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Discussion Starter · #1 ·
On the 'other' bb? There was an interesting thread about B235 pistons. It certainly adds to the 'conspiracy' theories running about these days My favorite is that the B234 was the more over designed motor, and once the GM bean-counters' ethic took hold, more 'practical' pistons would be used. Anyway, the message from the threads seem to imply that if one is going to tune an engine, the B234 is 'the' one - the B235 cannot be safely tuned above 300 hp with the stock pistons.
 

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It's a very interesting thread. Makes me wonder if my B204L pistons are more like the ones in the B234R or the B235R.

Don't want to end up like this:
 

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Phillip with the 9-3 Viggen 'vert also sent me a PFD file that I can't seem to open. (Need to update?)

It says that at some point during the MY 2000 run Saab realized that the B235R's cast (at the time) pistons were not up to the job, and switched back to a forged design.

At any rate tuning above 300 bhp would be done more safely with a lower compression than either the B234 or B235 have stock.

9.3:1 is ok for 300+ hp, but you're going down a road of diminishing returns. You can get more power out of lower compression, but with increased ignition timing. On pump gas anyway ...

... besides ... upgrading the pistons is never a bad idea anyhow. I'd be pulling them out to ceramic coat mine anyway, and if shooting for 300+ hp the cost of a new set would be relatively small in contrast.

Dubbya~
 

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Got the file to open finally! Turns out from the year 2000+ the following mods were made to the B235 engine:

-New exhaust camshaft
-New, reinforce pistons
-New nitride hardened wrist pins
-New Sturdier connecting rods, with trapezoidal small ends. This shape increases the wrist pin surface area use on the power stroke.

In the 2000+ Aero engine a new oil sump was fitted to reduce noise.

Also from year 2001+ the base engine (B235E) received the Nimonic exhaust valves, reinforced pistons, and other modifications previously reserved for the "R" engine.

While there have been a couple cases of owners failing pistons on year 2000, it's possible that either ...

a) it was an isolated incident (tuned too aggresively or had a faulty knock sensing system)

or ...

B) they altered the pistons at some point in the MY2000 run, and simply don't specify the exact date ... it may have also been on a B235E engine, which didn't receive the reinforced pistons until MY2001.

Also in 2000 they switched away from the "air flushing" injectors used on the MY1999 B235 engines.

Dubbya~

p.s. If it's ok with Phillip HS (the person who sent me the PDF file) anyone who'd like to see it can PM me their e-mail and I'll send a copy. Other than the information listed here, there is little more information of importance in it that I saw.
 

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So does this mean we are under the assumption that MY 2000 should be ok? That is what I am buying so that would go some way to putting me at ease. Adrian, I would like to see that pdf. PM sent...
 

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Hey guys - my first post here. I came across this thread and figured I should post. It was my Viggen that had the piston crack mentioned on saab net. It's an '01 with ECU tuned to SQR stage III specs, 3" DP and all the way back. Spearco fmic and K&N air filter. Those are the mods, I had it dyno'd at 255whp/301ftlbs of torque at the wheels the week before it blew.

The A/F ratio was 12:1 to redline, it hit 18-20 psi, settled to around 15-16 at high rpms. Then she blew. I didn't know of the piston issues and the 300bhp/350 ftlbs limitations until it was too late.

So as a note of caution - watch the B235R's if you're gonna tune them. I don't think it was a knocking/detonation issue. I had felt the T7 reduce timing and seen it reduce boost on hot days so I assume it was doing its job, unfortunately I don't have any diagnostic tools available to monitor those signals.

Well, I'm about to go get a new motor and put the stock ecu back in for now, and get to rebuilding the orig one, if its salvageable.

cheers,

-Steve
 

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Well I want to make sure that we're scientific about this. Otherwise owners may shell out lots of money for pistons that they may or may not need. So let's rule out some things ...

1. Spark plugs are essential to the Saab's knock detection system. What kind and mileage were the ones you had in the car at the time of failure?

2. I know of many owners of highly tuned B235R's who have not complained of bad pistons. Perhaps an isolated incident?

3. What other mods had you done to the car? Really for that power level things like a bigger intercooler, intake pipe, maybe water injection etc.

Not only is that amount of power pushing the turbo well outside of it's compressor map, but it's doing so on the stock intercooler, which is a very poor piece for a 300+ hp car on 9.3:1 compression.

