Author |
Message |
boulderdrop Samba Member
Joined: February 06, 2008 Posts: 481 Location: Seattle, WA
|
Posted: Fri Feb 05, 2010 2:30 pm Post subject: Question: Transaxle Gearing and Bostig-Zetec |
|
|
I'm getting everything together to drop the Bostig conversion into my 84 Westy, but I'm having troubles understanding why some people would change the gearing for the rebuilt transaxle that I'm getting. The new Ford Zetec 2.0L engine, rev's much higher than the old 1.9L WBX and I'll need to run the rpm's much higher to get the same torque/bhp. Here's the data...
BASELINE PERFORMANCE DATA AND OPTIONS
Zetec engine's performance:
HP: 130 at 5300rpm
Torque: 135 at 4500rpm
Redline: 6750rpm
Van's Tires:
Sizes: 205/65/16
Diameter: 26.5"
Circumference: 83.2"
Rev/Mile: 761
Stock Transaxle Gearing (i think):
1st:3.78
2nd:2.06
3rd:1.23
4th:0.85
Ratio Upgrades available from "AA Transaxle":
3rd Gear: 1.18. 1.14 & 1.09
4th Gear: .77 and .70
PERFORMANCE WHEN CHANGING THE GEARING
I've been playing around with a cool transmission-calculator, trying to get my head around what it means to change the gearing:
http://www.fatboyraceworks.com/gears/
Stock Gearing with 5300 rpm:
1st with 3.78 ratio = 25.12 mph
2nd with 2.06 ratio = 46.10 mph
3rd with 1.23 ratio = 77.21 mph
4th with 0.85 ratio = 111.72 mph
Changing the 3rd gear ratio's, yields the following:
1.23 ratio = 77.21 mph (stock)
1.18 ratio = 102.50 mph
1.14 ratio = 106.09 mph
1.09 ratio = 110.96 mph
Changing the 4th gear ratio's, yields the following:
0.85 ratio = 111.72 mph (stock)
0.77 ratio = 157.07 mph
0.70 ratio = 172.78 mph
QUESTIONS
Now these MPH are ridiculously fast and obviously not real-world, but I'll need to keep the RPM's much higher than the WBX. I usually drive in 3rd gear and this takes me up to about 64 mph in the real world.
Q: If I move to a taller 3rd with a 1.18, that'll take my theoretical top-speed from 77 mph to 102.50. But it might impose a "lugging" down of the engine when shifting from 2nd to 3rd, while I wait for the engine to spool up the rpms.
Q: If I just change the 3rd, but leave 4th the way it is... I would keep my top speed of 111 mph, which is fast enough and (I would think) would have more guts for the inclines, as the rpms would still be high... but I could probably stay in 3rd all-day-long, up/down the pass.
Q: If I changed 3rd with a 1.18 and 4th with a 0.77, it seems that 3rd would be were I was at all the time and 4th would just be a highway gear for long-straight-flat roads.
Corrections, thoughts, experiences?
Last edited by boulderdrop on Fri Feb 05, 2010 2:55 pm; edited 1 time in total |
|
Back to top |
|
|
candyman Samba Trout Slayer
Joined: December 20, 2003 Posts: 2694 Location: Missoula MT
|
Posted: Fri Feb 05, 2010 2:33 pm Post subject: |
|
|
from what i gathered, you don't have to touch the stock gearing for the zetec conversion. In fact, I may be wrong here, but i think darryl at AA trans runs stock gearing in his and rebuilds tranny's for a living. |
|
Back to top |
|
|
boulderdrop Samba Member
Joined: February 06, 2008 Posts: 481 Location: Seattle, WA
|
Posted: Fri Feb 05, 2010 2:39 pm Post subject: |
|
|
@Candyman : Bostig says they haven't changed the gearing in any of their test vans and that the stock gearing works well. Daryl at AA Transaxles says that it's not needed for the Zetec, but that it can be improved slightly with a taller 3rd and shorter 4th. He said he's had good results with the taller 3rd and hasn't heard much about the 4th yet. He runs this setup in his Syncro and likes it, saying that the taller 3rd is nice for downshifts from 4th.
