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I have a D15 with a ported B7 head and an A6 camshaft with the stock 56mm TB.
Found an intake manifold and matching 74mm TB for a good price.
That seems like alot (too much). Thoughts?
You are right... it is WAY too much. There is a difference between volume and velocity... and ideally, you want the volume to be just enough to keep from losing velocity throughout the power-band. When you go turbo or supercharged... too big is no longer an issue because the power adder creates velocity.
In short, a throttle body that is too big will not make any more peak power than a properly sized throttle body... but it WILL lose power in the low to mid range area of the power band.
If I recall, you can get an F22 throttle body and it's 60mm instead of the 56mm. Port a D16Y8 IM to match and that will give you a little bit more but shouldn't be over the top.
The F22 TB also looks and has the FITV of the D series if I recall so looks exactly OEM like the B7 throttle body. You will need to tune for it though.
I think the fatter slightly shorter length Y8 runners will give you better low and mid range while the skinnier longer Z6 runners give you better top end velocity. I could be mistaken as I haven't actually tested this and am trying to recall the understanding I thought I had when I was researching all of this several years ago.
If I recall, you can get an F22 throttle body and it's 60mm instead of the 56mm. Port a D16Y8 IM to match and that will give you a little bit more but shouldn't be over the top. For a mildly modded D16, I think a 58-60mm T/B is a great place to start, and probably exactly the size needed.
The F22 TB also looks and has the FITV of the D series if I recall so looks exactly OEM like the B7 throttle body. You will need to tune for it though.
I think the fatter slightly shorter length Y8 runners will give you better low and mid range while the skinnier longer Z6 runners give you better top end velocity. I could be mistaken as I haven't actually tested this and am trying to recall the understanding I thought I had when I was researching all of this several years ago. TomCat, that is actually backwards. The long, narrow intake runners are better for low and mid-range performance... the short, fat intake runners are designed for top end power. No intake manifold design will give you more power everywhere on an N/A engine... you will give to get.
How much is too much NA air?
