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Batan
Samba Member
Joined: March 10, 2003
Posts: 1637
Location: Vancouver, BC
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 Posted: Mon Aug 08, 2005 9:14 pm Post subject: Highway revs? Possible or is my tach smoking crack? |
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I have a cheap old aftermarket tach but I'm shifting using the speedo.
Kind of 15mph(shifit to 2nd), 25-30(shift to 3rd) and about 45mph to 4th.
Watching the revs, they make sense in first couple of gears but the tach shows about 2100rpm at 60mph on the highway...does ANY of VW trannies allow that low of revs on the highway? What should it be at 60mph?
The car is a 61 coupe and the tires are stock. |
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execk2
Samba Member
Joined: April 30, 2005
Posts: 1359
Location: Quebec City
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| Posted: Tue Aug 09, 2005 4:37 am Post subject: |
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Should be closer to 3000-3300 rpm. Does that make sense?
Mike
www.mikeandjosee.com |
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GhiaNut
Samba Member
Joined: December 17, 2003
Posts: 606
Location: Gulf Coast of Florida
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| Posted: Tue Aug 09, 2005 5:22 am Post subject: |
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| Any chance somebody slipped in a "freeway flyer"? They're aftermarket; geared lower in 4th. |
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Batan
Samba Member
Joined: March 10, 2003
Posts: 1637
Location: Vancouver, BC
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| Posted: Tue Aug 09, 2005 8:25 am Post subject: |
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| GhiaNut wrote: |
| Any chance somebody slipped in a "freeway flyer"? They're aftermarket; geared lower in 4th. |
I think there is. That would be awsome, wouldn't it?   |
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Rome
Samba Member
Joined: June 02, 2004
Posts: 10768
Location: Pearl River, NY
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| Posted: Tue Aug 09, 2005 2:41 pm Post subject: |
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| Does your tach have a small switch to use it on 4-6-8 cylinder engines?? |
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Batan
Samba Member
Joined: March 10, 2003
Posts: 1637
Location: Vancouver, BC
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| Posted: Tue Aug 09, 2005 7:02 pm Post subject: |
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| Rome wrote: |
| Does your tach have a small switch to use it on 4-6-8 cylinder engines?? |
Yes it does...and it's on 4. However, I checked it today I think that switch might be bad since the tach bounces around if I jiggle the switch. At idle and slight throttle it seems to be correct though... |
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Banzai KG
Samba Member
Joined: April 10, 2004
Posts: 2992
Location: Sunnyvale, CA
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| Posted: Wed Aug 10, 2005 12:15 am Post subject: |
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| GhiaNut wrote: |
| Any chance somebody slipped in a "freeway flyer"? They're aftermarket; geared lower in 4th. |
Actually it's not a lower 4th, you mean a higher 4th gear. But also to have a "freeway flyer", it's a conjunction of both a higher Ring & Pinion (3.88:1) and a higher 4th gear; 0.89 - stock 4th gear or 0.82 - Bus 4th gear.
A later model Beetle (I think of a '73 and later) started to come out with the 3.88 R/P and a 0.93 4th gear, changing the 4th to either a 0.89 or 0.82 will drop the RPMs lower.
_________________
Jim Kikuchi
Sunnyvale (near San Jose), CA
1964 Karmann Ghia coupe
V.V.W.C.A. - Golden Gate Chapter: http://www.ggcvvwca.org/
B.L.T.N. (Better Late Than Never) late model VW Club (San Jose/Santa Clara, CA): https://www.facebook.com/groups/bltnvw/
NorCal Aircooled Group (NAG) Facebook Goup: https://www.facebook.com/groups/NAGVW/ |
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peterericb
Samba Member
Joined: January 11, 2005
Posts: 523
Location: Texas - North DFW
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| Posted: Wed Aug 10, 2005 5:55 am Post subject: |
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write down some mph and RPMs for all your gears, measure the diameter of your tires and use algebra to figure out your other gears, assuming that the tach is right...
Then look up your tranny number and see if the other gears make sense. If not, chances are the tach is wrong (or you have a 100% custom tranny)... if the other gears match then you definatly have a freeway flyer.
If you used This calculator, you would have to work backwards, but I bet you could find a formula or a calculator that would do what you wanted.
I would look up your tranny code to fill in that calculator, then see if the mph comes close for any of the gears. Pretty quick test...
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I love it when a guy covered in tattoos tells me I should keep my Ghia "All Original" |
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Banzai KG
Samba Member
Joined: April 10, 2004
Posts: 2992
Location: Sunnyvale, CA
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| Posted: Wed Aug 10, 2005 8:12 am Post subject: |
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This chart shows the gear ratios for the Type 1 Beetle (same as Karmann Ghia), use this to compare: http://sandlizrd.baja.com/gears.htm
You can also use this Gear Ratio Formula:
To calculate mph in any gear here is the formula:
RPM X 1/2 TIRE HEIGHT
-------------------------------------------------------- = MPH
GEAR RATIO X RING & PINION X 168
_________________
Jim Kikuchi
Sunnyvale (near San Jose), CA
1964 Karmann Ghia coupe
V.V.W.C.A. - Golden Gate Chapter: http://www.ggcvvwca.org/
B.L.T.N. (Better Late Than Never) late model VW Club (San Jose/Santa Clara, CA): https://www.facebook.com/groups/bltnvw/
NorCal Aircooled Group (NAG) Facebook Goup: https://www.facebook.com/groups/NAGVW/ |
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Batan
Samba Member
Joined: March 10, 2003
Posts: 1637
Location: Vancouver, BC
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| Posted: Wed Aug 10, 2005 11:25 am Post subject: |
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I'm definetly suspecting the tach. Seems to be a lot closer to what it should be if I switch it to 6 or 8 cylidner  It shows high idle if I switch it to 6 or 8 but it definetly stretches the rev range. Set at 6, it will rev at about 3500 rpm at 60 mph.
