I am a bit curious why would Audi do performance upgrade on the RS4 engine to bump up the HP to 500? They are testing the RS8 using Gallardo engine and de-tuned it to 500 horse. In term of perfomance, the RS4 with 500hp on V8 would out perform 500 hp V10 because of power to weight ratio.
Does anyone know if the steering wheel on the R8 or Audi TT fit on RS4. I like the multi-function Sport steering wheel. Any audi mechanic or engineer can answer this?
04-12-2007, 07:07 PM
04-12-2007, 07:10 PM
certification for changes and the marketing ROI
04-12-2007, 07:12 PM
04-12-2007, 07:16 PM
04-12-2007, 07:37 PM
It is possible to retune the intake for a higher rpm torque peak, which would push power up, but then the engine would be more peaky. It might even be possible to do this with the current manifold by adding some tuning slugs inside, to raise the resonant frequency of the high rpm intake path. But, this would require an ecu change to modify where the intake flap kick over, and might cause a drop in torque in the midrange. If this were coupled with an exhaust manifold designed with similar tuning, it might be possible to get even more than 50 HP out of it, but it would not be a streetable any more, and tough to drive on a track if rpms dropped below 5 grand.
04-12-2007, 07:48 PM
Unless the injectors are change to a higher capacity which probably would give more hp
04-12-2007, 07:57 PM
This is direct injection, not manifold injection. The injector flow is controlled by the open time, which at max rpm is about 3.5 milliseconds, and by the fuel rail pressure, which is under closed loop control and can be pushed up to 1800 psi.
The current engine is pretty well tuned. I doubt no cats will increase flow that much, unless coupled with an exhaust header tuned in conjunction with intake manifold tuning. Performance in this engine is limited by flow. And flow is not that bad.
04-12-2007, 08:14 PM
You guys seem to have alot more capacity than the turbo FSI guys. I was up to 9ms on times before we bumped fuel pressure and then was still at 7ms. Whne the tubo was upgraded it was at 9ms again.
04-12-2007, 08:21 PM
It depends. Remember that the fuel rail pressure is also controlled.
Here are three different logs at 6000 rpm
InjectionTiming ThrottleAngle FuelRailPressure Lambda
2.55 ms .........99.2% ......... 112.14 bar ...... 1
3.06 ms .........99.6% ......... 113.04 bar ...... 0.85
0.77 ms .........24.7% ......... 35.33 bar ....... 1
113.04 bar = 1640 psi fuel rail pressure
max is 125 bar/1800 psi
04-12-2007, 08:28 PM
So if it is set to run around 110bar (which coincidentally is what the turbo FSI was set to run) you should be seeing that on a WOT run. It'll fluctuate. Say it was programmed for 110bar, you may see from 105 to 115 spikes but you should be able to draw a line through that log and see an average of whatever...say 110bar. It looks like 3ms give or take huh? Not bad at all. That does appear to be plenty of room. The turbo cars will need bigger injectors with their higher hp kits, probably with their K04 kit to maximize it too. You guys are lucky bc my guess it they will be expensive.
04-12-2007, 08:36 PM
04-12-2007, 08:37 PM
04-12-2007, 08:49 PM
At 6000 rpm specified pressure is 112 at WOT. Above that they set it at 115 with a 3.06 open time all the way out to 8000 rpm. Longest open time that I see is 3.57. At 8000 rpm 360 degrees of crank rotation is 7.5 ms. Usually you want the injection period to be less than 180 degrees with direct injection, so that the spray is distributed by the intake swirl pattern. That sets the max injection time at 8000 rpm to 3.75 ms. Which says that for the RS4 engine, if we could somehow increase flow, there is still headroom for 25% more horsepower. Funny thing, thats 525 Horsepower, pretty damn close to the 540 HP that MTM claims with their supercharger.
If we look at the 2.0 TFSI engine at 6000 rpm, then 360 degrees of crank rotation occur in 10 ms. I'd say the 7ms and 9ms would be too long to be contained within the intake stroke. The spray will then continue significantly into the compression stroke. This will probably cause wetting of the cylinder and piston crown.
I bet those tricked out TFSI engines have one hell of a problem with fuel dilute in the oil.
04-12-2007, 09:09 PM
but obviously there would be sacrifices to be made elsewhere.
04-12-2007, 09:10 PM
Currently the injector on time is not optimal, since it remains on for more than 180 degrees. So higher flow injectors will help ... if, and only if, the fuel rail can keep regulated pressure up at the higher flow rate. But those injectors are a lot harder to design and manufacture than the old manifold injectors, so they will be spendy.
Bigger injectors might also require modifications to the rail pump and/or regulator, if either cannot keep up with the increased flow. If that were to occur, then it could get ugly, and very expensive.
