Question about acceleration with mazdaspeed rims

[palerider]

Hey guys. Ive posted just a couple times, and plan to become more of a contributor(or pain whichever you prefer..lol)

My car is at the dealer getting the MS CAI installed, and when I pick it up Im thinking about ordering the Rays rims next. My question is one Ive never really seen addressed....

What is are the specific improvements that such a lighter wheel will make on my ride, acceleration, cornering, etc. Ive never had aftermarket rims on any of my cars so Im a little in the dark as to what to expect. I know that most of that is going to just be opinion, but the guys who drag must have a pretty good idea of what lighter rims actually can accomplish at the track. There was a guy who put 20's on and everybody was pretty agreed it would affect his performance noticeably..... for the worse.(Look good though, so nice tradeoff!!!)

A similar thread discussing the performance improvement on 16 lb wheels versus 24 pound wheels is what Im hoping for here. Acceleration is whats most important for me. Also.... does a lighter wheel effect how much power goes down through the wheels in a dyno. Im scheduled for one on Monday, and had never heard that commented on before. It seems like it should affect power to the wheels on a Dynojet..... even if only marginally.

Thanks in advance.(drive)

 

[njaremka]

general drivability will be improved with lighter wheels, especially losing 8lbs per wheel? wow!

when ig o from my winter set-up, which is about 42lbs per corner, to my summer set-up, which is a tick over 37lbs per corner, i notice a HUGE difference. the car is a little more responsive inthe corners, and take off from a stop is much easier. also, the car feel more "peppy" on the accelerator pedal.

the only thing you might regret from purchasing those wheels is the price. $400 each? - OUCH!!

 

[palerider]

When you say a "HUGE difference"....can you compare it to what would be felt on a CAI butt dyno. Ive often heard that to be described as a huge difference as well....

And a CAI gives a 20+ hp difference. If wheels affected the acceleration in a similar fashion, then what could be expected in the 1/4. A couple tenths maybe?

Thanks for the quick response, BTW!

 

[njaremka]

on a speed3, i have no idea. on my protege es, i felt a bigger difference from the wheel switch, than from my CAI.

 

[palerider]

on a speed3, i have no idea. on my protege es, i felt a bigger difference from the wheel switch, than from my CAI.

Thats amazing!!! 5 pounds less at the wheels, and Im assuming stickier tires, feels like more than the gain of an intake. Thats an interesting statement, and exactly what I was looking for.

The assumption is that a dyno for whp, MUST then show an increase. The only way acceleration with lighter wheels is improved is that less hp is getting lost through wheel transfer. Right?

Ive never seen a before and after dyno with wheels so I'll be the first. Whp for stockers and whp for the mazdaspeeds. I think Im gonna pull the trigger.

 

[njaremka]

you MIGHT not see any increase on a dyno, but i don't have anything to back that up with. simple physics tells you that it is easier to move something with less mass. thats whats really going on. its just easier for the car to spin lighter wheels.

 

[palerider]

you MIGHT not see any increase on a dyno, but i don't have anything to back that up with. simple physics tells you that it is easier to move something with less mass. thats whats really going on. its just easier for the car to spin lighter wheels.

I totally agree.

So if we have a certain hp at the crank, and hp is what spins the tires, and the tires spin faster with lighter tires.....it has to be because more hp is showing up through the tire. What else is making it spin faster.

It has to show at the dyno!!

The dyno doesnt know if its wheel/tire weight or a bigger turbo.... all it reads is the rate at which the tires spin. Now its just a matter of finding out what 7-8 less pounds of wheel, on a Speed3, gets us on a dynojet.

Some of the track guys should have an opinion on this. I hope they weigh in, even if its to crack my head with some reason Im missing.

 

[Craighjr]

I might be wrong.

I totally agree.

So if we have a certain hp at the crank, and hp is what spins the tires, and the tires spin faster with lighter tires.....it has to be because more hp is showing up through the tire. What else is making it spin faster.

It has to show at the dyno!!

The dyno doesnt know if its wheel/tire weight or a bigger turbo.... all it reads is the rate at which the tires spin. Now its just a matter of finding out what 7-8 less pounds of wheel, on a Speed3, gets us on a dynojet.

Some of the track guys should have an opinion on this. I hope they weigh in, even if its to crack my head with some reason Im missing.

I'm under the impression that you want to gain hp by putting on Mazdaspeed wheels. that's impossible. The light weight wheels will allow your engine to rev up faster (much the same as internal ballance shaft removals or light weight flywheels). You may see a quicker pull on the dyno, but hp should remain constant. The lighter stuff allows the engine to spin up faster improving drivability. They always say removing x lbs is "like" adding x hp. They say "like" because your improving things you can feel but the hp is most likely consistant. That being said I have the MS Rays and would love to see a graph proving that they add hp or just allow peak tq to occur sooner.

