CAI’s...do they actually work?

[travis]

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...your saying spending $500 to save $100 worth of gas is not good economics?

[rfoll]

The oem put cold air on there for a reason, they wouldn't spend the money if it didn't help the CAFE bottom line. My neighbor has a same year 1 ton van, with the same engine package, and he gets 14 mpg pulling a small trailer. I would be wondering about the tune. Those engines are notorious for eating distributor caps.

[travis]

The oem put cold air on there for a reason, they wouldn't spend the money if it didn't help the CAFE bottom line. My neighbor has a same year 1 ton van, with the same engine package, and he gets 14 mpg pulling a small trailer. I would be wondering about the tune. Those engines are notorious for eating distributor caps.

I’ve heard that about the distributor caps, and the plug wires on these engines. Also heard that pretty much all of the parts store plug wires any more are pretty much junk. The plug wires are the only thing I have not replaced yet, but I’ve got a set of Taylor 8mm spiro wires coming

[BigBlockMopar]

I fabbed a CAI on my daily '73 Dart some years ago. Didn't do much if anything for mileage.
But it did get rid of the laziness the engine developed when everything under the hood was warmed up after some driving.

Did a 'crapload' of other stuff on the car to get the (lousy) mileage up, but can't say all I had done was succesful.
I did however, make the much more fun to drive. So in that view IMO it doesn't quite matter if you spend more then the inprovement in mileage nets.

[BILL-C]

I’ve had horrible results with parts store distributor caps. Genuine Chevy cap from dealer worked perfect.

[MadBill]

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.

Now there's one that virtually always helps! The air flowing under a vehicle is very turbulent and produces much drag. A number of trucks come with air dams, usually on light-duty models, strictly for improved economy, but these are usually limited in depth to ensure good ground clearance.

We made a very rudimentary one for my friend's GMC van. We basically just fitted a big vertical sheet of aluminum (Detroit Wonder Metal or If it's not too cantilevered, Coroplast is easy to work with and would work too.) between the bumper and its mounts, reaching to ~ 5" from the ground, then trimmed it bit by bit until it (mostly) stopped touching down on bumps.

Not only did it have a very noticeable impact on mileage (~ 2 MPG @ 60 MPH), it also got a ton quieter, especially at 40-60 MPH.

[groberts101]

I am extremely skeptical of things like this, but I keep reading so many positive reviews I can’t help but wonder if there is some truth there.

In a couple of months I’m going on a 4000 mile trip in my 1999 Suburban C2500. It is a stock L31 with a fresh tune up, only “mods” are the upgraded GM injector spider assembly and a custom Spintech dual 3” in/single 3” out muffler. I run stock weight full synthetic oil.

I’m trying to up the highway fuel economy a bit. While investigating different options one of the big things that keeps coming up is CAI’s. Claims are typically .75-1 mpg, up to as much as 1.5mpg gain on these suburbans. Is that even realistic? The stock air filter is huge, and it draws air out of the inner fender, so it’s not like it is breathing hot under hood air. Plus highway cruising speeds are only in the 2200-2400 rpm range so it’s not pulling any crazy rpms.

Any suggestions to help the current 12.7mpg highway average would be appreciated. 1.5mpg at this point is a pretty significant gain. A little extra power too is always a good thing, a stock 350 can only do so much in a nearly 6000 pound tank.

Most of that is advertising to lighten your wallet but there is most definitely merit to smaller sq/in induction systems with better flowing filter elements in reducing pumping losses. Never once had one lose power and/or mileage over a factory setup. And if it does you need to revamp the layout or design and keep tuning till you find the net gain.

As for the heat and larger throttle angles helping engine efficiency.. sure.. OEM's do it all the time but that's not the only reason they do it either. Emissions are their major achilles and they are willing to trade low speed throttle response and torque to gain in that specific area. Tuners can have a heyday with all that gets left on the table due to NVH and emissions. However, I have never, not even once, seen a hotter induction with larger throttle opening make more power, low speed or otherwise, and gain mileage over a well sorted cold air induction system having much fatter ignition curve and smaller throttle angle with higher manifold vacuum. Not even once on hundreds of tuned vehicles with various mod's from milder to wilder.

