Disconnecting O2 Sensor
01-06-2004, 11:41 AM
#1
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Thread Starter
Disconnecting O2 Sensor
My 3.6 V-ram conversion utilizes only one O2 sensor. I know that disconnecting the sensor will cause a rich "safety" condition. For track and hi-temp high rpm driving, is there an advantage to running in this enriched mode?
Probably a stupid question, but that never stopped me before
.
Thanks,
Probably a stupid question, but that never stopped me before
.Thanks,
01-06-2004, 01:10 PM
#2
The O2 system (Lambda controlled) optimizes the fuel mixture to achieve
an air to fuel ratio of 14.7. This point (Lambda = 1.0) is ideal for emissions
control. Maximum torque occurs at an air to fuel ratio less than 14.7, i.e.
Lambda less than 1.0.
So, by disconnecting your O2 sensor and adjusting the mixture with your
air flow meter, assuming it hasn't been changed to an air mass sensor,
you can gain a little extra torque. Set the mixture for a CO of 1.5% before
the CAT at 2000 RPMs. Avoid a too rich mixture, as the CAT may have a
shorten life.
Check out this website (www.systemsc.com) on the Graphs page for some
additional info.
Good Luck
Loren
'88 3.2
an air to fuel ratio of 14.7. This point (Lambda = 1.0) is ideal for emissions
control. Maximum torque occurs at an air to fuel ratio less than 14.7, i.e.
Lambda less than 1.0.
So, by disconnecting your O2 sensor and adjusting the mixture with your
air flow meter, assuming it hasn't been changed to an air mass sensor,
you can gain a little extra torque. Set the mixture for a CO of 1.5% before
the CAT at 2000 RPMs. Avoid a too rich mixture, as the CAT may have a
shorten life.
Check out this website (www.systemsc.com) on the Graphs page for some
additional info.
Good Luck
Loren
'88 3.2
01-06-2004, 01:24 PM
#3
Does anybody have the link to O2 "simulator" used on the 2nd O2 sensor when you have cat bypasses installed?
This device simulates a variance in the 2nd O2 sensor to prevent the CE light.
This device simulates a variance in the 2nd O2 sensor to prevent the CE light.
01-06-2004, 01:29 PM
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Jeff,
When I installed the Cat bypass, my CE light came on at 100 miles after the change, then I turned it off. 100 miles later, it came on again. After turning it off the second time, it has not come back on. I assume that the '96 ECU has the same learning algorithm as the '97 that stop setting a CE condition for the same fault after resetting it a couple of times.
It is either that, or my ECU just gave up because it knew it could not win with the onslaught of mods coming at it...
When I installed the Cat bypass, my CE light came on at 100 miles after the change, then I turned it off. 100 miles later, it came on again. After turning it off the second time, it has not come back on. I assume that the '96 ECU has the same learning algorithm as the '97 that stop setting a CE condition for the same fault after resetting it a couple of times.
It is either that, or my ECU just gave up because it knew it could not win with the onslaught of mods coming at it...
01-06-2004, 02:54 PM
#5
Instructor
Thread Starter
Loren,
Thanks! Note that there is no cat installed (custom exhaust with stock heat exchangers). Didn't realize that the AFM was adjustable. Hmmm.
Using a Cyntex Performance Tuning chip now and getting pretty good results (although I am aware of your position on aftermarket chips...I don't have a stock one...any reason to get one?). DME is a 96 Euro OBD1 box (part # 993-618-124.11). Recent dyno run indicated a range between 15.5:1 (low rpm WOT)and 13:1 (high rpm WOT). But...sniffer was a probe in the exhaust pipe, so I'm guessing that a reading right off of the HE would yield more accurate results (richer). Do you agree with this assumption? Plugs look like new with only a slight yellowing to the ceramic. Was concerned about being too lean but plugs and performance don't indicate as much (268 rwhp/245 tq).
Thanks again,
Thanks! Note that there is no cat installed (custom exhaust with stock heat exchangers). Didn't realize that the AFM was adjustable. Hmmm.
Using a Cyntex Performance Tuning chip now and getting pretty good results (although I am aware of your position on aftermarket chips...I don't have a stock one...any reason to get one?). DME is a 96 Euro OBD1 box (part # 993-618-124.11). Recent dyno run indicated a range between 15.5:1 (low rpm WOT)and 13:1 (high rpm WOT). But...sniffer was a probe in the exhaust pipe, so I'm guessing that a reading right off of the HE would yield more accurate results (richer). Do you agree with this assumption? Plugs look like new with only a slight yellowing to the ceramic. Was concerned about being too lean but plugs and performance don't indicate as much (268 rwhp/245 tq).
