JCan Posted October 18, 2012 Share Posted October 18, 2012 Over the past couple of days, I have been reading about 02 sensors (wideband vs narrow band) and how they can be used as feedback to adjust air/fuel mixture. Really cool stuff!. I have also learned that a narrow band 02 sensors were inexpensive and one could use a volt meter to read the result. We are running 6 - 2 - 1 headers on our L28 with dual SU carbs. And the ex-manifold combines cyl 1,2,3 and cyl 4,5,6 into separate tubes! Am I correct in thinking that If I placed two O2 sensors in the 2-1 pipe that I can measure and adjust fuel mixture of each carburetor at idle/3000rpm using my volt meter? (noting the SU carbs air fuel mixture is only adjustable at idle and when driving). I would greatly appreciate your input on this Thanks Jim PS I plan to take the car to a dyno shop anyway, they will mostlikely remove my sensors and place their own wide band sensor... right? Quote Link to comment Share on other sites More sharing options...
johnc Posted October 18, 2012 Share Posted October 18, 2012 Adjusting mixture on a SU carb involves repositioning and/or changing the needle. You should get a book about performance tuning SU carbs before making any mods to the exhaust. Quote Link to comment Share on other sites More sharing options...
JCan Posted October 19, 2012 Author Share Posted October 19, 2012 (edited) John C I purchased Ztherapy carbs and Steve modified needles based on our discussion of engine size, cam, and compression ratio. I expect that I will not need to mess with the needles. As you know, there are adjustments that I can make and need to be made once we start the engine up. These include float bowl level, linkage (both at idle, 2krpm, and choke) and most importantly, fuel mixture (the screw on the bottom of the carb). It is the setting of the screw at the bottom of the carb that i am referring to (and also balancing float bowl level between the front carb and the rear carb). I think I might be able to spend a couple dollars ($30 for 2) and dynamically measure the fuel mixture with the car under load (driving up hill at constant speed for instance) and compare the front carb setting with the rear carb setting and adjust. What do you think? Attached is a picture of the motor we are building. Jim Edited October 21, 2012 by RB26powered74zcar Please Resize Images to: 1024 x 768 pixels or close, before placing on HZ. Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted October 19, 2012 Share Posted October 19, 2012 (edited) Placing a bung on either stream is a cool idea. A multimeter might not be able to give you an accurate reading. Use a graphing meter if possible! That is trumped by the fact though that a simple O2 is not accurate. It does not tell you how lean or how rich you are, only that your in the window of things sort to speak. Buy yourself a wideband. An LC1 or what ever brand, with some kind of output you can watch and record if need be via laptop or whatever. Buy one you have to calibrate. Buy the cheapo 02 bung caps so you can switch back and forth between both and cap them when your done so the wideband does not get damaged over time sitting in the exhaust stream. Buying 2 widebands would be cool, but costly. I would agree with john about the buying the "book about performance tuning SU carbs". All you really need is 1 though and measuring all 6 at once in a single pipe. Symmetry is the key to dealing with these carbs. All things being equal and all. Any anomalies in the separated streams would be chalked up to engine integrity at that point. You must be prepared to be ultra anal on your adjustments... and believe me it can and is done. Edited October 19, 2012 by rayaapp2 Quote Link to comment Share on other sites More sharing options...
