NA motor builds?

[RS6BRIT]

What do you guys mean by de flap? Do you mean removing the flap in the airbox?

No mate. They mean removing the tumble/swirl flaps there actually in the manifold. Usually done whilst the manifold is off the car during a carbon clean.

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Btw - there is no such thing as 'adequate backpressure'. You want none - this myth comes from people fitting massive headers and seeing a drop in power and putting it down to backpressure being needed. Nothing like that at all - bigger headers reduce gas velocity which have a massive effect on drawing in fresh air and volumetric efficiency. You want headers no bigger than what provides zero resistance at the rpm you are looking at. Anything bigger will reduce power.
For forced induction its a different story - bigger is better.

Also you don't want to build an optimised n/a engine then slap on f/i.
Completely different tuning - for example, in n/a you want a massive valve overlap to allow the exhaust gas to help pull more air in. With forced induction if you do this all that happens is boosted air gets sent straight into the exhaust.
Similarly with rpm - with n/a you really need as many revs as you can get (hence lighter components) but with f/I this suffers massive diminishing returns. Consider the current superchargers - due to the 8k rpm limit of the rs4 they are pretty much at their rotational design limit with the pulley they have. Reducing the Rev limit could make benefits over the whole rev range but then who wants a 7 k v8;)

[sar]

if i was you i wouldnt try to reinvent the wheel.

like others have said in N/A form the max you will get out of a rs4 engine is approx 450bhp. you being in the states the ONLY option for you is JHM, fit their 2.75" x-pipe catless exhaust, get their tune tune job done. if you want to push the boat out get their lightweight crank pulley and a lightweight flywheel.

to spend any more looking for gains in N/A form is a complete waste of $$$. new cams, head work ect and the associated r&d that comes with being the 'first' will cost you tens of thousands of $$$ and your car will be off the road for months for very little gain. let the tuning company's do the r&d.

the only tuning company building rs4 engines is JHM (sleeved block,rods and a piston and ring pack deigned for boost) and from what i know they are only doing that so they can push past the 10psi boost limit they see as being 'safe' for the stock rs4 piston/ring design.

if you must have more than 450bhp the ONLY option is to supercharge. again you being in the states the answer is easy.

[rwilsonrs4]

Btw - there is no such thing as 'adequate backpressure'. You want none - this myth comes from people fitting massive headers and seeing a drop in power and putting it down to backpressure being needed. Nothing like that at all - bigger headers reduce gas velocity which have a massive effect on drawing in fresh air and volumetric efficiency. You want headers no bigger than what provides zero resistance at the rpm you are looking at. Anything bigger will reduce power.
For forced induction its a different story - bigger is better.

Also you don't want to build an optimised n/a engine then slap on f/i.
Completely different tuning - for example, in n/a you want a massive valve overlap to allow the exhaust gas to help pull more air in. With forced induction if you do this all that happens is boosted air gets sent straight into the exhaust.
Similarly with rpm - with n/a you really need as many revs as you can get (hence lighter components) but with f/I this suffers massive diminishing returns. Consider the current superchargers - due to the 8k rpm limit of the rs4 they are pretty much at their rotational design limit with the pulley they have. Reducing the Rev limit could make benefits over the whole rev range but then who wants a 7 k v8;)

You may be right in that due to high rpms of the RS4 the superchargers are losing efficiency but i can assure you that in no way are they a 7k v8 once fitted !!, mine bounces off the limiter in every gear no bother without struggling , and is still producing much more torque at 8k than it was when NA so efficiency is lost in the suoercharger not so much in the engine ,Parasitic losses an issue aswell but the gains outweigh the loss by a lot or theres no point

[Tubby]

If one were to de-flap with a port and polish you wouldn't see much gains on an N/A motor? Are the people raving about this mod mainly doing it for FI benefits? What about these intake mani spacers I hear about? One would think that when doing all these little mods that the power gains could stack up and give a noticeable increase. Partnered with stiffer differential and motor mounts on top of the lightened flywheel.

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Sorry - I think you've got me at crossed wires!
In order to keep the lush 8.5k rpm limit the pulley size is somewhat a limiting factor as most superchargers will be spinning at or near their design limit.
If you were going for out and out power at all costs then you may (and I've not tested so it's purely conjecture) aim to reduce the rpm limit when fitting a supercharger and fit a smaller pulley so the supercharger is spinning faster but the engine errr isn't so you end up with a higher boost (which may or may not give more bang).

[RIV]

How interesting!!

[rwilsonrs4]

Sorry - I think you've got me at crossed wires!
In order to keep the lush 8.5k rpm limit the pulley size is somewhat a limiting factor as most superchargers will be spinning at or near their design limit.
If you were going for out and out power at all costs then you may (and I've not tested so it's purely conjecture) aim to reduce the rpm limit when fitting a supercharger and fit a smaller pulley so the supercharger is spinning faster but the engine errr isn't so you end up with a higher boost (which may or may not give more bang).

Ok I see where your at , i would just overspeed the blower its not a problem with centrifugal blowers they will run up to 150 00 rpm , but it is a problem with rootes type and even screw blowers , you could do a smaller pulley and lower RPM but thats a real hassle i think as you would lose power in total as the rpm is limited ,so the amswer to that is to run a larger pulley ,=less boost =less power but a wider power band which would reduce the overall loss of total HP as the engine will run to its native 8k+
not worth it
overspeeding a blower isnt really a huge deal unless its by 30% or more and it would be for a very limited time unless your trying to reach the top speed for a few miles , even then it wouldnt probably do any harm , the issue is that because the tolerances in rootes blowers are so tight ,at high overspeed the lobes will expand due to the forces and heat and can make contact which will cause wear and at worst jam and cause the belt to slip /snap so yeah its not really worth the risk overspeeding , mine has the safest pulley size for this engine and is at its max design speed at 8300 engine prm but is on the downhill spiral of efficiency after 6000/ 6500, so true the ultimate power and torque cannot be produced , but it still pulls like a train

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Be interesting to see what would happen if you sized the pulley to max out at 7k rpm. No idea if better or worse but fun to try
Theory would be that it'd be spinning the charger 18% faster at all rpm up to 7000 and for ultimate performance you're looking to maximise the area under the engine output graph.

I remember talking to Doug when mrc were putting the kit together. They'd already done the b7 s4 with no problems but with the higher rpm, compression ration and massive valve overlaps all hurting forced induction gains he certainly had his hands full!

There is something about a tuned n/a engine - they have a lot of personality I would love to tinker with the b7 unit some more and see if can get up to 500