Gearhead News

August 1, 2021
Can a Diesel Engine Run on Gasoline? Let's Find Out

Diesel engines and gasoline engines are so fundamentally different that it’s possible to do real damage simply by filling up your car with the wrong fuel. Converting a diesel engine to actually successfully run on gasoline is thus naturally a huge job, requiring major engineering changes to the very heart of the motor. However, YouTubers aren’t easily deterred, and Garage 54 did the hard yards required to make an old diesel minivan engine burn gasoline instead.

The motor in question is a Toyota 2CT turbodiesel engine, yanked from a minivan and left to sit for a year before the project began. Vlad, the star of Garage 54, starts by highlighting the work required to convert the engine. Diesel engines use compression ignition, and don’t have sparkplugs, so these need to be installed into the combustion chamber somehow. The high-pressure diesel fuel delivery system is also not suitable for delivering gasoline to the cylinders. Most difficult of all is changing the compression ratio. The diesel engine has a 23:1 compression ratio, which would quickly lead to detonation if fueled with gasoline. This needs to be reduced closer to 10:1 if the engine is to run safely on gas. 

YouTube/Garage 54
What’s a little fire between friends?

The first step taken was to disassemble and clean the engine to investigate the possibilities. After measurements of combustion chamber size and looking at engine specs, it’s clear that simply throwing in a few extra head gaskets will only drop compression to around 16:1, nowhere near low enough. Instead, the team decide to go the whole hog and machine down the pistons by 4mm to get the compression ratio down low enough. 

For spark, the preignition chambers and fuel injection ports are instead machined to accept sparkplugs from above. The team also note that the diesel injection pump runs a drive gear identical the camshaft gear. This allows the pump to be removed and replaced with a distributor from a Lada Samara, which is driven at a 1:1 ratio with the cam. With spark sorted, the team turned their attention to fuel and air. Old Lada intake manifolds were cut up and modified to suit the Toyota engine, and fitted with an old carburetor to supply fuel. Simple enough, and it does the job.

Amazingly, with the engine hanging from a stand and lashed up with an old battery and given a little fuel, it starts up first time. It even responds to throttle and revs up as you’d expect. It’s pretty rough and ready, particularly at low RPM as there’s no flywheel to smooth out the combustion pulses, but it is undeniably a running gasoline engine.

YouTube/Garage 54
Pistons were machined down to lower the compression ratio.

YouTube/Garage 54
The universal expression of “IT’S WORKING!”

We’d love to see the engine on a dyno to learn what it’s putting out in terms of horsepower and torque. Comparing the output to a contemporary carbureted gasoline engine would be fun. Hopefully the motor is dropped into a body and we can see the formerly-diesel engine ripping some skids soon. 

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