Last edited by boulderdrop on Fri Feb 05, 2010 2:53 pm; edited 1 time in total |
|
Back to top |
|
|
wasserbox Samba Member
Joined: April 08, 2008 Posts: 533 Location: Durango, CO
|
Posted: Fri Feb 05, 2010 2:44 pm Post subject: |
|
|
boulderdrop wrote: |
but that it can be improved slightly with a taller 3rd and shorter 4th. |
Maybe a stupid question - but when it's referred to as Taller and Shorter - does that mean a Physically taller gear that would be easier to spin, but lower speeds at the wheels...
Or does that mean taller figuratively, as in harder to push (more HP) but faster at the wheels? |
|
Back to top |
|
|
anthonywesty Samba Member
Joined: May 06, 2007 Posts: 107 Location: Sunshine State
|
|
Back to top |
|
|
WBX man Samba Member
Joined: September 06, 2006 Posts: 94 Location: Copenhagen, Denmark, Europe
|
Posted: Fri Feb 05, 2010 2:47 pm Post subject: |
|
|
If you choose the optimal gear ratio, the maximum speed you can reach with 130 hp is in the range of 100-105 mph due to the wind resistance.
It is calculated from the drag coefficient and front area. _________________ 2,1 DJ WBX Vanagon/ T3 with Megasquirt/ Renault-Lotus UN1 gearbox/ 320 mm AMG front brakes/ 280mm Eurovan rear brakes
My recent projects:
http://www.t3nettet.dk/viewtopic.php?p=6342#6342 |
|
Back to top |
|
|
Vanagonner Samba Member
Joined: September 15, 2009 Posts: 506 Location: Broomfield Colorado
|
Posted: Fri Feb 05, 2010 2:49 pm Post subject: |
|
|
Keeping stock gearing sounds very sensible to me. If you really want to use all that rpm, you could put in a an n/a diesel transaxle .
That would look like (in 4th) about 71 mph at 4500 rpm, 84 mph at 5300 rpm, and 107 mph at 6750 rpm, I think.
1st? you'll be thru it before you have a chance to finish blinking. _________________ Sage
'82 Westy 1.6 D
the mighty n/a
Last edited by Vanagonner on Fri Feb 05, 2010 3:08 pm; edited 1 time in total |
|
Back to top |
|
|
boulderdrop Samba Member
Joined: February 06, 2008 Posts: 481 Location: Seattle, WA
|
Posted: Fri Feb 05, 2010 2:51 pm Post subject: |
|
|
@wasserbox : I believe that a "taller gear", is physically bigger and has a ratio that's closer to 1:1. So, it would cause the RPM's to be higher for the same speed. Like shifting into a "taller gear" on a bicycle. |
|
Back to top |
|
|
WBX man Samba Member
Joined: September 06, 2006 Posts: 94 Location: Copenhagen, Denmark, Europe
|
Posted: Fri Feb 05, 2010 2:56 pm Post subject: |
|
|
boulderdrop wrote: |
@wasserbox : I believe that a "taller gear", is physically bigger and has a ratio that's closer to 1:1. So, it would cause the RPM's to be higher for the same speed. Like shifting into a "taller gear" on a bicycle. |
The other way around... taller gears makes you go faster with same rpm's _________________ 2,1 DJ WBX Vanagon/ T3 with Megasquirt/ Renault-Lotus UN1 gearbox/ 320 mm AMG front brakes/ 280mm Eurovan rear brakes
My recent projects:
http://www.t3nettet.dk/viewtopic.php?p=6342#6342 |
|
Back to top |
|
|
anthonywesty Samba Member
Joined: May 06, 2007 Posts: 107 Location: Sunshine State
|
|
Back to top |
|
|
HeftySmurf Samba Member
Joined: June 15, 2008 Posts: 879 Location: Washington, USA
|
Posted: Fri Feb 05, 2010 3:01 pm Post subject: |
|
|
I put a taller 3rd in mine..... the van is most fun to drive in 3rd.
And yes a shorter 4th would help the free driving.
I feel like I have no acceleration in 4th on the highway.
I recommend you speak with Daryl at AA he will answer any question concerning this, and he is an expert.... He has a Zetec, and rebuilds transaxles....
