Richo’s Viggen story continues

Posted by swade on April 7th, 2008 8 Comments Printer-Friendly

Time for an update (of sorts) and a query that Richo would like your opinion on.

Viggen This is how Richo’s Viggen looked around a month ago. It was spewing smoke and using oil faster than the Saudis could pump it. I’m not sure what the final diagnosis is, but whilst Richo was initially advised that he’d have to replace the entire engine, it’s now believed to be not quite so fatal.

There’s some burning on the pistons and it looks like they’ll be replaced, as well as something being a little warped and something else being scored. Richo was trying to describe it me but then he’d ask me what part he was talking about - as if I’d know! - so it was a little of the blind leading the naked (I was the blind one).

The engine’s currently in pieces all over the place and one thing he’s been advised is that while they’re replacing the pistons, to use some tougher, forged pistons rather than just replacing them with stock ones again.

Here’s a mangled piston, from Abbott Racing Motorsport.

Saab piston

Richo’s aren’t all busted up like that, but if he just puts stock ones back in there, with the reasonably high state of tune he’s running, then there’s every chance he’ll end up back where he is right now.

So - the question….

Anyone got any recommendations on forged pistons? Any words of encouragement, caution? And especially recommendations as to suppliers. They’d be most welcome.

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WooDz said:

I found this site about a month ago.
It mentions forged pistons in FAQs

http://www.viggenfactfile.de/faq.html

-April 7th, 2008 at 11:30 pm
jeff k said:

Taliaferro has these

-April 8th, 2008 at 2:14 am
Daniel P said:

There are Wössner pistions too..
http://www.woessner-kolben.de/english/indexenglish.html

-April 8th, 2008 at 2:41 am
Andy Rupert said:

At first, I was thinking, “Just do what the mechanic suggested.” But then I read the advice given at WooDz’s link:

A german tuner offered to install Wiseco custom forged pistons, but he told me that usually, 50.000 km on forged pistons would be a lot. It is not the piston that fails in this case, but the cylinder wall. This was backed up by a Wiseco rep I phoned: Forged pistons behave different from standard pistons concerning heat. If the car is still cold, piston tolerance is bigger. This will cause additional horizontal movement on the piston and therefore more wear on the engine. Not good for people using the car for a lot of short trips / city cruising.
Plus, if the piston is very hot, it can “mill out” the piston wall, which is softer than the piston material. Generally speaking, one could probably say that the thermic balance of the engine is “disturbed” by using a forged piston, as the engine block was not designed to work with such a piston in mind.

-April 8th, 2008 at 3:58 am
WooDz said:

My interpretation after most of the tuning tips, is that the best you can do for the Viggen is give the engine as much air as possible to breath and get a very good inter cooler. It seems that the T7 management system relies a lot on what’s happening in the engine itself and that changing pistons and say spark plugs, will end in given the wrong information. In turn running into the probability of the ECU registering actions like knocking well beyond the point of when softer materials would. Basically by using harder wearing parts will likely raise the overall temperature in the engine, causing damage to the block itself.

But as my mechanical skills don’t go beyond a flat battery, maybe someone else would like to confirm my drivel.

-April 8th, 2008 at 4:48 am
Amer K. said:

I have had lots of pistons cracking due to the heat we have here in Saudi Arabia..

Wossner pistons are quite nice, but I’ve liked the JE with coating that is supplied by GenuineSaab.com

We have tried different situations, the best we’ve done at a reasoable cost & what our friend Andy Rupert mentioned regarding heat transfer/thermal conductivity/capacity relation is the following: Use Stock Pistons & Connecting Rods from B234 Turbo Engine, they work quite alright and this method has been used earlier before forged pistons were available for 9-5 Engines as Magnur Uhr from Nordic has told me about 7 years ago.

But Incase you need to take the car to higher horsepower the best thing to do is use a B206 Block which comes without Balanceshafts or a B234 Block ..

Saab has moved to the 5th Generation Engines B2X5, which are much softer engine and as a Step to have cost reduction.

MVH/Amer

-April 8th, 2008 at 8:25 am
Mailr said:

My engine has run >80000 km with JE pistons, thank you. On the other hand the engine is still only at the standard 170 bhp rating. However, I think Wössner is a better choice as a direct replacement as it have better thermal matching and thus allows for smaller tolerences (and thus lower sound).

But in my opinion the first choice for reliability, unless the machine is highly tuned, is to use tried and true B234 pistons and rods. Just don’t forget to switch to a B234 head gasket as well, as a B235 head gasket will result in the valves hitting the cylinders.

-April 8th, 2008 at 11:04 am
szabolcs said:

I have Saab 9-5 2.3T (1999). The piston burns , reaks down after 1000 kilo metres! I exchanged a piston two times already!The sark plug burns after 1000 kilometers.The engine is new!
What should I make?

Thank you!

-August 13th, 2008 at 4:33 am