CRD Performance LPG/CNG Diesel Blend Transit Van After 4 years of development and extensive testing on a wide range of cars and light vans of up to 3.5 Tons, we can now offer customers Diesel Blend conversions using either CNG or LPG.

All the development has been carried out by the fuel injection Technical Team at CRD Performance in Bolton, including Eddie Zyla and Mark Howarth, shareholders of CRD Technology Limited .

Photographs of some of our development vehicles; an Audi Q7, a Vauxhall Insignia and a BMW 330D. Click the images for more details.

Development vehicle:
Fiat Grande Punto 1.9 JTD fitted with a Zavoli LPG system on a track day at Elvington.

The patented control unit we’ve designed uniquely takes input signals from a vehicle’s Common Rail Diesel system and outputs control signals that are synchronised with the diesel injectors and relative to the quantity of diesel being injected. These control signals can be used with almost any make of CNG or LPG vapour or liquid system (for example BRC, Prins or Vialle) enabling most diesel engines to run on a blend of diesel and Gas.

LPG Diesel-Blend VW Transporter:
Gerd Van Aaken with his newly converted LPG diesel-blend VW Transporter.


CNG vs LPG – Whats The Difference?

CNG/LPG Tanks CNG is compressed natural gas, the same gas we use for cooking and heating that’s used by most households from the National Grid. LPG is Liquefied Petroleum Gas that’s used also for heating and cooking (where natural mains gas isn’t readily available) and is also sold in over 1400 petrol stations in the UK, commonly for use with LPG converted petrol vehicles.

CNG is the cleaner of the 2 fuels and has a higher octane rating (i.e. its resistance to burn) of 130 – 140 (compared with 105 for LPG), allowing for a greater substitution ratio of gas to diesel. Its availability at present is limited in the UK, unlike the rest of the world, especially Germany, Holland, India and Pakistan where it can be purchased at most fuel stations. With the recent discovery of Shale gas in the UK and the Government’s go-ahead for Fracking to take place, CNG is set to become the new fuel of the future.

Although CNG can be compressed and cooled to become LNG (liquefied natural gas) this is not commercially viable on small to medium cars and vans due to the storage tank costs involved.

LPG is still much cleaner and cheaper than either petrol or diesel and is more readily available in the UK and also has a network of approved installers who are already trained to carry out LPG installations. Although its lower octane rating limits how much diesel substitution can be made, with a good ECU remap, it’s possible to achieve savings that are quite close to that of CNG.

One advantage of using LPG over CNG is the size of storage tank required; LPG is stored in low pressure compressed liquid form (at about 10 bar) and it expands 255 times when released into vapour form, so only a small tank is usually required. CNG is stored as a compressed Gas at over 200 bar using very strong and heavy steel storage tanks; lightweight carbon fibre composite tanks can be used but are much more expensive. Generally, CNG tanks are about 3 times the size of an LPG tank—not usually a problem if being fitted to a van or commercial vehicle.

Any diesel vehicles converted to run initially on LPG instead of CNG can easily be converted to CNG at a later date, fairly inexpensively; the only changes necessary being the tank, supply pipe and reducer.

Ford Transit Diesel LPG/CNG Development/Demonstration Vehicle:
Ford Transit LPG/CNG Diesel Development Vehicle - Under-bonnet Ford Transit LPG/CNG Diesel Development Vehicle - Tanks
Under-bonnet view of the LPG/CNG system LPG and CNG tanks

CNG Cost & Refuelling

At the time of writing, the cost of diesel in the UK averages around £1.45 per litre; petrol is around £1.40 and LPG 70 pence per litre, all including road duty and VAT. CNG costs 75 pence per Kg, plus 25 pence duty and 20% Vat – that’s £1.20 in total. A Kg of CNG equates to approximately 2 litres of LPG (60 pence per litre). Typically, when substituting Gas for diesel about 1.3 litres are used for every litre of diesel saved.

Currently, there are only a small number of CNG filling stations in the UK but that is expected to change in the very near future to fall in line with the rest of Europe.

Small Home-fill overnight filling stations are available through BRC GB, but it is the user’s responsibility to declare usage and to pay duty and VAT (approx. 45 pence per litre).

Affordable industrial filling stations using a small compressor and several storage bottles for fast filling a few vehicles are also available from Preston based company SMP Limited .

Ford Transit Diesel LPG/CNG Dual Fuel Vehicle Filling at CNG Services, Crewe Ford Transit Diesel LPG/CNG Dual Fuel Vehicle Filling at CNG Services, Crewe (filler)
Ford Transit Diesel LPG/CNG Dual Fuel Development Vehicle Filling at CNG Services, Crewe

How It Works

Unlike a petrol engine with spark ignition, which can be converted to run fully on Gas with the petrol switched off, diesel is still required at all times for the Gas to ignite. Diesel engines work on the principal of compression ignition and therefore don’t have spark plugs or ignition coils to ignite the fuel. Diesel is instead injected at extremely high pressures and at precisely the right time, directly into the cylinders, where it is ignited by the extremely hot compressed air.

Diesel LPG Dyno Plot Most of the time, when a diesel engine is running, there is an excess of air inside the cylinders, so to increase the engine speed and power the vehicle’s Electronic Control Unit (ECU) simply increases the amount of fuel injected through the common rail system. Precisely injecting gas behind each inlet valve of the engine’s intake manifold allows a mixture of Gas and air to be compressed in the cylinder on the induction stroke, which is then ignited along with the diesel. This gas/air mixture not only produces more power but also helps the often difficult to burn heavy diesel fuel to burn more fully, release more energy and reduce smoke and particulate emissions.

