Audi S4 and S5 planned to be 4 cylinder!

[actng]

Chipping the engine depends highly on the ECU used and the turbo. You can technically allow for 30lbs of boost if you have a factory EBC but your turbo will run out of effciency at 15 and will melt itself at 25. (have a friend who had a vac hose come off so his waste gate wasn't actuated, he just bought a new turbo...)

not sure about the high end cars but most "average" cars with turbo are maxing out at 5psi - 10psi. so chipping it to 15 or even 20psi is possible without significantly shortening turbo life/engine life for those who care to try.

There will still be a considerable difference in feel between a large displacement V8 and a small-medium displacement turbo there is just no way around it. The question is will it be enough of a difference to make the S4/5 undesirable?

this is sort of pointless for me to say but i'll say it anyway... a V6 turbo for example is a happy medium between goign with a NA V8 or V6... you can get CLOSE to the same power as a V8 but be as fuel efficient as the V6.

i love it. for myself, i'm not sure if i want to drive a non-turbo car again.

 

[thedguy]

not sure about the high end cars but most "average" cars with turbo are maxing out at 5psi - 10psi. so chipping it to 15 or even 20psi is possible without significantly shortening turbo life/engine life for those who care to try.

Except a lot of modern turbo engines are now running 15-20psi from the factory. GM's turbo ecotec's in the US. Evo's and STi's IIRC are fairly close to that as well.

this is sort of pointless for me to say but i'll say it anyway... a V6 turbo for example is a happy medium between goign with a NA V8 or V6... you can get CLOSE to the same power as a V8 but be as fuel efficient as the V6.

i love it. for myself, i'm not sure if i want to drive a non-turbo car again.

Stock, a v6 turbo seems pointless, the weight and complexity make it worse than a v8 and most modern v8's seem to do quite well on mileage, compared to turbo v6's.

 

[Orubasarot]

Eight second round the 'ring isn't that much. And they should have gone with the more traditional Audi 5-cylinder engine, like this:
http://img140.imageshack.**/img140/940/audiquattroenginejarama.jpg

That's the only thing wrong with this news. A (THE) turbo 5 would honestly guarantee a purchase from me. But besides that, if other companies follow then I will finally stop torturing my family members with stories of how obese modern cars are.

My E46 is a whale but I can't believe there are "small coupes" even heavier than that.

 

[prizrak]

not sure about the high end cars but most "average" cars with turbo are maxing out at 5psi - 10psi. so chipping it to 15 or even 20psi is possible without significantly shortening turbo life/engine life for those who care to try.

You have 11psi of boost with a chip you will have 15. The point is not what the engine will take or the turbo the point is efficiency. Your turbo might be able to take 20psi but it is inefficient above 15. Alot also depends on the turbo, whatever you are running from the factory might be very close to peak for that turbo and as thedguy pointed out alot of cars running 15-20 nowadays (Evo runs 22 or so stock) and the turbos tend to be pretty small to minimize lag.

this is sort of pointless for me to say but i'll say it anyway... a V6 turbo for example is a happy medium between goign with a NA V8 or V6... you can get CLOSE to the same power as a V8 but be as fuel efficient as the V6.

i love it. for myself, i'm not sure if i want to drive a non-turbo car again.

It's been pointed out by thedguy already but they are not. V6 tends to have peak torque high in the rev range so if you turbo it you end up with having to deal with lag same as the I4 since you have little bottom end torque. N/A V8s are generally pretty good on fuel because of the amount of torque available at low RPM's. It is not uncommon for Vette guys to get 25mpg on the highway because at those speed in top gear the engine is barely turning. As an example from Audi itself the TFSI V6 in the new S4 is no better on gas than the old V8, which I think was an EFI so generally less efficient than FSI.

Since you have the same engine as I do I suggest watching your real time MPG when you are running between 4-5K RPM and see it drop into single digits very quickly. Boosted cars are only better than N/A cars on gas when they are out of boost range because as soon as boost is there you are effectively increasing your displacement. In crude terms at 1bar (~15psi) your 1.8 becomes a 3.6.

 

[M_Bolc]

^The old biturbo S4 had peak torque at 1975 RPM, and it plateaued all the way up to 5500 RPM, that's why it still is considered the best of the S4s.

 

[thedguy]

^The old biturbo S4 had peak torque at 1975 RPM, and it plateaued all the way up to 5500 RPM, that's why it still is considered the best of the S4s.

That number is only achievable under boost though. The moment any engine starts to get positive manifold pressure it's just gonna suck down fuel compared to an n/a engine of similar torque/power.

 

[actng]

Except a lot of modern turbo engines are now running 15-20psi from the factory. GM's turbo ecotec's in the US. Evo's and STi's IIRC are fairly close to that as well.

Point taken... it depends on the car. My car was max at 5psi from the factory and spikes at 7psi. The SRT4 is also about 10psi I believe.

Stock, a v6 turbo seems pointless, the weight and complexity make it worse than a v8 and most modern v8's seem to do quite well on mileage, compared to turbo v6's.

Again, depends on the car... Audi S4 (B5 platform) has a biturbo V6 and that ran (still runs) much better than a V8 like A8 or 7series.

Your turbo might be able to take 20psi but it is inefficient above 15.

So for a race car, chipping the engine will make the turbo inefficient... but for a street car, where you're not constantly pushing it to the limits, it may be a good option for some folks who mainly want fuel efficiency but on the odd weekend want to open it up and don't mind the poor fuel efficiency?

