FellowTraveler
Well-Known Member
AIR FILTER CFM minimum requirements for the 6.5td at various RPM’s and VE values @ WOT only.
If your diesel falls flat at WOT or while towing or loaded even with a tune consider the air filter is limiting the ability to flow required CFM and/or air-charge density needs to be increased.
The IDI diesel engine is an air-pump that is fuel throttle controlled and as the RPM raises so does the amount of CFM that is pumped through it the numbers are variable with RPM & VE with the air-charge-density being most critical part of the equation.
As always air density plays the greatest role in your total performance/economy results. The colder the intake air-charge the more oxygen is squeezed into a cubic foot of air and any additional fuel can burn more efficiently “remember a diesel is fuel throttled” so any increase in air-charge density along with additional fuel increases HP/TQ output and require less over all pedal input during normal driving conditions. Keep in mind while loaded/towing on an upgrade at WOT the more air density you have available the less-the-heat-load there is on the cooling system, engine oil and transmission fluid.
Any air flow modifications along with other mods that increase the VE of your specific build is a good thing minus any air flow loss in CAC/IC plumbing and any pressure drop across charge-air-cooler (aka incorrectly: intercooler).
Larger sized turbocharger compressor increases air flow @ lower boost levels with less heating of the air-charge and should be properly plumbed through a quality charge-air-cooler, air to water cooler or 1k psi water injection (higher psi the more atomization) directly injected or spray the outside of charge-air-cooler under load for best results.
“An open air filter should be avoided at all costs because it reduces air density big time by pulling hot under hood/bonnet air into turbo compressor where it is heated more, then consider a small stock turbocharger @ high boost super heating the air-charge at WOT too.” Proper sizing of turbine housing is critical as it affects drive/back pressure.
The following chart I made from various RPM’s from 3.0k to 4.0k and VE values from 1.5 VE to 3.0 VE with decent mods and properly sized CAC/IC @ WOT. As RPM’s increase so does the CFM depending on a diesels volumetric efficiency (VE).
The 400 CID 4 stroke 6.5 turbo diesels average CFM flow at various VE values & WOT. However, keep in mind under normal driving conditions not loaded/towing at lower RPM the cfm flow requirement is much less and a stock or mild aftermarket air filter is OK. “The denser the air-charge is the better.”
@ 3.0k RPM & 1.5 VE flows 521 CFM, @ 2.0 VE flows 694 CFM, @ 2.5 VE flows 868 CFM, and @ 3.0 VE flows 1042 cfm
@ 3.5k RPM & 1.5 VE flows 608 CFM, @ 2.0 VE flows 810 CFM, @ 2.5 VE flows 1013 CFM, and @ 3.0 VE flows 1215 cfm
@ 4.0k RPM & 1.5 VE flows 694 CFM, @ 2.0 VE flows 926 CFM, @ 2.5 VE flows 1157 CFM, and @ 3.0 VE flows 1389 CFM.
In conclusion a single or dual and properly sized for WOT air-filter (s) and canister (s) are required to get most out of the 6.5td @ WOT as is a quality charge-air-cooler (aka: improperly called intercooler) water to air cooler or high pressure 1k psi water injection is required to increase air-charge density.
Avoid any adapter in your intake air-filter to turbo compressor runner that makes your smaller runner match up to a larger turbo compressor inlet as it chokes the flow at WOT. The runner should match or be slightly larger in diameter than the turbo compressor inlet.
A larger air-filter will increase time between PM cleaning, replacing filter elements.
If your diesel falls flat at WOT or while towing or loaded even with a tune consider the air filter is limiting the ability to flow required CFM and/or air-charge density needs to be increased.
The IDI diesel engine is an air-pump that is fuel throttle controlled and as the RPM raises so does the amount of CFM that is pumped through it the numbers are variable with RPM & VE with the air-charge-density being most critical part of the equation.
As always air density plays the greatest role in your total performance/economy results. The colder the intake air-charge the more oxygen is squeezed into a cubic foot of air and any additional fuel can burn more efficiently “remember a diesel is fuel throttled” so any increase in air-charge density along with additional fuel increases HP/TQ output and require less over all pedal input during normal driving conditions. Keep in mind while loaded/towing on an upgrade at WOT the more air density you have available the less-the-heat-load there is on the cooling system, engine oil and transmission fluid.
Any air flow modifications along with other mods that increase the VE of your specific build is a good thing minus any air flow loss in CAC/IC plumbing and any pressure drop across charge-air-cooler (aka incorrectly: intercooler).
Larger sized turbocharger compressor increases air flow @ lower boost levels with less heating of the air-charge and should be properly plumbed through a quality charge-air-cooler, air to water cooler or 1k psi water injection (higher psi the more atomization) directly injected or spray the outside of charge-air-cooler under load for best results.
“An open air filter should be avoided at all costs because it reduces air density big time by pulling hot under hood/bonnet air into turbo compressor where it is heated more, then consider a small stock turbocharger @ high boost super heating the air-charge at WOT too.” Proper sizing of turbine housing is critical as it affects drive/back pressure.
The following chart I made from various RPM’s from 3.0k to 4.0k and VE values from 1.5 VE to 3.0 VE with decent mods and properly sized CAC/IC @ WOT. As RPM’s increase so does the CFM depending on a diesels volumetric efficiency (VE).
The 400 CID 4 stroke 6.5 turbo diesels average CFM flow at various VE values & WOT. However, keep in mind under normal driving conditions not loaded/towing at lower RPM the cfm flow requirement is much less and a stock or mild aftermarket air filter is OK. “The denser the air-charge is the better.”
@ 3.0k RPM & 1.5 VE flows 521 CFM, @ 2.0 VE flows 694 CFM, @ 2.5 VE flows 868 CFM, and @ 3.0 VE flows 1042 cfm
@ 3.5k RPM & 1.5 VE flows 608 CFM, @ 2.0 VE flows 810 CFM, @ 2.5 VE flows 1013 CFM, and @ 3.0 VE flows 1215 cfm
@ 4.0k RPM & 1.5 VE flows 694 CFM, @ 2.0 VE flows 926 CFM, @ 2.5 VE flows 1157 CFM, and @ 3.0 VE flows 1389 CFM.
In conclusion a single or dual and properly sized for WOT air-filter (s) and canister (s) are required to get most out of the 6.5td @ WOT as is a quality charge-air-cooler (aka: improperly called intercooler) water to air cooler or high pressure 1k psi water injection is required to increase air-charge density.
Avoid any adapter in your intake air-filter to turbo compressor runner that makes your smaller runner match up to a larger turbo compressor inlet as it chokes the flow at WOT. The runner should match or be slightly larger in diameter than the turbo compressor inlet.
A larger air-filter will increase time between PM cleaning, replacing filter elements.
