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Automatic transmission Bus / cams experiences?
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pablovent
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PostPosted: Sat Oct 14, 2017 4:36 am    Post subject: Automatic transmission Bus / cams experiences? Reply with quote

Hello,

I have read a lot of information about different cams in buses with automatic transmission, it seems that things are somewhat different from the manual transmission, there is also information about the different TC alternatives.

There are very few buses with automatic transmission in the world, it would be great to know other similar experiences to get a better and real idea of the mysterious subject.

Any info is grateful!!

Best.
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Gregg in the 603
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PostPosted: Sat Oct 14, 2017 3:48 pm    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

Actually, there are more automatics than you think. I'm always surprised how many there are. Mine is bone stock all around, nothing special on the cam and the TC is as stock as it gets too. And it's freaking awesome!
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1979 Mexico Beige Westy auto
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orwell84
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PostPosted: Sat Oct 14, 2017 6:13 pm    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

I have a 73 with a stock automatic. The Bentley does specify a different cam for the automatic. I have run it with a rebuilt engine with a stock manual cam and am currently running a Web 73 cam, which was an improvement. I don't think the autotrans is all that pciky, it's happy with a strong engine. I have heard people recommend using Vanagon TC's but I don't remember the reason.
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raygreenwood
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PostPosted: Sat Oct 14, 2017 9:18 pm    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

orwell84 wrote:
I have a 73 with a stock automatic. The Bentley does specify a different cam for the automatic. I have run it with a rebuilt engine with a stock manual cam and am currently running a Web 73 cam, which was an improvement. I don't think the autotrans is all that pciky, it's happy with a strong engine. I have heard people recommend using Vanagon TC's but I don't remember the reason.


Actually the auto trans is a little picky about cam. Its not rpm range its looking for. Its vacuum signature for the modulator.... if it has a vacuum modulator. If not...it may not be picky. How having the wrong or poor vacuum signature affects shift point...I am not even sure you may feel it in a loaded bus....but in a smaller/light automatic equipped car....its harsh.

The vanagon TC....is better because it has a higher stall point allowing you to rev the engine higher to take off from a stopped position before lockup....to a point where the engine is producing a little bit better advance and power. Less stumbles off the line. May be slightly smoother decoupling when coming to a stop as well. Ray
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WhirledTraveller
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PostPosted: Sun Oct 15, 2017 6:20 am    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

Only early automatics have the vacuum modulator. The 010 transmissions don't have it so don't care about the vacuum signature.

I am running a Raby cam, it's not specific to automatics and works fine. I'm also using the later Vanagon style torque converter with the higher stall speed. It makes a noticeable improvement in performance because it gets the engine further up into the power band, at the expense of more slipping so probably a bit more inefficiency and heat.

One thing I've noticed with the automatic, you need good power between 2000 and 4000 RPM. Less than 2000, don't care because the torque converter, 4000+ don't care because the automatic never really lets you get much higher. But there are some big steps between 1 and 2, and 2 and 3, so you can't pick the perfect gear to keep the engine right on the power peak, so the power between 2000 and 4000 needs to be solid throughout. If I was designing a cam for an automatic that would be my criteria. So, a setup that makes more power than stock over 3000 RPM but less power than stock under 3000 RPM may be a wash. With my "Camper Special" type setup, I did find myself in the situation going up and over a steep mountain pass where first gear would wind up right to the rev limit no problem, but 2nd gear couldn't hold because the RPM jump and power difference was too great. This was before the new torque converter, which should help.
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1977 Westy, Automatic. Big Valve heads, CS Cam.
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pablovent
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PostPosted: Mon Oct 16, 2017 4:44 am    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

Additional data;

the type 4 in it's various applications (411/412, 914, or kombi), came with a few different stock camshafts. Their caracteristics are different from each other, it's not only "duration". Overlap probably biggest difference, split duration, and ramp shape and lift.

The stall speed of the torque converter will be matched with a "performace" camshaft. With the automatic baywindow, VW simply used a part which they already had, from the type 3 automatic and 411 car. This converter has a stall speed of only 1900rpm. Code stamped next to one of the 3 mounting "ears" on that torque converter could be "D".

According to VW's spec, 3-speed automatic kombis already have reduced pullaway and hillclimbing ability in first gear to begin with, compared with the 4speed manual.