04-12-2007, 10:14 PM
04-13-2007, 12:21 AM
Many states are moving to OBD port based emission testing where they basically hook up to the OBD port and look for codes to see if all with well with your emission controls.
04-13-2007, 03:31 AM
04-13-2007, 04:02 AM
The ? how do I get more out of this already great package seems to be gaining steam. Makes sense as more cars get in the hands of the US market, and people worry about BMW M3 etc. I'm not going to loose sleep over it. I agree Audi will not make upgrades for FSI V8 with the V10 in the house. If you want more power call MTM and get on the list. There superchager could be short lived. You can have it for that price. RS4 didn't get Performance Car of the year for nothing.
04-13-2007, 04:36 AM
I present Exhibit A: the E39 M5. 400HP out of a larger 5 liter displacement. The best tuners in the world can barely get another 70HP (hotly debated, apparently the 70HP can only be had on Dinan's dyno). Called the Dinan S2 package, it will cost you $25 grand. Four new cams, eight new throttle bodies, new extruded aluminum intake runners, $8-grand headers, exhaust, chip, $2 grand CAI, $2 grand diff., suspension, wheels, tires, etc. All that, I don't know of anybody who could document that their S2 is faster in the 1/4 mile than a stock E39 M5.
04-13-2007, 05:37 AM
I realize it might be hard to believe, but the German engineers are even smarter than us ;)
The common paths to more HP - higher RPM and higher compression - are already up in the stratophere on the RS4. The RS4 engine is displacement-challenged, but bore/stroke is likely cost-prohibitive if not impossible given block dimensions.
Audi isn't going to leave much - if any - HP "on the bench" for (which once was) their flagship performance car. The car is done rung-out, modded to the max, seriously hot-rodded. Any HP increase will come at a ridiculous price and comfort compromise. I'm estimating about $300 per HP increase for the first 10HP, then upwards of $500 per HP up to 30HP. After that, don't ask! (blower)
Personally, I can appreciate the balance that the best automotive engineers in the world have given the RS4, so I'm trying hard to resist the mod bug (for now).
04-13-2007, 05:45 AM
At least not from this motor. The RS4 engine is already very "peaky" and eager to rev. It is not an easy vehicle to drive smoothly at lower speeds. Around town driving requires near perfect balance of clutch and accelerator -much more so than any car I have previously owned, including my Stage 3 B5 S4. My RS4 is a daily driver for me and while more power is always fun under the right set of circumstances, I wouldn't want to sacrifice the car's daily driveability any more.
04-13-2007, 06:04 AM
04-13-2007, 06:54 AM
You guys have to get past this whole removal of the cats nonsense.
I've yet to see anything on this motor that shows tha a) anyone can do ECU tuning to handle the check engine light issue that will surely arise; b) to overcome the prospect that removing the cats, while it may increase hp in the upper rpm ranges, will most certainly cause a loss of low end torque or at least in some rpm ranges....hardly a good compromise, unless you're drag racing this car.
Unless some does a fully tuned/matched exhaust sysem from headers back, I can't imagine their being much chance of seeing an increase in torque AND hp across the rpm band.
AS for the intake, the runner's length is optimized for torque already. Going to a revised intake with shorter runs will likewise move the powerband upwards with a loss of torque down low. The Mustang guys have known this for years, so don't get excited about exploring that route.
At best, I think we can hope for proper ECU tuning (10-20hp) and possibly a cold air intake for another 8-10hp. Beyond that, this motor's static compression and camshaft profiles seem to be close to maxxed out for drivability and performance, so I would not expect much more than that.
I'm also growing tired of the MTM wild card assertions...a) no one's going to pay $15K for this kit, let alone $25K and lastly, the car they're testing is a shop mule...I'm sure it's hacked, duct taped and zip tied together. When I see one done, on the road, with dyno charts, here in the US, I'll get excited, until then, it's no more realistic than fission fusion passenger cars in my book.
One thing you have to remember: this car is EXTREMELY low production...from any company's perspective, producing parts for a low run production vehicle with a low number of customers who would potentially modify their cars means that parts are going to be 2-4 times more expensive than comparable Mustang parts. The Ferrari and Lambo guys live with this fact.
Looking at the intake manifold, probably the best option is a direct port nitrous system, assuming someone can figure how to make it work on an FSI motor....but if you do, say bye bye to your powertain warranty and few guys would be smart enough to run colder plugs and narrow the spark plug gaps to compensate.
In short, if you want 500hp, go buy a Gallardo or an M5. Otherwise, enjoy the world's best performance sedan.
04-13-2007, 10:05 AM
and is done on the turbo FSI cars and the S4 cars by mulitple tuners for track use (APR has one for me). I have also never seen a loss of torque from running straight pipes. I know there is a rumor out there that this is the case but i've never seen it happen on any audi i've had. Removing back pressure can also improve low end torque.
