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Discussion Starter · #1 ·
After a year of running the 55

After a year of running the 550 with a Stebro x-pipe and Quicksilver mufflers, I'm now the (sole prototype) driver of the only 550 in the world with a tuned exhaust system (from Hyper-flow).
In early 2007, I'll have an article in PILOTA magazine, describing the process of engineering and test-fitting prototypes and the definate results.

Forget the "sound" improvement (and forget what a muffler- any muffler- can "do" for performance, since the muffler is at the END of the harmonic chain and thus is nothing more than the bell of a musical instrument). This car now PERFORMS like a Ferrari with a 1970's era F-1 engine with tie rods so light you could mail them in an envelope!

The car now pulls tree stumps to 7,000 rpm and is also now well over 500 hp in the mid-range! I'm amazed by the difference! The next step: Cam timing (by Scuderia Rampante in Boulder, CO, with data selected from a GTO250 engine that ran at Sebring, Nurburgring and Daytona). I've got a choice between more hp or more torque; and am leaning to more hp from 3500-5000 rpm, since the power band flattens out anyway at the top end by sheer physics.

Discussion Starter · #2 ·
If you are tracking the car, h

If you are tracking the car, horsepower sells cars, but torque wins races. Typical road race tracks are about 70% accelerating, 20% cornering, 10% braking. I would go with torque, as "grunt" off the corners will get you a faster top speed at the end of most straights. And better launchs off traffic signals

Discussion Starter · #3 ·
Thanks for writing, Bob.

Thanks for writing, Bob.
After two seasons of tracking the 550 (four events that averaged about $1000/per in maintenance, I'm now just a simple man from Wyoming, interested in enough torque to pull from 65-120 on some wonderful wide-open Wyoming road. I'm remiss in knowing the relationship between torque, hp and rpm. What I feel the power curve is now lacking isn't at the bottom end, it's in the mid-range (3rd gear) as I'm (for example) onto the interstate, going from 3rd-to-4th at about 100 mph and wanting the power to extend. Maybe that's torque I'm looking for. But my rpm at that point (after shifting 3-4th in the 5-6000's) is up in the 3000's. Dave Helms' cam data can be tuned for hp (GTO250 at Daytona or Sebring) or torque (Nurburgring).
I'll do some more reading on torque/hp/rpm
Cheers John

Discussion Starter · #4 ·
John, Good writeup from the

John, Good writeup from the web about torque:
Force, Work and Time
If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on.
In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time.

Awhile back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower.

Everybody else said OK. :)

For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms which define a *twisting* force, such as foot pounds of torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum.

Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.

Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidently, we have done 6.2832 foot pounds of work.

OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement:

Horsepower = torque x rpm divided by 5252

This is not a debatable item. It's the way it's done. Period.
Now, your job is to match the max torque value to the rpm range you want use, for the type of driving you want the car to perform at. For the realworld, the "flattest" torque curve at the range of rpm and gears used, will be the fastest.

Discussion Starter · #6 ·
Hi Mitch, whats new? This si

Hi Mitch, whats new? This site been a little quiet lately. You are correct about the old bib overall farmer's quote. In the old days, we could beat a Cobra into a corner, but the V-8 torque off the corners was awesome.
We need to talk John into tuning for torque in the rpm range he wants to use. We might want to confuse him with gear and rpm charts and rate of acceleration for each gear. I know you can post some great info for him to ponder. Your thoughts,,,,

Discussion Starter · #8 ·
Hi Bob; Ford did the same with

Hi Bob; Ford did the same with Ferrari at LeMans with the GT40s.

A great big engine (displacement wise) with a desending TQ curve has a big accessible power band almost flat amount of HP over 1/3rd of the RPM band. A high strung littel engine with the same peak HP may have a nice flat TQ curve, but the area under the HP curve will be found to be deficient (relative to the GBE). This is the "No replacement for displacement" argument with is, in effect, a statement about TQ.

However, even with all the good things going for them wrt TQ; a small high strung engine with a nice flat TQ curve does have one handling advantage over a GBE. That is, while the car is on the flat part of the TQ curve, the weight transfer to the rear under acceleration is constant over the RPM band where the TQ curve is flat. This makes these cars slightly more easy to balance atthe edge of traction through long sweeping turns.

Discussion Starter · #9 ·
Bob wrote "I'm now the

Bob wrote "I'm now the (sole prototype) driver of the only 550 in the world with a tuned exhaust system (from Hyper-flow). "

Did hyper-flow supply you with headers, cats and muffler? Also, what is the current status of this project?

Discussion Starter · #11 ·
Tony, the status of the projec

Tony, the status of the project is completed. I've tested and evaluated both the prototype 550 cats and x-pipe and both products are now available from Hyper-flow. I understand that Dave Helms in Boulder (who did the fit-check, installation and production feedback) on the project has now been contacted by muffler engineers who've left the Tubi company. I've also been approached by a dealer of X-OST mufflers, to test those units.

Hyper-flow provided cats and x-pipe. The OEM headers were kept in place.
No dyno, as it's a waste of time on the 550. This is because the hood scoop alone provides dozens of horsepower on the intake side (power which is lost in a hot room of stagnant air being sucked into the engine.
I believe I understand that a 355 with Hyperflow cats was tested and there was a 30somehp increase in the midrange and a nominal 5-10hp increase on the top end.
I definately feel like I'm driving a car that weighs 500-800 pounds lighter; with a torque curve that is flat all the way to 7000 rpm

Discussion Starter · #12 ·
Thanks Wyo550,

What did the

Thanks Wyo550,

What did the project entail? It sounds like you put them on, drove around and said "Yup, they fit, sound and feel great"

I am wondering if there was more to it than that.

Discussion Starter · #13 ·
Yea, the test and evaluation r

Yea, the test and evaluation ran all the way from the fabrication of the prototypes by Hyper-flow, to confirmation of installation fit by Scuderia Rampante. Finally, after the above, the mechanic and driver both ran the car in a focused T&E mode- against known performance benchmarks like rpm, torque curve and throttle response, etc- to determine actual performance improvements, sound characteristics, etc.

I'm now writing an article for PILOTA with all the details. The nest phase is to do cam timing with GTO250 data from a race model that ran at the Nurburgring. I know what power band I want enhanced, from my driving T&E and we're tuning the torque curve for that power band.
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