duragg Posted October 19, 2012 Share Posted October 19, 2012 You want Wideband for sure, and if you can put one on each section you are a smart man. Best investment I ever made for tuning my DCOE powered Z. The difference between lean stumble and rich bog can be tricky to determine. 1 Wideband and a 6 channel EGT from like an old aircraft GEM601 would be ideal... Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted October 19, 2012 Share Posted October 19, 2012 You want Wideband for sure, and if you can put one on each section you are a smart man. Best investment I ever made for tuning my DCOE powered Z. The difference between lean stumble and rich bog can be tricky to determine. 1 Wideband and a 6 channel EGT from like an old aircraft GEM601 would be ideal... Oh your sick! EGT monitoring would be the way to go, but complete overkill. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 20, 2012 Share Posted October 20, 2012 Six Widebands and EGT's like on a properly outfitted Engine Dyno are ideal.... And there are roadgoing systems that do that. As duragg mentions, Aircraft Spruce has neat six-channel engine performance computer/dataloggers that are reasonably priced. JeffP is trying to figure out how to put one in his ZX Dash! Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted October 20, 2012 Share Posted October 20, 2012 Six Widebands and EGT's like on a properly outfitted Engine Dyno are ideal.... And there are roadgoing systems that do that. As duragg mentions, Aircraft Spruce has neat six-channel engine performance computer/dataloggers that are reasonably priced. JeffP is trying to figure out how to put one in his ZX Dash! I dont think it needs to be said that you and Jeff are also a bit sick/twisted... but there you have it. Ill agree with ideal, but I guess Im also sick. Other than aircraft and a few twisted folk you only really see this kind of sick being used by the professional racers... that need and want every last .25 pony and inch pound of torque from their machines. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 20, 2012 Share Posted October 20, 2012 It could be merely curiousity... I mean, why rent a wind tunnel to prove "what we already knew about the S30".... Guess we didn't know all we thought we did, huh? The quest for knowledge trumps all reason. Six WBO2's... Six EGTs.... Remember I used to have access to K and J thermocouples, AND an Omega Datalogger! I had 6 on the black shark car long before those fancy WBO2's were available. "Back in the Day" it's simply how you did it! Less than 20 degrees differential between cylinders was the goal... It may not be "right" -- but it is consistently wrong if nothing else! Quote Link to comment Share on other sites More sharing options...
JCan Posted October 20, 2012 Author Share Posted October 20, 2012 Okay, On my 6-2-1 headers, we will place two bungs on the 2-1 pipe and populate with narrow band 02 sensors then measure using a multi meter. This $30 solution will allow us to tune the carbs in the garage and get them pretty close. Moving to wideband sensors is a costly approach (> 10x). I am taking this approach as I expect the money would be better toward the purchase of new seats. or other nice things we have not budgeted for. this approach allows us to eventually move to wideband sensors in the future with little modifications to the car. Thanks for your inputs. Over the months during re=assembly of the car I will continue to research wideband O2 solutions. Jim Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted October 21, 2012 Share Posted October 21, 2012 You can watch the AFR sensors with a multimeter, but its still best to be able to graph it as a multimeter samples to slow for an accurate reading. You should be able to attain idle values that way, but dont bother doing any loading samples. You can get an AFR/wideband setup with a gauge. Quote Link to comment Share on other sites More sharing options...
duragg Posted October 21, 2012 Share Posted October 21, 2012 I just troll Craigslist and find the AEM Wideband and sensor all day long for $100 to $150 bucks. Mine on the Z is toast from 100LL exposure. But I still have one in my Mercedes 560SEC which is handy for troubleshooting and max-power tuning (or at least getting close enough..) Hide discretely if you desired. Quote Link to comment Share on other sites More sharing options...
JCan Posted October 23, 2012 Author Share Posted October 23, 2012 You can watch the AFR sensors with a multimeter, but its still best to be able to graph it as a multimeter samples to slow for an accurate reading. You should be able to attain idle values that way, but dont bother doing any loading samples. You can get an AFR/wideband setup with a gauge. I agree that a wideband sensor is optimum and will likely purchase one AFTER the car is completed. However, I plan to use the inexpensive sensors to adjust the air/fuel ratio. The adjustment : matching Air flow at 700 & 2500 RPM and Matching Air fuel mixture between both carbs using the narrow band sensor at 2500 RPM) Once adjusted, because of the nature of the carb design (needle to manage air flow mixture through all demand curves) I expect the adjustments to be optimum. Once completed, for fun, I will get access to a wideband and compare my results and post them here. Jim Quote Link to comment Share on other sites More sharing options...
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