Supercharged 993 - Improving charge air cooling
10-13-2012, 04:10 PM
#91
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Juha,
Can I suggest that you do the maths on the charge density in respect of the trade off between intake temperature, charge pressure and supercharger power consumption? We've played around with similar supercharged 964 engines on Motec for some years now and the maths never lies - we always find gains running the IAT cooler by reducing the boost, especially in acceleration terms. The secondary factor is that you can also run more ignition timing with less boost, resulting in reduced EGT (and as a result = lower CHT).
Can I suggest that you do the maths on the charge density in respect of the trade off between intake temperature, charge pressure and supercharger power consumption? We've played around with similar supercharged 964 engines on Motec for some years now and the maths never lies - we always find gains running the IAT cooler by reducing the boost, especially in acceleration terms. The secondary factor is that you can also run more ignition timing with less boost, resulting in reduced EGT (and as a result = lower CHT).
I agree with your reasoning but as allways, things are not black and white. Where do you draw the line?
When you say lowering boost yields more performance,but up to what point? Until you have 0.001bar boost? I doubt it. So there is a middle ground somewhere. Right now i have only 0.35bar boost, i think that is very little, almost next to nothing. If i can raise it up to 0.5bar and still stay within the efficiency range of the supercharger, i think it will yield more power. As long as i have proper charge air cooling, which i now do have.
Btw, we couldn't dial in any advance at all with the lower boost (0.35 vs. 0.55)
In any case, seems to me that the 450hp advertised by TPC is impossible to achieve with this supercharger...would you agree with me Colin?
10-13-2012, 04:32 PM
#92
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I should, but it's more fun to speculate without actual facts...
I agree with your reasoning but as allways, things are not black and white. Where do you draw the line?
When you say lowering boost yields more performance,but up to what point? Until you have 0.001bar boost? I doubt it. So there is a middle ground somewhere. Right now i have only 0.35bar boost, i think that is very little, almost next to nothing. If i can raise it up to 0.5bar and still stay within the efficiency range of the supercharger, i think it will yield more power. As long as i have proper charge air cooling, which i now do have.
Btw, we couldn't dial in any advance at all with the lower boost (0.35 vs. 0.55)
In any case, seems to me that the 450hp advertised by TPC is impossible to avhieve with this supercharger...would you agree with me Colin?
I agree with your reasoning but as allways, things are not black and white. Where do you draw the line?
When you say lowering boost yields more performance,but up to what point? Until you have 0.001bar boost? I doubt it. So there is a middle ground somewhere. Right now i have only 0.35bar boost, i think that is very little, almost next to nothing. If i can raise it up to 0.5bar and still stay within the efficiency range of the supercharger, i think it will yield more power. As long as i have proper charge air cooling, which i now do have.
Btw, we couldn't dial in any advance at all with the lower boost (0.35 vs. 0.55)
In any case, seems to me that the 450hp advertised by TPC is impossible to avhieve with this supercharger...would you agree with me Colin?
I'm sure the result will surprise you.
We have seen over 400hp but nowhere near 450hp with an Eaton 90 - I think TPC's claims are based on unrealistic drivetrain losses from RWHP numbers. We have measured 480hp FWHP on a supercharged 964 engine on Motec running an Autorotor blower.
10-14-2012, 09:23 AM
#93
Although I've read some of the debate on Eaton vs. Lysholm type superchargers in the past, I never suspected the difference in efficiency to be as large as portrayed in the article posted by Haygeebaby. Thanks for posting, very insightful!
I have found some further reference on a Jag XKR engine sapping 84HP in driving its Eaton supercharger with 139C temps, vs. Autorotor 59HP and 98C temps.http://www.jagweb.com/aj6eng/superchargers.php
On the matter of calculating IAT into air mass:
Density= Pressure / (R x Temperature)
D= kg/m^3
P = Pascal --> 1 bar = 100000 Pascal
R= gas constant = 287.05 for dry air
T= Kelvin = (celsius + 273)
Running IAT's of 30C at 1.35 bar absolute vs. 65C at 1.55 bar absolute means a % difference in air density of 1.55 / 1.59 = 0.975 or -2.5% only .
