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Marv [UK]
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 Posted: Wed May 27, 2009 12:32 am Post subject: Tuning shop AFR set up :shock: and advice needed |
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Well I finally managed to finally fit my VEMS AFR and CHT gauge in my bus and it's really purdy. No photo yet as every one i've taken so far has been really crap and blurred
Problems so far are that the CHT gauge isn't working properly as the wideband heater and pump circuits are causing interference (i think) and I need to shield the cable with some stainless overbraid which I haven't got around to yet.
Bus is running sweet as a nut but now I FINALLY know why my bus has some heat issues. The AFR readings I've gleaned so far are
Idles at 12.7
mid throttle cruising almost always bang on 14.7 
under load acceleration up hill leans out to about 15.1 (i blame this on vac advance 205 distributor)
no load cruising downhill richens up to near 12!
little load acceleration can be anywhere from 13.3 to 14.3
WOT is about 14
idle overrun from high revs barely reaches 14
When I stomp on it at low revs, the hesitation I am getting is caused by an AFR in very low 11's
Considering I took my carbs to a well known aircooled experienced tuning shop to get them dialed in perfectly as I didn't have the tools to do it myself, I am shocked that they dialled it in bang on stocih! Put it this way, it's one of those places that won't let you watch, and I certainly won't be going there again in the future.
Currently my timing is set at 29 - 30 degrees without vac advance and I think i'm going to bump that up to 32 to see what effect that has.
Then i'm going to step down my rockers to 1.1 from the current 1.25 and see what that does
I am aiming for a mileage motor as fuel is just too damn pricey at the moment at nearly £1 a litre ($1.50 a litre or nearly $6 a US Gallon!) and quite frankly, I am sure that I can get better fuel economy than I am getting at the minute. I currently get 25MPG from a UK gallon (4.54 litres where a US gallon is 3.8 litres) which equates to about 21 MPG US. It's not that bad when i was getting less from the 1600 that was in there.
Anyway
Spec is a 2017 with a C35 and dual DRLA 36's on slightly ported (homebrew dremel job) stock 040 heads and also with 215R14's on the back wheels (7% greater circumference than stock).
When I have finally dialed in my distributor, fuel pressure (after fuel pump problem recently) and valve lift down a bit i'm going to be going for lean cruising but what AFR's should I be aiming for?
Guess work at the moment is
WOT of less than 13
Cruising at about 16
idle at the richer side to prevent popping at overrun
DRLA's have 32 Venturi's
140 mains (guess i'll go up to 142's or 145's)
180 tall airs
60 Idles (i'll go down to 58's to start and richen up on the idle screws for overrun)
.2 emulsion tubes
40 pump jets but i'll go down to 33's to prevent severe over richening on stomp to WOT
What do you think? Am i barking up the wrong tree? |
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Slow 1200
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| Posted: Wed May 27, 2009 1:35 am Post subject: |
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are you 100% sure you don't have an exhaust or intake leaks?
oh, and I don't see any reason to change you rockers I would leave them alone, and save the time spent on doing your rocker geometry again in finding out what's wrong with your current tuning. |
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Marv [UK]
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| Posted: Wed May 27, 2009 2:41 am Post subject: |
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| Slow 1200 wrote: |
are you 100% sure you don't have an exhaust or intake leaks?
oh, and I don't see any reason to change you rockers I would leave them alone, and save the time spent on doing your rocker geometry again in finding out what's wrong with your current tuning. |
I'm about as sure as you can be with an EMPI exhaust and heat exchangers but there are some slight sooty marks at the heat exchanger donut clamps. Hardly anything when you consider the exhaust is many months old and rusty as feck. It is something I intend to redo again soon though. As far as the intake goes, i'm pretty sure  I've spent so much time with my head in the engine bay recently.........
The only reason I want to redo my rocker geomety is to reduce valve train stresses. A C35 with 1.25 ratio rockers is 0.466" lift but with 1.1's that reduces to 0.411". With the stock heads, i think that will be barely noticeable in power but might gain a mile or two per gallon. I have calculated that by reducing the lift by 0.055" I only have to alter the shims by 0.015" or 0.3mm which is next to nothing so I might not even bother. It depends on what shims I have lurking whether i do or not.
The bus makes more than enough power for me to have fun and still be able to lose a fair bit for driveability's sake. With a family in tow and with the bus being driven by other people occasionaly, an On / Off motor is not necessarily the right thing to have so detuning for economy has been a hard decision, but the right one. Besides, if it will make my gearbox last a couple of years longer then that can only be a good thing right?
