How do you tune cars with ITBs? Are they only ran in open feedback?

>implying /o/ actually knows anything about cars

>>17487582
RPM/throttle position map. There's precious little manifold vacuum to measure, and it's destroyed pretty quickly when the throttle butterfly is opened.

>>17487671
That seems pretty garbage considering it doesn't reflect load or elevation. Lambda sensors are not exactly fast acting or super dependable devices by themselves.

I'm guessing it's fine since theyre meant for select race events, but still creates a lot more factors to account for.

File: DSC_0245.jpg (726KB, 2464x1632px) Image search: [Google]

726KB, 2464x1632px

>>17487732
>I'm guessing it's fine since theyre meant for select race events


He doesn't know some shitboxes came with them from the factory

File: Assembly.jpg (49KB, 863x523px) Image search: [Google]

49KB, 863x523px

>>17487582
If you want to tune using manifold pressure (vacuum), you hook up a vacuum line from each runner, and connect them with a vacuum block which you attach the MAP to.
MAF is quite hard since you don't have the room for accurate measurement.

Most people just use throttle/RPM (Alpha n) to map ITB's and it works fine.

>>17487629
>Implying I haven't just designed a set from scratch

>>17487732
You'll use an incar Lambda readout, and make sure that doesn't get too far out of whack. You could compensate elevation y using a MAP, and load is pretty well-sorted by alpha N.

>>17488190
Looks nice. Variable runners?

That's about what I thought. Im guessing MAF wouldn't work without a plenum to dampen oscillations like in >>17488133

>>17488308
There is no MAF in this photo >>17488133

>>17488323
Indeed, but there is a reservoir in front of the throttles. I was pointing out how that might make it possible.

>>17488308
Looks like shit, it's just the concept rendering. It was basically just a rough sketch for my instructor.

>Red: flange (designed to fit C20XE)
>Blue: adapter (from port shape to round)
>Purple: extension (variable, to optimalise Helmholtz)
>Yellow: stabiliser
>Green: Placeholders for Jenvey ITB's

I've since improved the design, it now fits a C20XE (which my customer has) and a 1.6 Zetec from a '93 Mondeo (I've got a spare on an engine stand to demo a 3D-printed model on), depending on the flange and adapters. Theoretically, I can now scan any flange and have a 3D-design ready to mill within 30 minutes. Instead of the purple extensions, I put the throttle bodies as close as possible to the ports, so right behind the adapter blocks. To still get the resonance right, I'll use 3D-printed velocity stacks.

>>17488364
That's pretty fleshed out. What's your line of work?

Also, how are you 3D printing? When I 3D printed a flange to tap a MAP for our research engine, I found the thermal expansion was shite with metal constraints and got mad leaks. It wasn't great plastic though so that didn't help.

You have a cool project, anon. Most people I knew who took on variable runner projects abandoned them due to cost or complexity.

>>17488422
>What's your line of work?
I'm just a student (mechanical engineering).

>Also, how are you 3D printing?
Since it'll be just a prototype (for now), PLA in our school's Ultimakers. If it ever gets out of prototype, I'll just make it out of billet (we've got a four axis mill I've been itching to use). For the stack I'm looking to get a sponsorship with a local company that's working on a filament called _HT, and that should fix the thermal expansion. If not, the Jenvey throttle bodies I'll use will have a rubber O-ring to guarantee a good seal.

It's not really a variable runner though, since I can't change it on the fly. I'll be able to rapid prototype velocity stacks though, so tuning should still be pretty easy. Where you originally had to make them by hand, now I'll be able to crank them out within about an hour each while I can do other stuff.