[DeTomaso] Ghetto Engineering Part 1

Tomas Gunnarsson guson at home.se
Fri Oct 17 14:46:11 EDT 2008


Which way was the opening of the "sensor" end of the tube pointing when you measured? Direction of travel, sideways, towards the back, up, down?

Tomas

----- Original Message ----- 
From: "Scott Couchman" <scottcouchman at yahoo.com>
To: "Pantera Forum" <detomaso at realbig.com>
Sent: Friday, October 17, 2008 3:12 AM
Subject: [DeTomaso] Ghetto Engineering Part 1


>I decided to try and build on some of the aero work Goran
> has been doing. I bought20’ of 5/16” flexible clear vinyl tubing for $4 from
> Home Depot and fashioned aU-shaped manometer at one end and filled it with
> water. I then used the other end tomap the pressure at different locations on
> the surface of my ’72 Pantera while I droveat near highway speeds.
> 
> With the manometer end of the tubing duct taped to the dash, and the other end
> leadingout the window and duct taped outside at the base of the windshield, I
> headed south onI5 while monitoring the change in the meniscus level in the
> manometer. I decided to trydifferent speeds and measure the pressure at
> different locations along the centerline ofthe car. I started at the base of
> the windshield because I understand that this is ahigh-pressure region. The
> change in the meniscus level confirmed that. There wasn’tmuch change at low
> speed, but the movement was very noticeable as I accelerated intothe flow of
> traffic. I decided that I should repeat the test this time headed north and notsurprisingly got similar results. As I hit 90 in the ‘slow lane’, I passed a
> CaliforniaHighway patrol officer giving a greeting to a Chrysler Pacifica
> driver on the side of thefreeway. I decided to take the next exit and stopped
> in the back parking lot of a HomeDepot to wait out the officer and to move the
> end of the tubing to the top of thewindshield.
> 
> 
> 
> I repeated this test a couple of time, trying to be as
> discrete as possible to avoidattention. Note- it’s difficult to be discrete
> going 90mph in a yellow Pantera in themiddle of the day on the busy 5fwy!
> There was a C6 that was shadowing me and Icouldn’t tell if he was trying to
> figure out what I was driving or what I was doing withthis tubing hanging out
> the window. As I passed the Highway Patrol, the red light cameon……fortunately,
> it was the red light on my gas gauge (at least now I know it stillworks!), so
> I ducked into a gas station before the carburetor agreed with the warninglight
> that the tank was empty.
> 
> 
> 
> DATA – At the based of the windshield, the meniscus moved
> down .5” at 80mph and1” at 90mph. Remember, to convert to pressure, the column
> of water is twice that, or1” at 80 and 2” at 90. This was consistent with what
> I expected. At the top of thewindshield, the meniscus moved UP 1” at 80 and 2”
> at 90! This really surprised me.That’s 2” and 4” of water, or a total of 3”
> and 5” difference between the base and thetop of the windshield! I measured
> the pressure at the rear of the roof, but the realreason I was doing this test
> was to try to find a high pressure location to mount an oilcooler to keep my
> oil below 275F during open road racing.
> 
> 
> 
> CONCLUSIONS – First, a manometer made out of flexible clear
> plastic vinyl tubing isa reasonable approach to measure airflow around a
> Pantera at near highway speed.Second, if you’re planning to feed your engine
> with cool air from the top of thewindshield, I hope you have different data
> than I found. Third, I need to measure airtemperature at the same locations
> because pressure is only part of the equation. Fourth,I need to do more
> pressure mapping, but I think I’ve found a location to mounting an oilcooler.
> Fifth, extrapolating from 90mph to 150mph isn’t practical so I need to do moretesting at higher speeds.
> 
> 
> 
> By the time I finished 4 sets of tests, the freeway was
> starting to slow with afternoon
> commuters, so I decided to head back to the
> garage and find the last bottle of
> MillerLite in the ‘frig and settle in for an
> afternoon nap. I have more work to do, but
> I’ve already found some interesting
> results. But before I do more testing, I need to pull
> the distributor so I can
> get it re-curved this weekend. I’ve got some photos of the test if
> anyone is
> interested. OBTW, if you’re interested in knowing where to mount the oil
> cooler, show up at the May Open Road Race in Ely and I’ll show you!
> 
>      
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