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Old 09-16-2006, 01:17 PM   #1
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Smile Have you dynoed your 2.7L Boxster?

I just got back from Performance Autosport in Richmond, VA where I had my 2000 2.7L boxster dynoed, what fun. It was my first time at a dyno and the tech, Kevin was very helpful and answered lots of my novice questions. Things like what gear do the run the test in, 4th, which is closest to the 1:1 ratio of the engine/transmission.

Really cool to see the car strapped down (I forgot to bring my camera) and watch the tires spin up to redline in fourth gear (142 mph). The car sounded great, especially above 6000 rpm.

I only wish I had known about this Performace Autosports, which is a 1.5 hour drive from our home before I had a TTP intake, Fabspeed bypass pipes and Autothourty chip put in the car several months ago, I sure wish I had a baseline reading before I did any mods. BTW, Performance Autosports has a late generation Dynojet Research dyno, very cool. They did three pulls and came up with these numbers:

196.4 HP/ 168 torque
198.1 HP/ 169 torque
198.4 HP/ 169 torque

I will try to scan and post a copy of the readout, but I was impressed by the very flat torque curve, almost flat from 2200 rpm to 6500 rpm. It was also interesting to see that the power peaked at 6500 rpm, then dropped down pretty quickly above that to just 150 hp at 7500 rpm (Autothroity chip allows higher max rpm). The dyno run also showed that above 5000 rpm, I am running a little rich.

My question is, how do these HP numbers at the wheels relate to engine HP. I have heard that there is a 15-20% loss of HP between the engine rating and what shows up at the wheels. Does anyone know what that percentage loss is for our Boxsters?

Subjectively, it sure seemed like there was more performance when I had the TTP intake and chip put into my car. Now with these dyno numbers I am trying to figure out how much over HP over the factory rating I am making based on this dyno run.

I have been very pleased with the mods I have done to the car. The car has been running and sounding great. I have taken several long trips, logging almost 7,000 miles this summer. When I behave myself, I can get 29.5 mpg with steady highway driving with the top down. When I am messing around milage drops to 18-19 mpg.

Finally, having the dyno run done was a great way to spend a saturday morning and 75.00 for me and my teenage son. The two of us exchanged looks as we stood by and watched the Michellin's on the back of the Boxster spin up to over 140 mph and listened to the engine scream. Now thats what I am talking about,

Ed

2000 2.7L Boxster
Arctic Silver/Black, 50K

New:
Brakes, Windshield, Shift Cables, MAF and O2 Sensors

Mods:
TTP Cold Air Intake with BMC Filter Element
AutoThority Performance Chip
Fabspeed Bypass Pipes

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Old 09-16-2006, 07:56 PM   #2
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Awd drive cars have the highest percentage of parisitic loss, followed by Rwd, then Fwd. Rwd cars typically have about a 15% loss which means a 2000 2.7L would have appox 184 hp at the wheels. I noticed you said you watched the car scream to redline....why weren't you behind the wheel during the pulls?
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Old 09-16-2006, 09:15 PM   #3
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Quote:
Originally Posted by Adam
Awd drive cars have the highest percentage of parisitic loss, followed by Rwd, then Fwd. Rwd cars typically have about a 15% loss which means a 2000 2.7L would have appox 184 hp at the wheels. I noticed you said you watched the car scream to redline....why weren't you behind the wheel during the pulls?

Hi,

Yea, I agree with the 15% loss estimate. Now, in day-today driving, you cannot even feel 10-12HP, so how much did those dozen ponies cost you...?

Happy Motoring!... Jim'99
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Old 09-17-2006, 03:15 AM   #4
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Dyno Stuff

I was hoping to be able to do the dyno pulls, but they would not let me. They actually put up a barrier to keep folks from getting too close during the runs. They have one technician that does all the dyno pulls. Must be an insurance thing.

I know what you mean about the cost of the mods Jim. They cost over 2K. Because I dont have a pre-mod baseline, I dont know if the car was making its advertised HP, and hence just how much of an improvement the mods made with performance.

That was one of the reasons I was asking to see if anyone had done a dyno on a stock 2000 2.7L Boxster, mine has 50k miles on it. Do six year old cars still make their advertised HP, or are they typically down a dozen hp or so.

Also, I have seen the 2000 2.7L advertised as having 217 hp in some sources (thats what my owners manual says) and 220 hp in lots of others. Its not big deal, but anyone know what the actual rating is?

With the intake and chip, the car sounds much better to me, and between the flatter torque profile and the 15 or more whp, the car sure seems more responsive. I just wish it was not that expensive to squeeze a little more performance out of the car.

Now, I wonder what headers and high-flow cats might do..... Help me, I am sliding down the slippery slope of car mods, hee, hee, hee.....

Ed
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Old 09-17-2006, 03:46 AM   #5
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Well if my math is correct the numbers you posted seem to make perfect sense at about 15% loss. If your car is advertised at 220hp I would have to say they are using flywheel hp. 220 x .15 = 33 ......... 220-33=187 hp at the wheels you have 198 at the wheels so a ball park figure would bring your mods in at 11hp. You are probably somewhere around 231 hp at the flywheel.
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Old 09-17-2006, 08:47 AM   #6
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You can look at it this way too:

1) Your increased HP (11) cost about $181 per horse ($2,000/11).

2) Comparing a 2007 987 vs. 987S the HP increase is 50 and costs $9,900 or $198 per horse. A 2006 comparison would be $242.50.

Looks like you did OK. The most important thing is that you are happy. And that has far greater value than anything!
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Old 09-17-2006, 04:43 PM   #7
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some additional thoughts

The explanation of driveline loss from engine to wheels sounds right. My last car was an Acura RSX-s. It advertised 200 HP and I dynoed it with 3k miles. It dynoed at 174, which is 12%-13% loss. After bolt-on mods mods it dynoed at 204whp, very easy and cheap to make power.

After a couple of years, with no further mods, whp went up by 6. It dynoed @ 210whp @ 30K mi. I think cars perform better from 25K -75K miles. I dynoed my Z28 every year I owned it (it was free), and it didn't begin to lose power until 85K miles. Power was down 7% at 140K miles, so unless you have major engine problems you shouldn't lose power anytime soon.


One last thought.... When comparing AWD-RWD-FWD power loss, these are ordered most loss to least loss, but wouldn't a mid or rear engine be more similar to a FWD than RWD. Based on proximity if engine to drive wheels, there is no drive shaft or rear diff that most RWD cars have, which causes most of the additional loss. The Boxster's drivetrain would probably lose closer to 12%, which is more consistant with FWD.

Just my thoughts
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Old 09-20-2006, 08:02 AM   #8
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Quote:
Originally Posted by mtch


One last thought.... When comparing AWD-RWD-FWD power loss, these are ordered most loss to least loss, but wouldn't a mid or rear engine be more similar to a FWD than RWD. Based on proximity if engine to drive wheels, there is no drive shaft or rear diff that most RWD cars have, which causes most of the additional loss. The Boxster's drivetrain would probably lose closer to 12%, which is more consistant with FWD.

Just my thoughts
That's a real good point. I was thinking about that the other day myself. I would think that the boxster would be more efficient than say a front engine Rwd car that has a long heavy drive shaft to spin?

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Last edited by Adam; 09-20-2006 at 09:07 AM.
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