nakata

What are the exact differences in the engines? What are the exact values ​​of camshaft? Other major differences are there in the exhaust, intake? Are same MAF sensor?
Think about to put in my A8, S8 camshaft and injector and reflash ecu. What result to expect?

nakata

Talk about 5V engine's.

omarcarbomb

Higher Compression- Not exactly an easy mod...

nakata

When watch ELSA, C/R is same for A8 & S8 11:1. Only know about conrod's is differend.

ddillenger

v8a6 on AZ has s6 heads on his a6.

To start, the cams are more agressive, the s6/s8 heads have an additional roller for the timing belt, exhaust manifolds, and the biggest difference, the variable intake manifold. The a6/8 has a 3 stage manifold, with variable runner changeovers around 3000rpm and 4500rpm, whereas the s8 manifold only undergoes one state change. The a6/8 has dual solenoids to activate the manifold runners independent of one another, whereas the s6/8 only requires one solenoid as both runners open simultaneously.

omarcarbomb

http://en.wikipedia.org/wiki/Audi_A8#S8

"A retuned, 20-millimetre (0.8 in) lowered sports suspension included a 30 percent stiffer spring rate and 40 percent more compression damping in the shock absorbers. Speed-sensitive "servotronic" power assisted steering was also standard."

there is your more compression

Here is the best mod....

Trade your a8 in on an S8!

silverd2

The easiest way to match an A8 to an S8, is to pour a few gallons of fuel directly into the nearest storm drain each time you fill the tank

Actually the single thing that makes an S8 faster than an A8 is NOT the engine...it's the same thing that makes an S8 suck fuel like a tractor trailer: The Gearing. The actual trans is identical in A8 and S8, but all 3 differentials (2 in the transaxle case & the rear end) are geared lower in the S8. Those who have switched transaxles and matching S8 rear end gearing have achieved very close to the same acceleration times in an otherwise stock A8. ...and DOWN go the mpg's. S8 owners will notice that at highway speeds in top gear, they are taching about 700 rpm's higher than an A8. My A8 winds to about 81 mph at 6400 rpms in 2nd gear, while an S8 hits only 66 mph at 7000 rpms in 2nd gear.

The engine is only subtly tuned, mainly to reach the higher rev limit:

- Compression the same...block, pistons, lifters & valves the same.

- Same exhaust system ( manifold and all) w/chrome tips on S8.

- Slightly more aggressive cams and valve springs.

- Slightly higher peak flow injectors.

- 2 stage intake manifold in S8...one shift at about 5400 rpms.
3 stage in A8 (more expensive part)...shifts at 3360, then 5200 rpm's.

- S8 has different ECM, TCM and MAF.

- The extra idler roller on S8 engine is a "safety" ( not vitally needed) timing belt stabilizer for higher red line.

- 20mm lower and firmer suspension w/larger diameter rear sway bar. Aftermarket A8 suspensions (MUCH cheaper) are tighter and lower than OEM S8.

I, for one, consciously chose the A8 SWB as my #1 choice for what it is...an S8 would have been about #25 on my list. I still would not trade even at the same mileage, unless it was money motivated quick-flip deal to get a newer A8. If performance was the top priority, I certainly wouldn't be basing it on a 2 ton, upright 4 door sedan...I'd be switching back to Porsche.

To each their own...but, there are many of us who have NEVER wanted an S8 and did NOT compromise with an A8. The A8 is beautifully balanced and unique sport/luxury German sedan just the way it is and a MUCH better traveling car than an S8 in all ways.

nakata

I'm cared about suspension, know about engine only please. Some one to know exactly what is the different diameter in exhaust?

silverd2

Identical.

nakata

Well, thank you for answer.
My A8 is 6800 rev and manual transmission. But found very cheaply S8 camshaft&injector and temptation to upgrade engine.
Why S8 have only one stage intake? About MAF different is only diameter of tube or anything else?