Hp gurus... a question

This was brought up to me today... Since my car was dynoed on 20 inch wheels... would it have dynoed MORE on 19's?

This was brought up to me today... Since my car was dynoed on 20 inch wheels... would it have dynoed MORE on 19's?

 

I think it is hp delivered to the wheels...whatever size or wheel weight.

easy enough have jason put his wheels on your car,

This was brought up to me today... Since my car was dynoed on 20 inch wheels... would it have dynoed MORE on 19's?

 

Hmm that was just brought up to you yesterday???

i would definitely assume it would. not just the weight but the fact that they may be slipping on the rollers.

My Dynopak dyno runs use no wheels...so I dont think wheel size has anything to do with HP,,perhaps torque though as moving mass may + or -..

depends on the type of dyno. If I recall evo sport in Cali worked on a clk63 bs and from stock wheels to dymags they saw some 20-30whp increase on the dyno. It is based on the weight of the wheel not the overall size. If your 20's are as equal to your 19's you may see no difference. It just comes down to the rotating mass and it has been said that reducing rotating mass is equal to 1 to 3 or as high as 1 to 6 of actual weight?

depends on the type of dyno. If I recall evo sport in Cali worked on a clk63 bs and from stock wheels to dymags they saw some 20-30whp increase on the dyno. It is based on the weight of the wheel not the overall size. If your 20's are as equal to your 19's you may see no difference. It just comes down to the rotating mass and it has been said that reducing rotating mass is equal to 1 to 3 or as high as 1 to 6 of actual weight?

 

This is new to me. So the lighter the wheel, the better numbers we get?

depends on the type of dyno. If I recall evo sport in Cali worked on a clk63 bs and from stock wheels to dymags they saw some 20-30whp increase on the dyno. It is based on the weight of the wheel not the overall size. If your 20's are as equal to your 19's you may see no difference. It just comes down to the rotating mass and it has been said that reducing rotating mass is equal to 1 to 3 or as high as 1 to 6 of actual weight?

On 6speed, a guy with a Gt3RS said they saw NO improvement swapping to Dymags on the dyno....

i believe lighter the wheels more the power

I would presume you kept the same overall diameter? If you did, it will make no difference.

Size no, weight/mass/rolling resistance yes.

 

The 6speed Porsche guy is an anomaly, the dymags absolutely should return a higher number every time. Easier to transfer the energy to the roller via less resistance due to lower weight.

i believe lighter the wheels more the power

 

The affect is the same. Most people don't realize the affect of unsprung aka rotating mass. Unsprung weight and rotational inertia are much more important than static or dead weight. Physics dictate that 1 pound rotational or unsprung weight is approx equal to 10 pounds static weight.

 

So take the stock rims for example that weigh...Front 28lbs Rear 32lbs. An average of 30lbs per rim

 

My Dymags weight 14lbs front and 16lbs rear. An average of 15lbs per rim.

 

Also, every six pounds of weight savings equates to one added horsepower in terms of performance.

 

15 lbs savings

x 10lb static weight comparison

x 4 wheels

 

So the total affective weight savings in comparison to dead weight is 600 pounds.

 

You would then divide by 6 to calculate the amount of "affective horsepower" you have gained, or the amount of horsepower it would take to make your car equally as fast without reducing the unsprung weight.

 

600/6 = 100 Horsepower

 

JUST replacing your stock callistos with a set of dymags has the same affect on performance as adding 100 horsepower and NOT changing the wheels. Food for thought.

600/6 = 100 Horsepower

 

JUST replacing your stock callistos with a set of dymags has the same affect on performance as adding 100 horsepower and NOT changing the wheels. Food for thought.

 

 

No way.. changing to dymags will be nowhere near adding 100hp.

No way.. changing to dymags will be nowhere near adding 100hp.

 

 

It is. Removing 60lbs of unsprung weight is the affect of adding 100hp. It's a simple mathematical formula. 60lbs off the wheels is pretty much like adding 80hp at the tires. Reduce unsprung weight WHENEVER possible. Pullies, rims, brakes, aluminum driveshafts, etc......spend your money there, not on things like lighter seats. Seats are irrelevant compared to reducing rotating weight.

 

 

It is. Removing 60lbs of unsprung weight is the affect of adding 100hp. It's a simple mathematical formula. 60lbs off the wheels is pretty much like adding 80hp at the tires. Reduce unsprung weight WHENEVER possible. Pullies, rims, brakes, aluminum driveshafts, etc......spend your money there, not on things like lighter seats. Seats are irrelevant compared to reducing rotating weight.

First how did you get 14 and 16lbs for dymags? Other 19 inch dymags have weighed 18 and 21lbs.

 

And I disagree, it will certainly make a difference but not to the affect of 100hp.

First how did you get 14 and 16lbs for dymags? Other 19 inch dymags have weighed 18 and 21lbs.

 

And I disagree, it will certainly make a difference but not to the affect of 100hp.

 

 

The weights are what they gave the dealer when I ordered them. They may vary slightly, I don't really know until they are in my hands. Trust me, unsprung mass is HUGE. Make sure you get a rim under 20lbs and you cannot spend too much on pullies, lighter brakes, aluminum or carbon driveshafts, etc.....I've been drag racing and building race cars for 15 years. Trust me, that's where you should spend your money reducing weight. Doubt if you will, but the formula is right there for you.