Running 215/75/15s _________________ -Lorenzo
90 GL w/ Bostig
Last edited by HeftySmurf on Fri Feb 05, 2010 3:33 pm; edited 1 time in total |
|
Back to top |
|
|
vwlovr Samba Member
Joined: May 21, 2006 Posts: 1122 Location: on the road
|
Posted: Fri Feb 05, 2010 3:19 pm Post subject: |
|
|
yeah, my case is a bit diff. because i have very tall tires 215/75/16's i ended up going with a shorter 3rd and 4th. i could see on a stock tire van the tall 3rd and short 4th being nice. the zetec does not like to be lugged, but loves to be rev'd. i would have just changed the R/P because of the tires, but i couldn't get approval from my CFO for a front and rear rebuild
what i do love about my shorter 3rd is that 2nd to 3rd is awesome. climbing a hill i don't lose any momentum in that shift and it powers up smoothly after getting into 3rd. that's what would worry me about a taller 3rd, it seems like the stock gap from 2nd to 3rd is already big enough.
before i made the change it wasn't too bad, but i just had to drive like 80+ to be comfy in 4th. with stock or near stock tires i can imagine that the gearing is pretty close to good with the zetec.
i don't have the ratios i used with me, but like i said, my tires are big, so it's not really apples n apples. |
|
Back to top |
|
|
Christopher Schimke Samba Member
Joined: August 03, 2005 Posts: 5375 Location: PNW
|
Posted: Fri Feb 05, 2010 4:02 pm Post subject: |
|
|
vwlovr wrote: |
what i do love about my shorter 3rd is that 2nd to 3rd is awesome. climbing a hill i don't lose any momentum in that shift and it powers up smoothly after getting into 3rd. that's what would worry me about a taller 3rd, it seems like the stock gap from 2nd to 3rd is already big enough.
|
Having experience with a taller third and fourth in a SVX powered Vanagon, I can tell you that the gap in gearing between second and third that occurs with the taller third gear is really annoying. The jump is just too great to be comfortable.
When engine RPMs in second gear dictated a shift to third, the massive RPM drop meant that the engine RPM was reduced to a point in the torque curve that made anything below that RPM less useful. In other words, suppose you are cruising along in second gear near the top of the RPM range and then shift to third gear. The engine RPM drops so much that you must maintain that current RPM to keep the engine in the torque curve. If you reduce the engine RPM (slow down) in third gear at all from that point, the RPM drops so far into the torque curve that you have no choice but to shift back into second gear to create any usable torque. In my opinion, that loss of drivability is not acceptable. And yeah, I did make it seem more dramatic than it really is, but I did so just to illustrate the point.
If it were my choice, I would leave the stock gearing in place and fine tune the "gearing" with tire diameter. This keeps the gear spread in an acceptable range while still reducing your cruise RPM slightly. _________________ "Sometimes you have to build a box to think outside of." - Bruce (not Springsteen)
*Custom wheel hardware for Audi/VW, Porsche and Mercedes wheels - Urethane Suspension Bushings*
T3Technique.com or contact me at [email protected] |
|
Back to top |
|
|
crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9895 Location: Orbiting San Diego
|
Posted: Fri Feb 05, 2010 4:23 pm Post subject: Re: Question: Transaxle Gearing and Bostig-Zetec |
|
|
These speeds at 5300rpm all look about 10% too fast for that tire size and stock gearing. Did you enter the ring and pinion ratio correctly?
In any case, if you are upgrading from a 1.9 you should find the stock gearing with Zetec a big improvement. A Zetec from the 2.1 is not so dramatic until you get higher in the rpms.
Mark
boulderdrop wrote: |
Van's Tires:
Sizes: 205/65/16
Diameter: 26.5"
Circumference: 83.2"
Rev/Mile: 761
Stock Transaxle Gearing (i think):
1st:3.78
2nd:2.06
3rd:1.23
4th:0.85
Stock Gearing with 5300 rpm:
1st with 3.78 ratio = 25.12 mph
2nd with 2.06 ratio = 46.10 mph
3rd with 1.23 ratio = 77.21 mph
4th with 0.85 ratio = 111.72 mph
................
