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Thread: S4 vs S5 engine

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    Senior Member Two Rings hayasa's Avatar
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    S4 vs S5 engine

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    What are the differences? Both seem to be pretty similar, or at least more closely related than the S4 and the RS4. Any ideas why the S5 get 354 hp and 325 tq?

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    Veteran Member Four Rings ieatfishburitos's Avatar
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    Re: S4 vs S5 engine

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    Re: S4 vs S5 engine

    s5 and rs4 are the same motor......

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    Senior Member Two Rings hayasa's Avatar
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    Re: S4 vs S5 engine

    Quote Originally Posted by fitzS4 View Post
    s5 and rs4 are the same motor......
    Really? But the RS4 has 317 tq, so something had to be different. Can the S5 rev to the same level as the RS4?

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    Re: S4 vs S5 engine

    b6/7 s4's are 40 valve 4.2 liter v8's while the s5/rs4 are 32 valve 4.2 liter v8's.

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    Re: S4 vs S5 engine

    Quote Originally Posted by hayasa View Post
    Really? But the RS4 has 317 tq, so something had to be different. Can the S5 rev to the same level as the RS4?
    no it can not but yes they are mostly the same. the difference lies in the pistons since the rs4 has a 12.5:1 compression ratio while the s5 has an 11:1 and also the camshafts where the rs4 has a much "hotter" cam which allows it to rev to 8000+ but yet hurts it in total torque output. also the heads on the rs4 where given some lovin in order for them to flow that added air. also check the peak torque numbers and you see that the rs4 makes all 317 at a rather high 5500 rpm while the the s5 is at i believe 3400 which is a testament to its lower compression and milder cam setup.

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    Re: S4 vs S5 engine

    ^hayasa just got owned

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    Senior Member Two Rings hayasa's Avatar
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    Re: S4 vs S5 engine

    Quote Originally Posted by 91gl View Post
    no it can not but yes they are mostly the same. the difference lies in the pistons since the rs4 has a 12.5:1 compression ratio while the s5 has an 11:1 and also the camshafts where the rs4 has a much "hotter" cam which allows it to rev to 8000+ but yet hurts it in total torque output. also the heads on the rs4 where given some lovin in order for them to flow that added air. also check the peak torque numbers and you see that the rs4 makes all 317 at a rather high 5500 rpm while the the s5 is at i believe 3400 which is a testament to its lower compression and milder cam setup.
    Very cool. You all are quick!

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    Re: S4 vs S5 engine

    Quote Originally Posted by hayasa View Post
    Hmmm. Then what is the difference between the RS4 and S5 engines? They are rated with totally different specs...

    see above post


    the s5 and rs4 have the same basic engine specs. bore and stroke are exactley the same. it all comes down to the cylinder head. think of it like this, even though it is a bit graffic, you will understand it more fully.

    what requires more "thrust", pooping in a toilet or pooping through a straw? that is your torque. it requires more force (torque) but yet it does not flow as well as an open toilet would. now that is your top-end horsepower and also why the rs4 makes less torque than the s5. the compression is higher but since the exhaust ports where reworked in order to flow better, the gasses (poop) flow out alot easier so they can accomodate the added air coming in because of the hotter cams.

    *i did not make this up myself, i am just quoting a fellow dubber from when i had my corrado and we were talking about port and polishing cylinder heads. I wish he was on here because he could explain it alot better than i could
    Last edited by 91gl; 12-18-2008 at 08:13 PM.

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    Re: S4 vs S5 engine

    Quote Originally Posted by 91gl View Post
    no it can not but yes they are mostly the same. the difference lies in the pistons since the rs4 has a 12.5:1 compression ratio while the s5 has an 11:1 and also the camshafts where the rs4 has a much "hotter" cam which allows it to rev to 8000+ but yet hurts it in total torque output. also the heads on the rs4 where given some lovin in order for them to flow that added air. also check the peak torque numbers and you see that the rs4 makes all 317 at a rather high 5500 rpm while the the s5 is at i believe 3400 which is a testament to its lower compression and milder cam setup.
    The funny thing is the S5 is just as fast as the RS4 with such a "discrepancy" on paper statistics...

    here is just one source (edmunds article)
    354 hp Audi S5: 13.3 1/4 mile @ 104 mph
    420 hp Audi RS4 13.2 1/4 mile @ 106 mph

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    Re: S4 vs S5 engine

    Quote Originally Posted by Swanky View Post
    The funny thing is the S5 is just as fast as the RS4 with such a "discrepancy" on paper statistics...

    here is just one source (edmunds article)
    354 hp Audi S5: 13.3 1/4 mile @ 104 mph
    420 hp Audi RS4 13.2 1/4 mile @ 106 mph
    There are plenty of guys with rs4 that have ran 12.8, 12.9 with the rs4 stock. Has anyone taken their s5 to the track yet to see what kind of times they get?

