Audi S2 RSR

[UrS4boy]

Seems weird that 9.0:1 is mentioned since the MTM site says 9.3:1. These days that is low anyway.

9.3:1 is low (now) for naturally aspirated but not for turbo or supercharged.

[Mcstiff]

9.3:1 is low (now) for naturally aspirated but not for turbo or supercharged.

Perhaps for a stock car where you need to account for people dumping low OCT fuel in.

With modern technology tuners/racers, we are talking about a tuner car, can now enjoy the benefits of high compression ratio forced induction.

My old 7at had nearly 100,000 miles running 10 psi with stock compression and no intercooling.


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[A80Avant]

not to mention all new audi turbocharged engines and compressions much higher than I5.

[Billman]

None of these engines run 2 bars of boost on 98 ron and they also have much better knock control (ignition retard when it detonates).
They also have direct fuel injection witch speeds up the burn procces thus reducing the chance of knock, thezy have better combustion chamber design. All these features make these engines more capable to run higher compression.

[A80Avant]

we will soon see!

a lot of new tfsi/tsi and 1.8T engines on big turbos run big boost and hp. their CR is higher than 9:1

as a reference:
1.8T engine: 9.3:1 OEM head gasket
1.4TFSI/ S3 20.TFSI: 10:1
20.TFSI A4: 9.6:1

most of these that run maps, they take the boost at high levels, and do not knock.

Of course cyl head technology and fuel delivery plays a role, but it can be done and be efficient.

[Jamo]

Technology has moved on see turbo cars running 10:1 cr but billman is correct once modded a lot have to drop cr

[Billman]

we are highjacking the thread again but 9.3:1 is not much different than 9:1.
The guys running big turbos and big boost run also compression reducing gaskets. Except they run E85 or more exotic fuel.

[Jamo]

I think IMO its more the article isn't strictly accurate Regarding the cr
Bit like the dialynx article

[Sleeper_Avant]

well...................
back in 1992 the Escort WRC car ran 9.6:1 and undisclosed boost and produced (34mm restrictor) 300bhp *obviousley LOL* but more importantly 640nm torque!!!!
last of the line WRC cars behind hidden doors had CR 10:1CR and 40psi on a 34mm restrictor, remove the restrictor and remap....... instant 560cast iron horses with 720nm or mental gearbox f ucking torque.
you need to go out in one

ive always upped my CR on cosworth motors from 8.2 to 8.8:1 and minimum of 32psi purely for massive torque.


Displacement : 2979 cm3
Bore x Stroke : 84.0 x 89.6 mm
Type : 24 Valves
Aspiration : Bi-Turbo + Intercooler
Compression Ratio : 10.2
Output : 306 cv (225 kW) @ 5800 rpm
Torque : 400 Nm (295 lb.ft) @ 1300 - 5000 rpm



BMW 335i twin turbo,
we were the first people in the uk (europe maby?!) to fit a pair of hybrid turbos to this engine, and apart from uprated fuel pressure (commonrail high pressure type) and live mapping we whacked WELL over 500bhp from a standard motor but backed it off cos of the gearbox and diff complaining, this car has ran 460bhp at the hubs for 2 years now with no problems whatsoever........................................ ...

***also enlarged intercooler***

2.1bar of boost held from 2100rpm to limmiter

i had to fit the turbos 3 times, turbo dynamics ****ed the wastegate adjustments up and they rattled on tickover, not a nice job!

conclucion, technology is coming on in leaps and bounds and compression is a major factor, even more so with direct injection ****** petrols

pm me for more specs on what ive said

Sean

[Jamo]

Not doubting the method we are confused by the statement they upped compression on a 3b engine to 9.3 when the 3b is 9.3 stock
Maybe they took it to 9.5 but I think it's an article error for the true figure is lost in time

[Sleeper_Avant]

i see,

i dont know much about S2`s and tuner specials like the MTM cars etc

but if they used standard internals and only headgasket changes then surely thinner gaskets would cause valve/piston interfearance if standard valvetrain were employed? i.e standard spring rates, thinner gaskets and standard pistons?

RWD19T and me had very in depth chat when he bought my 2.5 bottom end and this was also discussed.

i know Early tuners messed about with CR`s using different layers in the metal headgaskets, inc Doug@MRC but im sure this was mainly to lower the CR.

interested to see the outcomes of this as im looking to build a high CR motor over the winter for my A4.

Sean.

[Sleeper_Avant]

cant edit my post?!

So extra reply, sorry!

is it possibly whoever wrote the article got confused between the old MB/RR to new 3b specs?

havent read article but mearly throwing ideas to explain things?

[Error404]

Doubt it journalists are infallible

[Jamo]

i see,

i dont know much about S2`s and tuner specials like the MTM cars etc

but if they used standard internals and only headgasket changes then surely thinner gaskets would cause valve/piston interfearance if standard valvetrain were employed? i.e standard spring rates, thinner gaskets and standard pistons?

RWD19T and me had very in depth chat when he bought my 2.5 bottom end and this was also discussed.

i know Early tuners messed about with CR`s using different layers in the metal headgaskets, inc Doug@MRC but im sure this was mainly to lower the CR.

interested to see the outcomes of this as im looking to build a high CR motor over the winter for my A4.

Sean.

Well no that's the whole point the orignal 3b engine had the paper gasket which gave a 9.3 compression later 93/94 ABY / AAN / ADU cars with the thicker metal one went to 9.0.

[Sleeper_Avant]

i see but surely the motorsport cars ran metal gaskets?

swopping layers is common place on metal gaskets to achive different CR`s,

these have been available technology wise from the very late eighties and early ninetys.

with MTM`s finding in R&D they had availability to the technology and research in motorsport backing?

Ford Cosworth powered road cars all ran paper Reinz gaskets but WRC stuff ran multi layer metal gaskets in `92, technology was widely available and used at the time, im sure i saw pictures of the early development 25v heads that ran metal multilayer gaskets.

not pushing an argument, mearly voicing suggestions.