Disapointing Dyno Test
02-08-2008, 04:27 PM
#31
Instructor
Could be different on a '99 since they are cable throttle compared to the '00. Just a guess.
02-08-2008, 04:39 PM
#32
Race Car
Here is a picture of the resevior on a 99.
Last edited by 1999Porsche911; 02-08-2008 at 07:14 PM.
02-08-2008, 09:18 PM
#33
Race Director
Chassis dynos aren't kind to cars with independent drive axles....
I did a dyno on my 2000 996 C2 yesterday, 243HP@6375rpm on the rear wheels. The factory figures are 300HP@6800 at the crank. The motor is a 2006brand new replacement motor with 15k miles, standard exhaust, standard air box with K&N filter cartridge, cold air intake and the plenum mod. According to the various advertisements, the modifications should give me an additional 25HP, which of course is BS. Assuming I still have 300HP at the crank, is it normal to lose 57HP on the way to the wheels? 57HP lost in the drive train! that's nearly 20% !!!
Could the replacement motor be a 3.4L Cayman S motor (less Variocam Plus)with 295HP@6250rpm? The peak HP occurs at 6375rpm rather than at 6800rpm, that is closer to the Cayman S figures.
There is also a spike in power at 5500rpm where it's up to 235HP, then to dramatically drop to 205HP at 5850, before it climbs up to the max 243HP at 6375. The HP curve seams very strange, I would expect some disturbance around 3500rpm, where the Variocam and Varioram are activated, but at that point the curve is smooth. Could the Variocam and Varioram switching points be wrong?
Please see the attached dyno curve. Are there any one out there who are experts on this, and could tell me if there is something wrong here?
Thanks!
Could the replacement motor be a 3.4L Cayman S motor (less Variocam Plus)with 295HP@6250rpm? The peak HP occurs at 6375rpm rather than at 6800rpm, that is closer to the Cayman S figures.
There is also a spike in power at 5500rpm where it's up to 235HP, then to dramatically drop to 205HP at 5850, before it climbs up to the max 243HP at 6375. The HP curve seams very strange, I would expect some disturbance around 3500rpm, where the Variocam and Varioram are activated, but at that point the curve is smooth. Could the Variocam and Varioram switching points be wrong?
Please see the attached dyno curve. Are there any one out there who are experts on this, and could tell me if there is something wrong here?
Thanks!
This out of parallel with the ground condition this deflection represents a parasitic load that can increase the amount of flywheel horsepower lost to drivetrain.
Best are those cars with the old fashioned solid rear axle. The car can be cinched down nice and tight and the axles being solid so to speak do not deflect and thus drive train losses are the least, though they can still be 15%.
And there are many factors that can affect dyno numbers. As I'm sure someone's already mentioned, dynos are better at doing a before/after reading.
Sincerely,
Macster
02-08-2008, 10:53 PM
#35
For a dynojet, it is about 10 hp low for a 3.4l 6-sp. If you look at the dynos of a 99'-01' Carrera and a Cayman S, they actually look the same. Both dyno consistantly in the 250-255 hp range stock. If you could get a low enough rpm reading, you might find a small improvement at low rpms with the Cayman S motor. A 3.6l dynos about 20 hp higher (low 270's) stock. This dyno is about right for a 3.4l tip. With tips, the torque converter loses a little extra HP. There is definitely a problem with the car. The high rpm dip of 30 hp is not normal. My guess is a varioram problem.
What is the "plenum" mod? Could be related...
What is the "plenum" mod? Could be related...
02-09-2008, 09:40 AM
#36
Drifting
Join Date: Jul 2005
Location: Prince George's County, MD
Posts: 2,481
Likes: 0
Received 1 Like
on
1 Post
Did they email you the run file? Standard (STD) mode gives a higher reading most times than SAE Mode(corrects for temp/Alt differences which makes it a bit better to compare against other 996 dynos).
In STD mode my 996 dyno numbers are 284hp/254tq, my SAE is 275hp/246tq.