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    Veteran Member Four Rings GotRS?'s Avatar
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    Re: S4 vs S5 engine

    Not for the question of S4/S5 but a good read anyway

    Here are the differences for those that might think that the RS4 engine has only a few minor "tuning" differences. These come from the Audi 4.2-liter V8 FSI Engine Self-study Program

    The main technical differences between the base Q7/S5 engine and the high-revving engine lie in the following:

    * Crankshaft/connecting rods/pistons
    * Timing gear
    * Cylinder head
    * Oil supply
    * Engine cooling
    * Intake path
    * Exhaust system
    * Engine management


    The cylinder crankcase of the high-revving engine was machined to higher specifications due to the higher stresses in this component. To minimize warping of the cylinder manifolds, the crankcase is honed under stress. For this purpose, a honing template is attached to the crankcase before the honing process in order to simulate the warping of the bolted-on cylinder manifold.

    Modifications to High-revving Engine
    At very high engine speeds, axial vibration occurs due to the unbalance in the single-mass damper. This can cause the crankshaft to break.

    To avoid this vibration, a dual-mass damper without unbalance is employed in the high-revving engine. To compensate for unwanted engine vibration, heavy metal inserts are integrated in the first and eighth crank journals by way of unbalance.

    Connecting Rod
    Cracked connecting rods made of 36MnVS4 are used in the basic engine, while the conventionally split connecting rods in the RS4 engine are made of 34CrNiMo8, for strength.

    In addition, the geometry and tolerances of the
    connecting rods were reduced on the high revving version of the 4.2L V8 FSI engine.

    Bearing journals diameter: 54 mm
    Bearing bushings: 1.4 mm thick, 15.25 mm wide
    Length of bushing: 0.20 mm diameter rolled
    Connecting rod length: 154 mm

    Piston
    For strength reasons, forged pistons with a slightly higher weight than conventional pistons, are used. Both engines have the same piston geometry.
    Piston weight without rings: approximately 290 g (10 oz)
    Piston pin: 0.20 mm x 0.11.5 mm x 40 mm

    High-revving Engine

    * 3/8" simplex sleeve-type chains are used here. Their advantage is their reduced wear and higher stress resistance at high engine speeds. In this case the idler gears have 38 and 19 teeth. The camshaft sprockets have 25 teeth.


    Different Features of the High-revving Engine

    * To match the higher engine power output and RPM, the following cylinder head components were modified:
    * Intake ports are charge optimized (based on larger cross-sections)
    * Intake valves are chrome-plated hollow stem valves (for weight reduction)
    * Valve springs are made of a material with higher tensile strength and also have higher spring force
    * To meet the higher fuel requirements, the injectors are designed for higher flow rates.
    * Roller rocker arms are more robustly designed, with peened rollers for higher strength
    * Camshafts have different timings and larger opening lengths
    * Intake valve opening angle 230 crank angle degrees
    * Exhaust valve opening angle 220 crank angle degrees
    * The lifters were adapted from the 3.2L V6 engine found in the TT and A3. They have a larger ball stroke which, in the course of testing, proved advantageous for the high-revving engine (with regard to the inflation of the hydraulic valve clearance compensation element).
    * The cylinder head has a modified water jacket which circulates coolant to the area between the intake port and the injector, thereby reducing the temperatures in the cylinder head combustion chamber plate.
    * Due to a modified camshaft drive reduction ratio, the camshaft adjuster has 25 teeth for the chain drive, as opposed to 30 teeth in the basic engine.

    In the more highly stressed high-revving engine, an additional oil-air heat exchanger is used to minimize the oil temperature even at high engine load. This additional heat exchanger is operated in parallel with the heat exchanger via a thermostat.

    Audi RS4 Sump
    A reliable supply of oil in all driving situations is critical, especially in a sports car such as the RS4. The oil supply system in the high-revving engine was designed for racing applications in which it is subjected to lateral
    acceleration of up to 1.4 g. To ensure this, the sump in the RS4 has an additional system of flaps.

    Design
    Four flaps, whose axis of rotation is parallel to the longitudinal axis of vehicle, are arranged inside a housing. Each of the flaps opens toward the inside of the intake end of the oil pump.

    Function
    When the vehicle is cornering, the oil flows inside the sump toward the outside of the corner. The two flaps facing the outside of the corner close and hold the oil in the sump intake. At the same time, the two flaps facing the inside of the
    corner open to allow additional oil to flow into the intake. This ensures a sufficient supply of oil to the oil pump.