In isolation this effect of running 35% less boost would cost 11BHP on a 400HP engine. I say isolation, since lower IAT also positively relates to knock threshold, max timing advance and CHT's as per Colin's argumentation.
Accordingly, the fact that the autorotor pump absorbs less crankshaft energy and drastically reduces IAT's makes for a very powerful package compared to Eaton type compressors.
I have found some further reference on a Jag XKR engine sapping 84HP in driving its Eaton supercharger with 139C temps, vs. Autorotor 59HP and 98C temps.http://www.jagweb.com/aj6eng/superchargers.php
On the matter of calculating IAT into air mass:
Density= Pressure / (R x Temperature)
D= kg/m^3
P = Pascal --> 1 bar = 100000 Pascal
R= gas constant = 287.05 for dry air
T= Kelvin = (celsius + 273)
Running IAT's of 30C at 1.35 bar absolute vs. 65C at 1.55 bar absolute means a % difference in air density of 1.55 / 1.59 = 0.975 or -2.5% only .
In isolation this effect of running 35% less boost would cost 11BHP on a 400HP engine. I say isolation, since lower IAT also positively relates to knock threshold, max timing advance and CHT's as per Colin's argumentation.
Accordingly, the fact that the autorotor pump absorbs less crankshaft energy and drastically reduces IAT's makes for a very powerful package compared to Eaton type compressors.
Last edited by evoderby; 10-14-2012 at 09:41 AM.
10-14-2012, 12:31 PM
#94
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Running IAT's of 30C at 1.35 bar absolute vs. 65C at 1.55 bar absolute means a % difference in air density of 1.55 / 1.59 = 0.975 or -2.5% only .
In isolation this effect of running 35% less boost would cost 11BHP on a 400HP engine. I say isolation, since lower IAT also positively relates to knock threshold, max timing advance and CHT's as per Colin's argumentation.
In isolation this effect of running 35% less boost would cost 11BHP on a 400HP engine. I say isolation, since lower IAT also positively relates to knock threshold, max timing advance and CHT's as per Colin's argumentation.
Yes, a 35C lower intake temp will result in 20-30C lower cylinder head temps. A 25C head temp difference will not only give better acceleration and power, it also provides a more stable burn rate which is much less detonation prone. Furthermore, according to the Eaton 90 operating graphs, a 3psi boost increase consumes around 7-10hp more in drive power losses.
Last edited by NineMeister; 10-14-2012 at 12:50 PM.
10-14-2012, 03:14 PM
#95
Thanks for the additional info/graphs Colin!
I intended the 3psi difference in my calcs to represent the effect of (added) intercooler restriction, just as Juha is experiencing...I should have been more clear on this.
Indeed upping boost through running a smaller pulley is going to consume additional drive power as shown in your graphs, resulting in an even more delicate balance in the upwards power potential through increasing boost....
An autorotor compressor running a very easy going 0.4Bar non intercooled (no pressure drop) intake seems an easy to fit 400HP system within the confines of a 911 non wing engine bay.
With 80% efficiency as claimed here, http://www.jagweb.com/aj6eng/supercharging_article.php , IAT's would run at 38C on a 20C day. Add some water injection to the equation and you're safer than Fort Knox;-)
I intended the 3psi difference in my calcs to represent the effect of (added) intercooler restriction, just as Juha is experiencing...I should have been more clear on this.
Indeed upping boost through running a smaller pulley is going to consume additional drive power as shown in your graphs, resulting in an even more delicate balance in the upwards power potential through increasing boost....
An autorotor compressor running a very easy going 0.4Bar non intercooled (no pressure drop) intake seems an easy to fit 400HP system within the confines of a 911 non wing engine bay.
With 80% efficiency as claimed here, http://www.jagweb.com/aj6eng/supercharging_article.php , IAT's would run at 38C on a 20C day. Add some water injection to the equation and you're safer than Fort Knox;-)
10-18-2012, 12:45 PM
#96
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Yes, a 35C lower intake temp will result in 20-30C lower cylinder head temps. A 25C head temp difference will not only give better acceleration and power, it also provides a more stable burn rate which is much less detonation prone. Furthermore, according to the Eaton 90 operating graphs, a 3psi boost increase consumes around 7-10hp more in drive power losses.
