Nicholbry

I am considering buying a used 1987 engine for my 1990 S4. With regards to swapping them; what, if any, differences are there between the two that might require modifications, challenges, things-to-know, things-to-do, etc? I'm assuming the wiring harnesses are one issue. What parts might I need for a successful conversion? Has anyone done this before?

I realize the engines are essentially the same, but I'm referring to the details of the swap. I notice that 928intl sells the engines 87-88 & 90-91. While I'm at it I might as well ask, does anyone have an engine for my '90 S4? Mileage? Details?

Thanks

Vilhuer

No exhaust temp probe places in heads at '87-88 engines is one change than comes immediately to mind. Simples way around is either use '89+ heads or delete entire system.

jorj7

The early 87 engines had forged rods and "oil squirter" blocks. Don't know if that
makes a difference in your application. I'm putting an early 87 block in my 90S4,
but using my 90's heads.

Vilhuer

If engine internal changes count there are three different types of pistons for example, '87-88 January, '88 February-89 and '90-91. Only '90-91 engines have really 10.0:1 compression ratio. Earlier S4 can have anything between 9.4 and 10.0. Even though hp numbers didn't change officially its possible later engines have on average slightly more hp.

CS, SE and GT had 10.0:1 as piston dish was smaller from the start.

UKKid35

Weaker heads in the '87 that are more likely to crack than those on the '90

Scott M.

Can the system be bypassed/deleted? I've been wondering this myself but haven't studied it. If so, how?

dr bob

Scott-

You can jumper the protective relays, but if everything is working OK I'd leave it in there. If something fails in the protective system, you can plug in a jumper then. There are just enough horror stories about losing early S4 cars to cat fires to cause me to keep mine intact.

Scott M.

Bob;

I know the cyl head temps sensors work via the ign monitoring system but is there anything else that it factors into, like timing retard? I have the system bypassed on my stroker GTS at the relay so am familiar with that aspect. It would occasionally go limp home mode (nature of the stroked cars). I'm also well versed in the coils shutting down, yada cubed.
I have a 87 motor and a 90 ultra low mileage motor, one of which I need to put into an SC'd 89. I'd prefer to use the 87 due to internal factors but haven't yet studied the outer diffs.

Jim bailey - 928 International

Jump 1,3 and 5 on the plug to the relay and there is no temperature monitor system any longer. BUT if the car suddenly acts like it is running on 4 cylinders and you keep driving, get the Marshmellows ready....

Scott M.

JB;

Yes, you and I discussed this when I got my GTS. My failing memory tried to tell me there was an adverse effect on timing, via EZK, when jumpered and not just ign monitoring.

Mahalo,

Nicholbry

Ahh! So I see that the big issue are the heads. Since I am paying hourly labor for my shop to complete the work it might be best to source a 90-91 specific engine, rather than pay added labor to swap heads over and risk an improper sealing to boot. Any snags along the way will only add to my labor costs and added complexity for a European mechanic who is not as well versed on the 928 as some of you guys. It really sucks not having a fellow 928 guy nearby who is also good with the wrench.

The idea of jumping relays or fuses to delete a critical system is not appealing either. I did so for the tire monitoring system as the PO had installed aftermarket wheels and also for the cooling flaps. These less critical features are fine for hacking and I'll limit it to those types of applications. If I knew more mechanically I might feel more comfortable as I could do checkups, diagnosis, etc in the future to monitor systems, but I would be challenged beyond my abilities with some of these potential hazards.

I really appreciate the input you guys have posted and I welcome any continued info on the subject as I may be forced to get an '87,'88,'89 engine due to availability and cost.

Nicholbry

When inspecting engine prospects where the engine is not mated to a car, is there a way to identify a '90-'91 engine from others? Although he believes it to be an '88, the owner of one engine that I am considering did not know for certain which year S4 the engine was removed.

Vilhuer

Engine number will tell exactly what it is or at least what it was when it left the factory. There is year information in it which follow same logic as VIN year info.

1981=B
1982=C
1983=D
1984=E
1985=F
1986=G
1987=H
1988=J
1989=K
1990=L
1991=M
1992=N
1993=P
1994=R
1995=S

Nicholbry

What might the difference(s) be between the '89 vs. '90-'91 engine? 928Intl has them listed separately. Again, I'm looking for differences that would interfere or obstacles to overcome when doing an engine swap into my '90 S4. Should I expect wiring harness issues; deleted or extraneous systems that might require deleting or fuse manipulation (jumping)? Anything would be helpful as I am trying to hunt down a decent engine that will translate well into my car.

Thanks Errka for providing me with the Alpha designations corresponding with the year.

Vilhuer

As I mentioned earlier '90-91 S4 engines use GT pistons meaning true 10.0:1 compression ratio. That was about only change between '89 and '90 MY as better heads were already taken into use in middle of '89 MY.

Not even '90 and '91 are same. Knock sensor connector were changed in '91 MY to gold plated meaning wiring and sensors need to be same type. Oil bypass valve in block was deleted and exhaust temp monitors moved from rear cylinder pair to one cylinder forward at same time. In US models check engine light was added meaning changes to LH and EZK boxes too.