N/A AFM tune + Abuse + BHP predictions etc...
#46
That calculator is based on averages from Edmunds...nowhere to factor in things like gear ratios and tire size.
A more accurate 0-60 is 6.3-6.5s according to a numerical ODE solver that does factor in all these variables (if anyone wants to see the MATLAB code I have it...I can't take credit for it though). I entered tire diameter based on the 195/165/R16 tires you are running, the gear ratios are pulled from Clark's Garage data for a 924S, the drag coefficient * frontal area = 0.647 m2 according to Wikipedia for a 944S (closest I could find, from here). I assumed a 0.7s average shift time, code assumes starting with the car in first and no wheel spin (doesn't account for clutch slip). Imported a Spec 944 dyno power and torque curve and adjusted for your expected power and torque. Used 2266 lbs weight. Again I'm happy to show the code, it's based on a Runge-Kutta numerical ODE solver and was a major school project for the numerical methods class at Baylor University that all students had to complete, he got an A for this.
I said as low as 6.3 to account for a slightly lower CoD, maybe lower shift time, and maybe +10 hp. Also shifting higher than 6200. You are still over 6 secs until 200 bhp or so.
and why are you getting onto me for saying "we?" I mean people who have already worked this out in the past. Most people understand basic physics. Nobody here is on a high horse, you're being antagonistic for no reason. You're asking a lot of questions and getting mad and frustrated when you get replies. At this point it's damage control to offset the misinformation you are posting. fml.
A more accurate 0-60 is 6.3-6.5s according to a numerical ODE solver that does factor in all these variables (if anyone wants to see the MATLAB code I have it...I can't take credit for it though). I entered tire diameter based on the 195/165/R16 tires you are running, the gear ratios are pulled from Clark's Garage data for a 924S, the drag coefficient * frontal area = 0.647 m2 according to Wikipedia for a 944S (closest I could find, from here). I assumed a 0.7s average shift time, code assumes starting with the car in first and no wheel spin (doesn't account for clutch slip). Imported a Spec 944 dyno power and torque curve and adjusted for your expected power and torque. Used 2266 lbs weight. Again I'm happy to show the code, it's based on a Runge-Kutta numerical ODE solver and was a major school project for the numerical methods class at Baylor University that all students had to complete, he got an A for this.
Code:
"The time required to go from 0 to 60 mph is: 6.5122 seconds. The time required to go from 5 to 60 mph is: 6.2788 seconds. The time required to go from 30 to 70 mph is: 6.6055 seconds. The time required to run a quarter mile is: 14.6582 seconds at 93.05325 mph"
and why are you getting onto me for saying "we?" I mean people who have already worked this out in the past. Most people understand basic physics. Nobody here is on a high horse, you're being antagonistic for no reason. You're asking a lot of questions and getting mad and frustrated when you get replies. At this point it's damage control to offset the misinformation you are posting. fml.
Nice pretty graphs, don't waste your time on this new Subject brought up by Voith, I'm not arsed if it's 5 , 6 or 7 seconds to 60
.. get back to the afm questions.......
R
#47
RL Community Team
Rennlist Member
Rennlist Member
I've done one of my MScs in England, in Cranfield. Title was: MSc in Computational Fluid Dynamics. I've been working as a simulation solver developer for the past years.
Will you believe me if I tell you that the "barn door" hinders air flow?
I guess not. It doesn't make it any less true, though.
Basically, it acts like an orifice decreasing the cross-sectional area which introduces a pressure drop before and after the orifice. That is a hydraulic loss.
Yes, this is not a problem, when the door is fully open. But at that point the device does not measure anything, it only says "more than what I can measure".
Yes, it slows down throttle response below 4500 rpm. Whether one can feel it or not, I can't say. Depends on how good the driver is, I reckon.
Yes, best would be to get rid of the square opening as well and have a constant diameter circular one instead, a la Augment's big bore airbox.
Edit:
Yes, Porsche will totally put it in even if it's restrictive. Here's why: because you need to measure air flow to be able to control fuel injection. They chose the AFM + Motronic because it is better than a carburetor. (Some might disagree, though.)
If they had access to more modern measurement devices, be sure they would have used that. Like how they ditched the AFM for the 968. Or is that already on the "newer things are just there 'cause they're cheaper not because they're better" side? Then you should convert back to a carburetor.
