Check Your Mixture - CHEAP!

[Workshop Help]

Errr? What happened to our lovely substitute teacher? She certainly didn't offend me. Many is the time I was tempted to cane the naughty boys, but I resisted and became a better person for it. Not that the naughty boys didn't deserve a good caneing and even now those who became politicians, contractors, car salesmen, and garage owners could still use a good caneing to get them back on the straight and narrow pathway of wholesome goodness.

So, if the lovely substitute would care to return, I'm sure the class would be more than delighted to contribute to her $75.00/day substitute teacher pay. Seeing how the school district is being squeezed by the Federales over the budget, we're now forced to pass the hat and have bake sales to make up the difference.

Mildred Hargis

[Laird Scooby]

I can see the logic in your method but isn't it a bit on the err, dangerous side? Only got to move your paw the wrong way and you've got something like 650C or more to instantly barbeque your digits!

Seeing this has given me a nice idea for a cheap gas analyser, based on a simple Lambda/Oxygen sensor and a handful of cheap electronic components. In fact, add a few more cheap components and either one more or 3 more Lambda sensors and you could have either 2 or 4 bargraph displays (depending on whether you have 2 or 4 Lambda sensors) for probably about a tenner, excluding the sensors.

You could then simultaneously see what's happening either in the front half (2 sensors) or back half or in each individual cylinder (4 sensors) without risking fried fingers!

I'll need to do a bit of research on it as i've forgotten a lot of the specifics, but it's certainly do-able! Does the FI engine have a Lambda sensor at all?

Cheers,
Dave

[RadioGuy]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">move your paw the wrong way and you've got something like 650C or more to instantly barbecue your digits!<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Ah yes...but you will only do this once...[B)]




Maintained on Saturday…Drive on Fun-Day !!! 1976 FHC - 1980 DHC

[Workshop Help]

Thank you for your responses, Gentlemen.

No, the fuel injected TR7 engines did not have the air rail holes machined tho the casting bosses are present.

The one big problem with using an Exhaust Gas Analyzer in one's tailpipe is that we have, in effect, two separate, two cylinder engines operating on the same cam and crankshaft. With two carburetors, the balancing is critical to achieve the designed operational output of the engine. When they are out of synch, for air flow and/or mixture flow, the engine works against itself. With the exhaust probe inserted, the reading does not isolate which carburetor has the correct setting and which one is out of adjustment. At best, the reading is an average of the total output.

Therein lies the promise of a Colortune glass spark plug. One can see the combustion color in each cylinder and make the necessary mixture adjustment with the engine operating. The failure of Colortune is the incessant shorting out of the spark leaving a rich loaded cylinder that will ignite a yellow/orange color until it is burned out when the Colortune finally does ignite.

Now comes our latest discovery, the air rail hole which displays the actual flame color as it exits past the exhaust valve. Accurate adjustments are now possible without a spark plug misfire.

The idea of installing O2 sensors into two or more of the air rail holes is a valid one. This will enable an accurate readout of each of the sensors readings on the mixture strength over the entire RPM range. Is it a worth while pursuit? Yes, I think it is.

As for the roasted digits hazard, obviously one must be attentive to what one is doing and the various under hood activities with the engine running. Life is filled with risk.

And, yes, the fuel injected engine does have an O2 sensor installed on the Federal models equipped with catalytic convertors.

Mildred Hargis

[tencate]

Well, I've used a Colortune on my TR7s and TR8s for years with no troubles whatsoever... in fact, it helped me spot a plug that wasn't firing on my 2nd TR8---one of the little propeller blades in my 15 year old Lumenition conversion finally broke off, and all the other ones were brittle too! Since my air pump and rail are still in service on the TR7, I'm stuck with Colortune. But I do like it, a LOT.

Mildred, are you going to be at the VTR South Central Regionals? Hope so, it'll be fun to meet up!

Jim (New Mexico wedgehead)

[Laird Scooby]

You could use the O2 sensor as your mixture analyser in that case although if it's still running electronic injection, the voltage will be fluctuating rapidly i expect. If however you're running carbs and have a digital voltmeter/multimeter with a sensitivity of at least 10kOhm/V, connect the DVM to the output wires of the O2 sensor and aim for a voltage of approx 0.45Vdc. This represents a mixture marginally leaner than the stoichiometric ratio, in other words just about perfect.