 

[Rotus8]

You get three main effects from lighter wheels.
1) Reduced mass of the car. Acceleration = Force X mass, so less mass gives more acceleration for the same power. This is a percentage of the total mass of the car, and probably not too important.
2) Reduced rotational inertia. This is the same as above, but can make a big difference, depending on the radius of the place where the mass is reduced. Less mass at the center of the wheel makes little difference, where less mass at the outer diameter of the wheel makes a bigger difference.
3) Unsprung weight. A lower mass wheel allows the suspension to keep the tread on the pavement more easily. The wheel reacts more quickly to the force of the spring. However, this can cause some undesireable effects if the suspension is not tuned to take advantage of the low mass wheel.

 

[palerider]

I'm under the impression that you want to gain hp by putting on Mazdaspeed wheels. that's impossible. The light weight wheels will allow your engine to rev up faster (much the same as internal ballance shaft removals or light weight flywheels). You may see a quicker pull on the dyno, but hp should remain constant. The lighter stuff allows the engine to spin up faster improving drivability. They always say removing x lbs is "like" adding x hp. They say "like" because your improving things you can feel but the hp is most likely consistant. That being said I have the MS Rays and would love to see a graph proving that they add hp or just allow peak tq to occur sooner.

I would agree that wheels dont add hp, at least anymore than cool stickers and ricer wings..lol. But..

the whole idea of measuring hp with new mods from a baseline number starts by measuring whatever hp is TRANSFERING from the crank to the wheels. In other words we increase crank but measure wheels. There is a loss that occurs.

My real question is.... does a significantly lighter wheel, INCREASE the amount of HP that tranfers to the wheel. Does LESS wheelhp loss occur.

Technically it doesnt matter if we increase hp at the crank and more true hp tranfers to the wheels OR ....
we just simply turn the same amount of crankhorsepower into more actual WHEELhorsepower.

The result is the same. Our car goes faster and our dynos increase, because we dyno at the wheel.

 

[Rotus8]

I would agree that wheels dont add hp, at least anymore than cool stickers and ricer wings..lol. But..

the whole idea of measuring hp with new mods from a baseline number starts by measuring whatever hp is TRANSFERING from the crank to the wheels. In other words we increase crank but measure wheels. There is a loss that occurs.

My real question is.... does a significantly lighter wheel, INCREASE the amount of HP that tranfers to the wheel. Does LESS wheelhp loss occur.

Technically it doesnt matter if we increase hp at the crank and more true hp tranfers to the wheels OR ....
we just simply turn the same amount of crankhorsepower into more actual WHEELhorsepower.

The result is the same. Our car goes faster and our dynos increase, because we dyno at the wheel.

A "proper" dyno won't show any difference. The engine is still putting out the same power and the friction losses are the same. However, an inertial dyno (which most commonly accessible dynos are) may show some increase, but it's an illusion. An inertial dyno works by the car accelerating a large drum of known inerta. The software then computes the amount of power required to accelerate the drum at that rate. If the drum has large inertia compared to the rotational inerta of the wheels and other drivetrain elements, you won't see a difference. If the drum is lighter, you may see some difference, which is one of the inaccuracies in inertia dynos.

YMMV. This is one reason why you should always use the same dyno when making comparisons of tuning & modification upgrades.

 

[Rainman]

F = MA. If you decrease the mass for a given force, the acceleration increases. So for the same TQ (that is, force applied at distance) you end up with wheels that spin faster. This improves your acceleration, but your HP stays the same.

R

 

[palerider]

Thanks Rainman/ Rotus...

Your posts were EXACTLY the kind of response I was hoping for. It still seems strange how acceleration increases, and faster spinning wheels cant have something to do with power, even if indirectly.... but you cant argue with the mathmatical equations. lol.

Since were talking about acceleration, it leads me back to my original questions other part. Do you guys have any idea about what these wheels or other lighter, maybe even smaller wheels would net at a track in time reductions? Of course all other things being equal.

Would it even be a consideration? or are wheels more of a cosmetic change and should be chosen essentially as one?

 

[Rotus8]

Thanks Rainman/ Rotus...

Your posts were EXACTLY the kind of response I was hoping for. It still seems strange how acceleration increases, and faster spinning wheels cant have something to do with power, even if indirectly.... but you cant argue with the mathmatical equations. lol.

Since were talking about acceleration, it leads me back to my original questions other part. Do you guys have any idea about what these wheels or other lighter, maybe even smaller wheels would net at a track in time reductions? Of course all other things being equal.

Would it even be a consideration? or are wheels more of a cosmetic change and should be chosen essentially as one?

In my opinion, unless you are already a highly competitive driver, wheels are a cosmetic change. If you are looking for a competitive edge, the very first thing to spend money on is driver training; there is a huge amount to be gained there for reasonable amounts of change, and it is major fun too!

 

[DaleNixon]

F=MA. So stop eating McDonald's and get your ass to the gym!

Edit: Disregard this post. I was being a drunken jackass on the internet. (thinkbeer There might be some truth here though =D

 

[whitey4311]

F=MA. So stop eating McDonald's and get your ass to the gym!

Edit: Disregard this post. I was being a drunken jackass on the internet. (thinkbeer There might be some truth here though =D

LOL, yeah it would be cheaper to loose 20lbs of body weight too.