| Author |
Message |
JRV (Jrvall)
Member
Username: Jrvall
Post Number: 419
Registered: 11-2002
| | Posted on Monday, December 23, 2002 - 7:09 am: | |
Dr. Mike, I really like your explanations of all the steps. Please keep going as your time permits.
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Dr. Mike Adams (Drmike)
New member
Username: Drmike
Post Number: 16
Registered: 5-2002
| | Posted on Sunday, December 22, 2002 - 6:33 pm: | |
JRV,
I'll try to put "Dr. Mike's overly anal webber carb setup procedure" down on paper/post it. By now it might be becoming appearant that I am not a medical doctor. I am actually a Ph.D. in applied math w/ a M.S. in mechanical engineering. I have been a engineer in the fields of automotive and aircraft instrumentation ( engine sensors and control systems )for about 20 years. As such, my procedure is based on the sequential elimination of dependant variables. That is, analyze what adjustment cause changes in other adjustments, and perform the procedure in an order that does not undo/invalidate your previous work. A good example is in your procedure.
Adjust the timing 1st. The timing affects the vacuum level. The idle/progression circuit is controled by manifold vacuum (hydrostatic), as opposed to the main circuit which is based on air velocity (hydrodynamic). Change the timing, and you screw up the idle circuit settings...
There are many inter-dependancies within the carb system itself.
My pet peeve is that almost NOBODY pays any attention to the closed-throttleplate position. This setting is critical to off-idle mixture. The plates must JUST cover the 1st progression hole. if not, one of 2 bad things happen.
1. If the plate is too far closed, there will be a lean spot just off idle, before the 1st hole is uncovered. Soo... people will open up the idle mixture screw to cover it up. Result... overly rich idle.
2. If the plate is too far open, then some fuel from the 1st progression hole will be added to the mixture from the idle screw. So, to get a proper mixture at idle, you need to screw in the mixture screws to compensate for the fuel from the progresion hole. But NOW... the whole idle/progression circuit is lean once you open up the throttle. So... you have to re-open the mixture screws to an over-rich idle to make everything "line up". Result... overly rich idle.
My procedure actually involves removing the carbs and visually setting the throttle stops to make sure that the the plate-progression hole orientation is optimal. Then I shake a large stick at anyone who would touch the throttle screws. I set the idle speed with the air balance adjusters. Moving the air balance adjusters affects only the idle mixture and idle speed. The throttle plates affect the idle mixture, idle spees AND the progression mixture.
There is a way to get close without removing the carbs, using a colortune. But it takes a bit of experimentation.
1. open up the air balance adjuster a couple turns. to avoid excess vacuum with the plates closed.
2. completely close the idle mix screw.
3. start engine.
4. adjust the throttle screw to slowly open
5. watch for intermitent blue combustion. this fuel is comming from the 1st progression hole.
6. start closing the throttle until you get no more blue flashes.
7. re-adjust the mixture screw for proper blue/yellow color.
If you do this on all cylinders, the throttle plates will all be in (more or less) the same position. You can then adjust them ALL by 1/8 turns as needed to even out the progression curve.
I'll try to get some time to write down the whole procedure. |
Matt Lemus (Mlemus)
Intermediate Member
Username: Mlemus
Post Number: 1097
Registered: 8-2002
| | Posted on Sunday, December 22, 2002 - 4:58 pm: | |
Peter,
Thanks,
JRV,
For the idle adjustment, do you use the tach on the dash or do you use another kind/one? I don't really trust my dash tach that much. I assume it is off by +-200 rpm. It seems to run smoother at a posted rpm of 1150. I am assuming that this is actually 1000 without verifying the actual speed. Also, would you do this with the air pump connected on a two valve 308?
Matt
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JRV (Jrvall)
Member
Username: Jrvall
Post Number: 417
Registered: 11-2002
| | Posted on Sunday, December 22, 2002 - 4:53 pm: | |
I'll go ahead and stick my neck out and post the General Steps I use, feel free to add, correct or flame these procedures.
Developing a Baseline for Carb Tuning.
1) Warm up engine, shut down, check compression, replace plugs
2) Check points, set dwell (clean, reset, replace)
3) Check Timing & Distrib Curve Accuracy.
4) Remove Air Cleaner, insuring nothing falls into throats, (install adapter pipe for fuel return line),
thoroughly inspect for fuel leaks, check choke cable adjustment and operation
(including linkage & adjustments on carbs), check entire length of carb linkage for
inaccuracies or link binding, with quality flashlight inspect all carb throttle adj. screws for regularity.
