I follow your logic, however there's one point that I think you're missing.
Your theory assumes a uniform mixure of air and fuel in the cylinder, and I
think that is generally not the case. It's possible (probably likely under
heavy load) for there to be excess air in one part of the cylinder(maybe
near the intake valve) and excess fuel in another (like around the
injector). This could give you smoke, even when you're not burning all the
O2 in the cylinder. Also, diesel burns fairly slowly, so with high enough
fuel loads your injected fuel might still be burning when you're way past
TDC, even on the way out the exhaust.

As I understand it, the propane helps to utilize that extra O2 (if present),
but more importantly it acts as a 'catalyst' of sorts, to help get the
diesel fuel load to burn faster, therefore more completely *and* (possibly)
at a more optimal time during the stroke.

On Sat, Jan 10, 2009 at 1:16 PM, Arnie Grubbs <vhuntertdi@...> wrote:

> FYI: If you can hit the go peddle hard enough to get smoke out of pipe
> (diesel smoke, not oil burning!) in a NA diesel, I don't think you want to
> add propane.
>
> Think about it. If you have enough diesel injected that not all of it is
> burning (smoke) that means you don't have enough air(oxygen). So, now you
> want
> to inject another gas in there that will displace some air in the intake?
>
> It just don't make sence to me! If you can make smoke, and want more
> power, you want to get more oxygen in there.. IE maybe an NO2 bottle.. but
> only when you are hammering it.. ( to clean up the smoke and get more power)
> anytime its running smokeless its running lean, and you don't need more O2.
>
> Just my .02 cents... :)
>
> Arnie G
>
> P.S. with a turbo you can get more O2 in there, so if you are not
> smokeing, add some propane, but if you are already smoking, it won't be all
> that much help..
>
> ______________________________________________________________________
> 1c. Re: CNG / Propane conversions for diesels
> Posted by: "Collingwood Ted" tedcollingwood@...
> Date: Sat Jan 10, 2009 5:46 am ((PST))
>
> That's another reason to do it on the Rabbit as it NA (no turbo) and you
> need all the power it can give which it no much.
>
>
> ----- Original Message -----
> From: Joseph Hupp
> To: VW-TDI@yahoogroups.com
> Sent: Friday, January 09, 2009 2:05 PM
> Subject: [VW-TDI] Re: CNG / Propane conversions for diesels
>
>
> Hi Tad,
>
> Do not buy a system which injects BEFORE the turbo - otherwise you
> could blow ya turbo to kingdom come!
>
> Have a look at this Australian company's website for information on
> post-turbo propane/LPG injection for diesel engines:
> http://www.d-gas.com.au/
>
> They are the only company in Australia to make a post-turbo LPG/Propane
> injection system!
>
> Joe
>
>
>
>
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