I got the smaller 2,4" pulley yesterday and went ahead and installed it. Nevermind the sweaty 2hours I spent removing the old pulley (that's another story)
Today we put her on my friends dyno. First run we saw 0.6bar boost and mixture getting somewhat lean. After adding about 10% more fuel the engine laid down 390hp and 480Nm with a very very nice torque curve.
We didn't have to pull the ignition from the last setup, there was no detonation (we did get detonation with 5 degrees more advance)
The IAT's were well in check. At first they maxed out at arond 40dgr celcius but after repositioning the auxiliary fan (so that there was direct flow over the wing, the IAT dropped down to 28-30*C.
On the street I couldn't get the IAT to exceed 20*C but it was a rather cold day (about 10*C).
I am very happy with the current setup/tune, knowing that I have very useful power, over 450Nm from 4000rpm-6000rpm.
So in this case, raising the SC rpm did yield more power.
Last edited by Juha G; 10-18-2012 at 01:00 PM.
10-18-2012, 01:52 PM
#99
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Very good discussion going on in here, I just love this place!!!
I got the smaller 2,4" pulley yesterday and went ahead and installed it. Nevermind the sweaty 2hours I spent removing the old pulley (that's another story)
Today we put her on my friends dyno. First run we saw 0.6bar boost and mixture getting somewhat lean. After adding about 10% more fuel the engine laid down 390hp and 480Nm with a very very nice torque curve.
We didn't have to pull the ignition from the last setup, there was no detonation (we did get detonation with 5 degrees more advance)
The IAT's were well in check. At first they maxed out at arond 40dgr celcius but after repositioning the auxiliary fan (so that there was direct flow over the wing, the IAT dropped down to 28-30*C.
On the street I couldn't get the IAT to exceed 20*C but it was a rather cold day (about 10*C).
I am very happy with the current setup/tune, knowing that I have very useful power, over 450Nm from 4000rpm-6000rpm.
So in this case, raising the SC rpm did yield more power.
I got the smaller 2,4" pulley yesterday and went ahead and installed it. Nevermind the sweaty 2hours I spent removing the old pulley (that's another story)
Today we put her on my friends dyno. First run we saw 0.6bar boost and mixture getting somewhat lean. After adding about 10% more fuel the engine laid down 390hp and 480Nm with a very very nice torque curve.
We didn't have to pull the ignition from the last setup, there was no detonation (we did get detonation with 5 degrees more advance)
The IAT's were well in check. At first they maxed out at arond 40dgr celcius but after repositioning the auxiliary fan (so that there was direct flow over the wing, the IAT dropped down to 28-30*C.
On the street I couldn't get the IAT to exceed 20*C but it was a rather cold day (about 10*C).
I am very happy with the current setup/tune, knowing that I have very useful power, over 450Nm from 4000rpm-6000rpm.
So in this case, raising the SC rpm did yield more power.
Awesome, anywhere close to 400p is a great result for that blower.
Now go and do ten laps of your local circuit.......
10-18-2012, 05:14 PM
#100
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I didn't measure it but i think the original is 2.8"
Thanks Colin! I agree with you, this as good as it gets with this setup.
It's quite obvious from the torque curve that the cams are restricting the flow at higher rpms. The torque dramatically drops down after 5000rpm.
I wonder if 500hp would be achievable with more aggressive cams and a more efficient blower!?
I hope i can do a track test in the next few days, the weather does not look very promising though...
I assume that with your comment you are implying that the heat generated by the supercharger would deteriorate the performance. However, i couldn't get the IAT higher than 30*C on the dyno, even after a dozen consecutive pulls. And on the road with proper cooling not even over 20 degrees. The cylinder head temps stayed below 200*C too...
It's quite obvious from the torque curve that the cams are restricting the flow at higher rpms. The torque dramatically drops down after 5000rpm.
I wonder if 500hp would be achievable with more aggressive cams and a more efficient blower!?
I hope i can do a track test in the next few days, the weather does not look very promising though...
