2-for-1 and possibly related: Bucking and unstable/nonidle

Bus, Microbus, Transporter, Station Wagon, Vanagon, Camper, Pick-Up.

Moderators: Sluggo, Amskeptic

Post Reply
User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Mon Feb 16, 2015 8:53 am

Ronin10 wrote:Haven't had a chance to straighten out my numbers yet (busy weekend), but did have the opportunity to play with different spring combinations in my 205P distributor, trying to make sure I have a centrifugal advance curve that makes sense. I never achieved spec (7.5 deg @ idle, 8-13 deg @ 1,600 and 20.5 - 24.5 deg @ 3,400 rpm - as given by OldVolksHome), but here's what my curve looks like: 8 deg @ idle; 8 deg @ 1,000 RPM; 16 deg @ 1,600; 18 deg @ 2,000; 20 deg @ 2,500; 24 deg @ 3,000; and 33 deg @ 3,400 RPM.

EDIT: I also received my shipment from German Supply so I removed my EGR and used the block off plate and swapped in the new brake booster tee. Morning drive in was pretty uneven. When the engine pulled smoothly it was really strong, but frequently it was interrupted with misfires either out the tailpipe or simple gaps in then engine pull. Will double check my valves as soon as I'm able.
As mentioned elsewhere in this site, we do not adjust the timing ever to meet idle needs. The critical timing is at the upper end 28*@ 3,200-3,400 rpm. As distributors wear, the range of movement increases, so we take from the idle side. The BobD engine, for example, is now down at 2* BTDC at idle. I can easily increase the idle airflow to nail my 950 rpm idle speed, so I don't care about less advance at idle. You care. You have to care, with that camshaft. BUT, do NOT increase timing at upper end to compensate. If you can narrow the advance range, great, 10* to 12*BTDC at idle increasing to only 28* would be good for that camshaft set up.
Colin
(ask Air-Cooled.net if they have a SVDA with that artificially narrowed range)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Mon Feb 16, 2015 9:51 am

Roger that. My only concern with idle is that it is relatively smooth enough to not die during decel/coming off an accel or when I come to a stoplight which sometimes happens now (although my AFM is admittedly off still and will soon be revisited...). I can back off the upper end no problem to get to 28 deg. This exercise was more to verify that my centrifugal advance was curved right after I rebuilt the distributor. It seems like I hadn't gotten the springs correct and this setup seems more in line with what I'd expect - more or less linear through the rpm range.

FYI, Aircooled.net is no longer making their Bosch SVDA due to a lack of acceptable rebuildable cores. They push you to the Pertronix SVDA. Any thoughts or comments on that distributor?
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
asiab3
IAC Addict!
Location: San Diego, CA
Contact:
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by asiab3 » Mon Feb 16, 2015 4:39 pm

Ronin10 wrote:This exercise was more to verify that my centrifugal advance was curved right after I rebuilt the distributor. It seems like I hadn't gotten the springs correct and this setup seems more in line with what I'd expect - more or less linear through the rpm range.

FYI, Aircooled.net is no longer making their Bosch SVDA due to a lack of acceptable rebuildable cores. They push you to the Pertronix SVDA. Any thoughts or comments on that distributor?
Did you bump (on purpose or on accident) the "limiting tabs" in the distributor during this? On an experimental 009 I had, I gently persuaded them inwards to limit the total timing from about 25* to 18* total. It made that distributor into a worthy spare from a paperweight. The Mallory distributors have these adjustable stops built in, though the recent years the tolerances has gotten looser from around 5+ years ago. I have a spare that I can curve any way you want if you'd like to try it out before modifying your good distributor. Just pay shipping.

I don't know what you would gain by going with a Pertronix SVDA unless it has been narrowed like Colin said. I will wager that your original distributor will outlast the Pertronix unit.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Mon Feb 16, 2015 8:11 pm

Limit stops?! There were supposed to be limit stops in there? I did crack open a 009 I had from a salvage yard and saw two vertical things I would term "limit stops," but my 205P (and the spares I've come across) didn't have them.

*headdesk*

I may take you up on that distributor option. Let me see how tomorrow goes based on the the below information.