Corrections, thoughts, experiences? |
|
|
Back to top |
|
|
Williamtaylor33 Samba Member
Joined: September 07, 2007 Posts: 1545 Location: Arkansas
|
Posted: Fri Feb 05, 2010 5:16 pm Post subject: |
|
|
Thats one of the biggest advantages with the bostig conversion. No gearing changes needed.
I think it would be sweet to hook on of those engines up to a 5-speed that was geared right...a 2wd 5-speed that is. One of the european trannys.
and i'd put a "0.70 ratio = 172.78 mph" in the 5th gear so i could get we're i'm going alittle bit faster. I didnt know the ford could provide this level of performance. _________________ 89 Bostig powered syncro westy |
|
Back to top |
|
|
J Charlton Samba Member
Joined: August 24, 2007 Posts: 1544 Location: The True North Strong and Free
|
Posted: Fri Feb 05, 2010 5:49 pm Post subject: |
|
|
A couple of useful formulae - I guess one has to figure it out from the speed at which their engine will be generating the torque they want.
rpm = (gear ratio X R&P X mph X 336 ) divided by tire ht (inches)
mph = (RPM X tire ht in inches) divided by (gear ratio X R&P X 336)
gear= (RPM X Tire Ht) divided by( R&P X mph X 336)
Eg if you wanted max torque at 4500 with a Bostig with a 4.53 R&P while you were travelling at 90mph (why???) then your final gear drive would be .83 Stock is .85 so 4500 rpm is probably going to give you about 88mph. I think I did this using 27" diameter tires. _________________ NAHT hightop availability May 18 2023 -
Bend Oregon - for Oregon, California- (7 tot , 3 available), Kennewick Wa (6 tot, 3 available), Small Car Performance Fife Wa. (7 tot 5 avail ), Fairbanks Alaska (1 tot 0 avail)
Future availability TBD : Springfield Mass. Staunton Va, Florida, Colorado, Grand Junction Co., SLC probably late 2023 |
|
Back to top |
|
|
AndyBees Samba Member
Joined: January 31, 2008 Posts: 2312 Location: Southeast Kentucky
|
Posted: Fri Feb 05, 2010 8:26 pm Post subject: Engine transplants and gearing |
|
|
I'm in the process of building a Vanagon tranny for a VW TDI engine transplant into my '84 non-Westy. The tranny is from the Air-cooled model with the DK code, 4.57:1 ratio Ring & Pinion. (Yes, I have addressed the difference in the shifter linkages.)
I've got a fairly detailed Excel spreadsheet set-up for the purpose of playing around with various gear ratios, tire sizes, rpms, mph, etc.
To me, a more powerful engine (hp and torque) cranking-out high RPMs in top-gear at say 65 mph is "wasting" that engine..... and wasting fuel. Your oil would need to be changed based on the RPMs logged as opposed to miles driven!
To use the "stock" Vanagon tranny gearing (which could be one with a Ring & Pinion from 4.57:1 to over 5.5:1) depending on which model you have, would be like driving my Jetta TDI at 70 mph and never shifting into 5th gear.
So, after considering the "universe" of options (tire size, tranny gearing, R&P, and engine), I come to the conclusion that the DK tranny with the 4.57:1 R&P would be satisfactory for my application with the upgraded 3rd and 4th gears (taller). I went with the 0.77:1 ratio 4th gear (stock is 0.85:1) and the 1.14:1 3rd gear (stock is 1.23:1). Data was based on using 205/75/15 tires (744 revolutions per mile).
Side note for those trying to understand the jargon: When the main shaft (input from the engine) gear has a larger diameter than the pinion shaft mating gear, that's considered "tall" (and could be considered an overdrive ratio). As that relationship is changed/upgraded, larger main shaft gear, the "taller" the gearing. Example: a 1:1 ratio is not as "tall" as a 0.85:1 ratio. Also, the ratios are in reference to revolutions which is based on the number of teeth on each mating gear.
Based on the spreadsheet and graphs from the data, it appears the engine will be turning about 2850 RPMs at 65 mph. The engine can more than handle the higher geared 3rd (taller for those who don't understand) when down-shifts on hills become necessary (slope, traffic, on board load, head wind, combo, etc.). If there is a need for additional cruising RPMs, going back to 14 inch wheels or even the 185 tires will be easy options. Side note: 70 MPH would only require slightly over 3100 RPMs.
