Clipping Turbine Wheel
03-16-2002, 11:50 PM
#1
Clipping Turbine Wheel
I have a k27/8 turbo that I plan to have installed on my 89 951 in the next month or so. I have heard that the k27/8 turbo tends to build backpressure in the exhaust and am wondering if clipping the turbine wheel will help. Has anyone done this?
03-17-2002, 01:05 AM
#2
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Location: California
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I do not recommend clipping this turbine. I have an 88 Turbo S and I have re-turboed with a clipped 26/6 because the lag was quite awful with the stock 2.5L motor.
The 27/8 has minimal backpressure and you already have selected a turbo with a lot of lag and a lot of top end.
I strongly suggest your talk to Tim or John at SFR for the real scoop. Reliable, excellent products, and truthful to a fault.
The 27/8 has minimal backpressure and you already have selected a turbo with a lot of lag and a lot of top end.
I strongly suggest your talk to Tim or John at SFR for the real scoop. Reliable, excellent products, and truthful to a fault.
03-17-2002, 07:33 AM
#3
Race Director
Well, it depends on upon the boost level you're going to run. Up to about 15psi of boost, exhaust backpressure is manageable at 8-10psi. But if you start using 18-20+psi of boost, the exhaust backpressure can increase to 45psi+. Not a good scenario as you end up using precious boost to force out the exhaust.
03-17-2002, 04:25 PM
#4
Danno: That's what I understand happens with these turbos. Isn't that also the reason boost drops like a stone at high rpm? I was just wondering what clipping the turbine would do. Does it affect lag? Would it help relieve exhaust back pressure?
03-22-2002, 11:37 PM
#5
I just spoke to a local turbo shop about clipping the turbine on my K27/8. They recommended it to a) allow better exhaust flow at high boost levels and b) reduce heat build up. They told me that clipping will not negatively affect lag. They said that the front edge of the turbine is what drives the turbine and that the trailing edge evacuates the gasses. I asked why the stock turbines were not clipped to begin with and they said that a turbo tends to pull the shaft one way and the slightly rounded edge of the turbine counteracts this. Does anyone have any experience with clipped turbines on a k27/8? I'm just looking for a method to help reduce exhaust backpressure at levels between 15 and 20 lbs so that my boost curve doesn't fall on it's face. Without changing turbos of course......
03-23-2002, 02:16 AM
#6
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my k27/6 makes 22 PSI and stay there (or go even higher) as long I want.
It made 3.9 sec from 100 to 150 km/h There is almost no lag over 3000 rpm at at 4000 is much better than any NA car including the GT3 Cup car.
with a MAF and a good wastegate hold the high boost is not a problem.
Konstantin
It made 3.9 sec from 100 to 150 km/h There is almost no lag over 3000 rpm at at 4000 is much better than any NA car including the GT3 Cup car.
with a MAF and a good wastegate hold the high boost is not a problem.
Konstantin
