Archive for category: Technical

Have you ever wondered what the green coating is on the skirts of some of our Cosworth pistons? If you have, then you are not alone! The coating is actually a fluoropolymer material that has the tradename Xylan, and Cosworth have been using this coating for a number of years on a wide range of parts, and not just the piston. Oil pump and scavenge pump bodies also received the Xylan treatment to help prevent wear from rotors.

Not all Cosworth pistons have this coating – pistons from earlier engines like the BDA, for example, were designed without any skirt coating. But the increases in piston speed in their race engines meant that some form of coating was necessary to help prevent scuffing of the skirts against the cylinder bore walls.

In the early ’90s Cosworth started to coat the skirts on pistons from several different race engine categories, including those destined for Formula 1 like this one from the race-winning HB engine (the coating also looks great when etched with the driver’s name!). Cosworth soon started Xylan coating nearly all of its race and high performance engine pistons, including  the ones we sell today for the YB engine.

What is Xylan?

Xylan was developed by DuPont in 1969, primarily for kitchenware utensils as an alternative to Teflon. Its excellent wear properties meant that it was soon adopted by the automotive industry, where it found its way into numerous different applications.

Xylan is in effect a composite material comprising of a dry film lubricant contained in a matrix with high-temperature organic polymers. This creates what can be termed as a plastic alloy that has excellent surface characteristics and is easy to apply. Xylan has a very low coefficient of friction, so its perfect for the interface between the skirt and the cylinder bore. It also provides exceptional wear resistance, and quite often Cosworth would strip engines down and see that the Xylan coating was completely unmarked. This is in part due to another benefit of Xylan – it has excellent surface adhesion.

The Cosworth Process

As with any coating, good preparation of the substrate surface is vital. In the case of pistons, the skirts need to be completely clean and free of any oil. Once cleaned, the skirt area is masked off with special tape which can simply be peeled off after coating.

The piston xylan coating is then sprayed on in one of Cosworth’s special custom-made spray booths onto the skirt. Each pass of the spray adds around 5 microns, so the thickness can be carefully built up to the required level. Most piston skirts only need a couple of passes to get the thickness up to the required level of between 6 and 12 microns.

The pistons are then left to dry – normally this can take 24 hours. Once dry, the pistons are good to go, with no other treatment necessary.

If you’d like to know more about the Xylan coatings that Cosworth use on piston skirts then get in touch.

A number of Cosworth pistons have what Cosworth refer to ‘piston anti-detonation bands’, but what actually are they? The term anti-detonation is perhaps a bit of a misnomer, as these bands don’t actually stop detonation. Instead, these bands mitigates the effects of detonation.

Understanding Detonation

Before we take a closer look at these bands, what actually is detonation? It’s a phenomena that is commonly mentioned in the world of high performance engines, but it does sometimes get used incorrectly. Detonation is broadly defined as unwanted or abnormal combustion. It occurs when both the temperature and the pressure in the unburnt mixture of air and fuel exceeds a critical level.

In a normal combustion event the spark plug will ignite the air/fuel mixture inside the combustion chamber. This happens before TDC whilst the piston is travelling upwards. The ignition of the air/fuel mixture creates a flame front that spreads outwards, igniting more of the mixture and leaving behind the burnt gases.

However, in certain circumstances when the temperature is hot enough, the unburnt mixture that is furthest from the spark plug (towards the wall of the cylinder) will ignite before the flame front reaches it. This unwanted and uncontrolled combustion can happen almost instantaneously, setting up strong pressure waves that hit the walls of the cylinder. These shock waves create the distinctive pinging noise that can be heard and indicate the presence of detonation.

Cosworth Anti-detonation Bands

In the early ‘90s, one step that Cosworth took to reduce the effects of detonation was to introduce anti-detonation bands. These grooves are located above on the top land above the top ring groove. They are typically around 0.2 mm deep and 1.25 mm wide. Most pistons will have two, three or four of these grooves, depending on the height of the top land.

But these shock waves can also be extremely destructive – they can inflict damage to the piston crown and in particular to the area around the top land. If detonation is severe then ultimately the piston will be irrevocably damaged, with the potential of engine seizure.

There are a number of Cosworth pistons that have anti-detonation bands, ranging from those for the YB through to some of the more recent Formula 1 engines. Basically, any engine that will experience high cylinder pressures will benefit from the usage of anti-detonation bands.

The aim of these bands is to protect the top ring by disrupting any high-pressure pulse waves from detonation. The volume within these grooves, although small, allows a space for additional atomisation of the fuel and air mixture. When detonation occurs, this extra space provides an outlet for the shock waves.

These bands also bring about a couple of additional benefits. Firstly, they can prevent the build-up of carbon above the top ring which would otherwise cause the ring to stick in the ring groove. Secondly, they reduce the amount of contact between the top land the cylinder bore wall. This makes them very beneficial at high engine speeds and piston temperatures. Hence they are also occasionally referred to as “contact reduction grooves”.

