engine and drivetrain 320i (E21) Throttle Body

[Healey3000]

Hi,

 

I realize that most EFI implementations using the E30 318i M10 intake use the M20 throttle body.  However, is the one off the E21 320i large enough for the M10 on our 2002's?

 

Thanks.

[jimk]

Yes, the M20 is overkill.  So long as you can make near atmospheric pressure MAP reading at wot, redline, a bigger throttle body does nothing but take up space.  Atmospheric pressure in the manifold can never be achieved in a NA setup due to the physics of air in motion.

[bluedevils]

I would stay with M20 TB, makes nice low-end torque. Hundreds of fellows are using it for EFI conversion with good results.

[txmatt]

the e21 tb will not have a provision for a tps.

 

On the plus side it does have a idle adjustment screw.

 

Larger TBs change the throttle response (for the better, I think)

[Healey3000]

Thanks folks.  I picked up an M20 TB along with a TPS from an M30 535i.  Bolts right on and provides the resistive output needed by Megasquirt.  Now I just need the adapter and have to figure out how to connect the throttle.

[Healey3000]

the e21 tb will not have a provision for a tps.

 

On the plus side it does have a idle adjustment screw.

 

Larger TBs change the throttle response (for the better, I think)

Hi,

 

Larger TB's actually degrade the response since a small angle creates a large opening, resulting in a slight loss of manifold vacuum.  Best of all worlds is a set of progressive butterflies.  In my junkyard foray today I saw an interesting TB on an E36 318i.  It has one small and one large butterfly, progressive.

 

I think that particular TB would be excellent for the M10 but the shape of the air intake is very strange.  If an OEM bellows isn't available, it will be difficult to connect to it.

[jimk]

Thanks folks.  I picked up an M20 TB along with a TPS from an M30 535i.  Bolts right on and provides the resistive output needed by Megasquirt.  Now I just need the adapter and have to figure out how to connect the throttle.

Check the TPS that it is a rheostat not a switch.  Rheostat type is scarce (and expensive to buy new).  I have two in the basement.

[Healey3000]

Check the TPS that it is a rheostat not a switch.  Rheostat type is scarce (and expensive to buy new).  I have two in the basement.

Hi,

 

It is, as it's the 6-pin type from the M30.  That's what I meant by resistive, as opposed to the WOT/Idle type.  Never did understand how Motronic managed without true TPS.  Mass flow is well and good, but...

[jimk]

Early Motronics didn't care how fast the throttle was moved, it never had the throttle pump feature.  They only used the idle position (to turn on the idle control function and maybe an idle table for fuel at idle) and the WOT switch to turn on a WOT fuel table.

Looks like you got the correct TPS, the switch contacts aren't needed.  I used one of the TPS's I have on a E30 IX with a Haltech ECU.

[txmatt]

Hi,

 

Larger TB's actually degrade the response since a small angle creates a large opening, resulting in a slight loss of manifold vacuum.  Best of all worlds is a set of progressive butterflies.  In my junkyard foray today I saw an interesting TB on an E36 318i.  It has one small and one large butterfly, progressive.

 

I think that particular TB would be excellent for the M10 but the shape of the air intake is very strange.  If an OEM bellows isn't available, it will be difficult to connect to it.

 

 

By "degrade" I take it you mean that it reduces the amount of pedal travel before you have essentially WOT in terms of flow and manifold pressure. I like the response of the larger TB as do many others.

 

You can adapt whatever TB you want with a set of flanges and some tube. For the other end, towards the filter, I think this would do what you need:

http://www.turnermotorsport.com/p-7286-intake-rubber-boot-from-throttle-body-to-manifold-e36-318i-96-98-z3-19.aspx

[TobyB]

 

 

 I saw an interesting TB on an E36 318i.  It has one small and one large butterfly, progressive.

Yeah, the down side to that one (I have one on the 318i) is that you FEEL the large butterfly when it comes in.

As in, there's a defined notch in the pedal pressure.  And the EFI on my car is still AFM, which is pretty

clunky relative to something modern.

 

Does seem to help economy, if you can stay out of the large butterfly.

 

t