VDI and boost
 

I have noticed that many people keep the VDI closed when tuning with turbo applications

what would happen if it operated as normal?
Has anyone tried this?

the VDI is like a boost in an n/a app, but under FI could it still act as a boost, perhaps added 2 psi? or screw up flow?

My understanding of the VDI is it takes advantage of the supercharging effect that is generated in the intake.
IIRC it goes something like this: Due to the compressibility of air, when the intake port begins to close the column of air begins to compress from the inertia of the moving air column. This creates a local high pressure wave, which travels back up the intake runner. The intake plenum is designed in such a way to take advantage of this (VDI) by forcing some of this pressure wave down the other intake runner to the other opening port.

Again IIRC from Jeff's webinar that forced induction ruins this effect so there is no need to deal with it and causing a lean/rich situation. Opening the VDI at 7500 rpm is likely to take psi away as that area of the intake now needs to be filled with air.

yes -- I agree. Even with it in the closed position there is a small amount of air leakage between the runners, so I even closed mine with JB wield. Yea I guees I am anal.

I'll go out on a limb here ....

How do we know the supercharging effect is ruined by a boost intake charge?

Is it possible that a 10psi column of air collapsing on a closing intake port could create a local pressure increase and send it back through the VDI to the other opening port?

Or does the small amount of leakage negate the effect?

/start Flame suit shield

Thanks WCS, that is what i was wondering/thinking too

here is a dyno of what my car did, as far as I knew my tuner at the time, MM had left the VDI operating normally

http://farm8.staticflickr.com/7167/6...c581a422_z.jpg

Notice at 7200ish rpms there is a boost in powah

Nothing yet?
Team and MM must be visiting relatives

Bump.....

I look at what the airflow does at that RPM. If it looks bumpy (which is 90% of the time), I keep it closed.

lol, if MM is your tuner then what difference does it make?

It would appear that there isn't any need in opening it for FI, but it wouldn't hurt to try and see if it matters :dunno:

https://www.rx8club.com/attachment.p...1&d=1325259636



ps: and I've been back to work, the new job is rockin', more so since it is usually dead this time of year :smoker:


.

At the time he was, now he is not....

He's not the only option, but there is a ton of info on this website. Since you asked the question it would seem as though you may not have read as much as possible as thoroughly as possible.

perhaps, however this topic is one that had no dedicated thread that I found from searching, and it seemed everyone suggested it to be closed. case closed, however my experience showed that leaving it open may either add benefits or could cause a local boost spike and detonation could occur.

A ton of info on tuning? I think not, there is enough info to hint at tuning but most of it is shrouded in trying to over-complicate it, or people just playing on, I know but I am not telling, or people pretending to know, or the people assuming that everyone learns the same way...

My general perception is that you are lacking in basic concepts without even addressing the tuning aspect

sorry if that seems harsh, I was trying to convey this gently but you are backing me into the corner, lol

I appreciate your honesty I will admit I don't know as much as I could, and I am still learning, but I am not a complete dope, often times I over analyze a curtain point, which causes me to overlook other aspects, if there is something particular that you think may benefit me, some good searchable keywords would be great :)

Sorry I'm drunk
Did I miss the part where we said that the dynamic super charging affect is ruined by a boosted application?

No need to search now as we've already retrodden the path again, lol