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Maximum Useful Power in a street car

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Maximum Useful Power in a street car

Postby SchmidtMotorWorks » Sat Jun 28, 2008 1:58 pm

With the ever increasing power available in street able engines, is there a point at which there are no transmissions or tires that can handle the power?

Take for example a big block roadster could easily have 1000HP with blower, turbo or nitrous. Are there street drivable transmissions and tires that would make the power useful?
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Re: Maximum Useful Power in a street car

Postby plovett » Sat Jun 28, 2008 2:18 pm

SchmidtMotorWorks wrote:With the ever increasing power available in street able engines, is there a point at which there are no transmissions or tires that can handle the power?

Take for example a big block roadster could easily have 1000HP with blower, turbo or nitrous. Are there street drivable transmissions and tires that would make the power useful?


I would say at that level, transmissions? easily. Tires?, not so much.

I am going to say, very simplistically, that around 700 hp is a very general practical limit for hooking on DOT tires on the street. I'm sure some people have done it with more hp. I can't do it on drag radials with only 530 hp. I definitely need some suspension work, though. Yup, I'm sticking with 700 hp. [-( 8-[

JMO,

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Postby Keith Morganstein » Sat Jun 28, 2008 2:51 pm

It depends on what the street car is going to do.

Stoplight to stoplight or the Autobaun.
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Postby SchmidtMotorWorks » Sat Jun 28, 2008 3:05 pm

It depends on what the street car is going to do.

Stoplight to stoplight or the Autobaun.


I'm thinking,,, what if you wanted to make a super car based on a compilation of the best American after market parts for a V8, something a few steps up from a Cobra car but still front engine. I'm trying to figure out what the practical limit would be for the engine. It seems that it would be easy to have way more power than a street drivable car could ever use with a fairly ordinary big block with power adders. In fact it seems that with a turbo, a big 4 would be more than enough and would have a weight savings.
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Postby Lucky13 » Sat Jun 28, 2008 3:48 pm

Controlling the power curve is the key here ( after getting the car to work). It may be possible to use 1500hp or more if applied right. If not applied right ( and the car not working) even 500hp could be to much.

I feel sure there are street cars with over 2000hp that work. There not using it on back roads , but they can get down the 1/4 mile.

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Postby PackardV8 » Sat Jun 28, 2008 4:36 pm

The late Mark Donohue said, "I'll have too much power when the wheels are still spinning at the end of the longest straight."

In today's traffic, it is almost impossible to really use 400 HP. I drive fairly rapidly, occasionally even over in Montana, and the times when I can hold a 400 HP engine wide open for any length of time are seldom and never. A quick burst up through the first two or three gears is fun. Passing at will on a two-lane is nice to have. However, I find myself constantly running up the tailpipe of a gomer. Pass one, strafe a couple of curves and there's another one in the way.

Unlike Germany, hardly anyone in the US watches his mirrors. Even with 400 HP, better have good brakes. Clear day on uncrowded I-90, as I'm rapidly closing at triple digits and a gomer pulling a 5th-wheel going 5 MPH faster than the gomer in front of him eases over into the left lane and parks.

Bottom line for me, anything over 500 HP is for cruise-night-braggin'-rights. It is not really usable in any of the 50 states I drive in. As to the question of a strong 4-cylinder; to this day, the best-balanced, most-fun-for-the-dollar cars I have ever owned were the Porsche 944s, especially the Turbos. Imagine an '80s 944T with a Roush Cup car take-out with a streetable roller cam. Now, there's 650 HP which would be fun to try to use and it could be built for less than $25K.

thnx, jack vines
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Postby Keith Morganstein » Sat Jun 28, 2008 4:45 pm

The V6 or 4cyl would work with enough turbo, but super-cars need something perceived as exotic or very nasty so it better really perform.

An alloy v8 is probably the best all around choice for power, sound and image.

I remember a guy with a high HP blown big block in a pick-up truck. It had ridiculous gears, something like 2.29:1 ratio. It had enough power to run the 1/4 in the low 10's using just first and second gears. I mention that as one way to deal with high power, traction and street-ability.

There was a thread by "torquemonster" about building a super car.
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Postby FordManVT » Sat Jun 28, 2008 5:45 pm

I'm with Packard...even if you get 1000hp to hookup, what's it good for besides 0-60mph? My daily driver has 300bhp and AWD. I could probably use 400bhp once in a great while, but not often enough to justify it.


