DIY Warm-Air Intake
 

A request was made to post up some pix of my warm-air intake. It isn't fancy, but it does the job...

First, I removed the cold air tube and resonator (year-round: weight reduction) and the exhaust manifold heat shield.

Pick up some flexible exhaust tubing at the auto parts store -- you can bend it to conform to your needs. I drilled a hole in the side of my airbox to allow the tube attachment. A zip-tie holds it in place.

http://pic16.picturetrail.com/VOL698.../345085848.jpg

The difference in many airboxes vs. the Integra setup is the tubular style of the filter and a clean seal at the air intake directly from the filter assembly. This allows "dirty" air to enter at any place in the box. The stock air entry (front-bottom of the box) was covered with duct tape -- this makes it easy to peel it away when summer comes around again.

http://pic16.picturetrail.com/VOL698.../345085853.jpg

The hole was drilled to allow a tight fit. Simply crimping the end ensures that it won't slide out -- the tight fit allows it to not slide into the filter causing damage.

http://pic16.picturetrail.com/VOL698.../345085864.jpg

The piping doubles as the summer, cold-air intake, so the it's' a bit rusty, but it works. In my experience (with some Honda engines), if you get the IATs into the 100-110F range, you'll notice an increase in FE + faster warmups.

If your airbox is a "clean" setup, such as a drop-in, find the intake source and setup a similar routing . It may take some additional plumbing and duct tape :thumbup:

Enjoy!

-Rick

Thanks! Looks like a pretty easy mod.

I think that to make this work on my '97 HX I'll need to remove the cold air tube and fit the new intake where that one went. Because the Civic air box is set up slightly differently - very little surface area for a tube to be attached at the side of the box so I think the bottom is better.

Well now that I've taken a wrench to my car, it's not exactly an easy mod.

The Civic filter is rectangular and right up against the side of air box leaving little room for a hose opening there. I'd rather duct to the existing location at bottom of air box and reroute that intake tubing to the exhaust area.

I wanted to get the air box + intake tube assembly out but there's a crazy fastener for both at lower front of air box. Rather than bust it I think I'll wait till I can deconstruct one at a self service 'automotive recycling facility'. Hopefully one of these days, right after I finish a daunting batch of happy homeowner cleanup and maintenance projects.

My WAI was very easy to do:

Stock:
http://www.ecomodder.com/forum/attac...1&d=1205878693

WAI:
http://www.ecomodder.com/forum/attac...1&d=1205960270
http://www.ecomodder.com/forum/attac...1&d=1205960068

I'm trying to think back to when I had my '97 DX. The filter was on top of the intake manifold and ran to a resonator box where your filter is. If I remember right, it was a pain to remove, so I left it. That was back in the CAI days, so I just cut the tube and re-routed it. Most cars have this "clean" design (which makes my filter tube an expensive part to replace).

I'm sure you have the same problem -- there's a lot going on near the box intake -- hoses, coolant overflow tank, A/C lines, and the ABS unit for me. I didn't have much room to make a 90-degree bend and use the existing inlet, so I made a new hole. It's actually a bigger challenge to find cool air -- the tube snakes its way down to an opening in front of the wheel.

Tas- Nice! It looks good and was easy to install.

-Rick

RH77 - Would you not get even warmer air if you placed the heatshield back on, and put the tube behind the header?

Looks like you could make a simple metal strap that would bolt onto the header where the heat shield goes, that way you could keep the tube stationary, and still have the heat shield on...

And the heat shield keeps the header warmer which = better exhaust flow, so you'd be getting two benefits: warmer air and better scavenging of exhaust due to faster exhaust flow.

Version 1.0, 3-years ago, drew the air from between the heat shield and manifold. IATs were way too high -- 180F in the Winter! The faster warmups were nice, but detonation wasn't. v1.1 moved the tube to its current location, which is far enough away, but never broke 90F. Removing the shield allowed "v1.2" to reach 100-110F on cold days, 140F on 40F+ days (fall is a bit unpredictable). This is in combination with a rad-block and has worked well since.

I still have trouble getting the transmission up to temp with straight-cold starts (no access to an outlet for the EBH). The TC fails to engage for quite some time, despite full operating temps and nominal IATs. The situation is long-term airport parking, cold-soak, and immediate entry onto an Interstate highway. The only thing I haven't tried is an undertray to insulate the transmission housing from direct cold air flow (which doesn't make sense, according to the shop manual's flow chart of TC engagement).