I have alot more mods including the plenum and a 6spd, FYI.
In STD mode my 996 dyno numbers are 284hp/254tq, my SAE is 275hp/246tq.
I have alot more mods including the plenum and a 6spd, FYI.
I did a dyno on my 2000 996 C2 yesterday, 243HP@6375rpm on the rear wheels. The factory figures are 300HP@6800 at the crank. The motor is a 2006brand new replacement motor with 15k miles, standard exhaust, standard air box with K&N filter cartridge, cold air intake and the plenum mod. According to the various advertisements, the modifications should give me an additional 25HP, which of course is BS. Assuming I still have 300HP at the crank, is it normal to lose 57HP on the way to the wheels? 57HP lost in the drive train! that's nearly 20% !!!
Could the replacement motor be a 3.4L Cayman S motor (less Variocam Plus)with 295HP@6250rpm? The peak HP occurs at 6375rpm rather than at 6800rpm, that is closer to the Cayman S figures.
There is also a spike in power at 5500rpm where it's up to 235HP, then to dramatically drop to 205HP at 5850, before it climbs up to the max 243HP at 6375. The HP curve seams very strange, I would expect some disturbance around 3500rpm, where the Variocam and Varioram are activated, but at that point the curve is smooth. Could the Variocam and Varioram switching points be wrong?
Please see the attached dyno curve. Are there any one out there who are experts on this, and could tell me if there is something wrong here?
Thanks!
Could the replacement motor be a 3.4L Cayman S motor (less Variocam Plus)with 295HP@6250rpm? The peak HP occurs at 6375rpm rather than at 6800rpm, that is closer to the Cayman S figures.
There is also a spike in power at 5500rpm where it's up to 235HP, then to dramatically drop to 205HP at 5850, before it climbs up to the max 243HP at 6375. The HP curve seams very strange, I would expect some disturbance around 3500rpm, where the Variocam and Varioram are activated, but at that point the curve is smooth. Could the Variocam and Varioram switching points be wrong?
Please see the attached dyno curve. Are there any one out there who are experts on this, and could tell me if there is something wrong here?
Thanks!
02-09-2008, 06:52 PM
#37
Advanced
Join Date: Mar 2007
Posts: 85
Likes: 0
Received 0 Likes
on
0 Posts
That is a ****ty dyno read out.. I hope they did not charge you much for that. I do alot of tuning on my turbo rotary on a dyno dynamics unit and it is awesome.. The one you posted can not be reading right as there is no reason for power to go down then back up unless you are running some sort of sequential turbo and that was the transition...
02-11-2008, 05:17 PM
#38
Rennlist Member
Thread Starter
Thanks folks for all the feed backs. My car is not a tip, it's a 6 speed. Also, the allignment of the wheels on the dyno rolls were good, so there is probably not a big loss due to miss allignment slippage. The motor lid was closed, so it might gotten hot under the lid, causing loss of HP. With the car running and the spoiler up, the motor compartment temperature is very low, and virtually not affected by exhaust and motor heat. This might be one explanation, but not all. The peak and the dip on 5500rpm and 5800rpm are caused by the VarioRam opening, but the drop of 30HP is too much. Also the drop of in HP above 6375rpm is strange. Could it be some kind of fuel starvation or air leak in the intake manifold?
The plenum mod is home made, but if the plenum modifications advertised for $8-900 are working, then my $5 mod is working too, the modification to air flow pattern is the same (Y-shaped plenum rather than T-shaped, with less turbulense and more laminar (and increased) air flow).
During the last week end's DE, the car perfomed just as well as other Carrera's, I can still kee up with 997S's on the main straight on TWS.
Some "experts" say it's the PSM that kicks in, because the front wheels are not turning, but I don't have PSM or any traction control (thank God...). But the ABS warning light came on during the dyno run, could that affect the ECU and upset the power output? Some "experts" I talked to last week end at the DE, said that the 996 is impossible to dyno correctly, due to ECU issues with only rear wheels turning. Any idea folks???
