The Tom Thumb is the first Catalytic Converter Test Kit on the market of its kind.

18 Nov

The Tom Thumb is the first Catalytic Converter Test Kit on the market of its kind.

Fits most Bosch O2 sensors.

As most know VW and Audi’s have some weak converters and the old P0420/430 group of check engine lights that come with them.

There are few fixes out there. Does it need a new O2 sensor? Or is the wiring Bad? Is the ECM working right? Or do you install a OEM converter Big Bucks or find a good after market still comes with a high cost.


With the Tom Thumb you can test everything in one test drive.

Some use an anti fouler to shut off the Check engine light most of the time this never works right.

That is added to the end of the rear O2 but adds like 1 1/2 inches to it. But sometimes hits the floor board.

What they are trying to do is slow down the reading of the rear O2 so it does not match the reading of the front O2 sensor that is used for fuel trim.

Two things must happen when the engine tests its converters first it looks to see that the rear O2 does move when fuel trim is adjusted the next test is

It looks to see that the rear O2 is slower than the front O2s movement by some kind of %

So I build the Tom Thumb, it fits on the end of the bosch O2 sensor like china’s finger toy. You just push it on your rear O2 sensor hard reinstall the O2 and test drive.

The Tom Thumb slips on the Rear O2 and into the converter. This is a test tool to make sure the ECM is in control.

Here are some pictures of the Tom Thumb P0420 test it at work and the Vag Com scanner screens showing it working.

Just click on pictures to enlarge

The stock O2 location using the Tom Thumb

What it looks like with a useless anti fouler

This a bit hard to see but what its show is the bottom line is the front O2 swing for fuel trim.

The yellow line is the rear O2 swinging very close to the same rate of the front O2 at 700 RPM

This converter is ready to fail a P0420.

The same converter using the Tom Thumb almost like new.

This is the Rear O2 in the new converter green line and the rear O2 yellow using the Tom Thumb in the old converter at 700 RPM.

The Tom Thumb is build in a way so the dimples help air flow around and inside the new controlled chamber here are some close ups.

Some have asked will it fall off NO it is a press fit. It can be pulled off if you must with some force and use on some other O2 sensor.

If it did fall off it is in the back of the converter so it will never hurt anything made of hi temp steel too.

The Tom Thumb is the first Catalytic Converter Test kit on the market of its kind it comes with everything you need.

Very simple to use just remove the rear O2 sensor slid on the Tom Thumb (Push it on Hard) on to the end of the Bosh O2.

We give you some furnace cement to help hold it to the O2 if you wish to smear it on the matting edge and some lube for the threads

Reinstall the O2 and clear the codes with a scanner. Now just test drive on the high way at 55-65 MPH for a few miles.

Now retest the readiness for the Catalytic Converter  if it passed. The Tom Thumb test kit just tested the O2 sensor

the wiring from the O2 sensor to the ECM and tested the ECM itself.  The Catalytic Converter is BAD replace it.

I do have a new How to VID

I do not sell them over the internet any more. I will install them at my shop here in  Pembroke MA 02359

Bob Mann Auto

111 High ST

Pembroke MA 02359


Bob Mann


My next CNG project a 2002 Audi A6 2.7 twin turbo with 79K using the latest Auto Gaz OB2 controlled system.

26 May

My next CNG project a 2002 Audi A6 2.7 twin turbo with 79K using the latest Auto Gaz OB2 controlled system.

This is one of the best systems I have seen so far supper well build uses the news peak and hold injector they are  OEM injector  and a high power regulator  to boot.

Here you can see the engine area my plan is to add the system and have it look like it come from Audi.


Stock engine

We pulled the top shields and air intake Y and installed the new CNG injector.

I use what I call the 6 inch rule. You must do your best installing the CNG injector as close to

the stock  gasoline injector as possible  for the best performances no more then 6 inchs away.

CNG injector mounted

Here I layed the stock air tube over the CNG injectors just to see how it looks.

Air tube layed back on engine




VW TDI Diesel CNG blend System install how to

24 May

CNGVW 037Here is some pictures and install information for my CNG Blend kit.

The kit is very simple only a few parts the main one is the 2 stage regulator which takes the high pressure CNG from 3600 PSI down to a few LB to be breathed in to the engine intake.

The line from the tank and coolant line have been installed all ready.

Next is the feed tube placed in the intake track

Than the feed tube and flow adjuster is installed.

The little gold screw is used to regulate  HP for the kit.

Here is it is installed very clean and simple.

There are only a few wire need to be hooked up I use the power from the injector pump as its key on source.

We use one of the crank sensor wire as the tech signal  a ground is installed and one wire for the gas on solenoid

you just have to clip the fuel pressure/ gas gauge contactor  on.

Now run the switch in the car.

For added safety I install the ETS  int ot the turbo dump pipe.

this is used to turn on the CNG system and off if the temp gets to high a must on a Diesel

I use one from it was modifed for the TDI and worked very well.

For inside it is just a simple on and off switch with some LED to show how much CNG you have in the tank.

Below I show the ETS on the left is the $200 one it can be adjusted to turn on the CNG at a low  temp and shut it off

if the EX temp gets to high. I set it to come on at 300F and shut off the CNG blend if it go,s over 1000F to be on the safe side.

It can be adjusted at any time.

The one on the top right is the one that will just shut it off if you hit its high limit $120

and the little switch in the bottom right is the CNG on/off and gas tank level LEDs .

So there have it.

