Show and Tell . ITB’s please.

[irdave]

5 minutes ago, Simeon said:

How do you use a MAF with ITBs?

 

Is it installed with a common air intake box / plenum?

 

Yep.  Put in in place where the s14 uses the AFM.

 

S14 has 28cm? trumpets inside the airbox...  It's not open like a rack of carbs.  Same thing with the s54 in the e46 m3.  Huge airbox.

Edited May 29, 2019 by irdave

[Dudeland]

19 minutes ago, irdave said:

 

And we have the added problem of being at altitude, and changing altitude pretty quick going up- so Jim says MAF- I bought a MAF.  You guys are getting me excited to get everything installed!

How do you manage a MAF with multiple intakes?  A common intake before the ITB's? 

 

Sorry, i should have refreshed the page before asking the question. 

 

Edited May 29, 2019 by Dudeland
Sorry

[AustrianVespaGuy]

4 minutes ago, Simeon said:

How do you use a MAF with ITBs?

 

Is it installed with a common air intake box / plenum?

Yeah as long as the airbox is tight, MAF is the most ideal as it directly measures what you want to know: mass of O2 entering the engine.  Alpha-N is probably the easiest/simplest method for ITBs, but it suffers most from changes in air density (changes in temperature and/or pressure, e.g. altitude).  Speed-density while not quite as accurate as MAF is still pretty good and a bit simpler, which is why it's generally the 'norm' for common plenum systems.  I think the trick with MAFs is making sure you really know it's output voltage response curve since they're non-linear and vary from sensor to sensor, but if you can handle that it's probably the best route for ITBs, though both AlphaN and Speed-density should be able to be made to work pretty darn well also, so just pick where you think you'd most like to spend your tinkering time!

[Dudeland]

I found an awesome setup!!!.  Turbo, efi, launch control 4wd leather seats.    Just kidding.. kinda.  I think I need to think about a real daily.   Just watched Might Car Mods.  

 

Episode

 

For sale: 

 

https://wwwb.autotrader.ca/ico/volkswagen/golf r/calgary/alberta/19_11094727_/?showcpo=ShowCpo&ncse=no&ursrc=pl&urp=6&urm=8&sprx=-1

[Grover]

It has been quite a few years since I built mine (car subsequently sold) but I used TWM ITB's run via MegaSquirt. I used a common vacuum tube to pull a steady signal so I could run off of MAP, which I found a much better option than AlphaN. I know that folks have developed systems which run a mixture of these two these days and this is probably a better set up. Initially I ran with just air horns and crude filters but later switched to an airbox. On the dyno it showed basically zero impact from an hp standpoint (when switching from airhorns to airbox) but maybe would change once things get warm under the hood in real life driving, I don't know.

[Dudeland]

5 minutes ago, Grover said:

It has been quite a few years since I built mine (car subsequently sold) but I used TWM ITB's run via MegaSquirt. I used a common vacuum tube to pull a steady signal so I could run off of MAP, which I found a much better option than AlphaN. I know that folks have developed systems which run a mixture of these two these days and this is probably a better set up. Initially I ran with just air horns and crude filters but later switched to an airbox. On the dyno it showed basically zero impact from an hp standpoint (when switching from airhorns to airbox) but maybe would change once things get warm under the hood in real life driving, I don't know.

Who made the ITB system?  

[jimk]

Attached find my observations about the manifold pressure with ITBs and a common manifold.  This not to say either is poor or good, just observations.  The paper was prepared for a person with an altitude issue to describe the pressure issue.

 

Note that because the pressure is different in each iTB runner at any given time, some air shuffles between runners thru the sensing tube.  A large equalizing tube between runners might help to minimize the pressure pulses.

 

Attached is the engine under discussion.  Those are not carbs but air valves that look like carbs.

Effects of Altitude on the Tune.pdf

[zinz]

1 minute ago, jimk said:

A large equalizing tube between runners might help to minimize the pressure pulses.

 

also slowing the response, somewhat, as you and I have discussed in the past.  Probably not enough to notice, though.  This is where we see large vacuum canisters on some older injected cars? .. maybe modern cars, too.. what do I know about them, though.

 

...love that flathead.  That's beautiful.

 

Ed

[jimk]

6 minutes ago, zinz said:

also slowing the response, somewhat,

Zinz,

I was not clear, the equalizing tube would need to be one different from the MAP sensing tube.  It's purpose is to shuffle air between runners and tend have the effect of a common manifold.

 

Back to the issue of IAC, the S14 has the tube built into the throttle body assembly.

 

 

Edited May 29, 2019 by jimk

[zinz]

I'm good at muddying the waters, Jim.  I think you and were looking at the common vacuum line I made between my Solex DDH sidedrafts, providing signal to my 123Ignition. You commented that a larger tube would smooth the pulses between cylinders.  

 

Ed

[revolve40]

@jimk would a Korman/IE intake manifold serve this purpose? They have a hole running through each runner (not my pictures).

 

Edited May 29, 2019 by revolve40

[tzei]

It might but i still would like to see how that flows vs. standard.

[jimk]

For MAP sensing on ITBs, here is a device developed as a project at MIT to overcome the issue of poor vacuum readings.

https://github.com/jharvey/MultiMAP

(some assembly required )

 

Edited May 29, 2019 by jimk

[xr4tic]

I'm a big believer in MAF setups, it measures TRUE airflow, not a guesstimate made up by the ECU based on what you think the VE table is.

 

I had issues with my ITB setup as well (motorcycle ITBs with MS1 Extra)

 

I ran Alpha-N, couldn't get a good MAP signal.  I did try hybrid-AlphaN which was slightly better.

Also Issues with cold tuning - rough idle.  I tried to plumb in an idle valve, but couldn't get it dialed in with the MS.

 

The ITBs pointed into the grill, so airflow changed based on speed.  3000 RPM in 2nd was completely different than 3000 RPM in 4th (not a problem with a longitudinal motor)

 

My vacuum log/idle valve attempt:

 

I used a Carb-Tune to sync the throttle bodies.

 

[steve k.]

It has been a while since I built mine and the car has been gone now for a while.  It took some time to sort things, but it ran great once completed. ITBs were done by Extrudabody. Unfortunately, the guys do not exist anymore.  ECU was Electromotive TEC GT. 

 

 

And more photos from the for sale ad