need tuning help

[msheller]

Ever since I converted to pte 52 kit, 50#er's, 3 bar, 2nd fuel pump, PL chip I've had a part throttle undulation or flutter. Runs great off boost and w/ application of heavy throttle...but wants to undulate or flutter if I use part throttle or if I use heavy throttle and then let off a bit.
What do u guyhs think it could be?
Matt

 

[Bill Z]

Re: need tuning help

My opinion here. I had the same problem with my 3Bar set up using stock injectors.

The 3bar MAP has to measure 3 atmospheric pressures in the same space that the 2bar does. The voltage in each amount of vacuum/boost appears to the ECM more coarse (each voltage change means more vacuum/boost than the 2bar). If for any reason there is a fluctuation in vacuum/boost, it becomes more dominate in a 3bar system. Keep in mind that air has mass. Sometimes with this mass changes direction suddenly there are ever so small ripples that are eventually measured by the MAP sensor. The longer and larger your vacuum lines, the more this phenomenon will affect performance.

A suggestion that may help to reduce this affect is to make sure the line to the MAP sensor has nothing else on it (no 'T's) and the line is the factory size line (small rigid plastic).

My 2 cents worth.

Good luck.

 

[msheller]

Re: need tuning help

My opinion here. I had the same problem with my 3Bar set up using stock injectors.

The 3bar MAP has to measure 3 atmospheric pressures in the same space that the 2bar does. The voltage in each amount of vacuum/boost appears to the ECM more coarse (each voltage change means more vacuum/boost than the 2bar). If for any reason there is a fluctuation in vacuum/boost, it becomes more dominate in a 3bar system. Keep in mind that air has mass. Sometimes with this mass changes direction suddenly there are ever so small ripples that are eventually measured by the MAP sensor. The longer and larger your vacuum lines, the more this phenomenon will affect performance.

A suggestion that may help to reduce this affect is to make sure the line to the MAP sensor has nothing else on it (no 'T's) and the line is the factory size line (small rigid plastic).

My 2 cents worth.

Good luck.

thanx 4 the reply!

Matt