I would keep it simple and cheap. go with a small block aluminum v8. With a 4cyl turbo, once you add the turbo, piping, intercooler, etc. are you really going to save any weight? It'll be complex no matter the weight.
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Postby plovett » Sat Jun 28, 2008 7:55 pm

I was assuming a street car with street tires trying to hook up for a drag style launch on the street. Not the same trying to hook up on a drag strip which is much cleaner/stickier.

"Supercars" don't often do drag style launches. IMO, they're much more likely to punch it at 50 mph or higher on the highway.

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Postby Larry Heath » Sat Jun 28, 2008 8:11 pm

I kind of think that the 700hp number is a pretty good number, as far as usable power level goes. One of the first cars I ever owned was a 1968 Mercury Cyclone with a 427 with tunnel port heads, ect. at a guess I’d say around 700 hp on tap, easy. At around 3500 lbs and using N50x15’s of that time period and top loader on surface streets it was not easy to get hooked from a dead stop, but not impossible either. With the compromise rear gearing this would allow for bottom end acceleration which very very few could match and a top end way in excess of 165 mph, aerodynamics were not something I was aware of at the time. At 165 mph the car was nearly uncontrollable even on a straight section of interstate, which at the time was new and smooth as a billiard table and quite deserted at times, at 155 mph cruse it would not even break a sweat. I suppose that if I had some sense of what aerodynamics could do I would have had serious issues with the tires safety, not that 155 mph wasn’t pushing it to and most likely beyond the limits of the technology of the time. If I had an air dam and a spoiler on the car I don’t doubt the car would have easily top out in the 180 to 190 mph range and I would have blown a tire and I’d have killed myself. So I suppose that a certain amount of ignorance is a blessing at times.

Today with all the chassis and aero technology and power available today who knows what the limits really are, all depends on what type and style of car you wish to run. Look what can be done in Indy Cars on the street circuits. What is the HP level there?

What I am very sure of, is that we can very easily build more power than can be safely applied to surface streets, and way more power than some have any real concept of just what they are in control of, or not, as the case may be. 300 or 400 hp may be way more than some have any right or enough sense to be in control of, on the other hand some may be capable of safely dealing with a car with 1000 or 1500 hp on tap, is it all usable to the max no way.

It’s all relative. Say moderately knowledgeable driver, moderately good chassis, 700 hp yields max usable fast/quick on the street. For whats its worth that is my opinion.

Later Larry
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Postby enkeivette » Sat Jun 28, 2008 8:11 pm

Depends on the car, I'm around 600hp in a 3rd gen Corvette. I can only fit a 275 tire without flares before it hits the frame. I'm going to push the limit next time and see if I could sqeak by with 295s, but that's a big maybe. 1st and 2nd are useless. And the rear end will slowly slide to the side sometimes in 3rd gear. These are Z rated Nitto tires.

But if you have a 1st gen Camaro that has been tubbed and you can fit some DOT steam rollers under there, why not?
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Postby prostreetL-78 » Sat Jun 28, 2008 11:28 pm

I`ve got a tubbed 67 camaro street car. It was driven on 1500 miles of the Power Tour. It makes an honest 700 hp out of a 496 with a G force 5 speed. I run it through the gears on back roads and if get the car rolling and roll into the power in first gear rather than dumping the clutch it hooks remarkably well. It moves around up to about 100 mph but always stays straight. On the other hand, I dropped a gear and the gas pedal passing a car at 60 mph once and ended up looking through his side window through my windshield. :shock: I held onto it but won`t do that again!
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Postby Dodge Freak » Sun Jun 29, 2008 12:25 am

Believe it or not, there is still great places for a high power car. Here in S.E. Michigan
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Postby SchmidtMotorWorks » Sun Jun 29, 2008 2:50 am

The V6 or 4cyl would work with enough turbo, but super-cars need something perceived as exotic or very nasty so it better really perform.


I was thinking for a while that a super car really needs to have a V12 to be exotic but what got me thinking about this power limit thing was when I ran the numbers on what size V12 would make 600hp, it was so small it seemed kind of pointless to spend so much to be basically equal to some common V8s. Something about a 3.5" piston just doesn't seem right either.
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Postby Greezer » Sun Jun 29, 2008 7:33 am

there is still great places for a high power car. Here in S.E. Michigan
Like the M5 connector, southbound from 15 mile road... :D Also, if you're takin' one for a rip, best to know where the MSP cameras are, they're everywhere.

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