Thread: Opinions Please.........

Looks like a small supercharger to me.

I have been over the website, and it is not clear how it works. It is clear that it is an air compressor (probably low pressure, high volume), but what is done with the air is not at all clear. It may be injecting air into the exhaust to promote burning of the unburnt fuel in the exhaust. If this were done before the turbocharger, it could both reduce pollution and increase boost and hence power without using more fuel. If used with a non-turbo engine the effect would be only to reduce pollution without any increase in power.

John

Well, it is obviously an engine driven compressor. The web site tells absolutely nothing about how it functions or how and where the output is plumbed. Is it just another version of the air injection sustems used in the past? It is going to absorb some engine output to drive it. Is there any payback or is it just another emissions control system?

This page : REDD Overview :: Rotec Diesel

Seems to be saying that it converts a 4-stroke into a valved 2-stroke.

I assume the kit also comes with a new injector pump drive which turns it twice as fast (plus cam mods???), in order to make the pump inject fuel every 2 strokes instead of every 4.

It seems that the pump is then adjusted to give a very lean burn.

Interesting idea, but I can't see how a turbo or supercharger can't do exactly the same job - probably without the need for a 2-stroke conversion...

As with most of these type of devices, if they worked, car companies would use them - diesel soot filters are $$$.

Originally Posted by isuzurover

This page : REDD Overview :: Rotec Diesel

Seems to be saying that it converts a 4-stroke into a valved 2-stroke.

I assume the kit also comes with a new injector pump drive which turns it twice as fast (plus cam mods???), in order to make the pump inject fuel every 2 strokes instead of every 4.

It seems that the pump is then adjusted to give a very lean burn.

Interesting idea, but I can't see how a turbo or supercharger can't do exactly the same job - probably without the need for a 2-stroke conversion...

As with most of these type of devices, if they worked, car companies would use them - diesel soot filters are $$$.

Thanks - I somehow missed that page. Yes, that is exactly what they are doing. Probably rather than a new pump, new timing gears/sprockets, which would be needed for the camshafts - note that these turn at crankshaft speed in their conversion. A turbocharger would require a very high boost get enough air in to give as lean a burn as could be achieved this way, and this would raise problems with compression pressures.

I think that the advantage of the conversion is just that - it is a conversion of an existing engine, which maintains the same power while improving both economy and emissions. It would not be attractive to a manufacturer because of weight, complexity, bulk, compared to a modern electronically injected engine that relies on very accurate control of fuel timing to achieve a good burn, with a soot filter as a final cleanup.

But when the alternative is to replace the vehicle, it could well be attractive, although it will need either a mandated change or much higher fuel prices, I would think.

John

Its basically turning a 4 stroke engine into a 2 stroke.
The pump is doing what is usually done in by crank case of a 2 stroke engine, ie, creating the pressure pulse which transfers into the cylinder via transfer ports.
The only real iffy with the REDD is the fact it is restricted to using the original inlet and exhaust valves.
As most would know, the exhaust in a 2 stroke petrol is an expansive gaping hole in the side of the bore aided by the expansion chamber at the exhaust head to create a low pressure area that the exhaust can escape to thus creating a vacuum in the head for the crank fed pressurised intake charge to fill it ready for the next cycle.

A fourstroke engine has a larger intake and smaller exhaust valve size, of which both are at the top of the cylinder. The ability to evacuate the cylinder of exhaust gas is totally reliant on the piston going full stroke to the top.
Have a look at a Detroit 71 & 92 series 2 stroke diesels. The process these use is a supercharger or turbo fed intake into the lower cylinder area but has 4 exhaust valves in the head to pass the exhaust.
Air enters through ports in lower cylinder walls when piston is down. Air is compressed as piston moves up. Fuel is injected just before top dead center. Mixture ignites, exhaust valves open at point before piston again uncovers intake ports in the cylinder wall. Air is forced in by supercharger/turbo and exhaust gas is expelled by the incoming charge and the pressure of the exhaust gases.

The REDD process is not quite consistent with 2 stroke principles and looking at it, although it would work to some form, is really only a cheaper way of doing something that has already been around for some time, just not as good.
It would be difficult to adapt to turbo diesels and essentially would be pointless as the engine driven pump would negate any advantages of the turbo in the first place.
Not to mention how much power would be sapped by running the pump in the first place.....
Cheers

Andrew

Given that emissions regs have killed (or are actively killing) all two stroke engines, how does this improve emissions over a well tuned four stroke diesel?

Sure it'll improve emissions over one that currently belches smoke, but there are far cheaper ways to improve that.
The cost of new cams, new pump drive gears, the scavenger/supercharger and installing it is going to compare unfavourably with rebuilding the whole engine and bolting a turbo to it.

What is the downside of running an injection pump at twice the design speed?

Lots of interesting comments, my friends away in the states at the moment but on his return I'll be firing lots of questions at him, so if you have any specific questions fire away.
This product is tried and tested in the USA, so I'm sure it's not a product that doesn't work.

I'll be sure to keep you informed on it's progress and I'll post his responses too.