How to make torque at higher RPM...
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
Isn't it much more fun when you figure it out for yourself?
It is to me, anyway.
FWIW, MEPs (I, B or F) are not something you measure, but something you calculate. As mentioned by a few, they relate how much torque (Indicated, Brake or Friction) is associated with each cubic inch (or cc) of displacement.
With good intake & exhaust tuning an engine (like an open Cup engine and perhaps Pro Stock) may have it's highest VE at/near power peak rpm rather than torque peak rpm. It still would most likely have a higher BMEP nearer torque peak because of increasing friction torque (and FMEP) at the very high rpm hp peak.
Keep the fires in you heads burning.
It is to me, anyway.
FWIW, MEPs (I, B or F) are not something you measure, but something you calculate. As mentioned by a few, they relate how much torque (Indicated, Brake or Friction) is associated with each cubic inch (or cc) of displacement.
With good intake & exhaust tuning an engine (like an open Cup engine and perhaps Pro Stock) may have it's highest VE at/near power peak rpm rather than torque peak rpm. It still would most likely have a higher BMEP nearer torque peak because of increasing friction torque (and FMEP) at the very high rpm hp peak.
Keep the fires in you heads burning.
TECH Resident
Joined: Dec 2004
Posts: 881
Likes: 1
Originally Posted by Old SStroker
It still would most likely have a higher BMEP nearer torque peak because of increasing friction torque (and FMEP) at the very high rpm hp peak.
I was hoping for specific engines where the peak bmep was well below peak VE. I would have thought this is more likely in engines with VEs of 105-115.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Originally Posted by DavidNJ
Unless you have variable displacement or are converting from 4-cycle to 2-cycle on the fly, bmep has a constant relationship to torque. Peak bmep always occurs at peak torque.
I was hoping for specific engines where the peak bmep was well below peak VE. I would have thought this is more likely in engines with VEs of 105-115.
I was hoping for specific engines where the peak bmep was well below peak VE. I would have thought this is more likely in engines with VEs of 105-115.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Originally Posted by DavidNJ
Peak bmep always occurs at peak torque.
TECH Resident
Joined: Dec 2004
Posts: 881
Likes: 1
Originally Posted by racer7088
Well Torque is what you actually have left at the end of the crank so it IS in fact BMEP. Just because Tq peaks at the crank doesn't mean that VE peaked at that same point. It all depends on the friction and other curves.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Originally Posted by DavidNJ
Yes, I know. However, looking at street engine maps it always appears that torque nearly exactly flows VE. I think this is just a factor of the air flow tuning and low torque and power peaks of most street engines. Points at which big, friction not linearly related to speed has reared its head. If the friction was linearly related to speed, than bmep would relate to VE.
