SaabCentral Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
164 Posts
Discussion Starter · #1 ·
I was wondering if anyone has bored out there cylinders and put in oversized pistons in?
i have a 1999 9-3 se
 

·
Banned
Joined
·
736 Posts
encore said:
I was wondering if anyone has bored out there cylinders and put in oversized pistons in?
i have a 1999 9-3 se
i want to bore it out to a 2.2 if i can... mayb this summer, or sooner if i cant figure out this oil thing:(
 

·
Registered
Joined
·
1,420 Posts
We have made a couple odd engines. Using combinations of factory sizes you can get a range of displacement. Each having various benefits.

90x93 = 2.445 (Eds Viggen 2.3 crank c900 2.1 bore)
90x90 = 2.290 (Stock 2.3)
90x78 = 1.984 (Stock 2.0)
93x78 = 2.119 (2.0 Crank with large bore)

The larger bore helps un-shroud the valves. For a normal car there is not much benefit to changing..

Another variable to consider is rod length. The B204, B234 and B235 share the 153mm rod length but the B205 has a longer rod of 159mm. Using these long rods in the 93x78 will give best benefits and I will use this in my next engine.
 

·
Registered
Joined
·
1,719 Posts
NickTaliaferro said:
We have made a couple odd engines. Using combinations of factory sizes you can get a range of displacement. Each having various benefits.

90x93 = 2.445 (Eds Viggen 2.3 crank c900 2.1 bore)
90x90 = 2.290 (Stock 2.3)
90x78 = 1.984 (Stock 2.0)
93x78 = 2.119 (2.0 Crank with large bore)

The larger bore helps un-shroud the valves. For a normal car there is not much benefit to changing..

Another variable to consider is rod length. The B204, B234 and B235 share the 153mm rod length but the B205 has a longer rod of 159mm. Using these long rods in the 93x78 will give best benefits and I will use this in my next engine.
Great info!

And your opinions of sticking this in a B234?
 

·
Registered
Joined
·
2,490 Posts
just out of curiosity how to longer rods help?
 

·
Registered
Joined
·
1,420 Posts
The rod ratio (Rod Ratio = Rod length / Stroke) The length of the piston movement is dictated by the stroke of the crank. The way it moves however is controlled by the rod ratio, the acceleration and dwell as it changes directions at the ends of the stroke.

Basically for a high rpm engine you need to stay below a peak velocity to get proper filling. You also need to keep the loads on the bearings under control. You can only package a rod so long without raising the deck height though.. So we have to start moving the pin up in the piston till we run in to the rings. You can run a special oil ring package and a smaller pin but this gets tricky and requires a custom rod, pin, ring package which would be necessary anyway just a little more time consuming to design. Now how much are the actual changes certainly a bit maybe a few hundred more rpm.

at 7200rpm for example with the best ratio of 2.04 (b205) peak pistons speed is ~30m/s vs the worst (2.3L) ratio of 1.70 of 35m/s
Interesting is that the peak is moved from ~80deg from TDC to ~60deg on the 1.7ratio engine.. This dictates a different ignition timing too.

This is only a small part of the story but you get the idea..
 

·
Registered
Joined
·
804 Posts
NickTaliaferro said:
The B204, B234 and B235 share the 153mm rod length but the B205 has a longer rod of 159mm. Using these long rods in the 93x78 will give best benefits and I will use this in my next engine.
Are you sure that's wise- abandoning a generally-regarded as "ideal" 1.7:1 rod ratio (153/90) in favor of a longer, potentially weaker, rod, as well as a MUCH thinner, and definitely weaker/less-reliable, piston ... merely for a very slight increase in efficiency brought about by a 1.77:1 rod ratio gotten with a 159mm rod on a 90mm crank?

Or do you JUST mean with the 78mm crank? :confused:

Can you even make the T7-height pistons 6mm shorter witout massive oil blowby and piston rock, as well as absurdly-high compression? edit: just look at the difference in 9000 Aero vs. Viggen pistons. That's 5mm shorter. Do you really think it wise to make them 6mm shorter still?:confused:

Also, you're forgetting about the B234R/L in the 9000's, the B234 has two different rods, the B234 turbo engines having a shorter rod as dictated by the much taller piston height (check the part numbers; if Saab only wanted different compression, they would have just changed the piston- not the piston AND the rod (besides, it's well-known that they are shorter)) ::



There's no way it could use the same rod without impacting the cylinder head. As the part numbers indicate, the N/A engine used the B204's rod.

Also, all the C900's had shorter rods from the shorter deck height, obviously. But I know this is not the C900 forum. Just making sure everyone here realizes that. I have several sitting around and they are definitely not 153mm long.

Also bear in mind that B235 (and maybe 205R's? :confused: ) of 2000+MY use trapezoidal small-ends which may not necessarily be compatible, or preferrable, on other engines. And any other rod used with the pistons designed for a 2000+MY B235/205R will not fit:



B205 = 159mm
B204/204/234i/235 = 153mm
B234R/234L = 148mm
B202 = 135mm (measured from the one next to me)

Just food for thought I guess.

-Adrian
 

·
Registered
Joined
·
1,420 Posts
Adrian.. A this is a discussion about modern saab engines.. In the families used in the NG900/9-3 B Pretty sure I can make a B205 based 2.1 ;) Are you forgetting the fact we are a JE pistons dealer and I might not be sharing all the resources I have. ;) Or all the details.

I have seen that picture you got from Nordic years ago.. Even compared the parts in the workshop.

Are you sure about the later rods not fitting.. ;) You have experience with this?

