Just did this last week and was very impressed with the results. Engine revs up much faster and pulls harder.
Anybody else do the E21 Intake Runner conversion?
- Thread starter sfdon
- Start date
Different intake runners?
I once mocked up an L-jet manifold with the E21 runners but never ran it on an E9. Instead, it was tried on a friend's early 530i (E12).
My memory is vague, but the results were not as readily apparent or as impressive as yours. I recall that the throttle response was reduced while the engine felt stronger only at the higher end. These results could have been misleading or anomalous since the engine was a tired lower compression model coupled to an automatic.
I seem to recall that the E21 runners are a bit longer but do not remember if they were also slightly larger. My friend, who is/was better versed in fluid dynamics, reasoned that the size difference resulted in slightly reduced air speed but greater volume or something on that order. While driving the car, I wondered out loud how an E21 might run with E9 runners, but never pursued this idea. (I suspect they might not fit or there are other interference issues.)
If these runners provide as dramatic an improvement as you have experienced, I wondered why BMW did not use them, at least on their European models (where emissions may not have been much of a consideration). One would think it would have been more economically prudent to produce one size versus two or more. Which runners were used on the racing models?
Given the slightly larger runners, have you experienced any clearance issues? Does everything (e.g. the stock filter) fit as well as before? Any obvious negatives?
Depending on your answers, I may give it another go!
Thanks.
I once mocked up an L-jet manifold with the E21 runners but never ran it on an E9. Instead, it was tried on a friend's early 530i (E12).
My memory is vague, but the results were not as readily apparent or as impressive as yours. I recall that the throttle response was reduced while the engine felt stronger only at the higher end. These results could have been misleading or anomalous since the engine was a tired lower compression model coupled to an automatic.
I seem to recall that the E21 runners are a bit longer but do not remember if they were also slightly larger. My friend, who is/was better versed in fluid dynamics, reasoned that the size difference resulted in slightly reduced air speed but greater volume or something on that order. While driving the car, I wondered out loud how an E21 might run with E9 runners, but never pursued this idea. (I suspect they might not fit or there are other interference issues.)
If these runners provide as dramatic an improvement as you have experienced, I wondered why BMW did not use them, at least on their European models (where emissions may not have been much of a consideration). One would think it would have been more economically prudent to produce one size versus two or more. Which runners were used on the racing models?
Given the slightly larger runners, have you experienced any clearance issues? Does everything (e.g. the stock filter) fit as well as before? Any obvious negatives?
Depending on your answers, I may give it another go!
Thanks.
x_atlas0
Well-Known Member
Larger and longer runners mean you get better response at lower revs. That's why all the high-revving engines (S38, M88, Ferrari, Lambo, Jag) have very short runners, usually called velocity stacks. The length and cross-sectional area of the stack determine when the optimal operating point is.
bengal taiga
Well-Known Member
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Manifold runner lengths
I will certainly defer to your superior knowledge on this subject, but I think you oversimplified things. I agree longer runners typically yield more low end torque (see for example Chrysler's famous 440 wedge's http://www.carlustblog.com/images/2008/08/26/4wrd_lk_engine.jpg (Although looking at Mercedes W194 300SLs seems to superficially contradict that notion. http://image.motortrend.com/f/85230...ng_1954_mercedes_benz_300_sl_coupe_engine.jpg
Yet, I understood that if the diameter of the runner was too large for a particular application, it could lead to reduced air pressure, reduced velocity, reduced throttle response, and consequently - power loss. The point being that bigger may not always be better. I do not know if, in fact, the E21 runners are actually larger in diameter or the same size as the csi runners so it may be that the only difference is length.
To me, manifold design appears to be a black art based on science. I do not profess to know anything other than what I have read about the supposed benefits of using the E21 runners, but I am curious to know both the real world benefits AND detriments, if any. Those who have tried it on our M30's please expound.
Thanks.
x_atlas0 said:
I will certainly defer to your superior knowledge on this subject, but I think you oversimplified things. I agree longer runners typically yield more low end torque (see for example Chrysler's famous 440 wedge's http://www.carlustblog.com/images/2008/08/26/4wrd_lk_engine.jpg (Although looking at Mercedes W194 300SLs seems to superficially contradict that notion. http://image.motortrend.com/f/85230...ng_1954_mercedes_benz_300_sl_coupe_engine.jpg
Yet, I understood that if the diameter of the runner was too large for a particular application, it could lead to reduced air pressure, reduced velocity, reduced throttle response, and consequently - power loss. The point being that bigger may not always be better. I do not know if, in fact, the E21 runners are actually larger in diameter or the same size as the csi runners so it may be that the only difference is length.