I've always had a problem getting the TC engaged quickly from a cold start. The kickdown cable has been advanced to allow solid shifts and quick TC lockup when fully warm for a while. It's probably the fuzzy logic in the TCU preventing perceived cold lockup.

RH77

Yep.

So what I was thinking while asking about putting the thingy back behind the other thingy... (your V1.0...) was to also incorporate a cool-air tube with a variable valve on it, (techie term for a motorized flap), that would be controlled by the (modified) output of the IAT sensor... so you could basically keep your intake temp optimal, +/- 15*F (reaction time)

Plus, it wouldn't be too hard to route cooler air, since there was that nice resonator under the bumper that you took out... I'm thinking a nice little valve there, instead of tape.

See what I mean? Plus, by the time you're done, it could look mostly stock... if that's a concern. (For me, it usually is.)

I see what you mean now...

I've had plans for a temperature-dependent intake system for a while (everything from an elaborate plan to use servos with butterfly valves and 2 tubes to using a simple used part instead). I'm told that I could source used parts from some 90's Volvos, GM throttle-body injection intakes, or old carburetted setups. I just need to take the time. The current setup works pretty well...

So, how much efficiency can be gained by adding back the manifold shield? It was a rattle point, so it was removed. As for the resonator, it was pretty bulky, so I got rid of it. It never really sourced cooler air, just air restriction and full-throttle sound deadening + weight.

It was kinda a joke, honestly... it's marginal, if anything.

The idea is the same as with header wrap... keep the heat in the exhaust as long as you can, but if you're using it effectively for something else, I'm sure your WAI is overtaking any benefit you'd get from putting it back on.

Stop it from rattling - copper crush washers (read: fuel filter/rail banjo fittings) under each bolt, properly torqued to crush them a bit, should cushion the rattle.

Put grease on the bolts before you put them in.. they'll smoke for a bit afterward, but you'll still be able to get them out the next time you need to.


When I noted about wanting to put the heatshield on my aftermarket header, I basically plan on brazing some nuts to it that will act as standoffs, and bolt the shield back on, after using header wrap on the whole thing.

My concern is that it looks more like stock than anything...

I'll shortly be working on an '88 festiva, carb 1.3L as my first project. I noticed that on the intake hat, there is a tube running to the fender, and a smaller metal tube running up to a valve of some sort, the other end attached to a heat shield on the exhaust manifold. If i force this valve to remain open, is that going to give me intake air that is too hot? Is hot air gonna help that much, and how much will it hurt what power there is? 70 mile per day commute through rural Mississippi.

"Version 1.0, 3-years ago, drew the air from between the heat shield and manifold. IATs were way too high -- 180F in the Winter! The faster warmups were nice, but detonation wasn't. v1.1 moved the tube to its current location, which is far enough away, but never broke 90F. Removing the shield allowed "v1.2" to reach 100-110F on cold days, 140F on 40F+ days (fall is a bit unpredictable). This is in combination with a rad-block and has worked well since."

RH77: Have you tried changing the gap, heat range, type of spark plugs being used to fix the detonation due to high intake temps? I had a supercharger on a toyota tacoma and the discharge temps of the s/c was so hot that it caused detonation that could only be cured with timing adjustment and/or colder heat range plugs. Just an idea.....

I tried this same setup in my Civic, but for some reason it dropped my MPG. I just removed the flexible piping, and now I just have a large hole in the side of my intake where the cool air tube and resonator used to be, and I get much better mileage now. I figure it's pulling in warmer air from the engine bay, but not getting the extremely hot air from the headers. Seems to be a great compromise for my car :)

so what kind of gains did you guys get from wai??

I'm seriously looking at replacing the Cold Air Intake I've currently got on my 1991 Jeep Cherokee Laredo 4.0L (Spectre Industries Modular Tubes with Original Factory Bellows-Elbow and Amsoil Synthetic Dry Media Cone Filter) with a Donaldson G070020 Sealed Cylindrical Air Filter Housing and plumb a heat resistant duct to my replacement APN Exhaust Header in order to improve colder weather fuel efficiency. I'll try to post pics once its done.

