Boxster Drivetrain Loss Factor ...
09-19-2002, 08:40 PM
#1
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Boxster Drivetrain Loss Factor ...
If this subject has been covered before, please direct me to it, but I wasn't able to find it by searching this forum.
I recently read an article (published in '96/'97'ish) that reviewed a Boxster (2.5 l) that had been supercharged. The thing that caught my attention was the baseline dyno results. The shop took a stock 986 with 205 bhp to the dyno and got a result of ~138 RWHP, for a whopping 33% drivetrain loss! They were very surprised and stated that 15%-20% loss is a more typical range. To make sure the dyno was correct and that the car was not defective, they ran a different Boxster on the same dyno, and then both cars on a different dyno, all with the same results: 33% drivetrain loss.
Has Porsche managed to engineer an exceptional car even with this substantial drivetrain loss, or was this an early issue that has been remedied in conjunction with the subsequent roll-out of the larger engined cars? Or is this all just balderdash?
The reason that I ask is that I just saw the dyno chart on Ken2KS's web site, and his modified '00 Boxster S appears to put out ~240 RWHP. Now, if that 33% drivetrain loss is accurate, and has not changed, that seems to be quite a jump (to 358 bhp?!!) over the stock 250 bhp claimed by Porsche. All that by adding EVO air intake and TTP headers (and some fancy waxes, decals and floor mats, among other things
). Wow! Move over 951 mod. potential!!!
Okay, I don't really think that is the case. So what's up with this, then? Is the explanation abundantly clear to everyone but me?
Please set me straight on this (... and do be kind).
- Brian
'05 Boxster RS (V8)
I recently read an article (published in '96/'97'ish) that reviewed a Boxster (2.5 l) that had been supercharged. The thing that caught my attention was the baseline dyno results. The shop took a stock 986 with 205 bhp to the dyno and got a result of ~138 RWHP, for a whopping 33% drivetrain loss! They were very surprised and stated that 15%-20% loss is a more typical range. To make sure the dyno was correct and that the car was not defective, they ran a different Boxster on the same dyno, and then both cars on a different dyno, all with the same results: 33% drivetrain loss.
Has Porsche managed to engineer an exceptional car even with this substantial drivetrain loss, or was this an early issue that has been remedied in conjunction with the subsequent roll-out of the larger engined cars? Or is this all just balderdash?
The reason that I ask is that I just saw the dyno chart on Ken2KS's web site, and his modified '00 Boxster S appears to put out ~240 RWHP. Now, if that 33% drivetrain loss is accurate, and has not changed, that seems to be quite a jump (to 358 bhp?!!) over the stock 250 bhp claimed by Porsche. All that by adding EVO air intake and TTP headers (and some fancy waxes, decals and floor mats, among other things
). Wow! Move over 951 mod. potential!!!Okay, I don't really think that is the case. So what's up with this, then? Is the explanation abundantly clear to everyone but me?
Please set me straight on this (... and do be kind).- Brian
'05 Boxster RS (V8)
09-19-2002, 11:51 PM
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Hmmm I never thought of it that way, I've got 358 HP!!! I like that! Yeah baby yeah!
Typically a driveline like the Boxsters which is more similar to a front wheel drive car setup than a rear wheel drive front engine set up is more efficient, between 10 and 15% drive train loss.
I suspect either they had a faulty dyno, or two faulty cars, but it was probably their dyno. I've never seen any other report that the drive train was that poor, although the Boxster S like I have does use a different tranny, I can't believe the 2.5 and now 2.7 tranny is really much different in terms of efficiency.
My base in the "S" was about 15% below crank horsepower as rated by Porsche and I trust the dyno I run on as being pretty accurate and my results also match those of Robert's in California so that rules out either of our dynos as the odds of them both being defective by the same amount would be next to nil.
I just have to believe some other factors are involved in those results, not drive train loss, although it "could" be that Porsche overstated the HP on the 2.5 and was more truthful on the 2.7 and 3.2, but I would have thought someone would have caught them on that, especially after what happened to Mazda and the Miata recently.
Typically a driveline like the Boxsters which is more similar to a front wheel drive car setup than a rear wheel drive front engine set up is more efficient, between 10 and 15% drive train loss.
I suspect either they had a faulty dyno, or two faulty cars, but it was probably their dyno. I've never seen any other report that the drive train was that poor, although the Boxster S like I have does use a different tranny, I can't believe the 2.5 and now 2.7 tranny is really much different in terms of efficiency.
My base in the "S" was about 15% below crank horsepower as rated by Porsche and I trust the dyno I run on as being pretty accurate and my results also match those of Robert's in California so that rules out either of our dynos as the odds of them both being defective by the same amount would be next to nil.
I just have to believe some other factors are involved in those results, not drive train loss, although it "could" be that Porsche overstated the HP on the 2.5 and was more truthful on the 2.7 and 3.2, but I would have thought someone would have caught them on that, especially after what happened to Mazda and the Miata recently.
09-20-2002, 01:56 AM
#3
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Oh, beHAVE! 
Now THAT sounds more like it! They said that they tried a couple of dynos (at different shops) and a couple of cars, but I still found it hard to believe that any manufacturer could manage to design a car with that much inefficiency, given the modern state of technology. Okay, maybe a '39 Packard, but a turn-of-the-millennium Porsche?!
Thanks for your corroborated data to set the record straight for me. I can let this one go, now. It's been bugging me (off and on) for a couple of weeks (i.e., since I read the article ... possibly on the Turbo Performance Center web site, but I can't recall for certain).
