OK guys,
we are getting ready to run my brothers C-3 at Bonneville in September (world of speed) taking a crack at 200 mph.

In the mean time We will be using my C-4 to let people become members of the 130 or 150 mph club (don't roll your eyes - over 90 % of the people who try 130 fail - for various reasons).

The C-4 makes the 130 mph club easily - 1 mile standing start - on the salt (estimates are you loose 10 % to the salt - your wheels have to be turning at over 140 mph to time out over 130). So far , 7 Johanssons and 3 others have made that in the C-4!

The question is - will the C-4 have what it takes to make 150.
this is a 2 mile runup with the speed taken after the 2 miles.

I need some guys with better math skills and formulas that I have.

225 X 50 X 16 tires, 3.07 rear end

I know with my gearing I can be running 4500 RPM in OD (0.68) and make it - but if I have to downshift to 4th (1:1) i'll need 6500 RPM (I think that may be on the edge of hurting the motor)

as I recall - the frontal area is 0.34. i am running a ZZ4 (rated at 355 HP) bit it is aspirated by the stock TPI.

So what do I need to make it? or are we wasting our time - i don't want a bunch of people to put up money to make the run if the cars not capable - I'm thinking I may be caught in a gearing conundrum ( can't even spell that word!)

Carl Johansson

 

When the 84 came out, it was supposed to do 150 in stock form. I once had my 92 vert to 160 or at least the digital speedo was bouncing between 159/160. This was on a freeway and I had about a 1.5 mile run from a 70MPH start.

ZR-1's were capable of speeds approaching 175 with the 375HP motor. The body shape or drag coefficient should not be a issue if you have anything close to 350HP on tap on asphalt. The 89 and later C4's with the manual tranny reached their top speeds in 5th gear; there was not enough power in the stock motor to use 6th for a top speed.

Given the percentage loss on the salt, you may need more mods to the motor to hit 150. Are you running street tires or slicks made for the salt flats? You might try a taller and narrower tire. From pics I have seen of cars running at Bonneville, the tires appear to be pretty narrow and much taller than stock sizes. That cuts the final drive ratio down so it will require more HP to go the same speed.

L98 motors just can't make power above 5000RPM in stock form. The intake design is more for low end torque and the runners effectively limit airflow at higher engine speeds. Chances are you would do better with a carb setup and a good intake manifold with sufficient airflow into the carb. Or going to a Superram setup would be a big improvement as would headers and a free-flowing exhaust.

 

Never been to one of those mph club runs. Do they let you use nitrous? If so you may want to consider. Can't say I've ever done it but 130+ comes real quick.

 

when my '94 was completely stock and with the 3:07 gears I went 155mph after only having it for a week and it still had a lil left but I got scared and let off. Everytime I tried to go faster I seem to let off at the same mph

 

While I appreciate the input guys - I need someone who can do the calculation on frontal area and horsepower needed. This is all about air resisitance - a very large % of the HP will go to move the air - 150 is a completely different animal thatn 130.

ignoreing wind and traction lost to salt - it apears to be easy - get it up to 4500 RPM - shove it into OD - and make the mark!

Fortunately it isn't that easy - go look at the USFRA webpage they have a listing of people that have made 130 and 150 - and 150 is pretty short. 130 is very short too - I wish they had stats as to how many tried as compared to those that suceeded!

So I need someone who can give me info about how much HP is needed - considering 0.34 frontal area.

BTW - the car is very capable of hitting 150 - the question is - can it do it on the salt - with traction loss - a 4500 ft elevation (actually an advantage) and a density altitude that often exceeds 8000 ft .

carl Johansson

 

every bodys vette here will make the 130 club - I originally did it with an 86 with iron heads, no OD on the 4+3 and 145,000 miles on the original engine.

No nitrous allowed - heres a link to the rules etc
http://www.saltflats.com/I30%20Club.html

You ought to come out and give it a try!

 

Carl, didn't we do this math a few years ago? If you can find the old topic I can work backwards. At the time didn't you have a L98 car with a broken 4+3? I think the math worked out to just over 130... I guess the jump to the ZZ4 would help...

 

Carl, don't know if this will help you much but I hit 162mph in the mile (standing start) with 3.07 gears, 275-40zr17 tires and 345 rwhp. That was on asphalt, but that was also a one mile standing start. The car was still accelerating, and I wish I had another mile to work with. Would love to come out to Bonneville sometime.

