CAI’s...do they actually work?

[Belgian1979]

I would think that a CAI would produce more than that, so it's well worth it.

[MadBill]

Depending on the vehicle, it could take as little as 20 HP to propel it on level ground at 50 MPH, so 1 HP would be a 5% change.

[Belgian1979]

When driving at that speed (close to 3000 rpm) I'm seeing my engine produce around 60-65 HP. 20 HP might be if you have a very (!) light vehicle. 1 HP on 60 HP = 1.6%

As far as fuel injected vs the air temp and looking into my efi mat tables I see that the difference between 113°F and 68°F is roughly 8%. This would mean that 8% more fuel needs to be injected. Assuming an efficiency of only 30% (low ball) you would still have 2,66% net hp increase. Not a lot but still favorable.
However on acceleration and WOT this would become far more and favorable.

This all is not taking into account that when driving on 113°F air temp you would be closer to detonation with the same CR. So if you want to drive with hot air you would also need to reduce your timing and that would reduce your HP even more.

[groberts101]

When driving at that speed (close to 3000 rpm) I'm seeing my engine produce around 60-65 HP. 20 HP might be if you have a very (!) light vehicle. 1 HP on 60 HP = 1.6%

As far as fuel injected vs the air temp and looking into my efi mat tables I see that the difference between 113°F and 68°F is roughly 8%. This would mean that 8% more fuel needs to be injected. Assuming an efficiency of only 30% (low ball) you would still have 2,66% net hp increase. Not a lot but still favorable.
However on acceleration and WOT this would become far more and favorable.

This all is not taking into account that when driving on 113°F air temp you would be closer to detonation with the same CR. So if you want to drive with hot air you would also need to reduce your timing and that would reduce your HP even more.

I agree. I tried most every trick in the book for my Vortec motored work vans and completely isolating the entire induction system with a foil faced/felt backed blanket(composite intake manifold top as well).. tune could be pushed harder and mileage always improved by about .5 - 1 mpg average. Could drive for hours.. pop the hood and the plastic tubing was still cool to the touch. Less throttle required to move those round edged bricks down the highway helped every single time. Paper physics is fun, thinner hotter air.. less ignition timing.. lower pumping losses.. but in the end creating the most cylinder pressure with the least amount of throttle/fuel input is key. Lean burn can be pushed harder. Larger tubed low restriction cool air intake systems are just another building block to get there is all.

[BobbyB]

Belgian,

When you say...

"When driving at that speed (close to 3000 rpm) I'm seeing my engine produce around 60-65 HP. 20 HP might be if you have a very (!) light vehicle. 1 HP on 60 HP = 1.6%"

You are getting about 10 miles per gallon of gas at 60 miles per hour, is that correct?

My understanding is that to increase fuel economy, we need hot intake air because of MadBills explanation. Modern computer controlled cars can adjust the timing to avoid spark knock with the higher intake temps.

I have played with manipulating the intake temp ( just a little bit) on my 1983 Ranger 2.8V6 4 speed 4x4 by using a hand operated vacuum pump to operate the heat stove to the air cleaner from inside the cab. I found that power was way down at highway speeds with high intake temps in the winter. (If I recall correctly, I saw temps in the 150 Degree F range at 65 mph with outside air temp around 30 degree F). Drivability was not too good in stop & go driving. What I definitely noticed was that the throttle had to be opened more at 65 mph. My understanding is to improve economy we must open the throttle more to reduce pumping losses. Lower numerical axle ratios and overdrive transmissions are probably the most direct route to opening the throttle at cruise, but not necessarily cost effective.

I bought a 4 thermocouple sensor and measured the temps at thermostat housing, engine bay, factory cold air intake, and just above the carburetor. Probably the most interesting thing I discovered is that the thermostat housing temperature varies almost instantly with power output... I.E. open the throttle 10% to climb a hill on the intestate & watch the water temp increase 10 dergrees (approx.)

[travis]

When driving at that speed (close to 3000 rpm) I'm seeing my engine produce around 60-65 HP. 20 HP might be if you have a very (!) light vehicle. 1 HP on 60 HP = 1.6%

As far as fuel injected vs the air temp and looking into my efi mat tables I see that the difference between 113°F and 68°F is roughly 8%. This would mean that 8% more fuel needs to be injected. Assuming an efficiency of only 30% (low ball) you would still have 2,66% net hp increase. Not a lot but still favorable.
However on acceleration and WOT this would become far more and favorable.

