I have this problem where my evo's peak boost is much lower at end of a track day or rally then at the beginning. We tuned the car to 32 psi peak in 5th gear where after driving some time on the track the car only boosts to about 26 psi peak. It is not connected to any compensation tables in the ECU that would lower the WG DC% under higher engine temp. The engine temp is not too high anyway. Also IAT is not a problem because the IAT table in the ecu is now set in a way it won't change the WG DC. I think the problem might be the 3 port grimmspeed controller that I am using. The controller is mounted close to the radiator and it gets really hot after some time on the track. Maybe the boost changes because even the WG DC% are the same the 3 port controller works differently when it's cold and when it's hot. What do you guys think? I have two engines, couple of turbos and there is the same effect on any engine-turbo configuration so the problem I think is not related to the engine or the turbo itself. Did any of you have a similar problem to mine?

 

Most likely heat soak.

 

heat soak.
what kind of ic do you have?

 

I have a brand new ams ic so I really don't think it's heat soak.

 

what turbo?

 

right now I have a stock evo 9 turbo installed with the stock actuator. But I had the same problem with the forge actuator and also same problem on a EF3 turbo with the turbosmart actuator. I use the Tial DV now but I had the same problem on the stock metal DV.

 

32 psi peak on stock turbo? As good as the IC may be, running the turbo that far out of it's efficiency range is likely to still cause heatsoak.

 

Regardless if you duty cycles arent changing you simply cannot overcome simple chemistry. The hotter the air the less dense it is.

 

The engine makes more torque with 32 psi then 28 psi so I don't think it's really that important that the turbo is technically out of it's efficiency range :-) I had the same problem running 28 peak. After some time peak boost droped to 24 psi. I also had this problem running the EF3 turbo with 26 peak.

 

that is true but I don't think that's my problem. My intake air temps are not that much different when the car makes 32 psi peak to when the peak boost drops to 26 psi. I have a Vipec ecu and an IAT sensor right before the manifold so I can see what the IAT is exactly.

 

+1

 

I finally fixed the problem. The problem was either the 3 port boost solenoid itself or the placement under the hood just like I thought. I had it mounted close to the radiator and after some time on track the 3 port was getting crazy hot. Everybody was telling me that this can't effect the valves performance so I just ignored it. But now I think heat must have changed how fast the valve worked thus lowering the boost. I now have a new MAC solenoid and it's mounted in a different location where it doesn't catch any heat from the engine. The car works fine now and holds same boost during the whole day on the track. It's said that the MAC valves can withstand a lot of heat but apparently not all the heat that it might be exposed to under the evo's hood.