Do you have a dyno chart for the 2.8? Which calc are you using? I like Grimm Reapers out of all of them.
What else will I need for a lift to fit 35s?
- Thread starter NDSpeed
- Start date
Do you have a dyno chart for the 2.8? Which calc are you using? I like Grimm Reapers out of all of them.
OP
OP
I'm not failure with the 2.8, but that seems like a high RPM. Based on my experience with other diesel engines that size, they tend to fuel-limit around 2700-3000. Like Wildman said, you really need to find a decent dyno chart and know at what RPM it will fuel-limit.
@NDSpeed
Engine doesn't matter, which is why it's not an option on GrimmJeeper Gear Ratio Calculator. All that matters is your transmission, tire size, and gear ratio. Based on the NSG-370 and 35's figured in below, I'd go with 4.88 but wouldn't mind 5.13 either.
Here's the chart with 4.11 vs 4.88 (see rpm's at 70mph)
Here's the chart with 4.88 vs 5.13 (see rpm's at 70mph)
Engine doesn't matter, which is why it's not an option on GrimmJeeper Gear Ratio Calculator. All that matters is your transmission, tire size, and gear ratio. Based on the NSG-370 and 35's figured in below, I'd go with 4.88 but wouldn't mind 5.13 either.
Here's the chart with 4.11 vs 4.88 (see rpm's at 70mph)
Here's the chart with 4.88 vs 5.13 (see rpm's at 70mph)
Engine absolutely matters. As was stated above, it is all about where the engine makes power, and what is the best rpm operating range. My guess is that the power curve on that diesel is very different than the 4.0 - starts at a lower rpm, and ends at a lower rpm.
Why does Grimm Jeeper not bring engine into the equation? They certainly aren't set up just to deal with the 4.0. It's for all engines.
@NashvilleTJ
I agree that the engine makes power at different rpm's, so, how would the OP find out where that power band is on his Cummins 2.8? We 4.0 guys like 2700-2800rpm's+
I agree that the engine makes power at different rpm's, so, how would the OP find out where that power band is on his Cummins 2.8? We 4.0 guys like 2700-2800rpm's+
OP
The 2.8 might not be able to even get to those RPMs. As I stated above, many diesel engines are fuel-limited below 3000 RPM (rev limiter for gas engine). So if he gears 5.13 and needs to spin 2800 RPM+ to achieve 65 mph, well his 2.8 just can't do it. That's why the engine and related specs matter. Grimm Jeeper is just a calculator. That's why it even calculates 1st gear at 70 mph (4.88 = 14626 rpm)
Without looking into your particular build, I put a sheet on my 'rebuild" page that is fairly comprehensive. I moved from 33's on around 3" of lift to 35's on 5+ inches.
https://wranglertjforum.com/threads/a-rebuild-of-mirustyjeep.54728/post-955592
I already had adjustable control arms and adjustable trackbars.
https://wranglertjforum.com/threads/a-rebuild-of-mirustyjeep.54728/post-955592
I already had adjustable control arms and adjustable trackbars.
First off I'd ask what speed you'll be running at on the freeway? You keep listing RPM's for 65 MPH while I'd guess most times you'd be running at least 70 MPH.
Looking at the info they offer on their website and their gearing calc I'd be shooting for around 2500 RPM's at your cruising speed you plan to run at.
Use this Gear Calculator and when you're putting in ire size take off 1/2" since most tires do ever run true to size. Play around wiht some different gear ratios and see what is going to fit your application the best.
http://www.grimmjeeper.com/gears.html