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Lui
Samba Member
Joined: March 12, 2004
Posts: 151
Location: East TN
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 Posted: Thu May 05, 2005 7:18 am Post subject: Five speed tranny? |
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Hello all,
I was wondering how practical is it to get a five speed tranny put in my bus so the rpms are not so high at 70 mph? I usually travel at roughly 65mph, and feel with a well planned fifth gear, the engine could handle it, and it would help reduce the rpms greatly. At 55mph in fourth I lose no speed up the hills, so I think I have plenty of torque at that rpm, albeit at less wind resistance.
Cheers,
Lui
P.S. I do not have an rpm gauge, what rpm would you say the bus is at while travelling at 65 - 70 mph? I'm guessing 4000? Isn't that not so good for these engines? (mine is slightly modified with a higher performance head).
www.geocities.com/lilithomson |
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shiningstar76
Samba Brewer
Joined: July 12, 2003
Posts: 2689
Location: Savannah
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| Posted: Thu May 05, 2005 8:20 am Post subject: |
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3500 to 4000 rpm shouldn't be bad for an aircooled vw. Plenty of cooling air. Are you planning on building a five speed trans or adapting one?
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KK4NTP
96 Tacoma
86 4Runner
My bus caught on fire and is now on the other coast with someone who gave me money for it. |
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Lui
Samba Member
Joined: March 12, 2004
Posts: 151
Location: East TN
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| Posted: Thu May 05, 2005 8:26 am Post subject: |
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Whichever is most convenient; I was open to suggestions. . .  |
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josh
Samba Member
Joined: July 13, 2003
Posts: 1773
Location: laid back in the tall grass
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| Posted: Thu May 05, 2005 8:46 am Post subject: |
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What year is the bus?
I just dug out my 76 bus owners manual to reference for another thread. Max and cruising speed is 75mph. cruising at 70 should not be a problem. Bringing the rpm's down might cause your heads to run hotter. |
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Lui
Samba Member
Joined: March 12, 2004
Posts: 151
Location: East TN
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| Posted: Thu May 05, 2005 8:52 am Post subject: |
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| Mine is a 1976 2.0 liter with the dreaded Weber single progressive carb, not the stock fuel injection. Do you interpret maximum cruising speed to be different than maximum speed obtainable, as I do? If so, then I feel a bit better about the highway speeds. |
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westy78
Samba Member
Joined: August 20, 2002
Posts: 2005
Location: Portland OR
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| Posted: Thu May 05, 2005 9:25 am Post subject: |
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Keep in mind that these engines were made to run all day at higher RPM's. If you have a healthy engine and good cooling (all seals in place, engine compartment sealed tight) running at 70 will not hurt it (although I like to keep mine at 65 tops). They are cooled by the airflow so if you reduce the RPM's with a fifth gear, you reduce the air CFM and will make your heads run hotter.
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Jasan C.
'78 Westy
VW Campmobile, it goes on vacation with you. |
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Jtast17
Samba Member
Joined: November 02, 2004
Posts: 220
Location: Elmira, NY
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| Posted: Thu May 05, 2005 9:25 am Post subject: |
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| My bus is a 72 with a 2000cc motor, Dual Dells. Will cruise at 70mph @ 4000rpms all day long without issue (short of a head wind ), nice and cool to the touch if I pull her off the road at that speed. A five speed would def be nice....but your def. right on that it would have to be a well planned firfth gear. |
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Lui
Samba Member
Joined: March 12, 2004
Posts: 151
Location: East TN
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| Posted: Thu May 05, 2005 9:41 am Post subject: |
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| westy78 wrote: |
| Keep in mind that these engines were made to run all day at higher RPM's. If you have a healthy engine and good cooling (all seals in place, engine compartment sealed tight) running at 70 will not hurt it (although I like to keep mine at 65 tops). They are cooled by the airflow so if you reduce the RPM's with a fifth gear, you reduce the air CFM and will make your heads run hotter. |
So, my heads run hotter at 55 mph than 70 mph? I might kick myself for this question, but what is "CFM"? I understood that the bus was designed to run optimally at 55 - 60 mph, was I incorrect?
P.S. I usually run mine at 65 tops, also.  |
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westy78
Samba Member
Joined: August 20, 2002
Posts: 2005
Location: Portland OR
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| Posted: Thu May 05, 2005 9:48 am Post subject: |
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Ratwell took some readings at certain speed increments/RPM's to determine where the most efficient cooling took place. You can see that between 60-65 the temps level off and hold. If you could figure out what gear ratio to use to stay at those RPM's at the cruising speed you want then a fifth gear may be beneficial. http://www.thesamba.com/vw/forum/viewtopic.php?t=1...s&start=20
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Jasan C.
'78 Westy
VW Campmobile, it goes on vacation with you. |
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westy78
Samba Member
Joined: August 20, 2002
Posts: 2005
Location: Portland OR
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| Posted: Thu May 05, 2005 9:49 am Post subject: |
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oops!
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Jasan C.
'78 Westy
VW Campmobile, it goes on vacation with you.
Last edited by westy78 on Thu May 05, 2005 9:56 am; edited 1 time in total |
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westy78
Samba Member
Joined: August 20, 2002
Posts: 2005
Location: Portland OR
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| Posted: Thu May 05, 2005 9:55 am Post subject: |
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| Lui wrote: |
| So, my heads run hotter at 55 mph than 70 mph? |
Not necessarily. At the lower speeds there is not as much load on the engine. With head temps, it's kind of a give and take. Head temp is also dependant on both load and rpm's. So lower speeds = less load but less CFM, higher speed=more load but more cooling air to the heads due to higher RPM's. Make sense?
| Lui wrote: |
| I understood that the bus was designed to run optimally at 55 - 60 mph, was I incorrect? |
Well, that is kind of up for debate. Some will say that they were designed to run full out at top speed all day. Others, including me, will say keeping them below 65 will keep them happy longer.