Also, based on the RPM "drop" between gears, with the TDIs peak torque at just over 1900 rpms, there should not be any issues.
My transmission rebuild will be finished this weekend. I will commence the process of addressing engine mounting next week. I did the wiring harness a year ago ...... I hope I remember the details in my notes...
As some friends and I have discussed, the "on-paper" data and real world data don't always equal. So, the available option of tire size can be very helpful.
Hope this clears up some things for those trying to learn! |
|
Back to top |
|
|
AndyBees Samba Member
Joined: January 31, 2008 Posts: 2312 Location: Southeast Kentucky
|
Posted: Fri Feb 05, 2010 9:19 pm Post subject: Re: Question: Transaxle Gearing and Bostig-Zetec |
|
|
boulderdrop wrote: |
I'm getting everything together to drop the Bostig conversion into my 84 Westy, but I'm having troubles understanding why some people would change the gearing for the rebuilt transaxle that I'm getting. The new Ford Zetec 2.0L engine, rev's much higher than the old 1.9L WBX and I'll need to run the rpm's much higher to get the same torque/bhp. Here's the data...
BASELINE PERFORMANCE DATA AND OPTIONS
Zetec engine's performance:
HP: 130 at 5300rpm
Torque: 135 at 4500rpm
Redline: 6750rpm
Van's Tires:
Sizes: 205/65/16
Diameter: 26.5"
Circumference: 83.2"
Rev/Mile: 761
Stock Transaxle Gearing (i think):
1st:3.78
2nd:2.06
3rd:1.23
4th:0.85
Ratio Upgrades available from "AA Transaxle":
3rd Gear: 1.18. 1.14 & 1.09
4th Gear: .77 and .70
PERFORMANCE WHEN CHANGING THE GEARING
I've been playing around with a cool transmission-calculator, trying to get my head around what it means to change the gearing:
http://www.fatboyraceworks.com/gears/
Stock Gearing with 5300 rpm:
1st with 3.78 ratio = 25.12 mph
2nd with 2.06 ratio = 46.10 mph
3rd with 1.23 ratio = 77.21 mph
4th with 0.85 ratio = 111.72 mph
Changing the 3rd gear ratio's, yields the following:
1.23 ratio = 77.21 mph (stock)
1.18 ratio = 102.50 mph
1.14 ratio = 106.09 mph
1.09 ratio = 110.96 mph
Changing the 4th gear ratio's, yields the following:
0.85 ratio = 111.72 mph (stock)
0.77 ratio = 157.07 mph
0.70 ratio = 172.78 mph
QUESTIONS
Now these MPH are ridiculously fast and obviously not real-world, but I'll need to keep the RPM's much higher than the WBX. I usually drive in 3rd gear and this takes me up to about 64 mph in the real world.
Q: If I move to a taller 3rd with a 1.18, that'll take my theoretical top-speed from 77 mph to 102.50. But it might impose a "lugging" down of the engine when shifting from 2nd to 3rd, while I wait for the engine to spool up the rpms.
Q: If I just change the 3rd, but leave 4th the way it is... I would keep my top speed of 111 mph, which is fast enough and (I would think) would have more guts for the inclines, as the rpms would still be high... but I could probably stay in 3rd all-day-long, up/down the pass.
Q: If I changed 3rd with a 1.18 and 4th with a 0.77, it seems that 3rd would be were I was at all the time and 4th would just be a highway gear for long-straight-flat roads.
Corrections, thoughts, experiences? |
I've wrestled with gearing, RPM, and speed numbers for months and months for my own purposes. I've discussed the various possibilities with several individuals with experience on the matter, etc.
So, I'm thinking there is something wrong with the speeds you are getting in the various ratios in 3rd gear..... notice the skip between the 1.23 ratio and the 1.18.... then on to the 1.14, etc. Assuming you didn't change something in the data, the MPH cannot be correct. ...??
.....and there maybe something wrong with the 4th gear examples too, even with the top speed in the .70 4th gear!
