Daveinet wrote:
Total weight the powertrain is pulling up the hill. It was intended as a point of reference. The 502 is not stock. If I run in 3rd, my drive wheel torque is the same as a DP with 1200 ft-lbs of torque.
Per the 410 HP hemi, you could easily put it in a coach weighing 30K+ lbs. It would accelerate fine. If you measure performance with your speedometer, it would hold speed on the the hills. That is indisputable fact. But so that no one is mislead, you would probably want to gear it, so it was turning about 3K RPM at 65 mph, which is very similar to how the early 80s 454s were setup. A setup like that would work just fine. 3K RPM would give you the same amount of drive wheel torque as a diesel turning 1500 RPM with 860 lb-ft of torque - a pretty common spec amongst large DPs. (assumption of both engines running in top gear)
hardtobe wrote:JetAonly wrote:
Yikes! I was hoping someone that knows their engines would post the physical difference between engines when used to slow the MH down. So I'll take a stab at it.
The diesel has no throttle plate, so it always has full volumetric capacity of air passing through it. This means at idle power it is still compressing all the air it can process. This is further aided by exhaust brakes and Jake brakes. Both act as a restriction in the exhaust of the engine. This can approach 80% of the HP the engine is capable of producing. This leaves the service brakes with their complete reservoir thermal capacity for an emergency stop, if operated correctly.
Gasoline engines at idle power do not process all the air they are volumetrically capable of. They have a throttle plate and they are tied to the correct fuel to air mixture to enable them to fire. If they do not have ~14 to 1 air to fuel the spark won't ignite them. They develop far less braking HP for that reason.
It is good technique with heavy vehicles to use something other than the service brakes to keep speed under control down hills.
JET I agree and that why I say all the DPMH guys whom cliam there not in need of ExB or EngB are nuts.I says lets all go to a 3 mile 6-7% grade and go down at 55MPH and see whom has overheated air brakes at the bottom??
hardtobe wrote:wildmanbaker wrote:
One note on the Dodge Hemi, they are awful thirsty when you work they semi hard. I dough you could afford to feed one in a MH. Most of the pickups with the hemi complain about barley getting 10 mpg.
As stated there is no way a dodge hemi 410HP gas engine would ever ever be used realistically for many many reasons in a 30K plus 40ft 4 slide Motorhome and anyone whoms believes different knows nothing about weight and torques and the real world.
JetAonly wrote:
Yikes! I was hoping someone that knows their engines would post the physical difference between engines when used to slow the MH down. So I'll take a stab at it.
The diesel has no throttle plate, so it always has full volumetric capacity of air passing through it. This means at idle power it is still compressing all the air it can process. This is further aided by exhaust brakes and Jake brakes. Both act as a restriction in the exhaust of the engine. This can approach 80% of the HP the engine is capable of producing. This leaves the service brakes with their complete reservoir thermal capacity for an emergency stop, if operated correctly.
Gasoline engines at idle power do not process all the air they are volumetrically capable of. They have a throttle plate and they are tied to the correct fuel to air mixture to enable them to fire. If they do not have ~14 to 1 air to fuel the spark won't ignite them. They develop far less braking HP for that reason.
It is good technique with heavy vehicles to use something other than the service brakes to keep speed under control down hills.
wildmanbaker wrote:
One note on the Dodge Hemi, they are awful thirsty when you work they semi hard. I dough you could afford to feed one in a MH. Most of the pickups with the hemi complain about barley getting 10 mpg.
hardtobe wrote:OhhWell wrote:hardtobe wrote:RMIGHTY1 wrote:
OK, newbie here and aspiring RV'er. What comments can be made about the advantages/disadvantages of a 350 HP internal combustion engine vs. a 350 HP diesel engine in a class A camper (assuming all other variables are equal)?
the 350HP diesel will most likely be a Diesel pusher which is considerable heavier than a gasser therefore its hard to compare
as a 350 gas motor would not be viable in such a unit for many reasons
that being said though I personally would prefer the diesel(if there was such a motorhome made) because of the larger torque value because I drive the mountains all the time
and the diesel will pull loads up steep passes at way less RPM and stress.
Anyone whom says they don't need a exhaust brake or better yet a compression brake is not the brightest bulb in the room/
YES u can get away without one and be safe but why if u don't need to?
I can safely decenda "steep" pass at 50MPH wiith a engine brake.TRY that with your old DP and just air brakes!!!
Now every diesel pusher MH made of recent(2000) onward have them so people who don't have old old MH
I just don't see the point of the arguments here trying to compare 1/4 mile pickup drags to a 40 foot diesel pusher 4 slide mH with 350
and more HP because its just simply not the same worlds
Try and imagine a 38-39+++ 2-4 slide Diesel pushers units with a 410HP
dodge hemi engine running the unit.Its would be the sickest running MH out there and another thing the guy with the 502 A class MH towing 18000 lbs did not go up a 6% grade at 80MPH.that is so much BS its ridiculous(unless he hit the hill at 100MPH and it was short 6% grade)
I don't think he's running a stock 502. When he said he could pull 18,000 pounds up the grade, he did not mean his coach AND 18,000lbs, he meant combined.
well he says quote:"I can pull 18K lbs up a 6% grade at 80 mph." so to me hes saying plus the Motorhome
OhhWell wrote:hardtobe wrote:RMIGHTY1 wrote:
OK, newbie here and aspiring RV'er. What comments can be made about the advantages/disadvantages of a 350 HP internal combustion engine vs. a 350 HP diesel engine in a class A camper (assuming all other variables are equal)?
the 350HP diesel will most likely be a Diesel pusher which is considerable heavier than a gasser therefore its hard to compare
as a 350 gas motor would not be viable in such a unit for many reasons
that being said though I personally would prefer the diesel(if there was such a motorhome made) because of the larger torque value because I drive the mountains all the time
and the diesel will pull loads up steep passes at way less RPM and stress.
Anyone whom says they don't need a exhaust brake or better yet a compression brake is not the brightest bulb in the room/
YES u can get away without one and be safe but why if u don't need to?
I can safely decenda "steep" pass at 50MPH wiith a engine brake.TRY that with your old DP and just air brakes!!!
Now every diesel pusher MH made of recent(2000) onward have them so people who don't have old old MH
I just don't see the point of the arguments here trying to compare 1/4 mile pickup drags to a 40 foot diesel pusher 4 slide mH with 350
and more HP because its just simply not the same worlds
Try and imagine a 38-39+++ 2-4 slide Diesel pushers units with a 410HP
dodge hemi engine running the unit.Its would be the sickest running MH out there and another thing the guy with the 502 A class MH towing 18000 lbs did not go up a 6% grade at 80MPH.that is so much BS its ridiculous(unless he hit the hill at 100MPH and it was short 6% grade)
I don't think he's running a stock 502. When he said he could pull 18,000 pounds up the grade, he did not mean his coach AND 18,000lbs, he meant combined.