At any rate the engine is very sturdy otherwise. The con rods are longer to give it more top end, the piston springs are softer, while the valves lighter, to reduce inertial and friction losses. The head is better flowing than the T5 head. The exhaust valves are made of a VERY epensive Nimonic alloy (definitely no bean counters there). And the piston pins are nitrided. (Also expensive and highly benefitial for longevity of a standard or modified car.)

It's a very very good engine in many ways. It deserves no bad reputation as a "cheap" motor. It's pistons were designed to be as light as possible to make the engine more responsive and to give better stock power and fuel economy. The fact that you should change them before going past 300 hp should not deter anyone. They'd be far better for that kind of hp as perhaps 8.5:1 compression or so.

Anyway, like I said before, it's a very well designed motor. Even if you have to replace the pistons in order to get huge power outputs its cyllinder head will still outflow the B234, it's con rods will still provide smoother power, it's nitrided pins will help reduce the chance of pin boss failure under high heat loads, it's nimonic valves will withstand higher EGT for longer, and it's entirely possible the the trapezoidal small ends on the conecting rod make them stronger than it's earlier cousin.

Also, most of the above mods are realy expensive mods that professional racers use. That means if you ever really wanted to tune the engine, many of the things profesionals would do are aready done. This might perhaps in the long run make it the better "tuner's engine" even if it's not the cheapest.

Dubbya~
 

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just to throw some gasoline on this argument ...
Having read the threads on the other board it would seem that the postulation is that the pistons are poorly designed in that the distance from the crown to the first piston ring is insufficient and causes the problem as detailed.
Changing material will help but if there is a design flaw it will always be weak
changing design of the piston is what is required giving more land area between the piston crown and the ring and as I understand changing to a different supplier will effect this change
the $64000 question is it really a design flaw ?
I think the many failures documented seems to point to this
And the solution ?
I guess it is change the pistons if you are going over 300 hp...Which I think maptun is advising for their stage 4 and above
Ok you do not need to do it for the b234 but that seems to be an exceptional engine (the bottom end anyway )
my 2c....
 

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Hi,

I will replicate the post I did over at the other Saab BB. You might know that my Viggen also suffered from engine problems, but was cured by Heuschmid.

This is the info I got from Johann Heuschmid, who is a Saab tuner for more than 30 years and is working now very closely with Saab in Sweden:

He sais there are 37 cases of broken B235R engines known to Saab. Nearly all of them are Viggen. The pistons get damaged, but not because they are especially weak. They are of very high quality, and they are coated.

There are multiple theories why this happens:

1. the B235R is identical in the 9-5 Aero and in the Viggen, BUT the way the air takes into the engine (and the intercooler) is different. Intake temperature on the Viggen under some driving conditions is 15 °C higher than on the 9-5 Aero.

2. on the Viggen, the crankcase ventilation is even more of a problem than on the 9-5 Aero, so sometimes oil is pushed into the cylinder. If there is 2% oil in the mixture, octane level drops from premium (100 Octane Shell V-Power) to regular (95 Octane). At speeds of 110-120 mph in 5th gear, the engine may start knocking. There is only 0.2 bar of turbo pressure at that moment, so knock detection is not active. This damages the pistons as shown on multiple pictures.
This can also happen with bad gas.

3. Very many of the viggens are often used under (Street-)Racing conditions. Only very few of the 9-5 Aeros are.

4. Very many of the Viggens are tuned. But of course, they are "stock" again when they get back to the dealer for damage analysis.

Why is Saab not very aware of the problem?

1. We all know the problem mosty occurs after 3 years or so. Most Viggens are out of Warranty by then, so only a limited amount gets to the ears of Saab engineers.

2. If the problem is told to the engine engineers at Saab, they say: "This is an engine from 2000. We did it in 1998. We are now working on the engines for 2006, which are completely different".

If you use other pistons than the stock pistons:

The same problems can occur with custom forged or b234 pistons, because the B235R piston is not the problem, just the victim of the before mentioned problems. There are just no reports of broken custom forged or b234 pistons in b235r engine because there are so very few of these engines.

These explanations are not mine, but they make very much sense to me.

Yours,

Philip
 

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Adrian,

1.NGK bcpr7es-11 with approx 5-7k miles on them gapped to stock spec.

2.I had not heard of any either until I posted about it and now they are coming out.

3.see this URL=http://www.vlphotos.com/saabvig..html]LINK[/URL] for mods

You won't hear from me that the b235r is cheap, but in stock internal form I don't see it going much past 300hp/350ftlbs and this is simething that owners of these engines should be aware of.

