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Super Coupe Club of America > SC Literature > CW Report on SC Intercooler Upgrade

by Charles Warner
ChasW500@aol.com

Enlarged SCPI Blower Top & Intercooler Evaluation Report

I recently received my long awaited Enlarged Super Coupe Performance (SCPI) Blower Top and upon opening the box I became quite convinced this modified top is the ticket. The enlarged top came with everything needed for a successful installation; bolts, flange sealer, anti-seize and instructions that include, as one might expect a splash of Bill's humor. There is nothing humorous about this blower top however; it's serious business. The only part that is not included is the Spanner nut wrench which can be purchased from the SCPI for $49.00.

The stock blower top is severely restricted where the air passage transitions from the square top area to the round section just before the intercooler collar nut. The reduction is 50% in this area. By comparison the raised and enlarged blower top from the SCPI maintains nearly full cross sectional area through this region and is smooth and aerodynamic.

I started the technical evaluation by measuring the pressure drop between the square section of the blower top and the intercooler tube by tapping into the castings and measuring the pressure difference with a differential pressure gauge. The stock blower top measured 2-PSI pressure drop at 6000 RPM! This pressure drop, caused by friction, heats the incoming air causing it to expand and reducing the available air mass. Also, because the blower sees a higher pressure it must do more work reducing available horsepower to the wheels. By comparison the Enlarged Blower Top from SCPI measured less than a 1 PSI pressure drop, quite an improvement.

Part two of the evaluation was an acceleration test. The improvement is quite remarkable. My SC with the stock exhaust and stock blower top accelerated from 20 MPH to 55 MPH in 4.17 seconds. With the 3 1/2 inch exhaust this time was reduce to 3.80 seconds, a .37 second improvement. The Enlarged Blower Top from SCPI reduced this time to 3.57 seconds a .23 second improvement! This kind of power improvement is not easy to come by in most applications, but lucky for us this part is available from SCPI. The enlarged blower top from the SCPI is a real power builder and a necessary addition to any performance minded SC owner.

SC Intercooler Evaluation Report:

The Thunderbird SC sports two power making devices, a Supercharger and an Intercooler. The idea of the supercharger is to force more air into the engine than a normally aspirated engine could, thereby allowing more fuel to be burnt and producing more power. The disadvantage is that air gets hot when compressed. As hot gasses expand there are fewer air molecules per cubic inch resulting in less air to burn fuel, hence less power produced. This is where the intercooler comes in. The intercooler cools the supercharger's hot gasses causing the air to become denser, burning more fuel and producing more power.

Over the last few months I measured the air temperatures and pressures between the supercharger and the intake manifold, this article reports my findings.

The supercharger and intercooler from Ford work quite well, but as one might expect there is room for improvement. At a normal 60 MPH to 80 MPH cruise the air exiting the supercharger is 160' F to 170' F when the ambient temperature is in the mid 50's. Under full throttle I measured a maximum temperature of 404' F at 6000 RPM! These temperatures were much higher than expected and demonstrates the need for an intercooler. Power increases 1 % for every 1 degree F of air temperature reduction. In this case an intercooler capable of reducing air temperature from 404' to 55' would improve power by roughly 35%. This represents the maximum benefit one could expect from an intercooler when running 15-PSI boost.

How good is the stock SC intercooler? See the chart below. Note; exit air temperature measured while accelerating under full throttle.

Ambient cooling air velocity measured at various vehicle speeds is displayed in the chart below. Note air speeds were too slow to measure, with my equipment, when vehicle speeds were below 50 MPH.

What I learned by making these measurements. First, the intake system including the intercooler, supercharger and intercooler tubes are heated by the engine and are quite warm even when the engine is under Very light loads. Between 60 MPH and 80 MPH the intercooler's exit air temperature hovers around 100' F, even with light throttle. Around town and in stop-and-go traffic this temperature creeps up to 112' or so with the ambient temperature at 55'. Under full throttle this temperature is much higher. Referring to the first chart you can see that the exit air temperature rises only slightly as the car accelerates from 0 MPH to 50 MPH. From 50 MPH to around 80 MPH the intercooler's exit air temperature begins to rise as the intercooler's mass continues to absorb heat. From 80 MPH and up the intercooler's exit air temperature begins to stabilize since the vehicle speed is high enough to force significant quantities of cooling air through the intercooler, extracting heat from the air charge. Note that at 100 MPH there is three times as much as air moving through the intercooler as at 60 MPH.

Next I installed the intercooler fan from the SCPI and saw a significant improvement. With the fan running and the car parked the ambient air moving through the intercooler has a velocity of 4.5 MPH. Although this is not very high it is enough to make meaningful improvements. I noticed a reduction in all temperatures throughout the system. At a 60 MPH to 80-MPH cruise the intercooler's exit air temperature was only 67' compared to 100' without a fan. Around town the exit air temperature with a fan rose to only 75' compared to 112' without a fan. Also observed was a reduction of supercharger air.

Temperature from around 175 degree to 123 degree at cruise speeds. This might seem a little odd at first but is explained by the fact the SC has a supercharger bypass which under no boost conditions circulates air from the intercooler back to the supercharger's intake. This cool-air cools the supercharger and tubing.

Below is a chart showing the improvement using an intercooler fan under full throttle acceleration.

On the average this is an improvement of about 30' that translates to about a 3% improvement in power or about 10 HP, not bad for a $90 part.

Finally, I measured the pressure drop across the intercooler and again found room for improvement. At full throttle and 6000 RPM I measured 3.5-PSI drop across the intercooler, not good! The reason, the SC intercooler is much too small, at least for high RPM operation. Spearco recommends designing an intercooler with a pressure drop of 1-PSI or less. What this means is the supercharger is working much harder than if the SC had a larger intercooler. If you read 12-PSI boost on your boost gage the supercharger is really pumping out something like 15.5-PSI ! This requires extra HP to drive the supercharger and is part of the reason I measured temperatures from the supercharger as high as 404 degrees. According to the numbers there is something around 50 HP improvement possible by going to a much more efficient and larger intercooler. I plan to design a high flow intercooler system for my SC using a large Spearco (SCPI) intercooler. Those of you out there who are handy and have the need for speed can do the same. Have fun!

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Document Last Modified: 07/29/04 03:33 AM
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