This all is not taking into account that when driving on 113°F air temp you would be closer to detonation with the same CR. So if you want to drive with hot air you would also need to reduce your timing and that would reduce your HP even more.

I agree. I tried most every trick in the book for my Vortec motored work vans and completely isolating the entire induction system with a foil faced/felt backed blanket(composite intake manifold top as well).. tune could be pushed harder and mileage always improved by about .5 - 1 mpg average. Could drive for hours.. pop the hood and the plastic tubing was still cool to the touch. Less throttle required to move those round edged bricks down the highway helped every single time. Paper physics is fun, thinner hotter air.. less ignition timing.. lower pumping losses.. but in the end creating the most cylinder pressure with the least amount of throttle/fuel input is key. Lean burn can be pushed harder. Larger tubed low restriction cool air intake systems are just another building block to get there is all.

This has always been my experience with carbed applications...colder engine and air temps, more aggressive tune, better mileage. I’ve never messed with this stuff on an FI application all that much before now.

This makes me wonder about the coolant temps too. This suburban always runs in the 200-208* range once warmed up...whether it is 60 or 110* outside. I’m wondering if replacing the 205* thermostat for a 165 or 180 might be worth something.

More experimenting to do I guess...

[Belgian1979]

When driving at that speed (close to 3000 rpm) I'm seeing my engine produce around 60-65 HP. 20 HP might be if you have a very (!) light vehicle. 1 HP on 60 HP = 1.6%

As far as fuel injected vs the air temp and looking into my efi mat tables I see that the difference between 113°F and 68°F is roughly 8%. This would mean that 8% more fuel needs to be injected. Assuming an efficiency of only 30% (low ball) you would still have 2,66% net hp increase. Not a lot but still favorable.
However on acceleration and WOT this would become far more and favorable.

This all is not taking into account that when driving on 113°F air temp you would be closer to detonation with the same CR. So if you want to drive with hot air you would also need to reduce your timing and that would reduce your HP even more.

I agree. I tried most every trick in the book for my Vortec motored work vans and completely isolating the entire induction system with a foil faced/felt backed blanket(composite intake manifold top as well).. tune could be pushed harder and mileage always improved by about .5 - 1 mpg average. Could drive for hours.. pop the hood and the plastic tubing was still cool to the touch. Less throttle required to move those round edged bricks down the highway helped every single time. Paper physics is fun, thinner hotter air.. less ignition timing.. lower pumping losses.. but in the end creating the most cylinder pressure with the least amount of throttle/fuel input is key. Lean burn can be pushed harder. Larger tubed low restriction cool air intake systems are just another building block to get there is all.

This has always been my experience with carbed applications...colder engine and air temps, more aggressive tune, better mileage. I’ve never messed with this stuff on an FI application all that much before now.

This makes me wonder about the coolant temps too. This suburban always runs in the 200-208* range once warmed up...whether it is 60 or 110* outside. I’m wondering if replacing the 205* thermostat for a 165 or 180 might be worth something.

More experimenting to do I guess...

I'm not sure on your setup, but if is FI, the injectors will always wet the manifold. The fuel is evaporated by manifold/head heat. Less temp may mean that it won't run as good. Just my .02$

[Belgian1979]

Belgian,

When you say...

"When driving at that speed (close to 3000 rpm) I'm seeing my engine produce around 60-65 HP. 20 HP might be if you have a very (!) light vehicle. 1 HP on 60 HP = 1.6%"

You are getting about 10 miles per gallon of gas at 60 miles per hour, is that correct?

My understanding is that to increase fuel economy, we need hot intake air because of MadBills explanation. Modern computer controlled cars can adjust the timing to avoid spark knock with the higher intake temps.

I have played with manipulating the intake temp ( just a little bit) on my 1983 Ranger 2.8V6 4 speed 4x4 by using a hand operated vacuum pump to operate the heat stove to the air cleaner from inside the cab. I found that power was way down at highway speeds with high intake temps in the winter. (If I recall correctly, I saw temps in the 150 Degree F range at 65 mph with outside air temp around 30 degree F). Drivability was not too good in stop & go driving. What I definitely noticed was that the throttle had to be opened more at 65 mph. My understanding is to improve economy we must open the throttle more to reduce pumping losses. Lower numerical axle ratios and overdrive transmissions are probably the most direct route to opening the throttle at cruise, but not necessarily cost effective.

