JFreeman

So Im in the middle of a build, and I am going to relocate the turbocharger. I was wondering if anyone has compared flow rates and characteristics between the turbo intake manifold and the NA intake manifold.

V2Rocket

gotta ask, where's the turbo going to sit? there's tons of room on the passenger side front if you ditch the pop-up headlights..

m73m95

NA also has a bigger throttle body...

blown 944

Mark, I'm not sure that is true. I'll measure them tonight. I'm currently working on my manifold and mounting "a" throttle bodyon the 83. I'm not which one yet but I could swear between the turbo and Na that the turbo throttle plate was larger diameter. I'll report back this afternoon.

JFreeman

Reading the responses I did chuckle a lot. Going to sit exactly where the pop up light used to be on the right side. Might go with a different charge air cooler also, haven't decided yet. I hear the stock turbo manifold doesn't flow the same to each cylinder so if the NA does, and flows more...that's a double win!

blown 944

just measured the throttle bodies and the turbo is about 1/16" larger diameter. I didn't mic the throttle blades but using a simple tape measure this is what I saw.

m73m95

Hmm... I can't imagine what I was seeing then. I didn't do any measuring, but when I held my spare 951 throttle body to my NA, I saw the NA as being bigger.... I do trust your measurement, but I'll have to go see what it was that I was seeing. Perhaps the plates are different sizes than the housing diameters?

Anyway, as common as the bosch system was in the 80's, I think its entirely possible to find a larger replacement that has the same, or very similar TPS and vacuum ports. Hopefully even closer than the BMW unit you're using.

JFreeman

So has anyone ever had an NA manifold on a flow bench before?

Rogue_Ant

I plan on putting both the NA and turbo manifolds on my flowbench when I get back...

JFreeman

Well I'm bringing this post back to life. Wondering if Joshua or anyone else has checked this out. Should begin turbo fitment and exhaust routing tomorrow. Depending on which manifold I go with greatly efects which intercooler will be used. So...anyone?

Rogue_Ant

Haven't gotten around to it yet...
I would imagine that the NA manifold is better, as there was less design restrictions compared to the 951 piece.

Thom

I had both a stock 951 and a 2.7 intake manifold on a flow bench.

The 951 intake was not too badly balanced with a 4% error between runners but the 2.7 intake returned a ~16% error because of runner #1 flowing significantly less than the other three. Apart from this runner all others flow about ~250 cfm, which is not really impressive.

Rogue_Ant

Thom - very interesting! So cylinder 1 flow was less... any thoughts on how that might affect the #1 cylinder since the port flow significantly less than the manifold runner?

Thom

I suppose the error will decrease as boost increases.
The factory presumably did not really care about the higher imbalance since a NA manifold is not supposed to see a MAP higher than 100 kPa anyway, and as you say a stock head will most certainly always flow less than its corresponding stock intake manifold.

333pg333

For all the fab work to put a turbo on the other side I can't imagine not going with a custom intake.