Air/Fuel gauges (yes more newb turbo questions!)

[Guest jt240z]

I do understand your concerns about a DIY kit and the Tech Edge unit. I will say that I've had the opportunity to verify MINE against a couple of "Professional" units and have found it to be accurate to within +-.1 A/F of both. The interesting thing was that both units were on either side of the TechEdge unit or right on the money. One unit read lean by as much as .1 while the other read rich by as much as .1 relative to my WB. In each case I had a downpipe bunged with two O2 bungs and the readings were compared with both units in each hole.

 

I know that accuracy is a relative thing, but I feel for (at least mine) the .1 A/F error is within acceptable margins. For many the $300 savings is well worth it. If you have questions as to the accuracy of the WB you build, then simply pay for a 3 pull baseline (Usually for less then $75) and compare. Don't dismiss a product simply because it's a DIY product. I may be dating myself here, buy some of the best audio amps that money could buy were sold as a DIY kit from Heath Kit years ago.

 

Another note on accuracy... How do you know that ANY WB meter is accurate regardless of who made. You could just as easily buy a new defective unit for $5000. Always verify your calibration sources. If you're depending on using your WB to "calibrate" your engine, then make sure that the instrument is in good working order. Do a comparison with calibrated gases or compare it to a known good unit at a dyno.

 

The Tech Edge units still beat the pants off any NB meter out and, if built properly, can be a very accurate way of getting an engine in tune. The bigger issue is how and where your tuning points are derived. I would like to see more discussion on the methodology behind the tuning effort.

[Guest bastaad525]

But for that matter, how do you know that the dyno shop's wide band is accurate? Maybe it's an older unit and they haven't had it calibrated or maintained in a while. *shrug* It's all relative..... To me stuff like reading plugs and hearing ping are some of the only really reliable indicators that something can be wrong. Not to say that I think that dyno shops' widebands are defective. Heck last time I went to the dyno they didn't even use the wideband, we just kept doing pulls and making adjustments til I got my peak power and torque. I guess the guy figured at my peak power I shouldn't be running too rich or lean... I didn't even realize he wasn't using it til way later, and I felt the same way.... if that was peak power, everything must be running good.

 

Okay so, an A/F gauge is definately out of the question. I'm still very interested in the EGT sensor though, it's still within my price range.... a nice looking Greddy unit is going for about $180. But jt240z raised a good question, how do I know what temps are okay and which are not for my setup? It all seems relative once again. If I get one I will do as cody suggested and just start with stock boost levels and timing and go from there, of course temps will go up as I raise the boost, but how do I know how high is too high? I agree that someone whos made use out of one of these needs to share their secrets

[BLKMGK]

It IS all relative. My W/B compared to the local dyno is about 1 A/F point off which would seem to suck except they use a tailpipe sniffer and NOT a bung (this sucks). In fact looking at my logs I find that their sensor is also reading several hundred RPM "slow" due to pipe length!

 

I agree that even buying somehting like the FJO has some risk. Free Air calibration would seem to rule some of this but using a test gas would be even better. To me .1 accuracy is incredible - anything within .5 is good enough for me actually. The trouble is that since it's ALL relative you might be close to someone else's meter and still be off or I might do something during assembly that tweaks mine <sigh>. Buying something like an FJO or AEM is worth it to me but no way will I pay what Horiba and Motec want, I know those guys are pirates.

 

As for EGT... see above. If you REALLY want to tune then buy the tools needed and tune. You might be surprised at what you can learn with a good A/F meter, I've learned a ton. I think I've said it before - I will NEVER try to tune a car without a W/B ever again. That said - sometimes you can "fool" a W/B too so you have to understand those circumstances too. To REALLY tune I think I'd want an EGT, W/B, and a cylinder pressure sensor ($$$). I spoke to someome who works with the pressure sensors everyday for a big diesal manufacturer. He said that the slightest change in fueling and whatnot was readily obvious on the pressure graphs. I'd LOVE to have one of those to tune timing but they simply cost too much for any one person to afford at a hobbyist level. Hopefully they will come down like W/B have....