1G The truth about the exhaust ground strap?

[mrmadmax]

Originally posted by Awdboost
There are a few things you guys need to take into consideration about the gas mileage and ground strap theory.

-The O2 sensor have 4 wires and one of them if not 2 are grounds.
-I think people that get the 25-35 mpg claims are doing one or if not two of these things. Drive all highway miles. Use the factory gauge to guess how much there gas mileage is or just are bad at math skillz. (The proper way to do it is fill the car until the pump stops. Drive around for at least 150-200 miles but make sure you record how many mile you drove. Then fill up the car again and let the pump shut off once again. Take the mileage and divide it but the gallon at the pump that you have filled, and that will give you your gas mileage.) Or the laws of physic do not exists on your car alone. :laugh:

As was mentioned above, you are correct; two of them are grounds. One grounds the heater circuit, and the other provides the return signal to the ecm (basically a ground at the ecm).

I got 28.5 mpg (all highway, few mods) just last weekend using the exact method shown above. In a mix of mostly city and some highway, it's closer to 24. I seriously doubt that anyone is using their gas gauge to calculate mpg; I can't even think of how it would be done...

As for the ground strap, the problem is noise (electrical noise). As was mentioned, the O2 sensor works off of a small signal (0-1V). There is all kinds of elecrical noise present in the engine compartment from the coils, injectors, etc; and this noise can show up in the O2 signal as a bunch of tall narrow voltage spikes. Often these spikes can get higher than the signal from the O2 itself. Grounding the pipe tends to lessen the height of the spikes, which should eliminate the interference that they cause. You won't see this on all cars (I have personally tested dozens, though only mine was a DSM), and my guess is that the ones that lack the noise do so because the manifold hasn't rusted enough to break down the electical connection at the head--yet.

 

[Smoothie97]

Hmm..ok so I need to get a hose clamp and wrap the ground strap around my Apex downpipe. Does not having the strap grounded affect my emissions? Because I'm getting tons of white smoke right now and I don't think I have any leaks. I wouldn't think that grounding it would make a difference because since I have no cat, the rear O2 sensor is reading crappy dirty exhaust anyway.

 

[MaNGiNa24]

Originally posted by jdmawd



the 3" buschur down pipe has has the threaded section for the o2 ground

I have the 3" buschur awd downpipe for a 2g and I don't see any threads? I just slipped the ground in between the exhaust mount and the rubber hanger, that worked fine. What do you guys consider bad gas mileage? I'm getting about 250 to the tank with the 3 inch catless turbo back, how bout everyone else?

 

[jim97gst]

When I put my exhaust on, I removed the ground strap bacause at the time I didn't know where to put it. Gas mileage seems to be fine (~26-30 mpg). However, I have a metal exhaust hanger welded on to the rear part of the exhaust and bolted to the rear cross member (no rubber in between). Will that accomplish the same thing as the ground strap? Is it important that the exhaust piping is grounded to the frame, or that whatever that ground strap is attached to under the car is grounded to the exhaust? Thanks.

 

[Benji]

What if you don't have it anymore? What should I replace it with?

 

[THEDUKE]

I would put a strap from the down pipe to the frame just so there is no problem with interferance from any other electrical stuff on the car,you want your o2 signal to be as good as possible. If the strap is gone you can get one at the auto parts store or off any car out of the junkyard. The strap being gone my not be a problem but some times its the little things that can make the differance in winning and loosing or have a car that performes all the time as you would like. It also would be hard to find intermiting problems that could be caused by the ground to any electrical system.
GOODLUCK

 

[Benji]

Thanks a bunch!

also, since I don't have a place to connect it to, can I just bolt the strap between the O2 housing and downpipe and just sand it down to bare metal? Or maybe bolt it in between the testpipe and downpipe!

 

[THEDUKE]

No from pipe to frame or body. Clean the pipe or sand & take a stainless steel hose clamp to clamp it to the down pipe & screw or bolt the other end to the frame or body, this should work fine.

 

[RabidDonkeyBoy]

the point of the strap is for the O2 sensor to work properly. whne the catlyic converter warms up it becomes charged -/+ slightly, i forget which, and since its hung with rubber hangers the closest place it can see ground is the O2 sensor and it ####s up the reading.....

thats why the grounding strap is all the way down @ the catalytic converter and not @ the O2 sensor/housing, it is allready properly grounded, the catalytic converter uses teh same gorund as the O2 senor ####ign up the signal....

 

[PhoenixRPR]

You guys have been relaly helpful about the ground strap, I would liek to point out that I'm experiencing bad idle surge and have noticed my ground strap is hanging loose, if it helps the idle surge when i reattach it, I'll let ya know. Boy wouldn't that be something? My idle surge isn't a bad ISC or BISS, both are fixed.

 

[crashed97tsi]

Originally posted by RabidDonkeyBoy
the point of the strap is for the O2 sensor to work properly. whne the catlyic converter warms up it becomes charged -/+ slightly, i forget which, and since its hung with rubber hangers the closest place it can see ground is the O2 sensor and it ####s up the reading.....

thats why the grounding strap is all the way down @ the catalytic converter and not @ the O2 sensor/housing, it is allready properly grounded, the catalytic converter uses teh same gorund as the O2 senor ####ign up the signal....

so if you don't have a cat, would you need the strap?

 

[PhoenixRPR]

The strap is to ground to o2 sensor, so if you don't have a cat, that makes no difference, you'll need to still ground the wire.

 

[tsi_turboawd]

Originally posted by PhoenixRPR
The strap is to ground to o2 sensor, so if you don't have a cat, that makes no difference, you'll need to still ground the wire.

i dont have a cat and why would i still need to ground that wire from frame to exh. pipe? ..doesnt make sense to me

 

[doug]

To make the O2 sensor work properly. I thought it was explained pretty clearly.

 

[tsi_turboawd]

ill try strapping the ground wire on my aftermarket downpipe anyway and see if it makes a difference in fuel mileage and/or idle surge.

if i could find it. doh!

 

[Violater101]

If you use DSMLink, then you can disable the rear o2 sensor and hence will not even need the o2 sensor or the strap period. I used that location for my wideband o2 sensor and works great.

 

[plymouthtalon]

I have a question. I just installed a 3" N1 cat-back on my 2g, and the bolt on the old exhaust where the strap bolted on is gone. I just wedged the strap between a hanger and its rubber mount. Is that a good enough ground? Because today my car threw a "fuel trim bank 1" CEL. I don't know if the strap is causing that, but the exhaust is the only new thing since the CEL came on. The band of wires going to the 02 sensor is twisted a small amount (I twisted the sensor counter-clockwise a bunch before screwing it in, I guess I didn't twist it back enough), could that cause the CEL? I need to know if I should bolt the strap to a hose clamp around the exhaust, or if the hanger and rubber mount is a good enough ground.

 

[rockice]

i have 2 ground wires hanging from my frame can i just solder them back on to the 02 sensors?