I would rather have a problem free, economic motor that makes 95 to 100 at the flywheel than a problematic motor that makes 110 or more, besides, I only need 100, not 120 even though i might WANT 130
Anyway, we've made a family decision that I can build a 2276 so the bus needs to be a bit more sensible and be able to do 300 mile road trips at the drop of a hat and not cost a fortune  |
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[email protected]
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| Posted: Wed May 27, 2009 8:39 am Post subject: Re: Tuning shop AFR set up :shock: and advice needed |
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what oil you running?
Go down to 55 idles and up to 150 mains, that will be close given your current #s.
Your idle mixture is way too rich, need to redo that. You should be idling in the high 13s at sea level, mid 14s at elevation. But I do not use a wideband to dial in idle mixture FWIW, I do a lean drop. Make sure you see no gas in carb throats while it's running, except for the pump squirt. If you do there's a problem.
John
Aircooled.Net Inc.
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Marv [UK]
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| Posted: Tue Jun 02, 2009 1:03 am Post subject: Re: Tuning shop AFR set up :shock: and advice needed |
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| [email protected] wrote: |
what oil you running?
Go down to 55 idles and up to 150 mains, that will be close given your current #s.
Your idle mixture is way too rich, need to redo that. You should be idling in the high 13s at sea level, mid 14s at elevation. But I do not use a wideband to dial in idle mixture FWIW, I do a lean drop. Make sure you see no gas in carb throats while it's running, except for the pump squirt. If you do there's a problem.
John
Aircooled.Net Inc. |
Currently running 15W40 which gives me good pressure with a pressure relief cover plate. 10W30 is going to be my next port of call to see what difference it makes to my motor
The idle mixture gave me a real shock when I first turned it over with the AFR switched on so this week i'm going to get in the back there and do some fettling. The really crappy thing is is that when I had my Dells rebuilt they were rebuilt and bench set on 55's but the tuning shop swapped them for 60's. Thankfully, I kept them though
I think the biggest set of jets I have to hand are 145's (except the 175's which would be pointless) so I'm going to jam them in too, see what happens.
Hopefully this will lean out cruising to a decent ratio at mid throttle but give me a good 13 ish stomp on WOT. The only thing I'm concerned about is super lean overrun |
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[email protected]
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| Posted: Tue Jun 02, 2009 9:53 am Post subject: Re: Tuning shop AFR set up :shock: and advice needed |
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the biggest tuning mistake is when peeps tune the idle/progression circuit for max power/response. This circuit should be LEAN (like 14:1 idle, and 17-18:1 progression) for cool running and MPG.
And don't run plug gaps over .030" IMO, just causes problems with no real benefit. YMMV.
New engines can even run 0-20 oil, it runs VERY cool with this viscosity, and the MPG is fantastic.
John
Aircooled.Net Inc.
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Marv [UK]
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| Posted: Tue Aug 11, 2009 2:53 pm Post subject: |
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Groovy 
story so far..... engine out, 1.1 rockers on, stock original pushrods in
Fuel pump set at 3 PSI at idle
CHT gauge working
Turned out I had 4 No 58 idles and 3 No. 55's. I've only gone and lost one  then i've got 52's which are only worth putting in bugs with small engines.
58 idles in, 142 mains in (biggest I have as I lent my 145's to someone I've since fallen out with.. )
I have NOT done a lean drop idle tuning yet as I wanted to see what was going on and what Issues I have when it gets warm
It appears I have an exhaust leak is what I have 
idle currently at 13.2 - 14
progression at around 15
WOT at 12.9
for concerted driving CHT up around 400 - 450*F which is too hot but it's really surprising how quickly it changes. the motor can lose 100*F in 20 seconds when you take your foot off it. Peaked at 490 going up hill with my foot down!!!!
Problem with idling too, seems to not want to drop. Starts and runs great at about 900 revs until it gets warm when it struggles to dip below 1500 sometimes. Even had idling at 2000 revs.
Things to do
Return spring for carbs if required. Can't hurt anyway, just a gentle one
Exhaust. Find feckn leak. Popping like mad at the minute
Timing. - 034 SVDA with the vac off. Will set it to 28 at max advance
disconnect linkage and check synch with vac gauges and manometer ports
set hot idle to 850 revs
perform lean drop idle setting and add 1/8'ths to get it right side of 14.5 AFR if necessary
I'll then go for a spin and see what happens then
Sampling rate for my VEMS is about 3 or 4 times per second, don't know how quickly others react but this seems very fast. |
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[email protected]
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| Posted: Tue Aug 11, 2009 10:39 pm Post subject: |
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go down on the idles! We finished tuning an engine here with 36 DRLAs, we wound up with 45 idles @ 4200', which is ~50s at sea level. Richer than this and you are running hot and pissing gas out the tailpipe, losing MPG.
AVOID driving at Stoic. Tune the carbs so you can't operate there.
