Dyno Results!!!!

[todd]

Here is the final "street tune" of the engine from Keith Craft. The enigine max hp was 640 hp@6200 rpm and max torque was 624@4900 rpm. Keith Craft tuned it down a little to make it a little more streetable. This dyno sheet is the 43 run on the engine, final street tune. This is not the max but what the engine was tuned in.

Big thanks go out to Drew at Keith Craft Motorsports in Plano Texas. Thanks again.

Todd

[jayscobras]

POSTED ON A PRIOR THREAD

JAY

[BMK]

Hi Jay,

Hope all is going well there in Texas.



I have been talking with Wayne 'wtcobra' and he has been hit hard with cold weather there in Indiana.

Different here. See forum "Australia club". Weather been good and there are a few good days ahead.

Some great photos of cars at the Cobra day on the Australian Forum - Threads.

Took a day or two to get over that moonshine that George and the boys were giving me at the 'Run N Gun'



Need to look into that recipe.



If you get a chance drop a Post on here on the Australian Forum.

Did not get that jacket patch. Have sent you a note.

Cheers

Bernie

Bernie Knight

Mt. Gambier South Australia
Home of "Weekend at Bernie's #2" - march 13th and 14th 2004

[Karl Muller]

is that HP at the clutch or the rear wheels?

[REDSC400]

Hi Todd:
Those are impressive numbers.

One thing that strikes me, is the low Volumetric Efficiency VE% numbers? You may want to query your tuner/builder as to why those numbers are so low.

VE = (Actual CFM / Theoretical CFM) * 100

Generally, you can expect a so called normal run of the mill engine (stock) to give 75% at normal maximum speed and about 80% at max torque RPM.

A stock high performance engine should have VE Numbers of 80% at Maximum speed and 85% at max torque.

A blueprinted or racing engine usually achieves 90% at max speed and 95%+ at max torque.

Often, reasons for low VE numbers are found in the air pump aspect of the engine. ie: constricted exhaust or air filtration that starves the engine of potential air.

You may be able to even get more out of this engine! That is pretty impressive.

[coyled]

The hp and torque seem about right and this motor will move a cobra really well. I too am confused by the VE#. I would think it would be higher. The max cfm at 475 seems low. The a/f number on mine was more like 13 to 1. Lots of power and lots of fun. Scott

[Mr.Fixit]

The VE and A/F and SCFM seem off.

what kind of motor?
is it a 468 cid?
measured at the rear wheels or flywheel?

[Steve R]

Fixit,
Could you please explain Brake Specific Fuel Consumtion?

We must be missing something about the A/F ratio. That seems real fat to me. What say you?
Steve.

[REDSC400]

Brake Specific Fule Consumption (BFSC) is a DYNO metric to describe fuel consumption rate. An engine on a dyno is stationary and the fule consumption cannot be measured in miles per gallon. Many dynos are equipped with a fuel flow meter and this meter shows you the fuel flow in pounds per hour. The rate at any given RPM divided by the Brake Horsepower at that same RPM is called the BSFC. The lower the number the less fuel used.

BSFC = Fuel Pound per Hour/ Brake Horsepower

[Steve R]

Art,
Thanks. Do you have any comments about the A/F ratio? I thought about 13:1 was O.K. Do they express it differently on a dyno sheet?

[REDSC400]

Steve R:
There is an old axiom that "You cannot burn gasoline without adding AIR to it". Companies like Holley make a great living on that need....

It is easy to deliver gasoline, it is the AIR that is the difficult part of the equation. At 12.5:1 (AIR to FUEL) (A/F) ratio you are very certain to have enough fuel to match up with every exisiting oxygen molecule.

To make one horsepower per hour at 12.5:1, you need 6.25 pounds of air (12.5 x .5 = 6.25) (the .5 comes from the typical standard that it takes .5 pounds of fuel to produce one horsepower in the "standard internal combustion engine" Translated out a 400 HP engine running at the RPM to generate 400 HP would then consume 200 pounds of fuel per hour)

You can lean down the A/F ratios to 14:1 or 15:1 at cruise speeds and 14:1 to 17:1 at idle with the variance being the engine and ignition variables.

What I have seen, is that on ANY dyno, if you manually vary the A/F at any given operating speed, you will see that the BHP goes up as you richen up the mix and then will fall off when the mixture gets too rich. Running rich is for power, and durability to save valves and pistons. Running lean is for economy.

I hear that most EPA style tuned engines are in the 14.7:1 A/F ratio range.

For more data on this subject, I would recomend the fine booklet, Super Tuning Holley Carburetors by Alex Walordy. This is a great great resouce. Also the book, Desk Top Dynos by Larry Atherton. and lastly, How to Build and Tune Holley Carburetors by Des Hammill. These are all available on Amazon.com or often on ebay. The Desktop Dyno book comes with a computer program to do modeling. It is cool.

I smell that Turkey Cookin"

Wonder what the A/F ratio is in the OVEN.... Dope!

[Keithc8]

The air fuel ratio is of because our air flow hat is of. I talked with SuperFlow about this and had to send the hat in to them. We will normaly have a 110 VE on these engines and move about 850cfm's, this how I knew it was of. This hat is electronically calibrated and then these numbers have to be installed to your calibration screen on the dyno. This effects the air fuel ratio which should be around 13 to 1. The horsepower numbers are right as well as the fuel used and brake specefic fuel consumption numbers. We will have the hat back next week from SuperFlow. Thanks

[gsharapa]

Numbers are impressive like mine were 638.9 HP but wait till you get it in the Cobra and take it for a blast!!!!!!!!!!!!!!

Keith builds an awesome power plant and the only thing you need to be concerned about is putting that pedal to the metal and flying off the road....................WOW what a ride!!!!!

[Steve R]

Keith C,
Thanks for straightening that out. I was a little confused. It was something like 12.7:1 or there abouts that was the magic
number in A&P school.
Steve