CAI’s...do they actually work?

[cjperformance]

My daily hack is a 4.0L 6cylinder stock standard. Economy is as predictable as the sun rising! Its efi and has a factory pickup for cold air. The pickup can be easily removed so engine bay air is picked up instead. Its winter here now. 10/14°C days. I have just filled it so i will remove the cold air pickup and do a comparison over the next 2 tanks. About a week and a half driving for me.

[travis]

My daily hack is a 4.0L 6cylinder stock standard. Economy is as predictable as the sun rising! Its efi and has a factory pickup for cold air. The pickup can be easily removed so engine bay air is picked up instead. Its winter here now. 10/14°C days. I have just filled it so i will remove the cold air pickup and do a comparison over the next 2 tanks. About a week and a half driving for me.

I’d be really curious to see how this works out for you

[travis]

2X! Cold air helps power but hurts economy. Adding a heated intake like the exhaust-warmed GM Thermac air cleaner system used in the seventies and eighties could measurably improve economy.

My buddy bought a new 1970 GTO and commuted daily ~ 80 miles. He kept close tabs on the fuel economy for years. One (Toronto) winter the cable-operated ram air stuck in the 'cold' position and he lost almost 2 MPG (~10%) until it was repaired.

“Cold” is definitely a relative term right now...it was 108* here today

Sounds like I have some experimenting to do. I could see it working either way...cold air, more power, easier for an under powered engine to move it down the road, or hotter air, less pumping loss.

I will do some testing over the next couple of weeks and see what happens.

[midnightbluS10]

Get a scan tool and observe IAT's of a stock intake system vs cai. When I compared mine using a Tech2, the cai had IAT's just a few degrees over ambient. The stocker was much warmer. I don't remember how much because it was about 8 years ago but there was more than just a negligible difference. Especially when you removed a headlight, which I usually do when at the track. No reason to not give it a straight shot right into the cai.


Mine helped power and economy. Truck ran over a second faster than stock with ONLY K&N FIPK and Dynomax cat back mandrel bent exhaust. Also started regularly getting 18-22 mpg regularly when before, I struggled to get 16-18. That was on a well-used engine with 225k+ miles and 100psi on 1 cylinder.

I've had this truck for 10+ years so I'm quite familiar with its mileage, how fast it is/was, etc... I've since put in a new, 0 mile LU3 V6 from Chevrolet Performance around 2012. It's got around 10k miles on it since then but I've yet to make it back to the track with it for a comparison of the 250k mile engine vs the new one.

[cjperformance]

My daily hack is a 4.0L 6cylinder stock standard. Economy is as predictable as the sun rising! Its efi and has a factory pickup for cold air. The pickup can be easily removed so engine bay air is picked up instead. Its winter here now. 10/14°C days. I have just filled it so i will remove the cold air pickup and do a comparison over the next 2 tanks. About a week and a half driving for me.

I’d be really curious to see how this works out for you

I can also , as per midnightbluS10 suggests, check IAT with a scan tool when I do this CAI on and off test.

[Circlotron]

Maybe a vacuum operated flap for cold air when you floor it and hot air the rest of the time.
For a spreadbore carburettor setup, how about hot air to the primaries and cold to the secondaries? That would be different.

[Dan Timberlake]

only “mods” are the upgraded GM injector spider assembly and a custom Spintech dual 3” in/single 3” out muffler.

Did the muffler do anything for mileage?

regards,

Dan T

[hoffman900]

I just want to put the qualifier out there to not spend more in trying to save gas than you’ll actually save in gas.

Doing some quick mental math, going from 12.7mpg to 14mpg will save you ~$200 ($3.50 a gallon) or so. So keep that in mind.

Carry on!

[BILL-C]

I owned a 97 K 1500 Suburban 4X4 with L31 ,4l60,3.42 gear, 100% stock in every way. It would tow a 6k lb enclosed trailer decent (just wouldn't stop) and had reasonable gas milage if i drove like that was my intention. Lightweight, it would get 17 mpg at 65mph. If i put the cruise on 80,then mileage would drop to 15 or so. There is something wrong with your truck if a 2wd version only gets 12 mpg on highway at 65 mph even with the 3.73 gear.

[cjperformance]

I just want to put the qualifier out there to not spend more in trying to save gas than you’ll actually save in gas.

Doing some quick mental math, going from 12.7mpg to 14mpg will save you ~$200 ($3.50 a gallon) or so. So keep that in mind.

Carry on!

So true!

[MadBill]

Maybe a vacuum operated flap for cold air when you floor it and hot air the rest of the time.

That's how the GM system (and others I expect) worked https://www.google.ca/search?q=thermac+ ... 45&bih=885

Also, I recall a GM engineer ~20 years ago describing the 4L80 trans as a 'built-in chassis dyno', at least as far as WOT power.

[jed]

My suggestion is to try aerodynamics. Don't ask me how or what I don't know.
Maybe a belly pan and some kind of frontal design. Something over the finder wells.
Don't worry bout how hokie it looks you'll never see those people again.
Just rember what Hoffman said it got to be cheep or u are defeating your purpose.

[Carnut1]

Travis, mod up the stock air counduits and give the stock throttle body a reshaping. Maybe a K&N air filter. Not free but cheaper than some ideas. Good Saturday project.

[Carnut1]

0408181047.jpg

https://www.google.com/url?sa=t&source= ... TZ5nAf0x_a Quicky tb mod. Change edge radius.

[travis]

only “mods” are the upgraded GM injector spider assembly and a custom Spintech dual 3” in/single 3” out muffler.

Did the muffler do anything for mileage?

regards,

Dan T

The factory exhaust system on this truck consists of the iron manifolds, a short section of 2” pipes, then balloons up to 2.75” duals back to dual 2.75” ID cats, then a dual 2.75” in/single 2.75” out muffler, and a 2.75” tail pipe, all stainless. After the short section of 2” pipe, this is the exact same exhaust as what was used on the L29 suburbans. When I got the truck, the stock muffler was missing...it had a Y-pipe connecting the 2.75” duals to the single tailpipe, no muffler. It was ridiculously loud and sounded like crap IMO. The stock muffler, or an exact fit stock replacement, is not available, so I tried a few different configurations. 1st, I adapted a pair of 2.5” I/O Pypes M80’s with turn downsI had laying around. Better than no muffler, but still way too loud and too much drone. Then a pair of Flo-pro 3 chambered mufflers with turn downs that I had laying around. Sounded perfect, but hung too low and looked terrible hanging down under the truck. Then a reversed single 3” in/dual 3” out Summit turbo muffler with a 3” Flowmaster tailpipe. Kinda loud but minimal drone and sounded pretty good, but I definitely lost a little power and lost about 1.5mpg iirc. Nobody else made a muffler that I could use as a dual in/single out setup within the confines of the real estate available, and with close to the correct spacing between the dual inlets, so I ended up having Spintech build me one of their “RV” series mufflers to the constraints I had to work in. The power and mileage came back to where it was with no muffler, but no drone and I love the sound...mildly aggressive but not obnoxious at all.

Well...that was long winded