[Chris 9-5]

Can I ask at what power levels these become essential?

I have read a lot saying our pistons are weak but I cant find a single post of a piston failure due to "too much power"

On another forum a guy has just decided he cannot go more than 300 bhp as if its a well known fact - but is it?

Come on, where does this urban myth come from??

 

[Raven18940]

Can I ask at what power levels these become essential?

I have read a lot saying our pistons are weak but I cant find a single post of a piston failure due to "too much power"

On another forum a guy has just decided he cannot go more than 300 bhp as if its a well known fact - but is it?

Come on, where does this urban myth come from??

The fact that B2X5 pistons are cast (not forged) unlike every other turbo piston that has gone before it. They say that the 2.3 can handle 300 and the 2.0 can handle 350.

 

[Chris 9-5]

They say that the 2.3 can handle 300 and the 2.0 can handle 350.

Ok but who is "they" and where do "they" say it

 

[Raven18940]

Ok but who is "they" and where do "they" say it

Jak Stoll said it on Saabnet. *shrugs*

I don't know man, how far are you with your mods. Maybe you can prove them all wrong.

 

[Chris 9-5]

Maybe you can prove them all wrong.

Well some one must have proved them right in the first place surely

Are we talking running flat out on a track all day?

Are we talking about damaged caused by running lean due to poor software or hardware specs?

Or are we saying, if your car has 400 bhp the pistons will just plain explode

 

[Gazolzwurf]

Something to read here
From viggenfactfile

Don't expect a conclusion. Seems like a fair amount of research has been carried out at 'viggenfactfile' and still there is no definitive answer.

Makes for a good read.

 

[Chris 9-5]

Yep good stuff!

So he's saying that the pistons are potentially weak at any power level possibly due as Raven says to their cast design...........

There are rumors on the internet that B235R pistons are weak and only good for up to 300 hp. This is also believed to be the reason why Hirsch limit their cars to 305-310 hp. However, there are a few B235R cars out the with far more power, running fine for quite some time now. I.e. Hirsch´s own Tuner GP car with 324 hp and Ollin Ruosaaris Viggen with more than 340hp.
To cite Ollin: Generally speaking, what will work for one will not work for the other. For instance one Hirsch employee wrote on the swedish Saab board that they ran a B235R engine up to 400hp with out failure, but at the same time there are people who have had failures with standard power levels. What does this tell us?
There are other variables within the B235R construction besides the physical piston itself that will lead to the "known" failure. Is the B235R more vulnerable to piston failure with 350hp than 250hp? We know the both can fail. Out of all the tuned B235 piston failures how many would have broken anyways? WE DO NOT KNOW.

 

[Raven18940]

Yep good stuff!

So he's saying that the pistons are potentially weak at any power level possibly due as Raven says to their cast design...........

It's not so much that it's cast, but not as "substantial" as previous designs. Put a B234 and B235 piston next each other and you'll get the picture, there's just a lot less piston to a B235. Perhaps this leads to the piston overheating more easily, who knows, it could just be a flawed design or bad construction process. Whatever the reason they fail, the reason they chose those pistons is simple, they weigh less. If you've done any research into the forces inside a piston engine, the greatest stress on a piston is an TDC after the exhaust stroke as there's no compressive load on the piston at this point. This stress is an acceleration rather than a force. So by lightening the piston, they greatly reduce the stress on the rotating assembly. This is the reason the B235 revs to 6500 rpms stock, more than any previous saab.

Anyway, the part of the piston that "fails" is the piston crown, the top bit. If it fails you won't have a hole in your block, you'll just lose all compression on the cylinder. So if you wanna know the limit, go and find it.

EDIT: I wanna go and build a 9000 with B235 pistons and ring its neck just to see what happens.

 

[DoctorPhill]

Horror tale

So,is it means that my new forged pistons will ruin my engine for few months?????:roll:
50 000km isn't much-anyone with forged pistons already?

 

[SectorNine50]

So,is it means that my new forged pistons will ruin my engine for few months?????:roll:
50 000km isn't much-anyone with forged pistons already?

What? No, your forged pistons won't ruin your engine... am I misreading this?

The forged pistons are much stronger and can withstand loads more power.

 

[Raven18940]

The forged pistons are much stronger and can withstand loads more power.

But that's exactly the problem, they're too hard and can eat the cylinder wall. And there's also the cold startup problem, forged bits have to expand more so the tolerances are really wide when cold.

 

[DoctorPhill]

Damn

But that's exactly the problem, they're too hard and can eat the cylinder wall. And there's also the cold startup problem, forged bits have to expand more so the tolerances are really wide when cold.

