I am looking for helpful input on the design and different features that would be necessary for a marketable product. The height of oil filter housing is one of my main concerns right now. I would like it to be a direct bolt in, but the runner length and shape that I have in mind will not work unless the housing is shortened. Would this be a deal breaker if a shorter housing was available on exchange with minimal cost? Also, I do not think that the design will allow for a strut tower brace (which apparently has little to no benefit on our venerable E36 chassis...). It will have bungs for N2O or methanol injection (Mr. Butters) and it will have two different plenums with different throttle body locations/sizes and two or three different plenum volumes...discuss...discuss...
GDM ENGINEERING
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It will have bungs in each runner ? Like 1/8 npt ?
1996 332IS
Built 3.2
CES/Steed TS Precision 6466, spraying a "$π!℅" load of meth.
Technique Tuning 80# tune.
1/4 mile 10.84 @ 136.72
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Last edited by milKt; 08-19-2016 at 11:55 AM.
Can you post pics of interim designs? I would like an option for no bungs and I would want stock tb location, except maybe a shorter intake (ie tb closer to the head) for more room on the intake side
Last edited by TheJuggernaut; 08-19-2016 at 04:14 PM.
I second that.
Modular sounds great. Something with a flat surface that we could make our own cap for if we didnt want yours. For example if I want to put laminova water to air cores in it. Or I want to use a GM ICV. This also means the runners could be extended DIY and half the equation is the length from the valve to the internal reflective surface.
Shorter runners seems like the best way to keep the rest of the stuff simple.
Meth injection for sure on NPT thread but make the NPT thread small enough to be drilled out for staged injection or flow measurement.
ICV relocation and mounting.
Temp, MAP relocation. Maybe an integral vacuum manifold to buffer MAP bounce.
A place to hide the catch can, hoses, and FPR.
Most all of this can be done by the use if you have a flat surface for a modular plate.
Hey, that was my idea!
Seriously though I think this is the way to go. I wouldn't want the runner any more than about 2 inches shorter than stock or it will be a turd in the low/mid range. If the goal is a nice wide powerband I don't think there is a thing in the world wrong with the stock intake other than that the plenum is very small. The vast majority of people won't rev there stuff high enough to take advantage of a short runner. As much as people think they want the top end power, people will be very disappointed if they see a dyno chart spooling 500 rpms later.
Last edited by someguy2800; 08-19-2016 at 11:56 PM.
Im ready to see a rendering
+1
Also, the plenum does not count as runner length. The runner length does not go to the back of the plenum.
Cast the runners. Its the only real way to have this be cost effective. Making it out of billett only makes sense if you are making a very small number and are doing the machining yourself for yourself.
Funny you mentioned 2", as that's what I was thinking really 1.5-2" max reduction. I don't think there will be much of a TQ drop of the OE runner shape is kept, the bend is very nice for velocity, but that few inches could help gain some room for additional plenum size, and maybe help with the top end breathing a little.
But we all know most setups are <7800 RPM on this side of the pond so the plenum should be built for that.
So we doing this or nah?
Infiniti G35S Turbo BMW M3/4/5 Ninja ZX6R 636
Penn State University '08...better than your school since 1855
Sigma Lambda Beta International Fraternity Incorporated
UTI Class of '10, BMW "STEPchild"
Acurazine.com Mod Squad
1996 332IS
Built 3.2
CES/Steed TS Precision 6466, spraying a "$π!℅" load of meth.
Technique Tuning 80# tune.
1/4 mile 10.84 @ 136.72
Your 1 and only stop for all your BMW performance needs
WWW.CESMOTORSPORT.COM
Yes, I am on a mini vacation. I agree on most accounts. I did not want a 6 inch runner, but I really didnt want a 10+ inch runner either. Also, the oil filter location really does suck. I dropped off three different intakes to get parts of them digitized. It seems as though I will be making several compromises.
Would 8.5inch long runner and 2.3 inch wide is good on the manifold?
That is a completely ambiguous question. A certain runner length will be right to make maximum torque at a certain RPM range. In general the shorter the intake runner is, the higher the rpm that it will be optimal at. The longer the runner, the lower the rpm it will be optimal at.
When the intake valve opens and the motor begins to draw air in it creates a local area of low pressure at the intake valve. This causes the whole column of air in each runner to accelerate toward the intake valve. The longer the runner, the more time it takes to get this column of air moving at top velocity, and the more inertia in carries. At low rpms the intake valve is open for a long time (speaking in milliseconds not crankshaft degrees) so the longer runner works well because that long column of air is slow to get going but carries alot of inertia, so it keeps packing air past the intake valve even as the piston is coming up from bottom dead center. At high rpms the intake valve is open for a very short amount of time, so you need to get the air column moving as quickly as possible. A short runner has a smaller volume of air and the low pressure pulse takes less time to travel up to the plenum so it is more effective at filling the cylinder in a short amount of time.
You know what rpm the manifold we have is most efficient at simply by looking at the torque on a dyno graph, so you can decide for yourself whether you want to move it up or down.
There is also some science to this in timing the pressure reverberations that travel up and down the intake tract to arrive back at the open intake valve at a certain time, but I don't put much stock in that as these reverberations are traveling at the speed of sound and they go through 5-20 reflections before the valve even opens again, and only work at a very specific rpm.
This is all a balancing act. Having the runner length tuned to be the right length to make the mid range torque but not be a dog on the top end Having the right plenum volume to support each intake pulse while keeping throttle response reasonable. Having the right port cross sectional area to keep the port velocity in the right range for different RPMs. Having the runner area right to support the high rpm air flow while having good velocity in the mid range. Having enough head flow to support the airflow demands for different displacements and higher RPM's and different runner lengths. No one manifold will be perfect for all combo's or peoples expectations for a powerband. The trick here will be to find one that has good gains for most, in the rpm range that they want to improve upon. One of the biggest reasons I like these motors is they make really good mid range power, unlike the 2jz's I have experience with that are turds below 5K. A significant portion of why that is, is because of the stock intake manifold design, and because we have enough head flow to not need to rely on the cam timing to make power up top like a 2jz does.
Last edited by someguy2800; 08-23-2016 at 09:48 PM.
Thanks for the explanation, the reason that i am asking cause i have one with that spec and need opinion on it. I guess i will found out when i put the engine together and dyno tune it.
This is pretty good info. I appreciate the breakdown. Lower frequencies have a higher wavelength which helps me keep it straight. Pushing efficiency way down gets untidy quickly because of the change in wave length or in short the length of the runner that helps you out. If you were to take the knowns and want to experiment I would look at what you started with as 1x and add a length of 1x/2 if you had to mess with it if the idea to reverse a pulse or 1x/4 if the idea is to cancel a pulse. I used 1x/4 on an exhaust side Helmholtz resonator that was dramatic for that narrow band. On the exhaust side it is a very narrow band as your gut tells you.
Like you said you can work off the known efficiencies we have from a runner length and diameter perspective. It seems like making a manifold with an unfinished plenum would allow people to play with the runner length and reflective surface distance if they chose to. For example extend a runner with a bell-mouth and finish the plenum box to whatever dimension you want to play with.
The GP bikes setup the plenum like a drum and use materials with a natural frequency centered around where they want the power. I don't think its a massive improvement but these guys are outrageous in the efficiencies they go after. I read about a team that used a thin material like kick drum material and actually tuned it like a drum with a key that stretched the material.
So I like new designs, but basically... you want to design the DI Manifold again?
That was my intent 6 months ago, but as I thought more and more about it....I want to improve upon it.
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