My car boosts up to 1.0 bar and as the rpm rise the boost drops off towards .9 or .8. Sometime the car doesn't get to 1.0. I am trying to figure out if this maybe due to the Bosch diverter valves which were changed back in 03. They are now going on 7 years. Also when I start the car from cold, I hear a "skill saw" type sound which seems to go away after a little while. Is that the famous "honking sound" which means a tear in the diaphragm? I realize swapping diverter valves maybe the solution to this boost bleeding, but I also like to diagnostic things properly instead of merely throwing parts at the car and see what works or not. Car is a 2001 with a RUF kit on. Thanks.

 

What do you mean by "RUF kit" ? - Engine or Body upgrades? - and what other mods are you running? A quality set of billet DV's should accompany any ECU tune, you'll keep replacing the plastic/rubber Bosch units if you stick with them.

 

That skill saw sound you hear is most likely the secondary air injection pump. It shuts off after few minutes when engine warms up.

 

Yes Ruf engine kit. Exhaust turbos and ecu sent back to Germany. Ruf intake manifold, and bigger diameter hoses from the intake manifold tot he compressor side of the turbos. Will aftermarket diverter valves keep the boost steady at 1 bar, or is it something that needs to be handled via the wastegates? I am trying to figure out how to hold the boost level steady all the way to red line, instead of it tapering off. On my previous car, Evo 9, this was accomplished by "using a calibrated boost hose assembly which allowed the tuner to modify the wastegate ecu maps. " And I am not sure that the diverter valves are the culprit in my case. I have been wrong before though. Excellent on the skill saw noise. I'll leave that one alone. Thanks.

 

Boost leak check, cap off at compressor inlets and pressurize

 

There are a couple of possibilities. Did your car used to maintain 1.0 bar all the way up to redline, and now it doesn't? If that's the case, then you probably have a boost leak, which could be diverter valves, leaks at the boost hose junctions, or other places. A pressure test could help you locate those. Seven years on the DV's - they probably are due for replacement.

If your car never maintained 1 bar up to redline, that is probably because the tune has backed off the boost at higher rpm. If the fueling hasn't been upgraded, you may be running out of fuel, and increasing the boost is just going to push more air through and make the car run lean. That can lead to detonation problems.

I'd suggest hooking up a Durametric and doing a few runs at WOT from 2000 rpm to redline to see what your engine is doing.

Jon

 

I have done the boost leaks checks from both the maf side and the compressor side of the turbos. In both instances I found boost leaks. One was the F hose which had a slit and both junctions at the intercoolers needed cleaning and proper fitting. Could not find a leak at the DVs. The leaks are now gone. Since I have owned the car, I have never seen it do anything but occasionally hit 1.0 Bar and then taper down towards .9 or .8 bar. This is what leads me to believe that may be the way the tune is set up. I did test drive a car while I was shopping which held boost at 1.2 steady to red line. What I am really trying to do is to make sure, the car is operating as it was intended by Ruf when tuned back in 2002. I started logging in recently. I am looking at rpm, intake air temperature Ignition angle, actual throttle value, boost pressure of sensor and set point boost pressure. I should be looking for a trend that shows if the boost actually goes down as the rpm rise. Is that right? Thanks.

 

What size turbos?

Can K16's even boost 1bar to redline?

 

I don't know what Ruf did to the turbos back at the workshop in Germany. I am going to try and figure out how to test the wastegates and see at which psi they trigger to open. Ruf may also have changed the compressor wheel on the turbos? We are talking 2001/2002 technology. Things have progressed quiet a bit since. AMS billet wheels on K16s etc... I pulled the id #s on the turbo, passenger side.

996 123 013 75
EF 504 1332 88052
5316 990 6726

Is this a stock KKK ID for a 2001 turbo?

 

That looks like a K16 part number

 

Ok,
so this may mean that Ruf does not modify the turbos, but maybe does something to the wastegate?

 

I suppose that Ruf could modify the turbos and not change the part number!

You need to find out what you have first.... won't Ruf give you the specs on what was done?

 

Is there a standardized procedure for checking proper boost pattern and level? By this, I mean, is there a specific gear I should be doing the WOT runs? At what RPM should I be seeing X amount of boost? Haven't had my Turbo for long and would like to test and see if it is boosting normally.

 

3 gear and WOT

 

Yeah, these cars are a plumber's nightmare. If the DV's are leaking internally, you might not see it in a pressure test. In my car, we disconnected the vacuum hose to each DV, pulled a vacuum with a hand held brake bleeder vacuum, and one of them wouldn't hold vacuum.

Try looking at the fueling. Log the O2 sensor lambda values on both banks (multiply this number by 14.7 to get air/fuel ratio), and Injection time (multiply this value by rpm/1200 to get injector duty cycle in %). BTW, to convert the boost pressure to bar : (Boost - Boost at idle)/980. Subtracting the first pressure logged offsets for whatever is the local barometric pressure that day.

I prefer to datalog in 4th gear, since you don't get as much data in 3rd gear, especially if you collect a lot of different quantities. Top speed is higher though, so you have to have someplace to do it.

Jon