To me, manifold design appears to be a black art based on science. I do not profess to know anything other than what I have read about the supposed benefits of using the E21 runners, but I am curious to know both the real world benefits AND detriments, if any. Those who have tried it on our M30's please expound.
Thanks.
From my measurements the diameter was the same- difference seemed to be the length of the tube. My thought was the airmass did not have to make such a sharp turn from one port to the other [upper to lower] possibly allowing less turbulence in the tube. No clearance issues- just one change to the bend in the fuel regulator bracket. First fives has a nice write up with pics and reference to higher dyno numbers. Biggest problem I see is I have to put the money out for a limited slip diff now .
MichaelP
Well-Known Member
Re: Manifold runner lengths
Much of the empirical evidence I've seen to support x_atlas's position is found over at firstfives.org. Numerous E12 owners have done this and report various degrees of improved low end torque traded off for a flatter curve at redline. If you do some site searching over there, you'l find some discussion of how to improve breathing at the top end with a Megasquirt injection arrangement. Look for Peter Florence's posts on the subject in particular.
bengal taiga said:
Much of the empirical evidence I've seen to support x_atlas's position is found over at firstfives.org. Numerous E12 owners have done this and report various degrees of improved low end torque traded off for a flatter curve at redline. If you do some site searching over there, you'l find some discussion of how to improve breathing at the top end with a Megasquirt injection arrangement. Look for Peter Florence's posts on the subject in particular.
Re: Manifold runner lengths
I heard about the swap from someone at karznparts, well before seeing the first five article and thought enough of the theory to fab up a transplant manifold. As noted the results were mixed. Now, I seem to remember some pretty bad weather at the time too.
Maybe you can address my earlier musings.
First, I have never heard anyone knowledgeable expound on why BMW never used the longer runners on the M30 if there is was real downside and only an upside.
Second, I see references to the Grassroots dyno results but do not see them posted, if you know, can you please share?
Third, how about the competitive aspects of the manifold modification? I have never seen any mention of it as a common upgrade other than first fives, maybe metric mechanic and now on E9.
As an aside, here are some interesting pics: http://aaron.aussiefiverdriver.com/M30 engine.htm
Thanks to all for rekindling my curiosity.
MichaelP said:
I heard about the swap from someone at karznparts, well before seeing the first five article and thought enough of the theory to fab up a transplant manifold. As noted the results were mixed. Now, I seem to remember some pretty bad weather at the time too.
Maybe you can address my earlier musings.
First, I have never heard anyone knowledgeable expound on why BMW never used the longer runners on the M30 if there is was real downside and only an upside.
Second, I see references to the Grassroots dyno results but do not see them posted, if you know, can you please share?
Third, how about the competitive aspects of the manifold modification? I have never seen any mention of it as a common upgrade other than first fives, maybe metric mechanic and now on E9.
As an aside, here are some interesting pics: http://aaron.aussiefiverdriver.com/M30 engine.htm
Thanks to all for rekindling my curiosity.
Interesting link- BUT- a lot of errors in regards to the 745i info...
Wrong dates, wrong designations for the M106..
[BTW- I own a m102 Jet and a m106 motronic]
If I were to have one complaint with the m30 b32 engine in my coupe it would be the flat [read boring] response to throttle at lower rpms. Possibly that would be taken care of by the Euro spec 9.3 cr vs the US 8.4 cr of the m30 b32 or by the original e30 b30m with its 275 Nm of torque.
Or maybe I'm used to the 400+Nm of torque of the 745i.....
As a downside- the wife who is the driver says that there is less tractability at very low rpms and in fact complains about it.
As always- bay area residents are welcome to test drive it and give their opinions.
:wink:
Don
Wrong dates, wrong designations for the M106..