5) Start engine and warm moderately, noticing running speed & condition, insure idle is 900-1000.
6) check air flow at each throat and mentally note, shut down, loosen all linkage jam nuts (with exception of rear carb),
7) Insure all carb throttle stops are touching on their respective set screw, insure choke stops allow throttles to assume full rest,
start engine again and recheck air flow, if necessary raise or lower to match while insuring idle speed remains at approx. 1000rpms.
once completed shut down engine.
8) Once all above steps checked and completed remove 1st plug and replace with 'Colortune Tool,' restart, turn mixture screw all the way in,
slowly unscrew until light (color) appears, continue backing out mixture screw until orange color appears, turn slowly in until 'Bunson Blue' color obtained (as noted earlier the high end of the blue scale seems to work out the best),
shut down and proceed to next cylinder.....repeat steps on all cylinders.
9) Idle may have raised at this point, recheck air intake volume again, reset as necessary for match and correct idle speed (850-900 rpms),
shut engine down, gently tighten jam nuts, insuring not to move throttles off their stops, tighten front linkage with return spring attached, .
10) With engine off fully depress throttle to insure free operation, restart engine and test engine acceleration and return to idle.
11) If engine accelerates and returns to idle properly, let idle, check all intake air volumes once more to insure no discrepancies, and color tune second time to insure constant firing by slightly turning mixture screw in & out while carefully scrutinizing color to insure best operation.
*The above takes into account that the carbs and other systems are in otherwise good operable condition and merely need adjusting.
*In the case of any cylinder or carb that doesn't have a nice stable range of adjustment the cleaning & adjusting of the internal components will be necessary.
*In the case of Carbs that fail to adjust properly, a host of problems can exist. If it's determined a carb cleaning/rebuild is in order, while the carbs are off
it is recommended that all intake Manifold O-rings are replaced, carb bases checked for flatness using a straightedge, all warped/deformed bases flattened by machining, carb bodies thoroughly cleaned and dried, all jets inspected, sized and noted, base gaskets replaced, needles & seats replaced, accelerator pump diaprams replaced, float levels carefully and accurately set, internal carb check balls checked for sticking, carbs reinstalled
and above Procedures repeated.
* When using a colortune it is best to try and check and adjust individual cylinders as quickly as possible, due to the lenght of time it takes to insure accuracy it might be neccesary to allow the engine to cool down occasionaly. However, haste makes waste and a methodical approach addressing anomolies as they are uncovered is a sound approach.
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'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 2285
Registered: 12-2000
| | Posted on Sunday, December 22, 2002 - 1:42 pm: | |
Matt, you can get them direct from Colourtune. Here's their PDF catalogue:
http://www.gunson.co.uk/pricelists/Gunson%20Price%20List%202002.PDF
And their online catalogue:
http://www.gunson.co.uk/acatalog/Gunson_Catalogue_Exhaust_Gas_Analysers_Mixture_Control_5.html
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Matt Lemus (Mlemus)
Intermediate Member
Username: Mlemus
Post Number: 1096
Registered: 8-2002
| | Posted on Sunday, December 22, 2002 - 10:06 am: | |
JRV,
would this work on a 8 cylinder carb car? I have been having difficulty tuning the carbs. They are running a little rich as well. I am intrested in learning how to dial in the carbs.
All,
Where can color tune plugs be found? This is new ground for me.
Matt |
JRV (Jrvall)
Member
Username: Jrvall
Post Number: 415
Registered: 11-2002
| | Posted on Sunday, December 22, 2002 - 9:53 am: | |
>>>Also... I do not belive that optimal results are likely if you use the procedure in the workshop manual to set up your carbs. <<
I completely concur. (caveat-please do not develop your own procedure until you have gathered a complete understanding of tuning from a-z)
>>They are great tools. But they are lousy sparkplugs. <<
Completely concur again.
>>I use 3 colortunes at a time ( on a 6 carb V12 ). <<
Sometimes I use 2, however, generally I just use 1 tuning, unless chasing an unknown or bigger problem. My standard procedure consists of going thru the mixture drill 2-3 times (have done it more).
>>You can use the colortune to equalize the mixture between all of the cylinders, which is good. But, you may end up going rich again to cover up a lean/flat spot in the curve. <<
Completely concur once again. However, my feelings are that until one goes thru the tune & tweek drill, idle speed, balance, mixture, using the tools (colortune) getting the feel which is as good a place as any for a DIYer to start there is no way of knowing what other issues may be hiding here and there and everywhere.
