I'm about to drill the headers for my 914/6 conversion and weld in a bung for an O2 sensor. Where have other people put the sensor? I'm thinking of putting it on the left side, just behind where the three pipes join, facing outward.

IMnonHO,

Anywhere within 6 inches from the collector going out the back of the car.

(I like in the collector or very close if possible)

It should not be installed BEFORE the collector or less than 12 inches from the end of the exhaust if possible.
(unless you want to read just one cylinder)

If placed at less than 12 inches from the exhaust, reversion pulses may pollute the signal, thus creating improper O2 readings at low RPMs.

Down stream of the collector also works well. Keep as close to collector as possible for fast response. Especially if you are going to plug the O2 input into a EFI system at some point.

When we dyno an engine, we have found this works the best. We have also used a Horiba 5 gas analyzer to compare with the several aftermarket O2 sensors. When placed as explained above. The comparisons were very close.

NOTE: If you are ever going to install a EGT gauge. Now is the time to weld in that bung. (On the other side) They are a great tuning tool. And keep the driver in the know as far as cooking his engine. And it really lets you know what happens when either fuel, timing, secondary ignition or load is changed. Kewl tool.!!!!
(A quad gauge and 4 senders is the cats meow. $$$$s)

Thats my experience. Yours may be differant.

C

Pardon my ignorance, but am I correct in assuming "the collector" is the piece that combines three pipes into one?

This O2 sensor is going to be used for feedback to a Megasquirt EFI system.

The EGT is a neat idea. I've used them on aircraft but have never seen one on a car. Can you point me at someone who makes the probes and gauges.

YES to the above

Analog EGT gauges: (Note: They also have a dual and quad gauge. You can see both exhausts)
Westech gauges
OR
Westach Corp


Digital EGT gauges:
Dakota Digital

These are just some of the offerings that are available.

I personally like HKS gauges the best. $$$$s
HKS EGT

It has a logging, peak, and signal output. It's the ShiZzzzle

C

I seem to recall reading somewhere that even getter than an EGT was sight glasses of somekind. IIRC, British cars used to use them, and there was "one" for every cylinder. I seem to think that it was like a glas tube, and they looked at the colors of the flame or something...

Ahh, I don't really remember. Sounded neat except you couldn't look at it while driving.

I remember the same story from somewhere in my past.

Thankfully we have better technology today.

Must of been pretty funny back in the day... can you imagine this...

Jake Raby, len Hoffman, the guys from FAT and a couple of 914 bros are all sitting around the garage drinking a couple of beers.

Raby fires up one of his engines and tells us all the sight glass is telling him it's running rich. The guy from FAT says "NO WAY JOSE" it's running lean.

The 914 clubbers look at each other and tell them" can ya give me a price break on the new sight glass thingy?"

It would a been hilarious.....................

Now... back to the cave.

C

Click to view attachment
Click to view attachment

Thats the ticket.

Simple and nicely done...!!!!!!!

C

Nice photo. I like the idea of putting it on the top of the collector rather than the outside - I will change my plan accordingly. Thanks.

Before I forget,

Henry Shmidt of SuperTech fame once told me that EGT and head temps on both 4s and 6s are totally unrelated MOST of the time.

And when checking this via dyno runs on the 4 bangers specifically. He was very correct.

So i was thinking that Head temp and EGT and oil temp is a "good" case scenario for empirical engine heat data.

Just wanted to throw that out.

I B thinking that Brett or some of the racer guys would know WAY more about this than me. If ya need to know more. Check wid da guys in the paddok section.....

Cheers,

C