More 100-300kph stuff
12-18-2007, 02:15 PM
#31
Instructor
Join Date: Aug 2003
Location: UK
Posts: 202
Likes: 0
Received 0 Likes
on
0 Posts
Looking at Jean's graph, there seems to be a "hump" in all three gears. If the power was graphed against time rather than speed would the hump be the same length? Its appearance in all three gears hints at something engine related rather than anything to do with drag or downforce. Maybe something that takes a while to heat up after which the power is reduced slightly?
Only a thought.
regards
Steve
Only a thought.
regards
Steve
12-18-2007, 02:29 PM
#32
Addict
Rennlist Member
Rennlist Member
Thread Starter
Looking at Jean's graph, there seems to be a "hump" in all three gears. If the power was graphed against time rather than speed would the hump be the same length? Its appearance in all three gears hints at something engine related rather than anything to do with drag or downforce. Maybe something that takes a while to heat up after which the power is reduced slightly?
Only a thought.
regards
Steve
Only a thought.
regards
Steve
This does not correlate with what you would guess from the long G graph is it ?
Not sure why this is - Jean ?
12-18-2007, 02:57 PM
#33
Addict
Rennlist Member
Rennlist Member
Thread Starter
Sorry if this is getting a bit boring for others - there seems some ambiguity here ?
I do not know how to get the AX22 to "smooth" the G data (I presume that is how Jean has got the lines in the graph in the post above so flat ?) but the graph below shows the raw G data:
The 193 run is the 2WD original run, the other two are two back to back 4WD 190mph runs the black one is the one in Jean's graph above "minivmax"
You can see the Gs are up and down and look very close on the graph below - how valid is it to "smooth" them ?
I have no idea really but as I say in the post above the smoothed lines in Jean's graph do not depict what the acceleration chart says which is that the two runs are identical up to 167mph....
I would add that the Driftbox data corelates with the acceleration data (although I have not tried to analyze the DB G data !
This one below puts the acceleration line on the same scale as the G force (un-smoothed -don't know how !!)
I do not know how to get the AX22 to "smooth" the G data (I presume that is how Jean has got the lines in the graph in the post above so flat ?) but the graph below shows the raw G data:
The 193 run is the 2WD original run, the other two are two back to back 4WD 190mph runs the black one is the one in Jean's graph above "minivmax"
You can see the Gs are up and down and look very close on the graph below - how valid is it to "smooth" them ?
I have no idea really but as I say in the post above the smoothed lines in Jean's graph do not depict what the acceleration chart says which is that the two runs are identical up to 167mph....
I would add that the Driftbox data corelates with the acceleration data (although I have not tried to analyze the DB G data !
This one below puts the acceleration line on the same scale as the G force (un-smoothed -don't know how !!)
Last edited by TB993tt; 12-18-2007 at 03:16 PM.
12-21-2007, 08:01 AM
#34
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
TB
It took me a while to answer as this is a very diffcult subject to tackle without the right tools to measure drag and downforce. I agree with you as far as its importance is concerned, and I have spent countless hours as well trying to identify the impact of different hardware on aerodynamics, lift , drag etc.. The more I read about the subject, the more I know that it is impossible to quantify, other than with some logic and assumptions.
Sport Auto is very lucky to have an ex-Mercedes Benz executive on its board, and therefore have access to their wind tunnel, one of the best in the world, and as a result, the data obtained is outstanding, and I am with you on the potential negative effects of Frankeinstein, "how much" is where I might disagree, as it is a front bumper, with no increase on surface area.
One interesting test that I have shows that a 993GT2 EVO with the banana wing on, produced a 1 second slower time up to reach 1 kilometer from a standing still vs. no banana wing. 0-1000meters: 19.85s vs. 20.85s.
By smoothening the run to 0.5-0.6s seconds instead of the factory set 0.3s, what you are doing is calculating running averages over 0.6seconds, which eliminates GPS noise that you see in this run (it reduces accuracy a bit but gives better trends).. Spikes on the dataloggers don't mean much. I do think that the humps seen are indicative of something, I just don't know what.