BTW, all but the first run I shifted into OD, but on the first I know I hit 150mph in 5th, which is 1:1 in my Richmond 6 speed.

Good luck!
Dan

 

4500 rpm with 3.07 and .67~.68 od with those tires will get you to about 170.

but your acceleration will be junk in od. Like 0.04g instead of 0.60g in 1st (or more usefull, 0.17 in 4th minus od).

You certainly will have the HP to do it, but the question will be how much do you want to rev the engine up to?

 

Sorry I can't help.
I just wanted to wish you luck, hope you hit your mark. Let us know how you make out, sounds like it would be a great outing.

 

Carl -

I'm assuming that you have enough horsepower to do the job, as the LT1 Vette's were supposedly able to run about 160 - 165 with a 300 HP engine. Since you have an engine with more HP than an LT1, then you should be OK.

Now, to your other question ...

These are the forumulas you need:

Velocity = (60*pi*Tire_Diameter*RPM)/(63360*Trans_Ratio*Rear_Ratio)

RPM = (63360*Trans_Ratio*Rear_Ratio*Velocity)/(60*pi*Tire_Diameter)

pi is approximately equal to 3.1416

I also used 25" as your tire diameter. You should actually measure the tire, and this calculation ignores tire diameter increase with increases in velocity (and it may not matter on the salt anyway due to the 10% slippage)

If you assume a 10% slippage, then you need to be going an indicated 165 MPH to just cross 150 MPH. An indicated 165 MPH translates to just over 6800 RPM in third (1:1), and just over 4800 RPM in OD (0.68:1).

What I can't answer is whether you have enough distance in the run to get the engine to that speed. We'd have to know more details about the HP/torque curve of your engine, and then take into account the increasing drag on the car as you accelerate up to max speed.

I hope what I provided at least gives you some help!

Steven

 

Found this.

http://www.miata.net/sport/Physics/06-Speed.html

http://www.miata.net/sport/Physics/

 

 

Ah, that's the ticket.

I found the old excel sheet and played around some. I was confused because I wasn't using time at all; yeah it turns out time isn't a factor when you're trying to run a certain speed in a limited distance.

The old answer was 130 mph (err, 145 RWmph) in 5075 feet.

The new answer is 150 mph (again, 165 RWmph) in 10483 feet.

So, there's a good chance you would have made it with your old car. I suspect the ZZ4 engine doesn't have much more torque than your L98, but it has more RPM range (which is the same as more HP or more importantly more time in each gear).

Now I was using 0.354 for frontal area, so .34 would be even better.

I was also using the conservative 4500 RPM shift point. If you bump that up to 5000 it'll get you up to speed that much faster. Well, as anyone in the drag race section can attest, there's an argument that you'll trap the same speed no matter what gear/gears you start and proceed through; but what that argument doesn't take into consideration is drag, because you'll taking longer amounts of time (not exactly distance) to attain a certain speed you'll be presenting yourself to the parasitic losses of wind resistance thus diminishing your actual acceleration.

Anyway, I the math says you'll make it, so get registered and good luck.

 

i have done 130 in my c4, period, there are some rules that disallow me from telling you how i did it, needless to say, there was a mustang gt involved

 

I hit 135MPH on the asphalt in the High desert but I let off just because I was coming up on some cars, but I'm not sure of the salt flats. I do know that after the intake(TPIS Big Mouth ported to Felpro 1206's) and the ASM runner's combined with the plenum being port matched to the runner's and the 52mm throttle body it hit the MPH way faster than it did before(stock intake was too restrictive this one really opened it up). Maybe if the intake was upgrade it will be possible! Let us know how it goes!

Does the C4 have a top speed limiter though? Is it allowed to go that far to 150MPH? (Havn't tried it yet to see if it does!)

Thanks,Matt

 

Man you have a good memory - you said the car would "barely" make 130 in 1 mile - turns out you were exactly correct - 132 and change - 10 times that day!

I'll see if I can find the thread - but thats 2 years old!

Carl Johansson

 

justin,
you're freaking awsome man. Thats just what I needed to know! So when are you coming out to give it a try?

Carl

 

Oh, two years is a trifle.

Horsepower speed calculation

real horsepower numbers

.

 

old school