JEEPERCREEPER
NAXJA Forum User
- Location
- Omaha, soon to be Arizona
For a '89 4.0, non-HO, 5 speed, best optium performance at 70 mph should be what, 2500-2800 rpm's???? What is "red line" for that engine, 5,000 rpm's???? thanks
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Power band/Red line
- Thread starter JEEPERCREEPER
- Start date
jjvande
NAXJA Forum User
- Location
- Albuquerque NM 505 burque
i have 31's and 4.10s in my '88 and i run at 2850 on the highway...not sure how fast im going at that RPM, but its got great power. I think that anything below 2500-2600 is lugging it on the highway. Many say that the 4.0 should have no problem running @ 3000RPM on the highway, and i dont doubt it. but at 3000 rpm, the jeep sounds insane with the flowmaster and i dont want to be going that fast in 5th (u-joints dont like it either). I run it at 3000 in 4th to pass on steep grades.
-J
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Dr. Dyno
NAXJA Forum User
- Location
- Al Ain, UAE
JEEPERCREEPER said:
Redline for the Renix 4.0 is indeed 5000rpm. Since you have a 5-speed, aim for something like 2400rpm at 70mph in 5th gear. That's the peak torque rpm. This gearing should make highway cruising relaxed with good fuel economy and acceptable response in 5th gear.
Buck Jackson
NAXJA Forum User
- Location
- Vancouver Island, Canada
How is that on fuel? Seems like it would be a guzzler on long trips...jjvande said:
- Location
- Foresthill, CA
I can confirm that the Renix system bounces off of a rev limiter of some sort (I think it cuts fuel, not spark) at about 5,350 - 5,500. 
I'm usually kinda busy driving when it's bouncing off the limiter, so I'm not sure of the precise RPM.
2,800 RPM, which is about 75 mph for me, can get me 16-17 mpg, in the flats, on 35's and a fully loaded rig.
I'm usually kinda busy driving when it's bouncing off the limiter, so I'm not sure of the precise RPM.
2,800 RPM, which is about 75 mph for me, can get me 16-17 mpg, in the flats, on 35's and a fully loaded rig.
jjvande
NAXJA Forum User
- Location
- Albuquerque NM 505 burque
i get 15mpg around town...at 2700-2900 on freeway i get 20mpg or so.