Power Options

Naturally this method will increase the engine’s power but, because the driver no longer has to push his foot down so far for the same effect, the ECU injects less diesel into the engine resulting in fuel savings. The increase in low down torque allows the driver to select a higher gear sooner or for an auto box to change up sooner. Some owners may even wish to use the Diesel Blend system for performance; during development we often ran our test vehicles in this way and, unlike an ECU Re-Map or tuning box which use extra diesel when driven hard, we benefited by using a cheaper gaseous fuel instead.

If the customer’s requirement is to keep power standard then the Diesel Control ECU can also be programmed to reduce the amount of diesel used by reducing fuel rail pressure. During the engine’s warm-up period, or with the Gas system switched off, the control unit automatically reverts the fuel pressure and engine power back to standard.

Another method used is to re-map the ECU with a programme that is custom-written for each engine type to optimise the blending of the 2 fuels. These ECU files are developed on our rolling road in association with Quantum Tuning , one of the UK’s leading engine re-mapping companies. Their chief file writer, Stuart Banfield, has a very good understanding of LPG, having previously worked with Mitsubishi (UK) on their Dual Fuel Mitsubishi Outlander. Instead of reducing fuel rail pressure the diesel injector opening times are reduced. This method retains the high pressure diesel atomisation and further improves fuel savings and tailpipe emissions (including CO 2 reduction). To allow greater substitution rates of Gas, any diesel injection pilot pulses are removed and the diesel injection timing point altered, but only above engine idling speeds.

Dual Fuel Ford Transit Development Vehicle at Prins Emissions Lab Dual Fuel Ford Transit Development Vehicle at Prins Emissions Lab
Ford Transit Diesel LPG/CNG Dual Fuel Development Vehicle in the Emissions Labs at Prins

Our Ford Transit demo vehicle came from the factory as one of the last Transits made without a Diesel Particulate Filter (DPF) and, using the Quantum Tuning remap method, with either CNG or LPG, it produces no smoke whatsoever—NO SMOKE!

No other Gas conversion system could use this method because, if the vehicle were to run out of Gas, the engine would be stuck in a very low power mode. With the Gas system switched off our Diesel Control ECU reverts to a fully mapped high fuel rail pressure setting, therefore restoring engine power back to standard.

Typical fuel savings range between 10% and 20% and, depend on how the vehicle is driven, the driver can easily achieve such savings.

Diesel Particulate Filter (DPF) Friendly

All new diesel vehicles are now fitted with a diesel particulate filter to help trap and burn off harmful diesel smoke emissions. These filters often fail to reliably work as they were intended. Diesel is a horrible, nasty and dirty fuel which is slow burning, and causes excessive soot (unburnt fuel) – even under normal conditions – to be expelled through the exhaust. The DPF captures and stores all these dirty diesel particulates and, all being well, rids itself of them periodically when the ECU initiates a controlled regeneration process. Regeneration is where the captured soot is re-ignited and burned in the exhaust, creating even more carbon dioxide than the car manufacturers publish in their emissions figures. Most vehicles fitted with a DPF will eventually suffer from a blockage leading to power loss, excessive fuel consumption or total failure, rendering the vehicle undriveable.

Running a diesel vehicle on a mixture of gas and diesel can greatly reduce these particulate emissions and, any soot captured inside the DPF, will be drier and less sooty than it would with diesel alone, making any regeneration much more likely to succeed.


Installation is almost identical to that of any LPG system on a petrol vehicle, with the exception of course that CNG uses different tanks, fillers, pipes and reducers. If anything, the system is quicker and easier to install than a petrol gas system, but still costs the same or slightly more due to the added cost of the Diesel Control ECU. On most vehicles, when carrying out a Gas conversion, reliable ignition live and rpm/tacho signals are usually difficult to locate; the Diesel Control ECU is able to generate and supply these, along with all the injector input signals. Also, since gas is only injected above idle speed, it’s not as critical to mount the gas injector nozzles quite so close to the engine’s inlet valves.

Diesel Control ECU - Universal Dual Fuel System

Technical Information

For those of you who are technically minded and would like to know more about how the system works, click the link below to either view or download the full operator manual of the Diesel Control ECU.

Diesel Control ECU – Operator Manual

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View Manual Online
(Opens in a new window)
Download Manual
(PDF format – 1,950 KB)

Installation Costs

Installation costs at CRD Performance range from £1500.00 plus Vat for a small, easy to install 4 cylinder diesel car to approx £2000.00 plus Vat for a medium-sized 4 cylinder van. Other vehicles and engines, with up to 12 cylinders, will cost more. Please contact us with your requirements. CNG installation costs are similar but with an additional cost for the CNG tank(s) filler, pipe work and CNG reducer, increasing the cost by approx. £500 – £1000. Remapping of the engine management system is optional but, if carried out at the same time as the gas conversion, will often be offered at the cost price (from Quantum Tuning ).

CNG/LPG Installer Dealer Investor Opportunities

Any UKLPG or LPGA installers wanting to become dealers for this unique product may contact Eddie Zyla at CRD Performance or Bert Clegg at CRD Technology for further details. Before enquiring make sure you have fully read and understood the operating manual. If you are unable to understand it or have no knowledge or understanding of Common Rail Diesels, this product may not be for you.

The Diesel Control ECU is compatible with the following Gas system makes:
(and most other sequential multipoint CNG/LPG systems)

BRC, Prins, Vialle, Lima, KME, LPG Tech, OMVL, Bi-Gas, Zavoli, Romano, XLR-8, Tartarini, Landi, Renzo, Eurogas

Investor Opportunity

CRD Technology are currently seeking investment for global expansion.

Please contact Bert Clegg for further details.