With much taller tires (726 revs per mile) at 5300 rpms and .70 4th, my spread is showing 137 mph..... big difference!
Check your numbers again, and report back!
Edit: Lastly, you say that you drive in 3rd gear at 64 mph. Well, for example, with 205/75/14 tires and stock tranny that come in a 1.9 WBXer, your talking 4750 RPMs to achieve 64 mph in 3rd gear ....... your engine cannot stand that very long. Also, the Vanagon Speed-O-meters are terribly off base (they over-state speed big time). You may not really be going as fast as you think you are.
My Garmin is within 1 MPH (+or-) with the speedo in my Jetta and the OBD ScanGauge mph reading, as well as DOT road-side radar displays and timed driving.
So, considering they are that closely in sync, move the Garmin to my '84 Vanagon, 1.9, it tells me that I am doing 65 mph when the speedo says I'm doing 80 ... the tach is at 3650 at that speed (65 mph). |
|
Back to top |
|
|
J Charlton Samba Member
Joined: August 24, 2007 Posts: 1544 Location: The True North Strong and Free
|
Posted: Sat Feb 06, 2010 8:11 am Post subject: gearing |
|
|
Woohoo _ this is a great calculator http://www.fatboyraceworks.com/gears/
Here are some gear ratios for a couple of vanagon trannys to play around with.
ABD - (standard vanagon tranny) 1st 3.78, 2nd 2.06, 3rd 1.26, 4th .85
final 4.57
3H (common diesel vanagon tranny from Europe) - easy enough to convert to gas 1st 4.11, 2nd 2.33, 3rd 1.476, 4th 1.023, 5th .816, final 4.83
Whatever tire size you plug in to the calculator, or whatever max rpm you put in (that you're comfortable running your engine at) - it becomes pretty obvious, at least to me, that the gap that exists between 2nd gear and last gear will be handles much better with a 3rd and 4th gear in there.
No wonder the 5 speed transmissions were pretty much the standard offering in Europe. _________________ NAHT hightop availability May 18 2023 -
Bend Oregon - for Oregon, California- (7 tot , 3 available), Kennewick Wa (6 tot, 3 available), Small Car Performance Fife Wa. (7 tot 5 avail ), Fairbanks Alaska (1 tot 0 avail)
Future availability TBD : Springfield Mass. Staunton Va, Florida, Colorado, Grand Junction Co., SLC probably late 2023 |
|
Back to top |
|
|
climberjohn Samba Member
Joined: January 11, 2005 Posts: 1840 Location: Portland Orygun
|
Posted: Sat Feb 06, 2010 8:37 am Post subject: |
|
|
Hi Volks,
This is a great thread! Wowzer, so many knowledgeable posters chiming in!
I emailed Darryl (AA Transaxle) a few weeks back with this exact question. His response is below.
Suggestion: Go visit Darryl, as you are both in the Seattle area, and maybe drive a van with both a stock tranny and one with different gearing and see what you think? I'm sure he could refer you to local customers who would be glad you show you their rides. Ask them about Loogie's concern with torque curve when shifting from 2nd to 3rd and back again.
from Darryl:
For most..re-gearing is not a priority and stock works ok..esp if your
budget is tight... Pass vans with no extra weight do better power wise and really are fine with stock gears.
I have driven 8 or more Zetec conversions incl my own Syncro Westy and have a good feel by now.
The Zetec is a higher revving motor and gets it Hp at the 3000 + RPM and redlines at 7K..
With a heavy van, like a Westy, you sometimes wish 4th had more oomph right after shifting from 3rd on a hill. Granted when you drop into 3rd on a long hill, the eng revs at about 5500, but it doesn't really care and will just purr at that speed for miles if you want it to.
Most do prefer to run any eng at a lower speed, so my suggestion is to put in a taller 1.18-3rd and a LOWER .82-4th gear..Sounds bassackwards, but it keeps the eng at its power curve without changing things very much..200 rpm higher and 200 rpm lower..
Lots of it is personal preference..Everyone I put just the taller 3rd into commented the lower 4th would have been nice to do at the time.
_________________ '86 Westy, 2.5 Subaru power
Know your limits. Exceed them often. |
|
Back to top |
|
|
|