The introduction of anti-detonation bands by Cosworth was another example of their experience and understanding of internal combustion engines. Indeed, when owned by Vickers, Cosworth actually patented their anti-detonation band design in the US, take a look here : https://patents.justia.com/patent/5267505

Want to know more about the range of  Cosworth pistons that we supply? Then get in touch via our Contact Us page.

Turn your volume up to 11 and sit back and enjoy 90 seconds of pure, unadulterated noise in this Cosworth Formula 1 engine test as a CA2010 engine is pushed through its paces on Cosworth’s transient dyno at speeds of up to 18,500 rpm.

The Cosworth CA engine represented a pinnacle in the design of high-speed naturally aspirated engines for Formula 1 racing. Calling on over 50 years of experience that dated back to the legendary DFV, Cosworth created their most ground-breaking engine ever.

Sadly, in 2010 the engine speeds were restricted by regulation to 18,500 rpm, but that didn’t stop the cars of that era sounding amazing.

The Need for Speed

In the ear-splitting ‘90s and 2000’s, engine speed was THE metric that Formula 1 engine manufacturers wanted to push to the limit. In a naturally aspirated engine, the goal is to get as much fuel and air into the combustion chamber, and the best way to do this is to run the engine as fast as possible. Unlike power figures, engine speed is something that rival competitors can measure from the side of the track, using audio recording equipment.

It is generally acknowledged that BMW were the first F1 engine manufacturer to break the 19,000 rpm limit in 2002. Toyota soon leapfrogged their fellow German rivals, reaching 19,200 rpm in 2005 despite the introduction of rules to increase engine mileage. These regulations caused a brief respite in the push for speed, but by the end of the V10 era in 2005 the entire grid was running at 19,000 rpm.

Switch to V8 Power

In an attempt to curb engine power, the FIA mandated a switch from 3.0 litre V10s to 2.4 litre V8s in 2006. However, this had little or no effect on the push for speed. Cosworth’s Bruce Wood explained how they did this to Race Engine Technology as part of their exposure on the CA . “To go faster you just have to keep making the bore bigger and the stroke shorter and sort out your valves.

“While developing the TJ we did tests on our single cylinder rig of 96, 97 and 98 mm bores – it was all about higher speed. We were considering a bigger bore and bigger valves and a compound valve angle before the mandatory switch to V8s was brought in. We had thereby established that combustion was OK with the 98 mm bore (the maximum permitted in 2006), so there was no reason not to move to it…”

In 2010 Cosworth returned to Formula 1 with the CA2010. By this time the rules had necessitated a cap in speed of 18,500 rpm. Nevertheless, the cars still sounded incredible, and drop in speed didn’t prevent engines like the CA2010 from reaching power figures of over 775 bhp.

Keeping It Together

20,000 rpm is a huge achievement – as this Formula 1 engine test video shows, even 18,500 rpm sounds terrific, but running at these speeds results in a number of engineering headaches. First of all, the inertia loads on the moving components roughly increase with the square of the speed. So a jump from 10,000 rpm to 20,000 rpm might be double the speed but will result in a quadruple increase in inertia loads.

The second problem with increasing engine speed is that there is a corresponding increase in vibration. This was compounded with the switch from V10 to V8 engines in 2006. A V8 engine like the CA equipped with a flat plane crankshaft will naturally have out-of-balance vibration in a horizontal direction.

Bruce Wood gives a further insight into the problems that this horizontal shaking of the engine would cause on the CA. “When we first started running the CA, the scavenge pumps, which are held onto the sump with horizontal bolts, would fall off. Those are 8 mm cap screws, the heads of which snapped off because of the unbalanced force, which is why our scavenge pumps are now secured by Multiphase bolts!”

Torsional Control

One other problem to resolve before unlocking 20,000 rpm is torsional resonance of rotating components like the camshafts and crankshaft. Torsional resonance has always been an issue in Formula 1 engines – Keith Duckworth had to resort to flexible compound gears to keep the gear drive intact in the DFV in 1967. Fast forward 4 decades, and double the engine speed, and the torsional problems become a whole lot worse.

“In terms of the torsional vibration inside the engine, we knew what we were up against, which is why the CA has far more damping devices in it than our previous V10 engines.”, says Wood. “We have a ‘compliant’ gear train that has been in our Formula One engines for years, then in addition (to two dampened compound gears) the CA has compliant quill drives within each of its two auxiliary drives, a big viscous damper on the back of the crankshaft, viscous dampers on the back of each camshaft and friction quill dampers in the front of each camshaft. That means in total it has 13 dampers – 14 when fitted with KERS.”

Fancy Owning a Piece of History?

We have now started to stock parts from Cosworth’s TJ and CA engines that can be displayed for all to see. Just keep an eye on our Memorabilia section of our on-line shop to see what’s currently available. Each part can be bought directly from the website shop and delivered straight to your door. And then just imagine these components being used in a 20,000 rpm Formula 1 engine!

Have you ever wanted to take a peek inside a Cosworth Formula 1 engine? And did you ever wonder how these engines were capable of reaching speeds of over 19,000 rpm, producing 900 bhp?