John
Aircooled.Net Inc.
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krusher
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| Posted: Wed Aug 12, 2009 12:47 am Post subject: |
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Dam that is hot, I have to lug the crap out of my bus up a steep hill to see 400 and cant get it much hotter then that if I try. Cruise at 60 at 320ish. 25/30mpg on US gas.
I hate those dam exhaust doughnuts, if I put a exhaust on a vehicle at work I always put a bit of sealant in the gap and then put the doughtnut against it.
Better still weld on flanges there.
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Marv [UK]
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| Posted: Wed Aug 12, 2009 1:34 am Post subject: |
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| krusher wrote: |
Dam that is hot, I have to lug the crap out of my bus up a steep hill to see 400 and cant get it much hotter then that if I try. Cruise at 60 at 320ish. 25/30mpg on US gas.
I hate those dam exhaust doughnuts, if I put a exhaust on a vehicle at work I always put a bit of sealant in the gap and then put the doughtnut against it.
Better still weld on flanges there. |
It is hot, worryingly so, but then I haven't verified the temp with an infrared thermometer yet. Still, It is too hot.
Cruise at 60 sees me at about 350 - 380 but then when I've got it tuned properly, It should sort out the heat issue. At least my oil stays cool with the original fanshroud and hoover bit now. Perhaps the 215 R 14 tyres don't help much 
Going to go the halfords tonight and get me some RTV to seal the doughnuts on there properly. It doesn't help that it's rusty as all hell though. |
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krusher
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| Posted: Wed Aug 12, 2009 7:36 am Post subject: |
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The place you took it to have it jetted should have spotted the exhaust leak and then not done the tuning till that what fixed.
I doubt your sdva will be adding to the problem as when you go to high load there is little vacuum and there so you just get the mech advance.
The extra vac advance will help advance the spark in light load situations where the lean mix needs to be ignited earlier does to it being harder to burn, you seem to have decent temps in those driving conditions.
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Marv [UK]
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| Posted: Wed Aug 12, 2009 10:15 am Post subject: |
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| krusher wrote: |
The place you took it to have it jetted should have spotted the exhaust leak and then not done the tuning till that what fixed.
I doubt your sdva will be adding to the problem as when you go to high load there is little vacuum and there so you just get the mech advance.
The extra vac advance will help advance the spark in light load situations where the lean mix needs to be ignited earlier does to it being harder to burn, you seem to have decent temps in those driving conditions. |
the exhaust leak comes from me dropping the engine in the last week |
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Marv [UK]
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| Posted: Thu Aug 13, 2009 12:54 pm Post subject: |
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Update:
Still need Johns quality advice though
exhaust leak fixed....
55 Idles installed (still on 142 mains but had delivery today, 145's and 148's, just haven't fitted them yet.)
synchronised the carbs with vacuum synchroniser, both front barrels (#2 and #4) synched at 10 inches of vacuum.
left hand carb idle screw showing about 3 or 4 threads, but the right one shows about 8 
Performed lean drop idle setting. #1 out 2 3/4 turns as are #2 and #3. #4 out 4 1/4 turns but I knew about this discrepancy when the carbs were rebuilt.
AFR's now as follows....
running at average of 14.2 at idle (750 - 800 revs) about 13.8 at cold start
normal cruising on flat land, constant 2000 revs - 15.2
3000 revs, again low 15's
3300 revs 15 dead on
cruising down a slight grade but foot still on it, goes up to low 16's
cruising up a slight grade, high 14's
foot flat on it, about 13.2, sometimes less
overrun at speed.... up to 20 without the vac can, 18.8 ish with it (the difference between a backfire and smooth running!)
low pressure acceleration AFR of 15.2 goes up to about 16.5.... I guess i need to adjust the accelerator pump nut.... In or out, can't remember off hand?
I know I need bigger mains... i'll go straight to the 148's (biggest i've got) and I know I need to adjust the accelerator pump a smidge, but what do you suggest I do about the low 15's cruising
head temps are 300 - 320*F at idle
up to and just over 450*F at worst
Oil temp gets to stat temp then no more so thats OK |
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[email protected]
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| Posted: Thu Aug 13, 2009 1:18 pm Post subject: |
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36DRLAs, try 50 idles to start. The only way to know is to try them. Maybe you'll wind up with 52.5s. Try 50s first.
John
Aircooled.Net Inc.
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Marv [UK]
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| Posted: Thu Aug 13, 2009 2:51 pm Post subject: |
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| [email protected] wrote: |
36DRLAs, try 50 idles to start. The only way to know is to try them. Maybe you'll wind up with 52.5s. Try 50s first.
