Topic: What is the best way to get more Top End?

[SDentone]

1990 YJ 2.5L 120,000 miles on the engine.  What can I do to get more power for climbing hills on the street with out loosing the torque needed for off road?  Be gentile I am a newbie with Jeeps and DIY projects.

My first though was to change some body parts for Fiberglass parts.  

1990 Stock YJ No upgrades on this thing......YET.

[Jeffy]

1990 YJ 2.5L 120,000 miles on the engine.  What can I do to get more power for climbing hills on the street with out loosing the torque needed for off road?  Be gentile I am a newbie with Jeeps and DIY projects.

My first though was to change some body parts for Fiberglass parts.  

1990 Stock YJ No upgrades on this thing......YET.

Well, I'd consider the TCG 9lbs inertia ring.  It will add more mass to flywheel which will help keep it's RPM's more constant when going up hills and what not.  It won't increase the top end though.

Actually, there isn't much on the top end.  I rev up over 4000rpm's so I can keep the RPM's high when I'm forced to downshift.  The mods I've got on my Jeep make the engine run relitively smooth at higher RPM's which is really nice.  It used to make a lot of noise and had a vibration at higher RPM's which was a bit annoying.

Still gears are your friend.  Gearing lower will make a huge difference.

[chardrc]

i read all this talk about pushing the 4banger over 4 grand.. but when i drive my jeep i can never getmusellf to go over 4 grand.. i feel like im pushing it to much and its going to blow.... and when i push it up to 4 grand i get a burning oil smeel afterwords :roll: ..... on top of that my motor is in need of a rebuild...

[SDentone]

OK TCG is?... Again please forgive my ignorance.  I have talked to alot of people about engines and such but I have never walked the walk so to speak.

[Jeffy]

OK TCG is?... Again please forgive my ignorance.  I have talked to alot of people about engines and such but I have never walked the walk so to speak.

Sorry about that.  Tri-County Gear.  They sell a 9lbs inertia ring for around $150.  It involves taking the transmission down so you might not want to do this unless you're going to replace the clutch since the tranny will have to come out anyway.

I still haven't done this but it's one of the things I'll consider when I have to do a clutch.

As for not being able to rev to 4000rpm.  You're just not trying.  There is no reason you shouldn't be able to rev the engine to the limiter.  Although on a older/higher mileage engiine you might not want to rev it as high for fear of breaking a rod or springing a leak in the headgasket.

[chrisfranklin]

Best way to get more top end?

Swap in a late-model Ferrari 12 cylinder.   After that, your top end problems will be over.

[superman1456]

go with a 4.0 if your goin to rebuild keep the 2.5 logo on the jeep and you will be happy with it been there done that it works out well

[Bounty Hunter]

Swap in one of these, 4banger from the Honda S2000 redlines around 11K.

Consider regearing for optimal power range while on the highway, generally means lower gears with the 2.5L engine.  Also check out a perfomance cam to bump power up on the top end, install new valve springs for the added lift, and a double-roller timing chain.  Header would help as well.

I don't think the inertia ring will do a thing for top end, it'll have the same effect as adding heavier tires, robbing power and slowing the engine.  I think the only place the inertia ring helps is when bouncing off idle while wheelin, keeping the engines momentum between power strokes.

[Jeffy]

I don't think the inertia ring will do a thing for top end, it'll have the same effect as adding heavier tires, robbing power and slowing the engine.  I think the only place the inertia ring helps is when bouncing off idle while wheelin, keeping the engines momentum between power strokes.

Actually it won't slow the engine.  Typically what happens when you install one, the engien will not drop RPM's as fast as it used to and you end up chirping the tires till you get used to it.  Onroad, it's not that noticable other then keeping the RPM's steady.  Like I said, this will help a bit when trying to maintain RPM's on the highway a bit.  It's different then adding larger tires, since the weight is not on the engine itself.  But like you said, it will help keep the engine from dying when idling very low while in gear.

[Bounty Hunter]

Seems to me that it's more power robbing weight on an already anemic engine.  And I compared it to heavier tires, not larger, to keep things in perspective.  I only see the benefits off idle, but I've never ran one either.

[Jeffy]

Seems to me that it's more power robbing weight on an already anemic engine.  And I compared it to heavier tires, not larger, to keep things in perspective.  I only see the benefits off idle, but I've never ran one either.

Well, they do take up some of the off the line power but once you're going you won't notice it as much.  Like I said, it will help keep from losing RPM's as fast when at speed but it's no replacement for more overall power.   A friend of mine runs one with his 2.5L in downtown SF and has no complaints.  There should be a few others here who have them.  But we're really straying now.

Go with gears like we both stated, SDentone.  It will make the biggest difference and you'll be happy...until you go with larger tires.  :lol1:

[SDentone]

OK Maybe I was a little vague on the question.  So let me restate...  I want to climb mountain passes without dropping to 35 MPH and not loose low-end power for off road.  Am I asking too much out of this engine?  Also I was thinking a little subtler than a Ferrari engine replacement. (Funny)  Would making the body lighter help?  Would adding a good after market header, and high flow CAT help?  Maybe a new air filter.  Is there a good tune up kit out there?  I use this Jeep to drive to work and off road so it has to be more practical for now.  Maybe next year I will lift it 8" and put 33s on it and bla bla bla....

[Mozman68]

re-gear to 4.88's...or lower if you have D44's or the like.

[Bounty Hunter]

Sounds like you're running stock size tires, so you don't want to regear too deep or highway performance will suffer, rpms will be way too high.

You can add things like a cat-back exhaust, 4.0L throttle body and spacer, airtube and conical filter, electric fan, etc.  You can even go as far as adding a performance camshaft.  All told I think you're expecting too much from the 2.5L and the aerodynamics of your rolling brick.  (think supercharger).

My 2.5L has most of the above mentioned mods (short of a blower) and it does fairly well on the hills.  I'm running 32" tires and can hold some pretty good grades at 50 or 60mph with stock 4.11 axle gears.

[SDentone]

Thanks for the info.  Yes I am running 100% stock for now.  The clutch was replaced at 80,000 and the Head gasget at 100,00 or so.  I am not expecting to do 70 through a mountain pass but 50 0r 55 would be nice.  The pass I go through is 5 lanes wide anyway.  I can hang in the slow lane.  So what kind of performance changes can I expect with a new cat and exhaust, Air filter system and Throttle body?