D2 S8 engine vs D2 A8 engine

[icrashcars]

Are there any physical differences between these two engines or does the extra 60Hp in the S8 come from the tune and exhaust?

also, if I put the S8 steering wheel with button shifters into an A8, what needs to be done to use the button shifters? I was thinking I could swap ecus perhaps?

sorry for the noob questions. I picked up an A8 in magnificent condition, but only because I could not find a reasonably priced S8 in similar condition. So the plan is now to do a conversion.

Untitled by haste1us


Untitled by haste1us


Untitled by haste1us

[Scotty@Advanced]

Are there any physical differences between these two engines or does the extra 60Hp in the S8 come from the tune and exhaust?

also, if I put the S8 steering wheel with button shifters into an A8, what needs to be done to use the button shifters? I was thinking I could swap ecus perhaps?

sorry for the noob questions. I picked up an A8 in magnificent condition, but only because I could not find a reasonably priced S8 in similar condition. So the plan is now to do a conversion.

S8 Rods are forged versus powdered metal on the A8.
S8 intake differs
Cams differ
Tuning differs
Exhaust manifolds differ IIRC

Wait for an S8 to crop up, the additional money you will spend on converting an A8 to S8 will buy you an S8.

[icrashcars]

thanks. I scored a mint a8 with 90k for $4k, so i couldnt pass it up. My buddy's shop just did the timing belt service, all hoses, wires, rollers, seals, motor mounts..etc so im pretty committed to this car.

The plans are to build the motor with performance internals in the spring, until then I am sourcing the body parts. I dont want an S8 clone...just an A8 on steroids. However, I would really like the steering wheel shifting abilities...so I am going to swap one in and go from there. I know there are flashes to change the shift mode to more of a sportier mode, so perhaps an ECU flash would enable the shifting abilities?

so far, finding information on the D2 A8/S8 has been challenging...but this site has been the best resource.

[BASARAB]

I barely see any info about modding d2 or d3.

[icrashcars]

Well, found a great DIY on retrofitting an S8 steering wheel into the A8....
http://www.audipages.com/upgrades/tiptronicwheel.html

[Nollywood]

Are there any physical differences between these two engines or does the extra 60Hp in the S8 come from the tune and exhaust?

More than just a tune and exhaust. Your A8 is a 32V. The equivalent 32V S8 was not sold in the United States, and was 40 hp up on the regular A8. The 40V version was 60 hp more than your 300, and 50 hp more than the 310 offered by the A8 40V.

Audi S8 32V.

01) Solid exhaust tappets.
02) Different camshaft profiles.
03) Different ECU.
04) Different pistons (higher CR).
05) Larger intake plenum.
06) Larger throttle body.
07) Larger exhaust manifolds.
08) Larger exhaust ports (different cylinder heads).
09) Different catalysts.
10) Different injectors.
11) Different transmission (lower final drive).
12) Different rear differential (lower final drive).
13) Different MAF.
14) Different airbox.

Audi S8 40V.

01) Different camshaft profiles.
02) Different ECU.
03) Different pistons (higher CR).
04) Larger intake plenum.
05) Larger throttle body.
06) Larger exhaust manifolds.
07) Larger exhaust ports (different cylinder heads).
08) Different catalysts.
09) Different injectors.
10) Different transmission (lower final drive).
11) Different rear differential (lower final drive).
12) Different MAF.
13) Different airbox.

All S8 engines rev higher than the equivalent A8's, hence the lower final drive to make the best of the engine's peaky nature. They're redlined at 7,000 rpm versus the A8's 6,400. It'll take more than a tune and exhaust to boost your 300 hp to 340, never mind 360 hp. Not without some form of forced induction. To attain those numbers whilst keeping the engine naturally aspirated, you're talking big bucks - tubular headers, cat delete, lumpy cams, throttle bodies, custom tune. I wouldn't fancy running an A8 engine at 7,000 rpm with your hydraulic tappets long term.

[Scotty@Advanced]

Also the crank pulley power steering pulley and serp belt are different, the S8's 7000 rpm rev limiter requires slower accessory speed.

[Scotty@Advanced]

Audi S8 40V.

