Why o.8bar boost on 3b and 1.2 on Aby

[220bhp]

Just wondered why Audi launced the s2 3b with only 0.8bar max boost and then changed it to 1.2 bar on the Aby. Was it a marketing ploy to sell the new model or was there another reason.I know that the Aby is 10hp more than the 3b,and that it has coilpacks instead of a distributor, but it just seems to me that the 0.4 exstra boost and coil packs would be worth more than 10hp.

[Greg_S]

I think it may have been due to the ignition coils on each cylinder, and marketing

[UrS4boy]

Just wondered why Audi launched the s2 3b with only 0.8bar max boost and then changed it to 1.2 bar on the Aby. Was it a marketing ploy to sell the new model or was there another reason.I know that the Aby is 10hp more than the 3b,and that it has coilpacks instead of a distributor, but it just seems to me that the 0.4 extra boost and coil packs would be worth more than 10hp.

I think you should look at the torque figures not just the hp. The ABY (and AAN) have more grunt than the 3B. Technically, the 3B uses a 2.0 Bar (absolute) manifold air pressure (MAP) sensor whereas the ABY (and AAN) use a 2.5 Bar MAP (stock form). The 0.5 bar difference in the MAP allows the 0.4 bar extra boost (as controlled by the ECU).

Personally, I am running an 3.0 Bar VMAP for my RS2'd 93 S4. With MRC software I hit 26.9 psi (relative) boost (about 2.9 Bar absolute) as measured by Kevin Day's TDS-1 digital information system.

[220bhp]

Thats great information m8, but why was it done.

[UrS4boy]

Why does any auto manufacturer improve horsepower, torque and, if they can do it, fuel economy? To garner more sales.

Back in the day, circa 1990, 217 hp from a 3B was good stuff. However, more is ALWAYS better, so coming up with ways to get a) more hp and b) more torque is a good thing. Remember than the ABY did not magically appear in 1993. It was an development of the AAN which was fitted to the much heavier C4 S4 in the 92 MY. The S4 was even heavier than the 3B-equipped 200 20vt and it needed the extra torque to fullfil the design mandate to have an engine that would give the driver the impression that they had a V8 under the bonnet (hood) all the while returning fuel economy like a V6. Hence the need for the extra hp and torque over the 3B.

Obviously considerable time, effort and money went into the development of the coil-on-plug ignition system for the AAN (later used on the ABY). The result was a relatively minor 10 hp increase (4.5% gain). However, the torque went from 309 Nm to 350 Nm, a 13.3% gain. This was the big benefit.

None of this could have happened without an increase in the boost pressure (to 1.15 bar) that was permitted by the new 2.5 Bar MAP, the ignition changes and new software.

Data refs: VAG SSP111 and SSP143.

[220bhp]

Fantastic.that exsplains why my s6 feels much more urgent than my 3b coupe.
I have just fitted a boost gauge in the S2, and it dos'nt seem to climb much more than 0.7bar, so I am on a bit of a witch hunt at the moment trying to find if I have a problem. Maybe I should compair the S2 with another 3b instead of the s6

[s2driveruk]

the extra power was only an overboost feature which lasted about 15secs and add in the extra weight of the ABY and the power difference is not massively different IMO

[valjo]

i guess that is why audi s2 3b used standard 5 speed gerabox (from audi 2.8 or 2.3 20v) and it has torque limit 310nm, but s2 aby used much better gearbox so it could have more nm and so need more boost

[alg]

i guess that is why audi s2 3b used standard 5 speed gerabox (from audi 2.8 or 2.3 20v) and it has torque limit 310nm, but s2 aby used much better gearbox so it could have more nm and so need more boost

True in reverse. IIRC from the press reviews at the time the gearbox used limited the torque hence the boost.

[S2central.net]

Torque is proportional to boost - pure and simple.

The ABY's ability to overboost into 1.2bar territory gives it the 380Nm torque figure which is about 70Nm more than the 3B could muster in standard trim.

Tis also no coincidence that the ABY engine was only fitted to cars with the stronger 01E gearbox as they would have had concerns in the factory about this with the relatively weak 01A box from the 3B. Its torque that kills gearboxes - not power.

Paul

[UrS4boy]

Torque is proportional to boost - pure and simple. The ABY's ability to overboost into 1.2bar territory gives it the 380Nm torque figure which is about 70Nm more than the 3B could muster in standard trim. Paul

Paul: Sorry, but I have to call you on the 380 Nm figure you put forward in your post above. I would pass it off as a typo but since you say its 70 Nm more than the 3B, you must think that 380 is correct.

All my info says 3B = 228 lb-ft = 309 Nm and AAN (should be the same as an ABY) = 258 lb-ft = 350 Nm (349.8 Nm if you're using 1 lb-ft = 1.35582 Nm).

http://www.boltscience.com/pages/convert.htm

I would be pleased if you could provide a hard reference for the 380 Nm figure so I can go seek it out for my library of UrS-car info.

Dave F. UrS4boy, aka "The Librarian"

[S2central.net]

258lbft is correct for the AAN as per first factory trim that was shipped to the states.

There are European S2 brochures that describe the overboost profile on the ABY equipped cars. I have always assumed the N.Am S4/S6 took this as well with later software. I can't find reference to it in any factory manual as yet.

[S2central.net]

There we are --->

http://www.s2-audi.co.uk/audi_docs/1994_brochure/page13.jpg

The 258lbft equates to 350Nm which is nominal max boost, whereas 380Nm is indeed the overboost mode. Other brochures are on Mike's site !

Paul

[S2central.net]

Backed up by this in the press pack... I knew I didnt imagine it

http://www.s2-audi.co.uk/audi_docs/press_pack_94/page5.jpg

Honestly dunno if this applied to stateside AAN engines. Guess it could easy enough - although its wee small intercooler might not be so keen on the idea - and it might have complications with programming for the Automatic gearbox option. Dunno !

Paul

[UrS4boy]

Backed up by this in the press pack... I knew I didnt imagine it

Honestly dunno if this applied to stateside AAN engines. Guess it could easy enough - although its wee small intercooler might not be so keen on the idea - and it might have complications with programming for the Automatic gearbox option. Dunno ! Paul

It would be interesting to compare the size of the intercoolers between an AAN and ABY. But that wouldn't be the end of it. The intake tract length is so much shorter for the AAN than the ABY there would be differences to account for there as well. Personally, I run a Apikol FMIC with my RS2'd 93 S4.

What are these things you call "Automatic gearbox option"? We did not have this option. All UrS-cars delivered to Canada and the US had five-speed standards with a 0.73:1 top gear. We have no need of autoslush boxes as we are manly men this side of the pond.

Thanks for the reference (and a source of more S-car info)

Dave F