It's been pointed out by thedguy already but they are not. V6 tends to have peak torque high in the rev range so if you turbo it you end up with having to deal with lag same as the I4 since you have little bottom end torque.

That right there must explain why they are going with a 4 banger for the new S4...!

 

[The_Finn]

So for a race car, chipping the engine will make the turbo inefficient... but for a street car, where you're not constantly pushing it to the limits, it may be a good option for some folks who mainly want fuel efficiency but on the odd weekend want to open it up and don't mind the poor fuel efficiency?

compressor effciency not fuel effciency

EDIT:

Again, depends on the car... Audi S4 (B5 platform) has a biturbo V6 and that ran (still runs) much better than a V8 like A8 or 7series.

not really... the only thing the V6 has going for it is maybe smaller physical footprint but any V6TT is going to be significantly more complex than a V8 and as a result of heavy turbos possibly just as heavy. Also while i love the 2.7TT found in the B5 you have to treat it nice or it will eat turbos and itself (it's like the 13B-REW of the audi world) compare that with the million or so audi V8s that are running like champs after damn near 2 decades

 

[thedguy]

Again, depends on the car... Audi S4 (B5 platform) has a biturbo V6 and that ran (still runs) much better than a V8 like A8 or 7series.

How so? The v8 models have significantly lighter and less complicated engines. And as Finn pointed out, they aren't known for their reliability.

 

[actng]

compare that with the million or so audi V8s that are running like champs after damn near 2 decades

hmmm interesting... i actually know of more Audi V6TTs that are still around than Audi V8s... but then that might be something to do with Audi... and also the lack of V8s back in the day.

 

[M_Bolc]

I have an uncle at an Audi dealer, appart from some weak turbos on the first 2.7 TT's those engines have been pretty healthy, and some of those show up with significant modifications on them still running like a dream.

 

[The_Finn]

I have an uncle at an Audi dealer, appart from some weak turbos on the first 2.7 TT's those engines have been pretty healthy, and some of those show up with significant modifications on them still running like a dream.

it's not the turbos themselves that are weak it's a few small parts that are prone to failure on all versions of the V6TT (except RS4 i believe) IIRC it's the bypass valves and some coolant lines. When these parts go it allows for conditions which will kill the turbos if you replace these parts with other stronger audi parts the engine will run fine for a long time. Issue being that alot of owners that are not ethusiests never learn and therefore kill their engines. Thats why i made the reference to the Mazda 13b-REW (twin trubo 2-Rotor) that requires similar "reliability modifications" so that it doesn't eat itself

hmmm interesting... i actually know of more Audi V6TTs that are still around than Audi V8s... but then that might be something to do with Audi... and also the lack of V8s back in the day.

Audi has been making cars with V8's since 1988 and they sold resonably well and most of them are still running to this day compared to the failure rate of the V6TT (see above) there is no contest that the 3.6L and 4.2L audi V8's are much more reliable and about equal as far as weight (though the early V8's don't have quite the power of more recent models)

 

[chaos386]

Well, the whole discussion is rather moot until we know how the cars turn out to be.

The only thing I can base my opinion off is the new 6cyl S4, which is inferior to the old V8 S4.

Because it gets less power, weighs the same, and doesn't get better economy.

If the move to 4cyl is going to be more of the same, then all I can say is no thanks.

I hear a lot of people in this thread saying the same thing about the new S4, but from some articles I found online, it has better fuel economy than the old S4, not worse. Plus, the power is nearly the same (333hp vs 340) and it's a bit lighter.

I don't see what the problem is with an S4 with a turbo 4 and 800 fewer pounds, even if the power drops to 280 hp or so.

EDIT: The weight of the S4 dropped by about 100 lbs, power by about 7 hp, and fuel economy rose from 20 mpg highway to 24 mpg. That's a 20% efficiency increase for a 2% drop in power and 2% drop in weight. I'd say that's damn good, and if they can repeat that with the four-cylinder models, I say bring it on.

EDIT2: 24 mpg is actually for the combined cycle (from Audi's UK website, I got the highway economy for the previous S4 from Edmunds); Audi UK claims 32 mpg on the highway for the new S4, and yes, I made sure to convert all UK mpg figures to US mpg. They also claim the new (UK) S4 is 3637 lbs compared to 3990 lbs for the previous (US) S4, but that could just be differences between UK and US models, so I'll stick with the "~100 lbs weight loss" figure from the articles above.

 

[prizrak]

Point taken... it depends on the car. My car was max at 5psi from the factory and spikes at 7psi.

Are you sure about that? You have same engine as mine and on the A4 its an 11psi stock boost.

it's not the turbos themselves that are weak it's a few small parts that are prone to failure on all versions of the V6TT (except RS4 i believe) IIRC it's the bypass valves

Yeah bypass valves are a big issue with the Audi turbos they have very low tolerances even if you go Stage 1 which is 4psi more than stock it is highly recommended to get a stronger DV, so I can believe that even with stock settings they would be prone to failing. The N75 valve and the turbo intake pipe are also pretty weak. Also if I remember correctly the actual turbos on the B5 were pretty weak on all the models.

 

[M_Bolc]

One more point to Audi, I just remembered that the new A4 the 2.0T is just as fast as the 3.2. The lighter engine does make sense

 

[prizrak]

One more point to Audi, I just remembered that the new A4 the 2.0T is just as fast as the 3.2. The lighter engine does make sense

I think it's more that the 3.2 is not all that great Car's acceleration and top speed are highly dependant on gearing as well. For instance the 1.8T with 5 speed auto has a hard time in 2nd gear. The 6spd manual doesn't have that same problem and is faster because of that.