15" to 17" or turbo problem ? - SaabCentral Forums
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NG900 & OG9-3 Workshop NG900 (1994 to 1998) & OG9-3 (1999-2002) & '03 Convertible Technical Forum

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  #1  
Old 21st July 2005
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Default 15" to 17" or turbo problem ?

Hi gyuz,

My 1999 9-3 always had a pretty good turbo kick. A friend of mine who own a 9-3 same year already try my car and told me : Man your turbo is kicking a lot when the gauge is in the middle/far yellow and red.

Since iv'e change my wheels from 15" to 17" I notice a BIG BIG change in the performance. The car is defenitely slower.

The same friend juste re-tried my car and make me notice that now, the turbo gauge was never going into the yellow area ...

Is that normal ? Can the fact of the wheel are bigger can prevent the turbo of running at he's full pressure ?

It should'nt have anything to do right ? My turbo should not kick as hard at it was, but the gauge should still go into the red, right ?
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  #2  
Old 21st July 2005
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BLE 9-3se BLE 9-3se is offline
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The wheels will make your car feel a little slower, but wouldn't affect how the turbo guage reads, or the amount of boost the turbo provides. When I went from 16's to 17's, the kick in the seat of the pants was definitely lessened due to wheel diameter. However, the car looks and handles noticeably better, which is in my mind, a good trade.

There's a lot you can do to get your minimal power loss back. Check the forums for ideas on that.

Keep an eye on your exhaust for blue or white smoke when you come to a stop sign after you've been driving for a while. If you see more than what you think you might see from your regular exhaust, your turbo might be failing. That's what happened to me.

How many miles on your car?
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  #3  
Old 21st July 2005
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110K Kilometres ... (+- 66k miles)

Dont remember seeing any smoke OUTSIDE the car ...
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  #4  
Old 21st July 2005
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Question

I am a little confused to as why the performance would suffer from going up a wheel size? Did you guys not get a tire that kept the original wheel/tire diameter? So the overall diameter is bigger? Not sure what else it could be ...

Just curious if I am missing something because my 18" just came in but the overall diamerter is going to be the same as my stock 16". So I wouldn't expect much change in power performance.

(Flame away on bent rims and ride quality, I've heard it all )
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  #5  
Old 21st July 2005
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Compare the weight of your 16" VS your 18" ...

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  #6  
Old 21st July 2005
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Well, there are 2 reasons that bigger wheels will slow you down, though they're kind of tough to separate.

The first is that bigger wheels are generally heavier than smaller wheels. This means that the engine has to turn a heavier wheel just to make the car move. Weight gained here has many times more effect than weight gained on a non-rotational part of the car..

The other, oft-neglected reason, is that the weight of the wheel is concentrated even further outward on the wheel. Meaning that that there is a bigger 'lever arm' or moment of inertia. Even if your 16" and 18" wheels weigh exactly the same amount, the weight is located closer to the outside of the tire, making the wheel harder for the engine to turn.

None of this will change the amount of boost you're making. This is a definate problem that needs to be addressed.

Reminds me of my friend. His SVT contour had it's secondary runners (think big throttle plate that opens at higher RPMs, like a 4 barrell carbeurator) freeze up and stop opening at about the same time he got bigger wheels. But he didnt know this was the case. I drove his car and said it now felt like a corolla. Well, in reality, it was probably breathing through holes smaller than that of a corolla.
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  #7  
Old 25th July 2005
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Hummmm what should I check first ?

Any small advice for troubleshooting ... ?

Thanks.
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  #8  
Old 25th July 2005
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If the turbo boost is not even getting past the beginning of yellow, first likely reason is a big air leak. I would look somewhere between compressor and intercooler, intercooler and delivery pipe, BPV, or at the throttle body. You might be able to hear a leak if someone revs the engine while you listen for a whistling sound with the hood up. Next, BPC malfunctions can make the waste gate open too soon and prevent maximum boost from being reached, and finally my favorite, vacuum line cracks and leaks...

In order of my own preference in looking for performance/boost issues:

1) Reset ecu and let it re-adapt with a few on-boost runs up a hill or empty road.
2) Plugs, air filter, injector cleaner and other tune-up items.
3) Replace vacuum lines, inspect PCV valve and evap purge hose.
4) Inspect all turbo, intercooler, BPV and delivery pipe connections and clamps, tighten as needed.
5) IAT sensor, manifold temp sensor, front O2 sensor, BPC malfunctions can also affect boost.

Last edited by PMI; 25th July 2005 at 11:03 AM.
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  #9  
Old 29th July 2005
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Ok, It's confirmed, I do have an air leak.

I can clearly hear it.

But Jeez, how the heck do you localize an air leak ?

I heard Ffffffffffffffffffffffffff, near the TB but everything *looks* fine ...

Any tricks to localize an air leak ?
Is there any danger of using the car ... ?

Thx...
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  #10  
Old 29th July 2005
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How do you know you have an air leak? There's an aweful lot of hissing and ticking sound which is all normal. Get a 1/4" flexible plastic hose, and use it as a stethoscope. Move it around and near all vacuum hoses. Get use to all the sounds and you may even want to slightly leak one so that you can train your ears to the sound of leaking vacuum.

If you really suspect that there's a leak, take it to a garage that has a fog machine and they can do an induction leak test.
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  #11  
Old 3rd August 2005
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It was the cutting pin ... Well it was the lack of the cutting pin lol!!

Now back top normallllll Pffffffff****tttttt

Sweeeeeeeeeet baby is back home!!!!!!!

Thx all.
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