O2 clamp unnecessary for EMU? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-07-2007, 02:09 AM   #1
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Default O2 clamp unnecessary for EMU?

me being stupid, i replied to a threat instead of posting a new one. anyways..

i know ive read this somewhere where it may NOT be needed, but it would like to verify. i also read somewhere that using the acceleration adjustment map did the job of a 02 clamp.

im sure it was on this forum before the great purge, but anyone can give me an insight please? thanks.
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Old 08-07-2007, 11:38 AM   #2
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Running an O2 sensor clamp is still a good idea even on an EMU. What you can do (and I have done) is to use the Aux Output of the EMU to control the clamp, which eliminates the need for an external pressure sensor and comparator, and ensures that the clamp switches at exactly the point that you want it to (in my case, the row in which A/F Target autotune turns on). This simplifies the design of the clamp to little more than a SPDT relay, a stable reference (I use an LM7805) and a couple of resistors.
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Old 08-08-2007, 07:13 AM   #3
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interesting..

thanks for the reply. ill see what i can do about getting it to run without the 02 clamp, hopefully no lean-tip-in will occur. if it does, ill work with the acceleration adjustment settings, but if it turns out to more of a hassle trying to play with the maps, i might as well get an 02 clamp

thanks for your reply.
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Old 08-11-2007, 03:37 PM   #4
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Hey Im unsure if i need a O2 clamp to be honest i do not know what the o2 clamp is and if i do need this thing how can i make it or where can i get it. Makeing it sounds better but if i have to buy it please some help on where to get one would be awsome. Im going to be running TDO5H with emanage and 300 injectors.
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Old 08-12-2007, 12:29 PM   #5
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Originally Posted by Dewalt View Post
Hey Im unsure if i need a O2 clamp to be honest i do not know what the o2 clamp is and if i do need this thing how can i make it or where can i get it. Makeing it sounds better but if i have to buy it please some help on where to get one would be awsome.
Grammar... and... punctuation...

Ok, seriously. Do some reading on Engine Management 101. Understand the function of the O2 sensor and its relationship to open-loop and closed-loop operational modes on the ECU.

When you turbocharge and engine and add fuel management, We are creating a situation whereby the engine is going to run rich when in boost. Normally, when we are in boost we are drawing so much air that the stock ECU is looking at a load cell that puts it into open-loop operation, so it is somewhat blind to the alterations that we are making downstream of it.

Certain conditions exist however when we may be in boost and yet the ECU is running closed-loop. This occurs at low levels of boost (particularly at low RPM) and also at the point where we are just transitioning into boost. During these periods, the ECU is going to see from the O2 sensor that the mixture is rich, and pull fuel to "correct" the situation.

An O2 sensor clamp is a circuit that interrupts the feed from the O2 sensor to the ECU and replaces it with a fixed voltage that emulates a slightly lean reading. The circuit is switched in whenever you are in boost, either via a simple pressure switch or by a comparator driven by a MAP sensor. The idea is to prevent the ECU from seeing that the mixture has gone rich and from then trying to cut back on the fuel, fighting us as we try to add more in.
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Old 08-19-2007, 01:26 PM   #6
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Originally Posted by Joe Perez View Post
Grammar... and... punctuation...

Ok, seriously. Do some reading on Engine Management 101. Understand the function of the O2 sensor and its relationship to open-loop and closed-loop operational modes on the ECU.

When you turbocharge and engine and add fuel management, We are creating a situation whereby the engine is going to run rich when in boost. Normally, when we are in boost we are drawing so much air that the stock ECU is looking at a load cell that puts it into open-loop operation, so it is somewhat blind to the alterations that we are making downstream of it.

Certain conditions exist however when we may be in boost and yet the ECU is running closed-loop. This occurs at low levels of boost (particularly at low RPM) and also at the point where we are just transitioning into boost. During these periods, the ECU is going to see from the O2 sensor that the mixture is rich, and pull fuel to "correct" the situation.

An O2 sensor clamp is a circuit that interrupts the feed from the O2 sensor to the ECU and replaces it with a fixed voltage that emulates a slightly lean reading. The circuit is switched in whenever you are in boost, either via a simple pressure switch or by a comparator driven by a MAP sensor. The idea is to prevent the ECU from seeing that the mixture has gone rich and from then trying to cut back on the fuel, fighting us as we try to add more in.
Is this the reason why my car is very lean on idle?

Last edited by MX5Kuro; 08-19-2007 at 04:43 PM.
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Old 08-19-2007, 07:18 PM   #7
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Originally Posted by MX5Kuro View Post
Is this the reason why my car is very lean on idle?
No
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Old 08-20-2007, 12:20 PM   #8
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Originally Posted by MX5Kuro View Post
Is this the reason why my car is very lean on idle?
Not at all. The O2 sensor clamp is designed to correct a potential lean condition in boost. Its only function is to prevent the stock ECU from detecting the rich condition that results when an AFPR or Piggyback performs fuel addition.

What leads you to conclude that you are lean at idle?
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Old 08-20-2007, 12:30 PM   #9
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hey guys, im still confused about this, if i run a greddy pressure sensor with the emu will i need the clamp or can i just adjust the maps to suit the lean out that the ecu is trying to send out?
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Old 08-20-2007, 01:25 PM   #10
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Originally Posted by Joe Perez View Post
Not at all. The O2 sensor clamp is designed to correct a potential lean condition in boost. Its only function is to prevent the stock ECU from detecting the rich condition that results when an AFPR or Piggyback performs fuel addition.

What leads you to conclude that you are lean at idle?
AFR hits 20 on idle, car is running hot and won't start until it's cooled down.
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Old 08-20-2007, 05:35 PM   #11
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Disconnect the heater wires to your 4 wire O2 sensor and see what signal the O2 is getting to the ECU
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Old 08-24-2007, 04:37 AM   #12
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Originally Posted by MX5Kuro View Post
AFR hits 20 on idle, car is running hot and won't start until it's cooled down.
Uhhh, check your injector settings first!

btw, you can give me a call over here in germany if you still have problems

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Old 08-24-2007, 01:14 PM   #13
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Uhhh, check your injector settings first!

btw, you can give me a call over here in germany if you still have problems

Falk
I adjusted the size in the parameters from 280 stock to 550cc now. But I think it might be the EGR removal. I blocked the EGR because my manifold doesn't have a EGR port (HKS). So I think the ECU thinks the airtemp is higher than ik actual is. So the mixture gets leaner than it is supposed to be.

I hope it can be compensated by the EMU.
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