How far can the RS4's stock motor be pushed?

B6/7 S4/RS4
#1

So with JHM getting the JHM supercharger on the RS4 this year…and with TTS making good power, runnning 11.4 @ 125…and with AMD putting a TVSr1900 kit out (maybe) and an option for a TVSr2300 kit…etc…I thought I’d put this out there.

How much power do we think the RS4 can handle before it goes boom?

Here’s what we’ve seen so far

APR TVSr1320 supercharger kit - made 435 whp on their dyno. This is not enough power to stress a B7 S4, let alone an RS4, but hey it’s a start for our list.

TTS Rotrex C38-91 centrifugal supercharger kit - made 610 crank hp on the MRC dyno. Made 485 whp on another dyno in the UK on an S5. Not sure if we’ve seen anything else. This is about as far as we’ve seen the RS4 pushed so far. Looks like about 500 whp is pretty comfortable, as TTS have these kits on about a dozen cars so far. Maybe they can chime in? Have they dyno’d a race file?

This is all we really have on the RS4…but as we know the RS4 and the R8 share a motor (or most of a motor). To that end, let’s have a look at what we’ve seen for the R8 4.2.

So…that’s interesting. 536 rwhp (they measured this at the rear wheels for whatever reason…and I can’t remember what that reason is). They also claim 600 whp with a race file (but showed no proof/dyno). They showed no quarter mile times that I’m aware of.

On this topic, the R8 4.2 Heffner twin turbo kit was being run by a customer who wanted some changes made. He road courses the car a bunch and found the tune that came with the kit was pushing the car too hard and pushing him into heatsoak, so he needed a tune that made less power…so he called APR. :smiley: Just messing arin/keith. He was a good APR customer and wanted a tune that addressed his needs and APR did a good job, writing him a lower boost file (6 psi)

APR dyno’d the R8 4.2 Heffner with APR calibration on their hub dyno, and then overlayed their RS4 supercharger dyno. The dashed lines are the Heffner R8 making 500 whp / 425 wtq with the revised tune. The solid lines are the APR RS4 4.2 making around 435 whp and 370 wtq. Thanks to arin for posting this info on AZoo.

http://www.goapr.com/news/wp-content/uploads/2012/04/r8-vs-rs4.png

The only other currently offered kit that might make good power would be the VF Engineering/Stasis R8 supercharger. I believe it used a TVSr1900. That should be capable of about 500 whp…anyone have info on that? I found a quarter mile time…12.3 @ 116. Frankly that’s pretty terrible. DA was 700 feet. No idea what the story behind that is.

Here’s another R8 4.2 with the Heffner kit, upgraded fuelling and an EPL tune. 550 whp 460 wtq

http://a1.sphotos.ak.fbcdn.net/hphotos-ak-snc6/270552_10150243581279774_151673719773_7140680_289529_n.jpg

Anything else along these lines?

#2

80hp/cyl is pretty damn good if you ask me.

#3

Do we know of the metallic properties of the rods in the R8 are the same as the ones found in the RS4? If so I think the R8 could be used as a pretty good measuring stick.

If I had to guesstimate JHMs numbers on the stg 1 RS4 s/c kit I’d say ~550 wheel depending on where the v3 is in terms of efficiency at that point. Also depends on if they work an intercooler solution into it. I think we all know the tuning is going to be top notch, 550whp should be getting into the 10s. We’ve seen what a bolt on car can do stg 1 should be a different car. Then with the blower maxed out…well that should just be silly.

Btw I’d chalk up that shitty vf s/c 1/4 mile time to terrible tuning…it’s gotta have more in it than that

#4

You covered the examples i would have used. Based on those examples, I don’t think most RS4 owners would feel comfortable going beyond 550WHP on stock internals, maybe I’m wrong. There aren’t enough long term examples out there to review confidently.

All exciting stuff though. Looking forward to the coming year and the options that become available to us.

#5

The R8 and RS4 share the same short block as far as I recall. The differences that I remember; intake, exhaust and the R8 is a dry sump system. I think the rest is identical.