Well, if you did, then we hope you’ll like this video that we made showing the inside of one of these high-revving monsters. Codenamed the TJ, this is the engine that was first used by Jaguar Racing in 2003. The team continued to use this engine when they morphed into Red Bull in 2005. It also saw active service powering the Jordan and Minardi teams in 2004 and 2005, respectively. Its final year of racing was in 2006, when Torro Rosso (formally Minardi) ran the engine against the V8’s.

Last of its Era?

The TJ was the epitome of the “anything goes” regulations from that era. Devoid of rules that restricted the number of engines that could be used by each driver, the emphasis was very much of extracting the maximum out of each engine in just one session or race. It wasn’t uncommon back then for teams to get through over six engines in one weekend (and that’s not allowing for unscheduled engine changes!). As a result, engines like the TJ were designed with performance over reliability in mind.

Midway through the life of the TJ, rules aimed at extending engine life started to creep in. In 2004 the FIA introduced the “two race” requirement that each engine had to attain. Engines like the TJ that were designed for outright power and performance had to be re-engineered to last longer. In addition, restrictions in later years on low density materials plus minimum weights and centre-of-gravity heights meant that the lightweight features seen on the TJ became redundant in subsequent engines.

So grab a cup of tea and see inside the last of the “anything goes” Cosworth Formula 1 engine masterpieces!

Modatek are pleased to be able to help keep these engines alive for historic race series and demonstration events. If you need assistance then get in touch.

In this technical feature, we’re going reveal some oil pump design secrets! A perfectly-working oil pump is vital to good engine health. If the oil pump starts to fail, the oil pressure will drop. And when the oil pressure drops too much, the end result can be catastrophic, such as seized mains or rod bearings.

Oil pumps are termed as positive-displacement pumps. The rotors within the pump move to create an open void that expands with movement and the expanding void is filled with oil. As the rotors move around, they take the oil with them, and the void then compresses, forcing the oil out of the rotors.

Internal and External Pumps

Broadly speaking, there are two types of positive-displacement rotary pumps – internal rotors and external rotors.

In an internal rotor pump, an inner rotor with external teeth runs inside an outer rotor with internal teeth. The inner rotor will have one less tooth than the outer rotor, and the two rotors run on fixed eccentric axis.  As the two rotors rotate, the volume created between the meshing teeth expands and contracts the oil.

Most internal rotor pumps need to have a crescent shape in the space under the inner rotor. This crescent separates the two rotors, creating a seal that stops leakage from the high pressure volume back to the low pressure volume. However, this crescent is eliminated in a gerotor pump like our popular Cosworth YB 2WD oil pump (gerotor is short for generated rotor). The gerotor design does away with the crescent, creating a compact and simple solution.

External rotor pumps consist of two identical rotors running side by side. As with the internal rotor pump, one gear drives another, and oil is moved through the rotors by the expanding and collapsing void when the teeth mesh. Usually the two rotors have parallel teeth, but in other applications the teeth can be angled in a chevron pattern.

Rotor Teeth Profile

Did you know that the profiles of the inner and outer rotors in an internal rotor pump are anything but simple curves – in fact, the profiles belong to the “trochoid” family of mathematical curves.

If you’re old enough to remember playing with a Spirograph toy, then you’ll remember the curve created by pushing a pen through a hole in a small cog and then rotating it inside or outside a larger toothed disc. These curves are actually called epitrochoids and hypotrochoids, and these curves are the starting points for the design of the rotor profiles. When the oil pump rotors are first designed, the chosen curves for the rotors are carefully adjusted to reduce the build-up of stress concentrations in the roots of the profiles, and to also provide good resistance to debris without compromising volumetric efficiency.

Its not just the profile of the tooth that determines the how the pump will behave. The other important design consideration is the amount of eccentricity between the inner and outer rotors. This eccentricity influences the shape of the rotor profile.

Teeth Numbers

The number of teeth chosen will have a major impact on pump performance. Fewer teeth mean that the overall diameter of the pump can be smaller, which in turn makes it easier to package in the engine. Fewer teeth also result in a reduction in power loss for a given flow rate, but the downside is that they have to run at a higher rotational speed, which can increase wear.

On the other hand, more teeth will give fewer pressure fluctuations and hence a smoother overall oil pressure. The fluctuation is sometimes referred to as pressure or flow ripple, and is an unwanted side-effect of any positive-displacement pump. The effect of pressure ripple is mechanical vibration in the oil circuit in the engine, which can damage components such as oil hoses, seals, and bearings, so any measures that can minimise pressure ripple are likely to be of great benefit.

Rotor Clearance

The clearance between the rotors themselves and between the rotors and the end faces will also have a significant effect on pump efficiency.

Reducing these clearances will have a knock-on reduction in leakage of oil across the end faces from the pressure side to the suction side. However, not enough clearance can cause the rotors to bind and jam up, plus debris will become trapped and then damage the pump.

Fit Genuine Parts!

The rotor profiles and clearances in our oil pumps have been carefully designed by Cosworth engine designers to match the requirements of the YB engine, and that’s why we believe that its important to fit genuine Cosworth parts like these. If you’d like more information on the Cosworth YB oil pumps that we stock and sell then please get in touch via our Contact page.