S4 Heads vs RS4 heads

[saf]

What are the differences between RS4 hears and S4 heads?

Ive had this explained before but still un clear.

When upgrading an S4 to stage3 K04 turbos with all RS4 bits IC's clutch flywheel injectors etc, and also heads are changed to RS4 heards, does that make car mechanically identical to an RS4 or are there other differences?

What are advantages and disadvantages between using S4 heads and RS4 heads on the S4.

Ive been told RS4's , turbos kick in at 3000 rpm and S4's at 2000 rpm because of the size of holes on the heads. This give you more low end grunt. Meaning?


Also more low down torque on an S4 because of smaller holes on the heads. Does this mean its better to have S4 heads if youre not going on track. If youre not going up to the high end of the speedo, is it better to stick to S4 heads?

Im thinking of doing an upgrade soon and want to know what heads to look out for.

Any advice would be much appreciated.

Many thanks

[s4woody]

2.4 heads from an A6 would do you fine..with some RS4 valves cos there filled with gas and stay cooler..just to confuse you even more...

[searider]

2.4 heads from an A6 would do you fine..with some RS4 valves cos there filled with gas and stay cooler..just to confuse you even more...

Gas?

How does that work?

I've heard of sodium filled valves - same thing?

[KayGee]

S4 and RS4 valves are the same. Exhaust cams are diff, Intake cams and valves are the same, only dfif. is exhaust cams and springs. From ettka.

S4 and RS4 are boh sodium fillled.

Rgds

Kaygee

[Paulm]

I would say this is all far to complicated. Cosworth (tuned the RS4) worked out the best compromise between Velosity and Volume.

Very Very basic.

Small ports S4. High velosity quick spool up = high low down torque

Larger ports RS4. High volume slower spool up = less low down torque but much more flow top end.

Cosworth prob spent thousands and thousands working out the best compromise.

If it were me I would go for the RS4 head and cam set up.

[s4woody]

you sure about them both being sodium filled..i thought only the ex valves on the RS4 were sodium filled..anyway sodium filled on a 2.4 head with RS4 cams must be the way to go..

[saf]

When changing to RS4 heads with all other bits, likeIC's fuel pumps etc, Does that mean the car is basically an RS4. If not what differences are there?

Also When you get higher flow top end, you talking about quicker and smoother accelleration higher up rev range right?

What would be better for road use?

Also another thing im trying to get my head around, is when the S4 has higher low down torque, why does it have a slower 0-60 time than the RS4?

My answer to this is probably because the RS4 has uprated injectors, K04;s and better cooled.

So what happens if we leave the S4 heads on, and then add K04's and all other RS4 bits, like IC's clutch, flywheel, injectors fuel pumps etc with remap.

Will the S4 have a better 0-60 time simply because it has smaller heads?

What are differences between S4 and RS4 apart from aux parts IC's clutch turbos etc. What are the main engine block differences.

Thanks for answering the many questions so far.

[KayGee]

Yes, both S4 and RS4 are using the same valves. However heads and exhaust cams are different.

Personally I'd go with 2.4. 2.6 or 2.8 NA heads (port matched to the RS IM and RS4 TB)

Good for very close to 600Bhp depending on turbo of choice

Much cheaper than MTM price for 605 BHp.

[saf]

Thanks Kevin,

Still confused on the head size and advantages and disadvantages of them.

The smaller heads. 2.4 2.6 and 2.8, what will be difference with these heads. Also What does NA mean and RS IM and RS$ TB.

Cheers mate

[Renarl]

Thanks Kevin,

Still confused on the head size and advantages and disadvantages of them.

The smaller heads. 2.4 2.6 and 2.8, what will be difference with these heads. Also What does NA mean and RS IM and RS$ TB.

Cheers mate

NA=naturally aspirated
TB= throttle body
IM= intake mani

Since i am upgrading my ride, reading Kaygees comment, it seems i should cancel my RS4 heads order and get a 2.8 head instead?

[SimonS4MTM]

Bottom end is different on RS4!

[dummi]

Bottom end is different on RS4!

i thought we cleared this up

[Paulm]

Yes, both S4 and RS4 are using the same valves. However heads and exhaust cams are different.

Personally I'd go with 2.4. 2.6 or 2.8 NA heads (port matched to the RS IM and RS4 TB)

Dont take this the wrong way I am not having a go.

But when Cosworth were tasked with mods for the RS4 if the N/A heads are much better than S4 ones why did they not just slap them on and save a heap of cash? Or maybe they did

I know there is far more work that goes into N/A heads to make a good overall power delivery. Optimising flow, atomisation, tumble etc. Where as you could chuck just about any head onto a turbo engine and it would make good power (Very loosely speaking)

[saf]

Bottom end is different on RS4!

in what way?

[SimonS4MTM]

Strengthened

http://data.rs246.com/Downloads/AudiRS4 ... 0Guide.pdf