Manifold Vacuum on 16V with ITB's...

[jondee86]

On my 16V smallport I have Silvertop ITB's mounted on a custom
fabricated tube manifold. Vacuum is sampled from all four inlet tubes
by way of small bore hoses (same size as OEM MAP sensor hoses).

At idle I am only getting 30 kPa of vacuum (70 kPa absolute pressure).

This seems a bit low, so has anyone got ITB idle vacuum readings to
compare ?? I'm going to check the reading from the brake booster
connection, as that comes from a larger set of manifold tappings. Just
to make sure the small hoses, to and from the map sensor vacuum
tank, are not causing a restriction.

Cheers... jondee86

[isac]

I have ST ITB's with T3 intake manifold and 68/70 kPa absolute pressure at idle.

I'm using Megasquirt with Alpha-n because under load pressure drop near to 100 kPa

Here's a video how idle
http://www.youtube.com/watch?v=aTmtrCVMm8c

and normal driving
http://www.youtube.com/watch?v=7v6eSI1G898

[jondee86]

Interesting !! I knew that ITB's didn't have much vacuum, and it's nice
to know that someone else has about the same result. I'm running on
a TPS only fuel map at the moment, but I would like to be able to get
some sort of manifold pressure fuel map working, so I can run try out
a TPS x MAP blend. That way I can use the Predictive MAP throttle pump
feature on my Adaptronic

Your engine looks very tidy... wish I had space to use that style of filter.

Cheers... jondee86

[alimonos]

can you give me the tps only map ? i am going to setup a greddy e-manage ultimate with itbs too ... :wink:

[jondee86]

alimonos Wrote:can you give me the tps only map ? i am going to setup a greddy
e-manage ultimate with itbs too ... :wink:

The map I have is just some line values I put in to make a startup map.
It was set up for VE tuning, with the first line 35%VE @ 0% TPS, rising
incrementally to 90%VE @ 65% TPS. Everything above 65% TPS is @
90%VE, and all lines have the same value from 0 to 8000 rpm.

The engine runs on this map with good A/F ratios, but I haven't tuned
the idle properly yet. The self-tune function has completed a few cells,
and they are not far off the numbers I started with. I really don't think
the map would be of any help with what you are trying to do. Better
for you to use a WBO2 gauge and adjust your settings until you get a
good A/F ratio.

Cheers... jondee86

[isac]

jondee86 Wrote:...

Your engine looks very tidy... wish I had space to use that style of filter.
...

This one it's a bit smaller

[jondee86]

Looks as so I have a cam timing problem Just moved the cams
around a bit, and now I have 45 kPa of vacuum. I'm going to degree the
cams and then try a few different settings. I'd be happy if I could get
around 55-60 kPa at idle

Cheers... jondee86