Thanks again,
01-06-2004, 03:45 PM
#6
Being on the rich side is always better, and it sounds as if you're on the lean
side.
First, check the CO at 2000 RPMs. Then loosen the spring in the AFM to richen
the mixture and check the CO, no more than two clicks at a time to get to a
CO of 1.5%.
Then run on the dyno, again.
Good Luck
Loren
'88 3.2
side.
First, check the CO at 2000 RPMs. Then loosen the spring in the AFM to richen
the mixture and check the CO, no more than two clicks at a time to get to a
CO of 1.5%.
Then run on the dyno, again.
Good Luck
Loren
'88 3.2
01-06-2004, 04:42 PM
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Originally posted by Jeff 993TT
Does anybody have the link to O2 "simulator" used on the 2nd O2 sensor when you have cat bypasses installed?
This device simulates a variance in the 2nd O2 sensor to prevent the CE light.
Does anybody have the link to O2 "simulator" used on the 2nd O2 sensor when you have cat bypasses installed?
This device simulates a variance in the 2nd O2 sensor to prevent the CE light.
Airpump test bypass circuit
Chip
Last edited by 914und993; 01-07-2004 at 06:58 PM.
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01-06-2004, 08:23 PM
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Hey Mike,
Good move on getting the Euro model V-RAM engine (or is it just the DME?) with only 1 O2 sensor. Positioning the 4 O2 sensors around my single 964 cat. so they were "happy" was one of the most challenging parts of the conversion. (We may have discussed this before your conversion, don't remember?)
Do you have the stock 3.2L or stock 3.6L heat exchangers on your car? Just curious.
Good move on getting the Euro model V-RAM engine (or is it just the DME?) with only 1 O2 sensor. Positioning the 4 O2 sensors around my single 964 cat. so they were "happy" was one of the most challenging parts of the conversion. (We may have discussed this before your conversion, don't remember?)
Do you have the stock 3.2L or stock 3.6L heat exchangers on your car? Just curious.
01-06-2004, 09:17 PM
#9
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Thread Starter
Randall,
Good to hear from you...it's been a while. I haven't lurked here much since I sold my 964. I bought my 89 about 18 months ago and completed the engine swap around Thanksgiving. I decided that doing a 3.6 swap was going to cost a fortune anyway, so why not spend a few extra bucks for Vram?...glad I did. I've got a US engine from a 97 model 993 with a Euro OBD1 DME. I sold the 3.2 before it was even out of the car. Went very smooth.
Engine has stock 993 heat exchangers. I had an exhaust system custom made because the cat-only solution was so blaring loud I couldn't hear myself think! No room in the fender wells for 993 mufflers (oil tank).
Interesting that you swapped a 3.6 964 motor for a 993 version. Was your old engine problematic, or was it just the passion for more power? Looks like you've got a 993 gearbox too....very nice. Interested in learning about your AC setup. Condensor in the rear fender?
Good to hear from you...it's been a while. I haven't lurked here much since I sold my 964. I bought my 89 about 18 months ago and completed the engine swap around Thanksgiving. I decided that doing a 3.6 swap was going to cost a fortune anyway, so why not spend a few extra bucks for Vram?...glad I did. I've got a US engine from a 97 model 993 with a Euro OBD1 DME. I sold the 3.2 before it was even out of the car. Went very smooth.
Engine has stock 993 heat exchangers. I had an exhaust system custom made because the cat-only solution was so blaring loud I couldn't hear myself think! No room in the fender wells for 993 mufflers (oil tank).
Interesting that you swapped a 3.6 964 motor for a 993 version. Was your old engine problematic, or was it just the passion for more power? Looks like you've got a 993 gearbox too....very nice. Interested in learning about your AC setup. Condensor in the rear fender?
01-06-2004, 11:46 PM
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Hey Mike,
Sounds like you now have the ultimate '89 Targa.
First I've heard of using a Euro DME for a 993 VRAM conversion, but it makes sense. Especially having to deal with only 1 O2 sensor. Surely would have been a better route for me, if I was aware of the option. Too late now. I do have to worry about smog, but think I still could pass with a single O2 sensor and cat. At least at the '91 limit.
Did you find out about the Euro DME option yourself, or was it your installer who suggested it?
Do you have heat in your 911? With the 993 heat exchangers, they have to perform somewhat substantial mods to match up to your 911's heating system. And, you know about getting mufflers to fit in a pre-993 narrow body.
When I investigated installing the 993 exhaust system in my own car, I was warned of how loud they run with cats only. Not enough room in the 964's rear fenders for 993 mufflers, also. Unless you're Kevin in the Northwest, and a few others, who have managed to make 'em fit somehow (not an easy job).