I don't quite get this mod.

Warmer air is less dense, I get that. Therefore the car would run leaner if it thought there was mroe air coming into the engine than expected based off the air flow meter. However, if I'm not mistaken, most cars have BOTH an air flow meter and an intake air temperature sensor that sends information to the ECU. So, if that were the case for this specific car, I don't see how this would help since the ECU would just correct accordingly and inject less fuel anyways.

Optimally you would want cold air going into the engine(to an extent) and the ECU to know how cold it is and how much there is to inject the correct amount of fuel.

Is there something I'm missing?

Heat. The engine will run richer with cold air because the ECU adds more fuel to make it so that it can burn the fuel properly since cold fuel is hard to ignite.
The hondas seem to like it at 120f, it manages the same MPG gain as lean burn if memory serves.

I'm not sure I quite buy that. An engine that is already at an operating temperature of 200 degree or more is not going to have problems igniting the charge from a "cold air" intake because by the time is actually gets to the engine, it's plenty warm. Maybe this wouldn't be true if temps are down below say 40 degrees, but still I'd have to see really solid data showing good gains to believe this is beneficial.

Cold air intakes are good for both power and mpg. A denser charge is a good thing.

My Prizm has seen a 4 MPG boost from the WAI and my average temperature is in the 70's.
When I put the CAI back on, I see it drop back down to 33 MPG.
Half the problem is that the engine has a hard time getting up to operating temperature quickly.

Is that in primarily city or highway driving?

50/50 split.

My reasoning behind a WAI is that warm air would help the engine warm up faster and stay above 195 degrees Fahrenheit, in order to stay in closed loop operation more often, and to bring about a more complete atomization of the fuel droplets from the individual injectors as each one of them sprays a pre-determined amount of fuel (based on RPMs, load on engine, current engine temperature, etc., etc.) into each intake port of each cylinder in turn.

I've found that my 1991 Jeep Cherokee Laredo 4.0L engine runs best at between 210 and 225 degrees Fahrenheit, ESPECIALLY when it comes to fuel efficiency. As the cooling system is pressurized to around 13 PSI above atmospheric pressure, I'm not too concerned about overheating, as long as ALL links in the engine cooling system are free-flowing when they need to be, and properly maintained on a regular basis (back-flushing, thermostat operation checks in boiling water with a thermometer, replacing hoses when they begin to swell up at their clamped ends, etc., etc.).

Cold air slows down the proper atomization of fuel, even from the injectors on a multi-port system, requiring more fuel to compensate for the slower evaporative rate at colder air temperatures. Why do you think the cold-start fuel consumption, before closed-loop operation temperatures are reached, is much higher than when the engine is fully warmed up? This is due to open loop enrichment in order to compensate for the fuel droplets' tendency to clump together during colder engine operations during warm-up, especially right after cold start-up. Also, cold air would cause an engine to take longer to warm up to closed-loop operation temperatures, adding to the higher-fuel-consumption-after-cold-start-up issue.

No, cold air intakes are NOT the best for fuel economy, even though they are SUPPOSEDLY great for boosting high-end Horsepower and Torque. However, fuel efficiency appears to be the MOST optimal in about the 1/3-2/3 RPM range, or between 1650-3300 RPMs in the case of my 4.0L Jeep Cherokee Laredo, at an air intake stream temperature of around 90-120 degrees Fahrenheit. However, cooling the fuel to prevent vapor lock, which has occured on my vehicle already at least once, on a really hot day in which the fuel got really heated up to the temperatures inside the engine compartment, might be a good idea, if it doesn't interfere with improving fuel mileage to any appreciable level. Does this reasoning make any sense to you at all?

Yes the reasoning makes sense. I can easily see how it would warm up the engine quicker, but, at least for my driving habits, that wouldn't be very beneficial.

Comparing cold start efficiency isn't a good comparison because the engine is cold. A warm engine, even on a day with cold temperatures will not necessarily have a problem evaporating fuel due to the heat from the warm engine right underneath that throttle body.

Also, if you want to increase operating temperature, why not just change your thermostat?

