hemi vs. cummins
05-15-2006, 10:31 AM
#16
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To digress a might (to 1967), my rrommate in my freshman year of college had a new Dodge Coronet with hemi. 7 liter variety. Now that was an acceleration machine! Didn't have aw s**t handles but sure could have used them 
05-15-2006, 04:15 PM
#17
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Do HEMI engines in the 2500 and 3500 series trucks have the configuration where the motor runs on 4 cylinders until the motor gets put under a load? If so, call me crazy, but that could get a little hairy if you are pullin a 10k trailer and need to get on it and go. I know I've been hard on these HEMIs, but come on, if I wanted a gasser that got 14 MPG on a good day, I'd get an old school 8.0 L V10 that runs on all 10.. all the time.
05-15-2006, 05:13 PM
#19
Originally Posted by v8440
Hey, you guys want an example of what the hemi can do in a vehicle a little lighter than the AVERAGE truck they come in?
My best friend has an standard cab shortbed 2wd. The textbook configuration for good acceleration. It also has the lighter 17" wheels, and limited slip. It has the 3.55's instead of the 3.92's, which in retrospect may be hurting it slightly. I at first thought the 3.55's might be better for such a light truck, but after watching it run, I now think a little more gear would still help it.
Anyway, here's what's been done to it:
1. Cat back dual exhaust, made and bent by local muffler shop. NOT mandrel bent.
2. Remove air filter at track.
3. Remove tailgate and spare tire at track.
It has run a 14.85 at about 87 mph! This is on the stock original tires. There is no programmer, no nitrous, nothing. The only modifications are the ones I just posted above.
I don't care who you are, that's riding for what it is. It's his girlfriend's daily driver, so it gets used a lot.
My best friend has an standard cab shortbed 2wd. The textbook configuration for good acceleration. It also has the lighter 17" wheels, and limited slip. It has the 3.55's instead of the 3.92's, which in retrospect may be hurting it slightly. I at first thought the 3.55's might be better for such a light truck, but after watching it run, I now think a little more gear would still help it.
Anyway, here's what's been done to it:
1. Cat back dual exhaust, made and bent by local muffler shop. NOT mandrel bent.
2. Remove air filter at track.
3. Remove tailgate and spare tire at track.
It has run a 14.85 at about 87 mph! This is on the stock original tires. There is no programmer, no nitrous, nothing. The only modifications are the ones I just posted above.
I don't care who you are, that's riding for what it is. It's his girlfriend's daily driver, so it gets used a lot.
Put the air filter BACK in and it will run faster. A Mass Air Flow sensor needs the air filter to "smooth" the air going past the sensor. If no filter, the air is "turbulent" and causes the computer to "freak" out.
05-15-2006, 06:10 PM
#20
I'll tell him to try it with the filter back in. I see what you're saying with the mass airflow sensor.
On towing with the mds, it's a nonissue. I had it on the magnum rt I used to have, and it kicks the other 4 cylinders back in so fast you can't really feel it. Maybe just a tiny TINY bit if you concentrate on looking for it. DC says it reactivates the cylinders in 4 thousandths of a second. Judging by how it feels, I believe them. In fact, it's quite likely that it would rarely if ever deactivate them in the first place towing much of a load.
On towing with the mds, it's a nonissue. I had it on the magnum rt I used to have, and it kicks the other 4 cylinders back in so fast you can't really feel it. Maybe just a tiny TINY bit if you concentrate on looking for it. DC says it reactivates the cylinders in 4 thousandths of a second. Judging by how it feels, I believe them. In fact, it's quite likely that it would rarely if ever deactivate them in the first place towing much of a load.
05-15-2006, 06:12 PM
#21
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I'm not 100% positive but I'm pretty sure a bone stock HEMI will out run a bone stock CTD in an unloaded 1/4-mile drag. I know my Titan would beat my MegaCab, and the Titan and HEMI are very closely matched. But like others have said, throw 1000 lbs in the back and the CTD will win every time!
05-15-2006, 07:15 PM
#22
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I can give you an honest 1st hand comparison. I've owned four Cummins powered Rams. My '01.5 and '03 standard output 250hp/460ftlb Cummins both felt pretty lively after turbo lag and would occasionally break traction on a launch. I got 17-18.5mpg city with all four Cummins Rams. 19 hwy 70mph and 10.5mpg towing our 5th wheel. They both towed our 10,040 lb 5th wheel pretty well. 65-70 on flats to mild rolling hills and an occasional bog to 58mph so the '03 could downshift to 3rd without over revving the engine with it's 4.10 rear end. I traded the '03 for my '05 Hemi powered Ram after fighting with DC over the dreaded driveline vibe for 44k miles. The '05 is a carbon copy duplicate of my '03 but with Hemi and 5-45RFE instead of the Cummins and 47RE. Even the 10.5" AAM is the same but a 3.73 instead of 4.10 with the Cummins. The Hemi gets 14~ city, 17-18 hwy at 70mph and 8.5~ towing the same 5th wheel 65-70mph over the same paths the Cummins towed it. If you were deaf and had no tach, you would not be able to tell the difference towing our 5th wheel. Until you reach a steep hill. The 460 Cummins has enough torque but, can't rev high enough to apply it at 70mph in direct. So it must bog down in O/D until it can downshift. The Hemi will downshift to 2nd at 65mph and accelerate to over 70mph at 5000rpm+ on the same steep hill. Only did it once. I'm happy to let it bog to 60~mph and downshift to 2nd for a much less cringing 4200rpm where it pulls like a champ and sounds comfortable. So in a nutshell, the Hemi will outrun the standard output 250/460 Cummins empty and towing 10k lbs. But it's close enough towing that there's no doubt the HO Cummins or a bombed SO Cummins would walk away from the Hemi towing 10k lbs. The Hemi and the HO make comparable HP at their peaks but, 2900rpm with the Cummins is much more reasonable on a grade than 5400rpm with the Hemi. It's above my cringe factor rpm. So for me, the 300hp the Hemi makes at 4200rpm is it's peak. The Hemi, even in the heavy 2500, will readily rip the tires loose on a launch and leap to 45mph in 1st gear, then snag 2nd to over 70mph. Don't do that much either.
My next truck will likely be a HO Cummins. The Hemi's fun and lives up to the hype for a smallbock gasser but, the Cummins has the same allure the Harley has. Who cares if the Ninja is faster...
My next truck will likely be a HO Cummins. The Hemi's fun and lives up to the hype for a smallbock gasser but, the Cummins has the same allure the Harley has. Who cares if the Ninja is faster...
05-15-2006, 11:54 PM
#23
Originally Posted by SSminnow
Put the air filter BACK in and it will run faster. A Mass Air Flow sensor needs the air filter to "smooth" the air going past the sensor. If no filter, the air is "turbulent" and causes the computer to "freak" out.
Wait a minute-Houston, we have a problem. Namely, that the hemi doesn't HAVE a mass airflow sensor. It's a speed density system. I just realized this a while ago, and had to check around some to make sure I wasn't remembering wrong. Sure enough, when my wife got home from work, I checked-none there.
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