Re: VIPAIR™ Dyno Results on 99 RT 16 RWHP!!
I'll jump back in on this one, why I don't know because I don't have any vested interest in Vipair. I am just trying to help those interested understand the ram air/cold air theory.
RussM, thanks for doing some testing! I did some math on this in an earlier post as my motor is out of the car so no real world testing for me right now. I just think there are a few issues with the test method I would like to discuss. You tested pressure with a "normal pressure guage vacuum" which I doubt had the accuracy to show the mathematically predicted <1psi pressure increase. Also, you had a stock box with the rain baffle and drains that could have bled off any pressure. On the dyno, you compared the vipair with the hood closed compared to a stock box with the hood open - not allowing ingestion of the hot underhood air. Then, after lunch, you did some other runs just to show the ability to manipulate dyno numbers a fair degree. Then you closed the hood and got no increase from earlier in the day on one final pull. Did underhood temperatures have the ability to reach those under normal operation? A fan is a good idea but not even close to real operation.
Anyway, I don't think the dyno is where anyone is going to see this modification show noticeable results. Here's why:
1) Any effect from "ram air" will not be realized because air is not flowing over the car at a high rate of speed (earlier the math was shown to have minimal pressure, <1 psi, differential below 100 mph or so), a fan just will not do it,
2)From what I have seen posted (and RussM showed this very clearly), people are very careful to have their cars fairly cold when dynoing. Most people have posted that if you do a bunch of runs in a row, the numbers drop. Therefore, the tester would really need to get the underhood temperatures hot before the back-to-back dyno runs to test the airbox for the cold air theory,
3)On a dyno, there is no pressure differential inside versus outside the hood. When a Viper is moving at a high rate of speed, the under hood pressure is higher than the pressure on the hood (if someone doesn't believe me, take the mounting bolts off of your hood and drive down the street, see if at speed it stays on - greater pressure outside - or flies off - greater pressure under the hood). This higher under hood pressure would tend to drive air into the sides of the stock airbox bringing in hotter air than outside the car. If anyone thinks the under hood air is the same temp as outside, ask yourself where that air comes from. Through the radiator. If there is no increase in heat after the air has passed through the radiator, radiators don't work. That sounds like grounds for another thousand post thread - sorry.
Therefore, I'll summarize my thoughts and go away. I think the increase gained by ram air is real, but very minimal and only then at very fast race track speeds. I think leaving the NACA duct open with the vipair is the wrong thing to do. I think the cold air aspect will make noticeable power under the proper conditions. These conditions are very difficult to test properly - a static dyno is not the place. However, I do question why every fully developed racecar (factory cars, etc) all go to great lengths to get cold air into the airbox if this theory doesn't work. FYI, every 10 degrees change in intake air temperature (using 77 degrees as a baseline) is a 1% change in HP!
Here is a HP calculator for air pressure, temperature, humidity:
http://www.wheels-of-fortune-autoclub.com/relhumhpcalc.html
RussM - thanks again for taking the time and money to go out and independently test a product and post the results.
Vipah, et al - Believe what you want to believe as I will. I will now do my part to let this die and not post on this thread again.
Regards,
