VW 16v ITB vacuum and ISV question...

JSchlappi82 · Post by **JSchlappi82** » Mon May 08, 2006 5:29 am

I have a VW 1.8 16v engine with ITB and CIS at the moment, but i'm going to megasquirt.

My itb's didnt have a vacuum supply, so i drilled 4 holes in the manifold, one for each runner, between the throttle plates and the valves.
I've put some plugs in the holes, about 5mm, and attached a hose to them, which goes to a little "canister" from where the vacuum goes to the brakebooster.
The other side of the "canister" used to go to the ISV, but then i lost the brakebooster, as the other side of the isv went to "atmosphere" (manifold between the throttle plates and the CIS air meter)
I blocked this end with a hose and bolt, as seen on picture. ( goes under the "manifold")

When i'm converting to megasquirt, will the vacuum be sufficient for the MAP sensor, if i attach it to the "canister" and will i need the ISV for idle control? (And how should i attach it?)

I the first picture you can see the "canister" and the hoses, with the orange arrows.

The second picture shows the ITB's, the orange point is where i drilled the holes for the vacuum. Not on that point, but it will give you an idea. The holes and plugs are on the botttom as mounted.

I've seen pictures of the bike throttlebodies used, they appear to have a similar vacuum plug, but i didn't see anyone use this for the MAP sensor.

Greetings, soon to be a dutch megasquirter...

http://members.home.nl/schlappi/PICT002 ... 20view.jpg
http://members.home.nl/schlappi/motorke ... 20view.jpg

keithmac · Post by **keithmac** » Tue May 09, 2006 2:19 pm

You can`t run the ISV with that setup, it needs a common throttle plate to bypass. Canister should be fine for map input but most people on itb`s run alpha-n via the tps.

Karl_Skewes · Post by **Karl_Skewes** » Tue May 09, 2006 4:12 pm

ditch the isv.

run the 4 map lines into one, and then if it pulses use a some sort of dampener, either fuelfiler+migtip combo or a carb dampener(possibly drilled out with 1mm drill bit if it dampens map too much).

If you still want to run a brake booster, tap one of the 4 manifold runners again for a feed to that.

However, after a year of different ITB setups on different motors I've given up on brake boosters and dropped them from my setups. I just don't get the same sort of assistance as per a single throttle manifold, and light car so why bother.

muythaibxr · Post by **muythaibxr** » Tue May 09, 2006 6:28 pm

keithmac wrote:You can`t run the ISV with that setup, it needs a common throttle plate to bypass. Canister should be fine for map input but most people on itb`s run alpha-n via the tps.

Tuning with alpha-n is insufficient if you're worried about any kind of emissions laws.

I'm working on testing some code that allows you to use two different maps and algorithms, and allows you to switch between them based on throttle position or MAP.

I'm going to be running Speed Density up to about 20-25% throttle position, and then alpha-n above that.

Ken

JSchlappi82 · Post by **JSchlappi82** » Tue May 09, 2006 10:09 pm

I was thinking about the 2 different maps, speed-density at low tps, and alpha-n at higher tps, but i didn't think it was possible... Keep me updated.

@Karl_Skewes: i still need the brakebooster, when i was using the isv it was really hard braking, i really need it.

Is it possible to check my vacuum? You can check it for pulses or for resolution i heard? Is there someone who can tell me how to do this?

Greets, Joris.

Karl_Skewes · Post by **Karl_Skewes** » Wed May 10, 2006 12:56 pm

ok, if you want to keep it, then simply tap one of the manifold runners for a feed for your brake booster.

Normally brake boosters have a bigger hose than map lines, that's why I do a separate tap of a bigger size for the booster.
You could probably get away with tapping 3 runners for map signal, and using one runner for the booster.

JSchlappi82 · Post by **JSchlappi82** » Thu May 11, 2006 3:23 am

I hooked up a vacuum gauge today, when engine was idling the needle was pulsating, it kept bouncing between 80 and 40 kpa. (-0,2b and -0,6 b)

When i pushed the hose together it becam stable, 80 kpa at idle (-0,2b).
With just a little throttle it was 100 kpa (0b), and at decelleration it was 40 kpa (0,6b)

That doesn't sound right, does it? No load, just a little throttle, and right 100 kpa?

Greetz, Joris

JSchlappi82 · Post by **JSchlappi82** » Thu May 11, 2006 8:41 am

Damn! I found out one cylinder isn't working as it's supposed.
I measured compression, 1, 2, and 4 were good. But cylinder 3 had 4 Bar, instead of 10....

I think i burned a valve, or the piston rings.

Thats why i don't have enough vacuum...?

Karl_Skewes · Post by **Karl_Skewes** » Thu May 11, 2006 4:11 pm

ok, putting that aside for a sec.

Try move your vacuum line to only tap 1,2 and 4. How's your map signal then?

A bad cyl (comp or manifold leak) can really mess with your vacuum signal on itb's.

JSchlappi82 · Post by **JSchlappi82** » Sat May 13, 2006 5:59 am

Damn!

I did a cilinder leakage test (?) -> An adapter goes into the hole where the spark plug was, then you put air pressure on the piston (in TDC) to see if there's a leak. (Valves, piston rings or gasket...)

On cilinder 3: 10% leak. This is acceptable.

Then i measured the compression again, all cilinders good!

Now i found out my injector for cilinder 3 isn't working at idle, but works fine while cruising!
Could this be an issue for vacuum? I found out my vacuum is about 80 kpa while cruising.

What vacuum is normal on ITB's? Should it be 0 kpa at idle, and is it normal it drops to atm. very soon?