With the first few heavy 80's shape "Vanagon" shape buses especially when loaded, VW realised they have a problem. Pulling away in 1st, engine would sit at very low rpm for a long time, and there was no lower gear to change down to. So VW changed the torque converter to one with a higher stall speed to solve this problem. Code "Z" and "H" has stall speed around 2500-2700, (Instead of 1900 rpm), which is closer to torque band. This was be from a late 80's WBX engine. There was also an "inbetween" torque converter, marked "K", stall speed 2200rpm.

Even with standard cam engines, official advice was to change to the later torque converter. These also worked well with higher rpm engines, like wbx 2.1.

Camshafts and followers are mostly reground to standard kombi spec.

"Stock timing of CJ 2l vw bus camshaft, vw's spec at 1mm lift:
Inlet open: 2 deg btdc, closes 35 deg abdc
Exhaust open: 35 deg bbdc, closes 5 deg atdc


Stock timing of 411/412 and 914 car which had D-jetronic fuel injection:
Inlet open: 12 deg btdc, closes 42 deg abdc
Exhaust opens: 43 deg bbdc, closes 4 deg atdc

Stock timing of 411/412 twincarb and 1700 manual kombi:
Inlet open: 4 deg btdc, closes 39 deg abdc
Exhaust opens: 40 deg bbdc, closes 3 deg atdc


Stock timing of CU 2L vw bus hydraulic cam at 1mm lift:
Inlet open: 2 deg btdc, closes 33 deg abdc
Exhaust open: 36 deg bbdc, closes 3 deg Btdc (before, not after tdc).
(This hydraulic CU cam is lazier than the mechanical CJ cam, because of exhaust valve closing earlier for Californian emission purposes. Torque dropped from 143Nm @ 2800 rpm to 137Nm @ 3000rpm with this cam, despite the CU engine also having high-energy ignition system and slightly richer jetting).

Remember that there are also differences in ramp steepness and total lift, of which specs were not always available from vw.
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dawie
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PostPosted: Mon Oct 16, 2017 11:38 am    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

Previous post on same subject:
https://www.thesamba.com/vw/forum/viewtopic.php?t=687608&start=0
Basically Pablovent is from Chile where conditions are very different to the USA. He is unhappy with the reduced torque at very low rpms after fitting a CB2201 cam. He prefer to keep his original low-stallpoint converter.
Info in above post seems partly copied and pasted from another forum where he also asked for advice. Probably because of the language difference there are some mistakes in above post compared to my original answer on the other forum. like the word "matched", which was "mismatched" in the original answer.

In short, one option would be the Web 142.
If possible have Web grind both the inlet and exhaust lobe using only the inlet's profile. That way there will be slightly more exhaust duration and lift compared to the split 142 cam.
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Wildthings
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PostPosted: Mon Oct 16, 2017 12:22 pm    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

The Type 4 cars were notorious for burning up automatic transmissions, with basically the same engine and transmission as early Type 4 powered buses had except for a longer final gear ratio. The higher stall speed "H" and "Z" torque converters actually end up lowering the tranny temperature because the engine can get the vehicle moving much more quickly instead of the TC just heating the oil while the vehicle sluggishly moves ahead.

As I have told Pablovent in another thread, I believe he needs a cam which is slightly more aggressive than stock coupled with one of the later torque converters. I last bought a torque converter about a dozen years back, it cost me $80 US at the time. Have no idea what shipping would be to Chili.

If he hasn't done so he needs to call John at Aircooled.net and to call The Type 4 Store. These are two of the principle go to places for Type 4 cams.
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pablovent
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PostPosted: Mon Oct 16, 2017 1:01 pm    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

My apologies Dawie,

I post this new thread try to looking for another T4 autotrans westys experiences (010) specifically, that information is poor on the web, original thread I was looking CJ code engine specifications ...


My best.
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pablovent
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PostPosted: Mon Oct 16, 2017 1:16 pm    Post subject: Re: Automatic transmission Bus / cams experiences? Reply with quote

yes, replace the stock "D" TC is a possibility for sure, match with improved cams, and appreciate this information, make a sense for me.... But im pretty sure my westy worked fine in its beginnings for many years with stock specs.

A few years ago rebuilted the tranny completly, and refresh the stock D code TC also (expensive).

I think must to have many another stock autotrans Westys T4 owners run in the streets, just i want keeping close to stock cam numbers.

Best
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