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Is your Dyno lying? This is a MUST read!!!!!!

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viper spray

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Discussion Starter · #1 · (Edited)
I read this in my new Car and Driver mag and had to post the story here. Would a Viper respond to airflow like this car did? Should we re-think how we dyno our cars and how much power they really may have? What about that VIPAIR that elite sells , could it really help at speed? Read this and post your thoughts. http://www.caranddriver.com/article.asp?section_id=4&article_id=8020 (READ BOTH PAGES)
 
nohsreg2000

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#3 ·
Great read....But it does not really explain some of the other phenomena that are occurring. Anything that helps create smooth airflow or reduces the load on the engine will create power. The amount will vary from design to design.

For example; Say you are Dynoing a small block Chevy with a motor driven fan. The difference between a dyno graph with no airflow and putting a fan to blow a 100mph wind will be rather great(I don't know how much I am just pointing out a load situation.) The increased air stream on the fan will reduce engine load quite a bit.
 
viper spray

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Discussion Starter · #4 ·
It just seems crazy that he picked up over 40 RWHP with a big fan blowing 38,000 cubic feet per minute of air at 75 mph down a narrow duct, right into the M5's radiator and intake on the dyno on top of the 37 RWHP picked up with a Home Depot fan.
 
nohsreg2000

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#5 ·
viper spray said:
It just seems crazy that he picked up over 40 RWHP with a big fan blowing 38,000 cubic feet per minute of air at 75 mph down a narrow duct, right into the M5's radiator and intake on the dyno on top of the 37 RWHP picked up with a Home Depot fan.
Click to expand...
In that particular case is makes sense. The computer is set up to manage the car based in real world parameters. An indicated 160MPH with 0 MPH airflow is not very real world. I imagine the computer compensated. Perhaps riching the hell out of the A/F ratio to adjust for what it perceived as insufficient airflow for cooling. Also just the lack of a positive pressure situation (or at least increased pressure) around the air intake can create additional load on the engine and it seems the complex BMW engine management system might have compensated for this as well.

These are shots in the dark but based on the article and what I know about airflow(Thats what I do) it adds up.

The last possibility is Mike Dinan could be pulling a fast one to make up for not making a number.
 
P

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#8 ·
I can see how that works for engines and cars (systems?) whith highly sophisticated engine management systems. BMW is known for measuring and adopting to all kinds of sensors in order to ensure a smooth ride.

Case in point, I managed to get the engine to run differently on my bimmer by putting the gas cap on wrong -the engineer hooked up a computer and explained how the on-board engine management system altered the engine profile to preserve emissions requirements based on my leaking gas cap.

Here is my question: How sophisticaded is the viper engine management system. Does it take into account as much external data as lets say a bimmer engine management system? It would be darn cool if any of the tuners would replicate the experiment on a viper and see if there is a difference.
Heck, it would be even better if it can be replicated on a stock bimmer, since the engine management system is the same it will gain percentage wise just about the same amount of extra HP as Dinan did.
 
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nohsreg2000

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#10 ·
Their is another way of looking at this for understanding. The car is supposed to make the high Hp number. It did not "Find" that extra HP with the fan. It compensated various systems that reduced HP without the fan.
 
John Hennessey

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#11 ·
Some people make the dyno out to be the final and absolute measure of performance. Ever see a bunch of dyno weenies in a parking lot comparing dyno sheets? The dyno is just another tool or measuring device, like a wideband, etc. It is a helpful guide, but its not an absolute as there is no way for a chassis or engine dyno to simulate the dynamics of a car accelerating over a broad range of speed like 0-150 mph or 70-170 mph. The influences of air flow into the air induction and across intercoolers, drag, driveline efficiency, engine load, cooling, etc. are all different on the road or track as compared to sitting still in a dyno cell.

I have seen so many times where a 700 rw hp Viper goes to the track and does not run as fast 600 rw hp Viper.

Bottom line is tha the time slip dont lie. Period.
 
Dr Roof

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#12 ·
John Hennessey said:
Some people make the dyno out to be the final and absolute measure of performance. Ever see a bunch of dyno weenies in a parking lot comparing dyno sheets? The dyno is just another tool or measuring device, like a wideband, etc. It is a helpful guide, but its not an absolute as there is no way for a chassis or engine dyno to simulate the dynamics of a car accelerating over a broad range of speed like 0-150 mph or 70-170 mph. The influences of air flow into the air induction and across intercoolers, drag, driveline efficiency, engine load, cooling, etc. are all different on the road or track as compared to sitting still in a dyno cell.

I have seen so many times where a 700 rw hp Viper goes to the track and does not run as fast 600 rw hp Viper.

Bottom line is tha the time slip dont lie. Period.
Click to expand...

:nod:
 
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Gerald

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#13 ·
If the slip doesn't like how come 1 person can take a the same car and run 11.8 at 128 and the next person with more skill can run 10.8 at 138? The dyno is a more "consistent" power measuring tool than a track (which is skill related)


/images/graemlins/smiles

G
 
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Dr Roof

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#14 ·
Gerald

I think what is meant here is that you take a skilled driver or the same driver on the cars and the DYno Numbers will come to life and sometimes Illuminated beyond the actual figures the Dyno Produces.

I know my car produces much more RWHP than is shown on a dyno when the car is in Motion. otherwise my car would not trap 147-151 on a very consistant basis.

The same is true with many other Forced induction Vipers
 
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viper spray

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Discussion Starter · #15 · (Edited)
It woud be very interesting to do what PAR suggests: "Here is my question: How sophisticated is the viper engine management system. Does it take into account as much external data as lets say a bimmer engine management system? It would be darn cool if any of the tuners would replicate the experiment on a viper and see if there is a difference", but like the article says , that huge fan that they used is a $7,000 fan.
 
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nohsreg2000
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