Testing a V8 Mustang engine on sustainable fuel

They’re busy evaluating the effects of sustainable fuel on their engines, because the Ken Miles Cup is set to be the latest Goodwood race run exclusively on sustainable fuels, ahead of the all-encompassing roll-out at the 2024 Revival.

We paid a visit to Mathwall Engineering who have been busy preparing several Ford Mustang engines for the 81^st Members’ Meeting, to watch them fire up an engine for the first time with sustainable fuel.

The fuel in use was S70L, supplied by Anglo American, which the team is expecting to run during the Members’ Meeting weekend, and this was a big moment for them as they made a bold step into the unknown with a back-to-back test alongside a traditional unleaded racing fuel. The engine? A 4.7-litre (289cu in) Ford V8.

With the engine mounted on the dyno, the team ran back-to-back tests, first on their standard 99 Octane unleaded race fuel, and followed immediately by the new sustainable fuel. In both cases, these were ethanol-free.

Anglo’s S70L is what’s known as a ‘drop in’ fuel, the idea being that you can pour this sustainable fuel straight into your tank and be safe in the knowledge that all should run as expected with no adjustments required. According to official figures, the sustainable fuel is ever so slightly denser (by around 0.014kg/l at 15 degrees celsius) with a higher octane (101.4 compared to 99.0), and this test would help us to understand whether those differences would translate into engine performance.

Experiencing the test in person was enlightening, this felt like our first opportunity to properly understand first-hand how these new fuels will affect the racing at Goodwood. The news is good, if you were worried, because on the evidence of this test, almost nothing is going to change.

We say almost nothing, because the sustainable fuel lets off a distinct aroma compared to the standard race juice. It was by no means unpleasant, and perhaps only noticeable within the confines of the dyno lab, but definitely different.

Aside from that, there was absolutely nothing to suggest that the fuel pumped into the engine for the first run was any different to that of the second run. The sound for one thing was equally impressive, you can rest assured the rumble of 30 Mustangs will unabated when the Ken Miles Cup gets underway at Members’ Meeting.

Perhaps more important is the performance, and we’re happy to report there’s no discernible difference there either. In fact the S70L sustainable fuel was delivering exactly the same peak power at a little over 7,000rpm, while the output trace remained consistently within 1.5PS between 3,500rpm and the redline.

The one thing that’s difficult to predict from these tests if the impact sustainable fuels will have on reliability, but there are clues we can take from this to suggest all is well. Routine checks of the engine’s internals showed there was no excessive wear to the cylinders or spark plugs, nor any increase in carbon build up. If there had been, concerns would have been raised for the longevity of the engine, and indeed its power performance. As it was, the team were confident that from this initial testing there was no cause for worry.

In the case of this S70L fuel, the move to sustainable fuels looks as though it should prove be fairly straight forward for the majority. The team did however carry out an identical test with another alternative sustainable fuel (FAS) with a far higher oxygen content that did require an adjustment to the carburettor in order to run safely, so discretion will be advised for individual teams to ensure they’re running a fuel that works best for their engine.

Clearly not all sustainable fuels can be described as ‘drop in’ alternatives to traditional race gas, but there is confidence within the industry that these fuels can be integrated with relative ease into historic motorsport. We’ve already seen plenty of examples of sustainable fuels in use at Goodwood, the 2023 Fordwater Trophy was the first fully-sustainably-fuelled race on the Motor Circuit, and it certainly looks as though teams all over the world are on working on the right track to make the Ken Miles Cup, and the upcoming Goodwood Revival, a huge success.

Following the test, the team at Mathwall said: “From a performance point of view it's very consistent, within a horsepower and a half with each run we've done, it gives the output that we'd expect from that engine.

“We were able to give it the same ignition timing, get the same fuelling out of it, so from what we can see it's a drop-in fuel.

“With that particular blend of fuel, we wouldn't have to tell our customers to change anything about their engine they've got currently. So we feel confident recommending it to people racing that weekend.”