I bought a 4 thermocouple sensor and measured the temps at thermostat housing, engine bay, factory cold air intake, and just above the carburetor. Probably the most interesting thing I discovered is that the thermostat housing temperature varies almost instantly with power output... I.E. open the throttle 10% to climb a hill on the intestate & watch the water temp increase 10 dergrees (approx.)

Last time I calculated it, my fuel consumption was 12 mpg on average, but that usually includes some higher speed driving (75 mph). Be aware that my engine is not tuned for economy. I do not run it any leaner than 14.0/1 in AFR. The engine doesn't like running leaner. Although it might be possible if the ignition timing was really optimized, which it is not.

[groberts101]

When driving at that speed (close to 3000 rpm) I'm seeing my engine produce around 60-65 HP. 20 HP might be if you have a very (!) light vehicle. 1 HP on 60 HP = 1.6%

As far as fuel injected vs the air temp and looking into my efi mat tables I see that the difference between 113°F and 68°F is roughly 8%. This would mean that 8% more fuel needs to be injected. Assuming an efficiency of only 30% (low ball) you would still have 2,66% net hp increase. Not a lot but still favorable.
However on acceleration and WOT this would become far more and favorable.

This all is not taking into account that when driving on 113°F air temp you would be closer to detonation with the same CR. So if you want to drive with hot air you would also need to reduce your timing and that would reduce your HP even more.

I agree. I tried most every trick in the book for my Vortec motored work vans and completely isolating the entire induction system with a foil faced/felt backed blanket(composite intake manifold top as well).. tune could be pushed harder and mileage always improved by about .5 - 1 mpg average. Could drive for hours.. pop the hood and the plastic tubing was still cool to the touch. Less throttle required to move those round edged bricks down the highway helped every single time. Paper physics is fun, thinner hotter air.. less ignition timing.. lower pumping losses.. but in the end creating the most cylinder pressure with the least amount of throttle/fuel input is key. Lean burn can be pushed harder. Larger tubed low restriction cool air intake systems are just another building block to get there is all.

This has always been my experience with carbed applications...colder engine and air temps, more aggressive tune, better mileage. I’ve never messed with this stuff on an FI application all that much before now.

This makes me wonder about the coolant temps too. This suburban always runs in the 200-208* range once warmed up...whether it is 60 or 110* outside. I’m wondering if replacing the 205* thermostat for a 165 or 180 might be worth something.

More experimenting to do I guess...

Anything you can do to cool the fuel and air mixtures down will allow a more aggressive tune by virtue of improving the engines octane tolerance. I ran a 160° in summer combined with water wetter and 180° in winter(occasionally a 195° during prolonged bitter cold periods) with anti-freeze.

I should also mention that both my Vortec engines were little 4.3 liters which tuned were before and after snipping the cylinder heads .050" and running thinner head gaskets too. One ended up with heavily ported heads with TONS of dreaded "low lift flow" due to bigger LS style valves, killer valvejob, and 1.8 ratio offset roller rockers working the tiny little stock cam(had to shave the short end of the rocker body and clearance the stock plastic valve covers to make them fit). I've done several 5.7's with similar cumulative mod's too. Light throttle and decel timing maps exceeded 50° btdc. So according to the laws of engine dynamics being put forth here(not implying they are wrong because I understand and agree with the physics behind them) my pumping losses surely went up and mileage should have gone into the toilet. Just the opposite occurred with more power from tip in to redline. Tires hunted for traction from standstill, would lay 2 fat 275mm sticky Dunlop tire stripes for about 10-12 feet and lay solid 2 footer scratches into second gear, when they were emptied of all work gear. They were torquey little "3/4 V8" beasts and beat the snot out of most much bigger engined trucks.

So regardless of all the dynamics that were working against me, and I tune ALL my motors this way.. the cooler the intake charge the better with tons of part throttle spark lead and work towards lean burn("the cooler the intake charge the better" is what makes this last lean burn part work towards improving MPG), I have learned that theory only goes so far and the real proof lies in the actual end result. So I'll repeat what I said earlier in this thread. The more aggressive the part throttle/cruise tune can be the more torque you will make. The more torque you make the less throttle you will need to accelerate and maintain speed. Getting a nice cool intake charge works towards that result and lean burn is just the icing on that cake.

[BobbyB]

Do any newer cars use heated intake air? All that I am aware of use only cold intake air and apparently tune the way groberts describes.

[Belgian1979]

All efi cars just use a programmed warmup enrichment.