On my own car, we (myself and Hergesheimer's) stuck with the 964's exhaust, avoiding the major headache of converting the 993's exhaust system to fit. But, it left us dealing with the 4 O2 sensors around a single cat. The issue was eventually sorted, but was quite a challenge. In retrospect, the 993 exhaust system conversion may not have been any more trouble. The whole O2 thing would have been a non-issue if we were only dealing with 1 of 'em. The problem with two sensors on one cat inlet is getting their readings to match (close enough)--if not, the car starts to run like a turd, and only gets worse.
My original engine spun a rod bearing at 100k miles. I opted for a used 993 engine instead of fixing my own engine. Thought it would be straightforward swap (3.6L for 3.6L), but it wasn't. But, happy with what I have now. As you've already noticed, I had the 6-speed installed at the same time.
>Interested in learning about your AC setup. condenser in the rear fender?
My, you have been away from 964s for awhile. In fact, it was you who replaced the condenser fan resistor in your 964, left-front fender. Which is where my condenser is. LOL! I believe you're thinking of the Kuehl condenser which fits in the rear fender. Typically a pre-964 upgrade, as far as I know.
Good talking with you!
Sounds like you now have the ultimate '89 Targa.
First I've heard of using a Euro DME for a 993 VRAM conversion, but it makes sense. Especially having to deal with only 1 O2 sensor. Surely would have been a better route for me, if I was aware of the option. Too late now. I do have to worry about smog, but think I still could pass with a single O2 sensor and cat. At least at the '91 limit.
Did you find out about the Euro DME option yourself, or was it your installer who suggested it?
Do you have heat in your 911? With the 993 heat exchangers, they have to perform somewhat substantial mods to match up to your 911's heating system. And, you know about getting mufflers to fit in a pre-993 narrow body.
When I investigated installing the 993 exhaust system in my own car, I was warned of how loud they run with cats only. Not enough room in the 964's rear fenders for 993 mufflers, also. Unless you're Kevin in the Northwest, and a few others, who have managed to make 'em fit somehow (not an easy job).
On my own car, we (myself and Hergesheimer's) stuck with the 964's exhaust, avoiding the major headache of converting the 993's exhaust system to fit. But, it left us dealing with the 4 O2 sensors around a single cat. The issue was eventually sorted, but was quite a challenge. In retrospect, the 993 exhaust system conversion may not have been any more trouble. The whole O2 thing would have been a non-issue if we were only dealing with 1 of 'em. The problem with two sensors on one cat inlet is getting their readings to match (close enough)--if not, the car starts to run like a turd, and only gets worse.
My original engine spun a rod bearing at 100k miles. I opted for a used 993 engine instead of fixing my own engine. Thought it would be straightforward swap (3.6L for 3.6L), but it wasn't. But, happy with what I have now. As you've already noticed, I had the 6-speed installed at the same time.
>Interested in learning about your AC setup. condenser in the rear fender?
My, you have been away from 964s for awhile. In fact, it was you who replaced the condenser fan resistor in your 964, left-front fender. Which is where my condenser is. LOL! I believe you're thinking of the Kuehl condenser which fits in the rear fender. Typically a pre-964 upgrade, as far as I know.
Good talking with you!
01-07-2004, 12:28 AM
#11
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Thread Starter
They say the memory is the second thing to go! I hope that's not really true.
I bought my engine with all conversion parts and DME from Steve Timmins at www.instant-g.com. He gets credit for coming up with that combo.
Yes, I have heat...just installed some 993 rubber diverters and some hi temp hoses to the 993 HE's...actually it wasn't that bad. I ditched the blower fan though in favor of a carbon fiber heat tube. So, my heat is backdated to 70's style...the faster I go, the more heat I get. Not a problem here in Georgia...actually it works pretty well.
Have you dyno'd your car? I'll bet you love that tranny.
Best,
I bought my engine with all conversion parts and DME from Steve Timmins at www.instant-g.com. He gets credit for coming up with that combo.
Yes, I have heat...just installed some 993 rubber diverters and some hi temp hoses to the 993 HE's...actually it wasn't that bad. I ditched the blower fan though in favor of a carbon fiber heat tube. So, my heat is backdated to 70's style...the faster I go, the more heat I get. Not a problem here in Georgia...actually it works pretty well.
Have you dyno'd your car? I'll bet you love that tranny.
Best,
01-07-2004, 12:45 AM
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Ah, Steve Timmins. Mr. 993 engine conversion. That's who I would have expected to think of using the Euro DME. My installation was performed without Steve's help, but I'm well aware of his website and reputation.
