Requested Info: I can leave from a dead stop gentle & break the tires loose. The car doesn't fall flat ( that I can tell) I can break the tires loose from a 3rd gear roll at about 65 mph. 1 & 2nd gear there is no traction, so that is why 3rd is noticeable at the 5000 rpm. @ 5000 rpm it is though it has had a small nitrous hit, it pushes me back in the seat & breaks the tires loose hard. It has a 4:11 rear gear & a home built 383, w/ approx. 500 hp. 1 & 2nd are useless to accelerate quickly. but 3rd lets you feel what the motor is doing.

 

you have so much mechanical advantage in 1 and 2 and so much torque, the gears are useless. in 3rd, at 5000 rpm your engine produces peak torque ( or near peak) and breaks loose because the mechanical advantage of 3rd gear is still alot. you need to either:

have less engine (less torque)

have less rear end gear (less mechanical advantage) (3.08 or so) so that your engine torque will not so easily overcome your gearing.

get more traction via better tires, better lock up, etc.

or some combination of the above that works for you and your setup.

you could also use a different transmission with a different gear setup across the power band.

this is a simple problem with simple solutions; you have more engine than your car (driveline and tires) is able to handle, so either reduce engine or cowboy up on your drivline.

 

WHen I first dropped the 406ci in I experienced the same thing, when I hit 5000RPM the tires started to spin, never experienced that before, kinda took me by suprise and I have 3.08 rear end and 295/50/15's on the back, had a shi eatin gin on my face for about half an hour after though

 

Agree with motor head, it is fun, but hard to drive the car quickly because of over powering the tires. Also, how do those 295 tires fit?

 

Question, I haven't dynoed my motor, but it feels like at 5000 rpm a dyno graph would have a near vertical increase. I haven't seen this curve in the many published dyno curves. Usually the slope is does not have a large incremental increase. This sensation reminds of a pipey two stroke powerband, with the exception that it is not "dead" at low rpms. In fact I can side step the clutch at idle in 1st gear & the car lurches forward & keeps chuggin...

 

The only way to know what the power peak looks like is to DYNO it....we're waiting.....

 

dyno it; there is no way you will get a "vertical" torque curve. dyno it if you must. still, the problem should be easy to solve. you obviously have too much torque for you given traction;

 

Will dyno it, but it maybe spring before this can happen. I would like to see the numbers & curves, but also, I have taken the garage tune up as far as I can get it. It is time for the professionals to do their thing. Also, I realize there should not be a near vertical curve, that is the way i would describe the sensation of power...

 

As said before HP = (Torque(ft-lb) x RPM)/5252 (a constant).

What you feel when you accelerate is the rate of change of acceleration (actually called "jerk"). The acceleration due to gravity is 32 ft/sec^2, that acceleration would yeild a 1/4 mile time of 9.08 sec at 198 mph.

The reason you don't FEEL like all hell is breaking loose when you jump off a step (or anything else) is because the acceleration is constant. That is why 365 to 400 HP factory big blocks sometimes didn't feel as fast as the 340-375HP small blocks. The BB's torque was GREATER and MORE Constant with less of a rise so you accelerated quicker but with less CHANGE in the rate of acceleration. This is also often described as being "less peaky".

The surge you feel at 5000 RPM results from the POWER rising rapidly due to the fact that your torque is rising (or falling MORE SLOWLY than the RPMs are rising) while the revs are rising producing more power and stronger acceleration as you get into the engine's power band.

The rock and sledge hammer analogy is excellent. Another way to put it is that I could take a 3 hp lawn mower and gear it to produce 1000 ft-lb of torque. Due to gear losses I would actually have LESS than 3 HP but I would have torque available which could SLOWLY twist or move whatever you wanted twisted or moved.

Acceleration comes from power. That is why the POWER/WEIGHT ratio is what people look at as the first indicator of how well a vehicle accelerates. That is why a Ferarri with relatively low torque can produce excellent acceleration - its does so by producing its torque at high RPM. This is just what the guy said about the two engines with identical torque but with one producing it at twice the revs (giving twice the power). Torque alone will not produce acceleration - you need SPEED to go with it.

 

Once again to all who responded. Thanx, I will digest & study the theories and formulas. Some of this at a glance takes me back to my physics courses years ago, but I never enjoyed those as much! I am however helping my kids with physics, perhaps I can integrate some of this into their work!! Many thanx.( P.S. to me this is redemption when occasionally the hot topics get a little hot...)

 

1st I wonder if its your tires? You can check at a tire shop to see if they are high milage tires. Hard rubber compound. Hard rubber is like driving with steel treads, no traction.

If your spinning your tires then the engine has no load and won't fall flat. Spinning tires means your manual is behaving like an automatic with a high slip convertor- your wheels. Engine isn't under load at low rpms, its at a higher rpm.
You mention a gentle start from a dead stop breaking the tires loose. This seems contradictory? From a roll you can break the tires loose?
Or you never can get the car rolling without breaking the tires loose?

What rpms are the 1st and 2nd problem happening? Everywhere?
What do you mean by a 3rd gear roll at 65?