DrMike, I'm impressed. You're the first (only) person I've had the pleasure of talking to that understood the full nature tuning a 6 carb set-up. Incuding the challenge of trying to go back in time to a period where all the parts were new and settings were relatively un-cobbled.. I concur completely about drawing a baseline. Although to draw a baseline one needs quite a large assortment of tools, data and understanding of engines as an overall system (compression, timing, settings, jet sizes, etc.) .
This is a very difficult area to broach from a 'make it not run to rich I'm a DIY'er with a little free time on my hands'. Goes back to my other thoughts on 'expectations'. I think it's possible for Dr.I to get his Daytona running leaner and smoother (which was his request) with the online help of the guys here. Get it 'really completely right'?, well, kinda doubtful knowing how time takes it's toll on soooooo many different things.
Dr.M, I can tell you've been down the same road I have in the quest. To start on an old, questional set-up and bring them current & right can easily take a week as I'm sure you know. Would you mind writing the drill start to finish (I'm not a writer & I type with 1 finger...lol)? or I can, with you filling in any blanks I might miss, but it will take me some time. I understand the trepidation one can have to just lay it all out.... |
Dr. Mike Adams (Drmike)
New member
Username: Drmike
Post Number: 15
Registered: 5-2002
| | Posted on Sunday, December 22, 2002 - 4:45 am: | |
I use 3 colortunes at a time ( on a 6 carb V12 ). Any more than that seems to affect the idle speed. They are great tools. But they are lousy sparkplugs. I do NOT trust them to drive around on. I have seem tiny cracks in the crystals just from running the engines up to the point where the mains kick in ( probably from a few overly lean runs ).
Like JRV said. it is not as simple as "watch the color, turn the screw". Even though that is how it is advertized. Accoring to me, even the instructions that come with the colortune are wrong.
Dr. I, I am probably way to anal about setting up the carbs. If your Daytona is running "a little rich", and someone had to tell you that ( i.e. you are not feeling a performance problem ), you may want to leave it be. The slight over rich mixture at idle may be covering up any of a dozen other adjustment issues that cause a lean spot in your fuel curve. All of which are worse than a slightly wet idle.
You can use the colortune to equalize the mixture between all of the cylinders, which is good. But, you may end up going rich again to cover up a lean/flat spot in the curve.
On the other hand. You may want to bite the bullet and "baseline" your carbs. All the tuning in the world is mostly just guesswork, if you don't really know where you are starting from.
Also... I do not belive that optimal results are likely if you use the procedure in the workshop manual to set up your carbs.
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lou staller (Lou_staller)
New member
Username: Lou_staller
Post Number: 1
Registered: 12-2002
| | Posted on Saturday, December 21, 2002 - 11:39 pm: | |
TEST |
James Selevan (Jselevan)
Member
Username: Jselevan
Post Number: 280
Registered: 6-2002
| | Posted on Saturday, December 21, 2002 - 11:08 pm: | |
JRV - do you (can one) use more than one colortune at once? While not inexpensive to own 6, it might make it easier to finish one bank at a time, rather than changing the spark plug 6 times. Is there a limit to time / heat that the colortune can tolerate?
Jim S. |
JRV (Jrvall)
Member
Username: Jrvall
Post Number: 414
Registered: 11-2002
| | Posted on Saturday, December 21, 2002 - 10:48 pm: | |
BTW James, I'm not trying to suggest a colortune is an end all, be all, do all...it's simply one of the many tools I use tryin to make a livin.
I still remember the sign hanging in my High School Coachs office...
" Practice Doesn't Make Perfect, Perfect Practice Makes Perfect" ...it can be interpreted as subjectivly as colortune readings, however once that light goes off and we finally get it, the sailing is much smoother.
If anyone cares to we can mull over why the colortune seems to work for some and not others. I have a feeling the differences between the two camps might lie with perceptions , procedures or expectations.
Anyway...Happy Holidays and Dr. I good luck.