The plenum mod is home made, but if the plenum modifications advertised for $8-900 are working, then my $5 mod is working too, the modification to air flow pattern is the same (Y-shaped plenum rather than T-shaped, with less turbulense and more laminar (and increased) air flow).
During the last week end's DE, the car perfomed just as well as other Carrera's, I can still kee up with 997S's on the main straight on TWS.
Some "experts" say it's the PSM that kicks in, because the front wheels are not turning, but I don't have PSM or any traction control (thank God...). But the ABS warning light came on during the dyno run, could that affect the ECU and upset the power output? Some "experts" I talked to last week end at the DE, said that the 996 is impossible to dyno correctly, due to ECU issues with only rear wheels turning. Any idea folks???
02-11-2008, 06:18 PM
#39
Burning Brakes
Join Date: Oct 2004
Posts: 1,162
Likes: 0
Received 0 Likes
on
0 Posts
If you look at a 987, they have butterflies in both intake crossover tubes. If you split the throttle body side at high RPM, it kills the top end by about 15HP. Ironically, it's even worse when the TB side is split and the main resonance is opened. That dip looks a lot like a 987 motor with intake split and the main resonance not opening. I think a 3.4L 996 motor is closer to a Boxster motor.
Also, get more runs. One run is not statistically significant, and a single run can have a "burp" in it. You should get a minimum of 3. (My last was about 20 runs, specifically different ECU and resonance tuning.) Take your plenum out, check the operation of the resonance tube, and if that doesn't show any improvement, than I wouldn't freak out too much as dynos can vary a lot.
02-11-2008, 07:15 PM
#41
Race Car
They are different, the 2000 I had doesnt have the configuration of vacuum lines like you said as you can see. I never hooked the butterfly (resonance) to any vacuum pods, it went to where the accordian hose goes into the drivers side intake. It was a straight shot to the nipple on the drivers side intake plenum. Here you go:
Last edited by Tippy; 02-11-2008 at 07:21 PM. Reason: a little more specific
02-11-2008, 07:37 PM
#42
Race Car
They are different, the 2000 I had doesnt have the configuration of vacuum lines like you said as you can see. I never hooked the butterfly (resonance) to any vacuum pods, it went to where the accordian hose goes into the drivers side intake. It was a straight shot to the nipple on the drivers side intake plenum. Here you go:
I don't know what accordian hose you are talking about but if it is a vacuum connection, your intakes system will not work correctly. One vacuum line from electric resonnace valve to flap and the other to vacuum source, directly or indirectly.
02-11-2008, 07:50 PM
#44
Instructor
Join Date: Feb 2007
Location: San Jose, CA
Posts: 122
Likes: 0
Received 0 Likes
on
0 Posts
The butterfly valve (tuning flap) in the back crossover tube is controlled by the electric changeover valve (sits right above alternater) which recieves it's vacuum supply from a reserve canister on top of the engine. There is no interface with the brake booster port.
The tuning flap is normally open and operates as follows:
Open from 700 to 3120 rpm and from 5120 rpm .
Closed from 3120 to 5120 rpm , if the throttle is also more than 30 % open at the same time.
The tuning flap is normally open and operates as follows:
Open from 700 to 3120 rpm and from 5120 rpm .
Closed from 3120 to 5120 rpm , if the throttle is also more than 30 % open at the same time.
02-11-2008, 07:51 PM
#45
Race Car
Notice you have a valve that goes on the top of another gold part which I dont know what it is.
Notice mine, the same part in front of the vacuum pod is capped at the top, there is not a SAI valve going into it.
My resonance valve did not tie into any of the 3 parts you have in the pic, or the 2 parts I have in my pics, it went to a nipple on the front of the plenum .
Notice mine, the same part in front of the vacuum pod is capped at the top, there is not a SAI valve going into it.
My resonance valve did not tie into any of the 3 parts you have in the pic, or the 2 parts I have in my pics, it went to a nipple on the front of the plenum .