04-13-2007, 10:15 AM
Modification of the intake manifold for high end torque would not effect low end torque, due to the dual runner design with the intake flap. What would happen is that mid-range torque would suffer slightly, and torque would peak at a higher rpm. About the best that could be done would be to move the torque peak to 5850 rpm, instead of the current 5500 rpm. This would cause a slight 4K to 5K rpm torque dip, and change the midrange HP slope, but would increase HP at higher rpm, and keep it continue to climb up near redline. This would have to be done with an ECU recode to change the flap actuation point to 5850 rpm, and to stop the throttle body shutdown right after 7800 rpm, where it goes from full open to half open, and delivered horsepower drops of the face of the earth. With these changes, a good 20 to 25 more horsepower is available ... but you'd have to keep the engine wound even more tight that it already needs to be.
The exhaust manifold is already a pretty good design. It's a 4:2:1 design, but the lengths are a bit short when compared to the R8 design, where they had more room. The current design looks to be pretty well tuned, and provides good port-to-port isolation. You should not lose low-end torque with higher exhaust flow, since this is an isolated port design, and should not benefit from back pressure. This is borne out by dyno plots that show torque increases across the entire rpm range, when switching from factory to Milltek catbacks. Back pressure is generally only an issue when working with a unified cast exhaust manifold, where all ports dump into one chamber.
To effect a 10 HP increase with a cold air intake would require a net intake temperature decrease over stock of 22 F. I don't have enough feel for the air intake design of our engine, and temperature at the MAF sensor. At first I thought that a cold air intake would not provide much benefit, but after I ran the numbers, 22F does not seem to be a huge temperature differential after all.
As for ECU tuning, I'd still be surprised if there is much that can be done in that regard. A/F ratios are already optimal at WOT. Timing is already automatically adapts. About the only thing left as low hanging fruit might be the variable valve timing. Some more overlap might be allowable with higher flow intake and exhaust. But boy, I'd be really concerned about burning valves. Right now, even if the throttle body is kept open above 7800 rpm, and the injectors keep firing, you aren't going to get any more horsepower out of the engine up to redline, since flow has been limited up here by the intake runner design. The only way to open up the band between 7800 rpm and 8250 rpm, is to shorten the secondary intake runner (as described above), and move the torque peak up by 350 rpm. Then an ECU remap could produce peak horsepower at 8150 rpm.
04-13-2007, 01:41 PM
I was working off the notion that someone would radically redesign the intake, hence they would NOT retain the dual flap design. But you're right...if they're modifying the stock piece, the car would probably respond exactly as you predicted.
I'm going to reserve judgement on the benefits of removing cats on this motor until someone shows a dyno plot to substantiate that the power band has not suffered in some area. If you have some data, it would help everyone here make future parts-purchasing decisions, but again, these plots only apply if they're for stock RS4 motors, not pro-built race motors.
As for the CAI, I suppose it depends on where the air is picked up from...if the unit runs inside the fender, would it pick up colder air than from the engine bay? And how does the surface temperature of the road affect those intake temps on hot days? Will be interesting to bear out.
With respect to a/f ranges being "optimal", that term is not descriptive enough. What are you calling "optimal" and what data is available to show what happens to this motor's powerband above or below certain a/f ratios?
Ultimately, I think we agree on the basic premise of this thread: getting more than another 20-30hp out of all the basic mods combined (intake, any/all exhaust mods and/or ECU retuning) will be difficult...and not without sacrifices to the driveability, power band or reliability.
Of course, if any tuner would like to prove me wrong, I'd be first in line for their power parts.
04-13-2007, 01:46 PM
04-13-2007, 05:20 PM
and if I did I sure wouldn't be posting and bragging about it online. As far as the cats go I just don't care for them in any car. It's a restriction and it seems that they can get blocked over time and decrease performance. With the amount of carbon coming out of our exhaust I can't imagine that they will self clean and blow all of that out. They will probably just slowly clog.
04-13-2007, 05:28 PM
04-13-2007, 05:31 PM
04-14-2007, 06:19 AM
Of course I would love more power, but, at this overall performance level (as opposed to a lower performance level car), I am not willing to sacrifice drivability and comfort to get it.
Really, for me, it's the angel on one shoulder telling me to be happy with the already amazing car, and the little devil on the other shoulder saying MORE, MORE, MORE. In the end, the devil will probably kick the **** out of the angel, but I'm not there yet.
04-14-2007, 08:42 AM
04-14-2007, 04:59 PM
difference in Dyno plots for sport on and off (I thought + or - 4 or 5hp). It was a long time ago and may have been on RS246.com. Of course it could all be BS.
04-14-2007, 10:32 PM
Might have been a normal difference between dyno runs. But a WOT all settings for the engine are the same above 5000 rpm, whether or not you are in sport mode.