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timvw7476
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Joined: June 03, 2013
Posts: 2206
Location: seattle
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 Posted: Thu Jul 17, 2014 3:08 pm Post subject: 10mpg with dual solexes...how is this even possible?! |
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With #1&2 being so "fluffy" it's the float or the needle & seat that feed them.
It obviously wasn't sticky caliper or clutch slippage, you would of smelled them by now.  |
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guitarman63mm
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Joined: September 03, 2008
Posts: 797
Location: Asheville, NC
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| Posted: Thu Jul 17, 2014 3:15 pm Post subject: |
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I should mention that I had trouble getting these carbs to idle in the Bentley's configuration - 2.5 screws out on the base mix screws, and (2.5?) on the CIS did not work whatsoever, and IIRC, it was super rich. I ended up setting the lower base mix screws to 1 screws out each, and that made it idle quite happily at ~700 rpm, but now I'm wondering if I need to lean out the CIS mix as well, and give it some air. The exhaust always has a light grey/white vapor/smoke when you rev it up from idle, which smells rich, like fuel vapor. Monkeying with the Bentley settings may have masked an underlying issue. Thoughts, BD?
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Jimmy
- 1974 Safaré Custom Camper. 091 trans + Dual Weber 34 ICTs + Pertronix SVDA + 1.7L 914 T4 engine. |
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12728
Location: on a bike ride somewhere
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| Posted: Thu Jul 17, 2014 3:36 pm Post subject: |
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| guitarman63mm wrote: |
| I ended up setting the lower base mix screws to 1 screws out each, and that made it idle quite happily at ~700 rpm |
Why 700? That's below factory spec, which was already low to satisfy emissions requirements. I go on the upper end of spec for a smoother transition off idle (drivability,) and better oil pressure at idle after pulling off a hot freeway run (engine longevity.)
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guitarman63mm
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Joined: September 03, 2008
Posts: 797
Location: Asheville, NC
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| Posted: Thu Jul 17, 2014 5:49 pm Post subject: |
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| asiab3 wrote: |
| guitarman63mm wrote: |
| I ended up setting the lower base mix screws to 1 screws out each, and that made it idle quite happily at ~700 rpm |
Why 700? That's below factory spec, which was already low to satisfy emissions requirements. I go on the upper end of spec for a smoother transition off idle (drivability,) and better oil pressure at idle after pulling off a hot freeway run (engine longevity.) |
I don't really remember why I set it that low. I remember a line from Colin's dual carb set-up info, "Your engine should run without too much complaint at about 6-800 rpm", but that was when setting the carburetor base mix screws - re-reading it now, I see that he suggests around 950-1000 rpm, per spec. I wonder if my engine is just pig-rich at idle on the right side...I'll go run through his instructions again tomorrow.
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Jimmy
- 1974 Safaré Custom Camper. 091 trans + Dual Weber 34 ICTs + Pertronix SVDA + 1.7L 914 T4 engine. |
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12728
Location: on a bike ride somewhere
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| Posted: Thu Jul 17, 2014 5:56 pm Post subject: |
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When Colin and I were messing with my (single carb) mixture screw, we got the AF mixture down to an O2 ratio/content of about 10.5 under accel to 12.8 cruise. (Super pig rich.) Then we adjusted the idle mixture screw to a 13.5 accel and 17 cruise. (Too lean to drive with, but ok just down the block for the test.) 14.7 is the chemically ideal mixture for energy production and waste reduction, but it is too hot/lean for our engines under load. It's a good mixture for idling, and you will see MUCH higher numbers under decel and low-throttle cruising.
So we know the idle mixture screws can play into mixture settings, but I don't know if it could really take your economy down THAT much.
And my 1600 will idle on four cylinders around 550-600 rpm warm, but I imagine the bearings are cringing.
Robbie
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guitarman63mm
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Joined: September 03, 2008
Posts: 797
Location: Asheville, NC
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| Posted: Fri Jul 18, 2014 8:50 am Post subject: |
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Welp, the plot thickens. I tried doing Colin's method of the finger on, finger off thing on the mixture reference line, and it seemed to always increase the idle when I took my finger off, no matter how much I closed down the base mix idle screws (this is with the CIS solenoid wire removed.) I also noticed that the left cut-off solenoid clicks when I connect the wire, but there's no drop in rpms when I remove it...everything is whacky with these carbs. 
I leaned out the base mix on the right side and upped the CIS's contribution, hoping it would make it all leaner, and set the idle to around 1000. I'll see how it drives...I'd really like to get my hands on a wideband though. I'll try to check the float level when I stop tomorrow night.