I don't see how you can have all of these problems simply by engine power. I have a 427 and 4.11s and don't. What I'm saying is you might make more power at top end or more at low or more at mid but you can't be doing all three. Something else is causing this, not engine power.
500 hp is happening at high rpm not low. Not at 1500 when your starting from a stop.

There is something else but probably not it- engine torgue. This might be breaking your tires loose but its pretty obvious when its done So I doubt its the probleemo.
When I shift the throttle has to be depressed for that road speed & gear. If I shift from 2nd to 3rd and let the clutch out THEN push the pedal down this is a downshift, not an upshift. Both pedals have to be synchronised so to speak.
If I'm shifting at 40 mph then that gear has to have throttle for 40 when the clutch is let out. If shifting at 65 then throttle for 65 has to already be there for 65 otherwise your using engine braking.

 

What you are feeling is "fun" motor! You obviously have some pretty serious cam and head combo..unless we're dealing with something goofy like a real slow opening vacuum sec carb.

There are lots of good technical stuff here, but HP as you are feeling it is just TQ at a high RPM. That's how you make HP..you design an engine to not "fall off" or have it "stay on the pipe" as long as you can..HP is the result.

And throttle response is not the total domain of little ports, small intakes and carbs as many would ahve you believe. Properly chosen "race" parts have no lack of throttle response.

I had to rework my 540 combo to reduce midrange TQ. I actually make the same TQ now, but it peaks at 700 rpm higher now..which means at say 4000 rpm..it's making less than before...but at 7000..it's Making LOTS more..and runs MUCH faster down the track! My TQ curve is much broader now...the peaks aren't necessarily further apart that much...just much less dramatic drop off....that allows the engine to accelerate much harder (HP) between peak TQ and peak HP.

JIM

 

Gentle take off maybe too exagerated. 1st or 2nd gear I can send the tires to smoke easily. Breaking them loose means just a quick stab at the throttle, not flooring or clutching it. From a roll in 3rd gear means driving at a constant speed of 65 then flooring it, not downshifting, upshifting or stabbing the clutch. It is not a problem, I was just wondering if it was torque or h.p. This is what I built the motor & drive train to do... The tires are 3year old low milage 255/60/15" bf goodrich radial T/A.s. I have gotten a 1.9 60' time with these tires once. I do appreciate all the feedback guys, but, I am not trying to solve a problem, was simply wondering. P.S I am having a cage installed 1st week of oct. & have a set of hoosier quick times, but the track booted me until safety upgrades were completed

 

CORRETION: I meant to say from a roll means 3rd gear approx. 30 ish mph, floor it. the car accelerates strong but as the tach swings past 5000 rpm the tires break loose and the car can get side ways. It is this point 5000 rpm that a figurative switch gets flipped & the motor comes alive. This is the point that i wondered if it is torque or hp. but there is no problems except the smile on my face when it occurs! If i floor it in 3rd at 65 mph it does the same thing but the motor is already happy, so it is not so noticable.

 

Then the simple answer to your original question is
YES
Its torque.
Its HP.
Take your pick. People tend to say one or the other but they are the same thing at this point. Torque per time is hp and no one ever is making torque at zero rpm. Torque is always said to provide movement or acceleration. The problem with this simplification is once this movement begins its no longer torque but hp. Does torque per time provide accelleration or hp?
Your original in the pipe thing is exactly whats happening.
VE must be getting boosted at this point.
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enter at your own risk
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And just to add more ness
A joule is almost the same as a watt and the watt is also a measurement of hp. Watts are used in the metric system instead of hp.
A joule is amps x volts. (metric don't use this for torque, this is just an over simplification )
A watt is amps x volts x one second. ( due to industry they break all the rules and charge your house power in kilo=1000,watts per hour=60 minutes x60seconds. This should be 36 megawatts your not supposed to mix multipliers)
Torque is 1 foot lever x lbs of force at the end of the lever.
A hp is torque X time.
A joule has no time you have to specify it. Torque is like that in a way.
A 500 hp engine is about a 35 kilowatt engine. Did hp squeek the wheels or did wattage chirp the tires?
To take this confusion further. 1 watt is equal to 1 joule second. Its also equal to 1000 joule milliseconds ( this isn't a mix since you have to specify time). 1 watt of power released in 1 thousands of a second is an explosion. Its the same amount of power but the time value has been changed. So will 1 watt of power produce an explosion? It depends on your reference of time. Will torque accelerate a car? it depends on time. And to add to this nitemare. Accelleration is another measurement that includes time as its multiplier. 1 G is 32 feet per second.... per second Thats about 22 mph... per second. 2 seconds is 44 and so on. Take away the second and your accelleration is not a rate of change but is now stagnate- its torque. But torque isn't what keeps a car going 44 mph but hp.



As final on all that felgercarb. To confuse and delude us car makers switched to liters for engine displacement. 427 is 7 liters. Ooh 7 liters sounds better. Imagine a 7 L stuck on the hood. Why didn't they also switch to watts for hp? 5 liter 16.5 kw engine. . They screwed up the engine making it metric but the chassis is still fractional.