Or explain why the AFM is best? The sensor that is a restriction in the lower half of the rpm range and cannot measure at all in the upper half.
Will you believe me if I tell you that the "barn door" hinders air flow?
I guess not. It doesn't make it any less true, though.
Basically, it acts like an orifice decreasing the cross-sectional area which introduces a pressure drop before and after the orifice. That is a hydraulic loss.
Yes, this is not a problem, when the door is fully open. But at that point the device does not measure anything, it only says "more than what I can measure".
Yes, it slows down throttle response below 4500 rpm. Whether one can feel it or not, I can't say. Depends on how good the driver is, I reckon.
Yes, best would be to get rid of the square opening as well and have a constant diameter circular one instead, a la Augment's big bore airbox.
Edit:
Yes, Porsche will totally put it in even if it's restrictive. Here's why: because you need to measure air flow to be able to control fuel injection. They chose the AFM + Motronic because it is better than a carburetor. (Some might disagree, though.)
If they had access to more modern measurement devices, be sure they would have used that. Like how they ditched the AFM for the 968. Or is that already on the "newer things are just there 'cause they're cheaper not because they're better" side? Then you should convert back to a carburetor.
Or explain why the AFM is best? The sensor that is a restriction in the lower half of the rpm range and cannot measure at all in the upper half.
#49
Im going to say 152rwhp, so about 188 crank. The same as my 944S really. She will drop off pretty hard after 5500rpm due to airflow restrictions in the intake system and the natural limits of the heads. Even ported they don't flow nearly as well as the 16V stuff. Your cam will help make up for some of that along with the porting in your heads, but the stock AFM will limit your gains.
I still maintain you would have been better off swapping a 968 engine, I say that because i DD my S2 with one swapped in it its pretty great even at 6,000ft. Its much quicker than my 924S and 944S were and i never want to go back to the other 944 motors. You have less weight but i don't think you'll get under 2450ish on the car even fully stripped.
I still maintain you would have been better off swapping a 968 engine, I say that because i DD my S2 with one swapped in it its pretty great even at 6,000ft. Its much quicker than my 924S and 944S were and i never want to go back to the other 944 motors. You have less weight but i don't think you'll get under 2450ish on the car even fully stripped.
#50
Race Car
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Location: Austin TX, drinking beer in the garage
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Im going to say 152rwhp, so about 188 crank. The same as my 944S really. She will drop off pretty hard after 5500rpm due to airflow restrictions in the intake system and the natural limits of the heads. Even ported they don't flow nearly as well as the 16V stuff. Your cam will help make up for some of that along with the porting in your heads, but the stock AFM will limit your gains.
I still maintain you would have been better off swapping a 968 engine, I say that because i DD my S2 with one swapped in it its pretty great even at 6,000ft. Its much quicker than my 924S and 944S were and i never want to go back to the other 944 motors. You have less weight but i don't think you'll get under 2450ish on the car even fully stripped.
I still maintain you would have been better off swapping a 968 engine, I say that because i DD my S2 with one swapped in it its pretty great even at 6,000ft. Its much quicker than my 924S and 944S were and i never want to go back to the other 944 motors. You have less weight but i don't think you'll get under 2450ish on the car even fully stripped.
I'll answer the question. I predict you won't make over 165 rwhp (~188 crank) and you stand a ~20% chance of grenading the engine on the dyno because of a poor tune
Last edited by Dougs951S; 02-04-2016 at 10:15 PM.
#52
RL Community Team
Rennlist Member
Rennlist Member
He did change all the fenders to fiberglass and all the windows (except the front) to lexan, so I do not debate his claims of weight loss.
Actually, I love his build, like I kept saying in his original thread, but he got really tangled up with this AFM topic. I guess it's going to get better the next time he discusses it with his engineer, maybe that chap doesn't know yet that there are plug & play replacements.
Actually, I love his build, like I kept saying in his original thread, but he got really tangled up with this AFM topic. I guess it's going to get better the next time he discusses it with his engineer, maybe that chap doesn't know yet that there are plug & play replacements.
#55
He did change all the fenders to fiberglass and all the windows (except the front) to lexan, so I do not debate his claims of weight loss.
Actually, I love his build, like I kept saying in his original thread, but he got really tangled up with this AFM topic. I guess it's going to get better the next time he discusses it with his engineer, maybe that chap doesn't know yet that there are plug & play replacements.
