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Those are some amazing quarter-mile times for a naturally aspirated non-four-wheel-drive car (991 GT3 The traps speeds are very impressive as well.
I know that the 991 RS is not designed for straight-line speed but it would be interesting to see what the 991RS would be able to run with the dundon headers in place for the 1/4 mile. Would the extra HP of the 4.0 motor negate the more aggressive down forcing of the RS?
Motor Trend tested a stock RS in the quarter-mile at 11.1 at 125 MPH
The torque is there and the RS is lighter, if you removed the wing and covered the fender outlets you might get into the 10's...
I wonder were the dragstrip shifts at redline or short shifting? My guess is that my car will be faster, with the Stage 2 tune, shifting closer to 8500.
I wonder were the dragstrip shifts at redline or short shifting? My guess is that my car will be faster, with the Stage 2 tune, shifting closer to 8500.
I experimented at the track and the car pulls harder if you shift at 8500. Is easier on the engine too!
Here's a plot of the ideal shift points on a stock 991 GT3. The dyno plots from the first post in the thread for the headers suggest a power curve larger similar in shape to stock (but boosted up), so I suspect the ideal shift points with the headers are similar.
Here's a plot of the ideal shift points on a stock 991 GT3. The dyno plots from the first post in the thread for the headers suggest a power curve larger similar in shape to stock (but boosted up), so I suspect the ideal shift points with the headers are similar.
So you are saying 9000 in first three gears then 4th@8850, 5th@8750 and 6th@8700 did i get that right?
The 991 C2S and GTS share the same base engine so they physically would fit. I will just have to do the needed testing on the dyno before being able to fully produce them. The GTS has the x51 power kit so I would want to do separate testing to see if that setup wants a specific header design compared to what the regular 3.8 would want.
Got some time sheets from 991 Gt3. Customer said no time differences with muffler bypass or side delete and Ti center muffler. Then he tried Dundon Race headers. Was a big enough difference they pulled him out for a tech inspection looking for Nitrous!
This is same tires, same pressures, same launch, no wing etc. as apples to apples as it can get. Left is Dundon Race Headers. Right is stock/center delete/side and Ti muffler
I thought all the rev limiters got changed to 8500 at the last second. The RS we tested on the dyno was 8500.
Yip. One of the biggest hood jobs from PAG of recent years. The Tacho is dashed from 8400, the stated 8800 and the journos just took that as fact but in sportauto it will do 8800 on ly in gear 1 then it peals back gear by gear to 8575. A number of owners have shown me their aim traces on this. On manual it allows a bit more latitude but mostly it shifts in the 8675 range. To me this is something PAG should have been taken to task on as its tantamount to lying. I suspect its also why the RS isnt overtly quicker than the GT3 despite all the aero and lightweight stuff and capacity increase.
Hopefully they fix this up for the next iteration.
Well done on the 1/4mile slips. Thats a tangible improvement! You will have my money and my order very soon Charles/James!
Here's a plot of the ideal shift points on a stock 991 GT3. The dyno plots from the first post in the thread for the headers suggest a power curve larger similar in shape to stock (but boosted up), so I suspect the ideal shift points with the headers are similar.
Great work on the graph! I did the same couple years ago but lost the file since. The car does seem to shift short of 9000 after 3rd gear in auto, so the gearbox programming most likely takes that into account. When shifting manually, I'd shift at 8500 or earlier because no one is 100% precise, especially without proper shift lights, and bouncing off the limiter even once costs more time than shifting 200-300RPM short of optimal.
Great work on the graph! I did the same couple years ago but lost the file since. The car does seem to shift short of 9000 after 3rd gear in auto, so the gearbox programming most likely takes that into account. When shifting manually, I'd shift at 8500 or earlier because no one is 100% precise, especially without proper shift lights, and bouncing off the limiter even once costs more time than shifting 200-300RPM short of optimal.
Thanks. I did a quick and dirty overlay of the Dundon headers power curves (matching the OEM traces and then looking at the headers trace overlaps for shift points), and it confirms that the theoretical ideal shift points are virtually identical to stock (redline in the first few gears, then gradually reducing):
04-11-2016, 07:48 PM
The traps speeds are very impressive as well.
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