What Mods to get some power back?
04-27-2015, 05:04 PM
#21
Chive So Hard
http://tire-size-conversion.com/gear-ratio-calculator/
^^^ that will give you the mechanical advantage equivalent ratio - 'back to stock' as they say.
You then need to figure out the per corner (wheel and tire) weight increase over stock. If the weight gain is significant, my recommendation would be to step up one size to help spin the extra rotational mass.
So if the calculator above says 4.10:1 and you added say 15+lbs per corner, I would bump the gearing to 4.56:1
It doesn't take much increase in rotational mass to take away that 'snappy' feeling on acceleration.
^^^ that will give you the mechanical advantage equivalent ratio - 'back to stock' as they say.
You then need to figure out the per corner (wheel and tire) weight increase over stock. If the weight gain is significant, my recommendation would be to step up one size to help spin the extra rotational mass.
So if the calculator above says 4.10:1 and you added say 15+lbs per corner, I would bump the gearing to 4.56:1
It doesn't take much increase in rotational mass to take away that 'snappy' feeling on acceleration.
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WarSurfer (04-27-2015)
04-27-2015, 05:12 PM
#22
http://tire-size-conversion.com/gear-ratio-calculator/
^^^ that will give you the mechanical advantage equivalent ratio - 'back to stock' as they say.
You then need to figure out the per corner (wheel and tire) weight increase over stock. If the weight gain is significant, my recommendation would be to step up one size to help spin the extra rotational mass.
So if the calculator above says 4.10:1 and you added say 15+lbs per corner, I would bump the gearing to 4.56:1
It doesn't take much increase in rotational mass to take away that 'snappy' feeling on acceleration.
^^^ that will give you the mechanical advantage equivalent ratio - 'back to stock' as they say.
You then need to figure out the per corner (wheel and tire) weight increase over stock. If the weight gain is significant, my recommendation would be to step up one size to help spin the extra rotational mass.
So if the calculator above says 4.10:1 and you added say 15+lbs per corner, I would bump the gearing to 4.56:1
It doesn't take much increase in rotational mass to take away that 'snappy' feeling on acceleration.
I'm reluctant to suggest 4.88's or deeper because most folks would just scoff and discount the suggestion - because they too haven't considered the more esoteric effects of going 'big'.
Cheers
Vladsky
04-28-2015, 05:48 AM
#23
Moderator (Ret.)
And, after doing this type of a differential gear change, don't be alarmed when your MPG drops significantly! In order to spin those tires, the rpm's go up, which simply put, means the engine is working harder to produce the same speeds you had with the smaller and lower rotational mass rims/tires you used to have.
And if you tow a trailer, that too will change, but the higher gear will actually help tow weight acceleration, but top end suffers all around.
And if you tow a trailer, that too will change, but the higher gear will actually help tow weight acceleration, but top end suffers all around.
04-28-2015, 05:55 AM
#24
Senior Member
And, after doing this type of a differential gear change, don't be alarmed when your MPG drops significantly! In order to spin those tires, the rpm's go up, which simply put, means the engine is working harder to produce the same speeds you had with the smaller and lower rotational mass rims/tires you used to have.
And if you tow a trailer, that too will change, but the higher gear will actually help tow weight acceleration, but top end suffers all around.
And if you tow a trailer, that too will change, but the higher gear will actually help tow weight acceleration, but top end suffers all around.
I realize I have a 6sp vs a 4sp but at 80mph my rpms are at 2200. Stock at 80 they were 1800ish. That's with 4.88s. I drive 90 miles per day in my highly modified Raptor and I lost 2mpg. I would have lost 2mpg without the 4.88s - just from the increased weight and rolling resistance.
Edit: don't forget that the first bump in gearing is offset by the increase in tire size - so very little if any rpm change. The +1 will impact rpms but typically only by ~200rpms.
If stock gearing is 3.55 (assuming a ~33" equivalent stock) and you add 35" tires, 3.73s will put you close to stock - I say close because the actual gearing to match stock would be like 3.62 and you can't get 3.62s.
Last edited by WarSurfer; 04-28-2015 at 07:17 AM.
04-28-2015, 10:25 AM
#25
Senior Member
So the "back to stock" ratio of a 3.73 and 35s is relatively the same? Good to know. I've been told that, to run 35s effectively I would need 4.10s or 4.56s. I appreciate the input.
04-28-2015, 12:01 PM
#26
Senior Member
4.10s would be the +1 option
04-28-2015, 12:40 PM
#28
04-28-2015, 08:24 PM
#29
Senior Member
I'll add another vote for gears before tuner. The tuner can't change physics, but the gears can. You're tranny is working hard to push those tires around and a new gear set will definitely take some of the load off and get you out of the hole a little quicker.