Splitter expansion road tests with video and pressure values.
08-12-2009, 11:41 AM
#31
Rennlist Member
Thread Starter
Yep, double checked it. you basically get vacuum at just about the edge ofthe hood. no place for intake inlets! 
mk
Pierre, I thought when we looked closer, they were just about in the right range. best you got the air at the base of the windshield anyway. its almost the same pressure as the nose of the car, so you are in good shape!
best,
Mark
mk
Pierre, I thought when we looked closer, they were just about in the right range. best you got the air at the base of the windshield anyway. its almost the same pressure as the nose of the car, so you are in good shape!
best,
Mark
Thanks.
The scoop openings did actually match up with the mouths of the stock intake tubes. That was my original line of thought, but I never ran the car like that, so now they're just for show. Changed my mind after I saw Porsche's aerodynamic graphs for the 928, and moved the intake to the base of the windscreen, which is a high-pressure area.
The scoop openings did actually match up with the mouths of the stock intake tubes. That was my original line of thought, but I never ran the car like that, so now they're just for show. Changed my mind after I saw Porsche's aerodynamic graphs for the 928, and moved the intake to the base of the windscreen, which is a high-pressure area.
Last edited by mark kibort; 08-15-2009 at 07:31 PM.
08-15-2009, 07:42 PM
#32
Rennlist Member
Thread Starter
While Anderson was at Laguna walking around looking at cars today, I was on the road finishing the testing of the splitter.
With 4 more support cables, the problem is fixed. Here is the video. Not only to 120mph, but to 130mph. It was quite a morning. I had to do the test 4 times due to battery failure with the go-pro camera. I(t needs really good rechargeables in great shape)
anyway, got a lot of pressure data points all over the front of the car and even in the engine compartment.
http://www.youtube.com/watch?v=UXgjpPbQcgs
Pressure test results:
At the splitter:
60mph .04psi
80mph .11psi
100mph ..17psi
120mph .30psi
130mph .32psi
under car behind splitter:
0-120mph 00psi nothing changed vs ambient
Hood vent area:
50mph .04psi vacuum
100mph .08psi vacuum
and for our doubting Thomas (Jim Bailey)
At the radiator front and behind (just around the fan output, but fans off):
In front of the radiator: Same as nose, inlet, and splitter pressures.
Behind the radiator:
50mph .03psi
60mph .04psi
100mph .08psi
showing that there is a pressure drop across the radiator, but pressure and flow goes up with speed almost to the extent of the pressure at the nose of the car. This means that Jim's commet of the max flow of a radiator is at 25mph? is dead wrong. in fact, the air flow is so great above 100mph, that it backdrives the cooling fans.
With 4 more support cables, the problem is fixed. Here is the video. Not only to 120mph, but to 130mph. It was quite a morning. I had to do the test 4 times due to battery failure with the go-pro camera. I(t needs really good rechargeables in great shape)
anyway, got a lot of pressure data points all over the front of the car and even in the engine compartment.
http://www.youtube.com/watch?v=UXgjpPbQcgs
Pressure test results:
At the splitter:
60mph .04psi
80mph .11psi
100mph ..17psi
120mph .30psi
130mph .32psi
under car behind splitter:
0-120mph 00psi nothing changed vs ambient
Hood vent area:
50mph .04psi vacuum
100mph .08psi vacuum
and for our doubting Thomas (Jim Bailey)
At the radiator front and behind (just around the fan output, but fans off):
In front of the radiator: Same as nose, inlet, and splitter pressures.
Behind the radiator:
50mph .03psi
60mph .04psi
100mph .08psi
showing that there is a pressure drop across the radiator, but pressure and flow goes up with speed almost to the extent of the pressure at the nose of the car. This means that Jim's commet of the max flow of a radiator is at 25mph? is dead wrong. in fact, the air flow is so great above 100mph, that it backdrives the cooling fans.
Last edited by mark kibort; 08-16-2009 at 01:44 PM.
08-16-2009, 02:05 PM
#34
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Hey Mark,
Isn't the radiator inlet grille in the lower part of the nose wrecking the usefulness of the splitter? If you could block that grille and still cool the engine I bet you pressure readings would go way up, depending on where you are measuring the pressure, of course.
Approx how many square inches is the splitter and what is the pressure just below the splitter?
Chris Cervelli
Spline Technologies
Isn't the radiator inlet grille in the lower part of the nose wrecking the usefulness of the splitter? If you could block that grille and still cool the engine I bet you pressure readings would go way up, depending on where you are measuring the pressure, of course.
Approx how many square inches is the splitter and what is the pressure just below the splitter?
