P.D.Q

I have been plagued with engine trouble with my 2.8 12V V6 C4 100 and now the engine has finally submitted to defeat.

So i now need a new engine but i have been offered a very good condition low mileage 2.8 30v for very silly money. But i need to work out just how cheap the engine will be once all the extras are worked out.

What do i need to do to put the 30v in to replace the 12v.
I know the ECU will need tweaking but what else will i need to do?

The_Hamster

Probably would not take much.

Guesses:

You could probably almost plug and play the whole thing. Might take a little bit with th exhaust manifold -> downpipes, but other then that it will probably be pretty straightforward if I were to guess. I imagine you could wire up the current ECU to the motor and it would run it. Won't run it optimally (wrong maps in it etc), but it will likely run fine enough to not be a major issue.

a6hcw

The transmission will be different, if the 2.8L 30V came from a C5 Audi. Hence, it would be too costly of a prject for a novice. You need to get an engine which has the same configuration as the existing.
I bought a 1996 A6 Sedan and a 1996 A6 wagon each for $3,000. If your Audi 100 is high mileage, then it may be difficult to justify spending more than what a 1996 A6 is worth.

4Driver4

The engine will bolt to the transmission, but after that it gets silly. Are you prepared to fabricate engine mounts? Rework the exhaust? Rewire the car?

Find the right 12v engine and install that.

4Driver4

Guess again. The engines and engine management systems are vastly different. A major component of the 30v is variable valve timing, controlled by the ecu. The 12v ecu has no "knowledge" of this.

The_Hamster

If the valve timing is fully electronically controlled then ya, you are screwed.

Find a normal 12v would be far easier at that point.

a6hcw

The newer C5 Audi with the 2.8L 30V engine, requires bumper removal, etc. to change the timming belt. So, the 30V engine may require significant front end modification of the frame and subframe and suspension to fit into an Audi 100. Even if the old transmission bolts to the engine, it may not be strong enough for the new engine.
The Audi 100 was only OBDI, not OBDII. It is difficult for a novice to rewire a computer controled vehicle, since the ECM, TCM and instrument panel must be compatable. Some of the newer computers work with an imobilizer, which may be in some of the newer instrument panels.
You could end up with a car unable to run or to pass the emissions inspection.
Go to www.vagcat.com , which has a parts catalog with pictures for the European Audi. However, the European 30V engine may not be the same as the USA 30V engine.

a6hcw

A 1999 Audi A6 2.8L 30 valve engine is shown in an AudiWorld Tech Article: https://www.audiworld.com/tech/eng39.shtml
You may see that this engine needs more space than the 2.8L 12 valve engine. What you don't see is that the C5 chassis is built around this 30valve engine. So, the front frame, subframe and suspension are completely different that on the C4 chassis.
That is why it would be too expensive to swap this 1999 Audi 2.8L 30 valve engine in to an old Audi 100 with C4 chassis.

P.D.Q

Thanks for all the replies guys :-)

Some very usefull info there.

I shall just try and find a 12v to drop in this time but i shall keep my eyes out on the 30v lumps and see if it is possible or a complete no go for reference on here as this thread is good info for the future.

Jrmccrary

I know its an old tread but I'm in a similar situation.I've got a 96 a4 quattro 2.8 12v auto.well its got 162k on it an i can hear a knock.now i know that means the rod is spun.so the motor needs to be built or replaced.well I've been thinking...this would be a great time to try and see if a 30v would bolt up to the car and work.so here's my questions will a 30 valve bolt up and run with my old trans? or i found a 5spd that goes with the motor dwm for sorta reasonable price.so say i was gonna do the motor and trans swap.what all would i need? and do u guys know of anybody that has or is doing it?i know sum of you guys are gonna say it would be cheaper to just buy a stick.i kinda know that but..i like this car and just wanna have sum fun in it,and at the same time fix the problem with it.any answers would be helpful.thanks