Any performance advice for 2.5 4-cylinder?
- Thread starter Moyock13
- Start date
Best performance advice sans forced induction? Stock sized tires in some lighter weight AT itires. Something like Goodyear Wrangler Trailrunners or something similar. I prefer the look of the stock steel wheels, but if you could go with a lightweight aluminum wheel even better. With my stock 9 hole steel wheels and a set of 235/75R15 ATs I can cruise pretty comfortably at 75-80 on the way to work (Dallas area) as long as I'm not facing a stiff headwind. Even then I can still cruise 75 just needs more throttle input.
I keep heavier MTs on a separate set of stock steel "sawtooth" wheels that I put on for trips.
I keep heavier MTs on a separate set of stock steel "sawtooth" wheels that I put on for trips.
If you have 33’s and are keeping them, go with 5.13. 4.56 and 4.88 are waste for a 2.5 manual on anything larger than 31’s. When you factor in that the stock tire was a 26.5”, you start to realize that even 5.13 barely catches you back up to “stock” on 33’s.
If you don’t insist on having 33’s, go back to stock size. Makes a massive difference and unless you will benefit from the large tires, they’re overrated. If you’re not wheeling it then large tires are only a detriment.
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redbullet
YJ Enthusiast
also of the old engine can have low cylinders compression, (the test and tool) my lawn mower can do 100 psi. Model A ford does 75.
it will have low power. (called basics) if this test fails.
I've reworked engines with top rings thin as razor blades. (radially)
or seen them packed in carbon so bad they where stuck. 1 or more cylinders.
it's old, things happen. the readings are also based on altitude. 3% loss per 1000feet.
par is 120 to 180 psi. sea level. the high number is from vast posters on line reporting, i'd say 150 is par.
the chart that is used by all private pilots is here for the corrections.
The test is based on CR, the Compression ratio, is what governs results (new engine broken in, after that wear happens.
the stock ratio is 9.1: (static CR)
The higher CR is the higher peak combustion pressure are (N/A) and power produced more, ( AFR good) (there are dynamic CR too, with cam effects)
Old tired engines are.
the math is all here.
bad rings , bad valves., worn or scored cylinders.
the cold engine the cylinders are not ROUND< so fails. ok>? the test must be done hot or warm, or do all 3 and learn. cold warm hot 180f
it will have low power. (called basics) if this test fails.
I've reworked engines with top rings thin as razor blades. (radially)
or seen them packed in carbon so bad they where stuck. 1 or more cylinders.
it's old, things happen. the readings are also based on altitude. 3% loss per 1000feet.
par is 120 to 180 psi. sea level. the high number is from vast posters on line reporting, i'd say 150 is par.
the chart that is used by all private pilots is here for the corrections.
equal is best. 10% variance is a goal (less best)
The test is based on CR, the Compression ratio, is what governs results (new engine broken in, after that wear happens.
the stock ratio is 9.1: (static CR)
The higher CR is the higher peak combustion pressure are (N/A) and power produced more, ( AFR good) (there are dynamic CR too, with cam effects)
Old tired engines are.
the math is all here.
bad rings , bad valves., worn or scored cylinders.
the cold engine the cylinders are not ROUND< so fails. ok>? the test must be done hot or warm, or do all 3 and learn. cold warm hot 180f
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those 33" will show 50mph on dash but is 57mph real, use a GPS $8 UPS speedo and see that.
stock speed sensor gears are wrong here.
stock speed sensor gears are wrong here.
the key part of this jeep engine for power, that loves to fail is the FPR. (of vast possibles) but is common this old.)
31psi at idle and 41PSI at WOT. (41 is what is possible) the vacuum in the plenum does that. Intake manifold center area plenum.
if the FPR fails , this is what happens:
if the vac hose pulled off ,fuel leaks out the FPR nipple the FPR is NO GOOD.
the FPR has 2 more failure modes
stucks open or closed as the love to do 15 years old or greater.
stuck open fuel pressure drops to say 31 all the time or even 20, and power is greatly lost. ( << hard cold facts)
stock closed the engine floods and CAT melts (2 problems now). with fuel even at 75psi can happen and is the PFR /pump shunt test spec in the FSM
a tech checks all that. The valve wears out and fails. they all do.
and the FSM leak down test.
and the injector balance test.
the enjectors can be sent out for ultrasonic reverse flow cleaning and checked for balance as a set.
finding power loss takes lots of testing.
engine , and EFI and brakes and the whole drive line.
31psi at idle and 41PSI at WOT. (41 is what is possible) the vacuum in the plenum does that. Intake manifold center area plenum.
if the FPR fails , this is what happens:
if the vac hose pulled off ,fuel leaks out the FPR nipple the FPR is NO GOOD.
the FPR has 2 more failure modes
stucks open or closed as the love to do 15 years old or greater.
stuck open fuel pressure drops to say 31 all the time or even 20, and power is greatly lost. ( << hard cold facts)
stock closed the engine floods and CAT melts (2 problems now). with fuel even at 75psi can happen and is the PFR /pump shunt test spec in the FSM
a tech checks all that. The valve wears out and fails. they all do.
and the FSM leak down test.
and the injector balance test.
the enjectors can be sent out for ultrasonic reverse flow cleaning and checked for balance as a set.
finding power loss takes lots of testing.
engine , and EFI and brakes and the whole drive line.