Yes,but does the piston itself contacts with cylinder wall????
What about the rings-I've always thought that just the rings touch the wall.

 

[SectorNine50]

Yes,but does the piston itself contacts with cylinder wall????
What about the rings-I've always thought that just the rings touch the wall.

Me too, I'm a little confused now. Are the rings built into the piston on the forged ones or something?

 

[Jssaab]

But that's exactly the problem, they're too hard and can eat the cylinder wall. And there's also the cold startup problem, forged bits have to expand more so the tolerances are really wide when cold.

I have heard of this but my forged pistons are silent ( knock wood) but there are reports that longer skirts can tend to hit against the cylindar walls a bit when the engine is cold ( goes away as they or the bolck expands)

The Wossner forged psitons are the exact same weight as the non-forged orginals ( but the B2X5 are heavier that is true) tested its true...

Well some one must have proved them right in the first place surely

Are we talking running flat out on a track all day?

Are we talking about damaged caused by running lean due to poor software or hardware specs?

Or are we saying, if your car has 400 bhp the pistons will just plain explode .

Naw wont' explode just will not hold up to the forces that raven described so eloquently. Nick T has cracked a piston at 325 BHP I think. One of the reasons Hirsch only goes to 304BHP is this concern. In general its better to run stronger over 300HP. (unless you are in a B2X5 then jack stoll only cracks them at 500HP)

 

[DoctorPhill]

There were 3 slots and 5 rings with my Wossner pistons and working gap was same as standard.

 

[SectorNine50]

There were 3 slots and 5 rings with my Wossner pistons and working gap was same as standard.

What does that mean?

Don't know much about the technology behind pistons... ;oops:

 

[paolo]

Well what does Nordic say Chris?

• Maptun go up to 315bhp on stock pistons, their higher stages use Forge.
• Abbott use forge at 320bhp
  

The above seems to fuel the 'myth' especially with an aforementioned post re: Hirsch - that makes 3 major tuners.

Maybe a current customer can ask them for the reasons?

When I change my exhaust housing on my 18t to a no.6 Nordic state my car should reach 320 easily - no mention of forged from them?

(But then again I ruin pistons at 5mph with Allen Keys so what do I know!):cheesy:

 

[DoctorPhill]

Rings

I'm in the fog also,here is how they look:

and

.
Also for 9-5 I've been told that they are much lighter than stock and the skirt isn't longer.
The set I've bought from Abbott were with some kind of side coating.

Abbott even recommend them for above 280 for 2.0 L and 300 for 2.3L engines.Wossner for 2.0 L were harder to find and I decided to do conversion also.
The Iconic 9000 Aero doesn't have forged pistons,but there are"Invar" disks
built in and they are much stronger than 9-5 and bit heavier also.
Replacing 9-5 pistons with these from 9k Aero is budget saving option and tech guys told me that they can handle up to 440-450 Hp-more than enough.
900Ng turbo and may be Viggen have forged from stock?
I hope that my new build Aero engine will run long time for me.

 

[Vigge]

I would put it this way,

if you wish to really TUNE the B2x5 engine get the pistons since you will need them sooner or later, either because of bhp or eliminating the "statistic proven risk of failure" Writing limits to what they hold is no use since the scale is pretty much from 200bhp to 400bhp, i.e failures happen. So the "magic" ~300bhp limit does not make much sense.

As much as I have spent time among various saab forums, I have yet come over information which would clearly point out that the risk of piston failure increases dramatically once the bhp level is raised to 300+. Out of all the piston failed engines the majority are with std output, since the quantity of them is large. Then we have these examples of who cracked a piston and at what bhp, but how on earth can you differentiate the cause to be bhp raleted instead of the normal "statistic failure"?

Personally I did run my car with a 330bhp tune for almost a year before I put in JE's and power adding parts (aim was set to bhp levels which the std pistons cant handle for sure) The use in my case is hevy, car is spanked on daily bases on the road, including looooooooooooong WOT runs + few times a year airfield fun and without failure, nor any faults where found in them when I gave them up.

There are many cars in Sweden running similar BHP and more and they seem to hold as well. For instance this car sees strip often and has seen for the past 2-3 years.
http://www.maptun.com/cars.php?id=132
best et 12.7 best trap 180km/h

but as stated if you want to eliminate the risk wheather it due to bhp or statistics its good to do the upgrade, since the piston failure can end up damaging other parts as well leading to a much larger repair bill.

 

[Vigge]

But that's exactly the problem, they're too hard and can eat the cylinder wall. And there's also the cold startup problem, forged bits have to expand more so the tolerances are really wide when cold.

How many saab do you know from real life with forged pistons? and do any of them suffer from the problems you mention?