Date: Mon, 29 Oct 2001 01:48:48 EST
Reply-To: FrankGRUN@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Frank Grunthaner <FrankGRUN@AOL.COM>
Subject: Re: Transmission Ratios, Diesels, Conversions
Content-Type: text/plain; charset="US-ASCII"
I've chosen to reply in reverse order to Mark's comments. I've placed my
comments in bold hoping to avoid even more confusion:
In a message dated 10/27/01 1:23:27 PM, drillock@EARTHLINK.NET writes:
<< And yes, if a mere 60 mph is your intended highway cruising speed then
the diesel r+p ratios are useable. I just got back from a 1200 mile
interstate trip in my 4.57 r+p TD Vanagon. I did not see any passenger
vehicles traveling at such a low speed except uphill. Who in God's name
would install a Tiico conversion and then drive at such obstructionist
speeds on long trips? Only a masochist would hold 60 mph for hours on I5
with semis constantly running up their butts at 70 mph. "The most
efficient utilization of an engine" is not always the primary
consideration. Sometimes real world factors interrupt the dreaming.
Unbelievable! Real World my posterior! Most efficient and optimal gearing
choices refer to a reasonable midband operation - that is, a condition where
sufficient power reserves remain so as to exceed that velocity, and lower
speed power remains such that the engine is not devoid of the torque needed
to fend off small inclines. I never suggested a speed governor holding the
damn thing at 60.
As for velocity chest pounding, I just returned from a trip from LA to
Monterey, then Santa Cruz and back. 830 miles. The run to and from 152 was on
I5. In my abused Westfalia with DZ transmission (5.86 r&p) I ran between 75
and 85 most of the way. The exceptions were the Grapevine which I cleared at
62 full throttle in third, and one semi where I had to push it up to 90. I
averaged 17.9 mpg for the trip as I was in a hurry. I had a maximum oil
temperature of 235 F (113 C), minimum oil pressure of 34 psi with Mobil 1
15W-50, and a maximum EGT reading of 740 C (1365 F) running at 85 mph in the
closed loop mode. (These numbers refer to 215/75x15 tires, so the actual
speed is around 3 to 4% higher). This was done with AC on. I am pleased to
say that I was not passed by passenger car or semi. As I have indicated many
times in the past, this engine/transmission package can wind beyond 6100 in
fourth (around 98) on a straight and level. The chip redline is 6700 rpm. I
often spin up to 6500 rpm in 3rd to pass on hills (70 mph).
60 mph my sensitized hemorrhoids!
I guess it all depends on which set of engineers you have an
affinity for. Look at the gearing choices of the VW engineers who
actually were responsible for putting the gas inline 4 engine into
production Vanagons. Don't expect to see 4 speeds with diesel r+p ratios
(5.83, 5.43). They did NOT choose such low gearing. I believe 4.83 is
what they mostly used, a waterboxer ratio. Also offered 4.57 AFAIK. Were
they brushing aside their own engineering data?
OK, now this is a valid point. Going through Helmut's transmission ratio page
and assuming its veracity, several points are clear:
The 67 horse, A/C engine pulls an overall gear of 3.89 (top) and 17.28 in
1st. For the 1.9 WB 82 HP engine the values are 4.11 and 18.26. For the
diesels with 5.86 r&p, the numbers are 4.89 and 22.17; with the 5.43 gears,
they are 4.62 and 20.54. The Euro TD runs 4.29 and 20.79. For the 5 speed
diesels, the numbers are 4.18 and 22.31, or 4.45 and 22.31, or 4.51 and
22.31, and for the most recent 3.96 and 19.84. For the SA transmissions, the
93.8 HP engine and the 162 HP engine run a 4.833 r&p with an overall ratio of
4.11 and 18.26 for first. Same as the 1.9 and 2.1L WB power trains. The SA 5
speeds run an overall top gear ratio of 3.94 and 3.73, with 1st gear numbers
of 19.86 and 18.76. For the automatics, 68 hp engine runs a 4.09 in top gear
as do the 76 to 88 HP 1.9L WB engines and the 93.4 and 109.9 HP 2.1L engines.
I assume the 3.74 R&P was a short run fluke.
From these ratios, some observations:
1. The engineers are running the same gearbox for a wide variety of engine
power outputs. If you include the A/C, the WBs and the SA I4 and I5's in the
group, the final drive top gear ratios run from 3.73 to 4.11. In this group,
the strongest engine pulls a 4.11 and the weakest pulls the 3.89. The range
in power is a factor of 2.4x! Of course, the old A/C engine makes its torque
max at 3000 rpm, while the SA I5 makes its max at 4500 rpm. Of course these
gear ratios don't begin to relate to the differences.
1a. Two possibilities - A). These are the same engineers that placed the
heater fan in the observed relationship to the dash. or B). They are running
at cruise with nearly the maximum load the engine can pull.
2. All the gear ratios give a first gear pull of about 20 to 1. It is hard to
start this box from a standstill.
3. Typical engine and gearing practice is to engineer a 4 speed gear box with
upper ratios such that you can shift from 4th to third and hit the torque max
at speeds around 60 mph so there is strong thrust for passing. Not possible
with these gearboxes which give a 50 percent rpm drop from 4th to 3rd (4
speed) or 35 percent for 5th to 4th.
So, I return to my former statements:
1. The wheel thrust values are as I have given them in the previous post.
2. Acceleration from any speed is a direct function of the number of pounds
of thrust you have available above and beyond the amount you expend to
maintain the current speed.
3. Lifting the vehicle up and over any grade encountered will come out of
your thrust reserve. High reserve, climb a 5 percent incline without slowing
at your chosen velocity. Low reserve, make that a 0.5 percent incline, or
drop a gear.
4. Major impact on longevity is load, not rpm in this range of piston speeds.
5. Fuel consumption is function of load, not just rpm. 8 percent less fuel
for 40 percent lower rpm.
6. For modest power/torque conversions the DZ is good, the DZ with 215/75x15
wheels or the DM is a fair alternative. The 1.8L I4 engines with a DK trans
will be about as swift as the 1.9L WB when not running on water/glycol vapor
mixtures, the TIICo with the 4.83 r&p will go like the 2.1 wb it replaced.
Put those I4's in the DZ, DZ and 15's or the DM and you will have
substantially more thrust available than the running 2.1.
7. Thrust is fun.
8. Spending money on overpriced conversions is painful.
9. Assuage pain with pleasure (er fun)!
10. Masochists convert and go slow as stock.
11. With higher power and torque reserves, go for the 4.11 overall or the
3.89.
12. Frankly, I took the maximum speed I wanted (100 mph), divided by the
engine redline (6300 for the normal I4), the tire revs per mile value, and
the gear ratio in fourth to determine the best ratio for me.
13. To each, his own view of the real world!
Mark >>
