test spark plug

6

69tr

Jedi Trainee

Offline

• Sep 18, 2006

• #1

I just received my new Victoria British catalog.(T6.39) I saw an item on page 26 that looks interesting. It is the Test Spark Plug. It is supposed to tell you if your fuel mixture is correct by the color of the fire.

Has anyone tried this item? How does it work? Does it work? Can it be used with dual carberators?

I guess I believe that if it seems to be true it is usually too good to be true.

 

T

tomkatb

Senior Member

Offline

• Sep 18, 2006

• #2

Here is the scientific way. Buy the cheapest O2 sensor at the local parts house and install it as near the head as possible.
https://www.bob2000.com/carb.htm
Amazing, my kid did this to his 454 chevelle with a holly 4bbl.

 

T

tomkatb

Senior Member

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• Sep 18, 2006

• #3

I actually have a colortune. Never really used it.

 

MGTF1250Dave

Jedi Knight

Silver

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• Sep 18, 2006

• #4

Aloha,

I have a colortune and have used it. It can be used on dual carb set ups using the number 1 & 4 or 1 and 6 for observations. It works by observing the color of the burning fuel air mixture and comes with a chart of the various colors you want to see. That being said, it is not as easy to do. I find you need a very shaded or even a shroud over the engine to be able to see the fuel burn.

IMO it can be used to check the mixture after you have balanced the carbs and set the mixture by the appropriate manual. I think it would be hard to use the colortune alone to set the mixture adjustment.

 

dklawson

Yoda

Offline

• Sep 19, 2006

• #5

MGTF1250Dave, can you elaborate on how to use Colortune with dual carbs? I bought one more than a decade ago and NEVER liked it. Perhaps it's the condition of my engines even after rebuilding the carbs but I couldn't figure out the way to get good results on one carb without the influence of the other. A friend borrowed my Colortune and used it with his single carb setup. He said it worked VERY well for him in that instance.

 

Dave Russell

Yoda - R.I.P

Gold

Offline

• Sep 19, 2006

• #6

[ QUOTE ]
Aloha,
IMO it can be used to check the mixture after you have balanced the carbs and set the mixture by the appropriate manual. I think it would be hard to use the colortune alone to set the mixture adjustment.

[/ QUOTE ]
Very true. So what do you do when the carbs are balanced & mixture set to perfection by conventional methods & THEN the color tune shows something else? Reset the already perfectly set carbs or change to make the color tune look just right, or say OH, & leave it alone? It is never the case that all cylinders get exactly the same mixture or burn exactly the same at idle.
D

 

A

Adrio

Jedi Knight

Offline

• Sep 19, 2006

• #7

I borrowed one once and was very happy with its performance in helping me set the mixture on my TR4A (too bad the car was not as cooperative as the colourtune). In fact the colourtune helped me figure out what was wrong with the car. I have since bought two colourtunes (new on ebay for less then the cost of one new colourtune). What I do is put one in number 1 and one in number 4 so I can see how the two carbs are acting. It is a bit of an iteration process becasue as you have all pointed out one thing effects an other but with some effort you do get it spot on.

 

P

piman

Darth Vader

Offline

• Sep 19, 2006

• #8

Hello all,

I agree with Adrio, at least the same number of colourtunes as carburettors. Ideally one per cylinder as fuel distribution is not necessarily equal from the same carburettor to shared ports, this can be more so with a siamesed port.
The problem with the scientific approach of an O2 sensor is it only gives an average so is not the real solution.

Alec

 

Dave Russell

Yoda - R.I.P

Gold

Offline

• Sep 19, 2006

• #9

So how do you "optimize" two cylinders on a shared port. In the end, they are all an average unless there is one carb/injector per port. All you will find out with a color tune is that each cylinder is a little different & you end up compromising for an "average". Iteration only fine tunes the compromise a bit. Probably not even noticeable in the overall picture.

Idle mixture which you are tuning, has little bearing on the engine's mixture under load. Many times with SU's, the idle mixture must be compromised to get good performance under other operating conditions.

I personally think that color tunes are a complete waste of time & money. Plug reading, if done correctly will tell a lot more about what is happening under actual running conditions.
D

 

A

Adrio

Jedi Knight

Offline

• Sep 19, 2006

• #10

I have never had any luck with plug reading. I think this subject is one that is more a 'preference' thing. That is what one is compfortable with is the way they would like to do it and the other ways don't make sense or work for them.

For me the colourtune is more for a 'feel'. I set it at idle but then I open the throttle to see how the mixture changes with this. As you say sometimes the idle mixture has to be compromised for the 'greater good'. In fact when I said the colourtune showed me my problem it was exactly this act (opening the throttle) that gave it away. Here is what I had:
At idle both number 1 and number 4 were slightly rich. When I opened the throttle number 1 went very lean and number 4 went very rich (I may have my 1 and 4 reversed as I am going from memory), but this told me in general what the problem was.

