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Big Bad John
Samba Member
Joined: April 24, 2005
Posts: 431
Location: Palm Coast, Florida
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 Posted: Wed Apr 11, 2007 6:45 pm Post subject: Engine RPM's on the hiway. |
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What is the expected RPM's to run, on a long trip, with a 2.0 FI engine.
I have always been accustomed to not running my old 1600 bug motors above 3200 for an extended ride.
That's what I have been doing with the 2.0.
Because I have low profile tires, that RPM only gives me a top speed of 52 mph. If I move up to 3400 I pickup to 55. At 3600 it will do 60 mph.
It sounds good at 3600 and doesn't seem to be straining. Is it OK to maintain
that RPM on a long trip? |
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regis101
Samba Member
Joined: July 28, 2005
Posts: 2078
Location: Livermore, Ca
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| Posted: Wed Apr 11, 2007 7:22 pm Post subject: |
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| Our 78 does 3200 at 58 mph. 65 is ~3500. 70 is ~3900. The sweet spot is 62-63 mph. Hums along nicely |
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fusername
Samba Member
Joined: March 15, 2006
Posts: 2897
Location: Boston MA
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| Posted: Wed Apr 11, 2007 7:26 pm Post subject: |
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I belive ratwell once found that a type 4 has an ideal cooling vs power rpm of 3600. I keep mine at approx 35-34 and I think that is about 57 mph, I say approx becasue my tach isn't too accurate, and I say I think because my speedo cable broke. gets me 19 to the gallon on long highway runs, and the engine sounds happy with it. I dont push too hard because the po drove without the engine seal in one piece for who knows how long. Gets me where I am going.
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Bleyseng
Samba Member
Joined: July 03, 2005
Posts: 4752
Location: Seattle
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| Posted: Wed Apr 11, 2007 9:05 pm Post subject: |
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max cooling is at 4200 rpms so whatever that is speed wise....
I run 70-75 without any problems and low CHT's. (275-325F)
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70 Ghia Black convert-9/69 build date-stock w/133k 1600 SP-barn find now with a rebuilt tranny and engine
77 Westy 2.0L w/Ljet, Camper Special engine-95hp and with LSD!(sold)
76 Porsche 914 2.1L L20c, 120hp Djet (sold)
87 Syncro Westy Titan Red 2.1L 2 knob 100k miles |
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AndyM
Samba Member
Joined: October 24, 2003
Posts: 315
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| Posted: Thu Apr 12, 2007 11:41 am Post subject: |
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| 70 mph @ 3100rpm's. Cool temps and about 17 intown and 20 on the highway |
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brent lehr
Samba Member
Joined: November 02, 2003
Posts: 172
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| Posted: Thu Apr 12, 2007 1:40 pm Post subject: |
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I used to consistantly run 4200 rpms in my 78 on many long trips without problems. This included many 1000+ mile trips (stopping only for gas) over the course of five years.
But, drive where you feel confortable. That's the key. If you step the cruising RPM up a couple hundred rpm and in turn worry about it the whole time, then it's not worth it to me. |
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busnerd
Samba Member
Joined: March 18, 2002
Posts: 336
Location: Vancouver, BC
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| Posted: Fri Apr 13, 2007 6:31 pm Post subject: |
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| AndyM wrote: |
| 70 mph @ 3100rpm's. Cool temps and about 17 intown and 20 on the highway |
Those rpm seem low at that speed.... do you have a modified transmission?
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Clarke B.
samba member # 3245
'78 Westfalia Dakota Beige
'64 Camper |
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nc68bugman
Samba Member
Joined: August 12, 2006
Posts: 681
Location: Beaufort, NC
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| Posted: Fri Apr 13, 2007 6:33 pm Post subject: |
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| Or small tires front, taller tires in rear! Scott |
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AndyM
Samba Member
Joined: October 24, 2003
Posts: 315
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| Posted: Fri Apr 13, 2007 7:14 pm Post subject: |
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| 73 Bus with a 1800 top end, later trans with the taller 4th. 195 75 14's all around and dual baby webers. |
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static
Samba Member
Joined: March 22, 2002
Posts: 1831
Location: The High Desert
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| Posted: Fri Apr 13, 2007 8:31 pm Post subject: |
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| Quote: |
| a type 4 has an ideal cooling vs power rpm of 3600. |
What about a type 2? (ie: 1600 upright, 68-71 bus) |
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NASkeet
Samba Member
Joined: April 29, 2006
Posts: 2958
Location: South Benfleet, Essex, UK
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| Posted: Sat Apr 14, 2007 5:59 am Post subject: Road speed vs engine rpm |
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| AndyM wrote: |
| 70 mph @ 3100rpm's. Cool temps and about 17 intown and 20 on the highway |
To obtain a reading of 70 mph @ 3100 engine rpm, you must have either one or more of the following:
mis-calibrated speedometer;
non-stock, transaxle final-drive ratio and/or 4th gear ratio;
Porsche 911 or VW Vanagon, 5-speed transaxle
larger than stock, external tyre diameter at the rear;
smaller than stock, external tyre diameter at the front.