Chris Cervelli
Spline Technologies
08-16-2009, 04:13 PM
#35
Rennlist Member
Thread Starter
Chris,
Actually, the main function of the splitter is to re-route air that would normally go under the car, to the sides of the car. there is a side benefit of having some pressuer build up on the splitter surface as well pushing down on it. But, as you can see from my 1/16" aluminum sheet, the pressure of .3psi is not enough to flex it with the support wires. the theroetical maximum flat plate pressure. (your idea of closing off the nose), would be near the same. (in theory, .11psi at 80mph, and .44psi at 160mph). Plus, if you block off the splitter, and raise the air pressure slightly, where does that air go? thats right, it will spill off under the car and negate down force. Case in point. Nose pressure (well above air inlets) with and without a splitter have still the same values and those values are close to the base of the windshield pressure value as well.
The HUGE advantage of an opening just over the splitter is to route the air that is spilling off the nose, capture it and route it to he next lower pressure areas, (sides of the car and through the radiator) after the radiator, where does it go? Normally, it would go under the car, negating some of the adavantages of downforce up front, but with a hood vent, where the perssure is very low, the air goes up and over the car, adding to the downforce. If you look at most ALMS cars now, they all incorporate this technique to add to the downforce, even the porsches have above splitter vents and hood vents to release the air to neutralize some of the vacuum on top of the car.
The pressure at the splitter, about 2/3s of the way to the front edge, is .32psi at 120mph. Just under the splitter, I was measuring 0psi (ambient) and slightly vacuum if you get caught measuring where the splitter, starts to point up toward the chassis, creating a vacuum area, before it neutralizes under the engine to 0 again.
The splitter is about 300sq-inches. amazing how the little 1' adder strip added so much more force to cause it to fail. (250sq-inches prior). that only works out to around 100lbs of downforce at 120mph, but less than 30 at 80mph. However, the benefit of the splitter at 80mph is far more beyond the actual force on the splitter. its the volume of air that is now re-routed over and to the sides of the car.
All facinating stuff. Wish I had a wind tunnel to test this stuff. Im going to get put in Jail testing on the streets! I spent 7 gallons of gas and 2 hours testing yesterday. It was like a track day!
Actually, the main function of the splitter is to re-route air that would normally go under the car, to the sides of the car. there is a side benefit of having some pressuer build up on the splitter surface as well pushing down on it. But, as you can see from my 1/16" aluminum sheet, the pressure of .3psi is not enough to flex it with the support wires. the theroetical maximum flat plate pressure. (your idea of closing off the nose), would be near the same. (in theory, .11psi at 80mph, and .44psi at 160mph). Plus, if you block off the splitter, and raise the air pressure slightly, where does that air go? thats right, it will spill off under the car and negate down force. Case in point. Nose pressure (well above air inlets) with and without a splitter have still the same values and those values are close to the base of the windshield pressure value as well.
The HUGE advantage of an opening just over the splitter is to route the air that is spilling off the nose, capture it and route it to he next lower pressure areas, (sides of the car and through the radiator) after the radiator, where does it go? Normally, it would go under the car, negating some of the adavantages of downforce up front, but with a hood vent, where the perssure is very low, the air goes up and over the car, adding to the downforce. If you look at most ALMS cars now, they all incorporate this technique to add to the downforce, even the porsches have above splitter vents and hood vents to release the air to neutralize some of the vacuum on top of the car.
The pressure at the splitter, about 2/3s of the way to the front edge, is .32psi at 120mph. Just under the splitter, I was measuring 0psi (ambient) and slightly vacuum if you get caught measuring where the splitter, starts to point up toward the chassis, creating a vacuum area, before it neutralizes under the engine to 0 again.
The splitter is about 300sq-inches. amazing how the little 1' adder strip added so much more force to cause it to fail. (250sq-inches prior). that only works out to around 100lbs of downforce at 120mph, but less than 30 at 80mph. However, the benefit of the splitter at 80mph is far more beyond the actual force on the splitter. its the volume of air that is now re-routed over and to the sides of the car.
All facinating stuff. Wish I had a wind tunnel to test this stuff. Im going to get put in Jail testing on the streets! I spent 7 gallons of gas and 2 hours testing yesterday. It was like a track day!
Hey Mark,
Isn't the radiator inlet grille in the lower part of the nose wrecking the usefulness of the splitter? If you could block that grille and still cool the engine I bet you pressure readings would go way up, depending on where you are measuring the pressure, of course.
Approx how many square inches is the splitter and what is the pressure just below the splitter?
Chris Cervelli
Spline Technologies
Isn't the radiator inlet grille in the lower part of the nose wrecking the usefulness of the splitter? If you could block that grille and still cool the engine I bet you pressure readings would go way up, depending on where you are measuring the pressure, of course.
Approx how many square inches is the splitter and what is the pressure just below the splitter?