The engine will very likely break at that level, even if its just the pistons, its still a broken motor requiring tear down and rebuild whether its before or after the fact.

Philip,

You said your engine problems were cured, how were they cured? Let us know.

thx,

-Steve
 

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Originally posted by NVigR8:


1.NGK bcpr7es-11 with approx 5-7k miles on them gapped to stock spec.[/b]
I dont have the time right now to write, so I will just keep it simple for now.

Steve, dont run your car with stock spec if you have more boost than stock. Knock control will not work properly. The gap should be dropped once boost is raised. If you run a stage III you should have a gap of 0.8mm or so.
 

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Discussion Starter · #12 ·
Well, here's some more gas for the fire - certainly, any incompressible fluids in the cylinders would cause damage, but those are still 'theories'. The 'bean counters' are not theoretical and I'm certain they are a part of the equation, what ever its' final form may take. And I should add that I never meant to imply that the 235 was a cheap engine, only that there are two sides to the Saab/GM 'union'. My question is this: what are the distinctions between the B234 and various MY-B235 pistons? The Viggen pistons may very well be of "high quality" and "coated ", but how do they compare quality and cost-wise with what was used in B234 turbos? I've heard it said that the 9000 used Mahle forged ones - is this a fact? Also, though this may be a bit off-topic, will the later year B234s ('94-'98) bolt up to the 9-5/3 transaxles?
 

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Does anybody know if the b234 pistons will fit in the b235r? Not sure if the con rods are the same and/or if the oil squirter feature changed the design.

Also - any ideas when the mahle pistons were used? I hear for 2004 the B235R gets them.

Can they be purchased from the dealer parts counter?
 

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Originally posted by NVigR8:
[qb]Does anybody know if the b234 pistons will fit in the b235r?  Not sure if the con rods are the same and/or if the oil squirter feature changed the design.

Also - any ideas when the mahle pistons were used?  I hear for 2004 the B235R gets them.

Can they be purchased from the dealer parts counter? [/qb][/b]
Firstly the B235R I'm fairly certain also has oil squirters, as would be necessitated even by the stock compression ratio and boost pressure. But if you mean whether they changed the angle at which the oil is projected ... I wouldn't know. The dimensional changes between the motors were minimal. The B235R was more just a refinement of the B234R, so they would have only changed a major design if it was absolutely necessary. But it's possible they did.

At any rate it's not material. The B234R pistons won't fit, so you don't have to worry about where the oil will spray on a piston you can't install.

Secondly, as just mentioned the B234 pistons will NOT fit in the B235R. Just want to be clear on that. They may physically fit in the bore, but as you were worried, the con rods are of a different length. The Viggen uses longer con rods for about a 1.7:1 rod/stroke ratio. This helps in top end, and makes the engine run smoother.

The Rod/stroke ratio affects the way the piston moves. The higher the con rod ratio, the less "jerky" the movement is. Having longer rods also reduces the stress on both rod and piston at high RPM, making the Viggen engine much better suited for high revving.

Even if the pistons themselves were to limit the peak boost, you might be able to make up for that simply by installing the cams and valvesprings from a B234R which are both more aggresive. This would raise the rev limit enough to make more hp, and because the B235R's valves are lighter, the rev limit would stretch further than you could do with the B234R. The afformentioned better flow through the head would help this too.

So even from a cost perspective ... it's not impossible that, if tuned properly, a B235R could outperform the B234R even cost wise for horsepower, though perhaps not torque. It's easier to change to the better valve springs and cams than it is to port the B234R's head up to the 5R's spec. If the springs are compatible. (I already know the cams are, so it's not a stretch to assume so.)


Also on the note of pistons. The B235R uses relatively large ring lands. See picture at beginning of post. Those are not small by most measure. They look to be 6 or 8 mm, whereas most new turbo cars use about 4 mm. The new Dodge SRT-4 uses a 4mm ring land on CAST pistons (which are also coated) and like the Saab has a reduced length between the wrist pin and piston deck. (Which was more likely the "flaw" in the B235R's pistons.)

The difference in the case of the SRT-4 is that it runs 8.1:1 compression, and detonation is virtually a non-issue. With the relatively high compression ratio in the B235R, it's more difficult to avoid. (As Phillip pointed out.)

