X51 Dyno Run
01-06-2008, 01:15 PM
#31
Addict
Rennlist Member
Rennlist Member
Join Date: Jan 2004
Location: Bethesda, Maryland
Posts: 2,856
Likes: 0
Received 0 Likes
on
0 Posts
01-06-2008, 01:44 PM
#32
Rennlist Member
Thread Starter
Having done hundreds of track laps in this car and bouncing off the rev limiter countless times, I can say without question that the engine pulls strongest just before the fuel cutoff. This may be Sport mode providing a nice top end surge (probably by delivering extra fuel) and/or the ram air effect achieved by the high speeds.
The Porsche Product Information book states:
"To increase driving comfort [in normal mode] a "gentler" cut-off [rev limiter] is generally used when accelerating and reaching the [engine] speed limiter setting. In the process the throttle is continuously closed when approaching the limit range for [engine] speed.
The Sport Chrono function facilitates additional acceleration potential through the use of an abrupt high speed cut-off by switching of individual cylinders (fuel injection & ignition) in a rotating fashion just shortly before the [engine] speed limit."
My notes in [brackets] add some clarity to the piece written by someone with English as their second language... The rest is quoted directly from the product guide.
So, the point is that in Normal mode, the engine management system provides for a soft landing as I approach the redline by cutting fuel in an escalating manner before I get the the limit. I believe this is shown in the dyno graph where the engine goes flat above 7000 rpm and the peak rpm is only 7314. In Sport mode, full fuel and ignition are available right on up to 7400 rpm. A surge is shown on the factory dyno sheet, and confirmed by my butt dyno. The factory dyno sheet shows peak power at about 7200 rpm. My peak power was measured at 6451 rpm! That's where the factory dyno sheet shows the X51 beginning its high end surge...
Compare the HP and TQ on my dyno runs to those of the factory. They are very similar, right down to the roller coaster torque curve between 4000 and 6500 rpm. Now, I'm not suggesting the engine makes much more than 400HP. I believe the conditions and correction factors probably introduce a margin of error and the only true way to measure is on an engine dyno. But, I do believe the full power output of the engine wasn't measured because the Sport mode couldn't be engaged. Had Sport mode been active, I believe 340-345 RWHP could have been achieved.
MC
Last edited by H20NOO; 01-06-2008 at 02:53 PM.
01-06-2008, 04:06 PM
#33
Rennlist Member
Join Date: Aug 2005
Location: Panama City Beach, Florida
Posts: 602
Likes: 0
Received 2 Likes
on
2 Posts
From everything I have seen on this subject, I think that the stock catalytics have the greatest effect. Try an X-51 dyno run with aftermarket cats & no other modifications.
01-06-2008, 11:35 PM
#34
Drifting
Join Date: Apr 2004
Location: WEST SIDE OF MPLS, MN
Posts: 2,628
Likes: 0
Received 0 Likes
on
0 Posts
My car made 628 RWHP on Protomotive's DynaPack dyno (same kind of dyno)
in horrendous Arkansas Summer Heat. These Porsches are very, very impressive cars,
stock or modified!!!
MK
in horrendous Arkansas Summer Heat. These Porsches are very, very impressive cars,
stock or modified!!!
MK
04-05-2011, 11:31 PM
#35
Advanced
Sorry to dig out this old thread as I was trying to find X51 dyno numbers.
Has any other X51 owners dyno their cars with high flow cats or run the car cat-less?
Has any other X51 owners dyno their cars with high flow cats or run the car cat-less?
04-06-2011, 02:00 AM
#36
Rennlist Member
Thread Starter
With 96,000 miles on the odometer and more than 5000 track miles, I'll tell you my X51 997S is running stronger than ever. The only engine issue to date was failure of oil/air seperator which cost a grand to replace. My only complaint is PCCB's are crap for track use. At 38k Porsche said I needed to replace the rear rotors because I had overheated them. Now the front rotors are falling apart. The pedal feel has sucked since mile 1 with waaaay too much pedal travel for a sports car. Other than that, the car has been phenomenal and has been a daily driver for 5 years.
One of the stock mufflers is suffering a crack and odd sounds. Since stock PSE mufflers run something like $1100 each, I may just go with aftermarket mufflers and high flow cats. I'm trying to avoid the expense quite frankly but we'll see. If I take that route, I'll dyno again on the same dyno as before and post the results.
For sure, this X51 lump is nicely broken in now. It has really come alive and seems more eager to rev than ever. I may post another dyno run at 100k miles just for shucks and giggles. My guess is it'll post 345 RWHP under the same conditions/configuration as the earlier dyno results nearly 3 years ago.
Best,
Matt
One of the stock mufflers is suffering a crack and odd sounds. Since stock PSE mufflers run something like $1100 each, I may just go with aftermarket mufflers and high flow cats. I'm trying to avoid the expense quite frankly but we'll see. If I take that route, I'll dyno again on the same dyno as before and post the results.
For sure, this X51 lump is nicely broken in now. It has really come alive and seems more eager to rev than ever. I may post another dyno run at 100k miles just for shucks and giggles. My guess is it'll post 345 RWHP under the same conditions/configuration as the earlier dyno results nearly 3 years ago.
Best,
Matt
04-06-2011, 09:11 PM
#37
Rennlist Member
Join Date: Aug 2005
Location: Panama City Beach, Florida
Posts: 602
Likes: 0
Received 2 Likes
on
2 Posts
This thread came back from the dead. What I would really like to see is an X-51 car run against a modified (or stock) 3.8 on the same dyno, same day. Even though the specific vehicles are no longer produced, it would be enlightening. Any interest in the Long Island/NYC area?
04-07-2011, 09:32 PM
#38
Rennlist Member
With 96,000 miles on the odometer and more than 5000 track miles, I'll tell you my X51 997S is running stronger than ever. The only engine issue to date was failure of oil/air seperator which cost a grand to replace. My only complaint is PCCB's are crap for track use. At 38k Porsche said I needed to replace the rear rotors because I had overheated them. Now the front rotors are falling apart. The pedal feel has sucked since mile 1 with waaaay too much pedal travel for a sports car. Other than that, the car has been phenomenal and has been a daily driver for 5 years.
One of the stock mufflers is suffering a crack and odd sounds. Since stock PSE mufflers run something like $1100 each, I may just go with aftermarket mufflers and high flow cats. I'm trying to avoid the expense quite frankly but we'll see. If I take that route, I'll dyno again on the same dyno as before and post the results.
For sure, this X51 lump is nicely broken in now. It has really come alive and seems more eager to rev than ever. I may post another dyno run at 100k miles just for shucks and giggles. My guess is it'll post 345 RWHP under the same conditions/configuration as the earlier dyno results nearly 3 years ago.
Best,
Matt
One of the stock mufflers is suffering a crack and odd sounds. Since stock PSE mufflers run something like $1100 each, I may just go with aftermarket mufflers and high flow cats. I'm trying to avoid the expense quite frankly but we'll see. If I take that route, I'll dyno again on the same dyno as before and post the results.
For sure, this X51 lump is nicely broken in now. It has really come alive and seems more eager to rev than ever. I may post another dyno run at 100k miles just for shucks and giggles. My guess is it'll post 345 RWHP under the same conditions/configuration as the earlier dyno results nearly 3 years ago.
Best,
Matt