 

 

The weights are what they gave the dealer when I ordered them. They may vary slightly, I don't really know until they are in my hands. Trust me, unsprung mass is HUGE. Make sure you get a rim under 20lbs and you cannot spend too much on pullies, lighter brakes, aluminum or carbon driveshafts, etc.....I've been drag racing and building race cars for 15 years. Trust me, that's where you should spend your money reducing weight. Doubt if you will, but the formula is right there for you.

I certainly believe you that it makes a difference, but not as much as you claim. I too have been around the block once or twice with some pretty fast project cars. Now spill the beans on your G!!!!

I don't think the 19" Dymag's are 14lbs & 16lbs respectively --- they are 17lbs front and just under 20lbs rear.

 

I believe there are many more factors than simple unsprung weight. The dynamics of a rolling vehicle on the road is rather static so simple theoretical calculation doesn't describe the entire picture.

 

At any rate, my SL (with CCB's) fresh off from the dealership feels nimble and handling is more precise compared to my former SE. Swapping the OEM Scorpius wheels to 19" Dymag's enhances the effects further. But one can hardly tell, if at all, within city driving. Above 80kph (50mph), things are more noticeable. But I disagree that swapping with the Dymag's will be = to 100hp; it sure never felt like it at any time or at any sane speed, didn't even feel like 30hp. If it really does = to 100hp, Dymag's should charge double the cost and they'll still be flying off the shelf.

I certainly believe you that it makes a difference, but not as much as you claim. I too have been around the block once or twice with some pretty fast project cars. Now spill the beans on your G!!!!

 

 

Typically, I have heard many people state that loosing unsprung weight is about 4x more effective than sprung weight. So if your Dymags are 60lbs lighter than stock, this would be equivalent to about 240 pounds of gross weight. Which would roughly be equal to gaining 24hp. I think 100hp is a bit optimistic.

 

 

Typically, I have heard many people state that loosing unsprung weight is about 4x more effective than sprung weight. So if your Dymags are 60lbs lighter than stock, this would be equivalent to about 240 pounds of gross weight. Which would roughly be equal to gaining 24hp. I think 100hp is a bit optimistic.

That I would be more inclined to believe. However dymags are not 60lbs lighter than stock. Off the top of my head:

 

Dymags are 18 and 21 lbs rear

Callistos 25 and 28

Scorpius 22 and 24lbs...

 

So on the Callistos you could save around 30lbs, and the Scorpius around 14lbs...

The wheel diameters work like gears. Small diameter, quicker rotation. I don't understand why anyone gets 20" other than for appearance. What are the diameters stock?

There are many different variables that come into play here. Everyone talks about reducing rolling weight when dealing with wheels. Yes obviously less is better and for every 1lb in reduction is akin to removing 6lbs of static weight from the car. However this is more applicable to handling characteristics - turn in, compression, rebound etc etc.

 

When talking about dyno numbers, acceleration, and decelleration, moment of inertia - measurement of how much force it take to spin or stop the wheel from spinning - is the key to the equation. If you want to compare a 19" to a 20" wheel for example, you have to take into consideration the construction of each one. What type of design? How is the weight of the construction material distributed throughout of the wheel? Is the majority of the weight near the center, spread fairly even throughout or is there a large mass of material torwards the outside edge?

 

Hypothetically speaking, if the Cassiopea and Callisto weighted exactly the same, because of the design of the Callisto and how the material is distributed, it would dyno slightly lower in certain areas on the graph because it would have a higher moment of inertia to start moving. It would be a fairly small difference however.

 

These effects would most likely not alter the peak power on a dyno, granted you pull through the peak point where power naturally begins to drop off.

 

With your car specifically Allan, I would expect to see a very slight 2 - 4hp / 3 - 5 lb/ft loss on the low end due to the slight increase in size from the tire. Your peak number should not be effected and on the street, the much larger contact patch will outweigh any minor power loss. If you were to run a 19" wheel setup with the equivalent 19" Tires to your 20's the effect would be the same.

 

This is really an apples to oranges comparison as you could compare 19" Wheel X to 20" Wheel Y to 18" Wheel Z and have competely different answers. Just remember YRMV.

There are many different variables that come into play here. Everyone talks about reducing rolling weight when dealing with wheels. Yes obviously less is better and for every 1lb in reduction is akin to removing 6lbs of static weight from the car. However this is more applicable to handling characteristics - turn in, compression, rebound etc etc.

 

When talking about dyno numbers, acceleration, and decelleration, moment of inertia - measurement of how much force it take to spin or stop the wheel from spinning - is the key to the equation. If you want to compare a 19" to a 20" wheel for example, you have to take into consideration the construction of each one. What type of design? How is the weight of the construction material distributed throughout of the wheel? Is the majority of the weight near the center, spread fairly even throughout or is there a large mass of material torwards the outside edge?

 

Hypothetically speaking, if the Cassiopea and Callisto weighted exactly the same, because of the design of the Callisto and how the material is distributed, it would dyno slightly lower in certain areas on the graph because it would have a higher moment of inertia to start moving. It would be a fairly small difference however.

 

These effects would most likely not alter the peak power on a dyno, granted you pull through the peak point where power naturally begins to drop off.

 

With your car specifically Allan, I would expect to see a very slight 2 - 4hp / 3 - 5 lb/ft loss on the low end due to the slight increase in size from the tire. Your peak number should not be effected and on the street, the much larger contact patch will outweigh any minor power loss. If you were to run a 19" wheel setup with the equivalent 19" Tires to your 20's the effect would be the same.

 

This is really an apples to oranges comparison as you could compare 19" Wheel X to 20" Wheel Y to 18" Wheel Z and have competely different answers. Just remember YRMV.

 

 

So far Jason has commented that traction is quite good!