Rich Thomson
Registered User
As I have been rebuilding the SC motor out of my 94 I have some thoughts I wanted to throw out there about the intake and supercharger IC setup.
First I wanted to talk about air flow. Air flow through a 2.5" pipe is pretty much constant. Just like our favorite topic of exhaust flow through a mandrel bent vs. compression bent pipe. Air flow is reduced through a compressed pipe.
If we believe static air flow is reduced when it is compressed by a smaller diameter then we must believe total air flow is also reduced. I use the formula 1mm=8cfm so for a 2.4" pipe the flow is 488cfm.
Now my point here is the SC intake and intercooler system is subject to the same rules. From the MAF to the intake matching air flow is the key to increased HP. Any one point along the air flow tract that restricts the flow of air reduces the overall air flow to the engine. A fact is the M90 Supercharger is capable of moving around 550cfm MAX. 500cfm inlet and 500cfm outlet flow see chart.
Verifying air flow through each part of the intake system is key. On the intake side of the supercharger the Air filter, MAF, throttle body & inlet plenum are all components we need to match. We only need to match components that are capable of flowing 550cfm each. More is OK but less is not. Matching a Pro-M 75mm MAF with a BBK 75mm throttle body is one example of flow matching components. Using a Stock 70mm MAF with a 75mm TB is a mismatch. This will restrict the air flow to the smallest component which is the 70mm MAF with stock center post reduces air flow even more. The only time this mismatch does not affect performance is when there is a greater restriction in the system or your SC air flow is at or below the components air flow capabilities.
Now onto the Intercooler side. I will begin with some numbers. The opening in the outlet side of the SC has about a 3 sq inch area opening. More on MP and S-Model SC setups. The stock SC top has about 1.5" opening for air flow. The raised top offers 2" (see pic) of opening for air flow. Modifying the top to allow increased air flow is possible (see pic). Removing the area from the front side of the neck will allow for about .25" increase. Not ideal since the ID of the nect is only 2.30" So porting the neck can get you upto 2.4" with a 1/8" margin of safety. So the best you could expect from modifying the current MP top is 2.4" of area for air flow.
Using the stock IC tubes and expecting anything close to 2.4" is not going to happen. The average ID is anywhere from 2-2.25". Extrude hone IC tubes I have seen but for the $$ you are better off spending it on a custom setup. More on the custom IC later.
The next point I want to discuss is the intake pluenum (outlet plenum) which bolts to the intake and delivers air to the intake. The stock part is the least restrictive part in the IC system. The flange where the IC tubes bolts to is about 2.3" ID and the opening to the intake is equilvant to a 2.75" opening. Mild porting and you have a good flowing part. The last part I wanted on comment on is the intake itself. Intake gasket matching and porting of the outlet plenum area is a big key to better air flow. The intake has a center triangle which can be removed to increase plenum volume by 4sq inches and increase air volicity when pressurizing the intake under boost. Also porting the opening to unshroud the air flow to the #3 cylinder is another important point when increasing air flow.
Rich
First I wanted to talk about air flow. Air flow through a 2.5" pipe is pretty much constant. Just like our favorite topic of exhaust flow through a mandrel bent vs. compression bent pipe. Air flow is reduced through a compressed pipe.
If we believe static air flow is reduced when it is compressed by a smaller diameter then we must believe total air flow is also reduced. I use the formula 1mm=8cfm so for a 2.4" pipe the flow is 488cfm.
Now my point here is the SC intake and intercooler system is subject to the same rules. From the MAF to the intake matching air flow is the key to increased HP. Any one point along the air flow tract that restricts the flow of air reduces the overall air flow to the engine. A fact is the M90 Supercharger is capable of moving around 550cfm MAX. 500cfm inlet and 500cfm outlet flow see chart.
Verifying air flow through each part of the intake system is key. On the intake side of the supercharger the Air filter, MAF, throttle body & inlet plenum are all components we need to match. We only need to match components that are capable of flowing 550cfm each. More is OK but less is not. Matching a Pro-M 75mm MAF with a BBK 75mm throttle body is one example of flow matching components. Using a Stock 70mm MAF with a 75mm TB is a mismatch. This will restrict the air flow to the smallest component which is the 70mm MAF with stock center post reduces air flow even more. The only time this mismatch does not affect performance is when there is a greater restriction in the system or your SC air flow is at or below the components air flow capabilities.
Now onto the Intercooler side. I will begin with some numbers. The opening in the outlet side of the SC has about a 3 sq inch area opening. More on MP and S-Model SC setups. The stock SC top has about 1.5" opening for air flow. The raised top offers 2" (see pic) of opening for air flow. Modifying the top to allow increased air flow is possible (see pic). Removing the area from the front side of the neck will allow for about .25" increase. Not ideal since the ID of the nect is only 2.30" So porting the neck can get you upto 2.4" with a 1/8" margin of safety. So the best you could expect from modifying the current MP top is 2.4" of area for air flow.
Using the stock IC tubes and expecting anything close to 2.4" is not going to happen. The average ID is anywhere from 2-2.25". Extrude hone IC tubes I have seen but for the $$ you are better off spending it on a custom setup. More on the custom IC later.
The next point I want to discuss is the intake pluenum (outlet plenum) which bolts to the intake and delivers air to the intake. The stock part is the least restrictive part in the IC system. The flange where the IC tubes bolts to is about 2.3" ID and the opening to the intake is equilvant to a 2.75" opening. Mild porting and you have a good flowing part. The last part I wanted on comment on is the intake itself. Intake gasket matching and porting of the outlet plenum area is a big key to better air flow. The intake has a center triangle which can be removed to increase plenum volume by 4sq inches and increase air volicity when pressurizing the intake under boost. Also porting the opening to unshroud the air flow to the #3 cylinder is another important point when increasing air flow.
Rich
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