Air/Fuel Gauges

I have not used one, but I like the idea.  Would make tuning the carbs much easier.

These are neat..

https://www.plxdevices.com

I like how you can add other modules to the single gauge.  Also it has data logging ability.  You could add a vacuum module and then data log a rudimentary load vs AF map.

If you just want to try one, aircooled.net will let you rent one.

http://vwparts.aircooled.net/I...-wideband-rental.htm

-Chris

Innovate LM1. You'll never regret it.

Ditto what Stan said. I use the same one and I got it from Aircooled .net (GREAT people to work with and good advice).

If all you want to know is "What's happenin' now?" and don't have the cash for a wide-band, then the CB performance in-dash might suit you.  Works fine for me.

http://www.thesamba.com/vw/cla...etail.php?id=1320714

That CB Performance gauge looks like a Westach unit.  I can vouch for Westach as I had a nice combo EGT / CHT gauge of theirs in a Cessna I used to have.  Quality and reasonably priced.

http://www.westach.com/catalog...php?page=PAGE2s.html

http://www.westach.com/

They have some cool combo gauges too, and I believe they will make custom combo gauges if you call them.  The combo A/F and EGT gauge would be nice for tuning...

http://www.westach.com/catalog...hp?page=PAGE10s.html

I didn't give you guys the whole story. I installed an AEM gauge and after two sensors, the thing still doesn't work right. I am not sure what the cause is and the techs at AEM were little help. The reason I went with AEM in the first place was because they claim it never needs to be calibrated. Well, after talking to many people, calibration is a good thing, even though it is a PITA. I have ordered an Innovate MTL-X gauge. I will report on how this one works. I opted for it rather than the LM-2 because I want a permanent gauge in my console. I can still get read outs with a computer hooked up.

I wasn't aware it was possible to calibrate a LAF.  What is the AEM gauge doing?  Generally, as long as the sensor is getting hot enough, and it isn't becoming contaminated (in the exhaust stream or outside on the reference holes), the volts to A/F should be constant.

Does your set up include a heater circuit for the sensor?

Make sure you have a good ground on that gauge! I have no experience with the AEM analog gauge,but the digital ones have been utterly reliable and flawless in operation.

 It HAS to have good 12V and -.

Hi Warren,

How are you going to monitor all 4 cylinders on your 914 (I assume that is what you are using for). Wouldn't the variation of the carburetor setting on each cylinder throw off the reading of the O2 sensor if each cylinder O2 ratio happens to be off from each other? I am also assuming you are getting a wide band O2 as the narrow band is useless. I use an old PLX on my supercharged Integra and it has been working out great for tuning the engine. Mine is using a VW Golf O2 sensor.

Good luck.

Eddy

I have installed the Innovate MTX-L and it works perfect so far. I am going to get the laptop set up to read the data log today, but right now I pretty happy with the numbers. At least now I can see if any tuning has made a difference.

Eddy - The top gauge is a 4 place CHT gauge. It's actually an aircraft gauge, but with it I can keep an eye on old #3, the hottest of the bunch. The O2 sensor is located in a place on the muffler that gets all 4 cylinders. I think a 4 sensor setup would be overkill. Shoot, what I have done is probably overkill, but I like knowing what is going on, particulary since I have had so many engine problems. And, I have signed up for a couple of AX's in the next few weeks, so I definitely need to know what the engine is doing.

I am confident the MXT-L gauge is giving me good, reliable information. My thoughts that I was running too rich have proven to be wrong. The AEM gauge was obviously bad. I did buy it second hand, so maybe the previous owner had the same problem.

In any case I am adding a 4-channel sensor interface to pick up RPM, so that I can tie my a/f readings to RPM. I just don't want to be looking at a gauge when I am WOT. I need to be looking where I am going.

Cool.  Would be great to record vacuum as well.  RPM + Vacuum + A/F would give you the complete fuel curve.

While you are at it, why not upgrade to a full EMS display?!

http://www.mglavionics.com/html/xtreme_ems.html

Drool.  This set up even allows for a configurable channel that could be used for your A/F sensor.  This Engine Management System is a fantastic value in the aviation dollars.. but rather pricey in automotive dollars.

That is really cool, but I am so far behind the curve on aviation stuff, hell, I can't even do a glass cockpit. I am still on steam gauges.

Seriously though, with what I have in the 914 is pretty much overkill for these engines, but like I said I want to know what is going on.

There's no such thing as too much information, Warren. I monitor all four as well. I'd like an EGT gauge.

Stan

I am not sure why you would need an EGT gauge with an A/F gauge. Obviously in an airplane, you adjust the mixture by hand depending upon altitude. In a car, you would have to change jets. Wouldn't the A/F gauge be enough?

What does the EGT measure?

Yeah, Warren-- an A/F gauge is many times better than an EGT gauge. I don't have an A/F gauge permanently mounted (I hook it up when jetting). The only reason an EGT gauge sounds good is because it's kind of a poor-mans A/F, and it's old-school aircraft. I like that look...

In an airplane, you'd primarily use an EGT to lean out the engine for best fuel economy (best range).  In that case you lean out the engine until the EGT's peaks.. then either richen it up a tad or lean it out a tad (depending on your engine or your aversion to melting pistons).

Here is a nice article discussing EGT usage in tuning an auto engine..

http://www.sdsefi.com/techegt.htm

Ron: EGT = Exhaust Gas Temperature

There is also a gauge called a "pyrometer" that measures EGT.  These are available in digital readout form.  I learned about them in truck driving school.  I don't think with the computer controls that are now used with modern engines that they are typically used anymore. 

I have been running the Innovate MTL-X gauge now for a couple of weeks. It has worked flawlessly, even through 12 runs at an Auto-Cross. The engine ran great and I could see the numbers. I am working on a read-out that shows the correlation between RPM and A/F mixture, but am having problems getting it to work right. As soon as I do get it right, I will post some pictures. Right now I am working on corner balancing and alignment to see if I can shave off a second or two on my runs. This **** is way too much fun!

Up your tire pressure by a few pounds and don't do the course with a full tank (weight). Sounds like you're having too much fun. Would you like to borrow my GoPro camera (and mounts) to record your track exploits?

Sure Jim, that would be cool. I am spending so much on parts right now, I don't have the extra cash for one.

Give me a couple days lead-time and I could meet you at the track (with the camera stuff). That would be cool!

Jim, that would be awesome. I double checked to see if I could have a visitor. No problem. The AX is on Oct 6 at Santa Maria Airport. You can spend the night with us.

I just ordered an Innovate 3844 MTX-L from Amazon. $183 to my door. This is an all-in-one unit, it comes with a Bosch wideband sensor. The power and controller for the sensor is in the gauge head. It has an analog voltage output, which is cool, because I can hook it up to my Megajolt ignition and datalog AF ratio, load(throttle position sensor, not MAP) , advance, and rpm. Then view it later on the laptop. Pretty cool!!

Danny, someday I hope to understand the explanation of what you just posted...it's significants...and why I should continue my beans and rice diet until I've saved $183.

My Spyder is pretty much nailed down in tuning. I am building a twin-plug mechanical injected 911 monster six though, for a 1972 911 coupe project. That is really what I bought the wideband for, to set up the fuel injection properly. Anyway, if you can datalog your rpm, load, and A/F mixture, you can adjust your fuel and/or spark to maximize power and make it lean enough that you aren't washing the cylinders down with gasoline.......

I do have an O2 bung in my Spyder exhaust, and have always been curious to KNOW the mixture. I didn't jet my engine, Jake did.