Ever wonder how much a blown turbo hurts power output?

[servion]

Well, I previously posted the dyno chart from my personal car about a month or two ago. When I did that dyno, I simply unplugged my boost controller (which, with my current controller, causes maximum boost). That's the blue line. The turbo had significant axial play (in and out, i.e. from hot side to cold side), but very little up and down play.

The red line is the same car (same setup) with basically everything the same except that the turbo was rebuilt and the car was retuned. The boost was also controlled with the boost controller still in place, so the new red lines are on less boost (I would guess 2-3psi, but its hard to tell because of the large difference between gauge pressure and absolute pressure here). I'm estimating a total of 22psi total solid boost.

The new pull goes to around 9.5k, I would have liked to pulled it to 10k or further; I'll think try that next time out =)

http://www.serviontuning.com/images/Tunes/servion.jpg

The tune changes were more drastic than I expected them to be. Anyway, I thought you all might be interested to see the difference from a turbo rebuild. The turbo wasn't even spitting up significant oil or anything like that; it just had some axial play that I wanted to fix before it got bad enough to cause the wheels to hit the housings.

[ryanman]

damn

[Aracheon]

Wow... :o

[Nate]

So you're saying there's a difference?

[servion]

Hahah, yes there is a big difference. See the shape and duration of the red torque curve at less boost?

[doctorstupid]

The reason for that is the side clearance in the compressor wheel, as the wheel moves awawy from the compressor housing those clearances get quite large (relatively) and the turbo's output just plummets. This is also, in part, the reason that larger compressors are almost always more effecient than smaller units, as the wheel size increases, the clearances stay the same, but they become smaller relative to the wheel size; giving the larger compressor an advantage.

But I digress, I've never seen it shown on a dyno, good post :)

[servion]

The reason for that is the side clearance in the compressor wheel, as the wheel moves awawy from the compressor housing those clearances get quite large (relatively) and the turbo's output just plummets. This is also, in part, the reason that larger compressors are almost always more effecient than smaller units, as the wheel size increases, the clearances stay the same, but they become smaller relative to the wheel size; giving the larger compressor an advantage.

But I digress, I've never seen it shown on a dyno, good post :)

That makes perfect sense. I wish I could post some more data (i.e., how bad it was like a specific clearance) but I don't have that data. I can say that the amount of axial play surprised me enough to drop teh turbo and send it off mid-season.