Two Guys Rally

Performance Loss Hunt: Part 3
[ July 8th, 2008 ] By: Mark Ozimek Posted in » Ramblings, Tips and Tricks

A while back, I made two posts about my car, and how there is a lack of power in the top end compared to what it used to feel like. I verified that the exhaust isn’t causing significant restriction and that the turbo is making about as much boost as it should be.

Since this is turning into a guess and check thing, mostly because my car is 10 years old and has almost 150,000 miles on it, and I don’t know how it was treated for the first 130,000 miles of its life, I said “To hell with it”, and ordered two things that I highly suspect to be contributing to the problem: Vacuum hoses and a CBV diaphragm.

Unfortunately, the vendor I’m getting the CBV diaphragm from does not have any in stock, nor does anyone else that I could find, replacing that part will sit on the back burner for now.

The silicon vacuum hoses from StylinMotors came in the other day, and sat in a corner of my apartment until I had the time to start ripping junk out of my engine compartment to get access to some of the hoses. Thanks to Independence Day being on Friday, I got a three day weekend to have fun. First order of business was figuring out what each hose does, and where it needs to attach to. Ideally, I would be able to just take one hose out, cut a new one to match and install. Knowing what everything does is something important to me, so I couldn’t make it that easy for myself.

After a couple minutes of fun wrestling with worm gear clamps and torx screws, the engine compartment of my S70 looked like this:

(click for larger image)

Although it looks like a disaster, all I really did there was take out the intake filter box and two intercooler pipes that were in the way of some hoses I needed to get to. Judging from the hose clamp style, the hoses are the original parts that were on the car when it rolled off the factory floor.

After prying the clamp off, I found something quite comical and frustrating at the same time. The hoses had rotted into place! I had to cut off every single hose I changed, since they would not come off any other way. Unfortunately, this meant that some of the hoses that are in tight spots did not get changed, since I couldn’t fit my knife into the area. I still plan on changing them though, I just need to remove more parts that get in the way.

Afterwards, the hoses in that picture had been replaced with silicone parts:

While changing out hoses, I found something very interesting. In the first engine picture, there is a small white thing on the very left edge in the center of the picture. This is a check valve that only allows air to flow in one direction. That hose comes from the intake manifold and leads downward to a T junction. The hose going to the right has another check valve, and connects to the intake hose just before the compressor inlet. The other hose goes to a solenoid that is part of the onboard fuel vapor recovery system.

Since the check valves are aligned in such a way to only allow air to be pulled out of the solenoid that is attached to a carbon filter, a broken valve from the intake manifold means that boost pressure can leak out of the intake manifold to before the compressor inlet or into the carbon filter. Both of these are things that should be avoided due to loss of efficiency and contamination of the fuel vapor recovery system.

Either way, I replaced the hoses I had relatively easy access to. Some will require the removal of the intake manifold, another is attached to the compressor housing, which the bottom part of the intake hose blocks, there is even a hose that runs over the top and back down to the back of the engine to the fuel pressure regulator. I’ll try to address the rest of these when the CBV diaphragm comes in.

So with all that said and done, did it fix the problem I’ve been seeing? Well, no. It actually did some things I didn’t really expect. Acceleration from a stop is now much smoother and more consistent as the engine speed increases. Fuel economy on the highway seems to have gone up by one or two MPG, but it is still too early to tell for sure. The most interesting is that the brakes feel much more responsive now. My suspicion is that there was a/some vacuum leak(s) that allowed air into the system causing minor problems, but not enough to make the ECU freak out. Knowing that is more motivation to go back and replace the rest of the hoses, since they surely have leaks too.

However, the top end power is still lacking, so the hunt to restore my engine to normal continues! I was joking with Charles earlier that I’m probably gonna replace everything under the hood short of the engine itself before I fix the problem.. I suppose time will tell. Until then, remember that preventative maintenance is the best thing to do to keep your car performing as it should.