Date: Sun, 28 Nov 2004 05:31:52 -0600
Reply-To: Al and Sue Brase <albeeee@MCHSI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Al and Sue Brase <albeeee@MCHSI.COM>
Subject: Re: Intake air flow, improvement possible?
In-Reply-To: <001401c4d4d3$fb61dfe0$e10cfea9@9100d>
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Sorry, Gary, I agree very little with your conclusions.
Running up to red line is only half the product. What torque it makes at
any given rpm is what determines the power.
(HP = work/unit of time) In other words an engine making 100 ft-lbs of
torque at 6000 rpm is making twice as much horsepower as an engine
making 100 ft-lbs of torque at 3000 rpm. It is doing the same work in
half the time. Also, one could attach the 6000 rpm output to a 2/1
transmission and then have 200 ft-lbs of torque at 3000 rpm.
Horsepower is everything, at least when it comes to acceleration and top
speed. Top speed is a bit irrelevant. A stock engine will produce
enough top speed to satisfy most of us, somewhere around 88-92 mph.
Where a horsepower increase is important is for passing and possibly for
towing.
Long term, continuous use of the increased horsepower WILL reduce engine
life.
Actually, fuel consumption MIGHT improve slightly due to more accurate
mixture control.
The maker of this product says it will increase manifold pressure 1 psi.
some turbos and superchargers make 7 to 10 psi increases. This probably
would be enough to feel, but decreased 50-70 times are what are really
important. There is some reason why most every manufacturer uses
hot-wire systems. Why would they, if 1974 technology was just fine?
Btw, any increase in air flow through the engine should result in
increased horsepower. It will not result in decreased fuel consumption.
The only simple thing that will decrease the fuel consumption would be
to raise the compression ratio.
Al Brase
Gary Lee, Vanagon Racks wrote:
> The recent discussion about possible improvements to the intake air flow
> chain in the vanagon got me to thinking.
> Here are my theoretical assumptions:
>
> 1. The volume of air required by a gasoline engine is directly
> proportional
> to RPM.
> The higher the RPM, the more air needed. A gasoline engine needs to
> maintain a relatively constant air fuel ratio.
>
> 2. The stock air filter - throttle body - intake manifold system is
> capable
> of flowing enough air for the stock engine up to redline.
>
> So, increasing the volume of air the intake tract can flow will have no
> affect on power or fuel economy (in a stock unmodified engine).
>
> If you drive your van at less than redline, increasing the size of the
> throttle body and/or increasing the size of the intake tract will have no
> affect
> on performance. Certainly everyday city driving is far below redline,
> well
> within the capacity of the stock AFM and air filter. Even if the stock
> system is
> restrictive, there should be lots of headroom for normal driving with a
> stock engine.
>
> If you do not accept the above, then some related questions are:
> - just how bad is the stock system?
> - do things like K/N air filters really honestly offer more hp and better
> mileage?
>
> Corrections and rebuttals welcome.
>
> Gary Lee
> Calgary
>
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