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Roy Strickland
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 15, 2005 - 2:14 am: | |
I am the one with the '78 GMC RTS II. It has a Detroit 8v71. Now... I know the clunker is governed, to about 57 mph to be more specific. Now if you get somewhat of a hill, it will lose around 10 mph with no people. Is that normal??? I can't imagine what it would do if it were full. I have not yet checked the air filter... The fuel filters I'm sure will be checked as the bus is currently broken down with some sort of fuel issue.. (They are what I believe to be the "old style" which I guess you put some kind of replacement in a metal, filter shaped, canister-like device.) I can tell you the exhaust (which comes out on the bottom of mine) is really really squished. I was probably down to about 5" X 1". At idle, it will almost blow you away. I tried to open it up a little with vise grips but I only had luck with the exit part and the whole pipe is smashed pretty flat for about 16 - 18 inches or so. Wouldn't this certainly steal power??? I've never seen such a fast rush of air from ANYTHING at idle like that.
I had a mechanic adjust the governor slightly upwards, but a negative side effect was the idle went up too. I only got like 2 mph out of it. I am gonna turn it back down because I don't want it to idle faster than it needs to for putting it into gear. Does anyone know of some way to get more power out of it. I can't believe how much speed it loses on hills empty. I thought about getting a new rear-end or whatever, but I figured if it can't pull the one it has now uphill, what will it do with a higher gear??? But I am really thinking the exhaust is pretty highly restricted... I am gonna cut that last little flat section off and see what happens. (Anyone disagree with cutting it off?? I don't want to do a bad thing, but it seems so restricted.) What should I do?? Thanks again!!!!!!!!
RS |
James Maxwell (Jmaxwell)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 15, 2005 - 9:30 am: | |
I would not cut the exhause off, but instead replace the damaged section. You don't want to be re-circulating exhause gas into the engine compartment or anywhere else under the bus. If it is smashed as much as you say, it is undoubtedly affecting engine performance.
You probably have a 4.56 or 5.13 rear end already, given the top speed you mention and would have to adjust the governor beyond its' safe RPM limit of 2350-2400 RPM in order to increase your speed any significant amount. You're still not going to get a freeway flier given the gearing the bus was probably built with. If u lower the rear-end ratio for more top end, you are going to get less pulling power
From what you said, your mechanic must specialize in Toyotas, not Detroits. Fix the exhaust problem 1st, then go from there. Clean the air cleaners, change the fuel filter cartridges, fix the exhaust (not cut it off). |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 03, 2005 - 8:39 pm: | |
Roy, you might try to find out what your empty weight and horsepower are. If you're trying to compare how a car behaves to how a bus behaves, you are going to be disappointed.
Most cars can produce 150 to 300 hp. If they weigh 2500 to 4000 lbs., that means that they have around 13 to 16 lbs. of weight per hp.
Our coach is one of the lightweights and a pretty good performer, but at 27,000 lbs. and 270 hp., it has to push 100 lbs. with each hp.
This means that the average car has around 6 times the hp. per pound of our coach.
I think your empty coach may weigh pretty close to our converted one, but what horsepower is the engine set for?
One other thing. While your transmission may shift faster than ours because we have a manual unit, we probably have a little more horsepower getting to the wheels until your converter locks up.
As ours is set up, geared to 83 mph., we can almost pull a 3% grade in high gear, and nearly 6% in third with a top speed of 57 mph.
Many grades even on the freeway can be as steep as 5 or 6%, so we lose some speed when in high gear on these.
Just what were you expecting?
Tom Caffrey PD4106-2576
Suncatcher |
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