Engine swap ops

[phoenixv6quattro]

Hello Gents. Simply put, whats the simplest option to drop into my 1998 2.8 30v avant. An S4/RS4 lump or a V8 from an S8? Thinking about biting the bank manager and doing it. Looking for a decent outfit (not deltavag! Lol) to do it for me also. Any reccomendations would be A1.

Cheers

Ollie

 

[ian52]

S4 engine would be easy if you have a donor car. To do it right you will need a lot of bits.

 

[CraigG]

i would say S4 engine... but you wouldnt want to stick a stock engine in there, youd want KO4's etc aswell, which would cost a pretty penny on top of your labour costs.

but then there is that V8 burble.... hrm

 

[andybnwc]

VR6

 

[jcb]

unless your car is already shod with top notch brakes, wheels/tyres, suspension an whatever interior you like then the cost is generally going to be significantly more than picking up a decent tuned/specc'd S4.

but if that is what you want then turbo V8 every time!

 

[ado66]

The obvious answer is to stick a 2.5 TDi lump in it. One of the mods on here has a 2.5 diesel sleeper that kills S4's and still does 40mpg when thrashed, it's a no brainer.

 

[Blue_Thunder]

One of the mods on here has a 2.5 diesel sleeper that kills S4's and still does 40mpg when thrashed, it's a no brainer.

A 2.5TDI kills an S4 in what? A caravan towing race?

Have to say, an engine swap sounds like a daft idea unless everything else has been modified to suit the extra power, but then insurance will be a nightmare because the car will be so far from standard. My modified S4 costs far more to insure than a stock RS4 would be, reason being because it's modified.

But seeing as how the 2.8 and 2.7T are the same block, I would imagine physical fitment would be fairly straight forwards. It would be all the electronic faffing around that would cost you the money.

 

[aragorn]

While i dont doubt a 2.5TDI can be tuned up, your not going to get close to even a remapped S4 without spending a LOT of money, never mind a k04+ one.

All the electronics will more or less plug streight in i would imagine.

If your current car has cable throttle you'll have a bit of tweaking in the cabin to do though for the S4's electronic throttle.

Depends how much power your after as to which route i'd take. The 1.8T shouldnt be overlooked if your looking for upto around 350hp, and the lighter weight will help the cars handling without doubt. V8 would be awesome, but it WILL require tinkering and tweaking, and lots of parts are bespoke (exhausts, flywheel, mounts etc), and only makes 300-340hp in stock trim, and will likely get very expensive very quickly if you go turbo V8 as everything is then custom.
The S4 engine is a viable option if your wanting big power, but its an expensive one. Engines alone go for bonkers money compared with the 1.8 and v8 options, and its more or less pointless fitting one with the stock K03s, so your down another couple of grand to fit K04's before its even in the car.

 

[phoenixv6quattro]

Thanks for the input gents. I'm favouring the 2.7 bi turbo option purely because of the ballache of fitting a v8. Have considered a PES, but once fitted and even with a smaller pulley it will struggle to make 300 horses. Does anyone know of any good specialists that will be able to do a conversion for me?

 

[aragorn]

Someone like Unit20 or MRC would probably do the job.

Wont be very cost effective paying someone to do it though i dont think. You'd be cheaper just buying an S4 and swapping your bits onto it.

Consider that S4 owners would expect to pay around a grand to have the engine removed and refitted (for example for changing the turbos) and thats without any conversion work at all, your probably talking a realistic figure of around 2k for the actual conversion (excluding buying the engine), maybe a little more depending how you source the conversion parts. With the cost of a good engine with all the required fixtures and fittings being probably over a grand, more still if your wanting the 6 speed and its associated parts, just doesnt seem worth it when you can buy a complete S4 for 3-4 grand.

 

[Talkwrench]

My money is on the VR6 turbo, if your gonna go through the ball ache of changing motors why not make it a bit more unique? S4 engines while very nice they CAN be a nightmare to look after/service/maintain plus cost a boat load to tune properly, the VR6 turbo built right will wipe the floor with an S4, K04's an all and be alot cheaper. If you went the 2.7 Bi-turbo route, just buy an S4 it will be far cheaper in the end. Oh and the 2.8 & 2.7 blocks are NOT the same before anyone gets carried away!

 

[Broken Byzan]

V8 would be my plan.... NOM

If this 1.8t ever goes south, it will have serious thoughts on next transplant

 

[Talkwrench]

Hmmm, can't deny they sound well but I guess it depends what your after. You can slap a NA V8 with a boosted motor no question. My first choice would be a I5 built to the max with a large turbo if only it fit properly in a B5, a proper Audi needs a turbo!

When my 2.0T goes pop I will be going the VR6T route I think unless an RS6 motor comes up cheap (yeah right!). Horses for courses obviously.

 

[aragorn]

why not just boost a normal 32v V8 rather than hunting down a cheap RS6 motor?

 

[phoenixv6quattro]

Gents, put a LOT of work into the car I have, so swapping parts over isn't practical. I have got it as close to my ideal B5 as I deem possible shy of the engine. It is tempting to sell up and buy an RS4, but I've come this far with mine so why not go the whole 9 yards! I simply havnt the time now to do it myself so would be looking to spend between 3 and 4 k on a GOOD conversion. The VR6 does sound intersting. How easily is this done?

