Want to know more?   Read on…

Most are well aware that the reciprocating internal combustion engine is simply a highly modified air pump. While many avenues exist for boosting the power output of an engine, most focus on ways to increase the volumetric efficiency of the system. Ported heads, larger diameter exhausts, headers, and bigger throttlebodies all serve to decrease airflow resistance. The greater the amount of air that passes through an engine, the greater the power that engine can produce.

FACT: Every 5°F reduction in temperature increases the density of the air and therefore the power by
            1%.

Why? From chemistry class, we remember PV=nRT, the Perfect Gas Law. This simple equation signifies that the volume of a gas is directly proportional to the temperature of that gas, in this case air. Cold air is denser than hot air. Why is this important to the performance enthusiast? Simple, your engine can ingest more air when it is cooler and denser; more air can be mixed with more fuel, which releases MORE POWER.

For example, a 150hp engine can gain an additional 3 hp for every 10°F the temperature drops. In modern EFI engines, the intake charge is drawn through an intake tube, filter, MAF (or VAF, etc.) and throttle body and into the aluminum intake manifold. The manifold is made up of a plenum and runners that direct the air into the intake ports in the cylinder head. However, during its residence in the intake, the air charge picks up unwanted heat, which increases its volume. By blocking the heat transferred from the engine, ThermoBlok spacers reduce the temperature of the intake manifold and therefore the air entering the engine. This search for cooler air is the reason behind cold air intake tubes, intercoolers, and icing down the manifold between quarter mile runs.

An additional benefit is that cooler air allows an engine to have a higher resistance to knock and ping. The engine computer can then dial in more ignition timing advance and even boost in supercharged applications.

But how do ThermoBlok spacers keep the intake manifold cooler?

Aluminum is a great thermal conductor. As a result, heat is very efficiently transferred from the hot aluminum cylinder head and throttlebody to the aluminum intake manifold. By placing a thermal insulating material between them, this heat conduction can be greatly reduced.

ThermoBlok spacers are made from a laminated phenolic composite with a thermal conductivity of 0.29 W/m*K. Aluminum on the other hand has a thermal conductivity of 150 W/m*K, more than 500 times higher. You must also remember that there is a gasket, commonly steel (20 W/m*K thermal conductivity), placed between the manifold and head. Replacing the 0.025" thick steel gasket with a .250" ThermoBlok thick spacer will conduct an amazing 688 times less heat (yes, that's nearly 70,000% reduction!).

The ThermoBlok spacer material also exhibits high stiffness and compressive strength, can withstand temperatures up to nearly 300°F, and has a thermal expansion coefficient very similar to aluminum to increase sealing capabilities.

Enough talk?   Here are the numbers:

Dyno Results

The following dyno plot was taken from a 1994 Ford Probe GT with a 2.5L V-6 engine. The only modification done to the car between runs was the installation of ThermoBlok spacers.

This plot shows an average gain of 5-7 horsepower and 9-11 ft-lbs of torque across the powerband. Each engine and combination of mods reacts slightly differently, but on average, Outlaw Engineering ThermoBlok spacers result in a 3-5% gain across the entire powerband with peaks as high as 10 horsepower and 12 ft-lbs of torque.

Temperature Results

Temperature data was taken using a CPS T200 temperature sensor with a time constant on the order of 5 seconds. An A/D convertor was used for real time data-logging of the readings into a laptop. The vehicle was driven with a speed of 60 mph. Following the driving test, the engine was allowed to idle for a sufficient time to reach the steady state maximum temperature.

Notice that the temperature difference between the intake manifold and the outside air is the same regardless of the ambient conditions. As you can see, the temperature of the intake manifold reached a steady state of approximately 35° F lower with the ThermoBlok insulators than without during 60 mph cruising. During the idle test, the non-insulated engine was nearly 60 °F hotter.

This means that after idling in the staging lines waiting for a quarter mile run, your insulated engine would have an immediate advantage.

Racing Results

Here's an example: One test vehicle (1994 Probe GT) recorded a best of 15.360@88.469 mph with a 60' time of 2.209 seconds prior to the installation of ThermoBlok spacers. Following the installation, the best run yielded a 15.262 @89.315 mph with a 60' time of 2.282 seconds. The temperature during both runs was 55°F. To summarize, the car was ~0.1 seconds quicker and ~1 mph faster, all with a .073 second slower launch. According to rule of thumb, it would require approximately 5 additional peak horsepower for the trap speed to increase by 1 mph.

Many people spend hundreds of dollars on performance mods of dubious value. We wanted as much data as possible to show that ThermoBlok spacers really worked.

In summary, it was shown that:

1. The intake was 35°F cooler at cruise and nearly 60°F cooler at idle.
2. Engines gain 3-5% power across the power band and up to 10.0 hp and 12.5 ft-lbs of torque.
3. The test vehicle was 0.1 seconds quicker and 1 mph faster in the quarter mile.