E21 'log' intake vs. E30 318i intake

[winstontj]

I was just cautioned that the E21 intake can limit or restrict power and performance and that the E30 intake would be a better choice for an EFI conversion. Can anyone substanciate this?

I now have two E21 manifolds and one E30 manifold. I'd rather use the E21 because of the way it looks. Regardless of looks this is going on a stroker motor and I want all the power I can get. I want the manifold that will allow for the most power.

Any help or feedback would be much appreciated.

TIA,

TJW

[bimmerboy]

they paid much more attention to actually tuning the manifold. altho it may get a bit small for a stroker. but i dont see the 320 being any better even if its from a 2.0

[winstontj]

they paid much more attention to actually tuning the manifold. altho it may get a bit small for a stroker. but i dont see the 320 being any better even if its from a 2.0

so is there a difference or not? Should I look for something different than the e30? I'm aiming to get ~180hp out of the stroker motor. (~150 at the wheels) The only real difference that I can see is that the E21's fuel injector bungs are more intrusive to the intake port, meaning the bumps stick down further or are larger in the e21 than in the e30 where the FI bumps are almost non-existant. Other than that they are the same size opening. I'm also assuming that I can have the head and intake ported to match a little bigger and better.

Should I really be worried about this for a lower HP car?

[MichaelP]

If it helps, the M30 (big six) motor went through the same manifold design metamorphosis from log type with 'horns' to the later one-piece unit, and the flow across the entire torque curve in the later type is much better. Quantitatively, the early log version resulted in serious mid-range torque loss, and the common fix (though only semi-effective) is to use the larger radius m10/e21 horns, though WOT suffers somewhat as a result.

Every early efi'd big six owner would likely have swapped to the single piece manifold by now if the injectors would swap between L-jet and Motronic -- but they don't without injector port machining.

[winstontj]

the early log version resulted in serious mid-range torque loss, and the common fix (though only semi-effective) is to use the larger radius m10/e21 horns, though WOT suffers somewhat as a result.

So it's more of the radius and turn of the horn than the bore and air flow capacity?

Am I making a mistake by going with the more period correct looking intake?

[edgefinder]

I didn't know all of this but i'd say use what works best. Form follows function.

[winstontj]

I didn't know all of this but i'd say use what works best. Form follows function.

edgefinder - my goal in asking the question and starting the thread was to find out whatever works best. Right now I feel like I don't have enough information to make an educated decision on which one to use. I am planning on using the E21 however depending on how much (if any) power loss there will be with the E21 intake I may want to sacrifice the form and go with the function of the E30.

[bimmerboy]

e30s work better, i have no idea on how much better tho. it may not be worth, because the 320 mani does look much better on the '02s

[peteinjp]

Might not be worth it but you could get the 320 unit extrude honed for better flow?

[DAK]

If you read the first sentence of bimmerboy's original post and MichaelP's answer... you have your answer. The e30 manifold was specifically designed by BMW to boost low to midrange torque with as little loss of top end as possible. Try to think of it the same as exhaust; a log manifold will work but a tuned header will flow better. How much better? How much of a difference? As with most mods one high performance mod will play off of and reinforce another.

It's all pretty complicated stuff (fluid dynamics, cam specs, valvetrain frequency, blah, blah, blah...). For a performance N/A motor go with ITB's for a force fed go with the e30. If you are truly concerned with premium performance build your own manifold tuned to suit your particular needs/concerns.

If you truly are going to turbocharge your stroker then the flow characteristics of the intake manifold become less of an impact on power band or peak. So you probably won't notice a difference unless you are going for maximum streetability.

Use what you like and you will be happy. All you've got to do is decide what is more important to you.

[winstontj]

If you read the first sentence of bimmerboy's original post and MichaelP's answer... you have your answer. The e30 manifold was specifically designed by BMW to boost low to midrange torque with as little loss of top end as possible. Try to think of it the same as exhaust; a log manifold will work but a tuned header will flow better. How much better? How much of a difference? As with most mods one high performance mod will play off of and reinforce another.

It's all pretty complicated stuff (fluid dynamics, cam specs, valvetrain frequency, blah, blah, blah...). For a performance N/A motor go with ITB's for a force fed go with the e30. If you are truly concerned with premium performance build your own manifold tuned to suit your particular needs/concerns.

If you truly are going to turbocharge your stroker then the flow characteristics of the intake manifold become less of an impact on power band or peak. So you probably won't notice a difference unless you are going for maximum streetability.

Use what you like and you will be happy. All you've got to do is decide what is more important to you.

My gut says I won't be able to tell the difference in the seat of my pants. That means the e21 wins because it's period correct. On the other hand - if it could make a 10-15hp (flywheel) difference - which could be possible in a 180hp motor, I'll want to get that extra 10-15 because it's 5-8% and possibly 5% at the wheels. That's my debate. Headers are what they are.... but I never thought about the fact that BMW designed the e30 for better power as well - I always thought it was easier for procuction and must have been cheaper.

Honestly as long as I can get 150 to the wheels I'll be happy.