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1998 VW Jetta TDI VO Conversion Installation Thread         Return to Main Page

Dual Tank System                                                                      < 1  2  3  4  5 >

WVO & SVO Compatible

Design and Installation:  Nick Pisca, July 2007


COMPONENTS                                             TOOLS

2 twenty-plate heat exchangers                                      Safety Glasses

1 filter head (fits B2-HPG Baldwin filter, or compatible)             3/8” Drive Socket Set (Metric and Standard)

1 custom under-mount aluminum tank (10.5 gallon capacity)           Phillips + Standard Screwdrivers

2 hydraforce fuel switch-over valves                                 Power Drill

1 17-19 inch HotFox fuel pick-up                                      Drill Bit Set

1 4-7 psi fuel pump                                                   2˝ - 3” Hole Saw

75 ft 3/8” dia fuel hose                                              Brake line Pipe-Bender

10 ft 3/8” dia high pressure fuel hose                               200+ Grit Sandpaper

20 ft 5/8” dia coolant hosing                                         Reciprocating Saw or Hacksaw

2 12V/30A switches                                                   Soldering Kit

4 30A fuse holders                                                   Vice-Grips, Pliers, Channel-Locks

various amperage fuses                                               Wire Cutters

1 temperature gauge                                                   Utility Scissors

25 ft 14 gauge wire                                                   2-ton Hydraulic Jack

10 ft 10 gauge wire                                                    Jack Stands

1 spool 14-16 gauge aluminum uninsulated wire                       Automotive Manual and/or Service Guide

box butt splices, assorted electrical connectors

box 7/16” head bolts w/ nuts

box 1/4” washers

1 roll reflectix insulation

100 pack zip ties

several brass fittings 5/8” and 3/8”

many hose clamps




NOTE: Research Before Converting Your Car!

I’ll assume that you’ve already done your homework on the differences between WVO, SVO, Biodiesel and so on.  If not, you probably shouldn’t be following this thread.  Some of the basics are…

WVO = Waste Vegetable Oil

SVO = Straight Vegetable Oil

Biodiesel = Vegetable Oil with additives


Your car must have a Diesel engine.

Don’t pour untreated Vegetable Oil into your Diesel Tank.

If you didn’t know those things already, visit the many forums and websites devoted to VO conversion. 





Prior to Installation:

I spent a good deal of time under the Jetta before the conversion looking to for extra spaces.  Since the VW is rather small, I wanted to maximize my trunk space by mounting the secondary veggie tank underneath.  Luckily, there is a large open rectangular compartment directly under the trunk.  After some quick measurements, I speculated that a 12” x 23” x 5” volume could work unobstructed, and a 12” x 32” x 5” tank would work, but require some demolition. 



Estimated Dimensions before Installation






Also, I found some space in the front clip to store the 20-plate Heat Exchanger.  I wanted to avoid storing this in the engine compartment, just in case I needed to perform repairs.  This component could be in the way. 

Near the air conditioning unit, there is a void surrounded by plastic.  I didn’t have the heat exchanger yet and hadn’t seen a picture of it, but I suspected that its size would be smaller than the designed space.

Estimated Dimensions before Installation





After massive preparation, I laid out a strategy to convert the Jetta.  This design was the initial plan and did change a little.

Glenn suggested that I move the filter head after the pump, for if the filter clogged, I could burn out my pump.  And since I was using a cheapie fuel pump, it will be weak and susceptible to damage.  Also, we had a back and forth discussion about whether to have a series or parallel circuit spliced into the heater core.  Glenn made a parallel system in his Benz and continued this on his Passat, which was under construction coeval mine.  He set up manual valves so he can shut off portions of the coolant circuit if necessary.  I stuck with a series circuit because Jeff tried the same thing on his Jetta. 





Components – Purchasing and Accumulation

I wanted to make the conversion myself and avoid buying a kit from Frybrid, Golden Systems or PlantDrive.  This required finding all the components on my own.  Since Glenn was building his Passat too, we tried to buy elements in bulk to save money. 

(2) Hotfoxes – I found a ebay store selling 17-19 inch Arctic Fox Hotfox units for 175 dollars.  I offered 300 for two and he accepted it.  This was a good deal considering buying them new is over two-hundred a piece.

(6) 20-Plate Heat Exchangers – Glenn found a Canadian dealer selling nickel-plated exchangers for a reduced rate.  We purchased six, but they arrived rather late (due to international shipping).  We split them three each, with the anticipation of using two per car.  Glenn later installed all three and has been maintaining solid temp.


Accumulative Components Prior to Conversion.


Unit Key:

A: 17-19 inch HotFox                                                                $150

B: 4-7 PSI Fuel Pump                                                               $39.99

C: 100-pack Zip Ties                                                                 $3.99

D: (2) 20-plate Nickel-plated Heat Exchangers                                      $89.90 ea.

E: Filter Head                                                                        $110.00

F: (2) Hydraforce Selector Valves with gasket fittings                             $99.90 ea.

G: (2) 30A Automotive Switches                                                     $5.99 ea.

H: Various Brass Fittings                                                          

I: Teflon Tape                                                                       $1.99

J: 20 feet 5/8” Heater Hose                                                        $13.21

K: 50 feet 3/8” Fuel Hose                                                          $45.98

L: 25 feet 5/32” Vacuum Line                                                       $17.80

M: Custom Aluminum tank                                                            $365.00

Unmarked: Injector Line Heaters (not used in Jetta conversion)                    $48.00


Totals                                                                                $1187.54



Tank Image.


The tank design is rather unique and provides the maximum efficiency of unused space in the 1998 Jetta.  I wanted my conversion to be very clean and have minimal impact on my engine and trunk compartments.  Once I made a basic design, I got quotes from various SoCal metal fabricators, ranging from $600 to $1200 dollars.  Most of these manufacturers deal with high-end hot-rod tanks or industrial-size components.  Luckily, Royal Manufacturing of Santa Ana stated “no project was too small” and quoted my first design at $250.  I was going to leave it at that and install a threaded type HotFox mount to secure the VO pick-up.  Arctic Fox recommends using the A-1721 or A-2060 horizontal adapters, which run over two-hundred dollars. 

I revised the design and detailed it to have breathers, returns and other elements, and most importantly, I created my own horizontal adapter based on the A-2060 specs directly from Arctic Fox.  Royal built the tank in twelve days as I waited for delivery of my HotFox, so I was never sure if the dimensions to which I designed the tank were actually going to work.  But they fit seamlessly.  The new “ear flange,” as the engineer at Royal called it, cost an extra 100 dollars.



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[c] 2007 Nick Pisca . . Waste Vegetable Oil Awareness and Travel .