Actually, I love his build, like I kept saying in his original thread, but he got really tangled up with this AFM topic. I guess it's going to get better the next time he discusses it with his engineer, maybe that chap doesn't know yet that there are plug & play replacements.
#56
Addict
Rennlist Member
Rennlist Member
There are few a bit optimistic parts here I think.
Sunroof 8.5kg ??
Bonnet 10Kg
Front Badge Panel 1.5kg
Rear Hatch & Spoiler 17kg
GTS Lights 15kg ??
Rear Bumper 3.75kg
Front Wings x2 10kg
Front Bumper 6kg
Lexan Side Windows 2Kg
Carbon canister 1.75kg
Mirrors 5kg ??
TOTAL Weight Saving 75kg
Interior
Battery 13.5kg
Rear hatch motor 2kg
Seats / Mounts 24kg
Wind up window / motor 1.5kg
Stereo / speakers 4.75kg
Sunroof motor & Cover 2.5kg??
Spare wheel / jack 19.5kg ????
Rear seats / upholstery 11.25kg
Steering Wheel & Boss 1kg ??
Total 80kg
Suspension / Brakes
Calipers (x4) 13kg ????
Torsion Tube .5kg
Discs Front Tarox (Lighter) .5kg
Torsion bars 2kg
Rear Trailing Arms 1kg
Handbrake shoes / Cables 3kg ???
Total 20kg
Engine & Bay
3.0 Block 5kg
Crank 3kg
Pistons & Rods .5kg
Flywheel 4.25kg
Timing Pulley .25kg
Balance Shafts (2) 1kg
Inlet Manifold 1kg
Airbox 2.75kg
Alternator 3kg ??
Alternator / Bracket .5kg
Radiator .75kg
Radiator fan 1.5kg
Washer bottle 6kg ??????
Header tank .5kg
Misc ? 4kg ????
Total 34kg
Exhaust
System 11.5kg
Manifold 4.5kg ????
Total 16kg
Grand Total 225kg
Bonnet 10Kg
Front Badge Panel 1.5kg
Rear Hatch & Spoiler 17kg
GTS Lights 15kg ??
Rear Bumper 3.75kg
Front Wings x2 10kg
Front Bumper 6kg
Lexan Side Windows 2Kg
Carbon canister 1.75kg
Mirrors 5kg ??
TOTAL Weight Saving 75kg
Interior
Battery 13.5kg
Rear hatch motor 2kg
Seats / Mounts 24kg
Wind up window / motor 1.5kg
Stereo / speakers 4.75kg
Sunroof motor & Cover 2.5kg??
Spare wheel / jack 19.5kg ????
Rear seats / upholstery 11.25kg
Steering Wheel & Boss 1kg ??
Total 80kg
Suspension / Brakes
Calipers (x4) 13kg ????
Torsion Tube .5kg
Discs Front Tarox (Lighter) .5kg
Torsion bars 2kg
Rear Trailing Arms 1kg
Handbrake shoes / Cables 3kg ???
Total 20kg
Engine & Bay
3.0 Block 5kg
Crank 3kg
Pistons & Rods .5kg
Flywheel 4.25kg
Timing Pulley .25kg
Balance Shafts (2) 1kg
Inlet Manifold 1kg
Airbox 2.75kg
Alternator 3kg ??
Alternator / Bracket .5kg
Radiator .75kg
Radiator fan 1.5kg
Washer bottle 6kg ??????
Header tank .5kg
Misc ? 4kg ????
Total 34kg
Exhaust
System 11.5kg
Manifold 4.5kg ????
Total 16kg
Grand Total 225kg
#57
Instructor
I will give it a shot. 185/159 hp.
And I also think, you will be better off with a standalone ECU.
Maybe this one:
http://speeduino.com/wiki/index.php/Speeduino
And I also think, you will be better off with a standalone ECU.
Maybe this one:
http://speeduino.com/wiki/index.php/Speeduino
#58
#60
I will give it a shot. 185/159 hp.
And I also think, you will be better off with a standalone ECU.
Maybe this one:
http://speeduino.com/wiki/index.php/Speeduino
And I also think, you will be better off with a standalone ECU.
Maybe this one:
http://speeduino.com/wiki/index.php/Speeduino