 

RobT

Jedi Warrior

Offline

• Sep 19, 2006

• #11

I have a Colourtune and a Gunston CO2 meter and have had little sucess with either. Could just be user error though. I now just set mixture by trial and error, based on how the car is running (any flat spots etc.) and the colour of the spark plugs - looking for that nice battleship grey.

Didn't someone post earlier that "Carburetor" was in fact Italian for "leave it alone"?

 

MGTF1250Dave

Jedi Knight

Silver

Offline

• Sep 19, 2006

• #12

Aloha Doug,

By inserting the test spark plug in #1 cylinder you can get a general idea of how the front carb is set based on the assumption that the rear carb will have a lesser influence on the mixture intake to number 1. As others have pointed out, this is a general indicator.

I have a hard time observing the color of the burn, so I prefer to set up my SUs with the SU or Haynes manual then road test. I feel more confident in performing this procedure. As Dave Russell said, I wouldn't change the mixture after a successful road test if I was unsure of the color.

The colortune is just another tool along with other to do the same job. How useful that tool is often depends on the skill of the user and their preference.

 

dklawson

Yoda

Offline

• Sep 20, 2006

• #13

Of all the tasks I perfom on my LBCs... setting the mixture is the one where I have the least self confidence. I refer to my manuals (including the Haynes Weber/SU/Stromberg book). I've tried vacuum gauges, monitoring a tach while lifting the carb piston, Colortune... I still don't feel I'm getting it right. I considered buying a Gunson unit until reading RobT's post above. I have no problem balancing air flow or getting things close on the mixture but I really hope some day to be coached by a pro and guided through the process face-to-face.

 

martx-5

Yoda

Offline

• Sep 20, 2006

• #14

[ QUOTE ]
Here is the scientific way. Buy the cheapest O2 sensor at the local parts house and install it as near the head as possible.
https://www.bob2000.com/carb.htm
Amazing, my kid did this to his 454 chevelle with a holly 4bbl.

[/ QUOTE ]

You also need an Air Fuel Ratio guage, preferably a Westach analog type, so you can see the output of the O2 sensor. I you have to locate the O2 sensor further downstream because of headers, then you'll need a heated O2 sensor.

The beauty of the AFR gauge, is that you can see the air fuel ratios at all operating conditions. I will be putting one on my TR3 when the resto is done.

 

Andrew Mace

Moderator

Staff member

Offline

• Sep 20, 2006

• #15

[ QUOTE ]
...Didn't someone post earlier that "Carburetor" was in fact Italian for "leave it alone"?

[/ QUOTE ]That was yours truly, quoting Dick O'Kane (actually a FRENCH word....).

I've long wondered how a Colortune works. Is it somehow or can it be "calibrated" so that it can perfectly mimic a Champion L87Y...or an L82Y if you ran a slightly colder plug, or ???

With leaded gasoline long gone, it's not always quite as easy to "read" plugs as it once was, but the same basic principles still apply. I still go by that, my ear, "seat of the pants feel"...and my fuel log notebook, to deal with mixture.

 

T

tomkatb

Senior Member

Offline

• Sep 20, 2006

• #16

martx-5

You can read the o2 sensor with a 0-1 volt meter. We rode around in my sons Chevelle for two days changing stuff. A holley 4bbl has 4 jets, four idle mixtures. two power valves, secondary springs, and heaven know how many other adjustments. We used a unheated($20) sensor near the header. It does help.

 

OP

6

69tr

Jedi Trainee

Offline

• Sep 20, 2006

• #17

Thanks for all the info. Now I am thououghly confused. I guess I will tune the old fashoned way for now.
Thanks, Pete

 

A

Adrio

Jedi Knight

Offline

• Sep 20, 2006

• #18

I would not say it is confusing so much as an indication as to how many different ways there are to get to the end. And it would seem there is no 'cookie cutter' solution where you 'fold flap A into slot B and there you have it one perfectly tuned Triumph'

I for one have leaned a lot for this thread. Thanks to all for the input. If only my time management skills allowed for me to have a whole day (or even an afternoon) to dedicate to doing this sort of tune-up.

 

martx-5

Yoda

Offline

• Sep 20, 2006

• #19

[ QUOTE ]
martx-5

You can read the o2 sensor with a 0-1 volt meter.

[/ QUOTE ]

This is true, but if I'm going to install an O2 sensor in a carbed car, I might as well have an in car gauge to oogle at. I like the Westach analog gauge because it's buffered, and the needle doesn't do the wild dance back and forth. Sometimes it's a little tough using a digital voltmeter.

I'll bet that you got that chevelle running real good using an O2 meter. A lot of people are starting to use them as a tuning device for carbed cars. Besides, when I switch over to fuel injection on the TR3, the O2 sensor will already be there. /ubbthreads/images/graemlins/thirsty.gif