    The intake system of the RS4 engine was designed with emphasis on maximum flow control. Pressure loss is minimized by a large cross-sectional areas in the Mass Air Flow (MAF) Sensor G70 and air intake pipe in combination with a 90 mm diameter throttle valve.

    To ensure a sufficient supply of air to the engine at high RPM, the power flap in the air filter is opened at engine speeds higher than 5000 RPM and at road speeds higher than 200 kph.
    The power flap is opened and closed by a vacuum
    actuator which is map-controlled by the ECM via the Intake Air Switch-Over Valve N335.

    The sand cast aluminum (should be magnesium) intake manifold was designed specifically to match the sporty characteristic of the engine. In contrast to the basic engine, maximum torque is produced at higher engine RPM. At this engine speed, the intake manifold changeover valve would be switched to the short path for higher power output.

    Spark Plugs
    In contrast to the Audi Q7, spark plugs with a higher heatrating (colder plugs)* are used because the RS4 engine is subjected to higher thermal stresses.
    * applies to NGK spark plugs

    Injectors
    Due to the higher fuel demand and the shorter window of time available for injection at very high engine speeds, the RS4 engine is fitted with larger injectors than the Audi Q7 engine.
    Last edited by GotRS?; 12-18-2008 at 11:22 PM.

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    Veteran Member Four Rings JetBlue's Avatar
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    Re: S4 vs S5 engine

    Although the motors are the same basic architecture they are different blocks, bottom ends and top ends. There is nothing in common between the RS4 and S4/S5 motors. The RS4 motor has one of if not the highest piston speed of any production motor and actually rivals the piston speeds of current F1 cars. If I remember correctly it is in the neighborhood of 150 feet per second. Pretty amazing when you think about how the piston comes to a complete stop and then changes directions around 140 times per second.
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    Re: S4 vs S5 engine

    Quote Originally Posted by Swanky View Post
    The funny thing is the S5 is just as fast as the RS4 with such a "discrepancy" on paper statistics...

    here is just one source (edmunds article)
    354 hp Audi S5: 13.3 1/4 mile @ 104 mph
    420 hp Audi RS4 13.2 1/4 mile @ 106 mph
    no shot. and i love how all the s5 fanboys take such pride in this. line up a s5 and rs4, the rs4 will dust it every single time. rs4's run high 12s stock, and thats a fact. considering my car ran a 13.3 bone stock yet got pulled on by a bus length by an rs4, that edmunds test is BS

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    Re: S4 vs S5 engine

    Agreed. The one posted time from an RS4 on this forum I've seen was around a 12.8 IIRC... That mag article seems slow for the RS4 and seems like that would be at the lower end of the spectrum for typical 1/4 time for an S5. JMHO.

    How does the RS4 never get any love?? When you read something like this quote or post #12, how can you not love a production street car with an engine like that?
    Quote Originally Posted by JetBlue View Post
    Although the motors are the same basic architecture they are different blocks, bottom ends and top ends. There is nothing in common between the RS4 and S4/S5 motors. The RS4 motor has one of if not the highest piston speed of any production motor and actually rivals the piston speeds of current F1 cars. If I remember correctly it is in the neighborhood of 150 feet per second. Pretty amazing when you think about how the piston comes to a complete stop and then changes directions around 140 times per second.
    RS4 is a work of art in my opinion. If I had more money I would own one.
    Last edited by Captain Insano; 12-19-2008 at 01:27 PM.

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    Re: S4 vs S5 engine

    Quote Originally Posted by 91gl View Post
    no shot. and i love how all the s5 fanboys take such pride in this. line up a s5 and rs4, the rs4 will dust it every single time. rs4's run high 12s stock, and thats a fact. considering my car ran a 13.3 bone stock yet got pulled on by a bus length by an rs4, that edmunds test is BS
    that makes you an rs4 fanboy!!

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    Veteran Member Four Rings AudiOso's Avatar
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    Re: S4 vs S5 engine

    Say goodbye to the V8 in the S5... that stupid 3.0 S/C V6 is what's going in it as of the 2010 production run.
    A couple of Audi's later...

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    Re: S4 vs S5 engine

    I seriously have no idea why anyone would want the 4.2 over the FSI SC 3.0 other than exhaust sound. And blown 3.0s can sound pretty damn nice IMO

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    Re: S4 vs S5 engine

    I agree, that 3.0 SC engine will be cool - a pulley and tune away from a BIG jump in power most likely. Gotta love forced induction.

    However, I can't say I dislike the 4.2L V8. I think it's a pretty decent engine in S4 form, and I already posted my opinion on the RS4 4.2L V8 (work of art). I think we are going to see alot more performance mods this year and better results from the S4 & S5 4.2L V8.... Can't comment on which will be better until the 3.0L SC engine actually exists and is modded.

