# A Engine Question.



## BRIAN (Aug 1, 2014)

After looking at the forum I can see that a lot of you have nothing to do, so to save you getting bored I will drag up a question i raised on this forum when the numbers were less than 1000.

 The engine in question is a Commer TS3 a 3 cylinder 2 cycle diesel 

In the last stages of its development before G M pulled the plug , the makers of the fuel pump CAV
developed a version of their DPA distributor pump for this engine.

Now??? the pump ran at half engine speed  Not at engine speed as normal ???

So how was it done???

Thinking caps On,  Unless you know!!!!!!

Brian.:nuts:


----------



## cvairwerks (Aug 1, 2014)

6 port rotor


----------



## BRIAN (Aug 1, 2014)

On the right track But how???
Brian.


----------



## JimDawson (Aug 1, 2014)

I'm guessing they drove it off of the idler gear.  That is the only thing in there with a 2:1 ratio.  Not sure if that is part of the accessory drive system or not.


----------



## Vavet (Aug 1, 2014)

My first thought was DUH...it runs off the camshaft...diesel engines still have camshafts, right? 


Then I realized, 4 cycle diesels have camshafts, but there are no valves and therefore no camshaft in a 2 cycle engine. 

It could still be done essentially the same way though - v-belt and pulley drive with the pulley on the fuel pump twice the size of the pulley on the crankshaft.


----------



## BRIAN (Aug 1, 2014)

OK we have some interest.
So I will start by clearing up the points raised.
On this engine the pump was driven from the gear train that ran the supercharger ( ported 2 cycle diesels use a big blower to push out the gases and refill with clean air, By closing the exhaust ports early we get supercharging for free). so it is simply a 2-1 reduction by gears.

But the question I am asking is how do get a distributor pump running at 1/2 speed to put out the fuel pulses at engine speed. 

If you think of a 3 cyl  distributor for a petrol engine , one turn gives 3 sparks, how do you make it give 6 sparks ( 2 turns output ) when you have only turned it Once???

On the Point made about camshafts, Yes some 2 cycle Diesel engines do have valves on the exhaust side operated at engine speed, and ports on the inlet. GM  -- Foden --etc, but this is not the question.
Brian.


----------



## cvairwerks (Aug 1, 2014)

The pump was probably a stock 6 cylinder unit that simply tied every other port together, allowing two injection pulses for every rotation of the pump shaft.


----------



## BRIAN (Aug 2, 2014)

Creeping up on it,

The pumping system was 6 cylinder, but the ports are not together.

So how do we take 6 injection pulses and distribute them to 3 outlets at twice the rate.

If it helps think of a 6 cylinder petrol engine distributor, but the cap only has 3 leads.

Brian.


----------



## BRIAN (Aug 7, 2014)

No takers I think it's time for a hint .

 The out put of this pump is opposite to the rotation . no gears are used the distributor shaft runs in one direction but the output is contrary at twice the speed???

I will offer a free down load of my Beginners clock book to the first person who in my opinion gets the correct answer.

Offer closes on September 1st.

Brian.:think1:


----------



## chuckorlando (Aug 7, 2014)

Maybe throw lever type deal. Cam type lob to trip it and the pivot would throw the other in the opp direction?


----------



## BRIAN (Aug 8, 2014)

No leavers Chuck, so keep thinking

Brian.


----------



## Wdnich (Aug 14, 2014)

Was this the one that had the injector pump mounted on the top of the engine, and the pump was driven off the back of the crankshaft. ,in  separate housing before the transmission bell housing. It was similar to a twin cam design, two or three lower gears driving a chain to two upper idler tension gears, then the final gear on a drive shaft going to the injector pump. It had a sort of shaft plunger setup, that rotated compressing the fuel. God old age is creeping up on me.  We had one in the shop I attempted to worked at  in New York to work. Technical info was hard to come by, we ended to sending it down the city for a gentleman to work on. He sent back schematics, but it still baffled me. 

I spent the last hour looking through old photo albums for the pictures I took while we disassembled. No luck at all, wife ranting.


----------



## JimDawson (Aug 15, 2014)

JimDawson said:


> I'm guessing they drove it off of the idler gear.  That is the only thing in there with a 2:1 ratio.  Not sure if that is part of the accessory drive system or not.



The above and 2 injectors per cylinder, with a firing order of 1A 3A 2A 1B 3B 2B


----------



## BRIAN (Aug 15, 2014)

Hi all 
 Not 2 injectors per cyl Jim.   The pump only had 3 outlets. but a nice try.

Hi wdnich.
I think the one you worked on sounds like the last production model that ran the DPA pump at engine speed and dumped every other pulse back to the tank. 
The photos sound good if you can find them. Things were changing fast in those days.
Brian.


----------



## Wdnich (Aug 17, 2014)

I have wracked my brain for three days over this one. The one thing that  keeps coming to mind would be a crank trigger system, that would trigger the pulse for the injectors to cycle, possibly off the flywheel or a independent crank ran pulley.


----------



## BRIAN (Aug 17, 2014)

All the clues are in posts #8 and #9
 its so simple you are going to hate me for this

Brian.


----------



## Wdnich (Aug 17, 2014)

6 pulses that fire to 3 leads.

A distributor type pump running off the timing system. The rotary cap has opposing ports that fire at the same time to the cross plumbed injector. Two leads into one.

I am going to wrap my head around this before it is over.


----------



## BRIAN (Aug 24, 2014)

You are running out of time the offer of the free download of my book closes on sept 1st.
the best so far is   cvairwerks  comment that the pump must be 6 cylinder OK all you have to do is distribute  6 pulses at half engine speed into 3 outlets.


If it help think of it as a 6 cylinder car distributor but the cap only has 3 leads ???
what can you do to make it use of the wasted 3 pulses to produce 6 pulses at twice the speed.
 don'.t alter the bottom end of the distributor or the drive.

_it's  O So  simple.ondering:

Brian_


----------



## chuckorlando (Aug 24, 2014)

each lead fires twice using the 3 "open" ones?


----------



## BRIAN (Aug 25, 2014)

Yes but how is it done???


----------



## Wdnich (Aug 25, 2014)

I am awaiting the ultimate answer. I was obsessing way to long on this one.


----------



## JimDawson (Aug 25, 2014)

''Y'' the opposing ports together.  the closed port would have little effect on the flow from the working port.


----------



## BRIAN (Aug 25, 2014)

post's #8 and #9. give all the clues.

It's a good thing I am over the pond in the Med because I fear for my life if I have to tell you the answer.


----------



## BRIAN (Aug 31, 2014)

OK Sept 1    3.15 in the morning and I had to get up, 
So here is the answer.

Look at a 6 cylinder  distributor with the cap off .

Turn until the points open. and the rotor arm is pointing to one of our 3 outlets,

Continue turning to the next points opening and the rotor arm is pointing to a place that we do not have a lead????

 BUT look at the rear of the rotor arm ,it's pointing to a lead,  But in the opposite rotation, So make a rotor arm with 2 contacts
and away we Go.


With the fuel pump simply drill the port all the way through the rotor.

I think I will go back to Bed.


See you later  Brian.


----------