CFM=cubic feet per minute
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Jasan C.
'78 Westy
VW Campmobile, it goes on vacation with you. |
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tristessa
Samba Member
Joined: April 07, 2004
Posts: 3992
Location: Portland, OR
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| Posted: Thu May 05, 2005 9:57 am Post subject: |
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<deletia> Whoops, Jasan beat me to it.
Last edited by tristessa on Thu May 05, 2005 10:40 am; edited 1 time in total |
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westy78
Samba Member
Joined: August 20, 2002
Posts: 2005
Location: Portland OR
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| Posted: Thu May 05, 2005 10:02 am Post subject: |
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I'll add one more thing. You have to think more in terms of RPM's and load in a certain gear when it comes to CHT. For example 50mph in third will have a different head temp than 50mph in fourth gear because of the difference in RPM moving the cooling fan at different speeds.
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Jasan C.
'78 Westy
VW Campmobile, it goes on vacation with you. |
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shiningstar76
Samba Brewer
Joined: July 12, 2003
Posts: 2689
Location: Savannah
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| Posted: Thu May 05, 2005 10:05 am Post subject: |
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a fifth gear = higher speeds with lower rpms~cooling air and increased headwind. 60 in fifth might become 50 in fourth with the idea that we have a groovy fifth gear and running at hightway speeds for a long time with less rpms might cause the motor to run hot. Is this what we are considering in a 'well planned fifth gear?" I am tempted to think that VW thought of this.
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KK4NTP
96 Tacoma
86 4Runner
My bus caught on fire and is now on the other coast with someone who gave me money for it. |
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westy78
Samba Member
Joined: August 20, 2002
Posts: 2005
Location: Portland OR
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| Posted: Thu May 05, 2005 10:11 am Post subject: |
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| shiningstar76 wrote: |
| a fifth gear = higher speeds with lower rpms~cooling air and increased headwind. 60 in fifth might become 50 in fourth with the idea that we have a groovy fifth gear and running at hightway speeds for a long time with less rpms might cause the motor to run hot. Is this what we are considering in a 'well planned fifth gear?" I am tempted to think that VW thought of this. |
A well planned fifth gear to me would be one that kept the optimum cooling/rpms at the desired cruising speed. Say you want to cruise at 75mph. If you could match the gearing to give you 3400-3500 RPM's at that speed you would be matching the same temps as cruising at 65mph in Ratwells graph with stock gearing.
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Jasan C.
'78 Westy
VW Campmobile, it goes on vacation with you. |
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Lui
Samba Member
Joined: March 12, 2004
Posts: 151
Location: East TN
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| Posted: Thu May 05, 2005 11:45 am Post subject: |
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| westy78 wrote: |
| shiningstar76 wrote: |
| a fifth gear = higher speeds with lower rpms~cooling air and increased headwind. 60 in fifth might become 50 in fourth with the idea that we have a groovy fifth gear and running at hightway speeds for a long time with less rpms might cause the motor to run hot. Is this what we are considering in a 'well planned fifth gear?" I am tempted to think that VW thought of this. |
A well planned fifth gear to me would be one that kept the optimum cooling/rpms at the desired cruising speed. Say you want to cruise at 75mph. If you could match the gearing to give you 3400-3500 RPM's at that speed you would be matching the same temps as cruising at 65mph in Ratwells graph with stock gearing. |
That's about what I had in mind, more or less.
New question: If I have planned extensive travelling at 65, what are good times to take breaks? -- i.e. let the engine "rest." Obviously not when the engine is really hot, but after every three hours on the highway? Four? Any thoughts? |
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westy78
Samba Member
Joined: August 20, 2002
Posts: 2005
Location: Portland OR
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| Posted: Thu May 05, 2005 11:57 am Post subject: |
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| Lui wrote: |
| . New question: If I have planned extensive travelling at 65, what are good times to take breaks? -- i.e. let the engine "rest." Obviously not when the engine is really hot, but after every three hours on the highway? Four? Any thoughts? |
I think this depends more on the roads you are travelling, weather conditions, etc. I've driven over six hours at a time in my bus. If you have gauges and keep an ocassional eye on them and they are staying within the acceptable ranges, I say keep on truckin. These things were made to run. On the other hand if you are climbing major hills, one right after another and bucking a fierce head wind in hot air temps stopping every once in awhile might be a good idea. It all depends on the particular bus and how well in tune it's in.
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Jasan C.
'78 Westy
VW Campmobile, it goes on vacation with you. |
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USMCbug
Samba Yoda
Joined: April 29, 2004
Posts: 2573
Location: Wichita, KS
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| Posted: Thu May 05, 2005 11:59 am Post subject: |
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Lui
Josh
I had to do a double take. 
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72 Super Beetle
73 Standard Beetle
79 Baywindow Bus
65 Split Window Bus
79 Baywindow Bus
71 Super Beetle (current)
"When war does come, my advice is to draw the sword and throw away the
scabbard."
- General Thomas "Stonewall" Jackson |
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tristessa
Samba Member
Joined: April 07, 2004
Posts: 3992
Location: Portland, OR
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| Posted: Thu May 05, 2005 12:01 pm Post subject: |
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| My rule of thumb is to stop when I need to pee, when I need more coffee, or when I need to put gas in the tank. Mmm.. coffee.. |
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westy78
Samba Member
Joined: August 20, 2002
Posts: 2005
Location: Portland OR
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| Posted: Thu May 05, 2005 12:01 pm Post subject: |
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I hope that's not a premonition for a before and after shot. 
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Jasan C.
'78 Westy
VW Campmobile, it goes on vacation with you. |
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