 

[Talkwrench]

why not just boost a normal 32v V8 rather than hunting down a cheap RS6 motor?

For a number of reasons really, the older 4.2's are alloy blocks with alusil plated bores if im not mistaken? I would steer clear of these for a FI build, they can't be repaired and tend to cause issues on standard motors. I suspect the crank main cap bolting arrangement wouldn't be as substantial either in a NA V8. I also suspect that the NA motors might not have oil squirters. Plus the RS6 motor has 5V's per cylinder so offers a higher VE than the 32 valver, the other option is the 3.7 V8 which is an iron block but they aint easy to find anymore.

Gents, put a LOT of work into the car I have, so swapping parts over isn't practical. I have got it as close to my ideal B5 as I deem possible shy of the engine. It is tempting to sell up and buy an RS4, but I've come this far with mine so why not go the whole 9 yards! I simply havnt the time now to do it myself so would be looking to spend between 3 and 4 k on a GOOD conversion. The VR6 does sound intersting. How easily is this done?

If thats the case dude and you want to hang onto that chassis I would go for the VR6 myself, If I could go back to the beginnning I wouldn't build the 20 valve again and wouldn't hesitate in starting a VR build. It isn't the most straight forward swap but nearly all the parts to make it fit are OEM depending which VR motor you went with. I believe the VR will be easier to work on than the 2.7V6 and wouldnt be hard to outrun S4's & RS4's plus they sound awesome under boost. There are plenty of VR builds in B5's over the pond on Audizine or motorgeek, I'm not sure if you will find a company willing to take it on for £4K, that would be a stretch doing it yourself, but the 2.7 route wouldn't be any cheaper either & christ I can outrun stockish ones in the 2.0 litre. I guess the best question to ask is what exactly are you after? A nice torquey bottom end or howling neck snapping top end? Its very hard to have both.

 

[aragorn]

All the V8's are alloy block made from alusil (its not a plating, its the alloy the entire block is cast from, which then allows them to run liner-less), including the 3.7s and the RS6.

If it works in the RS6 why wouldnt it work for "normal" v8's? You could just as easily use a 40v NA motor rather than the 32v, the 32v's are just easier to get a hold of and cheaper, and tbh i doubt there would be that much in it unless you were going for properly mega power figures, as the valve area between the two isnt hugely different.

My ABZ certainly has oil squirters, but i cant speak for the newer engines although i doubt they'll have removed them.

 

[Talkwrench]

All the V8's are alloy block made from alusil (its not a plating, its the alloy the entire block is cast from, which then allows them to run liner-less), including the 3.7s and the RS6.

If it works in the RS6 why wouldnt it work for "normal" v8's? You could just as easily use a 40v NA motor rather than the 32v, the 32v's are just easier to get a hold of and cheaper, and tbh i doubt there would be that much in it unless you were going for properly mega power figures, as the valve area between the two isnt hugely different.

My ABZ certainly has oil squirters, but i cant speak for the newer engines although i doubt they'll have removed them.

Well if thats the case I wouldn't touch any of them! All I know is that alusil / Nikasil = poo. I have had experience of nikasil bores in MX bikes and i would avoid them at all costs, You can't rebore those blocks and they do cause problems, once it starts you can't do a damn thing about it. If I put a V8 in my B5 I would push it to the limit therefore any technical advantage of having a more substantial crank cap arrangement would be a big plus, why stick with the normally aspirated V8 when you can get more from a blown lump? I just think using an alusil block isnt for big horse power builds but thats only my opinion. I would also like to add that the importance of VE shouldn't be under estimated, the valve area may be comparable between the 4V & 5V but there flow dynamics are different, Audi didnt develop the 5V head as a marketing ploy did they!

 

[aragorn]

I certainly wouldnt put nikasil and alusil in the same boat. Nikasil was used by BMW for their 6 and 8 pot motors in the mid 90's and was a spectacular failure, the nikasil reacts with sulphur in the petrol and ruins the bore walls. BMW switched to alusil after a few years and that sorted the problems.

I wasnt suggesting running the V8 as an NA motor, i was suggesting starting out with an NA block as a base, and then turbocharge it, rather than trying to find an RS6 lump.
RS6 engines make big power and i've never heard of any major failures? MTM also did a conversion where they decanted the RS6 internals into a standard 40v block so it would bolt up to a manual tranny, so again, the block must be reasonably comparable.
You also need to remember that for a given power figure, the V8 will be much less stressed. If you say you want 700hp, your looking at 175hp per cylinder from a 1.8T, 116hp per cylinder from a V6/VR6 or 87hp per cylinder from a V8.
In terms of cylinder loadings, that 700hp V8 is under the same sort of load as a 350hp I4, and i'm sure you'll agree 350hp is pretty trivial for an I4 engine (i'd certainly happily run a stock 1.8T at 350hp, perhaps with some rods thrown in as a safety). Add to that the cylinders in the V8 are larger (~525cc rather than ~450cc in the 1.8T and vr6 engines) which further reduces cylinder/piston loading.

