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Old 06-24-2009, 08:45 AM   #31 (permalink)
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Intake manifold design does have a larger effect on torque, but intake diameter and length can still play a significant role. Check out the article below.

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Old 06-24-2009, 08:59 AM   #32 (permalink)
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Quote:
Originally Posted by max_frontal_area View Post
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!
You suggest that lower RPM translates to easier to fill cylinders. This is true to a point. Modern cars have over laping cams. The intake valve remains open until slightly after the intake stroke finishes. At the right RPM, which translates to the torque peak of the engine, the air in the intake tract has a lot of momentum as it is pulled into the engine, and continues to fill the cylinder as the piston comes back up for the compression stroke.

In engine terms, we refer to how 'full' we get the cylinders as 'volumetric efficiency'. A volumetric efficiency of 100% would mean that you were able to fill the cylinder completely with ambient air pressure. Some cars are able to achieve slightly higher then 100% volumetric efficiency without a supercharger!

As for using a 4 banger as a v8. You lost me. Unless you are suggesting turning your car into a 2 stroke? In which case, you will enjoy increased power at the expense of engine longevity, fuel economy, and emissions. I doubt anyone could make a 2 stroke engine pass modern emissions requirements.

Heating the fuel works great. If your using veggie oil as fuel anyways. Gasoline dosen't have any difficulty vaporizing. Even regular diesel does fine. I've never seen any indication that heating fuel has any significant impact on fuel consumption with good fuel. An otto cycle gasoline motor made of steel is limited to about 37% efficiency. So i doubt smokey got 100 MPG on a car that the EPA rated at 25 without aeromodding the crap out of it.
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Old 06-24-2009, 09:07 AM   #33 (permalink)
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Thanks, That is very interesting. I learned something new. I would guess that this was the result of the reduced restrictions in the fuel injection compared to the old carbureters. I did note that the power gains came mostly over about 2400 RPM and I assume were at large throttle openings. Below 2400, where most driving is done, there was a reduction in power.
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Old 06-24-2009, 09:11 AM   #34 (permalink)
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Originally Posted by micondie View Post
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.
I had to design an intake system for a formula SAE competition car and the intake primary runner length, and diameter are the most significant parameters, So long as the rest of your intake doesn't have any major restrictions. The intake low pressure pules are generated at the valve, and end up reflecting off the end of the open intake runner. At the right frequency a high pressure ridge is sitting at the valve as it opens, and presto! More torque.

If the intake runner is to large (diameter), it dosen't build any momentum, and volumetric efficiency is low until a higher RPM. If the intake runner is short, this also favors a higher RPM set point. Ideally, you design your cam, and your intake runners to give you a broad range of favorable operating conditions.

Back on to the topic at hand, the warm-air intake. It's something i'd love to try, but I lack the intestinal fortitude to try it! My intake air temp is always close to ambient.
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Old 11-25-2009, 01:51 AM   #35 (permalink)
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Originally Posted by LeanBurninating View Post
flows easier
you could save some weight as well by switching out that piece of exhaust
pipe and substituting it with a drinking straw
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Old 11-26-2009, 02:48 AM   #36 (permalink)
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Quote:
Originally Posted by stevey_frac View Post
You suggest that lower RPM translates to easier to fill cylinders. This is true to a point. Modern cars have over laping cams. The intake valve remains open until slightly after the intake stroke finishes. At the right RPM, which translates to the torque peak of the engine, the air in the intake tract has a lot of momentum as it is pulled into the engine, and continues to fill the cylinder as the piston comes back up for the compression stroke.

In engine terms, we refer to how 'full' we get the cylinders as 'volumetric efficiency'. A volumetric efficiency of 100% would mean that you were able to fill the cylinder completely with ambient air pressure. Some cars are able to achieve slightly higher then 100% volumetric efficiency without a supercharger!

As for using a 4 banger as a v8. You lost me. Unless you are suggesting turning your car into a 2 stroke? In which case, you will enjoy increased power at the expense of engine longevity, fuel economy, and emissions. I doubt anyone could make a 2 stroke engine pass modern emissions requirements.

