O2 Sensor on Aspire

[boydg1]

.... Can I eliminate the O2 sensor on an Aspire (EFI) easier than replacing the carburetor on an Festie 88 or 89, with a Weber 32/36 DFEV carburetor?
If so, how would I go about it??

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[ericsmith32]

Which one? Sorta on the rear and no on the front one. Well unless you pull all the efi stuff and go carb'ed.

[TominMO]

Yeah, the EFI needs the feedback of the front 02 at least. 1994 and 95 Aspires only had the front 02 sensor, mounted on the exhaust manifold. In 1996 we got OBD-II, and the sensor back on the cat.

[htchbck]

ummm... I'll be the first to ask... why? ? ?

[bhazard]

Obd-1 doesn't require an o2 to run. You'll just be stuck in open loop.

[boydg1]

.... The less parts you have the more efficient motor you obtain. Not to mention the less cost involved and less headaches. With that said, I am NOT suggesting here something extreme just trying to be on the practical side of things and maybe stir some imagination.
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ummm... I'll be the first to ask... why? ? ?

[htchbck]

.... The less parts you have the more efficient motor you obtain.
.

Not true.

[boydg1]

.... Could you give us all a little more detail when you say "not true". Not trying to put you on the spot or anything like that, just trying to understand your point of view or your reasoning. :silent:
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Not true.

[htchbck]

Because on an EFI car the front O2 provides fuel trim data to the comp*. In fact by removing it you will actually lose efficiency. On festivas I've had a bad or disconnected O2 made the car run rich, not dumping fuel to the point where it ran badly, just wasting it little by little. I'm still not sure how you think eliminating the O2 will help with efficiency, but if you are dead set on doing it the simplest method would be unplug it. If you really want it out of there, remove the manifold, take the O2 out and either weld the hole shut or find a plug for it that is sized accordingly. Thats about all it takes to eliminate it, literally just take it out and fill the hole. How with that make you more efficient?... IDK... probably won't...

Only way I can see this making any sense to do would be if this is an OBD-II ('96+) car and you're wanting to do away with the one after the catalytic converter ('95 and earlier don't have that one) then you would need to get an O2 simulator so that the car *thinks* the cat is working right since it can't really know for sure without the sensor. Otherwise your check engine light will always stay on due to the emissions status not being verified. Removing the one after the cat probably would not adversely affect performance, since it is used mainly for emissions.

* I *could* be wrong about Festiva/Aspire engine management caring what the front O2 says, but I don't think I am and I know on many many other cars it plays a role in engine management. Also, there are many posts about people seeing better gas mileage after replacing their aging O2s (I've seen this in the past two months on two of my vehicles).

[Pu241]

I think you need look upon the O2 sensor as a critical component.
Up there with the water and fuel pump.
How do you see removing the O2 sensor as a step to higher efficiency?
Actually, if we had tighter control over the A/F ratio and controlled the exhaust temp to within reason of the materials, we could see a more efficient engine.

Given the cost of the festiva you can be sure they didn't include anything extra.

[htchbck]

Thank you John I felt like I was fighting a losing battle trying to explain it.

[boydg1]

.... I agree 100% with you and PU241 of POST#10 of this thread, as far as- things-are-today. What I am talking about is in the days BEFORE emission control when we did NOT have O2 sensor's but straight pipes with resonators and mufflers. As I recall, fuel injection and disc breaks were an invention of Europe and brought to the United States in time and I believe the Corvettes were one of the first to have fuel injection and possibly the disc breaks also. Back then we did NOT have computers like we do today. Consequently, they didn't have the control like they do today. I am suggesting we could do the same thing with an Aspire, similarly as with Festie's with the Weber 32/36 DFEV carburetors. What I don't know is if the onboard ASPIRE computer can run the fuel injectors in sync with the variation in RPM's. And if it can't, can it be modified or perhaps an E-prom could be burned to give the desired results? Or a separate computer unit all together which, most likely would involve another pickup sensor? All of these thoughts are just suggestions for debate here on this forum.

.

Because on an EFI car the front O2 provides fuel trim data to the comp*. In fact by removing it you will actually lose efficiency. On festivas I've had a bad or disconnected O2 made the car run rich, not dumping fuel to the point where it ran badly, just wasting it little by little. I'm still not sure how you think eliminating the O2 will help with efficiency, but if you are dead set on doing it the simplest method would be unplug it. If you really want it out of there, remove the manifold, take the O2 out and either weld the hole shut or find a plug for it that is sized accordingly. Thats about all it takes to eliminate it, literally just take it out and fill the hole. How with that make you more efficient?... IDK... probably won't...

Only way I can see this making any sense to do would be if this is an OBD-II ('96+) car and you're wanting to do away with the one after the catalytic converter ('95 and earlier don't have that one) then you would need to get an O2 simulator so that the car *thinks* the cat is working right since it can't really know for sure without the sensor. Otherwise your check engine light will always stay on due to the emissions status not being verified. Removing the one after the cat probably would not adversely affect performance, since it is used mainly for emissions.

* I *could* be wrong about Festiva/Aspire engine management caring what the front O2 says, but I don't think I am and I know on many many other cars it plays a role in engine management. Also, there are many posts about people seeing better gas mileage after replacing their aging O2s (I've seen this in the past two months on two of my vehicles).

[Pu241]

... I am suggesting we could do the same thing with an Aspire, similarly as with Festie's with the Weber 32/36 DFEV carburetors. What I don't know is if the onboard ASPIRE computer can run the fuel injectors in sync with the variation in RPM's. And if it can't, can it be modified or perhaps an E-prom could be burned to give the desired results? Or a separate computer unit all together which, most likely would involve another pickup sensor? All of these thoughts are just suggestions for debate here on this forum. .

OK, I followed you up to this point.
What is the "same thing we are trying to do"?
The fuel injection computer MUST run the injectors in sync with RPM variations, otherwise it will not work.
Maybe your trying to say something else, sorry I'm just not following.
If you want more control a Mega Squirt unit can be used, but is pricey.

[TominMO]

OK, I followed you up to this point.
What is the "same thing we are trying to do"?
The fuel injection computer MUST run the injectors in sync with RPM variations, otherwise it will not work.
Maybe your trying to say something else, sorry I'm just not following.
If you want more control a Mega Squirt unit can be used, but is pricey.

John, I notice your location(s) update. You're getting harder to track than Osama was!

[htchbck]

OK, I followed you up to this point.
What is the "same thing we are trying to do"?
The fuel injection computer MUST run the injectors in sync with RPM variations, otherwise it will not work.
Maybe your trying to say something else, sorry I'm just not following.
If you want more control a Mega Squirt unit can be used, but is pricey.

I'm not 100% percent on this but I'm starting to wonder if I misread his original post. Boyd were you trying to ask if it was possible to switch an Aspire over to carb and ditch the EFI altogether? If so you will likely lose fuel economy, but it could put some of the tune-ability of the engine back in your hands without installing an (expensive) megasquirt system. If you did this you would probably need a 88-93 B3 head as I don't think the Aspire ones have the proper hole for the mechanical fuel pump that a carb uses. Or perhaps just use a VERY low pressure inline electric pump, but either way you'll need to ditch the 40PSI+ in tank pump that the EFI uses as it will blow every seal in the carb most likely. Other than that should be pretty straight forward, get a carb intake, set it up to accept the weber (machining or adapter) and stick it on the motor. Once everything is hooked up and running you can start pulling off all the EFI stuff that is no longer hooked to anything. It would be interesting to see a carb'd Aspire, I bet kartracer would like it

Is that the plan?