[BTW- I own a m102 Jet and a m106 motronic]
If I were to have one complaint with the m30 b32 engine in my coupe it would be the flat [read boring] response to throttle at lower rpms. Possibly that would be taken care of by the Euro spec 9.3 cr vs the US 8.4 cr of the m30 b32 or by the original e30 b30m with its 275 Nm of torque.
Or maybe I'm used to the 400+Nm of torque of the 745i.....
As a downside- the wife who is the driver says that there is less tractability at very low rpms and in fact complains about it.
As always- bay area residents are welcome to test drive it and give their opinions.
:wink:
Don
bengal taiga
Well-Known Member
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Not accurate?
It has to be accurate, I read it on the internet! :wink:
sfdon said:
It has to be accurate, I read it on the internet! :wink:
Tierfreund
Well-Known Member
The intake runner swap imho belongs to the same cateogry of mods as K&N air filters, "cold air intakes" on E90s and fuel additives.
Faith moves mountains. The reason nobody ever posts real dyno numbers on such modifications, is that under controlled circumstances, you won´t find any improvements. While the famous butt dyno can easily be fooled by a difference in sound alone.
Take another long hard look at the engineering on your M30. Those bavarian engineers new what they were doing. And the gentlemen at the M-division were quick to raid the parts bin. So if they didn´t, there´s a reason.
Faith moves mountains. The reason nobody ever posts real dyno numbers on such modifications, is that under controlled circumstances, you won´t find any improvements. While the famous butt dyno can easily be fooled by a difference in sound alone.
Take another long hard look at the engineering on your M30. Those bavarian engineers new what they were doing. And the gentlemen at the M-division were quick to raid the parts bin. So if they didn´t, there´s a reason.
timt
Well-Known Member
For what it's worth:
The injected E9 plenum chamber is 3 litres, and each intake runner to valve is approximately 500 cc or one cylinder equivalence. For a purpose - flexibility and efficiency plus performance ... a set of compromises addressed in the second para of the extract below. Tierfreund's comment on the engineers sums it up nicely! There are books on induction tuning but also a brief and useful set of generic "guides" can be found on the Jenvey site wrt inlet tract length, throttle butterfly and injector positioning which help get all of this in context http://www.jenvey.co.uk/ go to Positioning within the Advice and FAQs tag.
Extract from AT Power write up on induction:
The air needs to be presented to the inlet valves as close to atmospheric pressure as possible, so why not have the inlet valves just open to atmosphere? Well, you need to have a throttle to control the air to control the engine speed and power. OK, so why not fit giant throttles and airways? Well, you don't just want a lot of air at the highest pressure available, you also want it travelling at high speed. This is because air actually weighs something, it has mass, which means it also has inertia. If lots of air was just sitting at the inlet valves at ambient pressure it would have to accelerate from standstill to high speed to get through the valves in the extremely short time that the valves are open. What you need lots of air to be travelling at high speed up to the valves just when they open, so it just charges in. This is where you have to find the right compromise where the inlet manifold airways are large enough to not cause too much restriction but small enough to keep the air flowing fast enough. Inlet manifold tuning can have a major effect too, but we won't go into that here.
The problem is made worse because the engine has to operate over a wide speed range. At high engine speed there's such a large amount of air going into the engine you can have large airways and still keep the airspeed at a reasonable speed. But at low engine speed the same large airway would cause the air to slow right down. This causes another significant problem. The fuel which has been squirted into the air stream won't mix properly to form a nice even explosive gaseous vapour. Instead it just drops down to the floor of the airway and you end up with a very weak gas mixture plus globules of fuel that won't burn properly, making the car undriveable at low speed. In a race car you sacrifice the low speed driveability, leaving a much narrower power band but with higher ultimate power. However you still need to keep acceptable response so you don't bog down as you accelerate out of corners.
The injected E9 plenum chamber is 3 litres, and each intake runner to valve is approximately 500 cc or one cylinder equivalence. For a purpose - flexibility and efficiency plus performance ... a set of compromises addressed in the second para of the extract below. Tierfreund's comment on the engineers sums it up nicely! There are books on induction tuning but also a brief and useful set of generic "guides" can be found on the Jenvey site wrt inlet tract length, throttle butterfly and injector positioning which help get all of this in context http://www.jenvey.co.uk/ go to Positioning within the Advice and FAQs tag.