Thanks again,
- Brian
Now THAT sounds more like it! They said that they tried a couple of dynos (at different shops) and a couple of cars, but I still found it hard to believe that any manufacturer could manage to design a car with that much inefficiency, given the modern state of technology. Okay, maybe a '39 Packard, but a turn-of-the-millennium Porsche?!
Thanks for your corroborated data to set the record straight for me. I can let this one go, now. It's been bugging me (off and on) for a couple of weeks (i.e., since I read the article ... possibly on the Turbo Performance Center web site, but I can't recall for certain).
Thanks again,
- Brian
09-20-2002, 09:46 AM
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Yeah that is on the TPC website, was in a magazine article that someone did on their supercharger for the 2.5.
Speaking of TPC and superchargers, a shop local to me wants to try and sort out the problems with the SC on the 3.2L, some of which is in the ECU programming evidently. If they get the parts they need, I'm the guinea pig and will post how it comes out.
Maybe then I will have 358 HP!!!
Speaking of TPC and superchargers, a shop local to me wants to try and sort out the problems with the SC on the 3.2L, some of which is in the ECU programming evidently. If they get the parts they need, I'm the guinea pig and will post how it comes out.
Maybe then I will have 358 HP!!!
09-20-2002, 02:19 PM
#5
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<img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />
Keep your fingers crossed and let us know how it goes. Being a guinea pig for these things can be a double edged sword, but the upside always seems to be too tempting to ignore!
Good luck!
- Brian
Keep your fingers crossed and let us know how it goes. Being a guinea pig for these things can be a double edged sword, but the upside always seems to be too tempting to ignore!
Good luck!
- Brian
09-23-2002, 02:54 PM
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This article might make interesting reading <a href="http://www.pumaracing.co.uk/trans.htm" target="_blank">Puma Racing - Transmission Losses</a> (along with most of the others on that site, for that matter - plenty of straight talking 
).
).
09-23-2002, 05:30 PM
#7
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Thread Starter
WOW! Great resource, JohnM! Answers to my questions and more. Right up my alley. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Thanks,
- Brian
Thanks,
- Brian
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09-24-2002, 05:37 PM
#8
RL Community Team
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[quote]Originally posted by brians:
<strong>...got a result of ~138 RWHP, for a whopping 33% drivetrain loss!</strong><hr></blockquote>
33% is way too high. I've seen a lot of postings on this and 15% is the number I believe.
Maybe it was a high temp/altitude test environment and they printed the actual rather than SAE corrected numbers.
Just for reference, my stock 944S2 made 187 RWHP.
<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=011134&p=" target="_blank">http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=011134&p=</a>
Karl.
<strong>...got a result of ~138 RWHP, for a whopping 33% drivetrain loss!</strong><hr></blockquote>
33% is way too high. I've seen a lot of postings on this and 15% is the number I believe.
Maybe it was a high temp/altitude test environment and they printed the actual rather than SAE corrected numbers.
Just for reference, my stock 944S2 made 187 RWHP.
<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=011134&p=" target="_blank">http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=011134&p=</a>
Karl.
10-01-2002, 08:25 PM
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When TPC dyno'ed a 993, they only got 209 RWHP. See the following link:
<a href="http://turboperformance.ws/images/911scdyno.jpg" target="_blank">http://turboperformance.ws/images/911scdyno.jpg</a>
There's something very fishy about TPC's dyno figures.
Karl.
<a href="http://turboperformance.ws/images/911scdyno.jpg" target="_blank">http://turboperformance.ws/images/911scdyno.jpg</a>
There's something very fishy about TPC's dyno figures.
Karl.
10-10-2002, 01:14 AM
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different dynos around the world show different results in australia your dyno figures of 245rwhp are way to high we see around 190rwhp as very high for a 3.2ltr and 175 as normal it just depends on if dyno read SAE OR DINN . THE DINN BEING THE LOWER FIGURE the two result on the same car still run it down the qtr in the same time
10-10-2002, 05:29 AM
#11
[quote]Originally posted by Ken2KS:
<strong>Yeah that is on the TPC website, was in a magazine article that someone did on their supercharger for the 2.5.
Speaking of TPC and superchargers, a shop local to me wants to try and sort out the problems with the SC on the 3.2L, some of which is in the ECU programming evidently. If they get the parts they need, I'm the guinea pig and will post how it comes out.
Maybe then I will have 358 HP!!! </strong><hr></blockquote>
Ken, for info I have got from a well respected tuner in the UK is that a low boost SC setup will normally give somewhere between 95-100 hp per litre, torque usually in line with HP and 90% available from 2-2500rpm. It depends on the car obviously. The HP figure depends on level of boost from 4.5psi upwards. If you want serious gains you will have to lower comp ratio and possibly use an IC depending on the application.
Good luck with that!
<strong>Yeah that is on the TPC website, was in a magazine article that someone did on their supercharger for the 2.5.
Speaking of TPC and superchargers, a shop local to me wants to try and sort out the problems with the SC on the 3.2L, some of which is in the ECU programming evidently. If they get the parts they need, I'm the guinea pig and will post how it comes out.
Maybe then I will have 358 HP!!!
</strong><hr></blockquote>Ken, for info I have got from a well respected tuner in the UK is that a low boost SC setup will normally give somewhere between 95-100 hp per litre, torque usually in line with HP and 90% available from 2-2500rpm. It depends on the car obviously. The HP figure depends on level of boost from 4.5psi upwards. If you want serious gains you will have to lower comp ratio and possibly use an IC depending on the application.
Good luck with that!
10-12-2002, 12:33 AM
#12
Three Wheelin'
Not sure if I believe the whole % concept. If it is the same driveline in car A and car B and car A has 225 hp and car B has 300, should they both not lose the same, say 75 hp? 1/3 in car A and 1/4 in car B????
