100 pound loss = how much HP gain???

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318willrun said:
That's why I'm kind of done with this thread... LOL. Everyone is bent on ET slips, and the faster you go the harder it is and more hp it takes, and traction. I thought i made the point in my opening post that i was aware of the tenth per 100 lbs. That is why I made the question bigger lettering and underlined it. How much HP equivalency is a 100 lbs loss? LOL :D :D :D
What this tells me is nobody knows how much hp I have to add to make up for a 100 lbs added. That's fine.
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Nobody can tell you until we know the weight of a vehicle@the line, a previous time slip for mph, then we know your hp, then it can be worked out reasonably close.
examples>
A 3000lb car that has 650fwhp can run 9.70@138, the same car on the same day with 100lbs taken out needs only 628fwhp to run the same ET/mph...22hp less.
A 3500lb car with 650fwhp can run 10.21@131, @3400lbs its 631hp....19hp less
A 3500lb car with 300hp can run 13.21@101, @3400lbs = 292hp, 8hp less.

Also 10hp is not necessarily 1/10th in ET. My old 340 Cuda ran 12.40@108 na with 368fwhp. It then ran 11.01@122+N20 which is 14/10ths faster (140hp)...but it made 157hp more on the track to run the no.
 
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Hot Metal said:
Nobody can tell you until we know the weight of a vehicle@the line, a previous time slip for mph, then we know your hp, then it can be worked out reasonably close.
examples>
A 3000lb car that has 650fwhp can run 9.70@138, the same car on the same day with 100lbs taken out needs only 628fwhp to run the same ET/mph...22hp less.
A 3500lb car with 650fwhp can run 10.21@131, @3400lbs its 631hp....19hp less
A 3500lb car with 300hp can run 13.21@101, @3400lbs = 292hp, 8hp less.
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I see your examples of a car but would a truck have expeditious wind resistance?
 
I know most of what you guys are saying is true. It's just hard to think of an 18 second A body losing 1000 pounds and running 17 seconds. I always heard a 1/10 per hundred. But in slower cars like the example above I have gained more than a tenth.
 
j par said:
Try giving an answer to post 50?..
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Almost impossible to do that. Those two are like apples and Rocky Mountain oysters. Chassis rigidity, wheel base, track width, sheet metal, ride height and some other stuff is so far removed one from the other that it's damn near impossible to compare them.

Aero doesn't really matter until about 100 MPH (120 according to some others) so that factors in as well.

It's not cut and dry.
 
So nobody can answer the question without giving an ET scenario... But thanks for all that tried.
:thankyou:

I'm moving on.... :)
 
318willrun said:
So nobody can answer the question without giving an ET scenario... But thanks for all that tried.
:thankyou:

I'm moving on.... :)
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I have a related question... how much longer do you think it would take Mary Poppins to drop out of the sky if she had an umbrella that was 1 inch more in diameter...lol..
 
Here’s my way of looking at it.......

Truck weighed 3760...... so 100 less is 3660.

Motor should make 150-165hp as it sits in the truck.

The power to weight ratio improved by about .6lbs/hp.
 
Some of this falls under sprung and unsprung weight. reducing unsprung weight has the greater advantages - lighter wheels and tires are the easiest. We did this with a track car and picked up noticeable gains, especially on acceleration. RPMs were down a little bit as well. I believe we were able to shave 25 pounds per wheel/tire combo
 
PRH said:
Here’s my way of looking at it.......

Truck weighed 3760...... so 100 less is 3660.

Motor should make 150-165hp as it sits in the truck.

The power to weight ratio improved by about .6lbs/hp.
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Exactly. You change hp/weight ratio which is key in acceleration. Your illustration is the way I looked at it
 
Plugging in some numbers into the basic Wallace calculator, and using the avg of what I felt would be a realistic power output for the current motor as it sits in the truck.......
3960lbs and 157hp = 17.08@79.12
3860lbs and 157hp = 16.94@79.79
 
PRH said:
Plugging in some numbers into the basic Wallace calculator, and using the avg of what I felt would be a realistic power output for the current motor as it sits in the truck.......
3960lbs and 157hp = 17.08@79.12
3860lbs and 157hp = 16.94@79.79
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To me the toughest part about weight is inertia. Sitting at a dead stop and accelerating hard is where weight challenges motion the greatest. While true with the aid of good gears, converter, or massive amount of torque can mask this effort to look effortless, science facts aren't changed. Thinking on my Duster, or any vehicle for that matter, a motor can seem bigger with nothing changed except weight loss. A 120 hp is enough to go 10's if it's in a light motorcycle. The only reason cars are faster from 0-60 than they are from 60-120 is simply because of gearing, and maybe some wind resistance. It's why machines with variable drive clutching will simply not take off if the clutches are messed up and the belt is all the way at the bottom of the driven pulley, but once moving will gain speed with them in the same position. Inertia.
 