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Jimmy
- 1974 Safaré Custom Camper. 091 trans + Dual Weber 34 ICTs + Pertronix SVDA + 1.7L 914 T4 engine. |
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1967250s
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Joined: May 02, 2007
Posts: 2137
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| Posted: Fri Jul 18, 2014 10:09 am Post subject: |
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| BAck to the beginning- Right side plugs are too rich. Looks to me that the carbs are not balanced properly. Do you have the balance tube on? Disconnect the linkage and re-adjust. Left carb is probably not open enough, and right too much, that is why left side adjustments do nothing at idle. This would also help engine run much more smoothly and improve mileage, you'll definitely notice it. Clicking of solenoid is good. IS right one also clicking? Proper fuel pressure is only 2 or 3 psi. |
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guitarman63mm
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Joined: September 03, 2008
Posts: 797
Location: Asheville, NC
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| Posted: Fri Jul 18, 2014 4:19 pm Post subject: |
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Alrighty kids, something new has arisen: I think I have a bum solenoid. Both click, but I swapped solenoids from one side to the other, and one of them appears to be staying stuck open. I've determined this because with both the pilot cutoffs unplugged, the base mix screw on one side is still changing the engine's idle. The interesting thing about this is that when I screw in the right carburetor's mix all the way, the engine drops from 850 or so to a loping 450 and tries to die, but if I back it out to 0.5 turns out, it races up to 1100, but if I back it out another 0.5 turns (to 1 screw out), it returns to 900. Now, the pilot cutoff is only there to prevent run-on, but this is interesting, because I'm wondering if the base of the mixture screw is damaged, and that's what's causing all of these problems on the right side - ie: It meters correctly at 0.5 turns out, but at any more than that, the damaged portion of the hole leaks in more fuel than intended, causing a rich scenario. Thoughts?
Not sure what you're referring to with the balance tube. I believe it was only called the balance tube on '72, I assume you're talking about the central idling system, in which case, yes, I have it on. I have them both synced pretty well with a snail meter at high rpms, so I don't think the linkage or any of that is the problem.
Earlier today, I tried doing something somewhat like Colin's method - base mix screws 2.5 screws out, which put me somewhere like 550 or so when warm (any more and it died), with CIS picking up the rest of the slack to bring it to 1000, but this was ridiculously unstable. When I would come to a stop, the rpms would drop to a ridiculous, loping 450-500 rpm, then slowly recover up to 1000-1100 over the next 20 seconds . At 450 rpms, my brake booster no longer pulled vacuum, and could have caused a collision. I set it back to 1 screw out on the base screws, and for the CIS, 2 screws out on the mixture screw, 3.25 screws out on the speed/air screw. With 1 screw out and no CIS, it's at around 350rpms and about to die, so it seems like my setup is backwards to what the original intent was, that is, set each carburetor to be adjustable within some latitude at 600-800 rpms, and then use the CIS to pick up the slack, maybe 400 rpms max. I'm inclined to keep it this way, with the CIS providing almost all of the idle mix, because I can't get it to run any other way. I really suspect the bases are damaged from some monkey mechanic.
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Jimmy
- 1974 Safaré Custom Camper. 091 trans + Dual Weber 34 ICTs + Pertronix SVDA + 1.7L 914 T4 engine. |
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Wildthings
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Joined: March 13, 2005
Posts: 50353
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| Posted: Fri Jul 18, 2014 5:37 pm Post subject: |
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| It sounds to me like you may have a leak vacuum leak in your brake booster, as you shouldn't be loosing assist if you are keeping steady pressure on the pedal. Try removing the booster vacuum line from the manifold and plugging the nipple and see what effect that may have. |
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1967250s
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Joined: May 02, 2007
Posts: 2137
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| Posted: Sat Jul 19, 2014 12:54 am Post subject: |
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| It should run just on the CIS at idle. Are you using the CIS adjustment screws on top of the left carb? |
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TomWesty
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Joined: November 23, 2007
Posts: 3482
Location: Wyoming,USA
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| Posted: Sat Jul 19, 2014 7:33 am Post subject: |
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| Wildthings wrote: |
| It sounds to me like you may have a leak vacuum leak in your brake booster, as you shouldn't be loosing assist if you are keeping steady pressure on the pedal. Try removing the booster vacuum line from the manifold and plugging the nipple and see what effect that may have. |
Ditto
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guitarman63mm
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Joined: September 03, 2008
Posts: 797
Location: Asheville, NC
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| Posted: Thu Jul 24, 2014 5:05 pm Post subject: |
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I think the booster probably is leaky, because it isn't storing vacuum effectively, and exacerbates this 'pulsing' issue I have when braking hard (I'm going to overhaul the brake system entirely when I get back) but that must not have been the cause of my woes with idling.
