M20 ITB's

[digger]

2.8 stroker 10.5:1 with schrick 272

With that all you will gain is throttle response and a big hole in midrange may a bit extra up top but "a bit" is the key, something with less than 40mm diameter (38mm) with a system that kets you adjust the runner length and different plenum is what i'd be doing if going in that direction.

save ur money for an e36m3........seriously they are pretty cheap

[e3o]

Sounds like you are looking to build something like this http://www.r3vlimited.com/board/show...ht=Euro+muscle

Build thread here

http://www.r3vlimited.com/board/showthread.php?t=200342

[SkiFree]

Or like these fellow Ausi M20's I put up in my build thread.

Extrudabody kit + IE 3.1 stroker


S54 ITB's + IE 3.1 stroker

[der affe]

I have dbilas on my 2.7i with a 292° dbilas cam. It took MSII and a fair amoumt of fiddling with to get it to run pretty well. That being said, it would be much better suited to a much larger engine with significantly higher compression.

I am building (albeit slowly) a 3.1 for the car. It will be supercharged with an M90 roots blower running 17 lbs of boost.

To answer an earlier question, according to dbilas, they will take 20 psi of boost before the throttle shafts start to leak boost pressure.

[jules325i]

so all in all they are just asthetics because they are to big.

[jules325i]

Sounds like you are looking to build something like this http://www.r3vlimited.com/board/show...ht=Euro+muscle

Build thread here
http://www.r3vlimited.com/board/showthread.php?t=200342

That thread was a perfect build for me.
he even is running the willwood BBK that im interested in thanks!

[digger]

even though the extrudeabody are 45mm they seem like they slightly farther away from the head than the dbilas which when taper is included means the engine may not see them as large as the dbilas 45mm. Dbilas do have them with 40mm apparently which would suit the smaller M20's, clearing the booster seems to make some compromises.

For comparison the entrance to the stock runnners is 45mm and tapers to 35mm ovalish shape at the head.

[jules325i]

even though the extrudeabody are 45mm they seem like they slightly farther away from the head than the dbilas which when taper is included means the engine may not see them as large as the dbilas 45mm. Dbilas do have them with 40mm apparently which would suit the smaller M20's, clearing the booster seems to make some compromises.

For comparison the entrance to the stock runnners is 45mm and tapers to 35mm ovalish shape at the head.

So if i contact Dblias dynamics and there is a 40mm it could be made to work effeciently.

[digger]

So if i contact Dblias dynamics and there is a 40mm it could be made to work effeciently.

they will be able to tell you but will recommend the 45mm

http://www.r3vlimited.com/board/showthread.php?t=200342

this says there is

[Buttbump]

If you look at Extrudabody's site or give them a Call www.extrudabody.com they have 40mm @ 209cfm, 45mm @ 295cfm, and 48mm @ 345cfm ITB kits for the M20's???????????

The Size of ITB's depends on what your head flow numbers call for........ Good rule of thumb is 1.5 times the Head Port Flow numbers....... IE: if your getting 200cfm thru each port Extrudabody's 45mm flow 295cfm (According to Kevin) which is about perfect for that combination, but if your head only flows 100cfm then their 40mm ITB's @ 209cfm are simply too BIG........ sizing ITB's has little to do with Engine Size, and all to do with Head Port Flow Numbers with your specific Cam Lift/Compression...........

Now what OTHER causes can cause ITB's to be too big? Too Large of a CAM Lift or too Large Over Lap on the Cam....... As the Piston moves back up on the Compression stroke, the intake Valve is STILL OPEN, the RUSH of incoming air/fuel (IE: Velocity) is what's Holding the Intake Charge in the Cylinder, if the intake TRACT is too LARGE or CAM is too Large = Little to NO Velocity, and the Charge is pushed back up the Intake Tract in the form of REVERSION....