Phillip mentioned 110-120 mph driving being part of the cause for the B235R's frequent self destruction. I would agree. I don't think Saab engineered the engine with sustained high speeds in mind. Short bursts of speed perhaps. But IMHO the Viggen was not aimed at the German market, and the only place where sustained high speeds are legal is Germany.

Most of the other cases for broken pistons appeared to be as a result of tuners significantly increasing boost pressure without increasing intercooling, and in some cases not increasing fueling with a higher pressure FPR.

Also keep in mind that a stage III Viggen engine puts out a LOT of horsepower. Far too much for the teeny little intercooler IMHO.

Also, if crankcase ventilation is a problem, I've already solved it on mine. I vent my fumes to the air through a filter. This happened as a result of breaking the plastic piece and not being able to run to the dealer for another, but it does prevent any significant fumes from being vented back into the engine. It's still maintains the very small vacuum line to the intake, so that when under vacuum the fumes are burned, but under pressure they're vented.


Apologies for the long post. I think we should say the Viggen engine is just "different" than the 9000 Aero's. It responds better to things like better intercooling, and higher revs, rather than just high boost like the 9000 Aero did.

And I think the statement which essentially started the thread "the B235 cannot be safely tuned above 300 hp with the stock pistons." just isn't true. The Viggen engine cannot be safely tuned above 300 hp using the same methods applied to the 9000 Aero. It requires different mods. But has always gotten the same ones as the 9K by the tuners, and is a drastically different engine it terms of how it should be tuned. As for 110-120 mph driving on the stock engine, it might be fair to say that driving a Viggen for long periods at that speed is not safe for the engine. But in most places that's not safe for the driver either, so I'd hope no one holds that against the car outside of Germany.

Dubbya~
 

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Adrian,

you say that the B235R can be tuned to 300hp safely with stock pistonss, but didn't mention how. If you are saying by adding a better IC and B234R cams, I disagree. My piston was sure to crack after the install of my Spearco. I have seen the results of the b234R on a 9-5 aero on the dyno and wasn't impressed with the lack of a difference measurable result over the stock ones.

Perhaps with a lower compression ratio, that then again that would require different pistons.

Off piston shopping I go!
 

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Discussion Starter · #16 ·
The Viggen engine cannot be safely tuned above 300 hp using the same methods applied to the 9000 Aero. It requires different mods. But has always gotten the same ones as the 9K by the tuners, and is a drastically different engine it terms of how it should be tuned.  [/b]
Now, which tuners are you referring to Adrian? I've got a feeling that people like John or Fredrik at MapTun would be insulted by a comment like this. They both have a lot of experience with tuning and Saab engines, in general.

As for my statement at the beginning of the thread, it rests upon the evidence presented: there are many modified B234's, mine included, that still have their pistons intact. I feel sorry for Steve because he took the good advice of a respected, and knowledgeable person - Dr. Boost - and even with safe tuning practice (an upgraded intercooler) managed to end up with a junk pistons.

Also, I might add that higher rates of fueling pressure aren't considered elegant solutions for increased fueling: different injectors and the proper software is the more elegant solution. Otherwise, too much fuel when off boost, which could also spell death for the pistons, would certainly wash away the oil film on the cylinder walls and dillute oil in the sump.

Finally, I didn't start this thread because I want to bash the B235. I just find it interesting that pistons seem to be a problem with other vehicles in the GM stable. I'm thinking of the piston slap problem that has manifested itself on quite a few Chevy and GM cars and trucks. Again, I'm sure at the behest of the 'bean counters', pistons without the longer skirts were used. Some say it is no big deal, but if I just bought a new vehicle and I could hear piston slap, I wouldn't be too happy - maybe I'm just 'old school'
 

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Before running out and blowing up another engine, I suggest that you B235R runners have a look at Nick's website. first. Nick is even a regular visitor to SSc. What this man doesn't know about tuning that Viggen engine probably isn't worth knowing.
But I'll stick to my T5 on my B235R block if it's all the same to you
.
 

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Originally posted by NVigR8:
[qb]Adrian,

you say that the B235R can be tuned to 300hp safely with stock pistonss, but didn't mention how.  If you are saying by adding a better IC and B234R cams, I disagree.  My piston was sure to crack after the install of my Spearco.  I have seen the results of the b234R on a 9-5 aero on the dyno and wasn't impressed with the lack of a difference measurable result over the stock ones.

Perhaps with a lower compression ratio, that then again that would require different pistons.

