2017 diff swap

[mrg666]

Originally Posted by gtengr

I posted my equation? Since you're saying I'm wrong, you should be able to compare it to the equation you use and easily explain why it's wrong. I'm not taking magazine top speeds over what Subaru published, but even if we use those numbers, it doesn't change my point: higher numerical gearing = higher 6th gear RPM = more horsepower put to the ground = incrementally higher top speed if it's aero drag limited.

Are you able to read? Or are you playing the dumb? I am not questioning your simple rpm calculation. I showed the same number in my post. It is correct.

I am asking you to backup your increasing top speed claim against two references I posted (and I can post more). Show the calculation.

[Tokay444]

Originally Posted by mrg666

Final drive replacement is a tradeoff, not really a power upgrade. Your engine will be working harder to do the same work. Acceleration will be quicker but sustained speeds will be at higher rpm. You might like it in the city since the car will feel quicker. But freeway driving will be worse; engine will be running at higher rpm on freeway, it will be noisier, and gas mileage will be lower. Even on track, you will be compromising your top speed for acceleration.

You want more power. So the right solution is getting more power. I recommend one of the followings.
- header + tune
- forced induction

If I had the 2017, I would go back to 2016 final drive and upgrade with FI again.

Having never been able to hit top speed on any track I've driven, I'll take the extra acceleration.
Also, if you compare engine load, I bet the engine is working less hard to do the same work. Rpm=/=effort.

[ermax]

Originally Posted by mrg666

Are you able to read? Or are you playing the dumb? I am not questioning your simple rpm calculation. I showed the same number in my post. It is correct.

I am asking you to backup your increasing top speed claim against two references I posted (and I can post more). Show the calculation.

The car makes power basically all the way to redline. So if you are running higher RPM then you have more power to pull a higher speed. If the car was limited because it was hitting redline in 6th gear then sure it would have a lower top speed.

[mrg666]

Originally Posted by Tokay444

Having never been able to hit top speed on any track I've driven, I'll take the extra acceleration.
Also, if you compare engine load, I bet the engine is working less hard to do the same work. Rpm=/=effort.

Of course, that is totally your decision and your car. How can I argue with that?

[mrg666]

Originally Posted by ermax

The car makes power basically all the way to redline. So if you are running higher RPM then you have more power to pull a higher speed. If the car was limited because it was hitting redline in 6th gear then sure it would have a lower top speed.

You are not redlining at 6th, you cannot. Because drag limited (not enough power), remember? That is why I said increasing power is more important.

[ermax]

Originally Posted by mrg666

You are not redlining at 6th, you cannot. Because drag limited (not enough power), remember? That is why I said increasing power is more important.

Okay now I'm starting to think you are the one playing dumb. Reread all the posts in this thread and then return.

Edit: As explained several times. The higher final drive would put you higher in the rev band. The car makes power all the way to redline so the higher final puts you higher in the band producing more power. More power, more top speed. You agree that the car will accelerate faster. The gearing keeps the revs in the power band. Do you think this simply stops once you put it in 6th gear?

[mrg666]

Originally Posted by ermax

Okay now I'm starting to think you are the one playing dumb. Reread all the posts in this thread and then return.

Edit: As explained several times. The higher final drive would put you higher in the rev band. The car makes power all the way to redline so the higher final puts you higher in the band producing more power. More power, more top speed. You agree that the car will accelerate faster. The gearing keeps the revs in the power band. Do you think this simply stops once you put it in 6th gear?

The car does not make more power with different final gear. Do you realize that?

Repeat after me:
Engine is the same, power is the same, engine is the same, power is the same.
You are not redlining at 6th, you are not redlining at 6th, you are not redlining at 6th.

It is not as straightforward as you are imagining in your head to estimate if the car will be slower or faster with different final drive. And, data shows top speed is not higher.

What else is there to say?

[ermax]

You do realize the car makes more power at higher RPMs right?