ITB's are not CONDOM's................ One size does not fit all.... :)

[digger]

If you look at Extrudabody's site or give them a Call www.extrudabody.com they have 40mm @ 209cfm, 45mm @ 295cfm, and 48mm @ 345cfm ITB kits for the M20's???????????

The Size of ITB's depends on what your head flow numbers call for........ Good rule of thumb is 1.5 times the Head Port Flow numbers....... IE: if your getting 200cfm thru each port Extrudabody's 45mm flow 295cfm (According to Kevin) which is about perfect for that combination, but if your head only flows 100cfm then their 40mm ITB's @ 209cfm are simply too BIG........ sizing ITB's has little to do with Engine Size, and all to do with Head Port Flow Numbers with your specific Cam Lift/Compression...........

Now what OTHER causes can cause ITB's to be too big? Too Large of a CAM Lift or too Large Over Lap on the Cam....... As the Piston moves back up on the Compression stroke, the intake Valve is STILL OPEN, the RUSH of incoming air/fuel (IE: Velocity) is what's Holding the Intake Charge in the Cylinder, if the intake TRACT is too LARGE or CAM is too Large = Little to NO Velocity, and the Charge is pushed back up the Intake Tract in the form of REVERSION....

ITB's are not CONDOM's................ One size does not fit all.... :)

first work out the runner size you need (cross sectional area 'CSA').......do this by getting hold of pipemax and some other simulation programs e.g. Engine analyser pro, dynomation and see what varying the runner bore size does to inlet tract velocity then target recommended velocities at whatever rpm you are after which in turn will give you the CSA you need, then choose what throttles compliment this. Doing this makes sure that with the head and cam you have things will be pretty close to what they need to be.

Excessive large runnners is shown to kill midrange according to the simulations which in reality is shown on the dbilas dyno plots with 45mm and larger throttles i have seen. Most people haven't the cam or exhaust setup to make the most of the bigger throttles so i wouldn't be sacrificing midrange for next to no topend, gain its best to err on the slightly small size IMO.

[e21jps]

ITB's on m20 are the goods, forget all the technical calculations and flows 40mm is about right, 45's can work but you need nice looong runners/trumpets but will always be a bit too big and have boggy midrange.

[fporro]

I could best describe dbilas 44mm itb's response to throttle as the way a sail would behave.

- If you were keeping certain amount of tension on rope as on partial throttle, then you cold feel the force of the wind increase and dreacrease as you manipulate it.
it raises or lowers it, as rpm increases and decreases.

- but, if wot is not reached gradually, then you'll feel resistance disapear and sail falls as on rpm drop or bog down feel.

I think all of this has to to with air speed velocity, it must be manipulated and keep at peak or within peak range during various throttle positions.

yzf r bikes have this fly by wire throttles with adjustable lenght trumpets




As many have said, the plenum could be improved up on.

There's not much talk about distance from valves to trottles, extruda and dbilas both make adaptors and yes, they both transition to match head port.,
there's 40mm units in dbilas catalouge under 323i engines.

I have a question or 3,

- itb's have a tappable port, just in front of throttle plate, would this be a acceptable place for map readings?

- if so, all 6 cylinders ? or just one reading., i'm thinking of tapping all 6 to take readings from dbilas plenum, a carbon airbox I bought and that crazy pvc pipe intake I made.,
been thinking one huge trottle infront of airbox to manipulate overall intake pressure and itbs in conjuction with adjustable trumpets manipulating air speed. scweets.

- could this readings be use to supplement ecu, someone posted that map's and itb's don't tune well together.

and last but not least, does anyone has the dbilas chip ?

[tinkwithanr]

Interesting thoughts. I know there have been a number of 'adjustable' length intake manifolds, though they tend to just be three or four different positions as opposed to the completely variable system on that bike.

It would also be interesting to see the benefits, if any, the addition of a larger throttle plate upstream from the itb's.

[TobyB]

Plenums are underrated...

Me, I'd take the S54, thank you very much, and hit the track.

And then not worry about breaking rockers ever again.

t