This is my understanding: there is some point at which the intake air is "warm enough" to not have efficiency losses, and I never would have imagined that you would need to modify your intake to achieve that. I suppose it would make sense, if you do alot of cold starts, to do the modification to improve warm up time, but it would still cost you power when the engine is warm.

Even on relatively cool days (40 degrees), if I open my hood, it is plenty warm and I can't imagine the intake air being much colder.

You might consider editing this page http://en.wikipedia.org/wiki/Warm_air_intake

Because whoever wrote it clearly doesn't get it

"My reasoning behind a WAI is that warm air would help the engine warm up faster and stay above 195 degrees Fahrenheit"

Every car's cooling system makes sure that the car stays at operating temp after it's warmed up by using a thermostat. If you're dropping below what your t stat is rated at, then you have a bad t stat or you've been coasting down a hill too long.

The issue I have is NOT with my t-stat, as it is already the maximum available opening temperature, and is working as it should, as of my last drive. What IS the issue is the temperature of the AIR going into the engine cylinders through the intake manifold, from outside the engine compartment's exhaust manifold side, where a lot of the heat-flow seems to be concentrated.

Also, I'm basing my idea on a "heat riser" on the intakes of older, carburated vehicles to not only warm my vehicle up to operating temperatures faster, but to also keep the intake air temperatures warmer than outside-the-vehicle temps, or even ambient engine compartment temperatures, as well, using heat off the Exhaust Manifold to do so.

Plus I'm not looking to increase Horsepower and Torque in the upper RPM band (3300-5000), but to improve fuel efficiency in the mid-range power band (1650-3300 RPMs). In fact, I DON'T give a Rat's Fat Ugly Tuchus about upper RPM band gains, as I've already done a number of mods on my engine block for better air flow (Ported and Polished Head, Roller-Tipped Rocker Arms, Anti-Pump-Up Valve Lifters, Oversized Intake & Exhaust Valves).

All I REALLY care about is squeezing as much fuel efficiency out of my I-6 as I can, based on what I've observed over the years as to what works v.s. what doesn't, even if my Upper Power Band suffers. Cold Air Intakes have NOT worked for me in my current vehicle's application, so I'm going the opposite direction to see what that will do, that's all. Do you now understand my reasoning a little better?

Plus your having mentioned your own driving habits as you did, would suggest you're a Jack-Rabbit-Style Skinny-Pedal-Stomper from all stopped positions, at least to my way of thinking, not someone who eases their foot onto the gas pedal in a common-sense manner, like I always try to do.:rolleyes: I also have to wonder if you've got one of those Coffee-Can-Mufflers on your car, like one of those Rice-Rocket-Honda-Boiz.:p If so, then I'll just have to start calling you "Fart-Knocker-Ricer-Boi" whenever interacting with you on this forum, from now on, just to get my lols, heh, heh, heh.:D

Maximum rated power would go down, but who cruises down the highway at wide-open throttle?

I've seen about a 5% improvement in FE from raising my truck's intake temperature 50 F above ambient.

How so?

Is your jeep throttle body injected?

Carb'd engine did get their intake air from a hot source when warming up, but once the car was warm, it had a mechanism to switch to colder source. Also, Fuel injectors make it much less important since they evaporate the fuel better.


If you say it gives you better mileage, I'll buy that.

More power means you can get up to speed faster with the same shift points.

5% is a good improvement, and worthwhile. I'm curious how much this mod helps with an already warm engine going down the highway - in other words, if you took the cold start out of the equation.

I don't know that much about warm air intakes but I have read a lot about them...


from all the things I have read the 2 major benefits are introducing heat into the engine for a faster warm up to get to closed loop faster which saves fuel.

Then the other benefit is to potentially reduce pumping losses. Cooler air is more dense and contains more oxygen. More fuel can be added for the given volume which produces more horsepower. This is useful if you want to get every bit of power from an engine while running down a drag strip. However idling at a light or cruising around town you don't need power. Yes you may use less throttle but your pumping losses will increase. It takes fuel to turn the engine, with cooler air it takes more fuel to reach stoichiometric combustion....since you aren't using the power the engine is making most of the power is being used to turn the engine.... ergo pumping losses... you are paying money to move cold air through the engine.

In theory warmer air = less fuel for given volume = throttle open a little more = less pumping losses = more efficient engine = ???more mpg???....

