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new lift and tires

M

mitsumotors

NAXJA Forum User
Location
Winnipeg
i just put on my 3" rc lift and 31" bfg a/t's. i haven't really noticed a big difference in power loss but its a manual so should i be doing anything differently now when i drive(like shifting at different engine speed) or anything? also will changing the gearing get me better gas mileage? and i was also thinking of cutting out my cat and replacing it with a straight pipe. i figure that at about 450,000km it is pretty clogged up so do you guys think doing this will give me a noticable change in gas mileage?
 
get an ebay cat
 
Gutting a cat or removing a cat is a VERY touchy subject here. Leave the cat or get a high flow one. You need to regear, no exhaust setup on this earth will give you back the power that you've lost.
 
it won't really give you any noticable improvement. i would leave it. as for as your power loss, that's due to the larger tires.

you can push it a little harder and shift later, but in the end, the only way to get that power back properly is with new gears. my wife's TJ (also manual) had 31's for 2 years and just stopped using 5th gear because it didn't have any power left in 5th gear. then when she went to 33's, we also went with 4.56 gears and now it moves very very nicely.
 
Yeah, leave the cat, or replace it. One of my XJs is muffler-less, but it does have a cat!!!

Next step is to re-gear the axles.
 
I'm running 32's with 3.07 gears and stock 4.0 with AX15. It def. lost some power, but I REALLY noticed it when I hooked up to a trailer. I killed it trying to take off! Oh and 5th is completely useless unless I'm going down hill.
 
Keep the cat, a modern cat is not a flow restrictor.

as to the gears, I ran for a minute with the stock gears and 31's.
5th is worthless unless you're doing 75.
keep the RPms up around 2200-2500 for the best mileage.
 
really??? even when i was running 235's i would be sitting at about 1700rpm at 65mph. it always seemed low to me but is there a reason it may rev low like this? now that i have 31's on it sits at about 1600rpm at 65mph. any ideas?
 
bigger tires means less rotations to go the same distance. so going the same speed you are using less rpm's do go the same speed. at 65, you are probably doing closer to 70 mph. thats why it does that. with 32's on mine, at 70, im doin 75.
 
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