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Discussion Starter #1
A local shop has an all-wheel-drive Dynojet that I’m gonna put my stock, rear wheel drive Q50 Sport on for a baseline run on Friday.

then I’m going to do a round of mods to reduce unsprung weight (lighter tires, wheels, brakes and driveshaft) and return to the same dyno to post results. I’ll detail the weights of the OEM parts and replacements and post the cumulative WHP gains in an update.

The more I read about it the more I am convinced it will be a pretty substantial change in power at the wheels. I’m seeing some videos where just a swap to heavier wheels / tires robs 5% of hp at the wheels.
 

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Excited to see the results. What diameter tire are you going to go with? That impacts how our car accelerates too.
 

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Looking forward to the before/after results, any ETA on the parts or is that part of you're future plans for the car
and you are just looking to get the baseline now?
 

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I'm in! 🍿
 

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Great idea.

May I suggest you get the wheels and tires so you can do it in one "test" session.

With power tools, changing your wheels will take minutes.
 

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Discussion Starter #6
Excited to see the results. What diameter tire are you going to go with? That impacts how our car accelerates too.
I’m going close to 26” even (305/30/19 and 255/35/19) VS 26.7”? For the stock sport tires.
 
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Discussion Starter #7
Looking forward to the before/after results, any ETA on the parts or is that part of you're future plans for the car
and you are just looking to get the baseline now?
Tires and wheels about 10 days out, brakes and driveshaft likely a week behind so the follow up dyno session will be around 3.5 weeks from now.
 
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Discussion Starter #8
Great idea.

May I suggest you get the wheels and tires so you can do it in one "test" session.

With power tools, changing your wheels will take minutes.
I think the best I’m going to be able to do is try to go back for the return session in the same time of day and similar weather to the baseline pulls. Everything will already be on the car when I return for that second go round.
 
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...and driveshaft likely a week behind so the follow up dyno session will be around 3.5 weeks from now.
Which driveshaft did you select?
 

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Discussion Starter #10
Which driveshaft did you select?
1 piece aluminum. The weight loss isn’t huge but Gilbert seemed to really attribute a big difference in acceleration to his.
 

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I’m going close to 26” even (305/30/19 and 255/35/19) VS 26.7”? For the stock sport tires.
Nice. My next set of tires will likely be Michelin PS4S 26.0” rears and 26.3” fronts. 305/25-20 rears and 265/30-20 fronts. That might be a while though now that I’m teleworking 4 out 5 days days a week.
 
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interested as well.. especially the weight savings of each added aftermarket part.

technically, you would be recovering 'lost' whp with these upgraded, lighter parts, not gaining any whp.
 

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Discussion Starter #14 (Edited)
interested as well.. especially the weight savings of each added aftermarket part.

technically, you would be recovering 'lost' whp with these upgraded, lighter parts, not gaining any whp.
Rear rotors 5 lbs each
Rear tires save 2 lbs each (but 60mm wider)
Rear wheels save 6.2 lbs each
26.4 lbs saved on driven wheel end

1 piece driveshaft saves 7 lbs

Front rotors 10 lbs each
Front tires 8 lbs each
Front wheels save 7.3 lbs each
50.6 lbs saved on the front, undetected by dyno but uncorking lost power on the car nonetheless.


My prediction of post 85 lb unsprung weight savings:
Detected Recovery (reflected in dyno increase)
3.3 % increase over stock whp
4.6 % increase over stock wtq

Total Recovery Unleashed (impact of F+R weight losses):
8.69 % increase in whp
12.23% increase in wtq
 

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I think the best I’m going to be able to do is try to go back for the return session in the same time of day and similar weather to the baseline pulls. Everything will already be on the car when I return for that second go round.
You don't have to worry too much about the weather because there will be SAE correction for the dyno but you do need to make sure that you used the same methodology for both baselines. For example if you are using two big fans in the front and one on the motor then you need to do the same thing. Same amount of minutes of rest between runs, etc.
 