This is what I'm trying to make the point on to you, 13B_88FC, a.k.a. Fart-Knocker-Ricer-Boi, about Warm Air Intakes v.s. Cold Air Intakes. Plus I'm not looking to build a racing machine. Instead I am looking to improve what I currently have for my daily commute. Since I don't go driving around at near-WOT-to-WOT like SOME people seem to think they should for MAX-Performance, I'm hoping to maximize fuel efficiency by driving conservatively, while using the Warm Air Intake idea I have to ensure a more complete mixing of air and fuel droplets from EACH of the SIX injectors on my 4.0L I-6's Intake Manifold.

My thinking is, if the Intake Air Stream is 30-50 degrees above Engine Compartment Ambient, the fuel droplets from each injector's pulse would be more likely to evaporate quickly enough to compensate for the lowered oxygen density of the warmer/hotter air, than if I were to drop the intake air charge temperature to BELOW Engine Compartment Ambient Temperature, which is what CAIs are supposed to do.

The use of a CAI would be more likely to cause the droplets to clump together more as they entered the Cold Air Stream into each of the intake ports on the head(s), requiring more fuel overall to be used per cylinder, whether on post-cold-start-warm-up, or once at operational temperature. By heating up the intake air charge to well above Ambient Engine Compartment Air Temperature, I'm hoping to avoid this, or at least reduce its likelihood, especially if it improves overall MPG, like I think it will.

Btw, the 4.0L Jeep engine NEVER had Throttle Body Injection since Day One. Even during the Renix years, it was a Multi-Port FI system. The earlier 4.2L Jeep I-6 WAS carb'd with a Carter "Chug-and-Glug", which was not as fuel efficient, or powerful as its younger 4.0L sibling, but not the 4.0L itself.:rolleyes:

Lol.. Ricer boy? Please, calling an rx7 a ricer is like calling a Lamborghini a muscle car. I mean seriously, these cars would just melt the glasspacks that people put on their gay ass hondas.

I figured you weren't trying to build a racing machine when you mentioned you had a jeep.

Of course your sly stereotypes about me driving around at WOT all the time are completely dead on... except not. Although to be honest, my fuel mileage is hardly affected by how hard I drive my car, unless of course it's just being turned into heat in the brakes. My car loves to rev... and you have to get up to speed somehow whether it be slowly at an arguably efficient engine speed or quickly at an arguably inefficient engine speed... it ends up being pretty damn close to the same amount of fuel used


I think there is an intake air temperature that is "warm enough" and gives optimal fuel evaporation when the engine is warm. A warmer air intake will help warm up the engine quicker and it will help in very cold climates. Most of the time though, I don't think it is necessary or will do much good.

Thanks for letting me know about the jeep engine's fuel injection systems.

Glass pack mufflers are a great viable option for high performance applications in the racing world. They are free flowing, light weight and just enough to let the person abide by the noise restrictions many race tracks have put on different classes of vehicles.... They are tough, simple and robust. I would love to see a rotary try to melt one.

Accelerating at 2 different rates isn't necessarily going to use the same amount of fuel. Especially if you end up going in to enrichment mode during the acceleration. Turning the engine at lower revs utilizes the engine more efficiently than turning it at higher revs. You don't want to lug the engine though that will retard the timing which lowers power and the ECU will add a lot of fuel to prevent damage which would waste fuel.

You're driving a Mazda RX7?:eek: DEFINITELY a Fart-Knocker Ricer BOI...lollollollollol!:D But seriously, Mazda RX7s ARE also a Japanese design, as well as import.;) Also I still STRONGLY disagree with your notion that my WAI idea is not necessary nor will do my Jeep any good.:mad: So now the Comparison War Gauntlet would seem to have been thrown down...let the Flames of WAI Fuel Conservation v.s. CAI Gas Guzzling War of Words begin!:D

Another thing - assuming that a given engine does not go into enrichment, brisk acceleration does tend to use less gasoline than accelerating slowly. Brisk acceleration tends to put the gas engine closer to peak BSFC than slow acceleration.

I agree glass packs are good muffler solutions, however it is common knowledge that rotary engines melt them very quickly (anywhere from a few hours to a couple months) unless they are very high quality. They're just commonly associated with "ricers" which is why I brought them up.