As I stated the Rod, piston, ring, pin combination is a PACKAGE.. you obviously can't just go swapping parts. I am sure not going to run a stock rod in an engine of this type. Probably not going to be able to find 93mm B205 pistons either. :roll: Orignal headgasket sure wont work either.. :roll:
 

·
Registered
Joined
·
804 Posts
NickTaliaferro said:
Adrian.. A this is a discussion about modern saab engines.. In the families used in the NG900/9-3 B Pretty sure I can make a B205 based 2.1 Are you forgetting the fact we are a JE pistons dealer and I might not be sharing all the resources I have. Or all the details.
Have you forgotten than I know the (or at least one of the) chief engineer(s) at JE for custom piston design? (also named Nick, oddly enough :cheesy: ) I might not be sharing all my resources either, but really I was just concerned with the idea of fitting 159mm rods to a 90mm crank.

As for a 2.1L B205R ... that sounds like a GREAT idea to me, and I know (and you know I know) that there are no factory replacement pistons with more than a 1mm oversize, nor accomodating head-gaskets. IIRC, [email protected] uses a 94mm bore in his 2.5L engine. Applied to the B205 and you could get nearly ~2.2L out of it. In theory, with appropriate cylinder liners, you could go as high as 98mm while still leaving 5mm between bores. (same as the Chrysler SRT-4's 2.4L, as well as all its 2.2/2.5L SOHC descendants from the 80's and early 90's) But I have NO idea how well the Saab block's infrastructure would support such liners, or if they're even necessary (as the stock block may have siamesed cylinder bores and I don't know the stock thickness).

Nick said:
I have seen that picture you got from Nordic years ago.. Even compared the parts in the workshop.
Actually, I got it from someone else, who apparently got it from Nordic. :p

Nick said:
Are you sure about the later rods not fitting.. You have experience with this?
The 159mm rods "fitting" the 90mm crank? Not without a seriously thick head-gasket or seriously thin ring-lands, neither of which are ideas I'm too keen on. Unless the Saab literature is WAY off.

Anything can be "made" to fit, with enough modification. I just expressed my concern about whether or not it was a good idea. I don't recal saying anywhere that it was impossible. Besides, you of all people here oughtta know me better than that by now.

Nick said:
As I stated the Rod, piston, ring, pin combination is a PACKAGE.. you obviously can't just go swapping parts. I am sure not going to run a stock rod in an engine of this type. Probably not going to be able to find 93mm B205 pistons either. Orignal headgasket sure wont work either..
Where on Earth did I say you were using STOCK pistons? Even my reference to "stock rods" in regards to the trapezoidal small end was directed more at other members who MIGHT be considering the idea, as your post didn't make any mention of custom rods when referencing length, and a previous post made a mention of "factory sizes" that I thought people might misinterpret. That's all.

In your direction, I was just voicing my concerns based on sheer dimension, not the idea that you'd have any desire to use the stock pistons or rods. And, it too, was just in regards to the idea of 159mm rods on a 90mm crank, something you appear to NOT be doing.

I thought we'd have both gotten past the point of these simple misunderstandings. I'm sorry I didn't realize you were merely planning on using 159mm rods with the 78mm crankshaft, which I think is a fine idea, although even the 153mm rods leave it with a REALLY good rod-ratio of 1.95 already (higher than that is rarely beneficial as the increase in combustion efficiency begins to be offset by increased weight from the longer rod), and would leave more room for pistons with very thick, tough, ring-lands. :)

Anyway, you have my blessing on the 2.1L (or now maybe ~2.2?) B205, even if I think tougher pistons might be preferrable to longer rods when the rod ratio is already so high as 1.95- it's just a trade-off that I myself would not bother with, but not something I'd condemn, as it's certainly not a BAD idea or anything. ;)

-Adrian
 

·
Registered
Joined
·
1,975 Posts
Remember also that the mapping of the car if done via "post" will become more difficult once these parts are altered.
 

·
Registered
Joined
·
804 Posts
Troll_speed said:
You really, really don't want stock Viggen pistons.

Maybe a 2.3 Turbo motor from a 9000 (94+up) is what you're looking for.
But the 9000 Aero pistons are ginormously tall, as can be seen, and forged pistons of the same pin-to-deck height might be a bit of over-kill. Forged pistons with the same heigh as the Viggen pistons could easily be made to handle 600+ horsepower.

So perhaps, B204, or aftermarket of similar length, rods with forged pistons made for a Viggen and a 90mm crank to match.

--All Saab 16v engines' rods are forged, so aftermarket rods are stronger, but rarely in a massive sense, and often harder to find in good quality due to lower competition between companies to make a better and better rod setup.

--Also, fully machining, and polishing (and cryo-treating, if the stock rods are indeed typical martensitic steel which may, or may not, have fully completed the austenite-->martensite phase transition while cooling, which is completed when cryo-treated) the stock rods could easily double their effective (fatigue) strength due to significantly reduced stress concentration. Given the number of B204L (same rod as B234i) out there that can be had for cheap, if you want to swap same day and not use your own, it might be worth looking into.

Remember that even the stock B204L/B234i rods can handle around 400 horses or so, maybe more, and 7,000 RPM. Doubling the strength should cover almost any practical power goal.

-Adrian
 

·
Registered
Joined
·
1,975 Posts
Adrian W said:
the stock B204L/B234i rods can handle around 400 horses or so, maybe more, and 7,000 RPM. Doubling the strength should cover almost any practical power goal.

-Adrian
I know a few B204L's with 500+ hp and 600+Nm and reved to 7500rpms on regular basis, thus the "hepolite" pistons which are supposed to be weaker than the other std T5 pistons. All these parts will support big bhp as long as the mapping is in order, but eventually the limit will be found.
 
1 - 17 of 17 Posts
Top