Cog belts?
Senior Member
Joined: Mar 2001
Posts: 830
Likes: 0
From: Plymouth, MI
Sal posted about this a while back here: https://www.f150online.com/forums/sh...ogs#post440421
Quote:
Cog belts are not used on the street for a reason. You can cause severe damage with cogs. It's ok to drive a cog car once a week around town, but even then it's suseptable to damage.
When you are doing 5000rpm and you take your foot off the gas, two things happen. One, the throttle closes, and two the by pass opens. The by pass opens to relieve the pressure from a blower that's still turning high rpms. If the by pass happens to fail, you are no longer venting boost and the pressure backs up in the motor and tries to rip everything apart. I have seen cogged Vortechs get thier impeller blades ripped right off on hard decel with a failed by pass.
Street driven blower cars use serpentine drive belts because in the case of a failed by pass, the blower tries to lock up and the belt slips instead of the blower destroying itself. If you put cogs on the Lightning, and the by pass fails, there is no doubt the pressure backup would flex the rotors to where they contact each other and the case. That would not be good.
__________________________________________________ ______________
"...the pressure backs up in the motor..."
HOW? There is nothing going on past the blower to make the pressure "back up". The throttle has closed but that's before the blower. Unless the valves have stopped opening, the pressure is going to blow that air right into the cylinders, same as if the throttle were wide open.
The throttle closing with bypass closed means that the pressure difference between the inlet and outlet of the blower stays higher than if the bypass were open, thus the load on the blower is slightly higher BUT with the throttle closed, you've got a large vacuum at the blower inlet and you aren't going to be making any boost.
Quote:
Cog belts are not used on the street for a reason. You can cause severe damage with cogs. It's ok to drive a cog car once a week around town, but even then it's suseptable to damage.
When you are doing 5000rpm and you take your foot off the gas, two things happen. One, the throttle closes, and two the by pass opens. The by pass opens to relieve the pressure from a blower that's still turning high rpms. If the by pass happens to fail, you are no longer venting boost and the pressure backs up in the motor and tries to rip everything apart. I have seen cogged Vortechs get thier impeller blades ripped right off on hard decel with a failed by pass.
Street driven blower cars use serpentine drive belts because in the case of a failed by pass, the blower tries to lock up and the belt slips instead of the blower destroying itself. If you put cogs on the Lightning, and the by pass fails, there is no doubt the pressure backup would flex the rotors to where they contact each other and the case. That would not be good.
__________________________________________________ ______________
"...the pressure backs up in the motor..."
HOW? There is nothing going on past the blower to make the pressure "back up". The throttle has closed but that's before the blower. Unless the valves have stopped opening, the pressure is going to blow that air right into the cylinders, same as if the throttle were wide open.The throttle closing with bypass closed means that the pressure difference between the inlet and outlet of the blower stays higher than if the bypass were open, thus the load on the blower is slightly higher BUT with the throttle closed, you've got a large vacuum at the blower inlet and you aren't going to be making any boost.
Senior Member
Joined: Aug 1999
Posts: 5,438
Likes: 1
From: Palm Coast, FL
Originally Posted by lurker
Sal posted about this a while back here: https://www.f150online.com/forums/sh...ogs#post440421
Quote:
Cog belts are not used on the street for a reason. You can cause severe damage with cogs. It's ok to drive a cog car once a week around town, but even then it's suseptable to damage.
When you are doing 5000rpm and you take your foot off the gas, two things happen. One, the throttle closes, and two the by pass opens. The by pass opens to relieve the pressure from a blower that's still turning high rpms. If the by pass happens to fail, you are no longer venting boost and the pressure backs up in the motor and tries to rip everything apart. I have seen cogged Vortechs get thier impeller blades ripped right off on hard decel with a failed by pass.
Street driven blower cars use serpentine drive belts because in the case of a failed by pass, the blower tries to lock up and the belt slips instead of the blower destroying itself. If you put cogs on the Lightning, and the by pass fails, there is no doubt the pressure backup would flex the rotors to where they contact each other and the case. That would not be good.
__________________________________________________ ______________
"...the pressure backs up in the motor..." HOW? There is nothing going on past the blower to make the pressure "back up". The throttle has closed but that's before the blower. Unless the valves have stopped opening, the pressure is going to blow that air right into the cylinders, same as if the throttle were wide open.
The throttle closing with bypass closed means that the pressure difference between the inlet and outlet of the blower stays higher than if the bypass were open, thus the load on the blower is slightly higher BUT with the throttle closed, you've got a large vacuum at the blower inlet and you aren't going to be making any boost.
Quote:
Cog belts are not used on the street for a reason. You can cause severe damage with cogs. It's ok to drive a cog car once a week around town, but even then it's suseptable to damage.
When you are doing 5000rpm and you take your foot off the gas, two things happen. One, the throttle closes, and two the by pass opens. The by pass opens to relieve the pressure from a blower that's still turning high rpms. If the by pass happens to fail, you are no longer venting boost and the pressure backs up in the motor and tries to rip everything apart. I have seen cogged Vortechs get thier impeller blades ripped right off on hard decel with a failed by pass.
Street driven blower cars use serpentine drive belts because in the case of a failed by pass, the blower tries to lock up and the belt slips instead of the blower destroying itself. If you put cogs on the Lightning, and the by pass fails, there is no doubt the pressure backup would flex the rotors to where they contact each other and the case. That would not be good.
__________________________________________________ ______________
"...the pressure backs up in the motor..."
HOW? There is nothing going on past the blower to make the pressure "back up". The throttle has closed but that's before the blower. Unless the valves have stopped opening, the pressure is going to blow that air right into the cylinders, same as if the throttle were wide open.The throttle closing with bypass closed means that the pressure difference between the inlet and outlet of the blower stays higher than if the bypass were open, thus the load on the blower is slightly higher BUT with the throttle closed, you've got a large vacuum at the blower inlet and you aren't going to be making any boost.
Senior Member
Joined: Apr 2003
Posts: 331
Likes: 0
Originally Posted by LightningTuner
You are correct. When I wrote that, I was thinking centrifugal type blowers, because that's a big concern with cogs. But with our setup, the TB is before the blower, so there is nothing for the boost to slam against on hard decel.
Senior Member
Joined: Sep 2002
Posts: 1,189
Likes: 0
From: HOMELESS
Originally Posted by Jubelands
So is it a YAY or NAY to cogs??