01) Different camshaft profiles.
02) Different ECU.
03) Different pistons (higher CR).
04) Larger intake plenum.
05) Larger throttle body.
06) Larger exhaust manifolds.
07) Larger exhaust ports (different cylinder heads).
08) Different catalysts.
09) Different injectors.
10) Different transmission (lower final drive).
11) Different rear differential (lower final drive).
12) Different MAF.
13) Different airbox.

This is not correct.

The following components are the same from the A8 to S8

Throttle body
Cylinder head castings
Pistons ** Same as the A6/S8/S6

The only internal engine difference from the A8 to S8 is the rods, the S8 uses forged rods versus powdered metal rods for the A8.

Also i failed to mention the A8-S8 valve train is different with higher ratio rockers and diff cam profiles. Valves/springs are the same.

[icrashcars]

Serious differences. Thanks for the great information.

[Nollywood]

This is not correct.

The following components are the same from the A8 to S8

Throttle body
Cylinder head castings
Pistons ** Same as the A6/S8/S6

The only internal engine difference from the A8 to S8 is the rods, the S8 uses forged rods versus powdered metal rods for the A8.

Also i failed to mention the A8-S8 valve train is different with higher ratio rockers and diff cam profiles. Valves/springs are the same.

Sorry Scott, I disagree.

I'm not 100% on the TB and cylinder heads. I have seen different part numbers on the AHC and ABZ cylinder heads. They can't be the same, as the AHC (S8) runs solid exhaust tappets. I've owned a '96 A8 4,2 QS and a '98 S8 - both pre-facelift models. And all the parts I mentioned above ARE different.

You reckon the rods are the only internal differences? The pistons are the same? Then what gives the S8 the higher 11,0:1 CR over the A8's 10,5:1? Because regardless of the material the rods are made of, the dimensions remain the same. The only other components that could alter the CR are the crankshaft and / or combustion chambers in the cylinder heads.

[TozoM8]

The original poster is from New Jersey so the pre-facelift S8 is out of the question. The US S8 01'-03' is a 40V engine with two stage intake and variable intake valve timing.

[Nollywood]

The original poster is from New Jersey so the pre-facelift S8 is out of the question. The US S8 01'-03' is a 40V engine with two stage intake and variable intake valve timing.

That's true bruh. I only mentioned the pre-facelift, to make more of a direct comparison between his 32V and the 32V S8. But you're very correct.

[Scotty@Advanced]

Sorry Scott, I disagree.

I'm not 100% on the TB and cylinder heads. I have seen different part numbers on the AHC and ABZ cylinder heads. They can't be the same, as the AHC (S8) runs solid exhaust tappets. I've owned a '96 A8 4,2 QS and a '98 S8 - both pre-facelift models. And all the parts I mentioned above ARE different.

You reckon the rods are the only internal differences? The pistons are the same? Then what gives the S8 the higher 11,0:1 CR over the A8's 10,5:1? Because regardless of the material the rods are made of, the dimensions remain the same. The only other components that could alter the CR are the crankshaft and / or combustion chambers in the cylinder heads.

I was talking about the 40V engines, not the 32V. The OP also mentioned the S8 having 60 extra hp meaning he's talking about a 40V S8 engine and I'm assuming he's comparing it to a 40V A8. The USA never got the 32V S8 engine.

[Nollywood]

I was talking about the 40V engines, not the 32V. The OP also mentioned the S8 having 60 extra hp meaning he's talking about a 40V S8 engine and I'm assuming he's comparing it to a 40V A8. The USA never got the 32V S8 engine.

I understand.

I posted details on both 32 and 40V S8's for comparison. The S8 40V motor still has quite a lot of differences over the equivalent 40V A8, both internal and external.

Out of interest, were the pre-facelift A8's in the US fitted with the 32 or 40V engines? I only ask, as in Europe, the 40V engines occured during the facelift. And the OP's car is a pre-facelift, making an upgrade to S8 power / spec even more complex.

[OLMEC]

Nice score...

[audinutt]

It appears that his a8 is a prefacelift judging by the pics.
The 32v v8 makes 300hp as I recall.
The 40v a8 engine in the facelift makes 310hp.

And the s8 engine make 360hp.
These are US car specs.

Back to the original poster's questions, your engine is VERY different from the s8's.

-richard

[Klum00]

your A8 is a great car as it is. I say do what you want with it cosmetically and be happy! It's still a quick D segment luxury sedan. Keep it for a while and once the same kind of deal comes up for an S8, trade up.