I have learned by consistent and repeatable results that generating the maximum amount of torque output at the lowest possible throttle angle will always make the car accelerate easier and quicker while using less throttle to reach its final gear steady state cruising speeds. Cooler denser air has more kinetic energy power potential and allows more ignition lead which further improves manifold vacuum.. which denotes burn efficiency all unto itself. Sure the motor will fatten up the fuel curve a bit and pumping losses can rise but the added benefits of all mentioned above can and does improve torque output to enough degree that those losses are overshadowed when the gas pedal is kept under control. Use less throttle to accelerate and maintain steady state cruise and you will gain mpg. If I had to put a number on it.. I'd say 1-1.5 mpg is about average improvement but some of that comes from the retune as well.

If you want the full potential you'd also need to mod that throttle body hat too. Not the greatest design with its squashed height and abrupt 90° sharp edged turn on the short side.

PS. If you're interested I can dig out my mod'd t-body hat and snap a pic to sjow you what can easily be done. It's not the prettiest putty work I've ever done but this stuff is all about shape and sizing anyways.

[rfoll]

I have seen a number of cases where aftermarket air cleaners and induction systems will totally destroy the fuel curve. My neighbor has a 1998 3500 with a Vortec 454. The previous owner had installed one of those systems and destroyed the economy and it made so much noise at cruise he couldn't hear the radio. He put the stock stuff back on and all was well again.

[JoePorting]

To improve fuel economy, I'd replace the O2 sensors even if you think they are good, replace the coils and spark plugs and wires, and run NGK Iridium spark plugs.

If the battery is more than 3 years old, replace it. Old batteries will draw down your electrical system making everything run bad. Replace air cleaner and run a bottle of fuel injector cleaner in the tank.

You should be getting around 17 mpg, so something is wrong.

[midnightbluS10]

I agree with most of what Joe posted, also. Replacing the spider injector, fuel pump, distributor, cap&rotor, plugs, wires, coil, fuel filter, etc when I did the K&N & Dynomax probably helped considerably. But then, I do frequent maintenance on my truck so it may not have helped as much as it could've.


I do know this. I've not driven a single 4.3L S10 or Blazer with the power mine has. Working at the Chevy dealership, I got to see them often. Mine snaps necks when I matte gas. Most others just sluggishly take off.

Can't wait to get it back out to the track for some updated time slips on the new motor.

And as far as the value of it? Pretty sure I've made my money back in gas savings over the last 6 or 7 years. If not, I will eventually lol.

[BigBlockMopar]

Now there's one that virtually always helps! The air flowing under a vehicle is very turbulent and produces much drag. A number of trucks come with air dams, usually on light-duty models, strictly for improved economy, but these are usually limited in depth to ensure good ground clearance.
...

I think there's even more to it.
A front airdam creates a low pressure area behind it, which could help hot engine-bay air to be drawn out and ventilated easier, which in turn cools the area and improve airflow through the radiator.

On my car I installed an aftermarket front spoiler/airdam from a '80s Mercedes.
The fit was near perfect and created a nice air dam. I even extended the spoiler another 1.5" with a rubber lip.
The car's mileage is still to inconsistent to see what it did, but it improved the car's looks in my view as I never much liked the 'open' low front end of it.

About CAI-systems, did anyone here go even a step further and double insulate the tubing and airfilter housing to counter heatsoak at slow driving/prolonged idling?
How about fuel-line insulation?

[Truckedup]

If not mentioned, folding the larger truck type mirrors back can be worth nearly 1 MPG on some vehicles.. To me, with the engine running at 2200 rpm at somewhat high intake vacuum, intake air flow improvement should not make any real difference ?

[ijames]

One good resource for improving mileage is www.ecomodder.com. These guys are the hotrodders of mileage, trying all kinds of aero, engine, and driving mods in the quest for improved mileage. For some reason the site would lock up my browser (both IE and Firefox) fairly often, but maybe that was just my system?

[travis]

I was looking at the front end this morning...there is no air dam/valance under the front bumper. There are mounting holes but no signs there has ever been one on there. There is a bunch of stuff in the way of any sort of smooth airflow underneath...it looks like it would be quite the turbulent mess under there. And a stock replacement air dam is like $12! I just ordered one...certainly can’t hurt to try for that price!

The mileage drops very very quickly at anything over 62mph. This could very well be the big difference between my buddies k1500 and mine...his has the air dam.

[dfarr67]

Either buy a truck spec'd to your needs. Or if your happy with this one, I'm sure with 3:73 gears a vortec 383 long block with uprated spider injectors and a good tune will serve well. Everything else is a bandaid.