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Horse POwer

3K views 19 replies 10 participants last post by  doubledoom 
#1 ·
One thing i dont get is..with 4.2L and a V8, why do they only put 354hp on the S5....even G37(v6) has 330 hp, M3 has 413 hp. My guess is they dont want to create too much competition for the future Rs5...
 
#2 ·
The RS4 has the same engine with 420hp. There's about a .1-.2 second difference from 0-60. It's still a very powerful V8.
 
#3 ·
It's a little more complicated than just "putting on" HP. The S5 engine is a tuned Q7 V8 (IIRC). Logistically, it was Audi's best solution. The RS4 lump (420HP) is a completely different beast. The next RS4/5 should have the same 4.2 RS4 engine with FSI, which should put it around 450HP.

The S5 and M3 are not direct competitors, so no need to compare the engines. As for the G37, a big V6 is more than capable of putting out that much power. Infiniti's been messing around with that engine for a long time now...
 
#4 ·
The S5 is also more fuel efficient than the RS4 version as well IIRC.
 
#19 ·
I am not finding that at the moment, but then I have only done 2.5k miles...
 
#5 ·
I am not 100% sure if it is a good idea but my Audi dealer told me that after I make 6-7000km on my car they will be able to do something with the software of the car and make it 400hp and more...
Do you guys think its possible?
 
#6 ·
As far as I know, that engine is completely incapable of putting out 400hp+ with a simple software mod. In fact, I don't think anything short of a complete rebuild will yield 400hp+ with that engine. You can get somewhat close by going all out with mods, but I don't think it can get there, especially with only software.
 
#7 ·
+1 You can expect a software mod to add around 10-18 HP to the gas/petrol V8, if you add a complete exhaust (with downpipes) you'll get about 10-12 (maybe 15) more with no other tuning or mods. Very doubtful that a software only mod would (or could) do 400+ HP.
 
#9 ·
No, completely different engine. There's a whole other computer in R8 and RS4 to handle the changes (specifically, the calculations needed for the increased redline) made to the lump.

Trust us, a software update WILL NOT give you 400hp from the S5's 4.2. The dealer's talking out of their @ss.
 
#11 ·
Lol if you consider the G37 even comparable, you should definitely go drive one. I test drove one like 2 weeks ago, and it's miserable. Most commonly, it is doing 0-60 in 6.0-6.2 seconds which is a full SECOND slower than the S5. Mostly because it is 3800+ lbs and only has 250 ft-lbs of torque (more similar to the A5).

The M3 is easily $10k more expensive depending on options.

-Ray
 
#16 · (Edited)
Lol if you consider the G37 even comparable, you should definitely go drive one. I test drove one like 2 weeks ago, and it's miserable. Most commonly, it is doing 0-60 in 6.0-6.2 seconds which is a full SECOND slower than the S5. Mostly because it is 3800+ lbs and only has 250 ft-lbs of torque (more similar to the A5).
Mind if I ask where you are coming up with these numbers? The G37 has 270 ft-lbs of torque. Also, most car mags have had the G run 0-60 between 5.2-5.4s.

http://www.caranddriver.com/reviews...rt_road_test+t-driving_impression+page-2.html

What exactly is so miserable about the car? For the price, its the best deal you can get for that kind of power, looks, and luxury...as u can see, I am a fan of Infiniti:)
 
#12 · (Edited)
Torque, flexibility and marketing...

OK so the S5 V8 puts out 354 BHP and another variant of that V8 (although quite a bit different) in the R8 and RS4 put out 420... There are a couple of things that need noting:

1) That's "peak" power... and BHP is a function of Torque and Revs, so more revs at the same torque, more BHP. The RS4 and R8 are higher-revving, so can make the BHP figure... However, put the R8 or RS4 engine and S5 engine side by side at 4,000 revs and they put out similar torque... ergo power. And this is shown in the performance figures of the RS4 and the S5... not that different.

2) So Audi have elected to put a more flexible and driveable engine with great torque characteristics across the rev range into their GT car (S5) and a higher revving, top-end torque loaded engine into their sports car (R8). That makes sense does it not?

3) The S5 is designed as a GT car, the RS5 when it arrives will be much more at the 'sports car' market and thus needs some room in the power stakes to differentiate it from the S5. In other words, if they'd put and engine with a '420' rating in the S5, they'd have to go 500+ in the S5 and that would mean large Turbos on the V8 or the V10, which would give power, but not the sports characteristics required and thus create a more powerful GT car. The RS5 will not need more than 450 BHP to be devastatingly quick if this is produced from a light engine with great response. But if the S5 had been 420bhp 'rating', would people fork out £15k more for a car which only had 20 or so more BHP?

At least that's what I think!

;)
 
#13 · (Edited)
I did some searching. Between the R8 and the RS4, there isn't a lot of difference -- same 4163cc motor, bore and stroke is 84.5mm x 92.8mm. One notable difference is that the R8 runs a dry sump oiling system, whereas the RS4 uses a traditional oil pan. Visually the intake manifolds look different -- I've not seen the R8 motor up close, but it's reasonable to believe that it uses independent throttle bodies, which add response, but do not affect overall power.

Comparing to the S5, the most notable difference is that the S5 runs an 11:1 compression ratio, whereas the RS4 and R8 are running 12.5:1. Their bore and stroke are identical (84.5mm x 92.8mm) which indicates that the cylinder geometry and rod geometry are also identical, and the difference in compression is caused by a difference in piston dome shape (or head gasket thickness, which is a lot less likely). Because the high comp piston was already a production piece, it's a pretty safe assumption that the lower compression piece was produced for the purpose of marketing, as stated above, so as not to clash with either the B7 RS4 or the upcoming RS5. So in theory, I can't see anything mechanically wrong with putting RS4 pistons in your S5 to achieve a bump in compression, which typically causes a significant increase in power across the entire powerband (and ironically an increase in fuel economy). The RS4 might have additional compensation in the fuel map, so I'd probably want to run an RS4 ECU and look into fuel injector differences in conjunction with this mod, just to be safe. On the other hand, being at 11:1 puts you in a better position to upgrade to forced induction, if you so desire.

On a side note, it's also noteworthy that the 3.2L FSI in the A5 already runs 12.5:1 so that amount of static load seems to be 'normal' for mass produced Audi components.

-Ray
 
#14 ·
'
Ray, great research and a really informative post. You make some good points about the engine's inherrent ability to handle the higher compression... maybe a good modification to think of once out of warranty... pistons or head/block skim... Must talk to APS!!

...Of course as I understand it, the negative of higher compression is the greater tendency to 'knock' and therefore the ECU must reduce the timing advance and compensate fueling, which reduces the available torque and limits the power gains.
 
#18 ·
Hahah...actually, everything you said does make sense. And i personally know what you mean about being young and not getting any help. I still think the G37 is still a good value considering a comaparble 335i is around 50k and an A5 is around the same. But I will say there are obviously some aspects of the G37 that no live up to the 335i and the especially the A5 ( looks/interior/quality). So, I just wouldnt say the car is miserable, but just my .02 cents :)

Sorry for digressing
 
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