I didn't say it would use the same amount of fuel, I said about the same amount. Most people over generalize and say that accelerating quickly is bad for fuel economy. Gasoline engines are more efficient at high load - they're making the most POWER per unit fuel burned when they're working hard, however the higher you rev, the more of that power is going towards counteracting the friction of the engine. In my opinion, the most efficient acceleration would be to sandwich the toque peak between shifts since that's where you're making the most power per RPM.

My stock peak torque is 3800rpm, right before my 5th and 6th ports open up. however my engine has a decent sized street port which probably raises the torque to around 4500 or maybe more; it seems to really pick up around 5k.

"enrichment mode"
A well tuned engine should (key word here is should) simply inject a linearly proportional amount of fuel based on the air flowing into the engine. Why would there be an enrichment mode? As far as I know, your air/fuel ratio should remain pretty constant throughout the power curve of the engine.

You're driving a jeep, of course you view every import car as a ricer. No ricer is faster than the mustangs and camaros of the same year, not to mention much better handling. Ok, ok, so probably only the turbo rx7's were faster, but still.

I never said YOUR jeep. You say it works for your car, then I believe you, which I have said previously.

I think we both have the right ideas, we just disagree on specifics. There is no golden rule. Cars are different, there are way too many variables.

My lifetime average with the CAI on my Mustang has been 20.4. My last two full tanks have been with the stock airbox back on and I will do a WAI after I am done with this tank. The two stock airbox tanks were 22.4 and 22.6, (647 miles on 28.722 gallons for 22.5 MPG across these two tanks) in winter, 45/55 city/hw driving.

A comparable tank from last fall/winter was in Oct when I did 19.8 on 40/60 driving. I did a 16.3 last Feb but that was 100% city.

A comparable tank from summer was 20.7 MPG on the 3rd of July with 50/50 driving.

I love that I'm beating a warm weather CAI tank in winter with the stock airbox.

What kind of cold air intake is it? Is it just heatshielded or is it taking air directly from the outside?

Definitely NO Absolute Golden Rule in THAT regard, just a general rule of thumb, with plenty of exceptions, especially with fuel injection systems and MAFS versus MAPS (my Jeep uses a MAP Sensor,which seems to like WAIs, instead of a MAF Sensor, which does not seem to like WAIs). Also, the thing to remember is that a Turbo-charged Rotary, or Wankel engine is quite a bit different from a naturally-aspirated inline-six reciprocating engine design, like what I have on my Jeep. Even though they do basically the same thing, i.e. pushing your vehicle down the road, they operate by somewhat different principles.

I remember one of my Automotive Technology teachers telling me about how fuel inefficient the first Mazda/Wankels were when they were introduced, and how they had a bad tendency to produce more smog than an equivalent displacement piston engine. He also touched on the inferior grade of materials used in their engine block-segment-to-block-segment seals. However, the high RPMs range was where they had their equivalent piston engine cousins beat, in both HP and Torque. It was not uncommon for a two-rotor Wankel to push 200HP near a VERY high Redline RPM and there was even a four-rotor design that would have put out as much as 400 HP, had it been utilized to any serious degree (never heard back about THAT one, though).

Buuut, compairing your Mazda RX7's Turbo Rotary/Wankel to my Jeep Cherokee Laredo's 4.0L Inline-Six is like compairing apples to kumquats, in my personal opinion, as a different set of rules MAY need to be applied to YOUR vehicle's engine in order to improve it's fuel efficiency over what it is currently. Plus if your engine uses a Mass Airflow Sensor, instead of a Manifold Absolute Pressure Sensor, as what's on my Jeep's intake manifold, your R/W may NOT likey the WAI that my Jeep 4.0L MAY likey. Understanding this MAY help you find your own solution(s) to your potential Gas-Guzzler issues, besides just driving like you've got a raw egg under your accelerator pedal, which I do to some degree as part of my modified Hyper-Miler regimen anyways. Hope this helps, even if only a little...

Yes, two completely different engines, that I wasn't trying to compare.

the later model 13b twin turbo's in the 3rd gen rx7 produced up to 276 hp (limited by japanese regualtions)

There were no 4 rotor street engine produced by mazda, however their 787B which won lemans (and of course was later banned) was a 4 rotor NON-turbo with 650hp.