Issues With Performance Engine in Autotrans FI Bus

[Boxcar]

Since timing with the 28°btdc procedure I have found a new realm of power above 4000rpm.
Where it seems there were about 600 more rpm tucked away up there that I just discovered.
It seems to have more headroom above 4600. But @ 4600rpm though I can flow along with traffic.
What is the redline with an engine such as mine?

[Amskeptic]

57 mph in second gear with an 003 automatic 1800 is 5,400 rpm with the 4.45 rear axle and 1.59 second gear. p.s. that's the redline.

Be aware that high rpm throttle lift-off gives more effective compression braking than at slower rpms and increased aerodynamic effects will drag your speed down when you release the throttle.

A stock 1800 engine/autobox will give you the best horsepower at 51 mph in 2nd, the upshift will then put you at the torque peak in 3rd. That makes 51 the most sensible shift point when you are in some kinda scalded cat hurry. Please feel free to make your new cruising speed 62 to 65, and give your ears some time to adjust. You will find that it attacks hills much better when you are already above the torque peak.
Colin

[Boxcar]

Thanks Colin, for confirming my sense of engine braking seeming far greater above 4k.
NEW CS senstations after a year!

A.) Would selecting second through the stick be the way to have 51mph in 2nd?
B.) Shifts are controlled by a governor and vacuum modulator, yes?

3 > 2 kickdown seems like a JAM! through the powertrain @ 40 mph.
Imagery = stomped-on kitty. I haven't been a fan.

Should I stick select 2nd to omit 3rd to my liking? Or is vacuum modulator possibly tweakable?:bounce:

[Amskeptic]

A.)Would selecting second through the stick be the way to have 51mph in 2nd?
What to do there?Swami?

Make sure your kickdown is functional. You do not do 51 mph shifts but twice a year or so.
Colinswami?
(try Colinswampy >FLdownpourSurvivor)

[Bleyseng]

Running the rpms up to 5000 is fine with that setup as it can breath with the bigger valves and cam. In 2nd gear of a autobox seems a little too much but I do it in my westy 4 speed all the time.

[Amskeptic]

I see an edited post that I will respond to here.

Redline is 5,400 rpm.
Maximum horsepower for a stock 1800 FI is usually around 4,800 rpm,
but . . .
take it easy on your torque converter. If engine revs smoothly, OK, but if you get a little thrashy vibration coming up under the floor, you best settle down, ya pup, or we will be doing torque converter seals.

I told you what the hp/torque split was, the best shift point, decent cruising speed, now YOU have to go verify my assumptions about your rear axle ratio and 2nd gear ratio. You do that by getting your transmission #s and manufacturer plate assembly date, and any interesting history like the vehicle log where you might find gems like "08/13/86 - replaced automatic trans"
Colin

[Boxcar]

Running the rpms up to 5000 is fine with that setup as it can breath with the bigger valves and cam. In 2nd gear of a autobox seems a little too much but I do it in my westy 4 speed all the time.

Hi Bleyseng, I recall you. Either from the 914Club, or TS. Always a helpful man. I miss Mr Greenwood's posts a bit still.Schmaart guys all.
AHEM.

Regarding autobox 2nd...
My bit of discontent in trans tuning remains to soften/lower the downshift/kick down point from 3 > 2.
I am on speaking terms with the 003 trans's vacuum accumulator. General up shifting is quick,a bit on the harder side of crisp, but once fully warm I can modulate this a bit with some subtle throttle foot anticipation.
The 3 > 2 shiftpoint though is in need of less subtle massaging. I realize I may manually overide that upshift to 3rd, but what I would like IS to be able if not a "blasphemation" to get the throttle wide open in 3 and use some of the 2800 rpm torque curve@ around 35/36 mph.
Roughly now when in third, and climbing, WOT near the 3 > 2 shift point, it dumps into second at the scalded kitty section of second's range.
As I write I visualize this being both hard to explain, and hard to adjust out.
I would like the 3 > 2 downshift to happen around 35/36mph, not 38 or 39/or40 where I feel an abuse of the poor little 003* There I said it.

(*I have both the T Shirts from that rebuild,and TC shopped out rehab)

[Boxcar]

I see an edited post that I will respond to here.

Redline is 5,400 rpm.
Maximum horsepower for a stock 1800 FI is usually around 4,800 rpm,
but . . .
take it easy on your torque converter. If engine revs smoothly, OK, but if you get a little thrashy vibration coming up under the floor, you best settle down, ya pup, or we will be doing torque converter seals.

