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Discussion Starter · #1 ·
Hi folks, as some of you know my results on the recent Scottish Rolling Road day were disappointing. Power maxed at 222.8BHP at 5000RPM and Torque maxed at 286.6Ib/ft at 3000rpm but dropped away rapidly after that.
Basically, I'm driving a standard Aero despite my numerous mods.
Took the car back to Dastek today to investigate the problem.
They did a compression test on my cylinders which came up with the following results:
1 175
2 150
3 150
4 150
However a leakage test came up with:
1 10%
2 60%
3 30%
4 40%
Apparently, anything up to 15% is acceptable so I have a major problem in there. Question is, is it the piston rings or the bottom end?
How big a job is it to identify and remedy this?
 

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I'd say it's a top end problem mate, I had the same with mine! Good compression readings but a poor leak test
when the head was ripped off no visible signs of any damage until the pistons were removed showing one had departed company with it's skirt rings and all The car drove right apart from a decrease in power and the usual puff of blue smoke.
Hope things work out well for you
 

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Would suggest its a top end problem. I have had the same results in my Ferrari. Good compression poor leak down results. Cause of problem worn valve guides. I feel you will have to strip engine down to investigate. Top end strip down not difficult on a 9000. Good luck
 

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150 is "good" compression?

My B235R tested at 215 in every cyllinder. Different conditions though.

Hmmm ...

With a tuned engine I would worry about piston rings. They are known to get damaged before the pistons if you have any detonation from a less-than-ideal tune, or gas.

Adrian W~
 

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It does seem that the 9000 head gasket tends to go from the No. 4 end first. If you have no overheating problems it might be an idea to have the head retorqued to see if that helps. I don't think there's anything to lose. If it doesn't work, you need to have the head off but as it stands, that's the only other course of action anyway.
 

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Discussion Starter · #6 ·
Bill, I had the head retorqued at Abbott last summer so I doubt that it will help.
I guess I'll have to emulate the guillotine and have it's head off.
 

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Well, you're going to have to get the head off whichever way... and you can then drop the sump (with a bit of fiddling) to drop a new set of piston rings in. If you're planning on keeping the car, the incremental cost for doing the rings at this point is relatively low.
 

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one thing I noticed at the RR day was a little blue smoke on start up
This would indicate that you are burning oil rather than displacing it
my guess would be piston rings which are unusual for a relatively low milage car
maybe some abuse when it was younger ?
Taking the head off may not tell you but it is the first step to tear the engine down if you are going to do the piston rings anyway...
 

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Discussion Starter · #9 ·
At 115k miles my mileage is only low in comparison to yours
I believe that the previous owner was an enthusiastic driver.
If the head is coming off anyway, should I be looking to change anything else as a preventative measure, ie the gasket?
 

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Originally posted by Gordy:
[qb]If the head is coming off anyway, should I be looking to change anything else as a preventative measure, ie the gasket? [/qb][/b]
What is the actual mileage Gordy? Might it be worthwhile going for a full belt'n'braces approach at this stage, i.e. new gasket, chains, guides, sprockets & oil pump. Assuming that the bottom end does appear to be OK?
 

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Does the engine breath heavily Gordy? try running it and take the oil filler cap off to see. Either way a strip down is in order but it may give you a clue Oh and are you talking about the head gasket needing to be replaced? if stripped down
 

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Hi Guys, I see a lot of talk about removing HEADS and looking at pistons, If your going to romove the head you MUST change ALL the gaskets, have the boares checked also, feel if there is any movment in the pistons from side to side, this may take a bit of prussure, if the rings are gone it will be easy to seee movment from side to side, VALVE Guides, to check these you may need to remove one or two also have the head checked, it my need a scim of 1 oe 2 tho.

Goor luck, but remember if you do thinks on the cheep don't be P*&&ed off when it brakes.
 

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Discussion Starter · #13 ·
Oh woe is me, I am cursed by the gods.
To bring you all up to date: To address the problem detailed above I ended up having a new short motor installed. There was nothing obviously wrong with the piston rings etc and, keeping in mind Saabs warning about rebuilds, I wanted to be sure that I had no future problems.
In went a new short motor complete with timing gear, new clutch, various other bits and bobs. When the car was returned to me it was overboosting wildly so I had the boost turned down.
Having now run in the car, it was back to Dastek today for some fine tuning, to have them reset the boost back up to Abbotts 1.35bar while checking fuelling and all that good stuff.
Unfortunately, the good people at Dastek have now discovered another problem. At anything above 1.2 bar, at 5k rpm the engine starts misfiring and power drops like a stone.
I'm desperately keen to find a simple (and cheap) solution for this and I'm hoping that folks might recognise this as a problem with the DI Cartridge or something equally simple. Please, please, please make some comforting noises and soothe my frayed nerves.
 

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Originally posted by Gordy:
[qb] At anything above 1.2 bar, at 5k rpm the engine starts misfiring and power drops like a stone. [/qb][/b]
I'd start with the DI cartridge, sounds most likely.

The other remote possibility is worn valve springs/cam lifters, but like I say, start with DI first
 

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Originally posted by Gordy:
[qb]I'm hoping that folks might recognise this as a problem with the DI Cartridge or something equally simple.[/qb][/b]
I agree with Mark - it does sound very like a DI failure, which would become worse with both increasing boost and increasing RPM.

It could even simply be down to the wrong plugs or incorrect plug gap.
 

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Discussion Starter · #16 ·
Excellent guys, thats exactly the kind of comforting noises I was looking for. Bill, It's interesting that you mentioned plug gaps as, based on Dasteks recommendation, I had them reduce the gap from the standard 1.1mm to approx 0.75mm. I've seen posts elsewhere on the site that talk about doing this so I reckoned it would be OK, was I wrong?
 

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0.75mm is way too small. The smallest I've ever known run is 0.9mm.

DIs run best at 1.1mm. I'd try a re-gap first.
 

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Actually, from my experience, the plugs should be on the tight end for high boost operation. I usually run .9mm on mine. When my first DI had about 100k on it, I had put plugs in and decided to try 1.1mm. The DI started the misfire that day, on the way up to the Ring. I can imagine that at high boost and revs, the load on the DI would be much higher, and an increased gap would only work it harder.
 

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OK, I'll add a qualifier

New, unworn DIs run best with plugs at 1.1mm. Remember they're not just producing a spark, they're also being used for measurement (including knock sensing IIRC) so if the gap is not in spec, it alters the measurment too.
 
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