Set at 4, it rarely goes over 2000rpm...2300 is about the highest.
anybody knows anything about tachs? I installed it, not rocket science so I'm wondering what could be wrong. |
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Banzai KG
Samba Member
Joined: April 10, 2004
Posts: 2992
Location: Sunnyvale, CA
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| Posted: Wed Aug 10, 2005 6:03 pm Post subject: |
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| Batan wrote: |
| anybody knows anything about tachs? I installed it, not rocket science so I'm wondering what could be wrong. |
What made or model is this so-called aftermarket tach? VDO, Autometer/Autoguage, Sun, Stewart & Warner, etc...?
It would help to narrow down the make/model of the product so we know what product you're dealing with.
_________________
Jim Kikuchi
Sunnyvale (near San Jose), CA
1964 Karmann Ghia coupe
V.V.W.C.A. - Golden Gate Chapter: http://www.ggcvvwca.org/
B.L.T.N. (Better Late Than Never) late model VW Club (San Jose/Santa Clara, CA): https://www.facebook.com/groups/bltnvw/
NorCal Aircooled Group (NAG) Facebook Goup: https://www.facebook.com/groups/NAGVW/ |
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guenther
Samba All-American
Joined: November 05, 2003
Posts: 125
Location: Between corn and bean fields
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| Posted: Wed Aug 10, 2005 6:41 pm Post subject: |
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My tach shows 2500 at 55mph and 3000 at 65 mph and it is a '72 stock tranny.
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coad 
Samba Scapegoat
Joined: September 12, 2002
Posts: 7573
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| Posted: Wed Aug 10, 2005 7:01 pm Post subject: |
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I can't see where it is your tach.
If the tach is accurate in the lower gears (as you swear it is), then the tach is accurate. The tach doesn't know what gear you're in-- 2500rpm is 2500rpm no matter what gear is engaged.
And there wouldn't be anything different happening at the engine that I can think of either. Same deal, the engine doesn't know what gear you're in either.
I think you almost have to have a weird 4th gear from a freeway flyer or something like was suggested earlier. |
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Batan
Samba Member
Joined: March 10, 2003
Posts: 1637
Location: Vancouver, BC
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| Posted: Thu Aug 11, 2005 6:16 pm Post subject: |
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| Banzai KG wrote: |
| Batan wrote: |
| anybody knows anything about tachs? I installed it, not rocket science so I'm wondering what could be wrong. |
What made or model is this so-called aftermarket tach? VDO, Autometer/Autoguage, Sun, Stewart & Warner, etc...?
It would help to narrow down the make/model of the product so we know what product you're dealing with. |
OK, I think it's definetly the tach. I would not mind fixing it although it's a cheap one coz I kinda like the way it looks.
Anyways, it has not brandname anywhere on it but rather a logo that is a circle with 2 arrowheads pointing clockwise on the opposite sides of a circle(pointing out circular motion). |
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70 140
Samba Member
Joined: September 22, 2002
Posts: 8471
Location: Ontario Canada
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| Posted: Sun Aug 14, 2005 7:33 am Post subject: |
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Why don't you set it on 8 and then half the number and see what you get:).
I'm going to tend to agree with coad. if its working at lower RPMs then I doubt it is bad. |
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execk2
Samba Member
Joined: April 30, 2005
Posts: 1359
Location: Quebec City
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| Posted: Sun Aug 14, 2005 8:19 am Post subject: |
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I agree that it is probably incorrect but OK. But, I think it would be important to try and verify this. The car needs RPM for cooling. A freeway flyer in heat without an external cooler runs the engine WAY too hot. On the safe side make sure your oil is topped off and fresh at all times. But get this checked out. Maybe a garage can hook up a temp to verify!? 
Mike
www.mikeandjosee.com |
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Batan
Samba Member
Joined: March 10, 2003
Posts: 1637
Location: Vancouver, BC
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| Posted: Sun Aug 14, 2005 10:22 am Post subject: |
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| execk2 wrote: |
I agree that it is probably incorrect but OK. But, I think it would be important to try and verify this. The car needs RPM for cooling. A freeway flyer in heat without an external cooler runs the engine WAY too hot. On the safe side make sure your oil is topped off and fresh at all times. But get this checked out. Maybe a garage can hook up a temp to verify!?
Mike
www.mikeandjosee.com |
The car runs very cool on the highway even when hot. I can very easily touch the hold the dipstick after a long drive in hot weather in the city and on the highway.
The tach seems to be extremely incorrect, I already checked the ground and it's good. |
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