I told you what the hp/torque split was, the best shift point, decent cruising speed, now YOU have to go verify my assumptions about your rear axle ratio and 2nd gear ratio. You do that by getting your transmission #s and manufacturer plate assembly date, and any interesting history like the vehicle log where you might find gems like "08/13/86 - replaced automatic trans"
Colin

Good Idea Colin,
I kind of recall having checked my FD ratio. It was I thought the shortest in all the land...But I will make another inquiry down below there.
I forget seeing the trans ID#. Maybe I will scout around when/if I get some hints/cautions about possible adjustment to the vacuum accumulator which I posed on my previous post here.
Thanks again Colin and Bleyseng

[Amskeptic]

Maybe I will scout around when/if I get some hints/cautions about possible adjustment to the vacuum accumulator which I posed on my previous post here.
Thanks again Colin and Bleyseng

Maybe you will listen to me instead of all of those hothead performance freaks like Bleyseng (what IS his hurry anyway? )

All performance cams reduce intake manifold vacuum, especially at idle. For FI engines, this means you get a lousy cold start/warm-up idle, and sometimes a lousy warm idle (the air flow meter needs FLOW that performance cams cannot provide).

Reduced intake manifold vacuum with an automatic transmission makes the modulator erroneously order a) harder shifts b) higher up the rev range. That's what they do, they determine the shift points and engagement pressure based on vacuum signal
(high vacuum = low load = soft slow speed shift)
(low vacuum = heavy load = hard high speed shift that you don't feel because load absorbs it)

Because automatics are under load in gear at a stop, I do not recommend "performance" cams in an automatic transmission bus.
Colin

[Bleyseng]

Nor do I but since he has one he needs to work around it. I'd try adjusting the warm engine idle upto to 1050 rpms and see how that works.
Haha, yep I am just a speedfreak! I just want more hp than what VW gave us OEM as it wasn't enough when they came out new! Although my Ghia with it's 1600SP is just fine OEM. The 914 2.0L stock was too weak....

[Boxcar]

Thanks all for reccomendations.

Shift points are manageable. I never drove a flat four auto before. Stated differently shifts are quick, and there is no sense of any slipping which is desireable.
My one undesireable area which I would not turn anyone else loose with this Bus on is the kickdown point being too fast in3rd, and way too fast in second.
Of course I can drive around the severe downshift by gauging hills etc.

A.)How does the vacuum accumulator adjust + or - or if at all to lower 3>2 kickdown
B.). Or to make it LESS likley to shift down is more better. To stay in 3 rd at 39..38...37 rather than shift into 2 ?
Is that a kickdown switch function, or vacuum accumulator function?

[Amskeptic]

Thanks all for reccomendations.

Shift points are manageable. I never drove a flat four auto before. Stated differently shifts are quick, and there is no sense of any slipping which is desireable.

I have driven many many automatic buses, and they can be remarkably smooth and unobtrusive.
At light throttle they hit 2nd at 10 mph and glide into 3rd at barely 30. They will immediately downshift into 2nd if you apply the accelerator at 30 and they will stay in 3rd once you are closer to 40 and up.
The "kickdown point" is not a "point". Your floored accelerator executes the kickdown.

My one undesireable area which I would not turn anyone else loose with this Bus on is the kickdown point being too fast in3rd, and way too fast in second.

What do you mean?
A "point" is not a "fast" or "slow" thing, it is a moment.
Is the vehicle shifting too late into 3rd on the upshift?
Is the vehicle shifting too soon into 2nd on the downshift?
Is the shift too firm? Spell it out. I think our discussion upo to this point actually has spelled out as clearly as you are likely to get, what is going on.

A "kickdown" is a decision. Does the transmission actually knock it down into 2nd at your floored accelerator command at 40 mph? THAT is a kickdown. And if you left your foot into it, it should stay in 2nd until 50 mph. BUT! If it violently shifts down at too high of a speed for your light accelerator position, I think we discussed that your vacuum signal is inadequate. I will blame your camshaft, but make sure your vacuum signal is optimal, nooooo leaks.

Of course I can drive around the severe downshift by gauging hills etc.

You mean, by loading up the engine so the shift is absorbed by increased work?

How does the vacuum accumulator adjust + or - or if at all to lower 3>2 kickdown
Or to make it LESS likely to shift down is more better.