I assume that with your comment you are implying that the heat generated by the supercharger would deteriorate the performance. However, i couldn't get the IAT higher than 30*C on the dyno, even after a dozen consecutive pulls. And on the road with proper cooling not even over 20 degrees. The cylinder head temps stayed below 200*C too...
Last edited by Juha G; 10-19-2012 at 01:45 AM.
10-19-2012, 09:15 AM
#103
Good job Juha!
Your conscious says you should be happy, yet your heart is craving for more boost...you've been bitten by the bug my friend!;-)
I've done some further calcs on the M90 - Autorotor comparison data provided in the article linked by Haygeebaby. Using the formula provided in my previous post I checked to see whether any significant differences in supercharger driving losses exist between the two. The 308HP M90 run @ 0.64Bar and 72C post intercooler IAT gives a Density figure of 1.656 . Dong the same for the 311HP autorotor run @ 0.57Bar and 54C post intercooler IAT gives 1.673 .
The relevance of this is that (308 / 1.656) x 1.673 = 311.1HP (!) . More or less spot on. This means that with proper intercooling there is no significant difference in compressor drive loss between the two types of charger. (As long as both are performing within their efficiency range, the Jaguar example of 84HP vs. 59HP seems nonsense). The Lysholm charger seems to have a much broader efficiency range though, and is much more efficient temperature wise shown by pre intercooler temps. Your current Intercooler however runs so efficiently with a 20C delta to outside air, that running an Autorotor at your current boost level won't do a whole lot for performance.
I do feel there's not much additional margin left from the M90 you're now running. In your quest for 500HP, switching to an autorotor to keep IAT's/efficiency in check at higher boost levels would need 1.24 Bar @ 35C IAT or 1.31 Bar @ 45C IAT......When changing your intercooler cores to a parallel design (M90 setup - same pulley you run now) you should however instantly gain at least 0.15* bar MAP or 427.5 HP. With 0.2Bar refound losses this figure becomes 439.8 HP....
*Some educated guesses here: Again, 0.2 bar additional pressure loss against a chargecooler already known to loose 0.2-0.25 Bar in itself is considered way beyond performance design criterea. http://www.bellintercoolers.com/pages/techFAQ.html , short tubes & large tube area & large frontal area is what is wanted.....0.1-0.15 Bar pressure loss is figure to aim for. Given the fact that the GT2 RS chargers are designed to flow & cool 310HP per bank running them up to 2x250HP should prove no problem to at least achieve a very middle of the road 0.2Bar overall pressure drop.
Cheers,
H
Your conscious says you should be happy, yet your heart is craving for more boost...you've been bitten by the bug my friend!;-)
I've done some further calcs on the M90 - Autorotor comparison data provided in the article linked by Haygeebaby. Using the formula provided in my previous post I checked to see whether any significant differences in supercharger driving losses exist between the two. The 308HP M90 run @ 0.64Bar and 72C post intercooler IAT gives a Density figure of 1.656 . Dong the same for the 311HP autorotor run @ 0.57Bar and 54C post intercooler IAT gives 1.673 .
The relevance of this is that (308 / 1.656) x 1.673 = 311.1HP (!) . More or less spot on. This means that with proper intercooling there is no significant difference in compressor drive loss between the two types of charger. (As long as both are performing within their efficiency range, the Jaguar example of 84HP vs. 59HP seems nonsense). The Lysholm charger seems to have a much broader efficiency range though, and is much more efficient temperature wise shown by pre intercooler temps. Your current Intercooler however runs so efficiently with a 20C delta to outside air, that running an Autorotor at your current boost level won't do a whole lot for performance.
I do feel there's not much additional margin left from the M90 you're now running. In your quest for 500HP, switching to an autorotor to keep IAT's/efficiency in check at higher boost levels would need 1.24 Bar @ 35C IAT or 1.31 Bar @ 45C IAT......When changing your intercooler cores to a parallel design (M90 setup - same pulley you run now) you should however instantly gain at least 0.15* bar MAP or 427.5 HP. With 0.2Bar refound losses this figure becomes 439.8 HP....
