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Old 06-22-2009, 01:23 PM   #21 (permalink)
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I screwed up, by a factor of 2. A 2 litre engine at 2000 rpm will try and move 2000 literes per minute, not 1000 litres. So you are looking at 4 crank hp for a heater to affect that airflow by 50C degrees.

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Old 06-22-2009, 01:27 PM   #22 (permalink)
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ok ok ok ok.

You make a good argument, although you assume it will be run continuously, and you do not account for the decreased amount of time spent out of closed loop on cold start, as well as time spent in and out of lean burn.

It also happens that using exhaust heat requires the length of the intake tract outside of the tb to almost double. Isnt that a considerable amount of restriction?
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Old 06-22-2009, 01:30 PM   #23 (permalink)
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Not if you use a larger diameter pipe.

Also, longer intake pipes usually increase low rpm torque, which is also good for mileage. So, you get a win win.
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Old 06-22-2009, 01:32 PM   #24 (permalink)
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True, but at some point you have to neck down the pipe to the size of the throttle body. And from the different intake designs I have been trying, I believe any neck down near the throttle body makes too much turbulence and has a negative effect.
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Old 06-22-2009, 02:09 PM   #25 (permalink)
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Well, yes, you want to neck down far before the throttle body. You want a smaller pipe connected to the throttle body for increased low rpm torque, and you want to adjust its length to play with the torque a bit too. But, before that, just use a large pipe. I don't see any problems with using aluminum dryer ducting like others have.
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Old 06-22-2009, 02:28 PM   #26 (permalink)
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Quote:
Originally Posted by LeanBurninating View Post
... although you assume it will be run continuously...
I did no such thing, sheesh. If you want to run the thing it will cost you 4hp while it is running, is that better?

Quote:
Originally Posted by LeanBurninating View Post
and you do not account for the decreased amount of time spent out of closed loop on cold start, as well as time spent in and out of lean burn.
I suppose if you want to argue that doing a long smokey burnout coming out of your driveway also shortens "out of closed loop" time, for a net efficiency gain then I would like to see that bit of figuring too

Seriously, 4hp is a huge deficit to overcome in efficiency terms.
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Old 06-22-2009, 03:28 PM   #27 (permalink)
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What was wrong with collecting air from around the exhaust manifold?
http://ecomodder.com/forum/showthrea...html#post75421
that is how VW has been doing since the beginning of time...

sadly most of us have been removing them from our cars... they either have rusted out or have broken.... I'm one of the few trying to find the parts to re-install it into my car LOL
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Old 06-22-2009, 04:15 PM   #28 (permalink)
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Your new intake doesn't really pose any less restriction than the OEM one did, as long as you're operating at low-throttle angles and less than 3000 RPM.

If you want to test that, find the max flow of the old OEM intake system with the most restrictive filter on the market. (This will give you a better chance of being right).

Then, make a graph which compares actual airflow of the engine (assuming 100% efficiency) with engine speed and throttle angle (3d graphing).

And find the plot points that line up with the OEM filter/intake's flow capacity.
Now, test the "new" intake that you've made. I bet you'll find that they pretty much align on the same plots until you get over 70% throttle, or over 3000 RPM.

You can build a simple box around your exhaust manifold using the OEM heat shields that will pipe hot air over to the filter without fully enclosing it. If you want the filter at the end of the intake pipe, the filter is normally the place with the greatest turbulence in the intake tract, not counting the throttle plate and places in the intake manifold/plenum, so if you're going to step down, that's the place to do it.

Any bend in your intake tract should (be larger diameter than the straight sections) allow for expansion due to pressure drop on deceleration of flow, while keeping flow attached at the outer walls of the intake piping for the best torque curve available from the design choice.

If you're using 4HP on a 30% duty cycle (You're using the heater 30% of the time and using residual heat the other 70%) and 10 HP to move your car at a steady speed, you're now using an average of 10*1+(4*(3/10)))/2 to maintain your speed and current intake temp.

The formula works out to 11.2 HP.

What this means is that you're using 10+ percent more HP now to maintain that speed and intake temp than you would be using if you didn't have the heater in the intake tract.

This means that you have to overcome another 1.2 HP loss before you make up for pumping losses. The extra load on the engine produces (marginally) more heat in the exhaust, which again is just wasted energy.

This isn't taking into account the closed loop operation or extra time spent in lean burn mode, this is actually assuming a basic engine driven at a given speed for a given output.

The formulae to convert units to account for the potential of leanburn operation and closed vs open loop mode would probably just make us all annoyed.
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Old 06-24-2009, 06:06 AM   #29 (permalink)
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Quote:
Originally Posted by stevey_frac View Post
Hot air does two things: It lowers the density of air, meaning you have to have your throttle more open to to get the same mass of air, which reduces pumping losses.

It also increases the temperatures of the air going in. Now i know that's obvious, but it's important. Most thermodynamic cycles improve efficiency at higher temperatures.
the more air molecules your induction sys can pump into your filling cylinders
the more power you will make per cycle. you can do so by augmenting airflow
with an optimized air intake tract, ram air or some kind of supercharging. or by chilling your intake air. more air molecules even cooler ones than ambient will be compressed and heated during the compression stroke in a gasser but more pronounced in a autoignition cycle. hotter air burns more readily as rudolf diesel found out almost 100 years ago. that in turn allows you to make more power with fewer rpms, think artificially turning a 4 cyl into v8!
lower rpms --> easier to fill cylinders, and empty them reduced reciprocating and parasitic forces, less frictional related heating (on moving/rubbing sliding parts) additional time for more complete burn... i can keep going.

why not utilize a fourbanger as a V8 and enjoy more power, economy and longevity instead of crippling it and forcing it to perform as a twin?!

heat your fuel like smokey did. he got an 80's chevy to give him 100 mpg?
just be careful if gas is your choice of fuel!
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Old 06-24-2009, 09:38 AM   #30 (permalink)
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intake tuning

Quote:
Originally Posted by Daox View Post
Well, yes, you want to neck down far before the throttle body. You want a smaller pipe connected to the throttle body for increased low rpm torque, and you want to adjust its length to play with the torque a bit too. But, before that, just use a large pipe. I don't see any problems with using aluminum dryer ducting like others have.
As an old hot rodder it has always been my understanding the only part of the intake that has much effect on power and torque is the length and diameter between the intake valve and the plenum where all the ports merge. (Has anyone seen the old long ram intake that Chrysler put on their performance cars in the mid 60's. They had very long individual ports that crossed the motor and joined in plenums over each rocker cover where the carbureters were mounted) That length could be altered on a motor with a two piece intake by putting a spacer between them. The distance from the plenum to the throttle body might have a very small effect. Beyond that point your only goal is to reduce restrictions to maximize air flow. I don't think that putting some baffles around the intake manifolds to direct warm air to the air cleaner would increase air flow restrictions because the surface area of the manifolds and therefore ths size of the baffles would be much larger than the area of your air cleaner intake.
I am curious if anyone has taken air flow reading comparisons of the air flow restrictions of different size throttle bodys at low lthrottle openings?

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