Intake upgrade and dyno results
10-21-2011, 10:48 AM
#46
Race Director
Data was from traqmate data take on the same car with and without the ram air. Car was a road america and speed traces were viewed. Not perfectly clean, but does show lots of promise. Enough that it is worth a shot to try it out. It was also determined with two cars with the same dyno hp and compring in car video and traqmate speed traces. More confounding here, but all evidence support some marignal gain. Just barely noticealbe on a race track.
10-21-2011, 03:24 PM
#47
Rennlist Member
Just found this - here is a cut & paste from the post on 944spec.org. I was the "test case"
Ram air works. We saw this some at Nationals with Dave Dirks setup. Based on this, I tested this at Road America, a 4 mile track that puts us in 5th gear 3 times a lap, with speeds up around 120 MPH. To optimize the effect I ran a 4" duct from a high pressure area (left fog light), directly to the AFM. For the test, only a window screen was used for a filter, and compared it to my baseline cold air intake (an efficient set up that had dyno'd 137HP/141TQ on a previous car). Leaving the filter on or off that set up made no difference on the dyno. The TM data is fascinating. low speed acceleration is no different, but above about 90 MPH, the curves separate fairly dramaticaly, as the ram air effect starts to show up. It was worth about 4MPH at the end of the straight. Look at the graph below. The green is the ram air. There are 2 laps from my car without ram air (red), and 2 laps from another car with very similar HP, but no ram air. All the "control laps are similar, but the ram air test lap stands out. Conditions were similar throughout.
Larger version here: http://sterlingdoc.smugmug.com/Other...3_2GstHxP-O-LB
Larger version here: http://sterlingdoc.smugmug.com/Other...3_2GstHxP-O-LB
10-21-2011, 03:55 PM
#48
Three Wheelin'
nice.
so not a practical mod for the street then
so not a practical mod for the street then
10-21-2011, 06:25 PM
#49
In reply to J1NX3D;
Not sure how much is obvious so forgive me if I state the obvious.
The graph shows values for Cp (coefficient of Pressure) for point on the car body (typically center line).
The Coefficient of Pressure relates local pressure to free stream or atmospheric pressure dependant on stream velocity / car speed.
The x access points 1 through 50 refer to the vehicle surface locations - Cp value show a negative free stream pressure positive Cp shows positive pressure.
So from the graph you can see there are two areas of positive pressure between points 2 and 9, and 17 through 24 basically the front bumper and wind shield. Note most of the hood is negative pressure.
Maximum pressure is approximately 0.9Cp on the upper and lower edge of the front bumper.
Now Cp =1 equate to Pressure with the square of the velocity so
at 30mph Cp =1 = .013psi over free stream
at 60mph = 0.5psi over free stream.
at 80mph = 1psi
at 100mph = 1.6psi
So not a whole lot of boost to be had.
Not sure how much is obvious so forgive me if I state the obvious.
The graph shows values for Cp (coefficient of Pressure) for point on the car body (typically center line).
The Coefficient of Pressure relates local pressure to free stream or atmospheric pressure dependant on stream velocity / car speed.
The x access points 1 through 50 refer to the vehicle surface locations - Cp value show a negative free stream pressure positive Cp shows positive pressure.
So from the graph you can see there are two areas of positive pressure between points 2 and 9, and 17 through 24 basically the front bumper and wind shield. Note most of the hood is negative pressure.
Maximum pressure is approximately 0.9Cp on the upper and lower edge of the front bumper.
Now Cp =1 equate to Pressure with the square of the velocity so
at 30mph Cp =1 = .013psi over free stream
at 60mph = 0.5psi over free stream.
at 80mph = 1psi
at 100mph = 1.6psi
So not a whole lot of boost to be had.
10-21-2011, 09:54 PM
#50
Rennlist Member
Thanks for the pressure plot & calculations, Andy - very interesting!
Not a lot of boost in turbo terms, but enough to make a difference, especailly because this is very cool air, with no turbo heating it up, and likely little drop off in "boost" at high RPM's. In Spec racing, 10HP is a pretty big deal, and would seem very conceivable. Also, the foglight opening, where we draw the air from, may be a higher pressure area that any place that was measured on the midline of the car. It has the bumper above it, and the ground below, which would seem to create a nice high pressure pocket there. In the midline of the car, this area is the radiator opening = open area, lower pressure.
Speculating 2PSI of cool air over 100MPH would equal significant HP in a race car. On the street, not so much - speeds are less, and risk of water ingestion higher.
Not a lot of boost in turbo terms, but enough to make a difference, especailly because this is very cool air, with no turbo heating it up, and likely little drop off in "boost" at high RPM's. In Spec racing, 10HP is a pretty big deal, and would seem very conceivable. Also, the foglight opening, where we draw the air from, may be a higher pressure area that any place that was measured on the midline of the car. It has the bumper above it, and the ground below, which would seem to create a nice high pressure pocket there. In the midline of the car, this area is the radiator opening = open area, lower pressure.
Speculating 2PSI of cool air over 100MPH would equal significant HP in a race car. On the street, not so much - speeds are less, and risk of water ingestion higher.
Last edited by Sterling Doc; 10-22-2011 at 01:02 AM.
10-21-2011, 10:46 PM
#51
Rennlist Member
Thread Starter
Ram intake colector is next!
It wouldn't take much more to hit 150 RWHP. You said it had a stock exhaust? Still have a cat too? performance exhaust (or simple cat delete), and add some minor p&p work (see my thread on my work with the intake), add a mild cam and or a maf, and you could easily break 150hp.
Do you have any other plans to improve the intake system?
Do you have any other plans to improve the intake system?
Also, I am looking to make some type of ram intake collector to feed the filter. Will be testing some options where to position the air collector. Will be posting updates in this thread as I make progress.
Last edited by Dimi 944; 10-24-2011 at 09:25 AM.
