[Vwdiesel] Jet A

[Patrick Dolan]

The adjustment on turbines is not so much to make it run qualitatively "better", but to inject sufficient volume to reach the thermodynamic design limits of the engine.  The lighter specific gravity fuels contain less energy per unit volume, similar for unit mass, so the fuel delivery has to be increased as you get "lighter" to maintain rated takeoff power (for which, of course, the aircraft operating manual is written).

The way to do so in a TDI is simply use a programme that allows more fuel delivery, or use various tricks to fool it into thinking it needs more fuel, or to install larger nozzles.  However, there is no need to change back and fourth since these features will simply increase power when you revert back to D2.  We don't have quite the same takeoff documentation and control issues with ground bound TDIs as airplone TDIs do.

----- Original Message -----
From: Justin Bennett <lug1970 at yahoo.com>
Date: Wednesday, December 16, 2009 11:47 pm
Subject: [Vwdiesel] Jet A

> Going to pass on some info concerning Jet A in TDIs.  Have ran 
> about 25 gallons mixed in various ratios thru my 98 Jetta.  Two 
> things I noticed was that there was a noticeable decrease in fuel 
> economy and a change in the way it started.  It wasn't as rattly 
> on start and didn't seem to start as quickly.  Since I was fueling 
> out of 5 gallon jugs I do not have a hard number on what the 
> decrease was.  It was like running super winter blend fuel.  Here 
> is the specific gravity numbers from the back of the Biobore JF jug.
> 
> JP4     6.363 lbs/gal
> Jet A   6.714lbs/gal
> #1 D    6.827lbs/gal
> #2 D    7.060lbs/gal
> 
> On certain turbine engines there is an adjustment for specific 
> gravity so if you were running a different weight of fuel you 
> could change fuel scheduling to make it run better.  Wonder if 
> there is a way to do that on the TDI engines.
> Justin
> 
> 
> 
> 
>      
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