Extract from AT Power write up on induction:
The air needs to be presented to the inlet valves as close to atmospheric pressure as possible, so why not have the inlet valves just open to atmosphere? Well, you need to have a throttle to control the air to control the engine speed and power. OK, so why not fit giant throttles and airways? Well, you don't just want a lot of air at the highest pressure available, you also want it travelling at high speed. This is because air actually weighs something, it has mass, which means it also has inertia. If lots of air was just sitting at the inlet valves at ambient pressure it would have to accelerate from standstill to high speed to get through the valves in the extremely short time that the valves are open. What you need lots of air to be travelling at high speed up to the valves just when they open, so it just charges in. This is where you have to find the right compromise where the inlet manifold airways are large enough to not cause too much restriction but small enough to keep the air flowing fast enough. Inlet manifold tuning can have a major effect too, but we won't go into that here.
The problem is made worse because the engine has to operate over a wide speed range. At high engine speed there's such a large amount of air going into the engine you can have large airways and still keep the airspeed at a reasonable speed. But at low engine speed the same large airway would cause the air to slow right down. This causes another significant problem. The fuel which has been squirted into the air stream won't mix properly to form a nice even explosive gaseous vapour. Instead it just drops down to the floor of the airway and you end up with a very weak gas mixture plus globules of fuel that won't burn properly, making the car undriveable at low speed. In a race car you sacrifice the low speed driveability, leaving a much narrower power band but with higher ultimate power. However you still need to keep acceptable response so you don't bog down as you accelerate out of corners.
I am going to bet that this mod is going to go to end up in the same category as 3" exhausts- great at certain rpm and load levels and lousy at others. Witness the butterfly exhaust valves installed in the later day Ferrari. For definite proof on the increased performance I decided to check with a Professor at the University of California at Berkeley [my wife] 
After four days of driving she stated " It's zippier and has more vroom-vroom". Hard [and maybe impossible] to argue with her.
Case closed! :lol:
After four days of driving she stated " It's zippier and has more vroom-vroom". Hard [and maybe impossible] to argue with her.Case closed! :lol:
MichaelP
Well-Known Member
Re: Manifold runner lengths
I mentioned the down side in my post that you referenced. The trade off is a flatter torque curve at high rpm. In other words, torque is improved at the lower end of the rev range (steeper curve), while torque on cam (above, say 3500rpm) isn't as good as with the stock intake runners.
I think there's a simple reason why BMW used the runners they did. Americans like low end torque, as with Detroit V8s. The Germans are more interested in what happens on cam, from say, 3500rpm and up, so the engineers balanced the performance of the L-jet motor slightly in favor of top end. It's often said that Americans want power from their cars, but they buy torque. It probably has to do with lower US speed limits and a bigger interest in drag racing.
Likely because it was an L-jet modification, limited to the late 70s and early 80s. I don't know enough about the early E24 crowd to know whether they get into fooling around with this kind of thing. The E12 group are serious tinkerers.
lloyd said:
I mentioned the down side in my post that you referenced. The trade off is a flatter torque curve at high rpm. In other words, torque is improved at the lower end of the rev range (steeper curve), while torque on cam (above, say 3500rpm) isn't as good as with the stock intake runners.
I think there's a simple reason why BMW used the runners they did. Americans like low end torque, as with Detroit V8s. The Germans are more interested in what happens on cam, from say, 3500rpm and up, so the engineers balanced the performance of the L-jet motor slightly in favor of top end. It's often said that Americans want power from their cars, but they buy torque. It probably has to do with lower US speed limits and a bigger interest in drag racing.
lloyd said:
Likely because it was an L-jet modification, limited to the late 70s and early 80s. I don't know enough about the early E24 crowd to know whether they get into fooling around with this kind of thing. The E12 group are serious tinkerers.
Re: Manifold runner lengths
Thanks for your response. I noted your observation about a flattened torque curve but all things being relative, I wonder if that couldn't be considered a plus, by a few.
You're probably right about the L-Jet connection being at the root of the manifold decision. But there may have been are a lot of other considerations. If I am not mistaken, the first injected E21's used the K-jet. E21's were offered with carbs too. For reasons unknown to me, the designers chose longer runners for FI - even for the Euro market. The selection does seem in step with your theory about North American desire for torque versus hp. Before I put my foot further in my mouth, I have no idea how using shorter (E9) runners might affect E21 performance but I'd bet using a 3.64 rear end ratio, or higher, might mask many deficiencies.
