97 TJ 2.5L performance parts

That's what I'm thinking too, and backwards from what I said about the torque converter. Don't worry, this is Usenet.

Earle

Just checked and I received the build sheet. Looks like I have the stock gearing of 3.73. Here's a portion cut-n-paste from the build sheet:

DGA - All 3-Speed Automatic Transmissions DGDS - 3-Spd. Automatic 30RH Transmission DHAP - Lock-Up Torque Converter DHNS - Command-Trac Part Time 4WD System DJJS - Dana 30/186MM Front Axle DMEP - 3.73 Axle Ratio DRJS - Dana M35/194MM Rear Axle EAAC - All Engines EPE - 2.5L Power Tech I-4 Engine

Also, evidently it had floor mats too. Who knew.:) TJ

My build sheet said I had t> >>

The 3.73 was for improved gas mileage with the automatic. However, if you put 4.11, 4.56 or even more reduction in it, you will probably get better gas mileage and certainly better performance. This is because the "2.5L Power Tech I-4 Engine" actually likes RPMs. Take note of your engine speed on the tach at cruising speed, say 60 or 65 depending on personal style and road conditions. You can afford to have that change to 3,000 rpm and keep or even improve your current fuel economy. If you go over 3,000 you will begin to lose.

For the math, say you are thinking of going to 4.56 axles and you are currently turning 2,200 rpm at 60, which you find a comfortable speed. This is just a guess. Your new engine speed at 60 after the axle change is going to be 2,200 x (4.56/3.73) or 2,670 rpm, not too shabby. You won't be passing that many people, but it should feel like a performance increase. If your lock-up torque converter is actually working, then you should be able to rely on this calculation too, with no torque converter slippage at highway speeds. An axle ratio change is pretty drastic in terms of expense, but this calculation can show you what to expect. If you elect to change the tire size, you multiply by the old tire size, and divide by the new tire size, to get your new engine speed at a corresponding road speed. Don't forget to have your speedometer adjusted if you try any of these tricks.

Earle

Thank you Earle and others. I think I know what I need to do. At today's gas prices any mod I do that actually increase mileage will payback in no time. Also, if I can get even close to stock performance by regearing it would be worth it. Even now my TJ is very drivable around town. I foresee my offroading to be mainly limited to the beach although no guarantees! I will start with the 4.0 throttle body mod first (relatively cheap) and see what happens. Then I'll add the cat-back..see what happens. Then I will regear....see what happens. I'll post results after each mod for reference. I kinda like Bill Hughes post regarding the V8 or vortex....I'm considering that for when/if I blow-up the 4-banger or drive train. Y'all been a great help. Again, Thank you! TJ

When off roading, you have low range. You will have 'no' issues with slow running in low range.

Mike

If I were you I would re-gear first.

Well, I just now looked at the intake system (pulled it apart). I don't see how a spacer could work. The fuel is being injected after the throttle-body. I thought the fuel was injected at the throttle- body. Looks to be "multi-point" at each cylinder. Don't think I can improve that. The air intake system(filter, tubes, boxes) is..well..scary looking. I can see where a K&N type intake would help get air in better that the stock system. But, I will consider the cat- back first to get the air out more efficiently. Matt: you are saying you'd regear first. Do you think once I regear I won't need to do anything else? TJ

Don't waste your money on the throttle body spacer, just make sure you check and replace spark plugs and air filter frequently. God Bless America, Bill 0|||||| mailto: snipped-for-privacy@aol.com

I think it redlines at 5k or 6k. I have to agree with Matt about regearing first, but then again if you have a stock exhaust it needs replaced anyway.

Earle

Yes. The dash shows a redline just over 5K. Interesting about the intake info.

How about this stuff?

messagenews:45e62efc$0$16409$ snipped-for-privacy@free.teranews.com...

Dang!!! I was planning on inventing this stuff!

K&N Stuff. I have the complete test if someone wants it.

You have to be careful. If you buy enough of those 'wonder products' your fuel tank will start overflowing and become an environmental and fire hazard.