If you can find a pair of O2 sensors and screw them in place of #1 and #4 air blanking plugs, you could either swap the DVM to each sensor in turn or if you're handy with electronics, you could use the LM3914 LED bargraph display driver chip to build a dedicated voltmeter for each sensor and have 2 displays. Again, the voltage to aim for is 0.45V as being right.

Not sure what the price of electronic components is like in the USA but i reckon ( excluding the sensor and a case for the displays), both displays could be built for about £10.

Hope that gives you a few ideas!

Cheers,
Dave

[Workshop Help]

Dear friend Dave, 'Whoosh!' is the sound of your most valued idea going over my head. Having reread your words, I glean a very good idea that seems doable. But, a bit of help from you will be needed.

Perhaps, if it isn't too much trouble, could you lay out a diagram or photos or something more clear in concept for us, all?

I can think of nothing more valuable than to be able to precisely dial in the most efficient settings on our carburetors. Regardless of whether they be Zenith-Strombergs, S.U.'s, Webers, Dell'Ortos, Holley's, Carter's or a gas soaked sponge lying over the open manifold, balancing the mixture along with the air flow will allow us to be the absolute masters of our engines.

Yes, I have thought of the O2 sensor inserted into the air rail hole(s). But, nothing more than that. Seeing the blue flame thru the hole was a 'Eureka!' moment in being able to now make adjustments in the mixture to the best Bunsen Blue setting. Your idea tho is superior because a true reading of the exact mixture ratio for the front AND rear two cylinders will bring about the most efficiency of the engine.

Mildred Hargis

[jclay (RIP 2018)]

Mildred,

It seems that I must have deleted the photo of the substitute teacher. I am sorry that the photo is gone. It was a mistake on my part.

Please edit your post to include the missing photo. I must admit that I have been running on empty (no sleep) for the past two weeks.

Again, I am sorry for any problems or hurt feeling I might have caused.

Clay

[url="http://web.mac.com/jclaythompson/Site/Welcome.html"]My Triumph Site[/url], [url="http://web.me.com/jclaythompson/Technical"]Technical Stuff[/url], [url="https://docs.google.com/?hl=en&tab=wo&authuser=0&pli=1#all"]Download Page[/url], [url="https://public.me.com/jclaythompson"]My Public Folder[/url], [url="http://web.me.com/jclaythompson/tr8/Welcome.html"]My TR8 Site[/url]

[dctr7]

Laird, let me get this straight, remove air rail.
Insert an O2 sensor into the hole, (assuming you can find the right threaded sensor). Then connect the leads from the sensor to VOM and look for a reading of about .45 volts. Anything greater than .45 volts is rich and anything less is lean. At that point adjust each carb to balance. Please let us know if this is really that simple and yet that accurate.
If so, can anyone describe the correct O2 sensor that would fit?

1980 TR7 Spider DHC 2.0 Ac Delco Electronic Ignition.

[Workshop Help]

Aah! A simple engineering problem. Instead of a threaded connection, would a O2 sensor threaded into a metal tube suffice? The other end of the tube could be slipped into the air rail hole so the exhaust gas pumps into the O2 sensor.

Is this what we're talking about?

Mildred Hargis

[FI Spyder]

The O2 sensor has to be at a certain operating temperature for it to work so it's position is important as the exhaust gases move past it. Placing it in a tube may isolate it from the exhaust gases too much so it never reaches that temperature.


TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

[Workshop Help]

So, either a very short tube or an adapter to funnel the heated gases to the sensor? The main problem is the threaded hole is quite small and I have yet to see any sensor that tiny.

When I view the exhaust gas analyzers on ebay, they all have a metal tube to draw the exhaust from the tailpipe into the machine. Is there an O2 sensor in the plastic analyzer case?

Mildred Hargis

[dctr7]

Has anyone been able to noodle this enought to come up with a cheap and accurate solution to get an O2 sensor in the port for the air rail?

Mildred do you know the sizing on the air rail port?

1980 TR7 Spider DHC 2.0 Ac Delco Electronic Ignition.

[busheytrader]

Mildred,

Are those your own fair hairy hands in the photos or Abner's?

Adam



TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, S/S Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes all round, Anti- Dive, Strut-Top Roller Bearings, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 14" 5 Spokes or Maestro Turbo 15" Alloys, Cruise Lights, S/S Heater Pipes, Replacement Fuel Tank. No Door Stickers. Mine since July 1986, V8 from 1991

[heronmotors]

Do Zentih carberators need to be primed when they become fuel starved? Thanks