How Much Power is too much
 

So, how much power is the engine in your Cobra putting out to the real wheels???


Bill S.

OOPS!!! That should read rear wheels...


Bill S.

Bill - Welcome to the world of superchargers (I see), where horsepower is a mute point and all you have to do is change a pully/belt. You will never go back to the darkside.
The real question in my mind is; What have you done to the rear end setup to CONTROL that power ? (not what is it?)
As for me it's around 600 plus or minnus with a 5th arm and watts linkage and very hefty steel parts.
cobrashock
;) ;)

Real or Rear? Are you SURE that was a typo, REALly? LOL

For me, 450 is plenty, heck 400 would do it! And "hooking up" IS the key!

Cobra number 2 will be shooting for 400, or close to.

Ernie

My engine is being built. I expect it to produce around 500 hp. I figure 400+ on the rear wheels if I can hook up. I have put wider tires than normal on the car.

I saw a good response to "How much power is too much" by Corky Bell (Cartech), pondering the question this way:
"Okay, too much power is when you can spin the tires at any speed in any gear...but not enough power is when you CAN'T spin the tires at any speed in any gear, so how much power is "just right"?

???? It's like asking how much money is too much? Can you really have too much HP?

Good question...At this point in time, I'm using autoweld adjustable upper and lower control arms...While it works wonders to stop the wheel hop, actually getting the power to the pavement is another story....I'm thinking of dropping down to 3:27 rear gears to help things along...may throw a panhard bar in later on, once I have got a feel for the new drivetrain and it's quirks.................Only time will tell..........


Bill S.

I'll go along with the apparent majority this way:

"If it matters what gear you're in, the engine's too small."

:D

Tom

If you have to ask, you don't need a Cobra ..... :D Really I would probably have to say 551. I built a Mustang that on a Dynojet measured 535 hp and 498 ft/lb. Frekkin' thing was a monster and really a royal pain in the arse to drive on the street. :3DSMILE:

Hi Folks,

To answer the question "How much power is just right?

I have always used a wheel slip percentage in the highest gear of 14% at full throttle as the forward bite number. (this is one of the things that you work with on in chassis setup using dampers and spring rates, etc.)

This is the number that the race tire engineers like to see.

Of course, in the lower gears these numbers become much greater and requires a driver that does not treat the throttle as a on-off switch.

The JBL chassis likes about 475 ft-lbs of torque. This gives the 14% wheel slip in 4th gear with a 3.55 rear gear and 315/35/17 Hoosier DOT slicks. (The overdrive screws the numbers, therefore it is ignored in the setup process.)

With the standard street tires (Michelin Pilot 335/35/17) the number is 380 ft-lbs of torque.

Sorry, but I do not have a clue as to what the other chassis out there like. Some may be less, but I am sure that others like a lot more. (Particularly beam axle cars.)

One thing that I have found, the drivers always say that they never have enough power. But when you look at the telemetry, the throttle position, and wheel slip numbers, it is always falls in the 12>14% range. (If the car has enough power to produce these numbers.)

NOTE: This means drivers who can turn competitive lap times consistantly. (Professional level folks. For us normal guys, the numbers do move around a bit. You know, smoke from the tires due to going backwards after too much throttle application at the apex.):LOL:

57% are putting out over 400 hp at the rear wheels. Come on guys this is Club Cobra not Club Pinocchio. I put down 275 at the rear wheels as I have a chassis dyno number of 267 and that was before I put roller rockers in. 400 rear wheel hp is about 470 flywheel hp.

And your point is??????????????/

This is not one of the wisest threads to have going on here inlight of all the talk of insurance woes posted on here in the last couple of weeks.

Tom S

Richard - fascinating information, as usual... That astounds me that the Hoosier DOT slick can only handle another 95lb/ft of torque than a regular street tire..... What tires will I need for 705lb/ft then? :confused: Seriously though, I want to use the traction control feature of my Motec M800. What percentage tire slip would you suggest I enter as the best compromise between safety on the road and weekend roadrace control?

Richard
I am not at all familiar with tire slip rated in a percentage. Can you explain the theory behind this and how it is measured and/or calculated etc. I guess I always figured tires either hooked up or broke loose, not much else in between. I am interested in learning more about this. You talk about this being at wide open throttle in top gear, but at what RPM? I would think that there would be zero tire slipage once the revs are at/near the red line.

By the way, it didn't take me very long to figure out that the throttle in my Cobra couldn't be treated as an on/off switch, especially in first or second gear. I was also very happy that I had a rev. limiter while I was learning this lesson.

Wayne

See below. You do need some reserve.

Wayne,
This is not meant to be a detailed explanation, but instead an example of the 14% factor as I am familiar with.
The most controversial subject in circle track racing right now is traction control and for the most part it is illegal. The whole idea behind traction control is to keep wheel slippage to the 14% number that Richard mentioned. The simplest devices are preprogrammed to retard the timing if the unit senses RPM increasing faster than it would at 14% slippage. The more advanced units use wheel speed or drive shaft speed sensors and ground speed sensors to compare ground speed to wheel speed and then accurately calculate slippage, then retard timing.
Tests have proven that forward bite is best and lap times are quickest when slippage is kept to 14%. The better drivers use RFTC or right foot traction control, but even the best can’t compete with an on board computer. Typically the more power you have the harder it is to CONSISTANTLY control slippage using RFTC.
A while back I was involved in a thread about BB vs. SB where I loosely quoted Mario as having said he that he was able to go faster with the 351W spec racer than with the over powered 408W. I don’t think anyone believed that too much power is not better than the right amount of power, even when one of the world best drivers says it.
Scott

Fact is, you can put only so much tyre under a Cobra, all the HP in the universe is useless if you can't put it to the ground.

Maybe even Mario had his hands full with the illmanors of a cobra? Less power makes it easier to controll for sure. Scott