Engine Performance

Hi, Iam fotis from Germany and a new member in this forum. I currently have a convertible .01 996 C4 and a .08 Mini Cooper JCW. Two weeks ago I went and did an ecu tune on my 996 and did a week later a Dyno run. The Porsche made 276 hp at the flywheel and 325 Nm of Torque. The power at the wheels was around 235 hp. The Dyno used was a Dyno Jet. I can post the Dyno sheet too. The problem is that my Porsch has eBay headers😅, high flow cats and a pipercross air filter and didn't even achieve the stock power figures. The car currently has 127k km on the clock and the engine is at an excellent condition. No ims bearing fail or any oil leaks. It also runs great. The car did run good/better with the hardware at the stock tune and was noticeably faster and more torquey after the tune. Does someone now where this loss of power originates from? I suspect that the mafs sensor is the culprit. The dyno is very accurate. I also measured my mini there and it made as the manic stage 2 map predicted 271 hp. Yeah my mini is faster than my sports car😅. ​

Does no one has a suggestion?

Ditch the eBay headers. What brand is the cat? There is some performance to be had there but not a lot. There is so much you can do to these cars to increase the enjoyment but HP upgrades are not one of them.

The cats are from magnaflow. Sure a n/a engine can't achieve much power trough performance mods, but we are talking about 30 hp less than the factory numbers even though the car got faster...

Sounds like you're in the right ballpark to me: https://jalopnik.com/i-dyno-tested-m...les-1788130306 I wouldn't worry about the numbers - just enjoy driving the car

My stock '99 is 245rwhp. So you aren't as far off as you think. My track car with stock headers, cat delete and magnaflow race mufflers was 265rwhp.

2001 C4 brand new was rated at 296 HP, but I don't know where that was measured, i.e., engine, engine transmission, or at the wheels. It is logical that HP at the wheels would be less due to drive train losses. Actually, I don't think you are doing too bad at 235 HP at the wheels for a 17 year old car (you didn't state mileage which is also a big factor). As said, maybe ditch the ebay headers and get some real headers. However, HP gains are difficult to gain with these engines. https://www.excellence-mag.com/resou...3#.WuieU5ch1hE

The mileage is around 79k miles, sorry I wrote it as kilometres. I knew that the Porsche have lower power ratings but I didn't expect it to be that low. Well the car drives good and I enjoy it. If everything is ok with the engine as you stated it, I wouldn't be happier.

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What were the dyno figures before the tune? It's pretty hard to beat factory tune on these cars. We don't even flash the ecus when increasing displacement to 4.0 liters in most cases.

I can't tell you what it was before, but it definitely was 10- 15% less. I don't think it can be blamed at the age or the mileage because my daily has more mileage at a higher power per displacement ratio and still delivers the power numbers it supposed to do. I think Porsche is cheating on the power figures quite a lot.

I also run the car on the best premium fuel available in Germany. At an American rating it should be like 95 Ron.

I heard running the 3.8s manifolds is a lot better than the after market stainless types you get on eBay , I've got the stainless on mine at the moment and it's on my list to swap for the 3.8 s Manifolds!

Sounds good. Are this the manifolds from the 997? Or the GT3 996?

My guess is Porsche advertises the HP at the flywheel, you are measuring it at the rear wheels and this creates a big difference...

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There is a difference in how they measure. I believe they use flywheel horsepower and DIN ratings, not SAE. DIN read higher than SAE and the % figure for drivetrain loss can vary on who you speak to. One of many reasons you might see a difference. Also, depending on the dyno, how it's strapped down, and other variables, the numbers can vary greatly from car to car and day to day.

This could be true about the measurement, but I still believe that the car doesn't perform as good as it should. For anyone who is interested, I got some 3.8s headers for 80 bucks and iam going to replace the eBay headers with those and report if there was a noticeable improvement.

Removing post I did not mean to place here...

Sorry guys, I suck, this was supposed to go on another thread, I dont use RL much... haha.

Accidental post sorry guys.

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so nearly every item you listed, I've found multiple folks who have tried them and found they cost power. Sad but true. The K&N intake is a great example of non engineered solution,, their filter that fits in the stock airbox, nets more power gain than their entire intake system. Mostly because the K&N doesn't get a solid cold air supply, and the factory does. Example,, Magna flow cats, in real wholesale numbers are a 100 dollar cat, the factory Porsche cats are not 2500+ just for the Porsche tax.. Porsche spend hundred and hundreds of million of dollars on engine airflow design. if headers were that big of a deal they would be on there. once you touch 100HP per liter.. average cost of 10more HP is over 10000 dollars. Cost for horsepower per cubic inch grows logarithmically, Thats why a F1 engine is millions to build. Thats why headers are so over rated on most stock engines.. the entire system has to be flow matched to the head the cam the intake the air temps... it all counts. Heck if you want to get top numbers , the header design for a sea level pull is different than the header for a pull at 5000 feet. Head to head, the stock 996 exhaust header is hard to beat, While Porsche isn't perfect, they don't ever leave much untapped power on the table. I've had enough exposure ot head to head testing on a ENGINE dyne that headers SELDOM if ever produce the gains people think they do. Dyno's are a relative measurement, not an absolute, no two produce the same numbers because there are too many places the operator can tweak that affect end power displayed. If the dyne area is NOT climate controlled generally the numbers are just tuning , not real power. A real dyno cell that can produce repeatable numbers is over $600K You need 100% temp and humidity control in sealed environment.. The HVAC has to be able to handle all the heat and keep the humidity under control to match the power output of the engine. You dont want the dyne being readjusted for every pull.

I've recently just collected my 996 c2. New (4k miles) Hartech engine rebuild and map. Have included read out for anyones interest.... still getting used to the car. CSR GTS exchaust with LWFW otherwise stock with Bilstein suspension. Look forward to my time on the forum

Just to add it is Gen 1 3.4