Incidentally, today's perfectly crap running seem to be caused by a stuck AFM. Despite lubing it a week or so ago, it's sticky again. Pulled it out and hit with some PB Blaster. Will continue to soak it for the evening and see if I get something more reliable tomorrow.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
asiab3
IAC Addict!
Location: San Diego, CA
Contact:
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by asiab3 » Mon Feb 16, 2015 8:15 pm

Ronin10 wrote:Limit stops?! There were supposed to be limit stops in there? I did crack open a 009 I had from a salvage yard and saw two vertical things I would term "limit stops," but my 205P (and the spares I've come across) didn't have them.

*headdesk*
Maybe the 209P doesn't have the same style, but there has to be a way to limit mechanical advance, and the rev-limiting rotor doesn't count… :bom:
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Mon Feb 16, 2015 8:39 pm

Wait! Hold the fort. Fingers engaged before my mind did. I just ran out to the garage to do a quick check and realized, yes, the mechanical advance does have the limiting stops. Which I should tweak it seems.

Also, as an aside and in reference to my sticky AFM mentioned above. It seem the portion of the portion of the flap that goes into the damping chamber is scraping along the bottom of the channel and that's what's causing the sticking. I had thought it was the spindle portion needing lube but upon closer inspection, I could see the scoring marks barely visible.

Bugger.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Tue Feb 17, 2015 8:21 am

Swapped in an untuned, spare AFM (but seems to be set very rich) after posting last night as well as the ECU that came with my harness (77 CA model...full throttle enrichment is back!). Made a big, big difference on the test drive last night and again into work this morning. I'll do some tuning of the AFM this week and see if I can get decent A/F ratio numbers and go from there.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
asiab3
IAC Addict!
Location: San Diego, CA
Contact:
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by asiab3 » Tue Feb 17, 2015 9:12 am

Ronin10 wrote:Wait! Hold the fort. Fingers engaged before my mind did. I just ran out to the garage to do a quick check and realized, yes, the mechanical advance does have the limiting stops. Which I should tweak it seems.
How did you see the tabs without dismantling the distributor?

I do not know if the timing range is your issue, so I can not tell you to bend or not bend. I can tell you that over-bending one will break it, and you'll be in much bigger trouble than stumbling /bad idle. Perhaps get a core distributor and experiment with it; it took me several cores to compile a working 205Q for my old engine.

I would look into the "sticky" AFM first, since you know there's a problem there.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Tue Feb 17, 2015 10:16 am

I had guts from another 205P in a box. I starting pulling them out and then I saw the axial piece and it struck me..."Oh yeah! Those are the limiting stops."

It was yet another humbling moment.

The AFM is next on the docket. Expect to benchmark where I'm at tonight and maybe do a bit of tuning, but need to swap out my son's bug's steering box first.

I do have a good idle now while warm - a cold engine is another story - and one of the things I noted previously was that below 1400 or so RPM the mixture was very, very lean. First target is to see if I can even get a good idle mixture while warm and then look at adjusting the higher RPM from there. If I'm having too much trouble adjusting for idle, it'll likely indicate another issue and that's what I'm looking to clarify.
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Wed Feb 18, 2015 8:38 pm

Ronin10 wrote:I had guts from another 205P in a box. I starting pulling them out and then I saw the axial piece and it struck me..."Oh yeah! Those are the limiting stops."

It was yet another humbling moment.

The AFM is next on the docket. Expect to benchmark where I'm at tonight and maybe do a bit of tuning, but need to swap out my son's bug's steering box first.

I do have a good idle now while warm - a cold engine is another story - and one of the things I noted previously was that below 1400 or so RPM the mixture was very, very lean. First target is to see if I can even get a good idle mixture while warm and then look at adjusting the higher RPM from there. If I'm having too much trouble adjusting for idle, it'll likely indicate another issue and that's what I'm looking to clarify.
Performance camshaft, yes? Tune engine for best warm behavior. Time to upper end spec when warm.
Understand at all times that your cam overlap has taken needed idle air flow.
Now put your restless engineering mind to work to come up with a decent cold idle air supply. Ask Luftwagen about his Ford or whatever solenoid purge valve that he uses on his Vanagon for a good cold idle. You may need to come up with a means to actuate/deactuate.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
Ronin10
Getting Hooked!
Location: Columbia City, Seattle, WA
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Ronin10 » Thu Feb 19, 2015 10:44 pm

All points above duly noted, but let me add another bit of information/complication in here...

I haven't had an opportunity to do much more the throw my A/F ratio meter onto Greta and measure her existing setup. Here's what I found: greater than 20 AFR @ idle (fluctuates significantly), 13-14 @ 1000 RPM (fluctuates), 11.2 @ 1600, 11.0 @ 2000, 11.3 @ 2500, 11.6 @ 3000, 11.8 @ 3400, 11.4 @ 4000 RPM.

