Blow Off Valve Question
Thread Starter
Intermediate
Joined: Apr 2016
Posts: 31
Likes: 10
From: Tecumseh
Blow Off Valve Question
I have a question about a suspect bad blow off valve. Its a quiet version, If is bad will the car run normal, and just not have the power from the ECS supercharger? It seems like i can hear it blowing off at about 1/4 throttle and i can feel the cars power change. It was all on the car when i bought it a few months ago. Car runs good, but certainly isnt the typical 550-600 hp it should be with the ECS. Thanks.
Le Mans Master
Joined: Oct 2014
Posts: 8,674
Likes: 2,728
From: Atlanta GA
It is supposed to blow off at 1/4 throttle unless you have your foot planted to the floor , If you are just making a fast run up to redline you might still have a vacuum signal if your foot is not on the floor .
The operation is simple , as long as you have a vacuum signal the valve will be open to a varying degree depending on how much vacuum you have . As soon as you go zero vacuum or into a boost condition ( pedal is to the floor ) valve will close
A simple cheap vacuum tester will tell you if the blow off valve is working ( see link below ). Pull a vacuum with it and see if it holds , test the other lines and make sure your check valve is working and inserted the correct direction . If all tests are good , You might have to remove the valve and physical look at it to make sure butterfly is sealing
Another test is , check for air leaks in your plumbing , buy two plastic pvc pipe caps same size as the inside diameter of your rubber hoses , remove the hose on throttle body, insert the cap and screw clamp down tightly. Take second cap and drill a hole in center and insert a air hose adapter. Then put this in the hose that comes from your air filter to your supercharger, screw it down tightly. You will need an air preasure guage in your compressor hose, connect air supply to pipe cap and carefully pump the system to 5 pounds ( no more than that !!!) and spray all your connections with soapy water , you will see air bubbles If you have a leak ....
Have you checked your belt tension ?
If everything checks out , its time to log your car with HP tuner and see what the ECM sees for boost , or you could buy a cheap boost guage. You could have belt slip causing your power loss
Feel free to PM me if you have any questions
Dave
https://www.harborfreight.com/brake-...hoClXkQAvD_BwE
The operation is simple , as long as you have a vacuum signal the valve will be open to a varying degree depending on how much vacuum you have . As soon as you go zero vacuum or into a boost condition ( pedal is to the floor ) valve will close
A simple cheap vacuum tester will tell you if the blow off valve is working ( see link below ). Pull a vacuum with it and see if it holds , test the other lines and make sure your check valve is working and inserted the correct direction . If all tests are good , You might have to remove the valve and physical look at it to make sure butterfly is sealing
Another test is , check for air leaks in your plumbing , buy two plastic pvc pipe caps same size as the inside diameter of your rubber hoses , remove the hose on throttle body, insert the cap and screw clamp down tightly. Take second cap and drill a hole in center and insert a air hose adapter. Then put this in the hose that comes from your air filter to your supercharger, screw it down tightly. You will need an air preasure guage in your compressor hose, connect air supply to pipe cap and carefully pump the system to 5 pounds ( no more than that !!!) and spray all your connections with soapy water , you will see air bubbles If you have a leak ....
Have you checked your belt tension ?
If everything checks out , its time to log your car with HP tuner and see what the ECM sees for boost , or you could buy a cheap boost guage. You could have belt slip causing your power loss
Feel free to PM me if you have any questions
Dave
https://www.harborfreight.com/brake-...hoClXkQAvD_BwE
Last edited by Dcasole; Jun 22, 2024 at 11:28 AM.
Thread Starter
Intermediate
Joined: Apr 2016
Posts: 31
Likes: 10
From: Tecumseh
Thank you. I do have a mighty vac i will do some checking with. I also have an appt with a tuner in mid july so Im sure we can get it figured out then. Thanks again for the explanation.