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    Active Member Three Rings DuncanC's Avatar
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    Re: S4 vs S5 engine

    I can't believe anybody is pumped about them taking away the 4.2 and giving us a lame SC V6. It doesn't like to rev. (no V6's do they are inherently unbalanced designs requiring crankshaft balance weights to keep from shaking to pieces) The sound won't be even close. I don't believe that big power is a pulley and a tune away, I think they are pushing 350hp out of an engine they initially designed for 250hp and its probably pretty close to its breaking point as is. If fuel economy for CAFE is that important I'd rather see a Turbo 4 like the B5 S4 had. But really to me the V8 makes the car, I would much rather have seen them add FSI to the 4.2 and at least offer it as an option. I don't really care about fuel economy and I don't care about 1/4 mile times, I don't care about 0-60. I care about a car that puts a big assed grin on my face every time I drive it, and for me only a N/A V8 does that. S/C car's have too much torque all around, anybody can drive fast in a car that has torque from 1500-5500 but it isn't fun. Turbo cars make you work them hard to get the most out of them which adds to the fun factor. But the throttle response is never going to be like it is in a N/A motor. The S cars are for people who enjoy driving and to me nothing is better to drive than a big power high reving N/A motor.

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    Re: S4 vs S5 engine

    that V8 is a cool-ass engine. much better than the S4 40 valve V8 that I have in my B7

    BUT

    don't think an S5 is anywhere near as fast as an RS4...that's just Edmonds. They SUCK BALLS at testing cars. They're really clueless.

    every reputable magazine (R&T, C&D, MT, Automobile) puts the stats as follows (or as near as makes no difference)

    0-60
    RS4 4.2-4.4
    S5 4.8-4.9

    1/4 mile
    RS4 12.8-13.0
    S5 13.3-13.5

  22. #22
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    Re: S4 vs S5 engine

    You shouldn't judge until it's available. It might be quite an engine. Or it could be tuned aggressively from the factory without much room for power improvement with simple mods. If I was a betting man I'd wager it will make an additional 40-50 bhp easy with a pulley and tune. Throw an exhaust in the equation and it's probably gonna be 400 bhp pretty easily.... We won't know until it's available and modded though.

    BTW, the B5 S4 is bi-turbo 6...

    PS - I like V8s alot too - I'm very happy so far with my B6 S4 and I don't even have an exhaust. Yet....
    Quote Originally Posted by DuncanC View Post
    I can't believe anybody is pumped about them taking away the 4.2 and giving us a lame SC V6. It doesn't like to rev. (no V6's do they are inherently unbalanced designs requiring crankshaft balance weights to keep from shaking to pieces) The sound won't be even close. I don't believe that big power is a pulley and a tune away, I think they are pushing 350hp out of an engine they initially designed for 250hp and its probably pretty close to its breaking point as is. If fuel economy for CAFE is that important I'd rather see a Turbo 4 like the B5 S4 had. But really to me the V8 makes the car, I would much rather have seen them add FSI to the 4.2 and at least offer it as an option. I don't really care about fuel economy and I don't care about 1/4 mile times, I don't care about 0-60. I care about a car that puts a big assed grin on my face every time I drive it, and for me only a N/A V8 does that. S/C car's have too much torque all around, anybody can drive fast in a car that has torque from 1500-5500 but it isn't fun. Turbo cars make you work them hard to get the most out of them which adds to the fun factor. But the throttle response is never going to be like it is in a N/A motor. The S cars are for people who enjoy driving and to me nothing is better to drive than a big power high reving N/A motor.
    Last edited by Captain Insano; 12-19-2008 at 05:41 PM.

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    Re: S4 vs S5 engine

    Quote Originally Posted by Swanky View Post
    that makes you an rs4 fanboy!!
    listen, i love both cars and all audis but the truth is the truth, the rs4 is hands down faster

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    Re: S4 vs S5 engine

    Quote Originally Posted by Swanky View Post
    The funny thing is the S5 is just as fast as the RS4 with such a "discrepancy" on paper statistics...

    here is just one source (edmunds article)
    354 hp Audi S5: 13.3 1/4 mile @ 104 mph
    420 hp Audi RS4 13.2 1/4 mile @ 106 mph
    yeah, RS4 is a consistent 13.0 at 107mph...also, keep in mind, the S5 is much lighter than the RS4.
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    Re: S4 vs S5 engine

    Quote Originally Posted by 91gl View Post
    listen, i love both cars and all audis but the truth is the truth, the rs4 is hands down faster

    Quote Originally Posted by EuroB6 View Post
    yeah, RS4 is a consistent 13.0 at 107mph...also, keep in mind, the S5 is much lighter than the RS4.

    i hear both of you... i just think it is interesting that the cars are close.

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