John
Aircooled.Net Inc. |
I've got 53's and 52.s but can't remember if I've got 50's or not. Going to go straight to the 52's then
I seem to have difficulty with the lean drop though. Empi Phatboy exhaust and bad hearing (I work on construction sites, they're noisy)
Hey ho, I'll give it another go tomorrow Must remember to bring some blutack home to aid in getting the feckn idle jet holders out again....
Somebody in the VW scene really HAS to make some LOOOONG idle jet holders, It'd make life so much easier. I was feckn about with a mirror and pliers for ages today, would have been quicker to take the linkage and top plates off
Now theres an idea for a quality part |
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74 Thing
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| Posted: Thu Aug 13, 2009 5:42 pm Post subject: |
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They already make them-jet doctor from CB
http://cbperformance.com/catalog.asp?ProductID=514
You plug the original idle air holes with the lead plugs in the kit then the air is introduced through an extented idle jet holder like the air stacks for the mains. |
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Marv [UK]
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| Posted: Fri Aug 14, 2009 9:58 am Post subject: |
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OK, so another update
52 idles are in.... can't get lean drop idle right, I'm having a bad day... 4 1/2 turns out on 1 through 3, but 6 out on #4 and seemingly no effect... not sure how many threads are left!
I'm going to have to learn to do lean drop idle on my bank of 4 vac gauges Anyone done this before? Know of a link or something to what I should be seeing on the gauges?
Anyway, idle at about 13.8 to 14.5, some stumbling and occasional 15.. It's not set right at all, I just can't hear it on this small a jet and lean running
low acceleration, about 16 give or take,
adjusted the accels to 1 turn in which solved the lean accel prob
still runs at 14.X to 15.2 while i'm maintaining speed up a hill
mains now at 148, down to about 11.8 when I'm on the gas
running at speed with foot off the gas, it rises to around 19 and pops like mad. I'm adling at 750 though, so maybe I ought to crank up the idle screw and just uncover the vacuum port a bit more, maybe I've half mooned it.
Still gets over 400*F on a couple of miles uphill
typical though, I hunt around for an hour looking for my 50's... no idea where they've got to. Damn, In go the 52's.
Spend a couple of hours fannying about, go to clear up some stuff ready for going camping this weekend, and the 50's fall on my foot!!! It's just one of those days  |
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Marv [UK]
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| Posted: Fri Aug 14, 2009 1:19 pm Post subject: |
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Proper update this time, been for a 70 mile drive on the motorway...
52 idles are looking ok... It idles at 13.9 +/- 0.1
750 revs but a bit of an uneveness in there...
1000 revs and increasing on the pedal gets about 16 - 17 AFR
2000 revs gives me late 15's early 16's
2500 - 3000 revs is late 15's
holding constant 3500 to 4000 revs on flatish roads gets me slap bang in stoich again. WOT is 11.9
Damn, I wish I'd only changed the idles, not the mains too...
So, what next?
I'm going to go back down to 140 mains and see if I can hold at 4000 at 16 AFR or more as thats where I do most of my motorway cruising.
I'm going to leave the 52's in there for now
I'm kinda hearing a little pinging in there when I hold a hose above the velocity stack.... hopefully thats just the valve closing
timing on the 034 is set at 30 ish at max advance... comes in at 2*BTDC at idle which is far too early in my mind.... it's a mexi bosch I'm packing my fake 019 (Bosch cast iron VJU 4 BR8) so I was thinking of plumbing that in at 7.5 BTDC at idle and seeing where that gets me. OK, no vac can attachment and re springing yet, but that will come with time
OK, so.... How do you lean drop tune for idle mixture with 4 vac gauges???? It's too damn noisy in my engine compartment with that damn EMPI phatboy |
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[email protected]
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| Posted: Fri Aug 14, 2009 1:30 pm Post subject: |
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1/2 your problem is your timing is set completely wrong. It should be around 8 BTDC at idle, 28-30 full advance hose off. If #s deviate from this the distributor has something wrong with it.
John
Aircooled.Net Inc.
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It's just advice, do whatever you want with it!
Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net
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Marv [UK]
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| Posted: Fri Aug 14, 2009 1:36 pm Post subject: |
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| [email protected] wrote: |
1/2 your problem is your timing is set completely wrong. It should be around 8 BTDC at idle, 28-30 full advance hose off. If #s deviate from this the distributor has something wrong with it.
John
Aircooled.Net Inc. |
Yeah, I guessed something like that, It's this damn mexi 034.... It was fine when I put it on a couple of years back, but it just keeps on giving - advance that is - it's right at 28 mechanical advance, but when I bought it, it was 24.... something must be worn out in there
I've got a real 009 stashed in the back of the van.... might give that a go instead.... or the 019ish..... hmmm decisions.....
I'll try the BR8 first I think |
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