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Discussion Starter · #1 ·
Hello,

I got my Y-pipe replacement pipes made up, and I was thinking about something. If the PCM does not get input from the upstream 02 sensors, it kicks the MIL on and goes into open loop. How much richer is the open loop than normal? I have holes in the front of my airbox, and if I were to run a K&N Pannel filter, or even a civic style intake, would that be enough air flow to counteract the "preset rich" condition? Do I make any sense to anyone? I realy dont have the money right now in my racing fund to get a chip, with lettering and painting the car coming up real soon.


Just me thinking,


Thanks for the help guys,


Brandon
 

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In short....No. Your Mass Air Meter will just read the new incoming air supply and adjust the computer accordingly, which would put you right back to the point that you're at now.
 

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Discussion Starter · #5 ·
So If I were to put an intake tube on my car, it would be best to run the upstream 02 sensors? I'm just looking to get a little more throttle response, and a filter I can clean after each night of racing. Even though I'm sure it would give a hp or 2, I wont see the 100+ HP that CAI's give ricers :p

Just curious, did any of my post make sense to you guys, or am I way out in left feild on this subject?

Thanks again for the info guys,

Brandon
 

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BLittle500 said:
So If I were to put an intake tube on my car, it would be best to run the upstream 02 sensors? I'm just looking to get a little more throttle response, and a filter I can clean after each night of racing. Even though I'm sure it would give a hp or 2, I wont see the 100+ HP that CAI's give ricers :p

Just curious, did any of my post make sense to you guys, or am I way out in left feild on this subject?

Thanks again for the info guys,

Brandon
just get a good tune that will turn off the rear o2s and put on the PI manifold.

you need the upstream o2s, they actually read the air/fuel ratio.
 

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Discussion Starter · #7 ·
I wish I could get a chip and a PI intake (swap would be nicer, explorer motor would be awsome), but it just isnt in my budget right now. As far as shutting the rears off, from what I understand they will only turn the light on, which is no biggie to me. I just thought if the fronts werent hooked up then the PCM had no info to go off of, then it would have to run the car off of a pre-set "map" which would be richer for engine saftey. Then with it purposly runing the car rich, and having no way of actualy telling if it rich or lean, If I put more air flow to it, it would put it about stoich.....Just my thinking, but I guess I was wrong again.


Thanks again,

Brandon
 

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In open loop mode your car reads the voltage sent to the computer from the maf and the throttle position sensor.

Just for example, if you have a grid type graph where the column data is the maf readings and the row data would be the throttle position reading. If say you were at half throttle you would follow the chart to where the row and column meet for where your voltage on the throttle position sensor and the air coming into the engine would meet and have a set value of time for the injectors to be open. This is where you get your "rich" mixture. Having the O2 sensors connected would in reality add a correction factor to this grid to have the car run at the correct air/fuel.

As it is, without running the O2's you would need to change something from the maf back in the air flow pattern or correct the voltage being sent by the tps to fake out the computer.

Some things to play with would be the tube diameter on the maf to make it read "less" air at the same flow you have now. Another would be to drill out the holes on the tps and rotate it enough to change your voltage at a given rotation. Those are the cheapest ways of playing with it I can think of.
 

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BLittle500 said:
If I put more air flow to it, it would put it about stoich.....Just my thinking, but I guess I was wrong again.

yup, thats where you're wrong, which is why i said you cannot change the A/F ratio arbitrarily at will....well to be added to that would be "and keep everything else the same".....you can fool the EEC by using sampling tubes to lean out the A/F ratio and what not, but then engine load is calculated incorrectly (due to sampling tubes at the maf).....A/F ratio and spark values primarily use engine load as a parameter (which would be incorrect), so you'd be going off base even further in your quest

the answer: put the upstream o2's back in :)
 

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You would be better off to just get a couple O2 sensor bungs welded into the pipe and run the front O2s still. The rears being off will not make any difference for performance and throttle response cause they just check whether the cats are there or not, but the fronts are used to calculate air/fuel ratio so you should keep those ones. On the other hand, when you are at WOT, the computer ignores the O2 sensors completely cause they can't respond fast enough, so you won't lose any power from them not being there, but your part throttle response certainly won't be improved by not having them, and for the $10 it would probably cost to have a couple bungs welded in, I would keep the front O2s working properly.

Mike
 

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Discussion Starter · #11 ·
Alrighty guys, I'm going to go ahead and put the upstream 02's back in. Thanks for all the great info, and your time weeding through my ideas!


Thanks again,

Brandon
 

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the only way you can really cheat the ecu for free is messing with the MAF. If you make the sample tube bigger the computer will think there is more air being consumed and add more fuel. WOT is preprogramed thou so it woulnt work there. I just bell mouthed the sample tube on my stock MAF and it made a huge difference
 

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twin turbo 281 said:
the only way you can really cheat the ecu for free is messing with the MAF. If you make the sample tube bigger the computer will think there is more air being consumed and add more fuel. WOT is preprogramed thou so it woulnt work there. I just bell mouthed the sample tube on my stock MAF and it made a huge difference

screwing with the sampling tube on an EEC5 car is one of the worst things you can do.
 
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