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Author Topic: Questions on high rpms  (Read 1873 times)

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hyp7

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Questions on high rpms
« on: January 05, 2009, 04:18:51 PM »
Hello I have read a lot of guys run their 2.5L up to 4000 to 5000 rpms. I rarely get mine over 3500rpms. So am I lugging my jeep to low? Also what is redline on a 92 yj? I just changed out the Rod and Main bearings cause I kept hearing knocking. So I changed out the bearings it did help alittle but I still hear it every now and then.
I also put in the 4.0 throttle body , I did notice a little change but not much, Im planning on a electric fan mod also what is a good temp controller? I dont do any wheeling mainly street use.
Thanks for the help and info.
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BarneyJeep

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Re: Questions on high rpms
« Reply #1 on: January 05, 2009, 07:41:35 PM »
on the street i usually shift around 3500-4000

on the trail, thats another animal....for the most part its about the same, some of the hill climbs i've been known to keep the pedal down and let the rev limiter hit....it bounces 5200-6000

'98 2.5l TJ
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Offline chardrc

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Re: Questions on high rpms
« Reply #2 on: January 05, 2009, 08:29:21 PM »
on hills offroad i usually go 3rd gear at 4k.. on road i shift 4k to 3500.. would probably go higher but my motor is highmilage and was poorly maintained...
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1990 YJ 4cly, ax5, 2.5 inch BDS lift, 31 MTr\'s,  Powertrax-lockers all around, track-bars removed, boomerang shackles, warn m8000 winch, electric fan. [sold but not forgotten]

2007 jk Rubicon 2dr

jaywiz1977

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Re: Questions on high rpms
« Reply #3 on: January 05, 2009, 10:22:42 PM »
on the streets 3500 to 4 here. when i get the chance to play in the mud though it's to the floor and make as much mess as possible!! except for the deep stuff then it'sall depending on the situation! i have been know to run her to 5k when i got that a**hole at the light on my rear with the brights on and in the big hurry!
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YJmechanic

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Re: Questions on high rpms
« Reply #4 on: January 05, 2009, 11:38:28 PM »
it depends on your setup,  i run high rpms cause i built my motor for high rpm,  when i was stock i don't think i ever went over 6 at best,  now i hit 72 but still run around 25-3 just driving around
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Offline Jeffy

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Re: Questions on high rpms
« Reply #5 on: January 06, 2009, 03:38:18 PM »
I agree, it really depends.

My engine is set up for more mid range so I try to keep it in that powerband.  My power really comes on strong when I get to 2700rpm and will pull to around 4000rpm.  Optimality,  you want to make sure you're shifting close to the engine rev limit so when you shift, you'll be well withing the powerband for the next gear.  Changing tire sizes and gears can throw this off though.  Not to mention the added ballast that we bolt onto our Jeeps.

It currently doesn't have much more to give past 4000rpm.  When I ran my conical filter setup, I was able to rev higher but I didn't have the low-mid that I wanted.  Same goes for my exhaust.  They did give me more top end but anything over 80mph really requires your full attention.  I'd be fine with a top speed of 75mph and be in the mid-high end of my powerband.  Right now, I'm geared too high so I'm turning too few RPM's in 5th and too much in 4th for my liking.  I'd have to be doing 80MPH to start to get back into my powerband in 5th.  Problem is my engine runs out of power in 4th to get it up to 5th in high wind situations.

Someday I'll have 5.38's or lower to fix this.  Then I'll probably do something dumb like move up to 37's.  :lol:
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YJmechanic

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Re: Questions on high rpms
« Reply #6 on: January 06, 2009, 11:24:56 PM »
you know jeffy i think i would do the same just looking at history,  37 flashed as an idea the other day too
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BarneyJeep

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Re: Questions on high rpms
« Reply #7 on: January 07, 2009, 01:38:35 PM »
the thing that kills me about the TJ 2.5 is redline is 5150, but according to the factory peak HP is reached at 5250...100 RPM PAST redline...
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Offline Jeffy

