M20 ITB's

[whodwho]

I was involved with a Dyno tuning session this weekend with a M30 with ITBs, started out SD and ended up Alpha-N. On SD you could get it running ok @ idle and WOT but rough thru the transition.

[nando]

Local Aussie M20 nut is doing a roller rocker and cam combo, I reckon if he sold those in kit form I would buy that.

My take on ITB's is this. I wanna do triple 45 dcoes. I know webers pretty well, and just seems easier to setup than standalone ITB injection.

no way. all you need is a vac manifold to pull a signal off each TB. run speed density.. done. you can have the fuel map tuned in an afternoon.

Historically, VAC has had lash pad hardness issues.

Lester Owen doesn't do M20, does he?

I ran the Ireland 'Heavy Dooty' M10 rockers on the 2002 with notable success,
given the reasonable cost.

Wonder if KM Cams will do an M20 steel rocker?

t

the M20 IE HD rockers are good. there was a batch that had some flashing issues but it was more of a matter of cleaning them up rather than poor strength. Somebody had a set x-rayed and the casting quality was excellent.

IMO everyone always freaks out about M20 rockers and says "billet!!!". But there really aren't any that are worth the price they cost. the HDs are only $300 and probably work as well and maybe even better (given how many have adjuster or pad issues). heck even a brand new set of stock/OEM rockers will take a lot of punishment. select proper valve springs and keep them adjusted. No issues.

[clarkson]

Local Aussie M20 nut is doing a roller rocker and cam combo, I reckon if he sold those in kit form I would buy that.

My take on ITB's is this. I wanna do triple 45 dcoes. I know webers pretty well, and just seems easier to setup than standalone ITB injection.

[TobyB]

Historically, VAC has had lash pad hardness issues.

Lester Owen doesn't do M20, does he?

I ran the Ireland 'Heavy Dooty' M10 rockers on the 2002 with notable success,
given the reasonable cost.

Wonder if KM Cams will do an M20 steel rocker?

t

[clarkson]

Yes stupid money:

VAC - M20 Billet Rocker Arms, Set of 12
Preorder Now!
VAC-PRA-M20
$1,799.95

I wonder how many they have sold.

[Herr Faust Schinken]

Vacs i think stupid money

[clarkson]

wow those are nice looking rockers.

Porsche Adjusters? What's the damage (price)?

[tinkwithanr]

Ha, fancy seeing you over here Toby.

Broken Rockers you say?





;)

[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

[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.

[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 ?

[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.

[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.

[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]

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