warm air intake is in

[Jay2TheRescue]

Ok, I found the wireless outdoor thermometer. I can't tell much from this morning's drive to work though. I only live about 2.5 miles from work, and as if by some miracle, I got every light green this morning. The thermostat just opened up right as I was pulling into the parking space. Ambient air was 71.5, and right when I shut the truck off the reading behind the radiator was 75. I'll see later when I go to the bank. There are 2 lights you have to go through to get back out onto the main road. It is nearly impossible to get both green, as most often the first light doesn't turn green until the second is turning red 200 yards away. The truck should definately be warmed up after that...

-Jay

[Project84]

Jay, that's exactly what I was describing as giving you no benefit at all, and in fact, causing a vacuum on your intake air. I really don't think it's going to push any air in.... consider the location of your fan, it's job is to PULL air...

I still don't think RAM air is the way to go... on old SBC w/ carbs I see the benefit, but w/ FI now days, and the use of IAC or Idle Air Control valves... the computer is going to see the "pressure" if you get any, and it will add fuel or retard timing to adjust.

[Jay2TheRescue]

Originally Posted by Project84

Jay, that's exactly what I was describing as giving you no benefit at all, and in fact, causing a vacuum on your intake air. I really don't think it's going to push any air in.... consider the location of your fan, it's job is to PULL air...

I still don't think RAM air is the way to go... on old SBC w/ carbs I see the benefit, but w/ FI now days, and the use of IAC or Idle Air Control valves... the computer is going to see the "pressure" if you get any, and it will add fuel or retard timing to adjust.

That was one thing I was hoping someone would comment on. It has a 350 V-8 with TBI and OBDII. I wasn't sure if the mass ariflow sensor would notice the increase in pressure, and the computer would respond by adding more fuel. My dad also mentioned last night that he wasn't sure that the extra "plumbing" would pass the visual inspection durring the emissions check. If I did do it, I'd have to do a really good job to try and make it as stock looking as possible. This of course will increase my costs, as I'd no longer be using scrap parts to do this. I'm thinking it was a wonderful topic of discussion to spur debate, but I am starting to think that there isn't much, if anything to be gained by this. Then to add potential hastle during the emissions test, I'm thinking of looking for other ways to increase my mileage.

[GasSavers_BEEF]

I say with a 2.5 mile drive, buy a bike (and yes I mean bicycle) unless you need the truck for your job.

lose weight, feel better, save gas

[Jay2TheRescue]

Originally Posted by BEEF

I say with a 2.5 mile drive, buy a bike (and yes I mean bicycle) unless you need the truck for your job.

lose weight, feel better, save gas

I have a bike, but being the owner of a small business I have to go out to the bank daily and make my depsoits. Granted the bank is only a mile away, but its a mile down a busy 6 lane road with no sidewalks or bike lane. I also like the idea of walking 20 feet out the door of my business, get in the truck, and lock the doors. I have thousands of dollars in cash in that little blue bag. I feel its a security issue, and I don't want to get hit by a car on the 6 lane road.

I also need a vehicle for the occasions that I have to drive out to a customer's home to make a delivery. On top of that, on days I work, I work 14 hour days. I don't need to loose another hour of sleep just to bike. Unfortunately I need a vehicle. I do keep a log and write the mileage off on my taxes though.

I would also like to report on my findings of exactly how hot it is behind my radiator. Warmed up and going 50 mph the air behind the radiator is only 8-10 degrees warmer than the ambient air temperature. The warmest temp I recorded while running my errands today was 101.7. I guess this means that GM really put a good cooling system in. It seems to work quite well. I don't think I am going to see any gain from an increase of only 10 degrees. Maybe I can push this to 20 degrees with a partial grille block, but I don't think its worth the effort now. I had thought the air behind the radiator would be much warmer.

[Project84]

Today on the way to a local junkyard I got up to 160*F intake air temp, there was a noticable loss in power, but not so much that I was shocked. Seems my heat shield will probably be all I need to get to 180*F, and once the temps are getting that high, I'm going to need the tubing all insulated anyway because the A/C lines are currently touching the flex tube and where I don't use it much, it's still in working condition and a good selling point when I decide to sell, so I don't want that getting messed up.

I have some down time right now, so I might go play with it some more.

