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Unread 07-19-2010, 07:33 PM   #1
takeda54
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Power loss from 35's? & pwr mods

How much power loss can you expect from going to 35's from the stock tires(255/70/17) "32" on a stock JK X with 3.73 gears. I plan on doing exhaust and cold air intact with predator , I hope this will help. I have been told by a local shop this will be good up to 35 horses.

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Unread 07-19-2010, 08:04 PM   #2
fernjack
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Most guys on here will tell you to save your cash and use it for gears .....the intake & exhaust thing just doesn't make ponies on this engine . Probably would need a cam and a retune to be able to use the intake & exhaust . Are you auto or 6spd. ?
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Unread 07-19-2010, 08:08 PM   #3
stanware
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I went to 35" from stock and also got a Volant Exhaust and intake and there is power loss, it was only after my Superchips tune that I got some real power back.
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Unread 07-19-2010, 08:17 PM   #4
fan45acp
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Really save your money and REGEAR...
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Unread 07-19-2010, 08:25 PM   #5
GPV
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Yep regear it and be done with it.
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Unread 07-19-2010, 08:32 PM   #6
Benderff
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You will not lose any engine power by changing tires. (So why would you waste money fixing something that's not broken?) Changing tire size affects the rate your drivetrain can turn your tires. If you want to be able to turn the tires the same as before you need to regear the axles.
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Unread 07-19-2010, 08:33 PM   #7
MilitaryJK4455
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about a 20% power loss in take off and about a 5% loss in mid speed (2500 rpms runnin up to about 65) and then about a 15% loss in anything over 70-75mph. Thats about the best I can describe it in terms that ppl on the interwebz can understand.
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Unread 07-20-2010, 01:10 AM   #8
Armycop
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The Superchip can give you a couple more HP and a better throttle response, but regearing is the best way to get the engine in the sweet spot for power.
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Unread 07-20-2010, 01:16 AM   #9
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Yup, re-gear first. If itís an auto go with 5.13ís. Maybe even 5.38ís.
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Unread 07-20-2010, 01:37 AM   #10
JLC08JK
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Just to give a real world example; I just came back from a road trip on 35" tires and stock 3.21 gears. In fifth gear at 2k rpm it was at 65 mph, there was absolutely no power available to accelerate without down shifting into fourth gear. I ended up running 90% of the 600 mile round trip in fourth gear at 75 mph with an occasional shift to third to climb the hills.
I have the 4.88 gears and they will go in as soon as I get my ARB locker for the rear.
The Flash Pack could have helped but it won't change the rpm/mph ratio!
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Unread 07-20-2010, 02:08 AM   #11
MilitaryJK4455
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Quote:
Originally Posted by JLC08JK View Post
Just to give a real world example; I just came back from a road trip on 35" tires and stock 3.21 gears. In fifth gear at 2k rpm it was at 65 mph, there was absolutely no power available to accelerate without down shifting into fourth gear. I ended up running 90% of the 600 mile round trip in fourth gear at 75 mph with an occasional shift to third to climb the hills.
I have the 4.88 gears and they will go in as soon as I get my ARB locker for the rear.
The Flash Pack could have helped but it won't change the rpm/mph ratio!
With my 3.73's I just got back from a trip with 35's also... 4th gear at 65 im running 2500 rpms, I did have power to accelerate and I was getting about 18.5 mpg and I could go up to 5th gear and run about 2k rpm unless I was going up hill, then I would drop into 4th.... That shows you the change just up to 3.73's... I only have to hit 3rd gear when traffic got slow or I was decelerating.
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Unread 07-20-2010, 02:12 AM   #12
Warlord2
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screw gears, just buy a hemi and call it good
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Unread 07-20-2010, 01:20 PM   #13
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screw gears, just buy a hemi and call it good
Ok, but Iíll have to sell my kids first. Ooh, this is starting to sound better already.
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Unread 07-20-2010, 01:27 PM   #14
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Quote:
Originally Posted by MilitaryJK4455 View Post
With my 3.73's I just got back from a trip with 35's also... 4th gear at 65 im running 2500 rpms, I did have power to accelerate and I was getting about 18.5 mpg and I could go up to 5th gear and run about 2k rpm unless I was going up hill, then I would drop into 4th.... That shows you the change just up to 3.73's... I only have to hit 3rd gear when traffic got slow or I was decelerating.
i just got back from a 400 mile round trip on 35's with 3.73's too. I was only able to really put it in 6th gear down hill. but most of my time was spent in 5th and needing 4th up hills. You think you would get better gas milage in 4th gear revving higher than 5th? Probably what a 300-400 rpm difference? just because it would be "trying less" even though the rpm's were higher? i was at 15.8mpg's or so. but i was going up to the moutains...
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Unread 07-20-2010, 03:54 PM   #15
MilitaryJK4455
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Quote:
Originally Posted by Rafi View Post
i just got back from a 400 mile round trip on 35's with 3.73's too. I was only able to really put it in 6th gear down hill. but most of my time was spent in 5th and needing 4th up hills. You think you would get better gas milage in 4th gear revving higher than 5th? Probably what a 300-400 rpm difference? just because it would be "trying less" even though the rpm's were higher? i was at 15.8mpg's or so. but i was going up to the moutains...
It just depends on how you drive man... I try to run about 65-70 in fifth gear where I can and I drop to 4th for inclines to keep the motor from working too hard... good mpg's and giving it hell dont go together

Not to mention I was driving to the beach... Not too many hills, I was able to run 5th pretty much the whole way unless traffic lights or idiots ended up in front of me.
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