I'm running ITB's and I need a better MAP signal...vacuum is so low......what do I do?
I'm running a small sized log canister. The signal is so weak. Would a bigger sized canister improve the signal?
Should I tap more lines into the ports and connect those to the canister?

I am also using a SAFC II

thanks....

 

i would tap a line from each cyl. into the canister

 

It's already setup that way.

 

get some thing that has the abillity to tune those things...... you are NEVER going to get a good map signal from itb's, its just the way they are.

if you have the time to mess with it uberdata can be made to run itb's, or get a standalone that can blend the map/tps signals.

 

as i see it, the reason you can't get enuf total vacuum with itb's at idle is because the canister you are getting the map signal from is losing overall vacuum when the intake valves are closed.

in other words, if you measure just one itb port with a vacuum gauge at idle, with nothing else plugged into the port, you should see the gauge jump wildly, because of the intake valve movement... every time the valve closes, the port loses a bunch of vacuum because of it's small volume, so when it loses vacuum, it would be bleeding air into the common canister that you are using to measure the map signal with... hope that makes sense.

just for drill, it would be interesting to see if there is any effect on the overall map signal amplitude when you do things like plug the the power brake vacuum line that comes from the vacuum canister.

i *think* that an alpha-n efi system uses just the tps for load sensing, while a speed density efi system primarily uses the map signal, plus a little tps... megasquirt will allow you to use only alpha-n mode at idle and low rpm, then transition into speed density mode whenever you program it to do so, probably based on the map signal... which is what jdogg was referring to.

 

but what if you were able to use a seperate check valve to block off each itb port that wasn't pulling full vacuum from the canister, when it's intake valve was closed:

• Maximum Vacuum: 30" Hg
• Maximum Temperature: 176° F
These check valves are used in vacuum lines, relying on back pressure for instant operation in any position. The tapered ends easily connect to soft tubing (arrows on the valve indicate direction of free flow). Valves have a polyethylene body and neoprene disc. Color is white.
Note: Valves are not rated for Cv factor or cracking pressure.
Connections: Barbed.

part #4610K13, $4.23 each, http://www.mcmaster.com/

i wonder how long they'd last? hopefully the valve guts wouldn't get sucked into your itb port when they came apart, lol!

 

you dont need all that...... running all 4 into a common vac manifold works

i have done it with normal speed density, but its not easy and takes some time.

alpha-n dosnt work that well if you dont have any map input at all. its hard to keep the afr at idle good when something changes the load on the engine... ie rad fan, a/c, etc.

the best way to do it is to have a throttle based fuel map with a correction for map.. keep the ign map Speed density... ignition is a bit easier to do that fuel with itb's.

 

Uberdata map scalar.

But first take some actual vac readings with a vac gauge at idle, partial driving at different loads, wot, etc etc. Then build your custom columns in uberdata based on that.

 

i'm using ITB and converted to alpha N.. and just turn up the idle.. don't expect the motor to idle smooth at 800 or like stock.. DFI GEN VII.. good luck