"less likely is more better" I shouldn't give you any indication that I understood a damn thing here, but
what you are asking is:
"how can I fool the modulator into thinking there is more vacuum than is actually available?"
Well, try to optimize whatever vacuum the engine is generating:
*increase idle timing
*ensure NO vacuum leaks, even the dipstick
*clean out vacuum modulator nipples on both ends use a larger vacuum hose (if 4mm use 5mm and use a sleeve on the nipples for a tight fit

Please understand that the vacuum modulator may very well be plumbed into the brake booster circuit, and you HAVE to check the integrity of the entire circuit. A leaking brake booster can cause violent shifts, or any leak along the entire run, including the wye in the engine compartment. As I remember, the vacuum modulator is teed off the brake booster downstream of the one-way valve under the car over the driveshaft. But you already know your modulator right? So where does it get its vacuum.
If it does tee off the brake system, can your brake booster give you an assisted pedal after five minutes or does it lose it after only 20 or 30 seconds?

If everything is definitely excellent, then call your VOLKSWAGEN 003 EXPERT and make damn sure you are communicating with clarity exactly what your issue is.
"My engine has a modified cam that has reduced my vacuum signal, now the vacuum modulator is banging out shifts as though I were flooring it all the time. Can I adjust it?"

Is that a kickdown switch function, or vacuum accumulator function?

Vacuum damn accumulator? This ain't no Lincoln, this ain't no Benz!
But is the function of the vacuum modulator to stage the shift point speeds . . . .
Colin

[Boxcar]

Thanks Colin, I think I have very normal function based on your description of typical 003/Bus shifting.
Sleeving the modulator nipple for tighter fit, with a heat shrink tubing? Nice idea.Anyhow, it is plumbed in 4mm back to the FI plenum.

Your final automatic driving description of "sliding into third around fourty"is what I have.

What if any would adjustment of the screw in the vacuum accumulator have in getting non kickdown;non wfo;PARTIAL throttle downshifts THAT IS partial throttle in third NOT to ask for downshift to second until like 36mph? As it is, it shifts down more towards 40 with partial throttle. This is my interest.

[Amskeptic]

Thanks Colin, I think I have very normal function based on your description of typical 003/Bus shifting.
Sleeving the modulator nipple for tighter fit, with a heat shrink tubing? Nice idea.Anyhow, it is plumbed in 4mm back to the FI plenum.

Your final automatic driving description of "sliding into third around fourty"is what I have.

What if any would adjustment of the screw in the vacuum accumulator have in getting non kickdown;non wfo;PARTIAL throttle downshifts THAT IS partial throttle in third NOT to ask for downshift to second until like 36mph? As it is, it shifts down more towards 40 with partial throttle. This is my interest.

Do you have a Bentley?

Do all initial inspections operations as far as fluid level,
correct state of tune (good luck with your engine vacuum readings, what are they at idle anyway?)
correct throttle/shift linkage adjustments.
Pull off and plug vacuum modulator hose.
Install two pressure gauges at test connections, upper is main, lower is throttle.
At 1,000 rpm, the main pressure is to be 92 psi, the throttle pressure is to be 45 psi.
If throttle pressure is not correct, turn your hex adjustment screw inside the vacuum modulator vacuum nipple. As a general rule, turning clockwise increases pressure.

With vacuum hose on, your main pressure should be 47-50 psi and the throttle pressure should be 5-6 psi. Notice how the modulator DROPS the hydraulic pressure under the presence of vacuum to soften shifts. Notice too how the differential between the pressures INCREASES under the presence of vacuum, this moves the shift points down the rev range.

Do not to get all goofy with guesswork. I believe we have assessed the issue at hand. Utilize the internet, email and phone to get yourself informed as to others who may have walked down this road. If you see an opportunity to nudge adjustments or specifications, work the tolerances in your favor.

This thread is going to Transaxle . . .
Colin

[Boxcar]

Thanks Colin,
a Bentley,yes have that.
I will look but thank you for adding some insights to the autotrans pressure checks.

vacuum at idle was around 10# when I last checked in the fall(low yes). As I added aux air regulator it was less,but idle went up so around 10# still@ 1025/1050rpm.
Fuel pressure regulator was "disgruntled" issuing out of spec. fuel pressure, but proper according to present low manifold vacuum.
Pressure check of trans should be interesting though. I considered it before,but look forward to dialing it in to best advantage.