How Hot Does My Exhaust Get?

Formula 1 engine red hot

In short, the highest temperatures that an exhaust manifold or exhaust pipe should ever reach would be approximately 850°C (1,600°F). As a guide, metals will start to turn red at 500°C and be a dark cherry red at around 635°C (1,175°F).

The hottest parts of your exhaust system will be either a bend in an exhaust pipe right next to the cylinder hard or around the catalytic converter.

Temperatures naturally increase as RPM or the engine work load increases. This is when the engine is consuming the maximum amount of fuel and producing the most amount of torque or horsepower.

Tests on the exhaust system temperatures of typical road cars ranged from 120°C (250°F) at 50kph (30mph) up to 550°C (1,020°F) at 112kph (70mph).

Red Hot Motorcycle exhuast pipe

There are 3 ways to prevent damage to nearby components under the above conditions:

  • Insulate the exhaust pipe to keep the heat inside the pipe
  • Place a reflecting barrier with an air gap between the exhaust pipe and the rest of the engine bay and its components
  • Add reflective and insulating materials to objects that could be damaged by the radiant heat coming from the exhaust pipes or manifold.

We typically use exhaust wraps or tapes and wrap these in spiral pattern around the exhaust pipe or manifold to keep the heat inside the pipes. Tests have shown that exhaust wrap can reduce engine bay temperatures by as much as 50%. These exhaust wraps can be made from fibreglass (starts to melt at 815°C), silica, basalt and ceramic wraps.

Car manufacturers have also caught on to the importance of heat control and most late model cars have embossed aluminium or steel heat shields. These are usually mounted in fresh air approximately 1-2 cm away from the exhaust or exhaust manifold. This air gap helps to carry away excess heat.

Heat sleeves are also now used in many new car engine bays to reduce the chances of heat damage to cables, wiring, hoses and hard lines. These sleeves are usually a lamination of aluminium foil and an insulating fibreglass backing. These sleeves use the reflective ability of reflective aluminium foil to repel radiant heat. The fibreglass backing gives the sleeve strength but also acts as an insulator.

Some heat sleeves use a mylar foil outer layer. Mylar is made from a microscopic layer of foil laminated to an outer layer of polyester resin. This is usually backed with an insulating layer of fibreglass. The polyester outer layer makes Mylar really tough, but it will burn off at around 200°C (400°F). Kool Wrap uses a thicker outer aluminium foil backed by insulating fibreglass. This material is available as a sleeve or in sheet form so that it can be used to insulate car components such as a starter motors or a firewall. The Kool Wrap foil and fibreglass can withstand temperatures approaching 660°C (1,220°F).

Remember that air is actually a great insulator when trapped in small pockets. Air is excellent at convection (electric fan heater) but is a poor conductor of heat due to its low mass. You can see evidence of this in styrene foam or ceiling insulating batts. These two products are designed to trap air pockets and reduce heat conduction. The material acts as a heat block. The heat cannot be transferred through the material. The same applies to exhaust wraps and fibreglass or silica blankets or wraps. The air trapped between the fibres reduces heat conduction.

A good example of trapped air acting as a heat barrier is double glazed windows.

References:

University of Washington: Underhood Surface Temperature Tests: Summary of Published Results

https://depts.washington.edu/vehfire/ignition/autoignition/surftemper.html

 

How To Install Our Latest Kool Wrap Exhaust Wrap Insulation

First, you need to work out how much of our Kool Wrap exhaust wrap do you need.

If you are wrapping smaller diameter pipes up to 37mm (1.5”), use a 25mm wide wrap. If your pipes are larger than 377mm in diameter then choose the 50mm (2”) wide wraps.

A Harley Davidson has larger primary pipes and will typically use 15m of wrap. A 4-cylinder engine will also use 15m while a V8 will require 2 15m rolls.Kool Wrap Titanium Exhaust Wrap on headers

Koolwrap offers its standard range fibreglass insulation wraps in white, natural (cream or tan) and black. If you are racing, then your pipes can easily get red hot and we would then recommend our high temp range of either a Vermiculte coated fibreglass wrap or our Titanium wraps. Our Titanium wraps will withstand up continuous exposure up to 1,800°F or 980°C. The melting point is a sky high 2,500°F or 980°C.

You do not have to dampen your Kool Wrap exhaust wrap before applying as our latest high-tech wraps are more flexible than older style wraps and confirm well to corners.