By looking at distance gained or lost for every point in the run, you get an interesting graph (rather than the tool's cumulative distance covered) The red line is variance between the two runs at every point (gain or loss in relative terms)
After 16-17s it looses dramatically distance per second. If it was aerodynamics, I would have expected a much more smooth decline (slope), as drag is increasing in a constant slope both before and after that point irrespectively...obviously with square of the speed (I can show it on the graph if needed).
I might be missing something big, but I just cannot make sense of the drag numbers needed to do this at 160mph to be honest, as an example, while you are almost at par with an RT12 up to 250kph, it suddenly takes you 5-6 seconds more than an RT12 to go from 250->300kph (from memory)!.
Sorry to make this reading so painful for everybody out there.
It took me a while to answer as this is a very diffcult subject to tackle without the right tools to measure drag and downforce. I agree with you as far as its importance is concerned, and I have spent countless hours as well trying to identify the impact of different hardware on aerodynamics, lift , drag etc.. The more I read about the subject, the more I know that it is impossible to quantify, other than with some logic and assumptions.
Sport Auto is very lucky to have an ex-Mercedes Benz executive on its board, and therefore have access to their wind tunnel, one of the best in the world, and as a result, the data obtained is outstanding, and I am with you on the potential negative effects of Frankeinstein, "how much" is where I might disagree, as it is a front bumper, with no increase on surface area.
One interesting test that I have shows that a 993GT2 EVO with the banana wing on, produced a 1 second slower time up to reach 1 kilometer from a standing still vs. no banana wing. 0-1000meters: 19.85s vs. 20.85s.
By smoothening the run to 0.5-0.6s seconds instead of the factory set 0.3s, what you are doing is calculating running averages over 0.6seconds, which eliminates GPS noise that you see in this run (it reduces accuracy a bit but gives better trends).. Spikes on the dataloggers don't mean much. I do think that the humps seen are indicative of something, I just don't know what.
By looking at distance gained or lost for every point in the run, you get an interesting graph (rather than the tool's cumulative distance covered) The red line is variance between the two runs at every point (gain or loss in relative terms)
After 16-17s it looses dramatically distance per second. If it was aerodynamics, I would have expected a much more smooth decline (slope), as drag is increasing in a constant slope both before and after that point irrespectively...obviously with square of the speed (I can show it on the graph if needed).
I might be missing something big, but I just cannot make sense of the drag numbers needed to do this at 160mph to be honest, as an example, while you are almost at par with an RT12 up to 250kph, it suddenly takes you 5-6 seconds more than an RT12 to go from 250->300kph (from memory)!.
Sorry to make this reading so painful for everybody out there.
12-21-2007, 09:29 AM
#35
Addict
Rennlist Member
Rennlist Member
Thread Starter
Jean
Many thanks for your thoughts on this.....
Using measured data:
I tested the CGT on this exact track/surface....
The CGT has a measured Cd of 0.37 and at 200kph has total 85kg downforce (measured by Sport Auto) and at 300kph its downforce is around the 300kg mark....
My measured data shows the following:
100-300kph: CGT = 28.85s, 993tt = 29.1s
100kph to 260kph: CGT = 16.25s, 993tt =15.9s
260kph to 300kph: CGT = 12.6s, 993tt = 13.2s
Is this proof that my 993tt wearing its new aerodynamics suffers from the same aerodynamic brick walls as the (proven and known downforce producing aero) CGT ?
Is the CGT an example of how a higher Cd shape is "treated" (in terms of air resistance) at these high speeds ?
I appreciate what you say about the frontal aera being the same but surely Franky's front end with its large surface area of intakes is a blunt wall compared to the smooth stock bumper's frontal area which encourages the air to flow around it ?
Many thanks for your thoughts on this.....
Using measured data:
I tested the CGT on this exact track/surface....
The CGT has a measured Cd of 0.37 and at 200kph has total 85kg downforce (measured by Sport Auto) and at 300kph its downforce is around the 300kg mark....
