December 4, 2012

I found a K&N filter that will fit my throttle body. It has enough room on one side to mount a pipe for Positive Crankcase Ventilation, PCV. The PCV has to be above the throttle body to keep the vacuum low.

K&N right


K&N left


Lamda sensor (O2 sensor)

December 4, 2012


A bung has been welded to the muffler to accept the O2 sensor. It is centered between the exhaust outlets.O2 left


O2 right

Intake manifold

December 4, 2012

The intake manifold has been given to a machinist to mount the injector bungs. They will be in the curve of the manifold where it bolts to the heads. Both bungs will be positioned so the injectors spray directly into the center of the intake port. The first picture is the “stock”, unmodified manifold.

Stock intake mni 1

Mounted throttle body

December 4, 2012

I’ve fabricated an adapter to mount the 42 mm throttle body on the intake manifold. I think it will do the job.Image

The kit has arrived

December 4, 2012

Parts: 1.ECU (aluminum housing, water proof) 2.Harness (including the connectors, waterproof) 3.Throttle Body assembly • 42mm Throttle body (including TPS sensor) • Idle Air Controll (IAC) • 2x Fuel injectors (190g/min) , 4.Fuel pump assembly • large Fuel pump (Flow rate: 45L/h) • Fuel pressure regulator(3bar) • Fuel filter • fuel hoses and clamps 5.MAP sensor (1.05bar) 6.Engine temperature sensor 7.Intake air temperature sensor 9. Oxygen sensor and bungs (INCLUDED) 10.Serial communication cable (to a computer) 11.Serial to USB converter (included) 12.CD – free tuning software (also downloadable)

This is a sample of what the kit looks like. My kit does not have an injector in the throttle body since I am going port injection. My kit also includes two injectors and bungs to mount the injectors in the intake manifold.



November 24, 2012

The EFI must be triggered through the ECU to open the injectors. I’m not sure how I’ll do that. The best way is with a trigger wheel. The preferred trigger wheel uses 36-2 teeth, meaning total 36 teeth with 2 missing.  The two missing teeth will be 60 degree before TDC, or 6 teeth before. Here is a picture of a 36-1 trigger wheel.


Installing one that doesn’t interfere with the rest of the engine is complicated and none are available commercially that I’m aware of so it would have to be fabricated. I may be able to trigger from the kill circuit built into the coils, but at this point I just don’t know. I have selected a supplier for the kit and ordered what I think I need to get started. I will identify the supplier at a later date if I am satisfied with the customer service.

It seems like a good idea

November 24, 2012

I’ve decided to take a shot at installing EFI on the 35hp 993cc Briggs horizontal V-twin. I have set some specific criterion. It must be closed loop and have port injection. I have stripped down my engine to start work and purchased an extra intake manifold to modify for the injectors.ImageImageImage


October 22, 2012
I’ve run the Kohler 29hp EFI all summer. I’m sold on it for several reasons. Yesterday at 16 degrees F it made two full revolutions and started and idled at 950 rpm. I let it warm up at idle while I got the boat ready and it never missed a beat. The fuel economy is much better than the 27hp. Kohler advertises 27%, but I would guess 20-25%. It runs much smoother at all rpm’s and never loads up in idle. The only negative I have is it doesn’t push as big a load as the 35hp Briggs, but that shouldn’t surprise anyone since it has almost 250 cc’s less displacement. The Robin and Kawasaki engines with EFI are very close to the Kohler in displacement but they are both open loop systems as opposed to the Kohler closed loop. Early automotive EFI’s were open loop which in my opinion are just good carbs. The closed loop has an oxygen sensor in the exhaust which tells the ECU how much to adjust the amount of fuel to inject based on the exhaust gas mixture. This is in addition to the other sensors such as intake air temp, oil temp and air density. I don’t know where the injectors are on the Kawasaki, but the Robin has them in the throttle body. The Kohler uses port injection which gives a better mixture at the head of the valve. I’ve asked Kohler, several times, when they are going to sell the 999 cc with EFI and their standard answer is about a year. The fact is, that if they don’t have an OEM manufacturer with a large enough demand we’ll never see it. Mud motors do not produce large enough demand. I’ve heard rumors for years that Briggs is working on EFI, but I don’t know what type or which engine. Bottom line is I think EFI is way better than a carb for my application and after running it for a year wish the big Briggs or Kohler had it. I’ve got a 993 Briggs with 65 hours on it. Maybe I should use the long, dark winter to convert it to closed loop EFI.



Why put Electronic Fuel injection (EFI) on 993cc Briggs

October 22, 2012

Better fuel economy, Easier starting, No carb icing, Smoother idle, More power.

Exercise complete

February 24, 2012

The DSD was fun and educational to do. The CVT wasn’t as good as I hoped. It didn’t seem to shift when under load and that could have been due to low engine power or poor clutch adjustment. I tried a 1.5 to 1 ratio with the standard drive with no improvement. The best speed was 13-14 mph and that is slower than I needed to meet my goals. The weight, at 565 lbs, was way too heavy. I parted out the lower unit and sold the jewel of an engine to a gold miner. Time to start another project.