MG MGB and MGB GT Tech Talk
I've been considering buying an instrument (why not...it's only money) to measure the fuel/air ratio in my engine's exhaust gas. I've read about/seen several on the internet for under $100.
Anyone out there using these things? If so which do you use and where did you get it?
Appreciate any other comments on them.
I have a KAL-Equip R89 that I got on ebay for about $90. Seemed to work great the first 3 or 4 times. I was able to get noticeable changes in %CO reading from small turns of the HIF mixture screws. It was put away for awhile and after that, I could not get a stable reading. These portable meters are probably best when used together with the RPM rise/drop technique described in the owner's handbook and Bentley's.
Yes
You can go to Autozone for the cheapest oxygen sensor and install it in an available port as near to the engine as possible. Then attach the wire to your voltmeter(non digital)(Millivolts as I remember) and you are in business for $15.
The better, more expensive heated sensor works even better. They are $35.
The kits are the same thing with a gage with a colored dial.
We did this on our Spit when we added dual HS4's. We messed with it for a while and finally relied on the butt dyno. When the car ran well we took the sensor off.
The link gives you a site where we got the info and a lot of insight. Page way down. http://www.bob2000.com/carb.htm
Larry
The Autozone stuff is narrow band and OK within one point or so of Stoichometric (being made for use in engine management systems). If you are looking at a tuning tool for experimenting, you will be better served with a wide-band unit and those are a bit more costly... I think I've seen them for as low as $150 for a basic set-up but I haven't looked for a year at least.
I've used a Innovate LM-1 wide band that I borrowed from a friend. Does a great job but is not cheap for a tool that you will use once and a while. About $300. If you don't want to weld a bung to the exhaust, a tailpipe sensor clamp is another $75. Even though I was very close to having the carbs tuned properly manually, the guage really helped dial in the air/fuel mixture on the road.
http://tunertools.com/proddetail.asp?prod=IN-3723
Charlie
Something else to think about is a dual EGT gauge, thats what we run in the race cars, one snesor on the fornt header pip on on the rear, that way we are able to monitor each carbs fuel mixture. You can buy the whole set up from Aircraft Spruce for about $120.00, they are very commonly use in the airplanes.
One thing about using a AFR or EGT is you need to tune at WOT, you'll be a little rich everywhere else, and folks that don' realize that will pull thier hair trying to get good number at idel or part throttle only now to be way too lean at WOT.
tomkatb Wrote:
As was said above, the cheapies are nothing more than a run of the mill narrow band sensor, available in a junk yard for $5, and a voltmeter, available in suitably matched low quality for less than $10. They only really tell you if you're above or below 'stoichiometric matched amounts of air and gasoline.
The wide band units read across a wide range of air/fuel mixtures, so you can 'dial in' the mixture you want to run at. I have one which has been extremely informative for my project retrofitting efi to MG's, Triumphs and Jaguars. I also can to understand why the Weber setup runs nice on my car-it's at an AFR of 12.5 ! The proper value for the environment and economy is about 15. Some nice performing SU's I measured at about 11-12
A proper A/F ratio is designed to change under different needs. For best power your A/F ratio will be around 12-13:1 at WOT. It'll be at 14.5-15 while maintaining speed, and considerably higher when decelerating. That's why you need a wide band meter to measure all these things. Only tuning for best idle will be a disaster.
By the way. LM-1 meters are NLA. They're selling the LM2 for $479 plus options. http://www.innovatemotorsports.com/
I surrender. Not as simple as I had hoped.
I'll use the old fashioned method, and invest my $100 in chocolate chip ice cream (and a longer belt).
roflmao !
But seriously, who really needs an excuse (or rational reason) to get a new toy/tool?
I've got a "dash dyno" that I have yet to use but I still like it!
The Edelbrock unit is only around $130. Its a fair compromise and effective for the price.
I looked into doing this about 2 years ago... apparently has not gotten any less expensive...
I am drooling over this one..
http://www.innovatemotorsports.com/products/g5_gauge.php
Having an LM1, I can tell you its worth every penny. You don't need all the fancy extra crap like the computer interface, just a gauge or handheld unit that tells you what's happening in real time. That'll get you everything that a dyno will tell you once you learn to interpret the info. The biggest issue with these is TMI (too much info). You have to slow sampling down to the slowest possible rate and watch the lambda meter if you have a digital readout. Otherwise its info overload, which is good and bad. The most essential thing is to NOT permanently mount it in the car. TMI is distracting - worse than cell phones and texting while driving a stick.
I've got an older (discontinued) PLX unit that works great. Has a dash mounted gauge and everything. The newer ones are even nicer as you have the option of running an OLED screen gauge. This allows you to have several different sensors all outputting to one gauge. You can also do custom gauge faces and even change whether you want a needle style gaud, a digital gauge or even a graph. Pretty cool stuff. Get expensive though. Here is their website:
http://www.plxdevices.com
I have this one.... Fantastic, never use all the features though.
http://www.stackltd.com/instruments.html#Lambda