ESFO

Trust me, since you enjoy playing the devil's advocate and the tireless cynic, you'll find some, silly, unfounded reason to bash it. You asked me about first hand knowledge.... Can you provide ANY evidence that our version of the 4.2 can't handle the horsepower that every MTM supercharged car puts out right now? Let me answer for you... 'No.' You can't. It's silly of you to suspect that this engine, with forged internals, won't be able to handle 470hp but a stinkin Mustang GT with it's cast internals can handle up to about 560hp with a supercharger. Which engine would you suspect is stronger, a V8 built by Audi with forged internals or a V8 built by Ford with cast internals?

You're just being a troll. Starting arguments against this forum's model just for the sake of arguing.

ESFO

just before I left work but had to leave. Good lesson.

ESFO

-sigh-

RI A6

There are only a few superchargers in the world that have ever seen this engine. So, there really isn't much data on whether or not the block and internals can handle the power. I'm behind the curve on MTMs latest supercharger for the S4, which has been going to come out any day now for 2 years. However, if it's been through MTM's testing I'll except that it's reliable, since they never produce a crap product.

An 8K supercharger would be a great deal. If it had come along 2 years ago, it would have made the decision to trade from a B6 to the RS4 much more difficult for me. As it is, I've had a year now of driving a beautiful car, and will continue to enjoy it.

Nothing I said was meant to belittle your cars in any way. I was asking questions, clarifying and adding my own information. And, in the process I also learned. I have trouble understanding why people are so sensitive to facts and discussions. If I'm wrong, I'm wrong and I admit it. If I'm right, I stand by what I say. Right now the only supercharger available for and S4 is 25K. When an 8K unit becomes available, it will change the entire equation, which I'll freely admit.

Ultimately, there is always a faster, more powerful car out there. I'll enjoy mine for now, and possibly look forward to the day that MTM releases their supercharger for the RS4 and I can struggle over whether I "need" it or not.

RI A6

ESFO

I don't mean to frustrate you. I think we're both saying the same thing and are getting caught in between by leaving some things out. The Chevy kits work because the engine is not near it's intake efficiency limits. The gains are big because Chevy left a lot on the table. The 350 cu small block kit puts out 435 horsepower @6000 rpm, which is great. But, when you compute the power to displacement ratio it's 1.25:1

If you take a look at the S4 V8. Displacement is 256 ci, with 340 HP @7000 rpm, for a power to displacement ratio of 1.33:1. But if we normalize power to 6000 rpm, we get a ratio of 1.14:1. So the S4 is a bit less efficient than the Chevy at the same rpm.

So, if we assume that the Chevy kit is about as efficient as you can get. And that we could do the same with the S4 engine, then we'd need to produce about 10% more horsepower, to bring the output to 373 HP. I'd call 10% a minimal gain.

My point, which was not well made, is that the S4 engine is already very efficient in developing power. It takes a lot of work to get the last 5% to 10% additional power out of her. The intake manifold is actually a pretty good and efficient design, and uses exactly the same ram techniques as the Edelbrock manifold on the Chevy.

The Audi engine has the advantage of a two stage ram. Peak torque on both the Audi design and the Edelbrock design are set by the length of the manifold runner, which creates a tuned resonant cavity, which produces some slight boost at the torque peak. With the Audi design (which is certainly not unique these days) the dual manifold allowed the designers to tune two torque peaks. One low end and one high end. Tuning the torque peak and moving them around really is as simple as changing the length of the intake manifold.

In the RS4, the designers re tuned the high end peak in the intake manifold, by making the high rpm path shorter, to accommodate a higher rpm range. They also introduced an additional opening in the intake chamber to allow more air flow at high rpm. Otherwise the intake system is not much different than the S4.

Air filters on the intake side of the manifold can have very little impact on the overall flow, if they are already well designed. And the Audi design is executed pretty well. The intake pipe and MAF sensor seems to be well designed, with a large amount of surface area, for low pressure differential, and is used unaltered on the RS4, so flow there has to be good. There are possibly slight gains to be had, but nothing huge.

I just don't think there's much to be gained, if anything, on the intake side. Which was also what was concluded on the Champion ALMS Challenge car, which used the stock intake system.

The S4 exhaust header could be improved significantly. It pretty well sucks. But without improving it, downpipes and catbacks will only provide small gains. The header could be tuned to work with the intake peak, this might allow more power than just downpipes and catbacks. But still, without some cam overlap changes, there might not be much more that the engine can use.

The S4 owner shootout shows gains with exhaust and chips of 16 to 28 Hp from a baseline of 257, for gains of 6% to 10%. This puts the gains pretty much dead in line with the Chevy kit, on a per cubic inch basis. I don't think that 6% to 10% is a very big gain at all, which is why I called it small or minimal.

I never meant anything derogatory by this. The engine is what it is, and is a pretty efficient design already.

405Z

It's what gives you the kick in the *** when you push the accelerator, it's what makes a car driveable on the street so that you don't have to constantly drive at 6000 rpm. That's the attraction of American muscle for a lot of people. That's why personally, I couldn't give a crap about the hp/liter argument because a 2 liter engine making 250 bhp but 120 lb-ft is something I'd never be interested in.

ESFO

In my first post I stated that if you are talking about available mods for the S4, yes, possible gains will be minimal. But, as with any other NA V8 more power could be made with other intake/exhaust modification, cams, headers, extrude honed heads, shorter runner intake (a'la RS4). I understand your efficiency ideas but neither that Chevy engine nor this S4 engine is making as much power as it could with even further modifications. Maxed out, without FI, that Chevy motor is probably capable of about 750hp. Unfortunately, none of those 'RS4' mods are available for the S4 (better intake, heads and headers), so one can only speculate.

You and I can agree on some points and agree to disagree on others.

Corrado79

It's not that "people are so sensitive to facts and discussions." It's that you argue in circles just to avoid admitting anyone but you is right. It's definitely annoying and quite sophomoric. I can understand ESFO's frustration.

Now you will respond, because you are obliged to based on your "-itus," with how wrong I am and how right you are, or maybe how you are just stating facts or some other seemingly-innocuous statement.