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Re: Questions on high rpms
« Reply #8 on: January 07, 2009, 01:46:32 PM »
You can edge into red.  100RPM isn't that much.
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"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

hyp7

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Re: Questions on high rpms
« Reply #9 on: January 07, 2009, 02:52:04 PM »
So i went for a little cruz today and I was going into the wind, is it ok to just stay in 4th gear ? I could do around 60mph in 4th gear at around 2700rpms But when I would shift into 5th I would slowly drop to 2300rpms and start loosing speed so I just ran it in 4th for a few miles. and on the way back the wind was at my back so i was able to run at 60 to 65 in 5th gear no problem. When I was running i 4th aginst the wind i still had plenty of gas peddle left so just to let you know i wasnt floored.
So tell me what ya think.
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Offline jfrabat

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Re: Questions on high rpms
« Reply #10 on: January 07, 2009, 03:17:36 PM »
Quote from: hyp7 on January 07, 2009, 02:52:04 PM
So i went for a little cruz today and I was going into the wind, is it ok to just stay in 4th gear ? I could do around 60mph in 4th gear at around 2700rpms But when I would shift into 5th I would slowly drop to 2300rpms and start loosing speed so I just ran it in 4th for a few miles. and on the way back the wind was at my back so i was able to run at 60 to 65 in 5th gear no problem. When I was running i 4th aginst the wind i still had plenty of gas peddle left so just to let you know i wasnt floored.
So tell me what ya think.

Before I regeared to 4.88, I was running with 4.10 and 31" tires, and any uphill incline or headwind would cause me to have to drop to 4th.  As it turned out, I learned that keeping the Jeep in 4th not only left some pedal, but also gave me better gas mileage (of course, I would use 5th when I was driving WITH the wind).  So go ahead and use 4th all you want, you wont break anything.  Besides, with 4.88, I run at about 3K rpm's in 5th at 65 mph.  The little 4-banger can drive all day at 3K and not even blink!
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'94 YJ 2.5L with 4" RE lift, Superwinch EPi9.0, FoMoCo e-Fan, SD30 and SD35 w/ARB-5.13, 165A alt., 33" BFG KM2 on 15" AR wheels, Sony sound system, Pavement Ends Hardtop, Hydroboost

Offline Jeffy

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Re: Questions on high rpms
« Reply #11 on: January 07, 2009, 03:24:21 PM »
Quote from: hyp7 on January 07, 2009, 02:52:04 PM
So i went for a little cruz today and I was going into the wind, is it ok to just stay in 4th gear ? I could do around 60mph in 4th gear at around 2700rpms But when I would shift into 5th I would slowly drop to 2300rpms and start loosing speed so I just ran it in 4th for a few miles. and on the way back the wind was at my back so i was able to run at 60 to 65 in 5th gear no problem. When I was running i 4th aginst the wind i still had plenty of gas peddle left so just to let you know i wasnt floored.
So tell me what ya think.

Running at 2700rpm is not an issue.    If you start feeling a shutter as the engine has trouble keeping pace then downshift.  On I-5 at the Grapevine, I've had to downshift into 3rd to stay at 50-55mph and was reving around 3500-4000 the whole time...  Fun, fun, fun... :lol:
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"If the motor car were invented today, there is absolutely no way that any government in the world would let normal members of the public drive one."

Offline chardrc

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Re: Questions on high rpms
« Reply #12 on: January 07, 2009, 04:21:21 PM »
Quote from: BarneyJeep on January 07, 2009, 01:38:35 PM
the thing that kills me about the TJ 2.5 is redline is 5150, but according to the factory peak HP is reached at 5250...100 RPM PAST redline...

I think the original jeep 4banger, "go devil" had its peak horsepower 400rpm above redline.... :weee:
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1990 YJ 4cly, ax5, 2.5 inch BDS lift, 31 MTr\'s,  Powertrax-lockers all around, track-bars removed, boomerang shackles, warn m8000 winch, electric fan. [sold but not forgotten]

2007 jk Rubicon 2dr

Offline chardrc

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Re: Questions on high rpms
« Reply #13 on: January 08, 2009, 11:58:05 AM »
Quote from: chardrc on January 07, 2009, 04:21:21 PM
I think the original jeep 4banger, "go devil" had its peak horsepower 400rpm above redline.... :weee:

my bad i was thinking about the hurricane f head that peaked 800rpm above redline according to wikipedia...
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1990 YJ 4cly, ax5, 2.5 inch BDS lift, 31 MTr\'s,  Powertrax-lockers all around, track-bars removed, boomerang shackles, warn m8000 winch, electric fan. [sold but not forgotten]

2007 jk Rubicon 2dr
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