Preferred way to punch a hole in an exhaust pipe

[DannoXYZ]

The true value of a unibit (step drill) can never be fully stated or understood until you have used one or own one.

I have a few of varying sizes both in metric and imperial. I would not be without them.

Yeah, extremely convenient!!!

I assume we're looking at top of exhaust?

 

[AllenV]

Yeah, extremely convenient!!!

I assume we're looking at top of exhaust?

I don't know how to describe the point-of-view in the image. But, the sensor will mount cable-end up at about a 30 degree angle from horizontal.

 

[Pevehouse]

I want to weld an oxygen sensor bung onto an early 70s Mercedes exhaust. The pipe is 2" diameter and maybe 14g wall steel with a nice patina of rust.

I have the whole exhaust out of the car in one piece with decent access to the surgery point. It looks like getting clamped onto my drill press or mill is a not at all practical.

Here's the question. How to drill a 3/4 inch hole in the 2-inch pipe using a hand power drill? The drill is 1/2" with the two handles.
1) a step drill
2) a hole saw
3) an annular cutter, which I do have in the right size
4) drill a smaller hole and expand that with a die grinder
5) something else??

Accuracy of the hole diameter is not so important.

I am worried that cutting through the curved surface will lead to all sorts of grabbing and twisting of the drill. So I am seeking advice in advance.

A fifth option would be to cart the thing down to a muffler shop and have them do it.

Carbide tipped hole saw

 

[AllenV]

Good ideas!!! What I've done along these lines with old Porsches is ditch the MPS altogether. Then use PIC controller taking input from modern piezo MAP-sensor that will simulate output of MPS/AFM/MAF sensors to give true 3D speed-density fuel-mapping based upon MAP x RPM. Once you've gotten MPS's calibration recorded, it's very easy to re-program PIC to whatever output curve you want.


Sorry for the spew, just tossing ideas out there that may help.

You've taken this much farther than I have considered.
I had not seen Tech Edge before. Very interesting and very useful. When I went to their web site, everything seems a bit stale and dated. Are they still active??

Back when I bought my Mercedes with the bullet proof M117 engine ( the 3.5 and 4.5L V8 ) I had considered putting a supercharger on it. The modest compression ratio and sodium filled exhaust valves looked very receptive to the idea. At the time I did a deep dive into Electromotive TEC3 engine management systems. None of this went beyond the research phase due to lack of time. A few years ago I found that Electromotive had disappeared! After I retired I looked at Megasquirt and a100% D-jet replacement including distributor-less ignition.
However, I began to dig into the underbelly of D-Jet and now favor preserving that as long as I can find parts. Mercedes and Bosch have been gradually stopping production of key elements. So we'll see how that goes.

One machine shop project that I will likely complete, even if I don't use it, would be to adapt a Mercedes distributor to hold a a 36-1 trigger wheel and Hall sensor. I already have a junk-yard distributor body from a 380SL.

 

[DannoXYZ]

Ah... I'll check as it's been 2-yrs since I bought something from TechEdge. I've been using their products for 30-yrs back when it was freeware/open-source project. About 10-yrs ago, they retired their discussion forums which was very helpful for Q&A with tips from other users. I've been looking at an all-in-one unit with on-board datalogging and display I can make portable for use on racing moto-bikes. Push one button to start datalogging, do couple laps, then come back and dump logs to laptop to draw pretty graphs for analysis.

As long as you're maintaining factory specs and performance from car, easiest to maintain as much stock configuration as possible. Least effort that way. Hoard or update most problematic parts.

Toyota had some '80s standalone ignition-systems I've adapted to CIS-based Porsches. So powerful that spark will actually jump from inside of ignition-coil-terminal to outside ground bolt if distributor wire's not plugged in!

What I've been doing lately on old moto-bikes is converting distributor points-type ignition systems. Get Ford EDIS ignition-modules from junkyard. Use factory distributor points to trigger EDIS. Which then drives coil-packs or COPS. Points are no longer high-load and lasts forever and you get high-power wasted-spark ignition.

 

[AllenV]

Ah... I'll check as it's been 2-yrs since I bought something from TechEdge. I've been using their products for 30-yrs back when it was freeware/open-source project. About 10-yrs ago, they retired their discussion forums which was very helpful for Q&A with tips from other users. I've been looking at an all-in-one unit with on-board datalogging and display I can make portable for use on racing moto-bikes. Push one button to start datalogging, do couple laps, then come back and dump logs to laptop to draw pretty graphs for analysis.

As long as you're maintaining factory specs and performance from car, easiest to maintain as much stock configuration as possible. Least effort that way. Hoard or update most problematic parts.

Toyota had some '80s standalone ignition-systems I've adapted to CIS-based Porsches. So powerful that spark will actually jump from inside of ignition-coil-terminal to outside ground bolt if distributor wire's not plugged in!

What I've been doing lately on old moto-bikes is converting distributor points-type ignition systems to COPs. Get Ford EDIS ignition-modules from junkyard. Use factory distributor points to trigger EDIS. Points are no longer high-load and lasts forever and you get high-power wasted-spark ignition.

My old car complicates things to where I just would not use its distributor in any EFI modernization. It comes from 2 model years where no vacuum advance was used. It has only vacuum retard which kicks in at idle as a smog thing. This is the car's only smog feature. Thus one benefit of doing the Full Monty MegaSquirt with distributorless ignition is to have a proper vacuum advance timing map. I have already put in Pertronix ignition which tosses the points and gives me high power sequential ignition, RPM dependent dwell, and tweaks timing a bit to compensate for electronics lag at high RPM.

 

[DannoXYZ]

Yeah, the Pertronix probably gave it great partial-throttle response eh? Nice and lively.

Really helps on many old carbureted bikes with 2D RPM-only maps. Upgrading ignition-only to 3D maps made them feel so much more peppy and eager!