I checked my timing, and it appears to have been at about 26.5˚ BTDC, possibly closer to 26.25, but now I'm splitting hairs. I had read that 27˚ was ideal for the 914 engine, presumably as I have a different cam than the bus, so I must have erred a bit on the retarded side. I bumped it up to 28˚, and mpg from Florida to South Carolina averaged 18, combined city/highway, averaging 50-55 mph.
I'm currently in Asheville, and it appears my mileage has dropped, but I'm not sure if I should advance it a bit more to 30˚. I suspect I should, because here's the weird thing: Going up a regular highway hill, at part throttle, in third, or fourth, I start to lose torque. So, I press it slightly more, but it continues to drop slowly, even with more air and fuel. Now, I think that trying to scale a hill at 40mph is rather unsafe with traffic at 65, and also, my head temps are dropping as I scale the hill, rather than rising, so, am I mistaken? We're talking about hitting a hill at 60mph at the bottom, head temps at 350, and getting to the top at 40 mph, and head temps at 335. Kind of odd to me.
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Jimmy
- 1974 Safaré Custom Camper. 091 trans + Dual Weber 34 ICTs + Pertronix SVDA + 1.7L 914 T4 engine. |
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Tom Powell
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Joined: December 01, 2005
Posts: 4855
Location: Kaneohe
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| Posted: Thu Jul 24, 2014 5:15 pm Post subject: |
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| guitarman63mm wrote: |
| ... Going up a regular highway hill, at part throttle, in third, or fourth, I start to lose torque. So, I press it slightly more, but it continues to drop slowly, even with more air and fuel. Now, I think that trying to scale a hill at 40mph is rather unsafe with traffic at 65, and also, my head temps are dropping as I scale the hill, rather than rising, so, am I mistaken? We're talking about hitting a hill at 60mph at the bottom, head temps at 350, and getting to the top at 40 mph, and head temps at 335. Kind of odd to me. |
Are you getting a richer mixture that cools the CHT?
Aloha
tp |
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guitarman63mm
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Joined: September 03, 2008
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Location: Asheville, NC
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| Posted: Thu Jul 24, 2014 5:54 pm Post subject: |
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| Tom Powell wrote: |
| guitarman63mm wrote: |
| ... Going up a regular highway hill, at part throttle, in third, or fourth, I start to lose torque. So, I press it slightly more, but it continues to drop slowly, even with more air and fuel. Now, I think that trying to scale a hill at 40mph is rather unsafe with traffic at 65, and also, my head temps are dropping as I scale the hill, rather than rising, so, am I mistaken? We're talking about hitting a hill at 60mph at the bottom, head temps at 350, and getting to the top at 40 mph, and head temps at 335. Kind of odd to me. |
Are you getting a richer mixture that cools the CHT?
Aloha
tp |
Presumably, but I thought that everyone was supposed to be able to advance up a hill until it stopped pulling at full throttle, not at part throttle. It feels like it wants more advance, but I don't want to push it unless it's kosher.
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Jimmy
- 1974 Safaré Custom Camper. 091 trans + Dual Weber 34 ICTs + Pertronix SVDA + 1.7L 914 T4 engine. |
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busdaddy
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Joined: February 12, 2004
Posts: 51156
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Thu Jul 24, 2014 6:08 pm Post subject: |
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| guitarman63mm wrote: |
| in third, or fourth, I start to lose torque. So, I press it slightly more, but it continues to drop slowly, even with more air and fuel. |
That's no suprise with an 091 and a 1700.
| guitarman63mm wrote: |
| also, my head temps are dropping as I scale the hill, rather than rising, so, am I mistaken? We're talking about hitting a hill at 60mph at the bottom, head temps at 350, and getting to the top at 40 mph, and head temps at 335. Kind of odd to me. |
The temps are likely dropping because of unburnt fuel when you are lugging it.
Try the next hill in 3rd gear as soon as it starts to lose power, 1700's make all thier power at higher revs than the 2000 that 091 was geared for. You may even notice an improvement in gas mileage.
