DrVolkl

Is APR going to change the tune to work with the pulley... or will tune not even know there's a difference? I'm curious to see how this all pans out.

sakimano

what's the pulley ratio, stock?

as for the tune traditionally these ECUs are able to adapt to increased air flow on their own, but I'm not sure when you swap a pulley. Again, more SC vs. NA stuff that changes everything. I'd bet a coke you'd need to be tuned for new hardware.

Here are my thoughts on the 1320 map, in very simplified terms
1 M3/hr of flow = 0.59 Cubic Feet per Minute of air = 0.39 HP (provided you have adequate fuelling)

Ok...so using that rationale, and the fact that the blower might need 20-30hp to run the thing (they're parasitic) you end up with the following. Could be 15...could be 40. Not sure on that. Let's say 20hp at the efficient 11000 rpm spot and 30hp at the inefficient spot at 17000rpm. If anyone knows, chime in.


11000 RPM = 850 m3 = 501 CFM = 331 hp - 20hp = 311hp net at the crank
Deepest part of the lake

17000 RPM = 1350 m3 = 796 CFM = 525 hp - 30hp = 495 hp net at the crank
This is a very inefficient spot so I'm not sure how many of those CFM flowed are turning into 0.66 hp...lots of hot air gets flowing when you're at the extremes on these blowers, and we all know that's less dense, thus less o2 thus less power.

Anyway, it appears to be good for up to around 500hp crank in this application if I'm not totally wrong. That's about 400-425WHP...pretty awesome. Wonder what the injectors are good for.

p.s. anyone else thinking the same thing I am? How the **** is APR getting way north of 500hp out of the RS4? Maybe my math is off...but it appears the blower would be under extreme stress unless they did some trickery to it?

p.s.s. I can't get a TVS1650 compressor map. What's with that?

MadMadS4

no need to bet. APR has already said they'd provide new software to go with their new pulley.

http://forums.quattroworld.com/s4b8/msgs/12197.phtml

NWS4Guy

Unsure of the parasitic losses, APR has stated that the injectors are actually very overengineered when they started working on their race car, they are good for far more pressure than stock will ever need, and they said an upgrade would be very unlikely needed.

How are they getting over 500 out of the RS4 is not so hard to see. The engine was designed as a NA already and had a pretty high compression ratio. As a result, the new injectors to add more fuel, the small identical R1320 we have on our engine to add more air (not much is needed or would be tolerated with the already high compression on this engine) adds the air needed for the extra fuel, intercooling for a cooler overall air charge to further add density to the air in the cylinder, and changing out the timing to be more aggressive. These factors all work together to increase overall performance.

voltrons_head

I'd be lieing if I said that I could be more than an observer in the conversation at this point. Sorry.

FWIW - I am playing along at home though.

sakimano

I think you're on the right track, but the fact is pretty simple...air is air. If it can't flow more air, it won't make the power.

The Eaton M90 kits for the RS4 and S4 are a great example. They make around 750CFM max with 35 hp losses. a.k.a. 465hp. While the RS4 makes 400ish stock a supercharger adds power (via CFM), but really doesn't add a ton.

case in point - SC B6/7 S4 with M90 = SC B7 RS4 with M90

flow is flow, no matter what your other jumping off points are. In fact the fastest M90 SC Audi 4.2 is a 2005 TIPTRONIC S4 sedan with almost no mods other than the charger, downpipes and catback. Faster than the PES RS4 that dynos 440WHP. Faster than the VF RS4 whose owner claims he walked a Z06 (snicker...sound familiar?)

Take a B6/7 S4 with headers and 2.5" exhaust and JHM manifold and you're making RS4 like power (thanks to awesome volumetric efficiency). The M90 really doesn't add too much to that car either...but put it on a stock S4 with bad headers/bad manifold/2.125" exhaust and you've got huge gains over stock.

Think of a ladder...the top rung is the top rung and can't get you any higher no matter what step you start climbing from.

Since you guys think I 'hate' the B8...and prefer the B6/7 S4/RS4 over all else consider this prediction:

The B7 RS4 with TVS 1320 supercharger will be nominally faster or equal to a fully modified B8 S4. By FULLY I mean headers (that work), GOOD catback, 100lbs of weight loss to match the RS4 curb, goof stage whatever tune etc.

Full bolt ons B8 S4 = TVS1320 SC RS4

rktskicar

Stock pulley ratio is 2.5:1. Upper 60 mm, lower 150 mm.

Bruce

MadMadS4

APR, GMG and Stasis are all planning pulley upgrades. What we don't yet know is what the new ratios will be and what the constraints are.

- APR stated they'll have a smaller pulley. With a smaller pulley, the concern is whether it'll have enough surface area to actually grip the belt, so I'm concerned with that constraint.

- GMG stated they'll have a larger pulley (at the crank) to change the ratio. With this - it would seem you could go significantly bigger, dramatically altering the drive ratio. However, is the constraint, then, the actual breakage of the SC?

- Might it be possible to do both pulleys? (personally I wouldn't risk damaging my SC)

NWS4Guy

Good summary and points all around.

I don't think APR will release anything that is garbage, so while it will have less of a grip area, there is no more stress that there will currently be, since it's spinning the same parts, just less contact area, so the overall pressure per area of belt will increase, still shouldn't be an issue really, look at the amount of accessories the similar sized belt is spinning all at the same time.

GMG, no data on it yet really, they seem to have a pulley and no software, so not a ton to gain here, since the bypass will still close off, and even getting more boost before this happens won't pan out with what the stock ECU is expecting so it might just open the bypass ealier depending on what the sensors report back with no tune, negating ANY gains.

I would never recommend doing both, nor going larger than GMG, or smaller than APR, the SC bearings have a max speed tolerance, and going far beyond this will aboslutely result in a failure.

LeadToRome

I don't think you hate the B*, I think you like your car. That's cool. You bring good info but you're also sort of pedantic and annoying at times. Hey it's the internet, who cares. Keep on truckin'.

edit,: Very weird. There's an "eight" in my reply but it turns into an asterisk when it's posted. I just tried three times to fix it. Oh well.