Boost issues
04-06-2010, 12:04 AM
#1
Boost issues
Hey all, I just discovered something interesting on my turbo and thought I'd share it. For awhile now I was getting boost readings that were below normal and worse erratic. I have K24s, with the Turbo S package on my car (ECU, oil cooler etc). She has been decatted.
She used to hit 1.1 bar peak (I have an external boost gauge) at about 4700 rpm that then dropped of to 1 bar. Then about a year ago the boost started gradually dropping off. Max 1 bar. But what was worse, she'd rarely hit that. Most times I'd get 0.5 - 0.6 maybe 0.8 bar with the attendant drop in power. I thought she was going into safe mode or the turbos were getting tired and had her in the official Porsche dealer here who told me they detected no fault codes but thought she was running lean from a manifold leak. They tightened up the headers but no diff.
Over the weekend, I had the intercooler off and had a poke around with a plan to installing a manual boost controller but was struck by what appeared to be the boost vent hose that came of the frequency diverter valve having collapsed. It does a fairly tight 180 kink up off the FDV before heading off to the intake tube that lead to the turbo inlets. And the hose looked like it had gone flat right at the peak of the kink. I pulled the hoses off (quite a pain as the factory clamps are crimped on) and put in some silicone hoses with plenty of room to prevent a repeat of the collapse.
I had her out this morning and man was I taken aback! I had forgotten how strongly she could pull when she hit the above boost levels
The boost came on strong and much earlier and I was now hitting the boost levels I first had. That vent hose has to remain open, if not it's as if the valve was shut and allowing full manifold/turbo pressure to act on the wastegates ie. safety boost mode instead of being bled off.
Hope the above is clear. I can take pics if needs be...One more thing to check if your boost levels aren't what they should be
cheers,
Kris
'97 993 TT
'03 X5
She used to hit 1.1 bar peak (I have an external boost gauge) at about 4700 rpm that then dropped of to 1 bar. Then about a year ago the boost started gradually dropping off. Max 1 bar. But what was worse, she'd rarely hit that. Most times I'd get 0.5 - 0.6 maybe 0.8 bar with the attendant drop in power. I thought she was going into safe mode or the turbos were getting tired and had her in the official Porsche dealer here who told me they detected no fault codes but thought she was running lean from a manifold leak. They tightened up the headers but no diff.
Over the weekend, I had the intercooler off and had a poke around with a plan to installing a manual boost controller but was struck by what appeared to be the boost vent hose that came of the frequency diverter valve having collapsed. It does a fairly tight 180 kink up off the FDV before heading off to the intake tube that lead to the turbo inlets. And the hose looked like it had gone flat right at the peak of the kink. I pulled the hoses off (quite a pain as the factory clamps are crimped on) and put in some silicone hoses with plenty of room to prevent a repeat of the collapse.
I had her out this morning and man was I taken aback! I had forgotten how strongly she could pull when she hit the above boost levels
The boost came on strong and much earlier and I was now hitting the boost levels I first had. That vent hose has to remain open, if not it's as if the valve was shut and allowing full manifold/turbo pressure to act on the wastegates ie. safety boost mode instead of being bled off.
Hope the above is clear. I can take pics if needs be...One more thing to check if your boost levels aren't what they should be
cheers,
Kris
'97 993 TT
'03 X5
04-13-2010, 02:41 AM
#4
Hey guys,
Sorry for the late reply but I could only get around to taking pics over the weekend!
I can't seem to insert a pic. Any advice?
cheers,
Kris
'97 993 TT
'03 X5
cheers
Kris
Sorry for the late reply but I could only get around to taking pics over the weekend!
I can't seem to insert a pic. Any advice?
cheers,
Kris
'97 993 TT
'03 X5
cheers
Kris
04-13-2010, 02:45 AM
#5
Hey guys,
Sorry for the late reply but I could only get around to taking pics over the weekend!
I have attached the pic here of the problem area. Only thing is the manual boost controller (MBC) that I have plumbed in might confuse the issue.
The circled area shows where I have plumbed in the mbc. The black hoses shown will in a stock car be one continuous length.
That hose rises off the frequency diverter valve (FDV) then kinks down (a 180 degree U). On my car, the peak of that U had collapsed and I was getting safety boost as the boost pressure to the wastegates wasn’t vented by the FDV. I had installed the MBC thinking there might be a problem with the FDV but the MBC is cranked shut while I am still getting my original boost and power levels
Hope this helps!
Cheers,
Kris
'97 993tt
'03 X5
Sorry for the late reply but I could only get around to taking pics over the weekend!
I have attached the pic here of the problem area. Only thing is the manual boost controller (MBC) that I have plumbed in might confuse the issue.
The circled area shows where I have plumbed in the mbc. The black hoses shown will in a stock car be one continuous length.
That hose rises off the frequency diverter valve (FDV) then kinks down (a 180 degree U). On my car, the peak of that U had collapsed and I was getting safety boost as the boost pressure to the wastegates wasn’t vented by the FDV. I had installed the MBC thinking there might be a problem with the FDV but the MBC is cranked shut while I am still getting my original boost and power levels
Hope this helps!
Cheers,
Kris
'97 993tt
'03 X5