Even if using a 0·82, 4th gear ratio, in an otherwise stock, 1976~79 VW 2000 Type 2 transaxle and 185 R14 tyres, one would obtain no less than 3400 engine rpm @ 70 mph.
Regards.
Nigel A. Skeet |
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AndyM
Samba Member
Joined: October 24, 2003
Posts: 315
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| Posted: Sat Apr 14, 2007 10:01 am Post subject: |
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As stated, I'm running 195 75 14 tires. The speedo is accurate, and the trans has the taller fourth gear.
Would bumping the 1700 case up to an 1800 top end have any effect on my lower rpm's ?
Andy |
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Bleyseng
Samba Member
Joined: July 03, 2005
Posts: 4752
Location: Seattle
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| Posted: Sat Apr 14, 2007 12:58 pm Post subject: |
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no
_________________
70 Ghia Black convert-9/69 build date-stock w/133k 1600 SP-barn find now with a rebuilt tranny and engine
77 Westy 2.0L w/Ljet, Camper Special engine-95hp and with LSD!(sold)
76 Porsche 914 2.1L L20c, 120hp Djet (sold)
87 Syncro Westy Titan Red 2.1L 2 knob 100k miles |
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NASkeet
Samba Member
Joined: April 29, 2006
Posts: 2958
Location: South Benfleet, Essex, UK
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| Posted: Sun Apr 15, 2007 5:32 am Post subject: Road speed vs engine rpm, for various transaxles & tyres |
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| AndyM wrote: |
| 73 Bus with a 1800 top end, later trans with the taller 4th. 195 75 14's all around and dual baby webers. |
| AndyM wrote: |
As stated, I'm running 195 75 14 tires. The speedo is accurate, and the trans has the taller fourth gear.
Would bumping the 1700 case up to an 1800 top end have any effect on my lower rpm's ?
Andy |
Hello Andy.
I'm not entirely sure what is meant by your questions? What do you mean by an 1800 top end; 1974~75 VW 1800 Type 2, engine cylinder heads or 1974~75 VW 1800 Type 2, transaxle final drive ratio?
A 1972~73 VW 16/1700 Type 2 transaxle, with a substituted 1974~75 VW 1800 Type 2, transaxle's final drive ratio, would certainly affect your road speed versus engine rpm characteristics; reducing engine speed for a given road speed. What are your engine specifications?
The 4th gear ratios, of 1972~73 VW 16/1700 Type 2, 1974~75 VW 1800 Type 2 & 1975 VW 2000 Type 2 transaxles, are 0·82, 0·89 & 0·88 respectively, but the final drive ratios get smaller, with each successive transaxle model. When the stock 1972~73 VW 16/1700 Type 2 and 1974~75 VW 1800 Type 2 transaxles are compared, then for identical external tyre circumferences, the combination of 4th & final drive ratios, give virtually the same engine speed, for a given road speed, in 4th gear.
The one thing that has to be bourne in mind, is that for a given TRUE road speed (i.e. not necessarily the speedometer reading!), increasing the front-tyre, external circumference, will decrease the speedometer reading, but if the rear-tyre, external circumference is similarly increased, one will NOT notice any change in the comparison between engine tachometer readings and corresponding speedometer readings.
Without my pocket calculator to hand (I'm using the public library Internet facilities), I am not sure whether the 185/80 R14 or 195/75 R14 tyres, have the larger external circumference. Tyres with a 75% aspect ratio, are not generally available in Great Britain and I have yet to see or hear of one here. I do know that 185/80 R14 or 195/70 R15 tyres, are almost identical.
Sometime ago, I made an analysis of various tyre size and transaxle combinations (including British specification, VW Vanagon, 5-speed transaxles, which have some useful gear & final-drive ratio options, appropriate to stock & modified, 1968~79 VW 1600 & 17/18/2000 Type 2s).
Regards.
Nigel A. Skeet |
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