*Some educated guesses here: Again, 0.2 bar additional pressure loss against a chargecooler already known to loose 0.2-0.25 Bar in itself is considered way beyond performance design criterea. http://www.bellintercoolers.com/pages/techFAQ.html , short tubes & large tube area & large frontal area is what is wanted.....0.1-0.15 Bar pressure loss is figure to aim for. Given the fact that the GT2 RS chargers are designed to flow & cool 310HP per bank running them up to 2x250HP should prove no problem to at least achieve a very middle of the road 0.2Bar overall pressure drop.
Cheers,
H
10-19-2012, 02:44 PM
#104
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Now that you have achieved your end goal, here are some runs from the 9m dyno of supercharged 964 engines.
From the bottom (lowest power/torque) up you have:
Stock 964 with TPC conversion, original Motronic installation
Stock 964 with TPC, 9m Motec upgrade
Lowered compression 964, Opcon blower (German Autos kit) with 9m Motec upgrade
Lowered compression 964, Autorotor blower, 9m Motec upgrade.
Unfortunately I can't remember the boost levels but suffice to say that the TPC kit was not intercooled and was a stock engine. The Opcon engine was an unknown, believed to have been converted by a UK specialist some time ago but never ran correctly until the Motec was fitted. The Autorotor engine was rebuilt by 9m, 9.0:1 compression and ran a very large full-width intercooler (single core).
From the bottom (lowest power/torque) up you have:
Stock 964 with TPC conversion, original Motronic installation
Stock 964 with TPC, 9m Motec upgrade
Lowered compression 964, Opcon blower (German Autos kit) with 9m Motec upgrade
Lowered compression 964, Autorotor blower, 9m Motec upgrade.
Unfortunately I can't remember the boost levels but suffice to say that the TPC kit was not intercooled and was a stock engine. The Opcon engine was an unknown, believed to have been converted by a UK specialist some time ago but never ran correctly until the Motec was fitted. The Autorotor engine was rebuilt by 9m, 9.0:1 compression and ran a very large full-width intercooler (single core).
10-19-2012, 04:43 PM
#105
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I do feel there's not much additional margin left from the M90 you're now running. In your quest for 500HP, switching to an autorotor to keep IAT's/efficiency in check at higher boost levels would need 1.24 Bar @ 35C IAT or 1.31 Bar @ 45C IAT......When changing your intercooler cores to a parallel design (M90 setup - same pulley you run now) you should however instantly gain at least 0.15* bar MAP or 427.5 HP. With 0.2Bar refound losses this figure becomes 439.8 HP....
However, I am not sure if it is the supercharger or the cams (or both) that hit the wall at 5000rpm...? There would be plenty more hp if I could keep the torque from falling for another 1000rpm.
Now that you have achieved your end goal, here are some runs from the 9m dyno of supercharged 964 engines.
From the bottom (lowest power/torque) up you have:
Stock 964 with TPC conversion, original Motronic installation
Stock 964 with TPC, 9m Motec upgrade
Lowered compression 964, Opcon blower (German Autos kit) with 9m Motec upgrade
Lowered compression 964, Autorotor blower, 9m Motec upgrade.
Unfortunately I can't remember the boost levels but suffice to say that the TPC kit was not intercooled and was a stock engine. The Opcon engine was an unknown, believed to have been converted by a UK specialist some time ago but never ran correctly until the Motec was fitted. The Autorotor engine was rebuilt by 9m, 9.0:1 compression and ran a very large full-width intercooler (single core).
From the bottom (lowest power/torque) up you have:
Stock 964 with TPC conversion, original Motronic installation
Stock 964 with TPC, 9m Motec upgrade
Lowered compression 964, Opcon blower (German Autos kit) with 9m Motec upgrade
Lowered compression 964, Autorotor blower, 9m Motec upgrade.
Unfortunately I can't remember the boost levels but suffice to say that the TPC kit was not intercooled and was a stock engine. The Opcon engine was an unknown, believed to have been converted by a UK specialist some time ago but never ran correctly until the Motec was fitted. The Autorotor engine was rebuilt by 9m, 9.0:1 compression and ran a very large full-width intercooler (single core).
The last setup would be really nice! How durable would the engine be with such a configuration? Was anything else changed than pistons? Different cams, bigger valves?
Will the gearbox handle that amount of torque?
btw, It looks like I'll be doing a track test on sunday, that is if the weather clears up.
