Bigger throttle body and ported manifold/ intake restrictions?

1FSTBRD

Registered User
I was just wondering what everyone' experiences were with putting a bigger (any size) throttle body and then porting the throttle body opening in the manifold. I'd gone the 70MM Accufab/ porting route on my '99 split port 3.8 Mustang and found that I'd lost some throttle response, but the difference was when I'd ported it, as when I put the stock TB back on with the same porting, the car went back to its normal throttle. Does it make much difference on the 3.8 supercharged version? I'd just bought my '91 SC, so it's stock right now, but obviously soon won't be, heh heh.

A few more questions:

1) What are the constrictions on the normal SC engine? Obviously the heads to a certain extent, and the exhaust (especially on these cars)
2) On the stock M90, does the opening/ port below the supercharger suffer from heavy casting flaws/ restrictions?
3) Also, does the supercharger, itself, pick up any heat from the upper manifold and would isolating it with a phenolic spacer be of any use? The upper manifold on my Mustang stays way cooler with the G10 phenolic spacer in between the upper and lower manifolds, plus, it was great to clean out the carbon and gunk in there while I was at it
 
Your 99' wasn't boosted i am guessing. Too big of throttle body/intake will hurt low end on NA cars especially smaller displacement. On the Sc being boosted, it will help across the rpm range. These thing are breathing through a straw! A good start is a 75mm TB and 76mm MAF with a 3" inlet pipe. I ported inlet opening and as far as I could reach to match and blend. But from my research on here, the inlet still necks down to 68mm... You will notice it will rev a little quicker. Too big of exhaust can lose torque too. I put true dual 2.5 on mine and noticed a little loss in low end. But nothing 5% od couldn't fix. :D
I was just wondering what everyone' experiences were with putting a bigger (any size) throttle body and then porting the throttle body opening in the manifold. I'd gone the 70MM Accufab/ porting route on my '99 split port 3.8 Mustang and found that I'd lost some throttle response, but the difference was when I'd ported it, as when I put the stock TB back on with the same porting, the car went back to its normal throttle. Does it make much difference on the 3.8 supercharged version? I'd just bought my '91 SC, so it's stock right now, but obviously soon won't be, heh heh.

A few more questions:

1) What are the constrictions on the normal SC engine? Obviously the heads to a certain extent, and the exhaust (especially on these cars)
2) On the stock M90, does the opening/ port below the supercharger suffer from heavy casting flaws/ restrictions?
3) Also, does the supercharger, itself, pick up any heat from the upper manifold and would isolating it with a phenolic spacer be of any use? The upper manifold on my Mustang stays way cooler with the G10 phenolic spacer in between the upper and lower manifolds, plus, it was great to clean out the carbon and gunk in there while I was at it
 
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You are right, the 'Stang is N/A.

That makes sense for a bigger TB on the SC engines, though.

Do you or anyone else have any ideas on how to reduce underhood intake temps? I'm paranoid of blowing head gaskets and adding any heat to the engine that doesn't need to be there. I'm running 94 octane in the car right now since I'd got it a few days ago, to try to minimize detonation and excess heat in the cylinders.
 
2) On the stock M90, does the opening/ port below the supercharger suffer from heavy casting flaws/ restrictions?

The inlet is on the rear and the outlet is on the top.

The later model superchargers have a different inlet design - I think most people don't bother trying to work on porting the early model superchargers...they find a later model and either run it stock or port it and the plenum. There are tons of existing threads here on that process or you can purchase uprated components from http://www.magnumpowers.com, as one example.
 
You are right, the 'Stang is N/A.

That makes sense for a bigger TB on the SC engines, though.

Do you or anyone else have any ideas on how to reduce underhood intake temps? I'm paranoid of blowing head gaskets and adding any heat to the engine that doesn't need to be there. I'm running 94 octane in the car right now since I'd got it a few days ago, to try to minimize detonation and excess heat in the cylinders.

The first best thing you can do in this regard is upgrade your intercooler - either with a double IC (Ken Wagner makes the best ones), or a pricier front mount IC, which will require other modifications to go with it. IC fan is good too, along with a baffle to channel the airflow across the IC.
 
The inlet is on the rear and the outlet is on the top.

The later model superchargers have a different inlet design - I think most people don't bother trying to work on porting the early model superchargers...they find a later model and either run it stock or port it and the plenum. There are tons of existing threads here on that process or you can purchase uprated components from http://www.magnumpowers.com, as one example.

Ah, gotcha! Excuse my noob-ness with the SC's, ha ha. I was looking for a Magnum Powers plenum, but I couldn't seem to find one. They may still sell it, but perhaps I am blind on the internets. :D
 
Send Charles an email and ask what he has on hand. Last time I was by there I saw at least one :) Also keep an eye on the classifieds here - I think one just sold last week.
 
Mp plenum

Supercoupeperformance has them I think I checked mp website and didn't see it listed.i just bought a used one bought a month ago I can stick my whole arm in it great design.cant wait to put it on.i dnt understand why there so expensive brand new last I saw $560 wonder if u could get away with a mandrel bent exhaust pipe and weld a flange for tb and vacum line and smush it at the blower inlet and flange it.but sometimes hassle is harder. than spending the $ on a part that fits
 
Supercoupeperformance has them I think I checked mp website and didn't see it listed.i just bought a used one bought a month ago I can stick my whole arm in it great design.cant wait to put it on.i dnt understand why there so expensive brand new last I saw $560 wonder if u could get away with a mandrel bent exhaust pipe and weld a flange for tb and vacum line and smush it at the blower inlet and flange it.but sometimes hassle is harder. than spending the $ on a part that fits

It's a really limited production piece, and Charles at MP had to foot the bill for all the casting and machining. They have always been expensive - I think it was $450 back in 2007 or so.

It is possible to cut and weld a stock piece, merging it with an aluminum elbow, and get an improvement over stock. But it's not easy to do.
 
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