O2 sensors and leaded gas - PeachParts Mercedes-Benz Forum

Emmerich · #1 05-29-2007, 10:27 AM

It is my understanding lead will gum up an O2 sensor. Is there a device that accomplishes the same thing that is not affected by lead? I was going to plumb up a couple of cheapo O2 sensors in my 6.3 to measure the voltage (mixture) as a por boy method requiring the addition of the bung holes in the down tubes. I have access to leaded gas which I plan to mix with premium unleaded to get to an octane of about 96 for my hot summer driving.

PaulC · #2 05-29-2007, 10:43 AM

What are you trying to accomplish? To create some type of knock sensor? Are you trying to ensure that you won't run too lean in hot weather?

Emmerich · #3 05-29-2007, 11:40 AM

You measure the voltage coming off the sensor, this will tell you the CO mixture. A knock sensor is a sonic sensor that literally "listens" for the sound of knocking and retards timing as needed. The 6.3 has no sensors like that at all. The FI pump is adjusted and it stays that way until it becomes out of whack or until you adjust it differently.

PaulC · #4 05-29-2007, 11:43 AM

Right.

OMEGAMAN · #5 05-30-2007, 10:55 AM

MAybe tou can run 104 octane boost and unleaded gasoline. That way you wont hurt the O2 sensors and wont ping either.

300EVIL · #6 05-30-2007, 12:04 PM

Go by exhaust gas temperature. You can pickup an EGT gauge and probe on ebay for around $50-$100. It won't be as accurate and fast as an O2 sensor but it will keep you from burning anything up.

Also, I'm pretty sure they don't sell leaded gas anymore so I'm assuming your adding a lead substitute. I think some of them are O2 sensor safe, I may be wrong though.

Emmerich · #7 05-31-2007, 12:28 AM

Quote:

Originally Posted by 300EVIL

Go by exhaust gas temperature. You can pickup an EGT gauge and probe on ebay for around $50-$100. It won't be as accurate and fast as an O2 sensor but it will keep you from burning anything up.

Also, I'm pretty sure they don't sell leaded gas anymore so I'm assuming your adding a lead substitute. I think some of them are O2 sensor safe, I may be wrong though.

I have a jug of teraethyl lead but I'm afraid to touch it... octane boosts are not all that great, avgas is not good either, so race gas is the way to go. I have 118 leaded race gas.

Towel Rail · #8 05-31-2007, 02:50 AM

Is it actually overheating or are you just bored?

Emmerich · #9 05-31-2007, 09:51 AM

It is overheating and it is a custom race motor and unfortunately I don't have the specs on the components. We are trying to debug the heat issues right now. The car is a 914 with a 400HP Chevy 327 in it, and if it works here, I was going to plumb up the same thing in my 6.3. Should help for setting the mixture on the IP.

300EVIL · #10 05-31-2007, 10:19 AM

Ah, race gas. The pink stuff is leaded alright, 118 must be about $9 a gallon right now. Your problem maybe a 914 with 400HP..... Are you sure the radiator is big enough and is getting enough air? Any tiny production cars you see with massive power usually have to go through some drastic measures to configure the radiator to properly bleed off heat. Are you using an electric fan? Do you know the compression ratio of the engine? Do you have pictures of how the radiator is positioned?

Emmerich · #11 05-31-2007, 10:23 AM

We have it all plumbed up with a big fan, and fender cutouts in the front trunk. The engine is 11:1 and thats about all I know, except it has an agressive cam. We are looking at the water pump output now to see if there are restrictions in the system.

300EVIL · #12 05-31-2007, 10:46 AM

Yeah, That water pump was never designed to move water that far. I'd suggest going with a high output electric water pump. Something designed to be used on a 1000+ HP small block. This is what I use:

http://cgi.ebay.com/ebaymotors/CSR-water-pump-sbc-new_W0QQcmdZViewItemQQcategoryZ107063QQihZ003QQitemZ130119962336QQrdZ1 Get yourself a bottle of "Water Wetter" too. The stuff really is magic! Even with 11:1 and a big cam you should be able to use pump gas. Although, If your not drag racing the car you may want to consider switching to a lighter cam. Example: If you pull into a gas station and everyone turns around to see what just pulled in, you have too big of a cam for the street!

Fender cutouts may not be enough. Engineers spend countless hours debugging overheating problems when designing a car. I'd look at differential pressure at idle and at speed to ensure your getting good flow. Is the airflow venting out the hood or underneath the car?

300EVIL · #13 05-31-2007, 10:59 AM

Here's a good example of the proper way.

Emmerich · #14 05-31-2007, 03:28 PM

The trunk is vented thru the wheel wells. My mechanic says he thinks we do not get enough airlfow at idle. I am worried the pump is not working properly, although a lot of guys use these conversions with a regular water pump. We are investigating the system to see if there are any flow restrictions. I had thought of adding an electric pump as well. I thought it would be nice to be able to manually switch on the fan and the water pump to cool the engine even when it was not running. I am not sure if I go electric if having the regular pump as well will work, or if it would be a restriction in the system.

The race gas is only $5.80/gallon.

300EVIL · #15 05-31-2007, 04:11 PM

The nice thing about an electric pump are it's capabilities are not limited to or governed by engine speed. I think you would do just fine with one good electric pump and dumping the belt drive pump. As you can see, the pump I'm suggesting takes the place of the belt drive pump. If you go this way I'd suggest using a cheap micro controller to run the fan and pump based on coolant temp. That would be a really slick setup as well as efficient.

$5.80 a gallon! Man, you guys get it cheap down there!