12/11/2020
Which Racing Fuel is the right fuel for your drag car or drag bike?
Every day I receive enquiries from customers asking which fuel we recommend for their naturally aspirated drag car or drag bike. There is a lot of information required to make a fuel recommendation, however most people believe the static compression of their engine is all the information I need to know.
This tech article is a general information article, aimed at our customers directly, as most engine builders/tuners should know all of this information already.
If you have a naturally aspirated engine and would like a racing fuel recommendation and some professional advice about which ETS Racing Fuels could suit your engine configuration, please provide us with the cranking cylinder pressure of your engine.
Whilst the static compression of an engine is an important parameter for choosing an appropriate racing fuel, to be precise, the cranking cylinder pressure of an engine is actually a more important piece of information for us.
Every engine has a static compression ratio, and every engine has a dynamic compression ratio, however the value that is the most easily accessible to most people, and cost effectively, is the actual cylinder pressure created by the engine.
You can get this value by disconnecting your coil, removing all the spark plugs, and fitting a pressure gauge to one of the cylinders, and cranking the engine over, without firing.
Cylinder pressure changes throughout the rev range, from when the engine is cold to hot, because of the sealing capability of the piston/rings, valve sealing and also depending on how fast you crank your engine. So it is not always a precise and absolute value, but it at least can give us a baseline of how much squeeze the engine is placing on the air fuel mixture in a given engine.
This is an important value to understand when making a fuel recommendation In most cases customers are not able to give us the dynamic compression value, which would be an even better value, and therefore the Cranking Cylinder Pressure (CCP) value is the next best thing.
There is a formula for calculating the dynamic compression of an engine, and you can fit a dynamic compression sensor to an engine, but these sensors are so expensive that traditionally only car manufacturers have them on their dyno’s across the world.
The dynamic compression of an engine will also change with increases in RPM of any engine, however as a starting point, the cranking cylinder pressure is a baseline piece of information that anyone can obtain, to help us better understand what type of fuel could be best suited to your engine.
In simple terms we are trying to understand how much pressure the air/fuel mixture is being squeezed inside the engine during the compression stroke.
We have to work with whatever information and data we can get, in order to give a professional fuel recomendation, so a cranking cylinder pressure test on an engine is able to be done by all dyno shops, and car owners, at home on their own cars, with a pressure gauge.
Racing Fuels are very often marketed as “suitable for engines up to 15:1 compression, or good for up to 1500hp engines”. Every engine is different, and understanding the engine, and more importantly, knowing the strengths and limits of racing fuels is important, in order to make the best recommendation for a customer.
In simple terms the static compression is just the ratio of “squeeze” that is mechanically applied to the air/fuel mixture prior to spark/combustion. So a static compression of 14:1, meaning 14 parts of air is being squeezed into an area equivalent to one part.
However in a 4 stroke engine we have inlet valves and exhaust valves open and/or closed at different points of the compression stroke, depending on the camshaft being used in a given engine. This is the thing that has a big impact on the final dynamic compression (or squeeze) an engine really has.
A lot of people don’t realise that you you can have 4 pushrod V8 engines, all with 14:1 static compression, however if all 4 engines have completely different camshafts fitted to them, they can produce completely different dynamic compression values. Meaning they will also have completely different cranking cylinder pressure values, and potentially be better suited to different racing fuels for optimum performance and engine safety.
Lets say we have four 350 chev engines, all with a static compression of 14:1, but with different camshafts. Engine 1 produces a cranking cylinder pressure of 160 psi, engine 2 - 180 psi, engine 3 - 200 psi, and engine 4 produces 230 psi cranking cylinder pressure. The higher the cranking cylinder pressure, the greater amount of squeeze being applied to the air/fuel mixture. Therefore the higher the cylinder pressure, the greater detonation resistant fuel you will need to use, to prevent detonation, and keep your engine safe. Importantly choosing a racing fuel that is better suited to your engine, will give you better value for money, and importantly a better performance result from your given racing fuel.
The fuel I recommend for engine 1 could easily be a 102 octane ETS unleaded racing fuel, whilst engine 4 would need a higher detonation resistant fuel like Xprodrag2.
Unfortunately a lot of people might do a fuel comparison between 2 fuels on engine type 1, and fuel A might outperform fuel B.
However if you did the same fuel comparison between the same 2 fuels on engine 4, you may get a completely different performance result from the same 2 fuels.
On engine 4, Fuel B might outperform Fuel A?
We have found exactly this during our R & D testing over the years.
So just because a friend of yours is using a particular fuel in his engine, which is a similar engine to yours, it does not always mean if you use the same fuel in your combo, that you will get the same power gains as he did with the same fuel? You may get more power, you may get less power, or you may need to use another fuel that better suits your engine combination.
There is a lot of engines out there that have a high static and dynamic compression, producing a cranking cylinder pressure in the 250-280 psi range. These type of engines require a very high detonation resistant fuel, so normally the fuel options for these types of engines is limited to the really high spec racing fuels.
Best example is the ETS Racing Fuel called Xprodrag2. We have done a lot of testing in Australia with this fuel against some of our competitors best unleaded fuels.
In pushrod V8 engines with up to approx 220 psi cranking cylinder pressure, the Xprodrag2 fuel was around the same as our competitors best unleaded fuels. In some engines Xprodrag2 was 3 or 4 hp better, in other engines it was 3 or 4 horsepower less.
However as soon as we compared the same 2 fuels in a 230-240 cranking cylinder pressure engine, Xprodrag2 was 15-20 hp better than our competitors fuels.
This is the very reason why we nearly always specify the cranking cylinder pressure of an engine when I post dyno testing results on social media, specifically to ensure we are not providing information that is misleading to our customers, and potential customers.
Every engine is different, and choosing the right racing fuel for an engine is not easy, but we rely on all of our own testing, knowledge and experience, and testing results from all of our technical partners across Australia to build our knowledge about all of the ETS fuels, which in the end, is to the benefit of our customers.
I fully understand and respect that other racing fuel companies/distributors/suppliers may do things differently, however I hope this explanation can help people understand the technical reason why we are asking you to supply us with this information.
It is also information you and your engine builder should know, in order to determine what type of fuel must be used in your engine as a minimum, for safety.
Understanding your engine is step 1, the more information we can have about your engine, like cranking cylinder pressure, the more precise we can be with a fuel recommendation.
We are well aware that many of our competitors market their fuels purely on octane numbers, comparing RON and MON values, and to be honest it appears that a big part of our market here in Australia still believe the octane number value determines which fuel is better.
This is definitely not the case, and whilst octane number values are an important parameter when considering a fuel, it is definitely not everything, like some will have you believe.
With the Australian ban on leaded fuels taking effect in July 2019, there appears to be a lot of surprise from customers that drag racers are going faster, and just as safe, down the track on far lower octane unleaded fuels (and in many cases far cheaper), compared to the high octane leaded fuels they have been running for the past 10-20 years.
ETS Racing Fuels are based in Europe, and what a lot of people are not aware of, is that most big World Championship racing, like Formula 1, Moto GP, World Superbike Championship, World Rally Championship etc etc, have all been using unleaded fuels with a maximum of 102 octane for well over 15 years?
So before you ring me or anyone of our distributors or tech partners wanting to know which fuel from the ETS portfolio we recommend you use, please take some time to get the cranking cylinder pressure information yourself, or get your engine builder to confirm to you what it is.
This way we can offer you a product that allows you to extract the most power, consistency and safety for your engine combination.
Distributors and contact information can be found on our website at www.racefuel.com.au
