after me! Funny how an electrical engineer knows all there is to know about aerodynamics - without any real world experience! (thats allegorical - you can insert any kind of engineer you know into the "electrical" pretense!)

Carl "why can't I get my car to fly - all the engineers insist it will!" Johansson

 

Hey Sonny,
Why is your chute mounted up so high and away from the rear end? Do you know something I don't know? I put mine right on the licence plate holder, a couple of people thought it was too low and would have turbulance problems - but so far we have had perfect deployments with no tangling delays etc - so until I see an actual problem - or someone convinces me otherwise - I'm gunna leave it where it is!

Carl

 

Sounds like you have some issues with engineers ... to bad
You started a technical post and asked for input, and then start insulting people that don't respond the way you want?
I've seen your other posts, and you looked like a straight forward
guy doing some interesting things, so I don't get it....
If I knew this was going to be just another ground effects (and engineer) bashing post I wouldn't have bothered with it.

Sorry if I've bothered you somehow?
Next time I'll just keep moving on by .....

 

Sorry if I offended you - I appreciated your input. My issue is with People who "provide me input" that I know for a fact is incorrect!

Sometimes the numbers people run do not take into effect the whole package. I have run a C-3 for about 6 years now - in excess of 175 mph - guess what - no front end lift - if it's there, it doesn't show up in a loss of stability - a squirelly feeling, or any other way I could imagine the "front end lift" would show itself. In fact the car hunkers down and gets more stable at higher speeds.

I am getting the same results with the 2 C-4 's I run. They get more stable at the speeds where I have been warned about "front end lift".
And guess what, the 3 or 4 C-4's I know of in excess of 200 mph - all running completely stock body (except a big box on the hood) , at least 1 exceeding 255 mph - none of them report any - I repeat - any sign of front end lift.

I have had several people here in the forum claim to have run 150 or 160 on the open road and they claim that the front end got light on them. One of 3 things is happening in this case.
1. They are lying about the speed - but have heard the tired old dogma about front end lift - so they figure they better incorporate it into their ego inflating story!
2. They haven't figured out that at higher speeds you need to be very precise and tiny with steering inputs - otherwise the cars gunna start wallowing around and get scary!
3. Their car is completely unprepared for that task - in this case - they are risking their lives on something they know very little about - and have chosen to not prepare themselves or their cars in any significant way! These are often the knarly grizzly photos we see here every once in a while!

I know what your numbers say - I also know what the car actually does - so which should I choose to believe and act on? should I ignore experience and real life results because a theroretical number says different than actual results?

It's my life on the line - I take this very seriously!

My question was how would the kit affect speed - thats it - I already knew it would add 3.5 mph by removing the kit - because I had already done it. I was just seeing if anyone wanted to take a guess at it.

I guess if the shoe fits - and you choose to wear it - thats your choice!

Carl " still waiting for the big hitters to show up" Johanssonb

 

Sorry you didn't find my posts useful Carl. I suppose from now on I can either start pandering to you, or better yet just avoid wasting any more time in your threads altogether.


I especially like how you say someone that experienced lift must be lying to inflate their ego. I only see one ego inflating.