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post #1 of (permalink) Old 01-11-2007, 08:22 AM Thread Starter
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Need more horse power

A guy at work bought a 95 YJ, he installed a SOA, K&N air filter mod and BFGs 33s now he wants to know what he can do to get more horse power out of the pretty much stock 2.5L engine.
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post #2 of (permalink) Old 01-11-2007, 08:53 AM
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Re: Need more horse power

It may not be a case of Horse Power. It may be a case of the lift/larger tires are robbing power. Regearing the axles will restore the power band. Ask him if he suffered a "power loss" after installing the lift/tires.

There's really not a lot you can do to that 2.5L. Things that come to mind is a bored out throttle body, or a 4.0L throttle body swap, and a Jet-Chip (IMHO, not worth the money), tuned headers, low resistance cat converter. Most of these parts I'd not put on my Jeep.

Even if he installed a different engine, there's still the axle regearing question that would haunt the Jeep. That's where I'd start.
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post #3 of (permalink) Old 01-11-2007, 09:17 AM
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Re: Need more horse power

There is no substitute for cubic inches.....
Don't polish the turd.....
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post #4 of (permalink) Old 01-11-2007, 09:43 AM
 
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Re: Need more horse power

The best way to get more HP from a 2.5 is to run it at higher RPM- i.e.,install new gears. Chrysler has done a great job of getting the best performance from the little 4 cyl. The six also for that matter. Any bolt on performance enhancers are a waste of time and money IMO. Besides, any significant increase over stock performance will mean the rest of the drive train needs to be upgraded as well. If he has to have more power than a properly geared 2.5 can provide, he should buy a different Jeep.
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post #5 of (permalink) Old 01-11-2007, 09:49 AM
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Re: Need more horse power

Ditto x 4....
About the only 'bolt-on' device that will improve 'perceived' power is new gears. Right now he has 4.10 gears....going to 4.56 will restore the engine power band to what it felt like with stock tires....that is you best bang for the buck.

So...when your friend did the SOA...did he also put in a CV driveshaft or did he do the budget thing and drop the transfer case?
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post #6 of (permalink) Old 01-11-2007, 10:22 AM
 
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Re: Need more horse power

As much as I hate to agree with ANYTHING this cast of scoundrels says...[img]/ubbthreads/images/graemlins/ooo.gif[/img]

They would be correct about engine size.
An engine with a long stroke will give more torque.
An engine that has more cylinders (but shorter stroke) will give more horse power than torque...

In your friend's cases, there are really only two options,
One is to install a supercharger to wring the last few horse power out of the little engine,
The second is to just install a larger engine.

If I were doing the recommendation, I'd suggest a MODERN light weight V-6 engine instead of the antique, over weight Inline 6 cylinder or over weight older iron V-8 engines.

Light weight, fuel injected V-6 engines grow on trees in salvage yards and remanufacture shops.

Engine Mounts and adaptors are usually exactly the same things are their larger V-8 counterparts, so those non-wear parts are available. (Non-Wear means one time purchase)

Anyway, no real gains will be made from this point out with that little 4 cylinder unless you add a turbo or supercharger. You might squeeze out a few more HP with this or that gadget, but you are at the point of diminishing returns.
Meaning larger and larger money for smaller & smaller gains.
Force feeding the engine with a supercharger will make it put out V-8 power, but at the cost of shortened engine life, and the kits aren't really what I'd call 'Cheap'...
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post #7 of (permalink) Old 01-11-2007, 10:40 AM
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Re: Need more horse power

I concur - except maybe the scoundrels part.

Don't forget several big STP stickers!



JYG - what do you think of the Chev 4.3 in place of the 4.0? Significant difference worth the effort?
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post #8 of (permalink) Old 01-11-2007, 10:47 AM
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Re: Need more horse power

In my experience the 2.4 liter engine is not a piece of junk, it's just a bit too small for a Jeep. I say regear and keep the 4 popper. It will always get you where you are going...eventually!
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post #9 of (permalink) Old 01-11-2007, 12:25 PM
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Re: Need more horse power

regear is the answer.
the 4 bangers come with 4.10 gears. This isn't going to cut it with 33" tires and the 4 angry squirrels. You need 4.88's
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post #10 of (permalink) Old 01-11-2007, 07:40 PM
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Re: Need more horse power

Assuming that the guy has a 5 speed ..tell him to drive around in 4th gear for a week or two. That's about what 4.88 gears will feel like in 5th with the OD. If he has no issues starting off in 1st gear, then it's mostly a game of gear-train semantics. He loses the flexibility of 5 ranges ..but he's just starting off in a 5 step ladder with a higher 1st step and never uses the top one.

If he's happy with what 4th gear gives him in mastery of the highway, then he can opt for the gear change without any disappointment about what it will feel like (assuming he went for 4.88).

He can always use 5th when drafting big rigs on the highway.
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