Hi guys. I am thinking about the exhaust on the 550...… (again not happy with it) Have anyone measured the backpressure with the original system on the car? I mean, a pressure gauge on a stainless steel braided hose might work for a while? In the press kit for the car, it is written that the valves are there to increase the pressure at low RPMs to increase efficiency and gain power. Some sport mufflers have valves, and some don't. How much does this affect torque and power at low RPMs....? I remember when I tested a Peugeot 1,6 l. carbed engine that my mother had, and the exhaust had rusted so it was a big hole in the muffler under the car, the power was at least 20% down... When I force my valves closed, the torque is noticable stronger. So what is ideal for low and high RPMs. I mean if the system is perfectly tuned from the factory, a straight through style muffler set-up would actually reduce horsepower and efficiency at some RPMs and throttle levels. Or will they not? WHO KNOWS ? The Ferrari factory knows their stuff.
I think this would be a great project to undertake and I hope you'll follow through and post results. Many years ago I did something similar with a turbocharged engine on an engine dyno and was amazed at the amount of back pressure at different points in the system. A couple of suggestions: 1. Don't use SS braided hose - on the surface it might seem like a good idea, but the teflon hose inside the SS jacket has a melting point of only 320 degC or 620 degF, so that's not high enough to withstand exhaust temps. Use soft copper tubing instead, and coil it so it will act as a radiator and shed some of the heat before it gets to the measuring instrument. 2. For the measuring instrument, you'll need a differential pressure gauge, rated for air/gas, and with a high working temperature. Probably something with SS internals. I'd think one with a range of 0-5 PSID ought to be sufficient. When I did the turbo motor I thought 0-10 would be sufficient, but I finally had to get one with a range of 0-20 to catch the highest backpressure. 3. Adding the sensing ports to the system may be the biggest headache. You'll want a port at the collectors, just before the cats, then another after the cats, then another after the resonators. Good luck!
Wouldn’t the pressure just before the rear muffler be the one to measure? And that it is equal all the way to the cylinder head? My rear original mufflers are modified to straight through, so they can’t be used anyway....
Eric, the pressure right at the exhaust manifolds (collectors) will be the highest back pressure in the system. Remember you're measuring differential pressure, referenced to atmospheric.
