B5204S vs B5204FS?

SomeGuy537 · Post by **SomeGuy537** » 22 Nov 2020, 14:22

Hello, does anybody know what the differences between the B5204S and B5204FS are? I can't find any info about it. If you go by Volvo's logic for their nomenclature "S" means naturally aspirated and "FS" means naturally aspirated with fuel injection and catalytic converter. However this seems to be a pointless distinction since all engines in the 850 are fuel injected and if i've understood it correctly all of them have catalytic converters too. According to Wikipedia the B5204FS was used in models badged only as "850" which was the base spec right? Does this mean the 2.0 20V GLT's feature the B5204S?
Kind regards.

Post by **RickHaleParker** » 22 Nov 2020, 17:19

Taking a clue from the 10 Valve versions. I don't think there is any difference. B5202S and B5202FS have identical specs.

SomeGuy537 · Post by **SomeGuy537** » 23 Nov 2020, 01:04

RickHaleParker wrote: ↑22 Nov 2020, 17:19 Taking a clue from the 10 Valve versions. I don't think there is any difference. B5202S and B5202FS have identical specs.

I see. Got to wonder why they bothered with two different names then. Are you sure all the specs are completely identical? Online i found clues that the B5204FS might feature EGR while the B5204S maybe doesn't?

Post by **misha** » 23 Nov 2020, 01:21

Older 20v engines (B5254FS)had variable intake,different style intake manifold and gasket.
When i say variable intake....they had some kind of flaps into intake openings.
Those are engines '92-'95(including '95).

All newer 20v engines have only "S" and no variable intake.
https://www.matthewsvolvosite.com/forum ... hp?t=65782

Post by **abscate** » 23 Nov 2020, 04:40

Great write up on this family of engines in this post, also discussion of the VIS system

https://www.matthewsvolvosite.com/forum ... is#p508090

The detailed engineering report in June’s post is amazing when you realize this engine concept was developed in the late 1980s

SomeGuy537 · Post by **SomeGuy537** » 23 Nov 2020, 08:01

Great info! I tried to find out which of the two engines i had in my car but the "45" engine code means B5204S according to some sources and B5204FS according to others. I was able to confirm that i have the B5204FS when the intake was removed while doing a PCV -job though. I noticed the weird looking manifold with the valves inside the intake runners. Does anyone know if there are any other differences? Are the engine managment systems the same? I've heard the B5254S and B5254FS don't have the same engine management.

Post by **misha** » 23 Nov 2020, 10:16

You have a sticker on timing belt cover with engine serial number and type.
Also....behind a timing belt cover,on the block...there is a factory number(the same like on the sticker) and engine type.

SomeGuy537 · Post by **SomeGuy537** » 14 Dec 2020, 11:07

misha wrote: ↑23 Nov 2020, 10:16 You have a sticker on timing belt cover with engine serial number and type.
Also....behind a timing belt cover,on the block...there is a factory number(the same like on the sticker) and engine type.

On my timing belt cover it says B5204S however it has the V-VIS intake manifold aswell as Bosch LH 3.2 Jetronic which would point towards it being a B5204FS right? I made another thread about this but i replaced my spark plugs twice recently because i used the single-prong plugs made for the B5204FS at first but it ran badly with those so i put in the three-prong plugs that aren't recommended for the B5204FS according to Volvo and now it runs great. Would this point towards my engine not being a B5204FS or is that just a dumb conclusion?

Post by **RickHaleParker** » 14 Dec 2020, 16:19

Looks like the only difference between a S and a FS is that the FS is equipped with a catalytic converter. Later on when catalytic converters became standard equipment the F was dropped. If this holds true a B5204FS is a B5204S with catalytic converter.

F is coming across as a Kludge. Both S and FS are Fuel injected. Perhaps C for Catalytic converter instead of F would of been better. Better yet encode it in emissions in the VIN number rather then the engine ID code because the addition of a catalytic converter does not change the engine configuration.

6th: Induction method (S/T/F/G/GS/FS/FT/SG)
S = standard (naturally aspirated).
T = turbocharged.
F = fuel injection with catalytic converter.
G = leaded fuel compatible,
GS = leaded fuel compatible, naturally aspirated,
FS = fuel injected standard (naturally aspirated) with catalytic converter.
FT = fuel injected, turbocharged with catalytic converter.
SG = standard (naturally aspirated) compatible with alternative fuels (LPG / CNG)

SomeGuy537 · Post by **SomeGuy537** » 15 Dec 2020, 02:42

RickHaleParker wrote: ↑14 Dec 2020, 16:19 Looks like the only difference between a S and a FS is that the FS is equipped with a catalytic converter. Later on when catalytic converters became standard equipment the F was dropped. If this holds true a B5204FS is a B5204S with catalytic converter.

F is coming across as a Kludge. Both S and FS are Fuel injected. Perhaps C for Catalytic converter instead of F would of been better. Better yet encode it in emissions in the VIN number rather then the engine ID code because the addition of a catalytic converter does not change the engine configuration.

6th: Induction method (S/T/F/G/GS/FS/FT/SG)
S = standard (naturally aspirated).
T = turbocharged.
F = fuel injection with catalytic converter.
G = leaded fuel compatible,
GS = leaded fuel compatible, naturally aspirated,
FS = fuel injected standard (naturally aspirated) with catalytic converter.
FT = fuel injected, turbocharged with catalytic converter.
SG = standard (naturally aspirated) compatible with alternative fuels (LPG / CNG)

I think all 850's have a catalytic converter, as far as i know there are three emissions codes in the cars VIN:
0 = Catalytic converter, oxygen sensor and evap
1 = Catalytic converter, oxygen sensor, evap and EGR
2 = Catalytic converter, oxygen sensor, evap, EGR and secondary air pump

So i don't think this is it.