Bob Mann

Here is what one test driver said on a forum

So since I’m only about 30 miles away in Cambridge I went and checked the car out. Bob had me drive it, I would compare the car drivability-wise the same as any other MKIV TDI you would get in. Power was comparable to something over a chipped car. It’s very smooth, and if you blindly just got in the car and drove it, you wouldn’t know it had the CNG other than the extra power, much like you wouldn’t know the difference if you were running bio. Difference is no gross odors like veggie, no messes from home-brew, just a little pump outside the house. I thought it was cool, only thing stopping me right now is the initial cost to get it going. But as I said before I think the costs would be covered in about a year from what I’ve figured. Fuel is easy to pay for on a week to week basis but as a lump sum it will take some saving. I’m fortunate enough to have gas at the house so this is a realistic option for me. I think the point is being missed here, he seemed to be a pretty good guy and not a salesman. Just sharing results of the project much like you see all over the boards so I don’t know why everyone seems to have an issue with this.

But it looks like I have been locked out from that forum for showing some thing other than BOI- Diesel .

To up date the CNG Diesel testing here are some Massachusetts emission test on Diesel tail pipe tests before and after CNG blending .

Below is the test with it just on Diesel

It with the CNG blend  it is a reduction of 400% in tail pipe particle mater .

My Youtube of the car running on CNG






autogaz di2autogaz disautogaz3autogazwiring

Bob Mann

VW TDI Diesel Gets 120 MPG on one Gal of Diesel with CNG blend!!

23 May

VW TDI Diesel Gets 120 MPG on one Gal of Diesel with CNG blend!!

I will give the math up front. 2001 VW TDI 129K using my new CNG blend test system.

Round trip 90 % Highway 75-80 MPH.

60 Miles round trip used .51 Gal of Diesel   and 1.2 GAL (GGE) of CNG yes I have the slips.

That is a 60% blend of CNG it has very smooth power to boot.

The EGT never went over 990F on long uphill pulls.

Using this system should give you a 70% reduce in fuel cost per mile traveled

If I do the math right here on an average a TDI gets 45 MPG at $4 a GAL that is 11.2 cents costs per mile traveled.

Using a CNG blend system it cost 03.3 cents per mile traveled on Diesel. CNG cost per mile traveled is

.02 cents at $1.00 a GAL (GGE).  If I did the math right someone please check it that is a cost of

05.2 cents per Mile traveled a savings of 58.2 %. I pay for home fueling now .40 cents a GAL that should push me in the 80% saving on fuel cost.

I have over 1000 miles on this test system no codes just works.

Hello it has been talked of doing Diesel blends all over the internet. But I have built this system round a simpler way I think.

So the point was to show we can blend fuels and cut costs for miles traveled without giving up performances.

I use a CNG vacuum controlled regulator modified by me. We dump it in the air intake after the MAF and before the turbo inlet.

I use an ECT from   and wire it in to turn on/off the CNG for safety. It runs about $200

The front end of the kit is very easy to install about 2 HR. Than a high pressure line ¼ inch or 6mm is run from the tank to the regulator.

I give up some trunk space for a CNG tank on a Jetta ½ the trunk on this TDI I use 2 small test tank that fit in the spare tire space 1.5 GAL filled.

For the front end kit I see it in the $500 range

Used tanks can be found from $100 to $1000.

Someone but it to me this way if you pay $4.00 a GAL for Diesel and get 40 MPG so for 60 miles it was $6.00 and for me with CNG blend it cost ( using $1.00 a GAL for CNG)

it cost $3.20 to do the same 60 miles  that is a reduction of in half of fuel costs. But when you put the home fueling station in the math I pay .40 cents a GAL of CNG at home.

It is now better I need someone to check this math is it 50% or 100% reduction ??

THe dash fuel gauge 200 miles on it



Bob Mann


22 Apr


I just finished my New CNG VW Beetle Concept. The VW Beetle is so loved by people that I felt it need to be the focus of a new CNG push.  So I build the complete package starting with 1999 New Beetle four cylinder automatic so that any one can drive it. Had a low cost CNG kit fromSouth Americashipped in. These kits are certified ever where in the world but theUSA. But here inBostonMAno one knows much of CNG and to fined a pumping station is a drive for me twenty mile one way.

The search was on for a Home Refueling Station this is a pump that takes you home neutral gas and pumps it in to your cars CNG tank over night. There are used all overCanada, Europe, South America and a few smart States in theUSAmostlyMidwest.

I started this project last year and never stopped. Got the Beetle to run great and pushed MPG of CNG to thirty miles in the city over a hundred miles to the tank and I still have the gasoline tank yes I run  on CNG or gasoline at a click of a switch.

Searched and found a used Home Refueling Station it was rebuild and tested and had it shipped in and installed a new gas line to the garage and updated the power. Now for the big test every thing was installed to code the car and the Home Refueling Station. Turned on the power and gas the little lights light up. I am feeling pretty good at this point hook up the gas line from the pump to the Beetle and hit the start button on the Home Refueling Station and off she went sounds like a window air-conditioner. Watched the pressure gauge in the car as it slowly went up every thing was working as planned.

A Home Refueling Station fills you cars CNG tank over time mostly at night when demand for power and gas is low. The one I have will fill a four Gal tank over four hours

To a pressure of 3000 PSI at a cost of below a dollar per GAL before Federal rebates.

After the Home Refueling Station fills you CNG tank it shuts is self off.

The feeling of filling my car at home safely and not having to go to a gasoline station at

$ 2.60 a GAL for regular and climbing it was so GREAT now I drive by those gasoline

Station with a BIG SMILE what a feeling.