RebekahsZ Posted February 17, 2013 Share Posted February 17, 2013 I have 1" of rear tire clearance with my stainless exhaust-do you think that's enough? Quote Link to comment Share on other sites More sharing options...
Snailed Posted February 17, 2013 Share Posted February 17, 2013 (edited) That should be ok, but if you can get another 1/2" or so I would do that. What is the O2 question? Edited February 17, 2013 by Snailed Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted February 17, 2013 Author Share Posted February 17, 2013 Oh-oops! Does it matter where I mount the O2 sensor within the collector? I had them in the first section of my tail pipe before but I'm re-doing my exhaust. If I don't get any feedback, I'm gonna just put them right in the middle of the short collector (length-wise). Quote Link to comment Share on other sites More sharing options...
Snailed Posted February 17, 2013 Share Posted February 17, 2013 To get the most useful reading I would try to put it in a spot where the gases from all four cylinders have completely mixed. So if it's going in the collector, put it as close to the small end as practical. Also make sure the tip of the sensor is angled down so moisture doesn't collect in it. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted February 17, 2013 Author Share Posted February 17, 2013 Thanks! Quote Link to comment Share on other sites More sharing options...
Domzs Posted February 17, 2013 Share Posted February 17, 2013 Rec. 6-8 in after the collector . Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted February 17, 2013 Author Share Posted February 17, 2013 That's gonna be impossible to get it that close due to the y-section that splits off one way for an exhaust cutout and another way for the real exhaust. The split is right after the collector so I'm space-limited. I've gotten answers ranging from as close to the exhaust valve as possible to 6" after the collector. Both credible sources. I'm gonna conclude that it probably doesn't matter too much and ill put it wherever it will fit. Quote Link to comment Share on other sites More sharing options...
Domzs Posted February 17, 2013 Share Posted February 17, 2013 That's gonna be impossible to get it that close due to the y-section that splits off one way for an exhaust cutout and another way for the real exhaust. The split is right after the collector so I'm space-limited. I've gotten answers ranging from as close to the exhaust valve as possible to 6" after the collector. Both credible sources. I'm gonna conclude that it probably doesn't matter too much and ill put it wherever it will fit. I don't think it's a good idea to have the O2s after the cutouts . If the cutouts are opened , the ECM won't have any feedback from the O2 sensors . That's just my opinion . Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted February 18, 2013 Author Share Posted February 18, 2013 I totally agree. That's why the o2 sensor is gonna have to be very close to the primary tubes in the collector. Ill just have to re-group if there are problems. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 18, 2013 Share Posted February 18, 2013 (edited) I'd reinforce the collector where all cylinders merge, or further back (6-8" max sounds about right.) You are looking for a feedback signal for the ECU, and if you examine where OEM's put em, it's in the collector or as close downstream as possible to the collector. For an ANALYTICAL TUNING APPLICATION (Stationary Dyno) you want as close to the exhaust valve as you can get. This is a different dynamic, and you CAN'T use a single cylinder trim the entire bank, much less the entire engine! Unless you have a single-cylinder engine, this makes "as close to the back f the exhaust valve as you can get" incorrect for your application. It would be the same as putting a single O2 in a primary tube! (Maybe OK for EGR, but not the O2 sensor!!!) The further down the pipe you put it, the more latency you will have in response to transient changes. We have our Bonneville Car using an O2 sensor IN the collector and the secondary O2 for the Horiba Analyser used on the Dyno about 3" downstream on the other side of the collector flange. We get almost identical readings when doing dyno pulls. Response is VERY fast, and the catalogs fom both sensors synchronise with each other very closely. When we used a Horiba in the tailpipe at the back of the car, our maps were off across the board. Until we realized we had to hold a load point considerably longer to let the reading stabilise at the outlet of the pipe. Ideally we. Would have had fast acting WBO2's in each cylinder to check and trim the ECU accordingly, but at some point with a 40 year old + engine (and being current record holders) you just shrug and say "why waste the money?" If we were contested, maybe... But we're fat, happy, and resting at the top right now waiting for all those stock 180mph 240's all the kids swear they have to come bump our record and do more development. Already got a sacrificial header ready to install bungs! Edited February 18, 2013 by Tony D Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted February 18, 2013 Author Share Posted February 18, 2013 I love this site and I might have a little man-crush on Tony D. That helps a lot. For example: driver side I gotta put sensor directly into the collector, which is very short, basically just a reducer. On passenger side it would be more convenient to put sensor about 2' down the tailpipe/headpipe due to where the wiring is for the sensor. (The Sanderson headers are different left to right). I think I can run the sensor wire differently and put the sensor in the passenger side collector so that they are the same. Quote Link to comment Share on other sites More sharing options...