My measured data shows the following:
100-300kph: CGT = 28.85s, 993tt = 29.1s
100kph to 260kph: CGT = 16.25s, 993tt =15.9s
260kph to 300kph: CGT = 12.6s, 993tt = 13.2s
Is this proof that my 993tt wearing its new aerodynamics suffers from the same aerodynamic brick walls as the (proven and known downforce producing aero) CGT ?
Is the CGT an example of how a higher Cd shape is "treated" (in terms of air resistance) at these high speeds ?
I appreciate what you say about the frontal aera being the same but surely Franky's front end with its large surface area of intakes is a blunt wall compared to the smooth stock bumper's frontal area which encourages the air to flow around it ?
12-21-2007, 09:53 AM
#36
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
TB
I had looked at CGT data as well since for me it is the perfect example of how aerodynamics impact a car's acceleration at high speed, the distinction between the two IMO is that one deals with massive downforce whereas the other we are saying is only due to CD changes, as this front bumper does not increase much (if any) the downforce.
Concerning the openings in the bumper, it does make sense that the larger openings impact the drag for sure, however they are the same as the 997TT, which is said to have improved CD as a result of the changes made on it in this area, I am sure that your franky bumper does not benefit from the same air exit path in low pressure zones as the well designed 997TT bumper does and this impacts drag, but this badly? The Techart is an example of how a similar design can have ill effects on CD, the amount of that impact is what is puzzling me.
When I think of GT2 wings and front bumpers and Gt3 wings, or 930s, 935s and other race cars with massive wings and widths and poor aerodynamics, I cannot foresee that a bumper design alone could put you at those CD levels or worse, but I might well be wrong!
I had looked at CGT data as well since for me it is the perfect example of how aerodynamics impact a car's acceleration at high speed, the distinction between the two IMO is that one deals with massive downforce whereas the other we are saying is only due to CD changes, as this front bumper does not increase much (if any) the downforce.
Concerning the openings in the bumper, it does make sense that the larger openings impact the drag for sure, however they are the same as the 997TT, which is said to have improved CD as a result of the changes made on it in this area, I am sure that your franky bumper does not benefit from the same air exit path in low pressure zones as the well designed 997TT bumper does and this impacts drag, but this badly?
The Techart is an example of how a similar design can have ill effects on CD, the amount of that impact is what is puzzling me.When I think of GT2 wings and front bumpers and Gt3 wings, or 930s, 935s and other race cars with massive wings and widths and poor aerodynamics, I cannot foresee that a bumper design alone could put you at those CD levels or worse, but I might well be wrong!
12-21-2007, 06:48 PM
#37
Racer
Join Date: Apr 2007
Posts: 296
Likes: 0
Received 0 Likes
on
0 Posts
I think you have to take into account overall lap times against overall top speed. I have a good mate who races the last of the joest 962's. He used to race an earlier (not sure what year) 962. The joest car hits the brick wall at about 180mph where as the older car would pull way past 200 mph. (the joest car being far far quicker on a lap). The lap time difference is a mile apart. Horses for courses I guess. Around Spa with the joest 962 car he has to lift to change gear as the G force is to great to make the gear change. That takes a lot of getting your head around, or at least it does for me.
04-27-2008, 08:40 AM
#38
Addict
Rennlist Member
Rennlist Member
Thread Starter
Time to revive this thread since we are testing again next weekend.
My spec is same as before but no Frankenstein front spoiler just a GT2 style front lip.
Aerocalculations done by Jussi already show that in this format the car's Cd is bad, somewhere between 0.36 and 0.4 !
I have only had the car up to 150mph but it does feel very stable but it seems that stability will be costly in terms of drag. Hopefully the 0-170mph will not be affected like last time. Just to refresh in the graqph below the green line is the Franky front spoiler and the red is with Turbos S front spoiler and 2WD....
An interesting data point is the new GT2 with 530PS tested by Sport Auto this car has a Cd of 0.32 CdA 0.66 - the GT2s 200-300 takes 25.1s with 2 gearchanges - my Franky front end took 22.2s with 1 change and with ttS front end (2WD ~530PS) mine took 19.4s !
