MyE28.com

Anyone have numbers on the stock flow rates of these 3 intake manifolds on a m30 motor? How about rates after they've been modded?

Modded how? The M30B35 intake I did some math on for my e30 build, and IIRC it has 47mm runners against 40mm intake valves which is the right ballpark in terms of the velocity you want. The throttlebody is actually a larger restriction in terms of cross sectional area

Lurker27 wrote:Modded how?

Port matched, extrude honed, or any other old school black magic tricks out there I'm unaware of.

None of the above!

Don't have numbers off the top of my head but I've been told the E12 intake manifold flows best, then B35 followed by B34. All of these intakes are inherently restrictive and act as 'corks' with sharp bends and uneven runner lengths. As I was determining which engine modifications made sense for my power goals we determined it made more sense to adapt a B36 throttle assembly to a B35 head. Since I'm using a turbo with a TCD w>a intercooler I'll be fabricating an accumulator as well. The OE accumulator inlet is in a less than ideal orientation in relation to the intercooler outlet. Only rough sketches at this point. Waiting to get the motor back in the car to see how much room I have to play with.

What's bothering me now is my turbo exhaust housing will likely prove to be too small to take full advantage of the increased flow efficiencies. It's always something...

No flow numbers from me; but on the "Sexiness Scale" its hard to beat the L-jet manifold from the E-12.

Mark 88/M5 Houston wrote:No flow numbers from me; but on the "Sexiness Scale" its hard to beat the L-jet manifold from the E-12.

Quoted for truthyness.

I will be adapting E12 runners for a B35/M90 mutt motor, sanding/grinding/filling till its smooth and no extra bits, port matching to the B35 head, and using a b34/35 TB, or maybe an M60 since the log/TB interface has to be hogged out anyway.

Bumping this thread out of interest. Does the E12 manifold really flow comparably to the B35’s? I’ve seen this suggested in a few places now. I’m planning a dirty B34 setup as I recently came into some piano top pistons, so if the E12 manifold is a good choice I may pick one up as opposed to fitting a B35 manifold.

I have seen posts about the issues with injector fitment, what throttle body is ideal for this setup?

I don’t think there is any scientific evidence that points to them
Flowing better.

SlickDizzy wrote:Bumping this thread out of interest. Does the E12 manifold really flow comparably to the B35’s? I’ve seen this suggested in a few places now. I’m planning a dirty B34 setup as I recently came into some piano top pistons, so if the E12 manifold is a good choice I may pick one up as opposed to fitting a B35 manifold.

I have seen posts about the issues with injector fitment, what throttle body is ideal for this setup?

My suspicion is that for an NA car, the Ljet manifold may be better due to the size of the plenum for equal flow to each cylinder. The smaller runners work better to improve air velocity for low end torque where I think the larger E21 runners may improve high rpm power.

I suspect (but have no back up evidence) that for turbo the B34/B35 manifold has a smoother flow path due to the direction of the cast aluminum manifold runners. It certainly has fewer gasket/leak points since it is one piece. As I understand, the B35 manifold much improved in terms of flow path over the B34 manifold.

Also interested what others know...


From my experience with Ljet, you would need head to log manifold adapters that also house the injectors. So getting the whole intake manifold would be the best bet to get started. Notice the different setup of the fuel rail also, which is sitting there next to the coolant reservoir.

I looked into some of this a while back and IIRC you could swap pintle caps and O rings and run later E28 era injectors in an earlier manifold. Also a friend who built an interesting 3.6 NA engine said the E21 manifolds were a torque boost, but HP restrictor due to their longer length. I believe he said it was both seat of the pants and dyno. I wasn't there so take this as an "I heard" from a reliable source, but not a claim of fact from me.