[TozoM8]

If you want more performance out of your A8, put an S8 trans and rear diff in it. It will be almost as quick as the S8.

[audinutt]

Speaking of which gabor, do you have another s8 rear end?

[icrashcars]

Well, I am in the market for totaled S8. any ideas where to buy one complete?

[Scotty@Advanced]

Well, I am in the market for totaled S8. any ideas where to buy one complete?

Many of the auction houses have them from time to time but you have to be registered and have the appropriate licenses.

[TozoM8]

Speaking of which gabor, do you have another s8 rear end?

No, I don't.

[audinutt]

Well, I am in the market for totaled S8. any ideas where to buy one complete?

Just keep in mind that the s8 has a lot of changes with the facelift. Immobilizer is going to be a big issue, if you don't mind tearing apart your a8 to rewire it go for it, it will be a pain.

[Nollywood]

Personally, I see converting an A8 to an S8 as reinventing the wheel. It's not like the S8 is a rare model. Now if you were converting a B5 A4/S4 to RS4, it would make more sense, seeing as the B5 RS4 was not officially imported to the United States.

If you simply wish to increase your accelleration times, then S8's lower gearing will make your 0-60 dash closer to the S8. The A8 and S8 are externally identical, so it's not like you're trying to achieve the same look. An S8 power train conversion will be costly, more so seeing as your car is a pre-facelift. Facelift has the immobilzer built into the cluster, and the facelift cluster won't plug into your car, without a lot of rewiring. It'll probably be much easier to obtain a Euro-spec pre-facelift S8 engine (AHC / AKH) as it shares a lot in common with your own car. Same wiring harness, and the immobilizer is stand alone (little box under steering column). You'll gain 40 hp, but will still still be trailing a regular A8 with the S8's lower-geared trans and rear diff.

[TozoM8]

I have a pre-facelift S8 cluster with 24513 miles for sale.
http://audipages.com/tozo/IMAG0200.jpg

[HIstateS8]

Well, I am in the market for totaled S8. any ideas where to buy one complete?

Try look up Shokan coachwerks. They have a whole bunch of A8/S8 parts. Good luck

[Scotty@Advanced]

Try look up Shokan coachwerks. They have a whole bunch of A8/S8 parts. Good luck

I wounldn't even consider Shokan as an option, their pricing is way out there.

[icrashcars]

I wounldn't even consider Shokan as an option, their pricing is way out there.

they had a decent price on body parts...650 for the front bumper and spoiler...350 for both mirrors. lights were expensive, so ill probably import those.

Since the engine is running beautifully, I am focusing on the suspension, body aesthetics, and having the exhaust overhauled.

updates and pics to come soon.

[TozoM8]

I have a pair of S8 mirrors for sale.

[icrashcars]

So, I drove up to my ski house on friday night, then on Saturday morning my "check battery" light came on. I let it idle thinking the battery would charge, but it did not. eventually it just puttered out, so I am assuming the alternator is not working properly.

I just had all the belts replaced two weeks ago, is it possible that something is just loose? Seems strange that it would just die without any symptoms.

any suggestions or advice?

[Nollywood]

If the drive belts are in place, then I doubt your battery warning would be as a result of the recent replacement. The serpentine belt tensioner is spring-loaded, so it's not possible for the belt to be too slack, unless the replacement is much longer than the original.

I would suggest you get your battery charged externally, then start the car. You can then check alternator output. Anything less than 14,0 volts with the engine idling, and all consummables switched off would indicate a tired alternator. I would expect to see 14,4 volts at idle.

[icrashcars]

If the drive belts are in place, then I doubt your battery warning would be as a result of the recent replacement. The serpentine belt tensioner is spring-loaded, so it's not possible for the belt to be too slack, unless the replacement is much longer than the original.

I would suggest you get your battery charged externally, then start the car. You can then check alternator output. Anything less than 14,0 volts with the engine idling, and all consummables switched off would indicate a tired alternator. I would expect to see 14,4 volts at idle.

If the alternator isnt the culprit, shouldnt it have atleast idled after the battery went dead?

[icrashcars]

I have a pair of S8 mirrors for sale.

What are you looking to get for the mirrors? Do you have a front S8 bumper by chance?

[TozoM8]

$250 + shipping for the pair.