[Tokay444]

Originally Posted by gtengr

Yes, I have numbers and equations to back up my claim. I considered engine rpm, trans gearing, diff gearing, and tire size to get the speed of the car. 4.10 vs. 4.30 results in 167 rpm difference at 80mph in 6th.

The official claim is that top speed is drag limited to 134 mph. 4.30 gearing would put the engine a couple of hundred rpm's higher in the power band than the 4.10, which would allow the car to overcome incrementally more aero drag and rolling resistance.

Except I've hit over 240km/h, completely stock.

Originally Posted by mrg666

Of course, that is totally your decision and your car. How can I argue with that?

What you can argue, if you'd care to try, is your statement that the engine is working harder just because the RPMs are higher.
I'd care to counter that with actual load outputs.

[gtengr]

Originally Posted by Tokay444

Except I've hit over 240km/h, completely stock.

Again:

Originally Posted by gtengr

The actual number isn't all that relevant to my point. And on top of that, claiming a top speed higher than 134 makes my point more obvious by inspection of the speed vs. rpm vs. engine power plot.

The only legitimate counterpoint is whether the car can actually pull 6th gear. If it can't at stock power levels, then what I've been saying here doesn't necessarily hold up for a stock car. But, the justification is still correct, and it would help if you increased power enough to pull 6th.

[daskaman]

When I run out of gear I just shift in 7th....

In all fairness I am planning a whole carrier swap, possibly with axles if I find somebody with a young part out.

[Somerandom18]

Originally Posted by Tcoat

MPH vs KPH?


If they clocked you doing 148 MPH how do you still have the car?

Because he was a cool cop and only suspended my license instead of writing 148 on the ticket. MPH. He asked how fast I thought I was going. I said I honestly don't know. He asked again and I replied well over 100. He looked away facepalmed and stated my speed. Then went to write the ticket. I fully expected to lose everything at that moment. He came back with the ticket. And sent me on my way with a 95 mph in a 65 and a recommendation of selling the car.

To get to 148 it took a lot of empty road and a 30-35 degree Sunday morning.

Sent from my Pixel XL using Tapatalk

[nikitopo]

Originally Posted by ermax

Okay now I'm starting to think you are the one playing dumb. Reread all the posts in this thread and then return.

Edit: As explained several times. The higher final drive would put you higher in the rev band. The car makes power all the way to redline so the higher final puts you higher in the band producing more power. More power, more top speed. You agree that the car will accelerate faster. The gearing keeps the revs in the power band. Do you think this simply stops once you put it in 6th gear?

Originally Posted by ermax

You do realize the car makes more power at higher RPMs right?

You are missing an important point. With a lower final drive you can use a lower gear and you have more power.


Example:
My car can reach 225km/h on 5th gear. If I swap to a 4.55 final drive, then I'll need 6th gear to reach the same speed. Even with the changed ratio, the 6th gear will provide less torque comparing to 5th gear.


So, it depends in which gear the car could achieve the top speed. Was it on 5th gear? Then, you don't have a higher top speed with the changed final drive ratio. Was it on 6th gear and you didn't hit redline? Then, yes chances are that you 'll have a higher top speed.

[Tcoat]

Originally Posted by Somerandom18

Because he was a cool cop and only suspended my license instead of writing 148 on the ticket. MPH. He asked how fast I thought I was going. I said I honestly don't know. He asked again and I replied well over 100. He looked away facepalmed and stated my speed. Then went to write the ticket. I fully expected to lose everything at that moment. He came back with the ticket. And sent me on my way with a 95 mph in a 65 and a recommendation of selling the car.

To get to 148 it took a lot of empty road and a 30-35 degree Sunday morning.

Sent from my Pixel XL using Tapatalk

95 MPH = 154 KPH
65 MPH = 104 KPH

If he wrote a ticket for 95 in a 65 he would HAVE to impound you car since it is greater than 40KPK over the speed limit. No matter how nice he was he would have no choice.