RotaMan99

I was thinking, when the SFM removal is available for the S4 N/A, getting the TB bored out and using 48mm plates and modifying the shaft for the plates to fit and also get the intake extrude honed to 48mm as well.

Now my question is, to take full effect of the 48MM intake and TB, I would need to make the housing's intake ports larger as well right, or is porting the intake port, mainly to change the opening and closing timing and not to allow more CFM.

Basically, I know I may gain some by going to 47-48mm from 45mm but would it be worth it on stock ports?

I was thinking about the price of doing this as well. The TB porting wouldn't be a whole lot, but the extrude honing would I have been told. Compairing this to a ITB setup that I would need a Standalone on which costs even more $$$.

Just looking for some input. I don't want responces like, don't do it or its not worth it. I want some explaination as to why so I can understand a little further.

Thanks.

WadeMCarter

Increasing the size of the port means more air enters the combustion chamber, but when you increase the size, it also changes the duration of the rotor passing it. i guess you can consider it a bottleneck effect, but opening up things helps. I say port your motor, its fun to drive around with it.

Eva001Ikari

iTrader: (7)

Well if you think about it this way it might make a little more sense.

Say you wanted to get water from a 2 liter bottle into a bucket, but all you have is a little tiny funnel to do it with. Even if you make the bucket as big as humanly possible, the water isnt going to go any faster. Boring out the throttle body would help i suppose but it would still only get as much air as the intake manifold can handle and get through the ports into the rotor housing.

So you still have that little tiny funnel to do it with. So do something about the funnel, bore out the throttle body and port the housings, of course it will get you extra power but you know, the injectors and the intake manifold are going to have something to do with it.

TehMonkay

iTrader: (-1)

Porting the engine has much more of a benefit than porting the throttle body ever would. Should've spent the money on that first.

The amount of power that can be made on stock ports is pretty high, but it's easier to make the power if you port the engine, and porting the exhaust will spool a turbo faster.

RotaMan99

Ya I was thinking about the cross sectional area of the port and I knew it does matter but I was trying to think that maybe if I make the intake runner on the housing so it was shapped as a velocity stack, that maybe it would work out good with stock ports. Since the restriction of the intake manifold and TB would be out of the question at that point.

RotaMan99

I don't have a turbo.

I was also going to do this so that when I do port the motor, im not longer as restrictred by the TB or intake as I would be before.

TehMonkay

iTrader: (-1)

People rarely ever port the intake, the only intake mod done is usually just removing the secondary throttle plates.

If you do want to spend the extra cash on this, port the engine first. Intake and exhaust, replace the exhaust port diffusers with the turbo ones, and make sure you at least have a header. If you have an S4 switch over to the S5 manifolds.

RotaMan99

I already have S5 mani

RotaMan99

I was doing some math and found that the area of the bores that air can flow through is actually smaller then the runners them selves. Porting the TB and using 48 mm plates should help a little. Its still smaller then the intake runners. So it seems the TB, at WOT could be a large restriction in the intake system.

NZConvertible

How closely have you looked at the TB? There is very little scope in the TB casting for enlarging the bores. I've seen one Japanese company modify them for 47mm plates and it cut right into the o-ring groove on the inlet side. It looked like sealing it to the IC pipe or intake pipe would be a bitch. In a perfect world you could expect a maybe a 10% increase in flow on a flowbench, but on an engine with all it's other restrictions added you'd be lucky to see 2-3% gain in peak power, and less at lower revs. I can't see it being worth the cost for an NA.

RotaMan99

^ I completly agree for the most part. This would be on an n/a and the o-ring on my TB is so flat I doubt its doing much of anything. Infact, before I say it does nothing, im going to remove the o-ring. I think I did run without one once but I don't remember. I think the plastic Elbow will make a tight enough seal if a metal layered gasket for the LIM to engine seals good enough.

With other restrictions, I see the AFM and filter. Im going to be running 3.25" ID piping and remove the AFM once the new version of the Rtek comes out.

Im not looking for any gains down low.

Now if I did this I would have to port match the DC but thats not a problem. It looks like 48mm is as big as you can go without sacraficing to much integrity.

The plate shafts I also ground down to help increase the cross-sectional area. By doing the math I only gained about 6% total. 2% per bore. Which would give me about a 16% increase. Not a whole lot, but might be worth it. I could grind some more off the shaft to maybe hit 20%.

RotaMan99

I did the math wrong after measuring the ports on the intake manifold. So the secondaries are actually small in area then the TB bores, even with the shafts and the primary runners are larger in area then the TB bore especally adding the both of them together.

So boring out the TB would really not do much of anything unless the intake manifold runners were larger.

RotaMan99

^ I said that wrong. The TB bores are still larger then the primary and secondary runners. The primarys combined is a little larger then the priamry TB bore. So you probubly wont gain anything.