Heating the fuel works great. If your using veggie oil as fuel anyways. Gasoline dosen't have any difficulty vaporizing. Even regular diesel does fine. I've never seen any indication that heating fuel has any significant impact on fuel consumption with good fuel. An otto cycle gasoline motor made of steel is limited to about 37% efficiency. So i doubt smokey got 100 MPG on a car that the EPA rated at 25 without aeromodding the crap out of it.
'volumetric efficiency' is my user name on some other forums - i am well aware of the term and its implications.

originally written by me:
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?!

allow me to translate. a large 4 cylinder coupled to an carefully designed efficient turobocharger system (not just the blower but intercooler, a misting system for keeping a heat soaked IC cool, and perhaps even water injection)
will provide you with fantastic economy if driven responsibly but can also
pull like a big engine. as long as you dont go cheap on turbo sizing like most manufacturers do. visit europe if you have the means. lots o lil highstrung engines with turbos. halvofem are diesels.
that explains the "fourbanger as a V8" now i will move on to "forcing it to perform as a twin".
now you take that same fourbanger and instead of feeding it the most and coolest air then splash in fuel to get your stoicio on - or even a lil less for lean burn because you have gone to great lenghts to feed it COOL air you have a margin or error in melting your engine. the result, your engine has to perfom fewer cycles. your have great economy, possibly awesome, and an engine that is maximized (in terms of efficiency and power combined)
add a spritz of water and you can take lean burn to new heights.
eat your heart out honda!
derailed myself again back to my point.
that same 4 be it a V, L, boxer or what have you, now you do the exact opposite of above. now you cleverly cheat it out of the air molecules that it wants so badly to do its job of pulling you down the road. add insult to injury to do all this at the point of risking hurting your engine - in the name of airflow. Heil!

Smokey Yunick, holder of various patents - author of a few books.
yes indeed and in an 80's chevy!!, and no, by heating his fuel only (gasoline)
he provided one of very few brains during the good ol days of good ol boy racing.

when you get your IT preheating worked out be sure to send this guy an email and fill him in on why he failed reaching his 300 MPH goal.
it is the all red firebird, i suggest you do some research on it to see what you can do when you chill your intake air.
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Old 11-26-2009, 02:52 AM   #37 (permalink)
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here is the link:

Banks Power | Twin-Turbo Revival: Part 1
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Old 11-26-2009, 10:43 PM   #38 (permalink)
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I have to mention that if your engine is functioning, and not malfunctioning, you're not depriving it of airflow. Keep in mind that most engines are already running air deficient compared to their max VE. By using hotter air, you're only allowing a higher throttle opening without making unnecessary power, reducing pumping losses. You're not putting your engine in danger at all, other than from detonation, and if your engine didn't like the warmer air, you'd be getting worse mileage as it dumped fuel to keep detonation at bay, or retarded the timing for the same reason.

None of the reasons in your post, although they were posted with conviction, as it appears, weren't "the whole story" as it were.

Lots of cars could benefit from a smaller engine with a turbo, because you're not really efficient at low throttle angles, and an engine that's small enough to be truly efficient at cruise conditions isn't going to be able to accelerate quickly enough to really be effective in the real world. Add a turbo and a bit more fuel with detonation deterrents to that smaller "efficient cruise" engine, and you've got a great combo.

Hm. I didn't go to engineering school, and automakers still haven't really figured this out.
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Old 11-27-2009, 02:17 AM   #39 (permalink)
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Quote:
Originally Posted by Christ View Post
I have to mention that if your engine is functioning, and not malfunctioning, you're not depriving it of airflow. Keep in mind that most engines are already running air deficient compared to their max VE. By using hotter air, you're only allowing a higher throttle opening without making unnecessary power, reducing pumping losses. You're not putting your engine in danger at all, other than from detonation, and if your engine didn't like the warmer air, you'd be getting worse mileage as it dumped fuel to keep detonation at bay, or retarded the timing for the same reason.
christ. have you ever tried/had to attempt to fix or even seen the internals of an engine that expired from detonation? google up some images
from street engines. then look at racing. high boost turbos, AA blowers, nitrous coming on without the additional fuel needed appropriately responding.
have you ever seen sparkplugs that look as if they had been made by alcoa?