Audi also ditched the 5v design when they went FSI, so it cant have been better by enough to keep it around once they'd developed the direct injection system...

I agree, the fact that reworking the V8 engines bores etc is dodgy ground does place a question mark over it, but i think the results from the RS6 motors show that they are easily capable of the sorts of power you'll get from a VR6 build.

Theres a big build thread on motorgeek with a guy thats running a 32v V8 in a B4 coupe, with a pair of T3 super 60's running 20psi, and all hes done to the motor itself is fitted stacked headgaskets. I'm sure that motor must be running over 600hp with those pressures out of those turbos, and its a completely stock motor internally barring the extra head gaskets.

 

[Talkwrench]

I certainly wouldnt put nikasil and alusil in the same boat. Nikasil was used by BMW for their 6 and 8 pot motors in the mid 90's and was a spectacular failure, the nikasil reacts with sulphur in the petrol and ruins the bore walls. BMW switched to alusil after a few years and that sorted the problems.

I wasnt suggesting running the V8 as an NA motor, i was suggesting starting out with an NA block as a base, and then turbocharge it, rather than trying to find an RS6 lump.
RS6 engines make big power and i've never heard of any major failures? MTM also did a conversion where they decanted the RS6 internals into a standard 40v block so it would bolt up to a manual tranny, so again, the block must be reasonably comparable.
You also need to remember that for a given power figure, the V8 will be much less stressed. If you say you want 700hp, your looking at 175hp per cylinder from a 1.8T, 116hp per cylinder from a V6/VR6 or 87hp per cylinder from a V8.
In terms of cylinder loadings, that 700hp V8 is under the same sort of load as a 350hp I4, and i'm sure you'll agree 350hp is pretty trivial for an I4 engine (i'd certainly happily run a stock 1.8T at 350hp, perhaps with some rods thrown in as a safety). Add to that the cylinders in the V8 are larger (~525cc rather than ~450cc in the 1.8T and vr6 engines) which further reduces cylinder/piston loading.

Audi also ditched the 5v design when they went FSI, so it cant have been better by enough to keep it around once they'd developed the direct injection system...

I agree, the fact that reworking the V8 engines bores etc is dodgy ground does place a question mark over it, but i think the results from the RS6 motors show that they are easily capable of the sorts of power you'll get from a VR6 build.

Theres a big build thread on motorgeek with a guy thats running a 32v V8 in a B4 coupe, with a pair of T3 super 60's running 20psi, and all hes done to the motor itself is fitted stacked headgaskets. I'm sure that motor must be running over 600hp with those pressures out of those turbos, and its a completely stock motor internally barring the extra head gaskets.

Kev im fully aware of the short comings of nikasil/alusil blocks my man, the fact still remains I personally wouldn't use one for a high HP build.

I here what your saying about the stress at the same hp levels in a V8 compared to I4 kind of an obvious statement really, but what about an RS6 at the same "trivial" horsepower per litre as a 400Hp 2.0? What then? Surely the idea of pushing a motor to the limits of what i can do is to push it to the limit?

As for the 5 valve heads, im not sure I agree with your statement. Are you suggesting that Audi made a mistake using the 5V head when a 4V would have produced the same or similar? Surely not.

Reworking an alusil blocks bores isnt dodgy ground it just can't be done.

While there are many motors making good power with stock internals it doesn't mean its right, I bet there resistance to knock will be virtually zero. When an engine pre-ignites the cylinder pressures can easily be 10 times higher than normal operating pressures therefore the rods get bent like paper clips or worse they punch a window in the block!

We could debate forever about applicable engine technologies but the fact remains making lots of horsepower per litre puts alot of stress on components and the wear rates go through the roof. So why would anyone start an engine build with an already compromised block? Surely your just asking for it!

I would like to add that the most powerful Audi engine I've ever come across was a good old I5 motor.

 

[aragorn]

I think the point i was trying to get at was that you wouldnt NEED to push the V8 to the limit to get a ****-ton of power out of it. An RS6 will do 600hp as it rolled out the factory more or less, and 600hp in a B5 is going to be bonkers.

If you look at it as wanting a specific amount of power rather than just maxing the engine out, then you can see a V8 could be a viable option.

My point was that you could have a V8 making a relatively unstressed 500hp, rather than a smaller engine wringing its neck, and it would be nicer to drive and quite likely require less work internally, than the same amount of power from a 1.8 or 2.8 motor.

As for the 5v, i'm simply saying Audi dont use it any more. Maybe thats because the logistics of trying to fit 5 valves and the FSI port into the head makes it impossible, but the FSI engines are all 4valve.

You CAN rebore alusil blocks, unfortunately its not as simple as good olde cast iron. The difficulty is typically in getting the oversize pistons and the correct oversize rings designed for an alusil block. Audi for instance treat the short block as a throwaway item, and dont as a result sell replacement parts for it. It can be reworked though: http://www.motorgeek.com/viewtopic.php?p=469482

http://www.kolbenschmidt.com.tr/pdf/brochure/KS_50003804-02_WEB.pdf