A technical question about a jake brake.

You are wrong. AFR at idle is indeed something like 100:1, todays low nox engines have smoke limit at 22:1 or something like that, perfectly tuned diesel might get as low as 16:1 without smoke. And no, diesels don't miss or burn pistons due to lean burn and there is no O2 sensors in diesels that control AFR.

 

Then why is CAT looking at things like O@ sensors for the Tier 4 Locomotive Engines. How do I get my Information called someone that Works at National Labs here in the Area. They are the ones that are Testing Cat/EMD which they bought last Year and GE's Tier 4 Protoypes. Both of which are running an O2 Sensor ON THEM. I gave my Source a call he is a Mechiancal Engineer for the Lab. He flat out has seen what happens when you run a Diesel motor lean for way to long it will and does BURN the Pistons. Sorry in the off season when not pulling loads for my First boss I maintained his Equipment and I alsop had to OH some motors that had Burned Piston Scored Liners from low Fuel flow into those Pistons. Remember Lenny from School Diesl is not only a Fuel it also works as a LUBRICANT. I was pulling wrenches in the slow times when we had pumps out for Scored Pistons Pumps from the Switch to Low Sulphur Fuel. We were seeing the Same Crap in the Liners.

 

They might use O2 sensors for testing purposes and new urea engines have NOx sensors that are almost similar to O2 sensors.

Overfueling burns pistons because the EGTs get too high, retarded timing might be another reason but lean is not.

 

Lenny trust me my boss fired any one that turned up his PUMP. If your engine smoked black you better have a Mechaincal Reason for it like a Turbo Failure and these were with Big Cam 1 series and Small Cams 1693 Cats in his OTR/ Grainrigs. He also had his Tractors for the Farm set up the Same way. I saw more than one Burn Piston from to little Fuel.

 

Then they would burn a piston running on level ground on light load, even if the pump was turned out for more fuel.

 

Lenny I know more about Cranking OLDER Diesels up than you'll ever know. Most of the Stuff I was working on at my First Bosses was Mechinical CONTROLS. The Only thing Electrical on it was teh Starting and Charging System. We even had 3 Trucks with Air Starters that used to scare the living Crap out of the DOT when they were on the road. The Newest Enginge he had in a truck was a 3406B series Cat. That was the Newest thing in the Fleet. Considering we had KTA903A's mounted in 2 4 wheel Drive Tractors that were the Primary ones we used to Plow the Fields.

The Trucks that hauled the Grain the newest one of them was an 84 and this was in 1996. Yet we ran all over the place in these things. Our Shop was fully Equipped I had all the Equipment needed to Overhaul any Cummins Pump out there Injectors heads I could and DID Rebuild it when needed. My truck that I drove til I was hit by a Drunk Driver was a 1973 International COE model 4070 with a 4X4 Transmission mated to a 290 Cummins.

 

You are thinking gas engines. A gas engine will maintain a somewhat constant AFR. A Diesel throttles using only the fuel and not with air at all. The only way the amount of air going through a Diesel changes is with RPM and boost. It will always pull in as much air as possible. Fuel is injected based on throttle position, boost, RPM, and possibly other variables depending on engine. When you idle a Diesel, it injects only enough fuel to make the "boom" to spin the engine at the desired idle RPM and is running very "lean". When you press the accelerator pedal down, it increases the amount of fuel injected (in essence, making the mixture more rich) and increasing the power and RPM. The only side effect of having an AFR more lean than about 18-22:1 is that you're not making as much power as you could potentially make. Get it more on the rich side, you'll start to have smoke, increasing EGT's, and other issues. New engines are getting a variety of new sensors and features to help control emissions. In the end though, you cannot idle or cruise a normal on-road Diesel at a 15:1 AFR.

 

A gas engine is a variable compression engine a diesel is a constant compression engine and when the fuel is injected it burns period their is always suppose to be more air than the fuel needs it produces power by increasing the pressure in the cylinder. There is very little chance of the pistons hitting the valves you have to be doing in the 3500RPM range to do that in a big cam Cummins a, N14 will do 3650 without damage 3670 and it will bend push tubes.
Jake's work as has been posted as an air compressor nothing to do with vacuum.
Mercedes has an extra valve in the head that opens and transfers air between cylinders, and when on high has an exhaust brake that boosts the pressure to 53 lbs. and no noise.
The Jake's work better the higher the RPM you run them at Cat has a 3000 RPM limit.
it is in there literature. The early Cats, bent rocker arms even in units that had no Jake's, it was a poor design.