"You're not putting your engine in danger at all, other than from detonation, and if your engine didn't like the warmer air, you'd be getting worse mileage as it dumped fuel to keep detonation at bay, or retarded the timing for the same reason."

you are obviously talking about an FE engine.
modern FE engines are equipped with dual band knock sensors which will knock back timing (i cant believe i said that do that long enough and your
exhaust manifolds will begin to glow and with the *concept* of wanting to flow preheated air through them there is even less capacity for cooling.
if that/those manifolds are made of aluminun they will be at risk of melting. now imagine having a dummy car with only a carburetor and mechanical distributor and no way to sense less than ideal combustion and the only way for you to find out through the coolant gauge, steam emitting from the hood.

there are ppl on here that dont know how to bump-start a coasting car
and they are being counseled to draw their intake air out from under the
exhaust manifold shield? UMBFK!

Quote:
None of the reasons in your post, although they were posted with conviction, as it appears, weren't "the whole story" as it were.
the story from my contingent is complete.
now i would like to hear yours.
please dont repeat: "higher throttle opening without making unnecessary power, reducing pumping losses" as i have read it many times. it is a simple
concept, not difficult to understand- thin air is favored when flowing around
objects, tight radii, sharp valves and seats, throttle plates and even carburetor internals found in older vehicles.
the concept i cannot warm up to no matter how hard i try,
is how an engine that is ingesting fewer air molecules can produce more power per cycle than the same engine being fed more.

Quote:
ots of cars could benefit from a smaller engine with a turbo, because you're not really efficient at low throttle angles, and an engine that's small enough to be truly efficient at cruise conditions isn't going to be able to accelerate quickly enough to really be effective in the real world.
Add a turbo and a bit more fuel with detonation deterrents to that smaller "efficient cruise" engine, and you've got a great combo.
Quote:
Hm. I didn't go to engineering school, and automakers still haven't really figured this out.
"an engine that's small enough to be truly efficient at cruise conditions isn't going to be able to accelerate quickly enough to really be effective in the real world"

sequential turbocharging, electrically assisted turbos, variable valves, momentary ultra lean burn, and most recently VWs upercharger/turbocharger technology have most been implemented in OE situations, as well as availability for the aftermarket
(except for VWs s/t technology)
once again i would encourage anyone with the means to visit Europe.
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Old 11-27-2009, 02:30 AM   #40 (permalink)
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Yep, seen plenty of engines that "expired" from detonation.

Why are you talking about racing engines on a forum dedicated to fuel efficiency? I'm not really into humoring it, but noone has ever said (to my recollection) that you get more power per cycle with warmer air. The reduced pumping losses make the engine more EFFICIENT, not more powerful. Reduced pumping losses, to an extent, also account for a large percentage of the power lost due to the thinner air taken in.

So you're out for maximum power in any situation? Try tuning for WOT. Sure, at WOT, colder air is much better for making power (not always, but yeah...), but during the normal drive cycle, how many times are you using the engine's full potential? I mean, honestly - do you rev your gasser to 6k and shift from every red light? If you do, methinks you're on the wrong forum, bud.

The idea is a breakdown of efficiency per volume. Since we all know it takes power to make power, and power is always lost in the conversion, and it always takes the same amount of power to do the same amount of work, the only real variable is the amount of energy that is lost converting the source to the motive force, which are frictional and pumping losses (among others). The idea is to use what you have more efficiently, not create more of something you already have an excess of.

The most efficient setup would leave the operator able to operate at WOT and maintain a steady speed/power output. That would be a diesel engine, in most cases, although throttle-less gas engines are apparently also in production now.

In the case of gassers, there is always the option to make a variable intake system, and it's not even that difficult. The average DIY'er can do it with a few hours' labor and some salvage parts. When this is the case, the variable intake temp can lead to the availability of excess power as well as higher efficiency, simply by changing the intake flow temperature to suit your needs.

So again, what's so hard to understand about using warmer air? I'm afraid I don't see where the cold air argument is relevant to our goals here at EcoModder?

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