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We just finished a complete engine rebuild on this 1995 GTS 5 spd. Beautiful car. Customer brought it to us because of excessive oil consumption of about a pint every 200 miles.
Bored it out slightly just to clean up the bores. Nikasil'd the block, new forged pistons and rings. Stock GTS crank and rods were re-used. Pulled his GTS cams and replaced them with our GT cam grind, which is slightly more aggressive than the stock GT cam grind. Also removed the cats and installed a nice SS dual exhaust. Sounds fantastic.
Stock, the GTS has 350 BHP at 5700 rpm, and 369 ft lbs of torque at 4250 rpm.
Now this car has 389 BHP at 6070 rpm, and 409 ft lbs of torque at 4230 rpm
Drives great, pulls hard. I have driven it 300 miles including the dyno session itself (5 pulls to redline under full load) and have zero oil consumption.
Stock exhaust manifolds on this car, with an X pipe cat delete and dual exhaust. Yes, headers would help it further.
No changes were made to the PCV system other than to make sure that everything was working as intended. It is my opinion, and I know I am not alone on this, that the primary reason for the oil consumption on the GTS is that terrible decision they made for not punching the oil holes in the bottom of the sweeper ring groove through to the inside of the piston skirt. So, I look at massaging the crankcase ventilation system on the GTS as really just a band-aid on a much deeper problem. I prefer to get in there and replace those pistons and rings, and then the oil consumption problem is stopped at the source.
Last edited by Carl Fausett; 06-05-2019 at 05:43 PM.
The "correction factor" to get to flywheel horsepower is a bit "loose".
(I use 10% to 12.5% (maximum) for a correction factor to get from rear wheel to flywheel, for a manual transmission.)
The GT cams make all the difference. Did a similar modification 2 years ago on my stock GTS. Should have done it a lot earlier, the engine really comes alive with these cams. My engine was never opened and is not using oil.
Mods:
- GT-cams
- 24 lbs/h injectors
- new ignition components
- SS X-Pipe with high flow cats
- RMB
- Sharktuned
It's an automatic with a 2.2 R&P. Drives great and the new engine characteristics harmonize well with the automatic.
The "correction factor" to get to flywheel horsepower is a bit "loose". (I use 10% to 12.5% (maximum) for a correction factor to get from rear wheel to flywheel, for a manual transmission.)
Greg, you misunderstand what the SAE correction factor is. It is not an adjustment for drivetrain loss.
The correction factor is used on a calibrated dynometer to adjust for air temperature, barometric pressure, and humidity to bring the tests into compliance with SAE J 1349 specifications. The computer will adjust the actual results up or down as needed depending on the conditions at that moment. If memory serves, the SAE spec is that the standard was calibrated for 72 degrees F (just one factor) and you can kinda tell that it was pretty close to that temp when we did our pull. The Correction Factor on this day was very slight - actual HP was 229.4 and the computer adjusted it adjusted it to 331.1 HP. Seems that the temperature, barometric pressure, and humidity this day was very close to the calibrated standard.
Its interesting when I do a dyno test in winter, and the correction factor takes away HP. Cold air being so much more dense - you make a lot more power, but the SAE correction factor again levels that out to what you would have had at 72 degrees, etc.
The "correction factor" to get to flywheel horsepower is a bit "loose".
(I use 10% to 12.5% (maximum) for a correction factor to get from rear wheel to flywheel, for a manual transmission.)
Regardless, it is still a good gain, over stock.
Nice job!
Originally Posted by Carl Fausett
Greg, you misunderstand what the SAE correction factor is. It is not an adjustment for drivetrain loss.
The correction factor is used on a calibrated dynometer to adjust for air temperature, barometric pressure, and humidity to bring the tests into compliance with SAE J 1349 specifications. The computer will adjust the actual results up or down as needed depending on the conditions at that moment. If memory serves, the SAE spec is that the standard was calibrated for 72 degrees F (just one factor) and you can kinda tell that it was pretty close to that temp when we did our pull. The Correction Factor on this day was very slight - actual HP was 229.4 and the computer adjusted it adjusted it to 331.1 HP. Seems that the temperature, barometric pressure, and humidity this day was very close to the calibrated standard.
Its interesting when I do a dyno test in winter, and the correction factor takes away HP. Cold air being so much more dense - you make a lot more power, but the SAE correction factor again levels that out to what you would have had at 72 degrees, etc.
The drive train correction factor you used was to multiply rwhp by 1.175 for engine hp
I customarily publish both rear wheel HP and engine HP, and I did so here. You can use whichever number you want.
The reason for posting engine HP numbers is because the RWHP number was never published by Porsche. So, if a person wants to know how much more HP they have gained over stock, they have to calculate the BHP so they can compare it to the published engine HP.
06-05-2019, 01:50 PM
Fresh GTS engine with GT cams, dyno
