[Webb]

Joe - EFI can work on a 2 stroke - but forget the O2 sensor. Use
an open loop system like the Polaris snowmobile line uses. For
max power you probably want to run a little rich anyway.

The reason  the Ox sensor won't work is that the air fuel mixture
is not kept out of the exhaust system. In fact, that is the
purpose of the expansion chamber, instead of a standard muffler.

An expansion chamber uses the shock wave in the gasses coming
through the exhaust tube to turn the last bit around and compress
it back into the cylinder just before the piston closes the port.

Result - the air fuel mixture spends some time in the exhaust
system before being compressed back into the chamber. That would
confuse the hell out of any O2 sensor there.

The system gets a 30% increase (according to one book) in power
out of this "reverse turbo" trick. I don't know if oil in the
fuel would kill an O2 sensor or not, but every system I know of
uses the thing open loop, because of the "raw mixture in the
exhaust" situation.


Joe Cheng wrote:

> Hi:
>
> I am new to the list. I have a 3-cylinder, 1000cc, 2-stroke
> engine in my race car and due to high g-force, the carbs are no
> longer working. Currently looking for a EFI system  and have
> the following questions:
>
> 1)   With oil in the fuel ( 32:1 ratio), can I still run an O2
> sensor ? Will the oil foul the sensor. I heard some Mazda
> Rotary race engines run oil in the gas (at 100:1 ratio) and
> have no problem with their O2 sensors.
>
> 2)   When sizing the injectors, I was told by Haltech
> (Australia) that for 2-stroke engines you have to double the
> injector size for the same HP output in a 4-stroke engine. My
> engine currently is putting out 210 hp from 3 cylinders.
> However, Haltech (USA) said size the injectors strictly base on
> HP figures. Anyone out there with experience on 2-stroke
> engines ???
>
> 3)   Who is a good supplier for throttle bodies. I need single
> individual ones to replace motorcycle type carbs. Any advantage
> in having one common throttle opening shaft instead of three
> individual ones ?
>
> Thanks in advance.
>
> Joe