E30 #2: 1990 Delphin: RHD ITB M20

[tinkerputzer]

Really nice work man. You've managed to keep the engine bay quite tidy :up: Great results and the sound from that 1-4 dyno pull is bonkers. Can't wait to see how those screens compare to open trumpets.

Are you still planning to try and fit the M3 wiring harness cover?

[318aye]

i retained all of the length i had when i added the box. This was one of the goals, as i lost some midrange torque 4000-5500 with a runner length 2" shorter. i had to trim about 10-15mm iirc with the straight trumpets to clear the hood so the trumpets were trimmed slightly before adding a box. you can test a shorter length by removing the spacers so you dont need to modify the trumpets

Duly noted. Now that I have access to proper carbon molds, I'm really sizing up the design work you did. Will probably message you in the coming weeks.

Really nice work man. You've managed to keep the engine bay quite tidy :up: Great results and the sound from that 1-4 dyno pull is bonkers. Can't wait to see how those screens compare to open trumpets.

Are you still planning to try and fit the M3 wiring harness cover?

Thanks! Believe it or not, it's actually very mild at idle and under cruising loads. I would like to get those covers in soon. I think it may end up being a moot point when/if the airbox route happens, as it looks like the harness will need to be pinned up further. I found out today that a friend's company actually builds CNC'd foam molds for composites all the time, and they have plenty of left over carbon :devil:. I'm very tempted to get started on that end of things immediately. We'll see how the mid trumpet screens work first though.



Car is an absolute riot to drive, even with the filters on. Fixed a few more small issues before I left the shop. Fenders rolled (no more tire shaving), and door card bottoms fixed. Made the drive home with no issues.



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[318aye]

Totally did crank too hard on the trumpets. No serious change, but you can see that it's given a bit on the inside (look for the light areas where the clamp joins). Easy on those allen keys!




So I used Rama's available "Manifold Plate" drawing from the site, but somehow the drawing didn't scale correctly or something. I also ran out of gasket material (Felpro PN 3157), so tomorrow will involve another trip to the laser, and hopefully correctly sized parts. Should have brought a trumpet.

I decided to go ahead and try making a set to work out any bugs ahead of time. Took gasket number one, applied black RTV. Applied circular screen section (needs to be circular, diameter larger than the port, but smaller than the outside of the trumpet clamp so that mounting the trumpet clamps down on the screen). Applied second gasket. Install beneath trumpet clamp. Voila. Will probably see the dyno Friday afternoon. If the lower screen only filters test well, I'll try screens with foam next week and see how much of an impact the foam density has on power.

Assembly pictures:









The purpose of this whole experiment is to try and get insight into how much of the 24 whp gain from the ITB's was due to the venturi effect from the trumpet mouths, how much was from simple flow increase, and how much was from the harmonic wave effects that the runner length creates. If the car performs better with low screens (in a theoretically more laminar flow (don't actually know this, serious assumption time)) I'd say the venturi effect is a serious contribution. If nothing changes, and the car still makes shit power with on-trumpet filters, maybe it's more likely that the harmonics are the reason for the increased power. None of these variables are controlled very well, so it's primarily speculation.

Starting to do my homework for the airbox. I want gloss finish carbon. Have already found a mold/composites place through a friend that should be able to save some costs. I may also have a line on a FARO arm with the laser scanner. I'd like to remove the trumpets and runner extensions, and have the bay scanned. This will allow me to accurately model the airbox, make design changes, etc and not waste money on bad prototypes. If that works out, I'll host the models somewhere.

Here's the drawing for the gasket (mm). I oversized the port hole so as not to obstruct, and undersized the outer "skirt" to keep it from being overly visible.

[MkII]

Your dedication to this build is amazing, great work! That engine bay looks amazing!

[brian52555]

Does anybody make an off the shelf airbox/plenum for these ITBs? Or would it be possible to adapt something from an S54 etc.?

[318aye]

Your dedication to this build is amazing, great work! That engine bay looks amazing!

Thanks! I'm really happy with it so far.

Does anybody make an off the shelf airbox/plenum for these ITBs? Or would it be possible to adapt something from an S54 etc.?

Not as far as I know. There are a few examples (Digger's, etc) and I've seen one in carbon. Still doing research. Will post the examples I find. S54 box would probably be too big, but who knows. When I get the bay scanned I'll see if I can find a model for the E46 CSL box.

Had the car detailed today, to say it needed paint correction would be an understatement. Thanks to Tyler at Super Mobile Detailing, car looks amazing.

[Matt-B]

To be honest, i never really cared much for m20s, since i never owned an m20 car, you have changed my opinion. I just went through your whole thread, and the time, detail, and effort you put in to such a small part of the car is amazing. The picture in post #151 makes me wish i owned an m20. Truely well done sir, im beyond impressed....

[pandaiswong]

You've inspired me to go ITB on my car.

[digger]

Rama was working on making some airboxes a while back, there was a GRP one made which from memory required somewhat shorter trumpets but only recently i saw this which might be the CFRP version of the same. maybe contact him, he may have tested it and found it works really well

[brian52555]

Thanks for the details on airbox - thinking of pulling the trigger on Rama's ITB kit soon, will ask about airbox.

[goarmy]

Good call on the air box but it is still the same. You must try and have some pressure in the system I suggest to box your filter like the original manufactures do.

Looks like you made some nice progress, keep going!!:)

[goarmy]

Think maybe a little cut and paint in the future ?😀

[Bimmer_man]

This is epic

Rama was working on making some airboxes a while back, there was a GRP one made which from memory required somewhat shorter trumpets but only recently i saw this which might be the CFRP version of the same. maybe contact him, he may have tested it and found it works really well

[brian52555]

Digger maybe you should make and sell your airbox?

[e30 gangsta]

The problem I see with most e30 itb kits is the lack of an airbox, therefore forcing you to run open stacks, or loss power running filters/screens. When you run no filters dirt sand etc get into the combustion chamber and over time it will wear the cylinder walls.

Not good for a daily driven car or a car you want to get miles out of. Itb kits would be way more popular if they came with a prefabbed airbox so that you do not lose any power, and have the increased benefit of actually filtering the air before it goes into your engine, while also making more power due to cooler denser air.