It is still unclear why, with the advent of the L-Jet, BMW continued to use the shorter E9-style runners for their burgeoning North American market. Maybe rear end ratios of 3.64 or 3.91 and Automatics are the great equalizer. Of course, BMW eventually changed to using several different style one-piece manifolds (but none resembled the subject runners).
Your explanation why this modification is not all that common is well taken. Stricter emission issues and relatively high costs may have also been major deterrents. The reasons may be even more self evident. They may be the same reasons why we don't hear of many common upgrades for the M Quattroporte. :wink:
Thanks.
MichaelP said:
Thanks for your response. I noted your observation about a flattened torque curve but all things being relative, I wonder if that couldn't be considered a plus, by a few.
You're probably right about the L-Jet connection being at the root of the manifold decision. But there may have been are a lot of other considerations. If I am not mistaken, the first injected E21's used the K-jet. E21's were offered with carbs too. For reasons unknown to me, the designers chose longer runners for FI - even for the Euro market. The selection does seem in step with your theory about North American desire for torque versus hp. Before I put my foot further in my mouth, I have no idea how using shorter (E9) runners might affect E21 performance but I'd bet using a 3.64 rear end ratio, or higher, might mask many deficiencies.
It is still unclear why, with the advent of the L-Jet, BMW continued to use the shorter E9-style runners for their burgeoning North American market. Maybe rear end ratios of 3.64 or 3.91 and Automatics are the great equalizer. Of course, BMW eventually changed to using several different style one-piece manifolds (but none resembled the subject runners).
Your explanation why this modification is not all that common is well taken. Stricter emission issues and relatively high costs may have also been major deterrents. The reasons may be even more self evident. They may be the same reasons why we don't hear of many common upgrades for the M Quattroporte. :wink:
Thanks.
gazzol
Well-Known Member
The question as to why BMW didn't conduct this modification themselves is in my opinion one of progress. The log style manifold was first used on the "big sixes" as first used in the E3's and E9's that we all love. The E21 was developed much later on and with different development criteria hence the modified intake runners, note all car manufacturers new developments which get more and more powerful with every incarnation.
The 2.8 and 3.0 Ltr engines will benefit very little from this runner conversion (assuming a standard max rpm) and they may even suffer a loss of low end torque (as has all ready been stated) the reason for this is that the manifold is not causing a restriction on these engines and if there is no restriction the only thing you will achieve by fitting bigger runners is reducing gas velocity and hence low end torque (also all ready stated)
On the other hand the 3.5 Ltr M90 or "L" block as some refer to it is a different kettle of fish. On this engine The manifold is a HUGE restriction and this is why this engine produces peak power at 5200 rpm and not 6000 rpm like the 3.0 Ltr and also why after peak power the power and torque drop off so suddenly. It is also why this engine has so much bottom end torque (the gas velocity is very very high)
Short runners=high rpm power verses long runners=low end torque.
This is a popularized over simplification. Every engine is different and whilst in general it is a fair assumption it is most definitely not the case with the M30/M90 and neither was it the case with the 24 valve racing engines in all their incarnations.
The big 6 needs long trumpets/velocity stacks/ram pipes, call them what you like in order to produce big power. Take a look at photo's of the racing engines and you'll see the intake length they used, this was after the M division engineers couldn't understand why they couldn't get the power they were expecting and spent hours of development time on the dyno. Interestingly this may be down to the capacity of the engine more than anything else as both the 12 valve and 24 valve engines used the long ram pipes.
The 2.8 and 3.0 Ltr engines will benefit very little from this runner conversion (assuming a standard max rpm) and they may even suffer a loss of low end torque (as has all ready been stated) the reason for this is that the manifold is not causing a restriction on these engines and if there is no restriction the only thing you will achieve by fitting bigger runners is reducing gas velocity and hence low end torque (also all ready stated)
On the other hand the 3.5 Ltr M90 or "L" block as some refer to it is a different kettle of fish. On this engine The manifold is a HUGE restriction and this is why this engine produces peak power at 5200 rpm and not 6000 rpm like the 3.0 Ltr and also why after peak power the power and torque drop off so suddenly. It is also why this engine has so much bottom end torque (the gas velocity is very very high)
Short runners=high rpm power verses long runners=low end torque.