#6

Yeah in terms of longevity I don’t see the point of going past 550wheel on a stock motor. The amount of power it will make is going to be killer as is.

#7

Yes beyond 550 whp would be uncharted waters…525 would be a very very strong car, considering everything else.

If the ttsrs4 trapped 125 on a config that dynod around 600 crank (480 whp we can guess?) It will be interesting to see what 525-550 can do.

Danny (ttsrs4) the 11.42 @ 125 car, appears ready to push the limits lol. He speaks of a nitrous add on to the tts kit and a 100 file to boot!

#8

^ That is hardcore lol. I read where he said something like “I gavew them permission to blow the motor during testing…” WHat?! LOL, cheers to him, helping the rest of us move forward with new found info on our motors minus the costs associated ;D

#9

I have a spare lol :wink: ! My engines out just now and it’s with Richard and darren at tts. It’s being stripped to see how things are, baring in mind I’ve ran three supercharger kits and nitrous plus the car is driven hard on almost every occasion! I’m looking at doing rods and chucking on a 100 shot of nos just to see how fast the car can go! Btw I’m having forged 3piece rims made will these help bring the time down? They will be really light

#10

^^ What rods have they chosen?

#11

More a case of what rods will I choose, I’m looking at options just now. One of the techs at Mrc was an f1 trainee he has contacts at various ‘high performance’ places who could make one off pieces

#12

That’s pretty hardcore but weren’t you going to try and blow the stock motor up? I was excited to see how far you could push it! Either way keep us posted.

#13

I’ll see, the engine is out as I’m doing a colour change so it would be daft not to build it wouldn’t it? I’ll wait and see what richard comes back to me with

#14

I’ll talk to the development engineers and see what they think about making rods on this lol…

http://upload.wikimedia.org/wikipedia/commons/a/ac/Wyman_Gordon_50000_ton_press.jpg

#15

lol

danny, wheels will help a bit. What’ll they weigh? The potentially wider tires might help you launch.

what colour are you changing to?

#16

Not sure on weight as of yet but lighter than stock. I’m sticking with 19’s but going with a stagger to try make the rear look phat. Colour is secret :wink: interior has been overhauled as well

#17

Just curious, but two questions that come to mind.

  1. Is there anything to be addressed with the extra boost considering how high of compression the RS4 is from the factory?

  2. On the JHM kit, what type of PSI are they going to need to run in order for 525-550whp? I’m just thinking if 6.5-7 psi is needed on the S4, and we’re speaking of airflow, is that going to be reaching a PSI where cooling needs more addressing. I know Stg II & III S4 are looking at meth & IC, but hadn’t heard on the RS4. I’d think that meth might at least be part of the RS4 stg I, but I really don’t have the understanding of forced induction that they do obviously.

#18

Good questions - which made me think of some too:

Do we know what JHM’s goal is power wise? Do they even set an awhp goal? If I had to guess I’d say no but i have no clue.

With the RS4 being quite efficient in stock form, once a proper 2.75" exhaust is thrown in the mix I wonder if the PSI’s would need to move up at all. It may be possible to keep them in the same range as the S4’s all while producing more power. Or…so they test out 8 psi for shits and giggles based on the RS4’s robust short block and go from there.

No idea - all fun stuff to think about though.

#19

I think they definitely set a power goal as part of their due dilligence on choosing parts. They wanted a supercharger kit for a couple of years before ‘settling’ on the V3

I think they have a goal, then source parts that should reach that goal after doing the math, then build the system, and run it to an efficient and safe level. Then they performance test the car (logging, dragstrip). Then they dyno the car to confirm some of the info.

Then they do it all over and over till they’re happy. Then they tell us ‘oh by the way, we made a supercharger kit’. lol.

We’re all wise to them now, so they kinda have to pre-announce some stuff (although they’ve gone back to being eerily quiet lately).

#20

Yeah, my statement was not thought out well at all. They obviously have a plan to follow which includes like you said, math and a build that follows. When choosing the S/C they looked at the maps etc and probably arrived at a rough target power number. Curous as to what that will be for Stage I. If I had to guess it would be 500 whp give or take a couple.