NA is best - 3.1L M20 w/ ITB's

[LateFan]

How does that or the buffer / canister idea work? Do you get a constant vacuum number by doing that, even with the various port pulses?

I love these threads. You guys are amazing.

[digger]

the plenum (volume) that connects each vacuum hose helps dampen the sharp pulses, kind of averages them out so to speak to try and create a more uniform vacuum reading.

[LateFan]

Is it consistent, or is it cycling up and down within limits?

[digger]

it still cycles, just less than would it taking a reading off a single runner.

most people steer away from MAP based tuning with ITB because even if you have a rail the pulsing still exists. the pulsing will depend on the cam, small duration and less overlap the nicer the signal

[nando]

Just FYI (and many in this thread already know) the S54 come with something like this stock.

[Northern]

How does that or the buffer / canister idea work? Do you get a constant vacuum number by doing that, even with the various port pulses?

I love these threads. You guys are amazing.

Here's an ultra shitty pic of how more cyls will dampen the pulses, if you're more of a visual person...

Disregard the scale on the y axis and the timing of the sine wave

[LateFan]

Very good. So a plenum chamber on a typical intake manifold eliminates most of that pulsing?

I should go out and look at my old Alfa - it has dual webers. But I think it has weights and springs for advance in the dizzy, so maybe no vac fittings anywhere.

[digger]

Very good. So a plenum chamber on a typical intake manifold eliminates most of that pulsing?

I should go out and look at my old Alfa - it has dual webers. But I think it has weights and springs for advance in the dizzy, so maybe no vac fittings anywhere.

yes, if you mean the actual intake runners and plenum rather than the little vacuum hose and vacuum rail they work similar

[Raxe]

Whew! Long day but a good one.

First started by disabling the vacuum to the FPR like ForcedFirebird recommended. It made a pretty huge difference in idle mixture stability, immediately richer but way less jumpy.

Synced the throttles properly using the synchrometer and set the idle at 1000RPM - I found 900 a little too 'slow' and unresponsive.



Final assembly pre-box:





Onto the airbox. Fitment is obviously really tight, I know RHD is coming out with a revised backing plate to help with clearance but mine is fitting alright I think. Needed to modify the cylinder 6 trumpet to fit the box overtop but it works.

I had a new Dinan E36 M3 air filter sitting around that I had been saving for years without a use, amazingly it's a perfect fit... very lucky. I wouldn't mind extending the intake down further behind the headlight in the future and possibly making a heat shield, but for now I'll leave well enough alone.







Loaded up some new numbers and took it for a drive! Everything is working pretty well, still need to fine tune the idle as it's still trending very rich but cruising is stable and acceleration seems good. I'm taking it easy at this point until I'm more confident all is well, but it's very driveable. Now to figure out VEAL and see what it can do.

Still a few things left to do besides tuning:
- Get the tachometer working, far as I can tell I need to wire it via the MS accessory port but maybe I'm just missing a simple setting? :\
- Install the catch can and hoses
- Find a permanent home for the IAT
- Clean up engine bay

Video of it running:

https://streamable.com/ah95h

[digger]

sounds like it is coming along nicely, digging the matte black airbox to it looks more in theme

[Raxe]

Just hit 100km on it today and feeling a lot better about it now. Most of the quirks have been ironed out and it's idling and driving well. Cold starts are still tough, I'm inching towards a good WUE formula but after the initial start it's fine for the day. Idle is still on the rich side as well, but I'm hoping I can improve that by getting the injector dead time figured out.

Only new problem I've had come up is the (new) brake booster check valve is getting increasingly noisy, I'm wondering it if too has to do with the pulsing vacuum but I'm expecting it's on its way out already.

Pic from today after a nice drive:

[digger]

noisy? the check valve makes no noise, or is it something inside the booster making whooshing noise? something unavoidable is that a 288 with ITB is going to have lower vacuum than stock

[parkerbink]

Very nice, what headers are those?

[Raxe]

noisy? the check valve makes no noise, or is it something inside the booster making whooshing noise? something unavoidable is that a 288 with ITB is going to have lower vacuum than stock

It's making a "tink tink tink" noise under braking, only at a stop or coming to a stop... confirmed it today with a stethoscope, it's loud enough to hear inside the car. Pretty strange, and it goes away immediately under load. I might order another to eliminate the possibility of a randomly faulty valve as they're cheap enough. Braking force is adequate, no issues with the assist other than the unusual noise. I suppose it could be from the booster itself, though it seems quiet with the stethoscope.

Very nice, what headers are those?

Thanks, they're IE shorty headers.

[Schlander]

Could you post your IG and VE table? :)