Throttle body manifold choices

[320smithy]

I am seriously looking at the options using throttle bodies.

There are some manifolds around to fit DCOE type injector bodies ( like a jenvey setup ).
One solution is a manifold from south Africa, but I have seen a picture of a Weber one piece manifold on this forum some where.
Can any one point in the direction of where I would buy the Weber thingy ?

[steve_k]

search for the username turbobrown as in his sig pic is a link to a site with the templates for making your own manifold.

hope that helps.

[steve_k]

also if you what the weber manifold search for webcon.

[steve_k]

here you go
http://www.webcon.co.uk/shop/shopexd.asp?id=10510

[320smithy]

thanks Steve

[HairyScreech]

What are your intentions for the engine? As a lot of throttle body kits are deeply unsuitable for the m20. Even some of the kits intended for the m20 are still not good.

[320smithy]

Intentions are more power, more torque by letting it breathe and replacing the ECU. At some point it will go to a 2.7 /2.8

[HairyScreech]

So road use then, an m20 needs between a 35 and 40mm throttle body per runner and no more, even a 40mm may be too big for many applications.
The runners for a b28 specified for a torque peak between 3500 and 5500 along with best power is around 320mm (coincidental the same length as m50 manifold runners) with a bore of 41mm at the plenum tapering down at a 4 degree angle.

If you go too far away from this spec the results seem to be a loss of both power and torque. So pretty much if you want throttle to gain you anything you need to work to roughly this spec.

The manifold if.perfectly fine for a b25 with just an extreme hone, an un modified b25 will not really trouble this.
If a high performance b28 is in order then you may find it better to modify an m50 manifold or similar to fit the m20 as getting these sizes and lengths from throttle bodies seems to be quite difficult in the e30 engine bay.

[320smithy]

sorry, missing information, installation is a tarmac rally car.

when you say runner, where exactly this that measured from ?

[HairyScreech]

In this case from the head to the Bellmouth. Have spent a little while playing with this in simulation. It looks.like there is a very good reason the m50 manifold is the shape and length that it is.
For a tarmac rally car you will still be wanting plenty of torque at reasonable revs so aiming around those sizes will still be beneficial.

At this stage it would probably be money better spent on other areas if the engine.
What's the current spec?

[320smithy]

The engine and gearbox are the last areas to have any money spent on them.
So far both have been standard. The rest of the car is about where I would like it, it just needs more power and seat time from me. It has a proper welded in cage, fabulous shocks, skyline brakes front and rear. Some money could be spent taking some weight out of it.

The current engine is very tired so that is getting hooked out. I have a fresh one that has a cam and BTB exhaust so that is going in. By the time that gets a bit worn I will have a 2.7 / 2.8 put together. So this step is to put decent ECU and wiring in, and TBs. Still looking for a gearbox.

[HairyScreech]

Any idea what your looking at in terms of ecu? Several people have upgraded to m3.1 from an m50nv with gains for little outlay.

[320smithy]

Motec M800 because I have one spare.
There are plenty of other ECUs that will do just as good a job that cost less I know, but I happen to have one.

[HairyScreech]

When it comes to choosing parts i am a huge fan of the "already have one" technique.

So you will be going alpha-n anyway so there's no issues in terms of having to get specific sensors (maf etc) involved.

As the long term goal is 2.8 the best bet would be to size things for a 2.8, which means aiming for a 38-40mm throttle and the 320mm ish i mentioned earlier to catch the 3rd wave reflection.
I assume your intending to build the manifold yourself, if so there are a few bike bodies that fit the bill.
http://www.msportster.co.uk/question/in ... s-for-m20/
http://www.msportster.co.uk/itb-project/
This guy actually used to be a member on here when i first joined, gives an idea of why/how to build your own, also gives an idea of how long they actually need to be which when you look at off the shelf kits they just don't come close.

In terms of full off the shelf kits the dbilas kit comes with a minimum 40mm throttles and has runners that are just too short to keep the intake velocity up, so bye bye bottom end and throttle response.


Do you know what cam is in the b25?
I gather your road rally class is 2.5 and over, so going to a 2.8 is no issue later on.

[ross2009]

http://www.ebay.co.uk/itm/BMW-E30-M20-3 ... 2c664e31fa

[HairyScreech]

Has been for sale on the zone for a while, for throttles its not much cop really, needs a modified drain tube and a lot more runner length to work nicely.
Would be cheaper and easier to pay someone to mill off an m20 manifold and weld runner onto the flange, would allow you to keep standard fittings.

[320smithy]

I have been looking at the weber manifold ( above ) with

http://atpowershop.co.uk/catalog/6cyl-d ... p-187.html

To get the runner length surely it is just s case of getting the appropriate long trumpets ?

[HairyScreech]

the oil breather/return pipe is a bit odd on that dcoe plate, probably more work that fitting a flange to a cut off stock manifold.

yes trumpets will give a decent length, however the closer to the back of the valve the throttle body then the more disturbance in the air stream as it tries to pass the valve.
A bit more length will help the air settle down if your not running roller or slide throttles and the throttle response change will be minimal.
Also with the stock angle of the ports there is not a lot of room by the servo to get the trumpets in.

[320smithy]

Servo no problem !

[HairyScreech]

oh well in that case job on.
shoot for around 38mm, 320mm long and 4degree taper from the port size and you cant go wrong.
Might be worth seeing if you can build an enclosure that draws air through the bonnet with an intake in the high pressure zone near the windscreen for coldest intake air.

[Corolla]

Found some thing of a problem with this.

The manifold throttle side has 45mm diameter round shape to match 45mm DCOEs.

What is the best way to " blend " in 38 or 40mm throttle bodies ?
Also struggling to get up to the 320mm length as the manifold is only 25mm thick.

[HairyScreech]

This is pretty much the issue with all of the off the shelf stuff. We are only around the same capacity per cylinder as a .6-1.8.

My suggestion would be to take a look at my latest post in my thread where i have cut off a 320 manifold to use as an adaptor. Do that and then just make some pipes the correct length and find someone to weld the lot up, that way you can get correct sizes and lengths.

[reggid]

Found some thing of a problem with this.

The manifold throttle side has 45mm diameter round shape to match 45mm DCOEs.

What is the best way to " blend " in 38 or 40mm throttle bodies ?
Also struggling to get up to the 320mm length as the manifold is only 25mm thick.

i recon you could "sleeve" it, bore it out to the same OD as some tube with smaller ID than you need, then fit the tube with the smaller ID and then blend it in / port match as required. Otherwise some suitable epoxy with required chemical and heat resistant properties.

The dbilas is the same no wonder their systems are junk about 8-10mm too big in diameter for a B25 and much lower velocities that kills midrange in a big way