318willrun said:
Exactly. You change hp/weight ratio which is key in acceleration. Your illustration is the way I looked at it
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The problem is all that is for an optimized chassis, clutch/converter (I always put clutch first because real race cars always have 3 pedals), shock tuning, gearing and even hood scoop size and placement (if you have a hood scoop) all factor into it.

That's why when I see any combination sorted out to where the ET matches the MPH I'm impressed. It's damned hard to do. And the quicker you go, the smaller the flaw that will expose itself, and is usually harder to fix.

I did a ton of testing on hood scoops and I can tell most of them are worthless. They are too low and too far forward to do much when you get enough speed to make them function.

And it goes on and on. If you take clutch/ converter out of the equation, the biggest chassis tuning issue is Instant Center and shock tuning. On both ends.

I've watched hours and hours of my customers cars on video and then brought them in to watch it with me. Almost every time, they can't see they are beating the tire to death, or they hit the wheelie bar so hard it unloads the chassis. Or the front is so loose it bangs off the limiters and unloads the entire chassis.

I've watched thousands of runs of cars (especially clutch cars) and really, until you get into Comp Eliminator or really fast bracket cars that data log, most of these cars could benefit from going on the scales and then doing nothing but making 100 foot runs just tuning the shocks.

I forgot about springs. Most guys over spring the hell out of everything, which makes the shocks job all the more difficult. So do ladder bars. Especially with a stick. The Instant Center is too damned high and short for most anything.

So again, the answer is to optimize whatever you have, get it as light as you can within reason and tune it.

I also forgot to mention weight bias. Way too many guys do everything they can to get 50% or more weight on the rear axle. In most cases (and in very high HP cars it's critical) that's the wrong move to make. You end up either moving weight forward, or if you don't have any weight to move, you have to add it to calm the chassis down. And, where you put the weight is critical.
 
yellow rose said:
That's why when I see any combination sorted out to where the ET matches the MPH I'm impressed. It's hard to do. And the quicker you go, the smaller the flaw that will expose itself, and is usually harder to fix.
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EXACTLY !! And even MORE impressive when it's done in a true street car. Drag cars with 5200 converters, 4.88s and slicks makes it easier. Of all the cars I've ever owned, my current Duster is the ONLY car I've ever owned to have the ET match the MPH, and they've all been street cars.
 
318willrun said:
EXACTLY !! Drag cars with 5200 converters, 4.88s and slicks makes it easier.
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This is why I can hardly wait for you to do your 10.99 in your race truck..
You'll have your converter, gears, and slicks to show everyone how easy it is...:thumbsup:...
 
j par said:
This is why I can hardly wait for you to do your 10.99 in your race truck..
You'll have your converter, gears, and slicks to show everyone how easy it is...:thumbsup:...
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Really??? We were talking about running the ET to match the MPH. It's easier to run the ET to match the MPH with those components.
 
j par said:
Yes really I'm excited to see how easy you make it....
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I'm already doing it with my Duster.... 1320 divided by 99 mph = 13.3's. Exactly what it runs... and I'm doing it with 2.94's/stock converter in 100% street form - all which adds to the difficulty.
  • and if you think it's so easy, your 112 mph should run 11.7's, so go make it happen in street form, as it sits. Then you can find out how difficult it really is.
 
318willrun said:
I'm already doing it with my Duster.... 1320 divided by 99 mph = 13.3's. Exactly what it runs... and I'm doing it with 2.94's/stock converter in 100% street form - all which adds to the difficulty..
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I haven't heard that run down before thank you for letting me know..
I wonder what it would do with 5200 converter and 4:88 gears?...
 
j par said:
I haven't heard that run down before thank you for letting me know..
I wonder what it would do with 5200 converter and 4:88 gears?...
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What it would do? Kick the snot out of somebody's 410 stroker, that's what it would do :D :D :D
 
318willrun said:
  • and if you think it's so easy, your 112 mph should run 11.7's, so go make it happen in street form, as it sits. Then you can find out how difficult it really is.
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That would blow my reputation for having the slowest Stroker on the forum...
 
j par said:
I wouldn't be beating your chest too hard because you'd merely be beating the slowest stroker on the entire forum...
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If I was you, I'd see that as a sea of opportunity. That would make me smile if I owned the car, then I'd roll up my sleeves and get to work.
  • By the way, the truck isn't getting 4.88's and a 5200 stall
 
318willrun said:
If I was you, I'd see that as a sea of opportunity. That would make me smile if I owned the car, then I'd roll up my sleeves and get to work.
  • By the way, the truck isn't getting 4.88's and a 5200 stall
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I don't understand why you make these off examples that you've never tried so easy or have you tried a 5200 stall with 488 gears and found them easy..?
 
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