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airschooled
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| Posted: Thu Jul 24, 2014 6:21 pm Post subject: |
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What is your vacuum advance timing coming in at when you consistently feather the throttle around 3k+ RPMs hoses on? T4s can take around 10*, maybe more. Doesn't mean it HAS to take that much, but if you're only getting a few degrees you might be wasting fuel. My fuel economy gained almost. 3mpg when I allowed more than 2* vacuum advance. I'm somewhere around 6-8*, but I don't want to push my T1 past factory advance limits.
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guitarman63mm
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Joined: September 03, 2008
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Location: Asheville, NC
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| Posted: Thu Jul 24, 2014 7:09 pm Post subject: |
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| busdaddy wrote: |
Try the next hill in 3rd gear as soon as it starts to lose power, 1700's make all thier power at higher revs than the 2000 that 091 was geared for. You may even notice an improvement in gas mileage. |
I am hitting it in 3rd. I can hardly hold a light incline at 4k in 3rd, so I've been blasting at hills in 4th and immediately switching to 3rd once I slowed to 50 or so. Sometimes I get a slightl 'bump' (not enough to be a lurch, or a hesitation) as I press down on the accelerator while in 3rd or 4th on a hill (haven't hit anything steep enough to slow me in 2nd), so I think it's rich and I can't think of anything else to do other than advance or re-jet (or slow down, which is cool by me, just not with the people riding my ass.) Another possibility would be that the 'bump' is timing scatter/points bounce, but I didn't notice any when timing it.
Redline on the stock 914 cam is 5500 IIRC, but I never push it past 4500. I think I may just start hitting hills at 2700 in 4th or 3rd, but never in between, because this seems to be the issue - the bus slows until it hits a torque value that it can hold, so if I'm shifting out of 4th early, it's going to slow to peak torque in 3rd, aka...around 40mph.
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Jimmy
- 1974 Safaré Custom Camper. 091 trans + Dual Weber 34 ICTs + Pertronix SVDA + 1.7L 914 T4 engine. |
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busdaddy
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Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Thu Jul 24, 2014 7:13 pm Post subject: |
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Hmmm....., what kind of air cleaners do you have?
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guitarman63mm
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Joined: September 03, 2008
Posts: 797
Location: Asheville, NC
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| Posted: Thu Jul 24, 2014 7:15 pm Post subject: |
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| asiab3 wrote: |
| What is your vacuum advance timing coming in at when you consistently feather the throttle around 3k+ RPMs hoses on? T4s can take around 10*, maybe more. Doesn't mean it HAS to take that much, but if you're only getting a few degrees you might be wasting fuel. My fuel economy gained almost. 3mpg when I allowed more than 2* vacuum advance. I'm somewhere around 6-8*, but I don't want to push my T1 past factory advance limits. |
I'll have to check tomorrow, it's dark at my campground. The distributor is a 205 series from the 914, because I reused the 914 cam, I wanted to keep an advance curve that was designed for it (I think this logic makes sense...) Pelican (a 914 parts dealer) has an article recommending timing a 914 with carbs at 27˚ mechanical, 34-36˚ total, so I presume that means that this vacuum can can pull 7 to 9 degrees of advance.
| busdaddy wrote: |
| Hmmm....., what kind of air cleaners do you have? |
Goofy K&N ones. I went with them because I found a flaw in Amazon's pricing/accounting for certain K&N stuff last year, and snatched these up for $9 a pop. I don't think they're causing restrictions, if that's where you're going, but it wouldn't hurt to do a quick on/off test on a tall hill.
http://www.amazon.com/gp/product/B00062YNN2/ref=wms_ohs_product?ie=UTF8&psc=1
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Jimmy
- 1974 Safaré Custom Camper. 091 trans + Dual Weber 34 ICTs + Pertronix SVDA + 1.7L 914 T4 engine. |
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udidwht
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Joined: March 06, 2005
Posts: 3779
Location: Seattle, WA./ HB, Ca./ Shizuoka, Japan
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| Posted: Thu Jul 24, 2014 7:29 pm Post subject: |
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Likely related to the mismatch between 1.7L and the 091 gearing. Stick a 3 rib 002 in there and take note.
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1972 Westy Hardtop/Type-4 2056cc
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Headflow Masters New AMC 42x36mm heads w/Porsche swivel adjusters
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73 Web Cam w/Web solids
Dual 40mm IDF Webers - LM-2 - 47.5 idles/125 mains/190 air corr./F11 tubes/28mm Vents - Float height 10.45mm/Drop 32mm
Bosch SVDA w/Pertronix module (7.5 initial 28 total @ 3400rpm)
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Pertronix Flamethrower 40K coil
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