Off piston shopping I go! [/qb][/b]
I apologise for being unclear.

Pistons crack generally because of excessive boost, which causes excessive torque. You can tune for more horsepower without using any more boost by moving the power higher up in the RPM band.

The intercooler would cool the air enough to prevent the detonation. It's this detonation that is causing your pistons to crack in one way or another. Forged pistons don't take "more power" they survive more of the detonation that is likely to happen at 300+ hp on the stock intercooler.

The B234 camshafts are more agressive than the B235R's camshafts. This is because the B234R's head does not flow as well as the newer B235R's head. Putting the cams from a 9000 Aero have been shown on the dyno to improve the top end and middle range on the Viggen. Combined with the higher strength Aero valve springs and there would be more hp still available due to a higher redline and better valve springs, which help improve the valve timing at high RPM. (The Viggen uses softer ones because it has lighter valves and does not need such hard ones to rev to redline, but once redline is moved higher srength ones would be necessary.)

So by making sure your charge is adequately cooled by a good intercooler or some kind of water injection, putting some different camshafts in, the Viggen's engine should be capable of 300+ hp without breaking the engine open.

As further argument, I mentioned the SRT-4 ... it uses cast pistons which are in stock form capable of 500+ hp and 600+ lb-ft of torque. They are NOT even as beefy as those Saab pistons.

Why do they manage that while ours don't always? They aren't designed better. They don't make use of the "quench pads", they aren't flat topped, and they're even smaller, with thinner still ring lands. (Which are the part that usually breaks.) They're just lower compression, so detonation is more easily avoided. No detonation, no broken pistons.

I've never seen a piston break from too much power without detonation being involved. Though I have seen piston rings fry because of too much power. I've seen rings microweld themselfs to the lands during high boost if the EGT gets out of control. And I've seen pistons, con rods, and crankshafts fly apart due to excessive rpm. And I have also seen con rods and crackshafts blown apart by excessive power. But pistons?

Pistons are generally designed very sturdily because even "mild" detonation at 200 bhp causes more in cyllinder pressure, and more stress than 500 hp does without detonation.

Dubbya~
 

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Just finished my last post and found two more! Man I'm slow.

Piston slap is common among the LS1 V8's because they use forged pistons. This only occurs when the engine is cold. My best friend happens to drive a 2001 Camaro SLP SS, and yes the piston slap is annoying. So far, not one single engine has broken or been damaged because of it here in the US. This I know because that friend is also a tech at a dealer and has access to the GM database. (We researched this a bit after hearing the slap ourselves. So far no unusual oil consumption, loss of compression or power. It just sounds a little annoying on warmup.)

The FPR I was referring to is on the MapTun stage 3 upgrade for the Viggen.

"Now, which tuners are you referring to Adrian? I've got a feeling that people like John or Fredrik at MapTun would be insulted by a comment like this. They both have a lot of experience with tuning and Saab engines, in general." -- Robert

It's my oppinion, I should hope that it is not somehow heresy to the crown of SaabTuners to shine light on what might have been less than perfect decisions. And it's not as though I don't respect them for all the did with various other Saab engines. Heck, if I were gonna upgrade, who do you think I would call??

Secondly, I stand by my oppinion. The B235R uses shorter pistons, longer rods, better flowing cyllinder heads, and has a poorly flowing and cooling intercooler.

My oppinion stands that it needs a better intercooler to help with flow and cooling. Increased use of high revs because of the shorter piston height, lighter rods and pistons, better flowing head, and higher rod ratio (all of which specifically make the engine run nicer at high RPM).

It may be more expensive than just an exhaust, intake, FPR, and chip. But I think it would allow the engine to reach higher hp more safely. That's my oppinion and is certainly open to debate if Johny or Frederik were to read this and wished to contribute.

They have a lot of experience with Saab engines, but how much could they have with the Viggen's engine? It's only just now been in existance 5 years. It takes time to develop new tuning techniques for an engine so different in purpose to its close 2.3L brethren.

Dubbya~
 

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Hi Adrian, just for your info: MapTun Stage III does not need or include an upgraded FPR. This is a mistake on their web page, they should have corrected this a long time ago as it already caused a lot of confusion.

BTW: At least 305 hp are perfectly safe on stock B235R internals if you change the IC. This is proven by Hirsch with their Troll R, which is officially Saab approved and has been sold in Germany alone a few dozen times. There are no broken engines on these cars known of yet.

Yours,

Philip
 
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