However, there is no harm dampening the wraps if you choose to. It may help to get a tighter finish and can help reduce the small fibres that come off the wraps and can cause skin irritation. Always use gloves and long sleeves when applying. If you decide to dampen your Kool Wrap exhaust wrap, do not soak the wrap in a bucket. Simply dampen the wrap under a tap or use a spray bottle.

It is easier if you work out approximately how much wrap you will need for each pipe before you start and cut a separate length of wrap for each pipe. This avoids trying to pass a large roll of wrap around the pipes.

Fold over the first 15cm of wrap to avoid a fraying end and to provide a tidy start. Then overlap the first 1-2 wraps to lock it on place. You can also add a stainless steel tie at this point to firmly hold your starting point. Then wrap slowly around the pipes using 5-8mm overlap (1/4”). The overlap will naturally increase on the inside of the bends. Keep tension on the wrap to give a nice tight finish.

You can finish your wrap with a spray paint aerosol can. You could choose a clear or a colour of your choice. This will help to lock down any loose fibres and help prevent liquids and dirt from staining your wrap.

You will initially notice the wrap will smoke when you first start your engine. This will disappear after 15-30 mins.

Formula 1 Exhaust Wrap

F1 Exhaust wrap heat protection
F1 Exhaust wrap heat protection

We are big Formula 1 fans here at Kool Wrap and we were delighted to see Daniel Ricciardo win the Chinese Grand Prix last week.

The Formula 1 teams are notoriously secretive and we rarely see behind the scenes photos of their technology. But we recently came across this photo of an unidentified Formula 1 engine from winter testing and you can easily see that they have used exhaust wraps or shielding to contain exhaust heat temperatures.

Heat management is extremely important in F1. Air intakes for intercoolers, radiators and oil coolers need to be kept to a minimum as they create aerodynamic drag and cost valuable lap time.

Racing has always been a fantastic test bed for new technology. Many previous inventions find there way onto our roadcars such as disc brakes, seat belts and fuel injection.

Today’s Formula 1 engines have reached amazing new levels of efficiency.  If we look at the energy stored in racing fuel (I will not go into how energy is never created, it is just transformed from one place to another) the engine designers job is to convert as much of that stored energy into twisting power. Petrol engines have always been fairly inefficient. When we convert petrol into heat, some of that energy pushes down the piston to turn the crank, but most of that heat energy disappears out of the exhaust pipe or into the cooling system.

A typical petrol engine in a late model car has an efficiency score of around 20%. That means 80% of the thermal efficiency is lost in exhaust gas, friction etc.

Mercedes F1 announced late last year that they have exceeded 50% thermal efficiency. This helps to explain how they can make 900+hp from a 1.6 litre V6 engine!

Advances in heat management have contributed to these efficiency gains. Mercedes have tried to keep as much heat energy inside the exhaust pipes so that it can drive their turbocharger to both create turbo boost pressure but to also generate electricity that can power their hybrid systems.

We will leave Formula 1 engine technology discussions for another blog later this year, but we can expect to see standard roadcars of the future doing a far better job of converting fuel into usable energy.

Kool Wrap Can Prevent Harvester Fires

Kool Wrap prevents Harvester Fire

We had a customer call from Western Queensland and he wanted some wrap to go around a muffler that was causing fires on his harvester.

He said it was common for pieces of dry stalks, crop dust or chaff to gather on the harvester and this was particularly dangerous around exhaust pipes, mufflers and turbo chargers.

In fact, the GRDC (Grain Research and Development Corporation) claim that 7% of harvesters will start a fire EVERY YEAR.

The risk of fire varies depending on the weather conditions, wind direction and the type of crops with Chickpeas being one of the worst offenders.

This problem is not confined to the northern states. We have had reports of similar fire problems in southern states such as Victoria.

Wrapping of hot exhausts and mufflers is one way to reduce the risks.

Other methods include the frequent cleaning of the vehicle with high pressure blowers to reduce the build up of inflammable materials.

Hot Floor in Landcruiser

80 Series land Cruiser Hot Floor

We often hear from 4WD owners complaining about floor heat caused by hot exhaust or mufflers under the floor of the cruiser. This is especially a problem at relatively low speeds or on hot days where heat can build up without cool air flowing under the car.

Australia has some of the harshest climates in the world and when exploring the inland deserts or the northern states, temperatures can exceed 40 degrees C.

Kool Wrap would recommend wrapping the exhaust pipe or muffler with our Exhaust Wrap insulating tape or apply our adhesive insulating material to the underside of the floor. Feedback from customers has been very positive.