Chris Cervelli
Spline Technologies
08-16-2009, 11:37 PM
#37
Rennlist Member
Thread Starter
I still have not run as fast as I did at sears with my S4 wing on stilts. ((well, only marginally faster with the stroker engine. I hope to change that this next race at sears! )
Lets take my splitter and make one out of CF or plywood and mount it to your car and get those stilts for the rear S4 wing.
mk
((well, only marginally faster with the stroker engine. I hope to change that this next race at sears! )Lets take my splitter and make one out of CF or plywood and mount it to your car and get those stilts for the rear S4 wing.
mk
08-17-2009, 12:21 AM
#38
Race Director
I still have not run as fast as I did at sears with my S4 wing on stilts. ((well, only marginally faster with the stroker engine. I hope to change that this next race at sears! )
Lets take my splitter and make one out of CF or plywood and mount it to your car and get those stilts for the rear S4 wing.
mk
((well, only marginally faster with the stroker engine. I hope to change that this next race at sears! )Lets take my splitter and make one out of CF or plywood and mount it to your car and get those stilts for the rear S4 wing.
mk
Its easy to do.......especially with a custom CF shop literally across the street.....
But do you think a raised-tilted stock wing will provide enough downforce? Everyone else runs a "mega" wing?
Of course having a race 928 that runs is priority #1....it should be running tomorrow (but I've heard that before)
08-17-2009, 01:44 AM
#39
Rennlist Member
Thread Starter
As you may have heard, through my testing, I measured 90lbs of downforce at 10 degrees inclination. when i put the cup car wing on, at 8 degrees, the car was near undriveable, as seen by the Laguna race in '06. I ended up at 0 to match the correct downforce of the car. it wasnt until I put the splitter on, was I able to get that wing back to the 5 degree range. bottomline, the old S4 wing, at 10 degrees was able to put the same downforce as the cup car CF wing at 0, which is what you need right now. the difference, is drag. 10degrees vs cup car wing at 0 is probably double the drag. at 90lbs of downforce, drag is 9lbs on the cup car wing. probably near 18lbs with the S4 wing due to its efficiency and its greater angle. So, in the end, put on the S4 wing stilts. Heck, If I had to for a race spec, I would have no problem putting it back on. IN fact, I bet my car would be faster without a wing right now.
MK
Its easy to do.......especially with a custom CF shop literally across the street.....
But do you think a raised-tilted stock wing will provide enough downforce? Everyone else runs a "mega" wing?
Of course having a race 928 that runs is priority #1....it should be running tomorrow (but I've heard that before)
Its easy to do.......especially with a custom CF shop literally across the street.....
But do you think a raised-tilted stock wing will provide enough downforce? Everyone else runs a "mega" wing?
Of course having a race 928 that runs is priority #1....it should be running tomorrow (but I've heard that before)
08-17-2009, 04:46 PM
#40
Rennlist Member
Thread Starter
Well, what do ya think?
Are you still running the C car, or the GT3 now?
Are you still running the C car, or the GT3 now?
Hey Mark,
Isn't the radiator inlet grille in the lower part of the nose wrecking the usefulness of the splitter? If you could block that grille and still cool the engine I bet you pressure readings would go way up, depending on where you are measuring the pressure, of course.
Approx how many square inches is the splitter and what is the pressure just below the splitter?
Chris Cervelli
Spline Technologies
Isn't the radiator inlet grille in the lower part of the nose wrecking the usefulness of the splitter? If you could block that grille and still cool the engine I bet you pressure readings would go way up, depending on where you are measuring the pressure, of course.
Approx how many square inches is the splitter and what is the pressure just below the splitter?
Chris Cervelli
Spline Technologies
08-26-2009, 08:17 PM
#41
Rennlist Member
Thread Starter
I did some more pressure tests, getting a reading on top of the hood, just in front of the hood vent. -.2psi (vacuum) at 120mph. WOW! what i need to do now, is close off the vent and see if the rear of the hood vent vacuum goes up in pressure. I suspect it will.
While at Laguna, I took a closer look at Andersons splitter. now mine is even bigger, but not as low, so I would imagine that is a trade off. some of the pressure area that builds up in front, can spill under the car ,where his fights it with a lower set up. however, mine is only about 1" higher ,but extends to be flush with the nose area now. Andersons is slightly rearward.
I like the plywood touch! I wonder if the cup car guys this weekend at his race, knew he was racing with a home depot, plywood splitter
. Actually, now it looks pretty good painted white. you can barely tell.
mk
While at Laguna, I took a closer look at Andersons splitter. now mine is even bigger, but not as low, so I would imagine that is a trade off. some of the pressure area that builds up in front, can spill under the car ,where his fights it with a lower set up. however, mine is only about 1" higher ,but extends to be flush with the nose area now. Andersons is slightly rearward.
I like the plywood touch! I wonder if the cup car guys this weekend at his race, knew he was racing with a home depot, plywood splitter
. Actually, now it looks pretty good painted white. you can barely tell.mk
