Mitchagain
08-29-2005, 02:09 PM
I have been reading all the claims about the benefit to the cold air induction to our Duramax’s. I noticed several stories about 2-3 mpg increases, so with the price of diesel climbing out the roof I figured even if there was a little increase, I ought to try it out.
4wheeln and I had time this weekend to do mods and tests to see what we could do to affect the temperature in the airbox, and not influence the air volume. The flex tubing we used was the same size as the outlet of the airbox.
Before any mods were done, we did a check on the temperature of the air in my swiss-cheese airbox. Saturday was a good day for the testing because it was hotter than hell at 111°. We inserted a Fluke digital temp probe in the box and mounted the DVM on the antenna for continual monitoring (cable was too short to have the DVM inside the cab).
After getting the truck get to operating temp of 195-200° and transmission temp to 180°, we started the data collection. (I did take the splash guard off) During the time spent at red lights the temp inside the box (TIB) was 162° but within ¾ of a mile at 45 mph the temp would drop to 123°. Next red light temp would climb to 145° within 10 seconds and increase to a max of 162-165° (depending on time spent at red light). With a 2 mile run of no red lights, lowest temp was 118°. (In all testing, rapid accelerations did not seem to show any benefit or detriment in getting the TIB to drop.)
Back in the shop we covered all the holes and the factory opening. We cut a 4” opening in the bottom of the box, and through the bottom mounting plate. We added a length of flex so that the bottom was even with the bottom of the plastic fender skirt. This put the bottom of the hose below the radiator bottom and roughly 14-16” above the pavement.
Because the holes were covered we put the temp probe inside the box at the flex tube opening and ran the wire up beside the filter (close to the plastic coolant container) and clamped the airfilter lid down gently. Because it was now Sunday morning the ambient temp was now 105-107°. After getting truck to operating temp (same as Saturday) we started the data collection. At idle at red light the temp got to 115-120° depending on the time spent at the red light. This is fully 40-45° cooler than “stock” configuration. Within ¼ mile the TIB was down to ambient temp, 105-107°. The Max TIB was 123° when we pulled over and waited for several minutes to see what the of effect pavement radiant heat. Again, within ¼ mile we were at ambient temp. All tests at 45 mph.
Back in the shop we shortened the hose to about 12” total length. This puts the bottom of the flex at a level that is roughly 6-7” above the bottom of the front edge of the fender skirt. This is also about even, or a little above, with the bottom hose connection of the radiator. We went back on the streets for the next test. Ambient temperature had increased to 111°. At the red lights the TIB was 140°. If we stopped to let the TIB increase to maximum it would top out at 149°. In less than ¼ mile the TIB was at ambient OR BELOW! In a 2 mile run at 45 mph and no red lights the TIB would drop to 1° below ambient.
Thinking that the heat increase was because of radiant heat from the radiator/CAC we installed a temporary shield that divided that area from the flex tube. No benefit from our shielding was seen. Maybe more complete shielding would be necessary for any benefit. As it stands right now, the bottom of the flex is in a position that I think is safe. It’s high enough to keep rain/water spray from being sucked up the tube, protected by the plastic fender skirting on one side and the headlights/turn signals on the front side, and metal fender wall on the outside. BTW, we did tie-wrap the bottom of the flex to the very bottom of the metal fender wall and the topside to the air box (though I cut the hole so close to size that the flex had to be “screwed” into the bottom of the box for a very tight seal.
Before all testing I replaced the air filter and the post OEM Cat filter. Today I am going over to the Chevy house to do the OEM fuel filter recall replacement. Afterwards I am going to top off the fuel tank and monitor the fuel economy. BTW, last fill was 15.1 mpg for all in town driving. Oh yea, final note, all this is after KB’s stack sealing on my LB7.
Does anyone have any engineering comments about the benefit of the cooler air into the airbox? Any formulas that take into account Temp-Humidity and combustion and or efficiency towards MPG increases/decreases? Comments?
4wheeln and I had time this weekend to do mods and tests to see what we could do to affect the temperature in the airbox, and not influence the air volume. The flex tubing we used was the same size as the outlet of the airbox.
Before any mods were done, we did a check on the temperature of the air in my swiss-cheese airbox. Saturday was a good day for the testing because it was hotter than hell at 111°. We inserted a Fluke digital temp probe in the box and mounted the DVM on the antenna for continual monitoring (cable was too short to have the DVM inside the cab).
After getting the truck get to operating temp of 195-200° and transmission temp to 180°, we started the data collection. (I did take the splash guard off) During the time spent at red lights the temp inside the box (TIB) was 162° but within ¾ of a mile at 45 mph the temp would drop to 123°. Next red light temp would climb to 145° within 10 seconds and increase to a max of 162-165° (depending on time spent at red light). With a 2 mile run of no red lights, lowest temp was 118°. (In all testing, rapid accelerations did not seem to show any benefit or detriment in getting the TIB to drop.)
Back in the shop we covered all the holes and the factory opening. We cut a 4” opening in the bottom of the box, and through the bottom mounting plate. We added a length of flex so that the bottom was even with the bottom of the plastic fender skirt. This put the bottom of the hose below the radiator bottom and roughly 14-16” above the pavement.
Because the holes were covered we put the temp probe inside the box at the flex tube opening and ran the wire up beside the filter (close to the plastic coolant container) and clamped the airfilter lid down gently. Because it was now Sunday morning the ambient temp was now 105-107°. After getting truck to operating temp (same as Saturday) we started the data collection. At idle at red light the temp got to 115-120° depending on the time spent at the red light. This is fully 40-45° cooler than “stock” configuration. Within ¼ mile the TIB was down to ambient temp, 105-107°. The Max TIB was 123° when we pulled over and waited for several minutes to see what the of effect pavement radiant heat. Again, within ¼ mile we were at ambient temp. All tests at 45 mph.
Back in the shop we shortened the hose to about 12” total length. This puts the bottom of the flex at a level that is roughly 6-7” above the bottom of the front edge of the fender skirt. This is also about even, or a little above, with the bottom hose connection of the radiator. We went back on the streets for the next test. Ambient temperature had increased to 111°. At the red lights the TIB was 140°. If we stopped to let the TIB increase to maximum it would top out at 149°. In less than ¼ mile the TIB was at ambient OR BELOW! In a 2 mile run at 45 mph and no red lights the TIB would drop to 1° below ambient.
Thinking that the heat increase was because of radiant heat from the radiator/CAC we installed a temporary shield that divided that area from the flex tube. No benefit from our shielding was seen. Maybe more complete shielding would be necessary for any benefit. As it stands right now, the bottom of the flex is in a position that I think is safe. It’s high enough to keep rain/water spray from being sucked up the tube, protected by the plastic fender skirting on one side and the headlights/turn signals on the front side, and metal fender wall on the outside. BTW, we did tie-wrap the bottom of the flex to the very bottom of the metal fender wall and the topside to the air box (though I cut the hole so close to size that the flex had to be “screwed” into the bottom of the box for a very tight seal.
Before all testing I replaced the air filter and the post OEM Cat filter. Today I am going over to the Chevy house to do the OEM fuel filter recall replacement. Afterwards I am going to top off the fuel tank and monitor the fuel economy. BTW, last fill was 15.1 mpg for all in town driving. Oh yea, final note, all this is after KB’s stack sealing on my LB7.
Does anyone have any engineering comments about the benefit of the cooler air into the airbox? Any formulas that take into account Temp-Humidity and combustion and or efficiency towards MPG increases/decreases? Comments?