JRV |
JRV (Jrvall)
Member
Username: Jrvall
Post Number: 413
Registered: 11-2002
| | Posted on Saturday, December 21, 2002 - 8:51 pm: | |
Hi James, I can only speak for myself, Colortunes work for me and have for more than 20 years and on far more than Daytona carbs. And like Dr. Mike, it's one of the few British things I would ever own more than one of. I can't even begin to remember all the things I've used them for. And sure you have to walk over and turn the lights up and down, and sure ya have to start & stop, and sure lots of other things, but it's a Ferrari...and it all just goes with the territory imo and if you want to learn and tinker then it can be fun. One of the first things that stuck in my perception of reality after making the shift from working on Porsches daily to working on Ferraris daily was how unafraid of work the Italians obviously were, because doing almost everything right on Ferraris was more 'work' than the average equal Porsche job. Heck, just taking the air cleaner off and getting ready to start takes a half hour. Set the timing on a 911, then a Daytona, lol. So personally, after I committed to Ferraris I got over the fear of work and carried on. Can't tell ya how many times I've told myself, nobody promised me a rose garden.
Anyway, I'm not one of the guys that thinks Ferrari, Easy and Cheap go together. But speaking of cheap....at $49.95 a colortune is as cheap as tool gadgets get. But the old saying goes, if you want it to work, you have to work it. And in all honesty colortunes like most everything else require practice to become proficient.
Also read what Dr.Mike mentions, to get good results there is a whole litany of things that need to be checked and speced and dialed in. But Dr. I just wants to tweak a little, learn a little, and try to get his Motor running better.
So really I was trying to avoid giving a course in Dr IMI's best interest, as he is new at this, and imo it's easier to slowly move up on such a complicated job and point him towards some helpful aids rather than just pointing to the screws to start turning. .
One of the things I try to envision when trying to get a guy started on something new is what stumbling blocks they might encounter and add a few tips that 'might help' them. As I view this situation one needs the car to give him a considerable amount of information so that decisions can be made and directions determined. And what better way of deriving information from a car than tools.
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James Selevan (Jselevan)
Member
Username: Jselevan
Post Number: 279
Registered: 6-2002
| | Posted on Saturday, December 21, 2002 - 7:54 pm: | |
JRV - I have used colortune plugs in the past, along with William's excellent approach of closely optimizing idle speed by adjusting each carb individually. However, I only had one colortune, thus, I had to remove the sparkplug after each adjustment and insert the colortune. I found it a pain, and, for those of us with eyes entering their 6th decade usually requiring bright shop lights, I had to turn down the lights to observe the color of the flame-front. Furthermore, I found a fair amount of discrepancy between what the colortune was suggesting and the idle speed monitoring. All in all, careful monitoring of idle speed seemed to accomplish a better job in less time.
My experience.
Jim S. |
Dr. Mike Adams (Drmike)
New member
Username: Drmike
Post Number: 14
Registered: 5-2002
| | Posted on Saturday, December 21, 2002 - 4:57 pm: | |
Gotta agree with JRV on the colortune. Best thing to come out of Britain since the RR Merlin engine. It almost makes up for British wine.
I find that if you set the idle mixture right at the edge of the blue/yellow transition, the off idle performance is at it's best.
Assuming that everything else ( float level, jets, throttle stop postitions, linkage synchronozation, etc ) is right.
With the colortune and the air meter ( I like the redline style with the kg/H display ), you can actually watch the whole idle/progression circuit work up to where the mains just begin to come in. This lets you know whether to adjust the idle mix, the float level, or the idle jet size. It can even identify idle jets that have been reamed out by some genius, and not marked ( ask me how I know ).
I make carb adapters with pourable rubber from Devcon. The flexane-80 kit seens to work well for this. Also good for casting other small rubber replacement parts like bumperettes, etc.
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JRV (Jrvall)
Member
Username: Jrvall
Post Number: 412
Registered: 11-2002
| | Posted on Saturday, December 21, 2002 - 2:45 pm: | |
Dr.., Bill is right, you'll need to fabricate the adapter. Mine is made from Hobby Store supplies, thin tin or brass, cut with scissors, formed to shape, thin double sided foam tape on the carb end to seal against the carb top opening, round tube piece glued on top to mate to the unisyn bottom. I think I used a styrofoam cup cut out one time when I was on the road and away from my special tools.
The reason I asked about the tools is they make it alot easier. But you can still improve and practice tuning with some old timer tricks, to determine air flow use a piece of 3/8"-1/2" hose a couple feet long approx 3' to listen to the sound made inside each carb port, one end a half inch or so inside the carb top, the other end of hose to your ear, like a stetescope, and listen to the engines heartbeat...practice matching all the heart beats...and listen carefully to the exhaust sound with the other ear and note rpm improvement or deterieration. I guess that's why it's called tuning by ear. ;-)...slowly work in order catching improvement on each cylnder as you go.