So with this in mind, I've got a pretty good handle on adjusting the AFM now. It's lean at idle and rich at high RPM...adjust wiper CCW to enrichen the whole fuel map and adjust the black cog CCW to lean out higher RPM, then correct idle with mixture screw, right? Unfortunately, I'm out of adjust on both the wiper arm and mixture screw...the wiper arm is at full rich and the mixture screw is turned all the way in to get to this setup.

Just toying with ideas here to get my mixture better at idle...is there a way to reset the position of the wiper arm on it's pivot axis?

Also, and I guess this is the likely scenario...I could just ignore idle as it is doing so nicely at the moment, and adjust the higher RPM leaner (along with my timing).
Oscar: 1976 Sage Green Bus, Stock Motor, Solid Lifters, Manual Transaxle

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Fri Feb 20, 2015 6:16 pm

Ronin10 wrote:All points above duly noted, but let me add another bit of information/complication in here...

I haven't had an opportunity to do much more the throw my A/F ratio meter onto Greta and measure her existing setup. Here's what I found: greater than 20 AFR @ idle (fluctuates significantly), 13-14 @ 1000 RPM (fluctuates), 11.2 @ 1600, 11.0 @ 2000, 11.3 @ 2500, 11.6 @ 3000, 11.8 @ 3400, 11.4 @ 4000 RPM.

So with this in mind, I've got a pretty good handle on adjusting the AFM now. It's lean at idle and rich at high RPM...adjust wiper CCW to enrichen the whole fuel map and adjust the black cog CCW to lean out higher RPM, then correct idle with mixture screw, right? Unfortunately, I'm out of adjust on both the wiper arm and mixture screw...the wiper arm is at full rich and the mixture screw is turned all the way in to get to this setup.

Just toying with ideas here to get my mixture better at idle...is there a way to reset the position of the wiper arm on it's pivot axis?

Also, and I guess this is the likely scenario...I could just ignore idle as it is doing so nicely at the moment, and adjust the higher RPM leaner (along with my timing).
I have to rewrite the AFM article. You have read elsewhere I hope, that we can set the wiper pretty specifically for 10.9-11.3 full throttle at 50 mph, should lean out to 11.5-11.7 full throttle at 65-70 mph.
You can't be all the way over to the rich side on that wiper adjustment AND have a bottomed out mixture screw. That is crazy compensated and would lead to horrendous fuel economy, do you have horrendous fuel economy?

Do you have a CHT gauge? Please note, I know you would love to bias all adjustments towards rescuing the idle, but that leaves everything else compromised. Your lean idle is because the engine is sucking exhaust at the beginning of the intake stroke from that considerable cam overlap instead of getting clean sucks (good vacuum) down the intake. The AFM just is not getting adequate airflow to signal a sufficient mixture.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
asiab3
IAC Addict!
Location: San Diego, CA
Contact:
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by asiab3 » Fri Feb 20, 2015 8:25 pm

Amskeptic wrote:The AFM just is not getting adequate airflow to signal a sufficient mixture.
Colin
What about a vacuum retard distributor to increase idle air flow?
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by Amskeptic » Sat Feb 21, 2015 9:56 am

asiab3 wrote:
Amskeptic wrote:The AFM just is not getting adequate airflow to signal a sufficient mixture.
Colin
What about a vacuum retard distributor to increase idle air flow?
That would not work in a performance camshaft application. Vacuum retard kills vacuum with a late spark, and we don't need to kill any more vacuum here. Vacuum retard also requires more idle air flow than we can get here.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
wcfvw69
Old School!
Status: Offline

Re: 2-for-1 and possibly related: Bucking and unstable/nonid

Post by wcfvw69 » Sat Feb 21, 2015 2:08 pm

asiab3 wrote:
Amskeptic wrote:The AFM just is not getting adequate airflow to signal a sufficient mixture.
Colin
What about a vacuum retard distributor to increase idle air flow?
Just thinking out loud here. With all the hours you have trying to tweak setting for that cam, why not pull the engine apart and replace it with a cam that matches your fuel injection system?
1970 Westfalia bus. Stock 1776 dual port type 1 engine. Restored German Solex 34-3. Restored 205Q distributor, restored to factory appearance engine.

Post Reply