Ban1dit

iTrader: (1)

I was told that instead of buying a corvette O2 sensor, that I could just tune them out. I already have rear O2 deletes. My question is this, if I tune out all the O2's will it effect power, drivability, or make it run rich or lean? If it is going to make the car run weird I don't want to do it. However, it would be nice not to deal with O2's anymore.

WKMCD

iTrader: (2)

I run my car in open-loop MAF and it runs great in all conditions. The only 02 I have is for a wide band guage. An full SD tune is done without the 02's also.

radkon

iTrader: (2)

You will need to get the car tuned to run open loop. I can't comment on any increase in power but when running open loop you can create a pseudo lean cruise setting to help on the gas mileage if its a concern.

You can also choose to run with the MAF or with out the MAF (SD tune) as they are not related.

KVU

iTrader: (1)

Most of the cars I tune run w/o the MAF, knock sensors, front or rear o2's and sometimes no AIT. WHen tuned correctly, there is no need for any of those items.

radkon

iTrader: (2)

While I can agree on the MAF and possibly the O2s, I can't see why you would remove the knock sensors. I know some tuners "desensitize" them but I would think you'd want some warning if you get knock say from a bad batch of gas.

slow

iTrader: (7)

I cannot agree with the IAT sensor comment, it is very well needed to get optimal timing, without it, your just compromising somewhere.

KVU

iTrader: (1)

You are a little quick to disagree. Did it ever occur to you that purpose built race cars tend to run with the timing locked out? You might want to consider other applications (aside from yours) before making a blanket statement. Please notice I said "sometimes" on the IAT.....

98redorangeta

iTrader: (10)

Yes it can be done but you will need to get a wide band to monitor things if something goes wrong with the car you wont have the o2s telling you.

KVU

iTrader: (1)

There are two main things at work.

1. Noise interference from aftermarket bolt on parts.
2. The harmonic frequency of the rotating/reciprocating parts.

Both things will trigger false knock counts. Let's say the rockers are loud. Then you desensitize the pcm's response to the false knock. Many people consider any registered knock counts (after that) as true detonation. When in fact, it's just a resonance of the offending part. In this case the rocker arms.

Knock sensors are designed to send a signal when a certain frequency is reached. Changing any rotating/reciprocating part will alter the harmonic frequency of an engine. Thus changing the harmonic frequency of detonation. In turn, making the knock sensors useless.


For the record, You must have front o2's ONLY if the vehicle has catalytic converters.

slow

iTrader: (7)

My statement is still factual.

your still making a compromise with locked timing, for a race car, where consistancy is more important than optimal/safe power, it is an acceptable method of acheiving the desired goal.

Ryan

KVU

iTrader: (1)

The timing is not locked out due to a compromise. That is what the engine likes/wants. The IAT is actually remove FOR consistancy, not to throw safety out the window for a few extra ponies...

ChrisS@sdpc

I was under the impression that the front O2 sensors monitored A/F ratios to provide feedback to the PCM for Closed Loop fueling.
PCM uses data from the O2 sensors to establish both Short-term and Long-term fuel trims in an effort to maintain an injector pulsewidth that will create an A/F ratio being commanded. In Closed Loop operation with a stock PCM, this desired A/F ratio is 14.7:1 which creates the minimal amount of harmful emissions.

I thought a lot of people ran front O2's for this purpose regardless of whether or not they were running cats. I could be mistaken though.

shoemike

iTrader: (25)

fronts are for stoich commanded AFR.
you delete them by disabling closed loop fueling.(open loop)
as far as disabling knock sensors, that is not necessary in most cases.

ChrisS@sdpc

Yes, you could "tune them out". Do you own a tuning product? It is unlikely that your current tune was setup to operate the engine without the front O2's. As a result, it will most likely make your car run rich or lean. It is too difficult to tell which way. Wheter or not the car will run "weird" is unknown. It is certainly possible that the engine may be so rich that it will puff black smoke and sputter, or be so lean that you more easily experience knock or a misfire.

Depending on where you live, you may need them for inspection purposes.

KVU

iTrader: (1)

You are right, a lot of people do run the front O2's to monitor and adjust AFR. Here is the deal. Stoichiometric is the AFR required for proper catalyst operation. That is why the factory O2's are designed to operate @ that exact AFR. Removing the front O2's while keeping the cats will change the average AFR from 14.7, regardless of how well the tune is. This will kill the cats. Higher than 14.7 will burn em up while lower than 14.7 will clog them.

The biggest problem I have found (w/ CL operation) is camshaft reversion. This means AFR via wideband is skewed anywhere there is a large amount of overlap. Most of the time the problem lies at idle. Running CL with a big cam CAN result in a rich condition the wideband cannot sense.
..at any rate, vehicles do not run optimum at 14.7 . For example,light load/cruse situations at 15.5ish will net the best MPG. Depending on the cam, 16.0 might net the smoothest idle. You cannot do this type of programming in closed loop. Hope this answers any questions you might have....

ChrisS@sdpc

I was sort of half-joking with the "I might be mistaken" comment. I shouldn't be a smart-***. I dind't mean to offend.

I don't have any questions as it relates to the purpose of the front O2's. I've been around for a little while.

I think you might be confusing some people with your posts though.

I never said stoich was "optimal", but I did say that it produces the least amount of emissions. There is a lot of documentation out there regarding this.

BTW, a lot of research that is going on in the automotive industry involves cats. I spent about a week at MIT a year or so ago, and most of the tests in the lab involved cats. Generally speaking, other constituents in the exhaust stream are much more likely to kill the cats than a lean or rich condition. This is one of the main reasons that the composition of standard motor oil has changed in recent years, but that is an entirely different discussion. I was also under the impression that most 3-way catalytic converters worked better with slightly lean input. I could be mistaken though.

Not too many people on this board remove their front O2's and keep their cats. Most people willing to remove their front O2's don't care too much about the effects, probably do their own tuning, etc. i.e. they are fairly hard-core about it.

Now, there are quite a few people that have added exhaust systems in which they have removed their cats but keep their front O2's. Several of the sponsors sell off-road setups (wink wink).

The original question was "can I tune out my front O2's?" For most people here (95%+), this is not a realistic option for a whole list of reasons.

Of course, Ban1dit could simply go unplug his front O2's. I am willing to bet the outcome will be less than 'optimal'.

gametech

iTrader: (1)

If you run SD, the IAT is absolutely necessary, unless you plan to retune everyday (or several times a day). The ONLY way that isn't true is if you don't mind random AFR fluctuations with every temperature swing.
BTW, slow is absolutely right about locked out timing being a compromise. There is no such thing as a single timing value "that the motor likes" across all rpm and throttle values. The reason for this compromise generally involves eliminating excess moving parts and other variables in a race only motor.

ChrisS@sdpc

Come on, it's just temperature. Just chunk your MAP sensor too and go Alpha-N.

gametech

iTrader: (1)

I also own a motorcycle. Don't get me started on the evils of open loop alpha-n.

KVU

iTrader: (1)

yeah....I don't think alpha-n rings a bell for many folks here. While in fact, I have logged over 140,000 mile using alpha-n with my 305 tpi car. Hope to have a tech article about my experiences (for TGO/diy-prom) soon.

You are on the TGO boards , right? SDPC is a great moniker to be associated with! Not trying to school you, but share my personal experience. I have tuned everything from stock car cavi's to built sy/ty's..