Turbocharging in place of supercharging...Has anyone done it?

phils89sc

Registered User
I used to own several Tbird SC's and know how well they run.. Currently I don't own one, not yet, but have an 85 SVO and was thinking about replacing the factory 2.3L SVO engine with an SC 3.8L or 4.2L. I talked to the guy I use to do my head work (Performance Masters) and he tells me that if I want to get maximum airflow through the head, I need to use the split port heads. Also, instead of sticking with the supercharger, I would like to turbocharge it. I have my reasons for wanting to go this route.

For those that have gone the turbocharging route, what is your config like? Where do I get a turbo header? I already have a proper ECU (PiMP with MS2) and will have to get an SC harness for my SVO.

Thanks,

Phil
 
I used to own several Tbird SC's and know how well they run.. Currently I don't own one, not yet, but have an 85 SVO and was thinking about replacing the factory 2.3L SVO engine with an SC 3.8L or 4.2L. I talked to the guy I use to do my head work (Performance Masters) and he tells me that if I want to get maximum airflow through the head, I need to use the split port heads. Also, instead of sticking with the supercharger, I would like to turbocharge it. I have my reasons for wanting to go this route.

For those that have gone the turbocharging route, what is your config like? Where do I get a turbo header? I already have a proper ECU (PiMP with MS2) and will have to get an SC harness for my SVO.

Thanks,

Phil

If you want to turbocharge a SC than you need to be able to fabricate most everything to make it work. There is not a bolt on kit available. Single port heads will flow good enough with a good port job and big valves.

Ken
 
Ken,

Thus far, I have decided to go with the split-port heads and intake. What is the best route to go for exhaust manifolds or headers? I have been out of the 3.8L SC game for a while now, and I don't know what is available now vs. way back when. When I had my last one, I had ported out my stock manifolds and that worked out pretty well. I can also weld and fabricate up any custom exhaust tubing I need, I was just wondering what is available, if anything, in the after market.
 
Ken,

Thus far, I have decided to go with the split-port heads and intake. What is the best route to go for exhaust manifolds or headers? I have been out of the 3.8L SC game for a while now, and I don't know what is available now vs. way back when. When I had my last one, I had ported out my stock manifolds and that worked out pretty well. I can also weld and fabricate up any custom exhaust tubing I need, I was just wondering what is available, if anything, in the after market.

nothing after market. I fabricate everything myself. I currently use ported stock manifolds but my setup is outside the norm. I don't know much about split port heads. There are more and more turbo guys here. For front mount turbo or turbos it is all custom and some of the other guys might chime in

Ken
 
How about the 3.8L vs. 4.2L question? I know the SC bottom end is pretty strong as it is, and I probably won't go past 18-20psi of boost. What would have to be done to a 4.2L to make it work under boost? Are we talking basically all new internals? Any suggestions?
 
How about the 3.8L vs. 4.2L question? I know the SC bottom end is pretty strong as it is, and I probably won't go past 18-20psi of boost. What would have to be done to a 4.2L to make it work under boost? Are we talking basically all new internals? Any suggestions?

Depends on HP goal. 300, 400. 500+, 300 HP stock bottom end no problem, up to 400 border line. Over 400 forged pistons & good rods. 4.2 will make HP easier and likely have an advantage TQ wise. 3.8 will make awesome HP done right. I have ran 26PSi a couple of times but prefer to stay around 20 to 21 as a max. But my engine is stout and built by the best

Ken
 
OEM 4.2 will work just fine from what I understand.

Sound to me like you would best be served with a 01+ Mustang or E/F-150. I personally think SCs should stay supercharged and an 01+ setup will handle a turbo at those levels.

A 01+block and 4.2 crank is just as strong a SC, by all evidence.

If it were me and had the budget Forged H-beam rods, and Forged Aluminum Pistons, plus what ever vavletrain your going with.
 
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We just finished it this weekend, its a 94 5 speed with ported heads and custom turbo cam, and a Precision 6266 T4 turbo.

Here's a part throttle video for the sound effects, we have to take some time and work on the tune, and work out a few bugs and then we'll have some more exciting footage.

https://www.youtube.com/watch?v=QNXb_c9nokE

Jeramie
 
Well, i'm in the middle--I have an SC with a single port, and a N/A 3.8 Mustang split port. My take on it is that for an N/A car, split port is better (ie: the base T-Bird MN-12's would have benefitted from the split port). If you had a 94-98 Mustang with a single port, the split port would be an upgrade--the 94 to 98 Mustangs made 145 hp with 215 tq, whereas the split port made 190 hp with 220 tq. It used to be more common on the Mustang forums, where guys would ask if they should swap their split port to single, which would allow them to run the SC supercharger (though with a ton of hassles and fabrication....and no real point to it).

The single ports have pretty big, unobstructed ports with a pretty good port floor. My analysis of the split ports is that the two ports/ runners have the capability to flow lots of air, but the low end torque runner/ port has a bend in it that compromises its abilities to flow.....which likely helps low end torque, but starts to hinder it at some point. The high end runner also gets pinched, anyways, at the intake bowl--though porting/ knife edging the split port divider into the bowl helps a fair bit. On the upside, If someone had the ability to analyze airflow through the ports at various valve lifts and various velocities, the split ports could probably be much better.....i'm talking about if someone knew the airflow rates where the low end torque runner stops drawing air through it, and where the top end runner starts drawing air through. I'd studied a few other split/ bi-port engine designs and runner tuning, but that's also more for an N/A car. The stock Ford exhaust valve and port is small, but it's also tuliped at pretty much a 45 degree angle.