My spec is same as before but no Frankenstein front spoiler just a GT2 style front lip.
Aerocalculations done by Jussi already show that in this format the car's Cd is bad, somewhere between 0.36 and 0.4 !
I have only had the car up to 150mph but it does feel very stable but it seems that stability will be costly in terms of drag. Hopefully the 0-170mph will not be affected like last time. Just to refresh in the graqph below the green line is the Franky front spoiler and the red is with Turbos S front spoiler and 2WD....
An interesting data point is the new GT2 with 530PS tested by Sport Auto this car has a Cd of 0.32 CdA 0.66 - the GT2s 200-300 takes 25.1s with 2 gearchanges - my Franky front end took 22.2s with 1 change and with ttS front end (2WD ~530PS) mine took 19.4s !
04-28-2008, 07:39 AM
#40
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
05-03-2008, 08:25 AM
#41
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
05-03-2008, 01:43 PM
#42
Addict
Rennlist Lifetime Member
Rennlist Lifetime Member
Some preliminary data:
UMW stage 2 w/stock intercooler, max speed of 173, max IAT of 51 C, ambient of 15 C
UMW stage 2 w/Secan, max speed of 179, max IAT of 37, ambient of 18 C
It was interesting to note that with the stock intercooler max IAT occured before top speed. What appeared to happen was that as the IAT peaked the ECU pulled boost which reduced the IAT slightly which resulted in a bit more power.
With the Secan peak IAT and max speed coincide very closely and boost is fairly steady. I'll post graphs later.
UMW stage 2 w/stock intercooler, max speed of 173, max IAT of 51 C, ambient of 15 C
UMW stage 2 w/Secan, max speed of 179, max IAT of 37, ambient of 18 C
It was interesting to note that with the stock intercooler max IAT occured before top speed. What appeared to happen was that as the IAT peaked the ECU pulled boost which reduced the IAT slightly which resulted in a bit more power.
With the Secan peak IAT and max speed coincide very closely and boost is fairly steady. I'll post graphs later.
05-03-2008, 02:11 PM
#43
Addict
Rennlist Member
Rennlist Member
Thread Starter
18DegC 1510kg 4WD - usual crappy standing start, uphill, harsh power sapping Bruntingthorpe surface, aerodynamics TBA 0-300kph in 28.94s 
"Texas" mile: 185mph
"Texas" mile: 185mph
05-03-2008, 02:49 PM
#45
Addict
Rennlist Lifetime Member
Rennlist Lifetime Member
Some preliminary data:
UMW stage 2 w/stock intercooler, max speed of 173, max IAT of 51 C, ambient of 15 C
UMW stage 2 w/Secan, max speed of 179, max IAT of 37, ambient of 18 C
It was interesting to note that with the stock intercooler max IAT occured before top speed. What appeared to happen was that as the IAT peaked the ECU pulled boost which reduced the IAT slightly which resulted in a bit more power.
With the Secan peak IAT and max speed coincide very closely and boost is fairly steady. I'll post graphs later.
UMW stage 2 w/stock intercooler, max speed of 173, max IAT of 51 C, ambient of 15 C
UMW stage 2 w/Secan, max speed of 179, max IAT of 37, ambient of 18 C
It was interesting to note that with the stock intercooler max IAT occured before top speed. What appeared to happen was that as the IAT peaked the ECU pulled boost which reduced the IAT slightly which resulted in a bit more power.
With the Secan peak IAT and max speed coincide very closely and boost is fairly steady. I'll post graphs later.
UMW stage 2 w/9M prototype intercooler, max speed of 177, max IAT of 46, ambient of 18 C. Seems like a v good showing in my eyes; higher vmax and lower peak IAT than the stock IC with a 3 degree higher ambient temp. An aftermarket intercooler that works better than stock!
Graph below. And sorry for taking this thread a bit off topic as there isn't a 300 kph speed to be found anywhere in my posts. I don't quite manage to run with the big dawgs.