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With 2 motors creating the same exact amount of power to the crank to 2 cars of the same mass, the power to the ground will be the same unless there is loss from creating heat, vibration, or any form of radiation. (maybe I left something out there)

But I believe the power difference is converted to stored energy, which will have to be used up in some way to decelerate. Usually convereted to heat, unless electric powered and is being reclaimed.

A car may accelerate faster, but will be harder to stop. We want to put as much power to the road NOT into stored energy.

Isn't there some law about this like:

Energy can neither be created nor destroyed. It can only change forms.

Objects at rest will remain at rest, and objects in motion will remain in motion at the same velocity, unless the object is acted on by an external force.

HP= a unit of power equal to 550 foot-pounds per second (745.7 watts).

One pound-foot is the torque created by one pound of force acting at a perpendicular distance of one foot from a pivot point when gravity is
9.80665 m/s2

I guess it's how the power is delivered (torque vs HP) unless there is a loss.

Bottom line we are trying to measure the loss difference. A dyno doesn't measure deceleration energy so aren't we are missing a part of the energy equation?

I haven't slept, so forgive the rambling. I'm sure @Avedis53 can explain this correctly in one paragraph.
 
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Discussion Starter #17
With 2 motors creating the same exact amount of power to the crank to 2 cars of the same mass, the power to the ground will be the same unless there is loss from creating heat, vibration, or any form of radiation. (maybe I left something out there)

But I believe the power difference is converted to stored energy, which will have to be used up in some way to decelerate. Usually convereted to heat, unless electric powered and is being reclaimed.

A car may accelerate faster, but will be harder to stop. We want to put as much power to the road NOT into stored energy.

Isn't there some law about this like:

Energy can neither be created nor destroyed. It can only change forms.

Objects at rest will remain at rest, and objects in motion will remain in motion at the same velocity, unless the object is acted on by an external force.

HP= a unit of power equal to 550 foot-pounds per second (745.7 watts).

One pound-foot is the torque created by one pound of force acting at a perpendicular distance of one foot from a pivot point when gravity is
9.80665 m/s2

I guess it's how the power is delivered (torque vs HP) unless there is a loss.

Bottom line we are trying to measure the loss difference. A dyno doesn't measure deceleration energy so aren't we are missing a part of the energy equation?

I haven't slept, so forgive the rambling. I'm sure @Avedis53 can explain this correctly in one paragraph.
From everything I’ve read, the reduction in unsprung weight helps braking too. I’ve been seeing situations where people see these 12-20whp recoveries from just swapping one element on the list (rotors, driveshaft, wheels+tires). I can’t figure out any reason why the benefits wouldn’t be cumulative.

So if a 2019+ Sport model starts out putting down power like the stock Berger Baseline car (334whp/ 336wtq), the impact of these Mods could push it to stock Red Sport levels of wheel horsepower.
 

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Of course it helps braking!! Less mass to slow down as there is less "stored energy" like I was saying.

Less rotational mass saves your brakes, less wear on your shocks/struts/coilovers with less mass to control.

Faster acceleration better handling.

But the downside is MORE ROAD NOISE as there is less mass to absorb the vibrations of the road surface.

My snow tires on my heavy OEM rims are quieter than my Sport Pilot 4S's.!😳 I was amazed by this, but understand why.
 

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I'm not certain that you will see a difference on the dyno by reducing unsprung weight. The dyno is measuring HP and Torque. Not rate of acceleration. You will certainly see a difference on the track though.
 

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maybe i'm lost or semi retarded (no offense to anyone).

let's go on a rs400 spec's, 400crank hp, about 350whp, stock. follow me. so the motor is using 50hp to rotate the trans, wheels/tires, axles, driveshaft and rotors. wouldn't lightening up these items allow the motor to actual have to use less HP to rotate them, ie, you having more WHP ??? i'm not saying like 20-30whp, but maybe 5-7whp freed up ???

someone chime in, i'm trying to make sense of this. cause them z1 2 piece rotors are hella expensive, alu or cf driftshsfts are $1000+ for some weight savings.
 
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