A8 vs S8 engine
AudiWorld Super User
Joined: May 2010
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From: East TN
MAF's are all electronically matched to specific engine codes and ECM's.
AudiWorld Super User
Joined: May 2010
Posts: 2,611
Likes: 11
From: East TN
The S8 goes through each gear so much faster than an A8, due to gearing, that 3 stages are not practical and do not match the torque curve produced by the S8 engine.
AudiWorld Member
Joined: Aug 2011
Posts: 322
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From: Houston
compression is already there.. &,
I'm guessing that running higher octane fuel would get the cheapest & easiest improvement.
The 93 octane with whatever % of alcohol does not exactly equate to max performance for the 4.2.
98 octane without alcohol should be the ticket which is a bunch easier than making engine mod's.
Then again the last time I picked up 5 gals of C16 it made me glad I only go to the strip on a limited
basis. Having fun has gotten to the point of not being (much) fun at all.
The 93 octane with whatever % of alcohol does not exactly equate to max performance for the 4.2.
98 octane without alcohol should be the ticket which is a bunch easier than making engine mod's.
Then again the last time I picked up 5 gals of C16 it made me glad I only go to the strip on a limited
basis. Having fun has gotten to the point of not being (much) fun at all.
Audiworld Junior Member
Joined: Jul 2012
Posts: 66
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From: Lithuania, Vilnius
Ive had both A8 and now have S8. Travelling wise, A8 is better. Smoother, better mpg. S8 looks better, inside and outside. Better brakes, not overheating like in A8. I like peformance, sound. But little bumpy ride and much worse fuel consumption is not so nice. But...handles nicely.
AudiWorld Super User
Joined: May 2010
Posts: 2,611
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From: East TN
Hard info to find...but doesn't include stock AUX or AKB (40V D2 A8) engines, though.
It also doesn't specify if the 40V S8 timing specs are at the retarded or advanced setting.
40V engines have variable valve timing which only advances and retards the intake cams about 10 or 12 degrees(?)...also tough to find specific info on just how much advance.
So here's all I've found:
Stock S8 (AYS)
Intake Lift at cam = .410" = 10.41mm
Exhaust Lift at cam = .310" = 7.87mm
AYS Camshafts (S8 V8 4.2 40v)
Intake open after TDC 25º
Intake close after BDC 45º
Exhaust open before BDC 38º
Exhaust close before TDC 8º
AEW Camshafts (V8 3.7 32v)
Intake open after TDC 10º
Intake close after BDC 25º
Exhaust open before BDC 30º
Exhaust close before TDC 10º
ABZ Camshafts (V8 4.2 32v)
Intake open after TDC 10º
Intake close after BDC 40º
Exhaust open before BDC 30.5º
Exhaust close before TDC 2º
It also doesn't specify if the 40V S8 timing specs are at the retarded or advanced setting.
40V engines have variable valve timing which only advances and retards the intake cams about 10 or 12 degrees(?)...also tough to find specific info on just how much advance.
So here's all I've found:
Stock S8 (AYS)
Intake Lift at cam = .410" = 10.41mm
Exhaust Lift at cam = .310" = 7.87mm
AYS Camshafts (S8 V8 4.2 40v)
Intake open after TDC 25º
Intake close after BDC 45º
Exhaust open before BDC 38º
Exhaust close before TDC 8º
AEW Camshafts (V8 3.7 32v)
Intake open after TDC 10º
Intake close after BDC 25º
Exhaust open before BDC 30º
Exhaust close before TDC 10º
ABZ Camshafts (V8 4.2 32v)
Intake open after TDC 10º
Intake close after BDC 40º
Exhaust open before BDC 30.5º
Exhaust close before TDC 2º
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Joined: Feb 2016
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I am checking to see if JH Motorsports knows anything - if anyone can do it, they can.
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