JCsTruck
Well-known member
- First Name
- John
- Joined
- May 26, 2024
- Threads
- 17
- Messages
- 881
- Reaction score
- 883
- Location
- Worcester MA
- Vehicles
- 2025 Reg Cab 2WD Work Truck XL with 2.7 + 2024 Supercab XL 4x4 with 5.0 V8
- Occupation
- Project Manager, formerly Construction Superintendent, formerly ASE A1-A8 Tech.
Supercharged or modified turbocharged engines are a different story altogether and when you increase the pumping ability (volumetric efficiency above 100%) of the engine then yes a stock intake is going to become restrictive.
On an unmodified naturally aspirated engine it has been my experience that many aftermarket intakes don't improve power in a usable RPM range over the stock intake. Often times they hurt low end torque in lieu of some top end horsepower gains. Same thing happens with an exhaust system when you go with larger diameter pipe or two pipes vs one. In years past anyway this is why those manufacturers of these intake systems displayed truncated power graphs because they didn't want the customer to see the low end loss.
I installed a K&N filter on my Tundra while it was on the dynojet dynamometer and it lost a little bit of power. To find out why I flattened out the K&N filter and compared it to a flattened stock Toyota filter and the stock Toyota filter had twice the surface area compared to the K&N filter. The Toyota filter had more pleated area or folds packed into the same square. The net result was even though the K&N filter could flow more air per a square inch, the stock Toyota filter flowed more overall because it had twice the surface area or media (more folded pleates) so it flowed more overall. The stock Toyota filter also arguably did a better job protecting the engine from harmful dirt particles too.
Now the bigger is better mentality always gets people in this business. Intake pipes and exhaust pipes are sized to produce the best air or exhaust gas velocity for a given RPM which is always a compromise between scavenging (or ram air) at low RPM vs high rpm. Because those things are fixed in size you cannot have both, although variable valve timing, and on some engines like my Kia Telluride the manufacturer also employs variable intake runners which mitigates those compromises.
Because an engine is an air pump that has 4 strokes and a power cycle every 90-degrees (8cyl) or 120 degrees (6-cyl) you get intake air speeds, and especially exhaust gas velocity that speeds up and slows down in between every firing cycle. If the pipe gets too big then you get air or exhaust gas that slows down too much at lower RPM and you lose low end torque as a result. In an all out pedal to the floor (WOT) race it doesn't matter as much but in everyday driving you may find yourself needing to dip into that throttle more than before to get your 5000 lb truck moving the same as before and it will make more noise while doing it too.
On an unmodified naturally aspirated engine it has been my experience that many aftermarket intakes don't improve power in a usable RPM range over the stock intake. Often times they hurt low end torque in lieu of some top end horsepower gains. Same thing happens with an exhaust system when you go with larger diameter pipe or two pipes vs one. In years past anyway this is why those manufacturers of these intake systems displayed truncated power graphs because they didn't want the customer to see the low end loss.
I installed a K&N filter on my Tundra while it was on the dynojet dynamometer and it lost a little bit of power. To find out why I flattened out the K&N filter and compared it to a flattened stock Toyota filter and the stock Toyota filter had twice the surface area compared to the K&N filter. The Toyota filter had more pleated area or folds packed into the same square. The net result was even though the K&N filter could flow more air per a square inch, the stock Toyota filter flowed more overall because it had twice the surface area or media (more folded pleates) so it flowed more overall. The stock Toyota filter also arguably did a better job protecting the engine from harmful dirt particles too.
Now the bigger is better mentality always gets people in this business. Intake pipes and exhaust pipes are sized to produce the best air or exhaust gas velocity for a given RPM which is always a compromise between scavenging (or ram air) at low RPM vs high rpm. Because those things are fixed in size you cannot have both, although variable valve timing, and on some engines like my Kia Telluride the manufacturer also employs variable intake runners which mitigates those compromises.
Because an engine is an air pump that has 4 strokes and a power cycle every 90-degrees (8cyl) or 120 degrees (6-cyl) you get intake air speeds, and especially exhaust gas velocity that speeds up and slows down in between every firing cycle. If the pipe gets too big then you get air or exhaust gas that slows down too much at lower RPM and you lose low end torque as a result. In an all out pedal to the floor (WOT) race it doesn't matter as much but in everyday driving you may find yourself needing to dip into that throttle more than before to get your 5000 lb truck moving the same as before and it will make more noise while doing it too.
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