Edit: I just did an informal weighing of the exhaust valves.....the split port are way lighter. You can feel it, it's noticeable....the concave design of the face, and the stem is much smaller. The intake valves are about the same weight, but the angle of the split port is much more conducive to the flow on the angle of the intake valve, whereas the single port SC has a pretty flat design. The margin on the exhaust valve can be ground down to blend into the tulip of the valve, too. But you're still stuck with a very small exhaust port.
 
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I do know that split port Mustang guys have made 275-300 rwhp/ 300 rwtq on 7-9 psi on a Vortech/ ProCharged setup in either a stock configuration and/ or mild bolt ons, with the stock engine compression of 9.27:1. Just sayin'. :D Again, the stock exhaust valve has an excellent tuliped design that is conducive to some pretty good flow. I'd ported/ polished some heads last year that I used as an initial design, but am currently working on a different one with slightly different ideas. I'm no expert, but I've had some hands on experience.

Also, the split port combustion chambers are significantly smaller, which leads to a higher compression in the split ports--no problem, since the quench area side has a lot of material that you could remove it from. Despite the smaller combustion chamber, the split port combustion chamber is also significantly less shrouded around the valves.....the intake valve, in particular, has a nice unshrouding from the factory on the non spark plug quench side.
 
I used to own several Tbird SC's and know how well they run.. Currently I don't own one, not yet, but have an 85 SVO and was thinking about replacing the factory 2.3L SVO engine with an SC 3.8L or 4.2L. I talked to the guy I use to do my head work (Performance Masters) and he tells me that if I want to get maximum airflow through the head, I need to use the split port heads. Also, instead of sticking with the supercharger, I would like to turbocharge it. I have my reasons for wanting to go this route.

For those that have gone the turbocharging route, what is your config like? Where do I get a turbo header? I already have a proper ECU (PiMP with MS2) and will have to get an SC harness for my SVO.

Thanks,

Phil


Phil,

Since it's going in an 85 SVO it would probably be a lot easier to use a stockish 5.0 based motor and turbocharge with a blow through carb instead of building up a 3.8 or 4.2 motor and doing fuel injected. Could probably find a used fox body turbo kit too.

David
 
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Another reason why the split ports flow pretty well, is because of the intake valve unshrouding as I'd mentioned--they should flow better when the piston is closer to the valves, because it is a far less torturous path for it to manage towards the cylinder walls. Believe it or not, the intake valve is actually bigger than the SC's......I seem to remember official Ford specs stating that it is smaller than the SC, but I can take a picture of the two valves with their faces up against each other, in case anybody doesn't believe it. That steeper angle of tuliping on the split port intake valve is way better for flow, because the SC's is much flatter in its relief, and I'd think that low valve lift flow would suffer in the SC heads. It's one speculation as to why the SC motors make so much torque, but comparatively less HP. The split ports make 20 less hp without a supercharger.
 
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I'd taken some pictures about 20 minutes ago. They're not of the greatest quality, but they show the differences in the valves.

Intake: the SC is on the left; the split port is on the right. The split port is bigger. The split port is polished, so it is a little more worked than the SC in this case, but the angle of the backside of the valve is just slightly more angled, and note the size of the stems. Those watching their valvetrain weight take note!
:D

scandsplitportintakevalvecomparison.JPG

Here's the exhaust valves--again, the SC is on the left, the split port is on the right. They're the same size (looks like the split port is bigger, but they're not aligned properly.....had to hold 'em with one hand and then take the picture with the other). The angle of the backside on the split port pretty much mirrors the valve seat face, if you remove some of the valve seat face margin (which I did......in stock condition, the margin would impede low lift valve flow more by hindering the flow along the backside of the valve). The stem sizes aren't as evident because of the picture, but they're the same sizes as the intakes in both cases. The weight difference, as i've said, is noticeable......the exhaust valve is way lighter on the split port. Again, that's up to oneself as to how much value valvetrain weight savings amount to, but it all adds up in a build. In this case, as well, the split port received a polished finish, but the SC valve is as modified as you could get it, because the valve seat margin can't be ground down for the most part, based on the contact patch with the seats. I still have to lap the valve properly, too, as the initial lapping was just to see where the valve seat contacts....there's a lot of pitting.

scandsplitportexhaustvalvecomparison.JPG

Edit: also, in terms of flow, the single ports look like they have the advantage, but velocity is likely down from the split port. One thing that I noticed with the split ports is that if you gasket match them (which I did), the high end/ high rpm runner in the split port forms a perfect horn-like shape (wider at the port entry, tapering down towards the bowl) to help pull air into the cylinder. The single port has a nice square shape, but the high rpm runner in the split port is a perfect round circle, which is probably going to equalize the airflow along the wall sides, port roof, and port floor. The SC's don't flow that well on the sides of the port (based on some flow testing that I did). Also consider this: the turbulent runner is the low rpm runner in the split ports, which means that the port roof in the SC which gets corrupted by the injector area is not in the air path. You're getting as close to a perfect tube into the intake bowl/ cylinder as possible. It also means that you can mirror finish the bejeezus out of the high rpm runner, since there is no fuel going through it until the bowl area and don't have to worry about atomization problems until the bowl.
 
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The exhaust to intake ratio is not ideal on split port heads for boosting. Plus the most powerful 3.8 factory head boosted motors out there are single port. This isn't an old debate here. You can do what you like but youll never convince me the splitport design is superior for this application
 
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