[GasSavers_Howard]

The hot air intake is a concept I have pondered since 1979, but not tried, though I did play with vaporized fuel at one time and saw no significant benefit. My original concept was to use a VW Type 3 because in those days it was about the only EFI car readily available. I called the combined system using vapor fuel and and warm air "VF HATS" for vapor fuel / heat attenuation throttling. I never got past the vapor fuel which I did on a generator engine (a big one), with a knows stead load. I used a generator so I could adjust mixture manually, as well as timing, working with a fixed load. The generator served as a dyno. The load was a very large heating unit. The result was no observable improvement in economy as measured by fuel used per unit of time, directly measured. As I said, I never did play with heated air.
I have looked at heated air for a couple of years, with an eye toward installing a system on my 1997 2 WD Chevy full size pickup with a 4.3 V6. Here's my take on the matter. It is known and observable that high compression yields better efficiency at cruise on a given engine in a given vehicle. I have seen this time and again. High compression results in pre-ignition under heavy load, so high octane fuel is needed, but ONLY needed under high load.
High compression results in HIGHER TEMPS at TDC of the compression stroke for a given CFM of air flow. My thinking is that the efficiency derives from temperature, not pressure.
Using heated intake air simulates higher compression ratio as the temp at TDC for a given CFM of air flow (measured before the heater).
High temp intake air is a liability at high throttle positions, and would require octane boost to avoid preignition.
The first advantage of using heated air is that it can be blended with cold air, increasingly cold as power is required.
The second advantage of using heated intake air is that the throttle can be opened wider, resulting in less load from creating vacuum.

In a perfect world we would have variable displacement engines that always had the same pressure / temp at TDC, as the compression ratio would be constant, and it would run at WOT all the time.

In our world, it isn't practical....... Though Sandia Labs developed such an engine back in the 70's

Instead we throttle engines.

A wonderful development would be variable chamber size........ but it ain't gonna happen I'm afraid

Another good development would be octane boost injection so we had the exact right octane level for any given driving condition. That system exists more or less.

Within reach for you and I is a variable temp induction system that simulates higher compression ratios under low power conditions. A car that is making 35 mpg at 70 mph is burning 2 gpm or 12 pounds per hour, or producing approximately 25 HP at that moment...... that's a tiny fraction of it's potential max net output, probably half or so of the net output available at that particular RPM.

My objective is to achieve the same TDC compression stroke temp as is achieved at WOT, no matter what the throttle position. To that end, the air flows (hot and cold) would be mixed based on power requirements.

So imagine that we have an engine running at 50% throttle, and we add heated air until it is running full throttle to get enough air to maintain it's 25 HP output. The air going in will be much hotter, and less dense, but what will the temp be at TDC? We could manufacture a test rig to find out using a small engine with a temp sensor, and air only feeding it, but it would be quite complicated.............The other thing that can be done is to add heated air until preignition is heard.

I am suspecting that some throttling would be needed along with some heating of the intake air to achieve the ideal result.

This is a project that really needs to be undertaken using a dyno and a scangage. I once had access to a tractor PTO dyno, which could have been hooked up to a vehicle drive shaft without a lot of creative work. A dyno is nothing more than a fixed load, and most of them use pumps.... or in the past they did. A 3" inlet centrifugal pump would make a decent load for a dyno, load being controlled by a simple valve, and the pump mounted on it's rotational axis, with an anti rotation arm attached to it, resting on a scale that measures torque simply by knowing the lever arm length.

I personally believe that many modern diesels could benefit greatly at low power cruise by bypassing the intercoolers and air to air coolers. "Modern" is perhaps not the proper word, as I have my doubts about electronic diesels. Von Bongart's book Diesel Engines published back in the 30's noted that compression ratio, and atomization (droplet size) were both closely tied to fuel efficiency. Droplet size is a function of nozzle size as related to fuel flow. A small injector tip running at max flow is efficient.... I've observed this directly....... it does make a difference. Modern diesels come with larger and large injectors because they are built for max output, NOT max efficiency. Those goals are fundamentally opposed to each other. Turbocharging results in the need for a lower baseline compression ratio, thus then, the turbo is NOT spooled up, the effective compression ratio is lower, as is the efficiency. This at least could be mitigated by increasing induction temp. There is also the issue of mixture...... diesels are mixture sensitive just like gas engines are, but they WILL fire at very lean mixtures. That however does not mean that they are efficient at lean mixtures. Brake specific fuel consumption graphs are often readily available for industrial diesel engines, and reflect this clearly.

........ Talk is cheap they say! I need to experiment a bit in real life, but I hesitate to rely on such subjective figures as MPG.

Howard