some tests with bad results ¡¡

[Simons]

Hi friend! As I told you by phone, I think that the problem is in the wastegate.

First when the boost are going up there aren't any problem becouse the waste is closed but when the n75 starts his duty cicle to control de boost, open the waste's valve and the exhaust gas pass across the bypass to the downpipe, and I think in this moment, some exhaust gas flow across the body and guide of the waste's valve and come into the low chamber of the waste and causes an increase of pressure on the low chamber and pull up the waste's valve.... open totally the bypass, 0,4bar with OEM spring, and the only way to close the waste is reduccing the exhaust gas(decelerate) becouse the n75 can't close due to the exhaust gas are flowing across the body's valve and making the same job that the n75 does with the pressure air from the turbo to open the waste.

one question, what is the tecnical name for the body and guide valve?? I don't remember ....

Tell us something

[prj]

Hi friend! As I told you by phone, I think that the problem is in the wastegate.

First when the boost are going up there aren't any problem becouse the waste is closed but when the n75 starts his duty cicle to control de boost, open the waste's valve and the exhaust gas pass across the bypass to the downpipe, and I think in this moment, some exhaust gas flow across the body and guide of the waste's valve and come into the low chamber of the waste and causes an increase of pressure on the low chamber and pull up the waste's valve.... open totally the bypass, 0,4bar with OEM spring, and the only way to close the waste is reduccing the exhaust gas(decelerate) becouse the n75 can't close due to the exhaust gas are flowing across the body's valve and making the same job that the n75 does with the pressure air from the turbo to open the waste.

one question, what is the tecnical name for the body and guide valve?? I don't remember ....

Tell us something

No.

[Bart76]

Did you try your multisensor? I don't know if it is the right word.

[Rocco]

hello friendssssssssssssssssssssssssssssssssssssssssssss ssssssssss


as Simons said it was the WASTEGATE

it has a lot of "play" in the piston and it loses some pressure there causing the 0.4bar "boost cut" after few seconds boosting hard....... boosting hard,but not boosting like NOW 2.0bar in 5th gear instantaneus spool up¡¡

now problem solved,hope it helps for next future boost problems in the forum members because our wastegates valves are too old and used....and many of them sure has play in the piston

take care with them friends

thanks to everyone for all the coments and helps/suggestions

[Simons]

No.

Why not??

I had a boost problem, my boost didn't keep properly, I changed the DV for a forge and a new n75...nothing changed....when I was changing the waste's membrane y saw that my low chamber was black and dust.... from the n75 the air is clean, and the valve had too much clearance....the problem was the wastegate.

[newsh]

hello friendssssssssssssssssssssssssssssssssssssssssssss ssssssssss


as Simons said it was the WASTEGATE

it has a lot of "play" in the piston and it loses some pressure there causing the 0.4bar "boost cut" after few seconds boosting hard....... boosting hard,but not boosting like NOW 2.0bar in 5th gear instantaneus spool up¡¡

now problem solved,hope it helps for next future boost problems in the forum members because our wastegates valves are too old and used....and many of them sure has play in the piston

take care with them friends

thanks to everyone for all the coments and helps/suggestions

Brilliant Rocco!

[Thuppu]

Isn't the 0,4bar boost cut controlled by the motronic and N75 when the engine is in malfunction/safe mode? OEM spring rate is 1,4-1,5bar(happens if/when the N75 to WG hose is loose or leaks).

[prj]

Isn't the 0,4bar boost cut controlled by the motronic and N75 when the engine is in malfunction/safe mode? OEM spring rate is 1,4-1,5bar(happens if/when the N75 to WG hose is loose or leaks).

Yes, it is.

Why not??

Never mind, misread some of your text yesterday, sorry.

However, it still is weird to me, that even if Simons theory is correct, the boost falls to exactly spring pressure.
It sounds like a boost cut in motronic much more than a such physical problem. Especially due to the fact that the boost falls sharply, not gradually.

[Thuppu]

If you unplug the N75 -> WG hose your boost shold rise up to the WG spring pressure that is much higher than the boost cut(0,4bar) pressure. If this doesn't work there must be a failure with the WG. But if it works there is some other problem with the engine/boost/fuel, some reason why motronic is cutting the boost to protect the engine.

[prj]

If you unplug the N75 -> WG hose your boost shold rise up to the WG spring pressure that is much higher than the boost cut(0,4bar) pressure.
If this doesn't work there must be a failure with the WG. But if it works there is some other problem with the engine/boost/fuel, some reason why motronic is cutting the boost to protect the engine.

If you unplug the N75 -> WG hose then the only thing the spring counteracts is exhaust backpressure.

[Thuppu]

Yes, of course, your right. With my setup the WG boost pressure rised up to 1,5 bar but with a another setup it can be different depending how much exhaust pressure is.

[prj]

If it only went to 1.5 bar then I think something is wrong...
I can easily go to 1.7 bar on my car with N75 attached, by just changing settings in Motronic, not disconnecting anything.

[Thuppu]

Hmm, too small hotside on the turbo? 55/AR.63. My motronic is remapped and the boost is set to 1,7 now, but I had to put a stiffer WG spring to reach the limit. WG opened to early with the stock spring, probably because high ex pressure. Have a new N75, the old one was a litle bit damaged.

[prj]

No need to change spring, better to change N75 topology, so that when N75 is ON, the upper chamber gets the same pressure as the lower chamber.

[Thuppu]

Did that need any changes in the Motronic values?