Snailed Posted February 18, 2013 Share Posted February 18, 2013 Ideally we. Would have had fast acting WBO2's in each cylinder to check and trim the ECU accordingly, but at some point with a 40 year old + engine (and being current record holders) you just shrug and say "why waste the money?" You might find shrugging and then reading the spark plugs a little more effective for individual cylinder trimming. That's what us kids with only one WB do. Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted February 18, 2013 Share Posted February 18, 2013 This is the Bonneville car Wiki D is talking about. No doubt what they do now with no real push by challengers for the title forcing them to get the last little 0.005% of performance out of the car to keep their record. ANY car at bonneville is by definition reaching the point of diminishing returns where adding a Zero to the budget adds a few percent improvement at best. How much would the difference between eyeball tuning the cylinders vs individual cylinger wideband sensors gain you? 2%, 5%? at HOW much cost? Best wait until it is needed to stave off the challengers. You might find shrugging and then reading the spark plugs a little more effective for individual cylinder trimming. That's what us kids with only one WB do. Quote Link to comment Share on other sites More sharing options...
Snailed Posted February 19, 2013 Share Posted February 19, 2013 I totally understand the strategy and agree with you and him on that. I was just pointing out that making use of more ba$ic techniques is very useful. A wideband O2 should be used with reading plugs and listening to the engine, not instead of IMO. I thought the winking face sort of implied my tone...damn internet. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted February 19, 2013 Author Share Posted February 19, 2013 (edited) I'm just gonna let the LS2 computer do the reading for me. I'm not that smart. How much of the sensor needs to be inside the pipe? The bungs bought are kind of deep. Edited February 19, 2013 by RebekahsZ Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted February 19, 2013 Share Posted February 19, 2013 . I thought the winking face sort of implied my tone...damn internet. See my sig. Through part of that problem is on my side, Now I'm back home in NZ I'm on rural copper line dialup and images, tags and insterted smileies often don't work. Or take an hour to finally decide to load when something kicks the cache or some other software does somethign else strange. Didn't see that winking face before... or now either... grrr... bloody copper wires... I miss the fiber to the basement connection my China apartments had. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 20, 2013 Share Posted February 20, 2013 (edited) I shy from telling people to read plugs as generally they will do it wrong, and draw incorrect conclusions. In fact, most "plug read" engines are several percentage points consistently rich and down on power. People read the exposed extended tips, and don't use an illuminated loupe to read the ring up inside the plug (which is where you need to read it!) Reading the extended portion near the ground electrode where it runs hot and burns off deposits results in a lean reading, and is very variable. That base ring is very consistent in comparison. Universally we are to,d by people looking at our plugs "you are too lean!" But our dyno testing shows otherwise. Once you know to read the bases with an illuminated loupe, it doesn't take too many plug reads on a dyno seeing the results to know "what looks right" for a particular family of engines. As long as the junction of the sensor is in far enough for the intake louvred to pick up a sample... You can always have your bungs turned down on a lathe to allow deeper setting of the sensor in the exhaust flow. Edited February 20, 2013 by Tony D Quote Link to comment Share on other sites More sharing options...
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