This is a popularized over simplification. Every engine is different and whilst in general it is a fair assumption it is most definitely not the case with the M30/M90 and neither was it the case with the 24 valve racing engines in all their incarnations.
The big 6 needs long trumpets/velocity stacks/ram pipes, call them what you like in order to produce big power. Take a look at photo's of the racing engines and you'll see the intake length they used, this was after the M division engineers couldn't understand why they couldn't get the power they were expecting and spent hours of development time on the dyno. Interestingly this may be down to the capacity of the engine more than anything else as both the 12 valve and 24 valve engines used the long ram pipes.
Honolulu
Well-Known Member
induction pipes
Hmmmm, some interesting reading about induction tuning, but many seem to miss the main point(s).
I'm good with timt on the importance of runner volume and speed of the intake charge.
However I believe that effective intake (and exhaust) tuning require that the pressure waves caused by valves opening and closing, are reflected back from the "other end" (acoustically speaking) of either the intake or exhaust tract. If those pressure waves can be made to arrive at the correct time, one has probably achieved most of what can be done with that runner/header volume and cross sectional area.
In all/each/every engine, the optimum runner or header length depends on acoustics and the intent or target of the engine designer. I would NOT compare engines of different displacements, cylinder heads, body weight, trans and rear end ratios to see what might be useful. There are simply too many variables. It's entertaining, but ya gots ta work on one thing at a time. Each step change in the runners has the potential to change everything, and each step may require that other areas be optimized before useful additional modification can be made.
That said, I read a fair bit relating that a runner change does produce what is characterized as an improvement. For that person. For that car. For that driving style. On those roads. and .....
Hmmmm, some interesting reading about induction tuning, but many seem to miss the main point(s).
I'm good with timt on the importance of runner volume and speed of the intake charge.
However I believe that effective intake (and exhaust) tuning require that the pressure waves caused by valves opening and closing, are reflected back from the "other end" (acoustically speaking) of either the intake or exhaust tract. If those pressure waves can be made to arrive at the correct time, one has probably achieved most of what can be done with that runner/header volume and cross sectional area.
In all/each/every engine, the optimum runner or header length depends on acoustics and the intent or target of the engine designer. I would NOT compare engines of different displacements, cylinder heads, body weight, trans and rear end ratios to see what might be useful. There are simply too many variables. It's entertaining, but ya gots ta work on one thing at a time. Each step change in the runners has the potential to change everything, and each step may require that other areas be optimized before useful additional modification can be made.
That said, I read a fair bit relating that a runner change does produce what is characterized as an improvement. For that person. For that car. For that driving style. On those roads. and .....
I suggest forum members who have an honest interest in what works/what doesn't look up the Metric Mechanics site and download the big catalog, in it there is reading that discusses the benefit/virtue/basis for swapping intake runners from a 4-cylinder to a 6-cylinder intake system. 8)
MM wisdom
This limited discussion is good food for thought but hardly definitive. Not unexpectedly, the discussion presents general mathematical theory, leaving much room for real world variables The numbers suggest several interpretations.
MM offers the following formula: "broadcast power range" is best achieved where the Ram Intake Volume = cylinder volume. This presumes the term "broadcast power range" is universally understood and accepted, and that volume equaling volume achieves that desired result (however it is determined).
MM provides two volumetric measurements, declaring that 565 cc's total ram intake volume is ideal for a (hi flow) 3.5 liter M30 engine and that 465 cc's total [ram intake volume] is almost ideal for the 2.8/3.0 liter M30 engine. It would seem that 500 cc's total [ram intake volume] is ideal for the 2.0 liter M10 engine.
The “target” formula suggests 583cc’s ram intake volume is mathematically ideal for the 3.5ltr engine. The “target” formula suggests 500 cc’s ram intake volume is mathematically ideal for the the 3.0ltr engine. MM describes the first situation (+18cc’s) as ideal while the latter (-35cc’s) is almost ideal. By the use of the terms ideal versus almost ideal, It is unclear how deviating from these inferential parameters, up or down, or by other values, affects broadcast power range.