On the cylnder end...the 'Gunsons Colortune' can really make mixture adjustment and problem solving/finding a lot easier, because it lets you see inside the engine and view what is happening...you can actually see a problem, ie: too rich (orange), to lean (white), a miss (black with no spark), a spark jumping but no gas(clogged ide jet) etc...so it can be real helpful and a fun learning experience. I found a place that sells some of Gunsons Products for you and a few links discussing carb tuning. The tools can really make a bear of a job alot easier but the carbs can probably be improved upon by carefull, methodical adjusting by ear and following the work shop manuels instructions. Here's the links enjoy and Happy Holidays.
http://www.aep.bigstep.com/index.html
http://discussionarchive.imzural.info/volume1/discuss/msgReader$2102?mode=topic
http://www.audifans.com/archives/1996/04/msg00618.html
http://www.viragoownersclub.org/p_8.htm
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William Badurski (Billb)
Junior Member
Username: Billb
Post Number: 119
Registered: 6-2001
| | Posted on Saturday, December 21, 2002 - 2:16 pm: | |
I fabricated an adapter using a short piece of 2" exhaust pipe. Cut a gasket from a piece of gasket paper to fit the square choke housing atop the carb, and glue it to one end of the pipe. You won't need a seal on the opposite end as the Uni-Syn has a gasket attached to its' base. Works fine, and cheap to make. |
Dr. I. M. Ibrahim (Coachi)
Junior Member
Username: Coachi
Post Number: 162
Registered: 5-2002
| | Posted on Saturday, December 21, 2002 - 12:48 pm: | |
JRV...i have a unisyn tool from the days when i used to own XKE's with threee SU's that needed to be synchronized all the time. I do not have an adapter, so if you can direct me in the right direction to purchase one. No color tune spark plugs either...I will try to follow Bill's directions...hope I don't mess this thing up too much.. thanks for the tips guys |
Greg Rodgers (Joechristmas)
Member
Username: Joechristmas
Post Number: 544
Registered: 3-2001
| | Posted on Saturday, December 21, 2002 - 10:49 am: | |
I use a Synchrometer that it very nice. It has a metered measuring device not the little red ball. HTHs. |
William Badurski (Billb)
Junior Member
Username: Billb
Post Number: 118
Registered: 6-2001
| | Posted on Saturday, December 21, 2002 - 9:15 am: | |
Hello Dr. Ibrahim,
I've used the "Colortune" glass spark plugs with mixed results, but find that just working with an electronic tach connected to one distributor works best for me.
I set the tach on "4-cyl" for most needle fluctuation, as I'm not interested in the actual RPM reading. I also place a large window fan in front of the car during this operation, as I've found that the engine speed and mixture requirements change somewhat when the dual cooling fans switch on and off. The window fan minimizes this occurrence during the rather lengthy carb adjustment procedure.
With the engine warm and idling, first check carb airflow synch using a "Uni-Syn". Work with the right side of each carb first, as this is the control side where the carb throttle levers attach to the linkage. Make sure the speed stop screws are backed out on all but the rear carb, then adjust the 10mm nuts at each lever to match airflow. Next move to the left side of each carb and repeat airflow check, but in this case match flow using the 8mm locknut and air bleed screw.
Once airlfow is matched, turn idle mixture screw on first carb in until RPM loss is observed. Back screw out and observe RPM gain. After a certain point, no further increase will be apparent. Turn screw in again to point where RPM would just begin to drop. Move on to following carbs and repeat for each. Finish by resetting idle speed at rear carb, then turn speed stop screws on other five carbs in until they just contact the throttle levers. |
JRV (Jrvall)
Member
Username: Jrvall
Post Number: 411
Registered: 11-2002
| | Posted on Saturday, December 21, 2002 - 9:10 am: | |
Dr., Do you have a "Color-Tune" (see thru spark plug), and an Air Meetering Tool (uni-syn, etc.)and an adapter for the carb tops to air meetering tool? |
Dr. I. M. Ibrahim (Coachi)
Junior Member
Username: Coachi
Post Number: 158
Registered: 5-2002
| | Posted on Saturday, December 21, 2002 - 9:03 am: | |
I have been told that my daytona runs a little rich. Can anyone give me a brief synopsis as to how to lean that mixture a bit? I have the workshop manual, but i don't think I need a total tuneup... any hints please? |
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