I have 94-97 Groty headers that I just put onto my car and there is less than a 1/4" clearance between the trans. pan and the O2 bungs, meaning there is no way to hook the O2's up to the bungs in the headers. I can most likely drill a couple holes in the exhaust piping after the headers and have the bungs welded in and run the O2's to that, but would it even be worth it for my application? I plan to run 110 octane which is leaded every now and then, I have heard leaded gas eats up these O2's anyway, is this true? Would the O2's even do anything for my car after it gets dynotuned... I know factory it adjusts air/fuel to run a certain air/fuel ratio based on tempreture etc., but on a car that is tuned to run much richer (around 12:1), Would running O2's mess up the settings?

List of whats done to the car is below

-LE 1 heads (flow 262/183)

-LT1 ported intake with 58mm throttle bores

-LE 1 cam (mid 220s duration, over .570 lift, tighter than 110 LSA)

-ARP head bolts

-ARP 7/16 rocker arm studs

-ARP polylocs

-Comp 5/16 flat pushrod style guideplates

- NGK TR6 plugs

-COMP chromoly pushrods

-CSR Electric waterpump

-Cloyes Double roller timing set and chain

-3600 Vigilante converter

-3.73 gears, on 10 bolt

-Transgo Shift kit

-hypertech 160 degree termostat

-groty 1 3/4 long tube headers

-summit X-pipe kit

-BBK 58 mm TB

-1.6 Comp pro mag 7/16 Rocker arms

-SVO 42 lb/hr injectors

-Cold Fusion Nitrous kit (150 SHOT)

-MSD window switch

-Cold Fusion fuel pressure safety switch

-walbro 255 fuel pump

-B&M trans cooler

-LT4 KM

-MSD ignition Coil

-UMI Lower Control Arms

-UMI panhard bar

-Moroso cold air intake

-BFG drag radials

-Clevite H main bearings

-Clevite H rod bearings

-Clevite cam bearings

-ARP main bolts

-Total Seal file to fit, ductile iron piston rings

-Moroso high volume oil pump

-GM Tall, polished valve covers

 

If you want to run closed loop you have to run O2 sensors, otherwise you can run continuously on PE mode without them.

 

yeah you need your O2's

 

Its possible to run in open loop. Since you are going to be running leaded fuel, you run the risk of contaminating the sensors. They are rated to work for 50 hours with lead, so its not necessarily an "immediate" failure. Problem is you will never be sure if they are contaminated or not.

An alternative approach would be to run the O2 sensors on the street, in closed loop, then pull them and run in open loop when running leaded fuel. Your chip would have to be optimized for the open loop operation.

You will also have a problem with locating the sensors too far away from the engine. Even with the sensors in the header collectors, a lot of 93 owners convert to 4-wire heated sensors so they will work correctly. Putting them even farther downstream in the exhaust pipe wll make it worse.

The O2 sensors only control the A/F ratio at idle and part load. They use a hard programmed value of 14.7:1. Your tuner doesn't alter that setting. He alters the PE mode target A/F ratio, and there's no O2 sensors involved when you're in PE mode. It doesn't matter what your WOT tune is, and using O2 sensors will not "negate" the tune.

I run open loop/speed-density, with a 300 shot of dry nitrous..... obviously running heavily leaded fuel. But I also use an aftermarket ECU. The "tune" is backed up with a large number of pulls on both an engine dyno and a chassis dyno.

 

From what I made of this.. If I just run open loop I would always just be in PE mode, Would just mean that the car would just be at 12:1 air/fuel (Including when idling, part load) or wherever the car is tuned to instead of using the 14.7:1 air/fuel hard programming? Would there be any negative effect of just running on the street in open loop mode all the time then?? (Well besides the obvious of the car idling, and running like **** at part load.) I think part of the problem with the O2's is that as of right now I plan to run leaded 110 on the street, being that the current price of premium here is $3.45 a gallon, and the price of 110 oct. race gas is $3.99 a gallon, it just seems more practical to just run 110 octane all the time for now atleast. How will this heated 4 wire O2 conversion help with my problem of location of the O2 bungs on the headers (not enough clearance there to put the 02 sensors in the bungs, since they are 94-97 headers, and the trans pan on a 93 doesn't allow enought clearance for them)? Are you suggesting that if I run the heated 4 wire O2s, that I would be able to run them from further away (the piping after the headers)?

 

The best thing to do would be to put the sensors in the collectors, AND convert to a 4-wire sensor. That would require new bungs in the collectors, and pluggin up the old ones. If you move the sensors to the exhaust pipes, even 4-wire heated sensors might not be enough to keep them at operating temps.

I'm not sure why people claim that if the ECM is on open loop, its running in PE mode. That doesn't make any sense. You may need to convert it to PE mode to get a decent tune, but that doesn't mean it will always be at 12:1. PE mode calculates a different target A/F ratio for different operating conditons like coolant temp, etc. Its possible to tune it for economy at low throttle positons.

Are you absolutley certain you need 110 octane for the 150-shot? Seems excessive for the engine combo you list, unless the compression ratio is extremely high.

 

no, I don't need 110 octane at all, long as a retard the timing a couple degrees I could acutally run on 93 octane. I am running stock pistons, and heads were barely even milled, even with the thinner head gasket I think i'm only at 10.6:1. BUT, I was just wanting to run it cuz it doesn't cost much more than premium currently (about .60 cents a gallon more) and I would be run more timing.. and it smells good, lol. Would there be any real negative effects from just running it on open loop for now (besides idling rougher)?

I do see your point with the tuning it for economy at low throttle positions thing, but I truely don't believe this car is going to get very good gas mileage either way with my driving habbits. I was getting about 12 mpg when the car was stock with highway and city driving combined, so i'd be happy to get 9-10 MPG with everything done to it. But anyway... Would there be any real negative effects from just running it on open loop for now (besides idling rougher)?

 

ttt

 

ttt

 

Please read the "sticky" at the top of the forum topic list, regarding abuse of "ttt". Do not use "ttt" or any other means of bumping your post to the top more than once in a 24-hour period.