jotto

Have been reading various posts about timing and ignition as well as car setups and alot of members are using meters to get the air to fuel ratio results. Im assuming this means you can tube your carb more accurately.

Is an AF meter a nessecity or just something that should be considered for high output, modded engines. Not sure how much one of those babies cost but it may go on my wish list which seems to be growing by the day.

Im fairly new to tuning and getting the Vette running sweet but I like to do a job properly if Im going to do it at all.

BigBlockk

You don't have to have one of these to get your car running good. They do help to get a razor sharp tune. This could help the beginner if you know how to read the results and know the systems within the carburetor.

BigBlockk

Later.....

jotto

I have seen that you should have various air/fuel ratios at idle cruise and WOT and that one of these meters will help tune/jet the carb for this.

Is there a reasonably cheap one that you can use between cars, ie stick a probe in the tailpipe instead of using a fixed probe welded into the exhaust?

Solid LT1

LM-01 AFR is what I use. They are sold through Summit or Jegs, I would recommend the RPM/data logger output set-up too.

griffths

If you have a laptop you can also use the LC-1 cable from Innovate Motorsports. It is cheaper than the LM-1 and does the same thing but if you want to log RPM I believe you will need the LM-1 since the RPM converter won't connect to the LC-1 cable.

Regards,

Jay

jotto

so does the laptop act as the meter? would be cheaper than buying a complete unit.

Gordonm

The laptop just keeps the data. The unit is by itself. HP is not cheap. A wideband AF meter is a great tool for seting up the carb. I have the wide band from Innovate also.

zwede

Yes, the laptop will show you a real-time display and also log it to disk for later review/graphing. I think the LC-1 will do rpm also with an optional rpm-module.

ajrothm

I also have the LM1 with the LMA3 converter from Innovate. It works awesome but its like opening "Pandora's box" when you start tuning with it. The tuning will never end and you will always want to get it perfect. I have it on my turbo-hayabusa.. its the ONLY way to tune a forced induction setup. I highly recommend a LM1 if you need a wideband.

olescarb

to me the use of a air/fuel meter or a exhaust gas analyzer is as important as a timing light is to proper tuning if you really care how your (or your customers) corvette runs. there are still those who set the timing and advance curves by ear and "read" spark plugs
henry @ oles

MotorHead

The LM-1 wideband is the probably one of the best things I ever bought. YOu really have no idea what your carb is doing with regards to A/F ratio without actually seeing what the levels are at idle, cruise, light load and WOT.

For example if you are reading plugs, you really should forget about that on a street car. You could be rich and idle, pig rich at cruise and lean at light load and WOT. When you "read " your plugs they look pretty good, maybe a little dark but nothing to worry about, meanwhile you are dangerously lean at WOT and could be damaging your motor and not even know about it. This example happened to me, my plugs were dark but my WOT was up in the 16's to 1, not good .

With the LM-1 I got everything sorted out and I get 20 MPG on the highway with a 550HP motor, now that I have my Race Demon back on I bet i am getting even better gas mileage.

enkeivette

You have a Turbo Hayabusa?! You're absolutely insane. Be careful.

And I was just wondering, would this meter work sufficiently? It's very affordable relative to the others.

or

olescarb

as long as the units are based on a wide-band or extended range o2 sensor it should be good. if it is a standard o2 (oxygen) sensor it will only be accurate at 14.7 to 1 a/f mixture. the Innovate unit is a good tool at a good price.

zwede

Nope. Those are narrowbands and tell you nothing at WOT. You need a wideband like the FJO, Innovate, Techedge etc.

MsVetteMan

I disagree on someone's plug statement.........you can read the plugs for the truest reading of all!! Your plugs will reflect how you usually drive the car, and will indicate thus.

Meters are nice.......but nothing like yanking a plug to verify.

enkeivette

So those won't vary at WOT?

BigBlockk

You can get a wide band sensor at NAPA. Try to find the voltage for each A/F ratio step for this sensor. If you can get the voltages you can use a volt meter to read the sensor.

BigBlockk

Later.....

AKRAY4PLAY

i like reading plugs also, but i have to tip my hat to the LM-1 meter. i thought i had my car set-up pretty well after four years, after getting the LM-1 tuner, i was WAY OFF!. i had to recurve the distributor, lean the idle feed restrictors, re-jet, change high and low speed airbleeds and play with the emulsion bleed circuit for better mid-range fuel curve. the AF tuner got me a much harder launch and better throttle responce. i also went from 6-8mpg to 26mpg on a 600hp 406sb. the motor was baselined on a dyno, but did not work to full potenial on the street. now it's closer thanks to the tuner.

back to my point, the tuner tought me worlds about how and when the various circuits work on a carb work. it is amazing how you can go from idle to main circuit with little to no throttle adjustment at cruise speeds. believe it or not, but most carbs are on the idle circuit 90% of the time. the mains only come on for hard accel or heavy loads. with the price of fuel lately, the tuner will pay for itself and you'll get better performance.

Gordonm

I don't disagree much but this is wrong. Reading plugs is very difficult and only gives you an average. Even if you put in new plugs before a 1/4 mile run you still have a period of idling and some throttle opening and then a period of WOT. If you shut it off right after the run you still have a bunch of different throttle openings. Not very accurate. Also with unleaded fuel and high energy ignitions the plug color will not give you an accurate reading.

With a wide band that records your AF ratio you have real time readings and can map it with rpm and with the Innovate you can have throttle position and manifold pressure and many other inputs. How many dyno guys are reading plugs. They all use electronics now for the best results.

UKPaul

A lot! It used to be easy to do "plug chops" where you'd run at WOT for 2 miles, dip the clutch & kill the engine. Reading the plugs was a great way to get WOT mixtures adjusted about right (and a great way to get some nicely burnt fingers!). Now, with the same engine, it's a pita. Not only is finding somewhere to run at WOT for 2 miles impossible, unleaded fuel burns so much "cleaner" (& hotter???) than the old leaded that it's hard to tell slight differences. Changing a main jet size by one step used to give a marked difference on the plug color, doing it now gives such a slight difference that it really is difficult to tell. You'll get color changes by going 2 or 3 steps away from ideal, but it's not going to be as accurate as it once was. Or maybe my eyesight is failing? Getting the mixture right at less throttle openings was a bit more tricky as you'd never be sure what circuit was working prior to looking at the plugs, & it took a lot of experimenting before you'd get it about right for all throttle openings. Obviously it can be done & I've no doubt that there's gurus out there that can tune carbs by looking at the plugs, but I've given up. This darn unleaded fuel has made it so much more difficult to see what's going on in there.
I've been looking at wideband sensors & reckon the price is going to be about £250 upwards delivered to the UK, roughly. I can't afford that & was wondering about reading voltages directly from a wideband Bosch O2 sensor bought from a local shop. Now BigBlockk has suggested the same thing I know that I'm not being stupid!
For years I adjusted jetting by looking at plug colors & doing test runs (does the engine pull better at WOT if the throttle is backed off slightly? Yes? Then it's running rich. Etc, etc, etc). Having fitted FI to a carburrated engine I know what difference accurate A/F settings can make to power/performance (lots!) & a sensor is the way to go (getting a Q-jet set up accurately without one is well beyond me).

NB. Killing the engine & coasting to a halt is a must when doing "plug chops". If you slow to a halt by closing the throttle then, if there's any wear at all in the motor, it'll suck a small amount of oil into the chambers which will "corrupt" the plug readings.