From that site:
"Early
Up until 1979, all BMW's used intake manifolds with wrap around "C" shaped runners. On BMW 2002 tii and 320i's, the manifolds were designed in the following manner:
* The plenum log holds 2 liters (Engine volume)
* The "C" Shape manifold runners to the back of the intake valve would hold about 500 cc (cylinder volume).
To create the broadcast power range in a BMW Engine the ram intake volume should be equal to the cylinder volume. Looking at the above information it is easy to see that 2 liters of intake charge will move into the plenum log. Then this charge is moved down the ram pipes and finally into the cylinders.
On early 6 cylinders (up to 1979), the manifold works the same.
* The plenum log holds about 3 liters.
* The intake runner to the back of the intake valve holds 465 cc.
* This ends up being an almost ideal ram manifold for a 2.8 - 3.0 liter BMW engine.
On a 3500 HiFlo Sport Engine we like to use a "C" shaped intake runner from a 4 cylinder manifold and use it on a 6 cylinder manifold. (See picture below.) The 4 cylinder runner holds 400 cc (versus 300 cc for a 6 cylinder) and has a straighter entry angle at the end of the "C". Substituting a 4 cylinder runner, the intake ram volume becomes 565 cc, which is ideal for a 3500 cc engine."
dp said:
This limited discussion is good food for thought but hardly definitive. Not unexpectedly, the discussion presents general mathematical theory, leaving much room for real world variables The numbers suggest several interpretations.
MM offers the following formula: "broadcast power range" is best achieved where the Ram Intake Volume = cylinder volume. This presumes the term "broadcast power range" is universally understood and accepted, and that volume equaling volume achieves that desired result (however it is determined).
MM provides two volumetric measurements, declaring that 565 cc's total ram intake volume is ideal for a (hi flow) 3.5 liter M30 engine and that 465 cc's total [ram intake volume] is almost ideal for the 2.8/3.0 liter M30 engine. It would seem that 500 cc's total [ram intake volume] is ideal for the 2.0 liter M10 engine.
The “target” formula suggests 583cc’s ram intake volume is mathematically ideal for the 3.5ltr engine. The “target” formula suggests 500 cc’s ram intake volume is mathematically ideal for the the 3.0ltr engine. MM describes the first situation (+18cc’s) as ideal while the latter (-35cc’s) is almost ideal. By the use of the terms ideal versus almost ideal, It is unclear how deviating from these inferential parameters, up or down, or by other values, affects broadcast power range.
From that site:
"Early
Up until 1979, all BMW's used intake manifolds with wrap around "C" shaped runners. On BMW 2002 tii and 320i's, the manifolds were designed in the following manner:
* The plenum log holds 2 liters (Engine volume)
* The "C" Shape manifold runners to the back of the intake valve would hold about 500 cc (cylinder volume).
To create the broadcast power range in a BMW Engine the ram intake volume should be equal to the cylinder volume. Looking at the above information it is easy to see that 2 liters of intake charge will move into the plenum log. Then this charge is moved down the ram pipes and finally into the cylinders.
On early 6 cylinders (up to 1979), the manifold works the same.
* The plenum log holds about 3 liters.
* The intake runner to the back of the intake valve holds 465 cc.
* This ends up being an almost ideal ram manifold for a 2.8 - 3.0 liter BMW engine.
On a 3500 HiFlo Sport Engine we like to use a "C" shaped intake runner from a 4 cylinder manifold and use it on a 6 cylinder manifold. (See picture below.) The 4 cylinder runner holds 400 cc (versus 300 cc for a 6 cylinder) and has a straighter entry angle at the end of the "C". Substituting a 4 cylinder runner, the intake ram volume becomes 565 cc, which is ideal for a 3500 cc engine."
x_atlas0
Well-Known Member
I have my doubts on much of Metric Mechanic's "math" and "testing" on some of their more odd enhancements, like the surface turbulence valves. That kinda throws everything else they do off, in my mind. Well, that, and the horror stories I have heard from more than a few people about their MM engine builds and more recent trans builds, ever since Blanton left.
lloyd said:
The math is not ambiguous at all. Ram intake volume and intake runner volume are different measures. Why should runner volume also include head port volume? Answer: it shouldn't, it is a different measure.
Thanks for cc'ing the section, while not definitive (who brought that up?) Rowe (writing at least 25 years ago) adds to our discussion.
x_atlas0 said:
well then, nevermind 8)