Haven't dynoed my car. I sometimes think about installing GHL's dual cat-headers for 964s. Which I would have installed in the first place, but they hit the market after my install. But, the car is sorted and runs great as-is, and I'm not motivated enough to deal with another exhaust installation. That, and I'm too cheap (about $2500, give or take).
Back in '02, passed my 15k service point....with little more than an oil change. That was nice, not having to deal with/pay for a valve adjustment. I'm now just over 25k miles on the 993 engine/trans install, put on over a period of about 3.5 years.
Your engine is looking good.
Haven't dynoed my car. I sometimes think about installing GHL's dual cat-headers for 964s. Which I would have installed in the first place, but they hit the market after my install. But, the car is sorted and runs great as-is, and I'm not motivated enough to deal with another exhaust installation. That, and I'm too cheap (about $2500, give or take).
Back in '02, passed my 15k service point....with little more than an oil change. That was nice, not having to deal with/pay for a valve adjustment. I'm now just over 25k miles on the 993 engine/trans install, put on over a period of about 3.5 years.
Your engine is looking good.
01-07-2004, 08:56 AM
#14
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Randall,
Guess we could take this off-line but there may info here that's useful to others. Where did you get your engine? Was it new (you mention 15k service interval)? Knowing Timmins reputation could mean anything. Overall he's been very helpful and puts out a good product, just a bit cantakerous if you catch him at the wrong time. He's got a real job too, (professor at Univ of Deleware), so that might explain it. Happy with the outcome over all.
What are you doing for oil cooling? Refresh my memory, what is the stock cooler on a 964 (I remember that it's in the front fender like mine...is there another one too?). I guess if it works for the 964 motor it's fine for the 993? Reason I ask is I added a small aux cooler (that's all that would fit in the other front fender), and around town temps are fine, but in traffic, etc., they creep up. Will be installing a switchable cooling fan on the remote cooler this weekend....here we go again.
Here's my plan (and I know you're the person to ask)...I plan to remove my fog lights and replace them with screens to get more air through the coolers. I plan to use the foglight wiring for the left light to get power and ground for the fan. This way, the circuit already goes through the foglight relay and I can utilize the foglight switch on the dash (seems cleaner that way). Sound like it'll work? Am I overlooking something?
Thanks again,
Guess we could take this off-line but there may info here that's useful to others. Where did you get your engine? Was it new (you mention 15k service interval)? Knowing Timmins reputation could mean anything. Overall he's been very helpful and puts out a good product, just a bit cantakerous if you catch him at the wrong time. He's got a real job too, (professor at Univ of Deleware), so that might explain it. Happy with the outcome over all.
What are you doing for oil cooling? Refresh my memory, what is the stock cooler on a 964 (I remember that it's in the front fender like mine...is there another one too?). I guess if it works for the 964 motor it's fine for the 993? Reason I ask is I added a small aux cooler (that's all that would fit in the other front fender), and around town temps are fine, but in traffic, etc., they creep up. Will be installing a switchable cooling fan on the remote cooler this weekend....here we go again.
Here's my plan (and I know you're the person to ask)...I plan to remove my fog lights and replace them with screens to get more air through the coolers. I plan to use the foglight wiring for the left light to get power and ground for the fan. This way, the circuit already goes through the foglight relay and I can utilize the foglight switch on the dash (seems cleaner that way). Sound like it'll work? Am I overlooking something?
Thanks again,
01-07-2004, 11:01 AM
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Good mornin' Mike,
Dr. Timmins. Yes, I've heard of at least one person having a bad experience with his service. But, near as I can tell, he is the 3.6L (as opposed to just 993, as I wrote earlier) engine conversion guru. I'm sure many people pick his brain, then don't buy sh** from him. Which has to be very annoying. Anyway, I've heard way more positive than negative about him. And, his website is a great source of information.
My engine was used, a theft recovery. From a '97 993, stolen in 2/98, the engine being recovered by the CHP 6 months later. 20k miles when stolen. I bought the engine and transmission from TRE Motorsports in Hollywood. Dave B., the owner of TRE, bought the engine from a police auction--or an acquaintance did. Prior to installing the engine, it was checked out, new spark plugs installed, etc. So, my "15k miles" were relative to the engine being installed.
Yup, just using the stock oil cooler on the 964, which is really the same as the 993 (may be a different part number, haven't checked). The cooler is in the right-front fender. 964/993 engines don't have an engine mounted oil cooler (like your old 3.2L), so you've gots to have the external cooler. I'm pretty sure the Carrera uses an external oil cooler, but I kinda' doubt it's adequate for cooling a 3.6L engine.
