boost a bit like a yoyo...

[Olivier]

Hello,
Got few little mod on the car and I am wondering if the waste gate is acting properlly. I did the mods before the boost gauge, then I don't know if its a normal acting or if its due to too many tinkerig...
What is happening is the boost goes up to 22 PSI,then the wastegate open lowering the boos to 15PSI and then re-ajust itself and goes to 18/ 19 PSI. I think the ECU get a fright and fully open the gate?
This mean the car pull hard, has a little less pull when the gate open, then keep pulling when the gate adjust itself. Sometimes the boost goes a little up and down too between 15 and 20.
Is that normal behaviour or should I have a constant going up boost in a nice up curve?
Thanks.
Olivier

[ngarover]

Don't have a specific answer, but I can tell you my 85 300CD's KKK turbo is turned up and runs the curve steady and smooth to max (about 20) if under full throttle. And will hold it as long as full throttle is held. releasing the throttle opens the waste-gate (you can actually hear it dump) and the boost will drop down to it hi-way boost of around 12 at 65 and be steady. So, in other words, mine does not yoyo.

Doesn't show the boost, but give you an idea of how it runs.

300CD 3 seperate spped tests the day after replacing engine mounts. - YouTube

[Olivier]

Cheers.
Mine is different, after awhile and when the rev goes highter the boost get lower.
I was looking at the boost when I take the foot off the accelerator and at 70mph no acceleration there is a boost of about 2 1/2 PSI. ( not 5 like I thought, sorry)
Perhaps I need to open the wastegate a little more, it might not open totally or not fast enough, then this could be the reason why the ECU is freaking out?
This mean another time under the beast, taking the underbelly off and play with the acuator
Oh well...
Thank you again Ngarover, I will try to achieve a proper curve
To be continued.
Olivier

[ngarover]

Originally Posted by Olivier

Cheers.
Mine is different, after awhile and when the rev goes highter the boost get lower.
I was looking at the boost when I take the foot off the accelerator and at 70mph no acceleration there is a boost of about 5PSI.
Perhaps I need to open the wastegate a little more, it might not open totally or not fast enough, then this could be the reason why the ECU is freaking out?
This mean another time under the beast, taking the underbelly off and play with the acuator
Oh well...
Thank you again Ngarover, I will try to achieve a proper curve
To be continued.
Olivier

Hmmm, at 70 when I take my foot out of the peddle, my boost is 0. When I hold a steady 70 my boost is a rock solid 8. IF I down shift and punch it, it jumps to to around 18. ( my kickdown does not work so I have to down shift)

[Olivier]

Cheers, I just double check, I got 2 to 3 psi at 70... Not 5 Psi as I thought.
I was doing this through memory and I thought the needle was in between 0 and 10 but it was between 0 and 5... sorry for the booboo. Still its some boost while there is no foot on the pedal...