Doesn't your existing external cooler in the right-front fender already have a fan? Perhaps all you need is to switch this fan, or set it up so it will run all the time (ignition on)?
Lots of people on this board have added an additional oil cooler to assist in cooling. Near as I can tell, this is only needed for track applications. On a 964/993, it's very easy to install a switch to start the oil cooler fan manually. You just place it inline on the wire from the oil cooler temperature sensor to the CCU. When you open the switch, the CCU reads infinite resistance, thinks there's a circuit failure, and starts the oil cooler fan in fast-speed by default. Nice and simple.
I'm not real familiar with Carrera wiring. That said, your idea of using the fog-light relay sounds like a good one. Assuming the fog-light wiring is adequate for the current the oil cooler fan will pull. On a 964, the fog-light fuse is only rated for 15A, while the oil cooler fan fuse is rated for 30A. You would need to check the gauge of wire used on the fog-light circuit, to make sure it's adequate. Or, find out what the current draw is for the fan you're planning to install. If you find the wires are of sufficient gauge, you may need to install a higher rated fuse, if the fan keeps blowing the 15A fuse (assuming your car also uses a 15A fuse).
Another interesting tidbit. On a 964, the back-up lights share the fog-light's fuse. Shouldn't make any difference for what you have in mind, though.
Even if the fan you're considering draws too much current, or the wires are too small, you could still get away with using the fog-light wiring by installing a (ack!) ballast resistor. Say, about 0.5 ohm. This will limit the current draw--but will also slow the fan considerably.
Is it possible to install a factory 964/993 cooler in your right-front fender, replacing the 3.2L stock unit? Not enough room? This should be more than adequate for everything except track use.
Well, that's all for now. Talk to ya' soon!
Dr. Timmins. Yes, I've heard of at least one person having a bad experience with his service. But, near as I can tell, he is the 3.6L (as opposed to just 993, as I wrote earlier) engine conversion guru. I'm sure many people pick his brain, then don't buy sh** from him. Which has to be very annoying. Anyway, I've heard way more positive than negative about him. And, his website is a great source of information.
My engine was used, a theft recovery. From a '97 993, stolen in 2/98, the engine being recovered by the CHP 6 months later. 20k miles when stolen. I bought the engine and transmission from TRE Motorsports in Hollywood. Dave B., the owner of TRE, bought the engine from a police auction--or an acquaintance did. Prior to installing the engine, it was checked out, new spark plugs installed, etc. So, my "15k miles" were relative to the engine being installed.
Yup, just using the stock oil cooler on the 964, which is really the same as the 993 (may be a different part number, haven't checked). The cooler is in the right-front fender. 964/993 engines don't have an engine mounted oil cooler (like your old 3.2L), so you've gots to have the external cooler. I'm pretty sure the Carrera uses an external oil cooler, but I kinda' doubt it's adequate for cooling a 3.6L engine.
Doesn't your existing external cooler in the right-front fender already have a fan? Perhaps all you need is to switch this fan, or set it up so it will run all the time (ignition on)?
Lots of people on this board have added an additional oil cooler to assist in cooling. Near as I can tell, this is only needed for track applications. On a 964/993, it's very easy to install a switch to start the oil cooler fan manually. You just place it inline on the wire from the oil cooler temperature sensor to the CCU. When you open the switch, the CCU reads infinite resistance, thinks there's a circuit failure, and starts the oil cooler fan in fast-speed by default. Nice and simple.
I'm not real familiar with Carrera wiring. That said, your idea of using the fog-light relay sounds like a good one. Assuming the fog-light wiring is adequate for the current the oil cooler fan will pull. On a 964, the fog-light fuse is only rated for 15A, while the oil cooler fan fuse is rated for 30A. You would need to check the gauge of wire used on the fog-light circuit, to make sure it's adequate. Or, find out what the current draw is for the fan you're planning to install. If you find the wires are of sufficient gauge, you may need to install a higher rated fuse, if the fan keeps blowing the 15A fuse (assuming your car also uses a 15A fuse).
Another interesting tidbit. On a 964, the back-up lights share the fog-light's fuse. Shouldn't make any difference for what you have in mind, though.
Even if the fan you're considering draws too much current, or the wires are too small, you could still get away with using the fog-light wiring by installing a (ack!) ballast resistor. Say, about 0.5 ohm. This will limit the current draw--but will also slow the fan considerably.
Is it possible to install a factory 964/993 cooler in your right-front fender, replacing the 3.2L stock unit? Not enough room? This should be more than adequate for everything except track use.
Well, that's all for now. Talk to ya' soon!