How to get a 4.2L V8 into a Turn Key for a swap.

thecharlum · 08-01-2011, 01:52 AM

I am looking to swap a Audi v8 4.2l into a Mazda Miata. Mainly because its the cheapest lightest 400hp 8,000rpm engine available. It can be mated to a t56 transmission so that is not a issue. I need to know what would be involved with trying to get the v8 to be a standalone turn key engine. Would I need to get a aftermarket engine management system and rig it all up and tune it out on a engine dyno? or Is it possible to get the ECU and engine harness from the donor vehicle to work as a stand alone. I think a after market stand alone engine management will work, but how are the dual intake runners controlled on the engine? Is it controlled via vacuum hose or is it electronic activated? Any input would be greatly appreciated.

TECHNAUT · 11-16-2011, 06:21 PM

i know the runners are vacuum powered, not sure if theres any electrical to it. your best bet is a donor car..... gonna have to pay for that though.

brittcrowell · 12-25-2011, 12:26 AM

Depends on what 4.2L V8 your talking about too. The older 32v only had one vacuum actuator. The first 40v had 2 vacuum actuators for the flaps and also used electricaly actuated hydrolic timing chain tensioners to advance the intake cam that worked in conjunction with the ecu and cam timing sensors. Regardless you still have 8 injectors and 4 oxygen sensors to deal with too.
I'm guessing your still going to need the ECU and harness to make it work.

Ritz · 01-26-2012, 10:30 AM

I'm sure the original poster is long gone, but I doubt this is do-able for a sane amount of $$$. Why not take the already trodden road that Monster Miata uses and go with a Ford V8? A marine 351W engine is good for 350hp normally aspirated. Throw a centrifugal supercharger on there and you've got your 500+hp and an existing blueprint for how to do the swap. 351W marine crate engines are pretty cheap....much cheaper than an Audi 4.2L (which is only good for about 350hp normally aspirated too).

Best,

NHMark · 06-05-2012, 05:02 PM

I looking for the ECU wiring diagram for a 1998 A8 as i am performing a 4.2 swap into a Pontiac fiero . I know there are better engines but this engine is nice and short better for longitudinal install plus if you want power these days just put a turbo on it

Omni1969 · 09-02-2012, 10:19 AM

I have the motor, and the ECU with wire harness for you if you want it. just give me a call and we can talk, I have a complete donor car if you need it. 301-379-2624 Mark

12-25-2011, 12:26 AM	#3
brittcrowell AudiWorld Member Garage is empty, add now Join Date: May 2005 Posts: 356	Depends on what 4.2L V8 your talking about too. The older 32v only had one vacuum actuator. The first 40v had 2 vacuum actuators for the flaps and also used electricaly actuated hydrolic timing chain tensioners to advance the intake cam that worked in conjunction with the ecu and cam timing sensors. Regardless you still have 8 injectors and 4 oxygen sensors to deal with too. I'm guessing your still going to need the ECU and harness to make it work. __________________ 1997 A8 Quattro hot/cold 171,375 miles Tranny Dead! :-( Broken arm rest Broken cruise control (its a moot point now!) 2001 A8L Pearl White hot/cold Boss's Car (God She's Hot!) 87,774 miles

01-26-2012, 10:30 AM	#4
Ritz AudiWorld Super User Garage is empty, add now Join Date: Oct 2003 Location: NYC Posts: 5,148	I'm sure the original poster is long gone, but I doubt this is do-able for a sane amount of $$$. Why not take the already trodden road that Monster Miata uses and go with a Ford V8? A marine 351W engine is good for 350hp normally aspirated. Throw a centrifugal supercharger on there and you've got your 500+hp and an existing blueprint for how to do the swap. 351W marine crate engines are pretty cheap....much cheaper than an Audi 4.2L (which is only good for about 350hp normally aspirated too). Best, __________________ --- 2002 A4 1.8TQM mod-free at the moment (gotta deal with that) Formerly...2001 A6 2.7T quattro 6sp w/GIAC X Before that...1999 A4 1.8T 5sp w/lots o mods

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11-16-2011, 06:21 PM	#2
TECHNAUT Audiworld Junior Member 2004 Audi S4 Join Date: Nov 2011 Posts: 34	i know the runners are vacuum powered, not sure if theres any electrical to it. your best bet is a donor car..... gonna have to pay for that though.

06-05-2012, 05:02 PM	#5
NHMark AudiWorld Newcomer Garage is empty, add now Join Date: Jun 2012 Posts: 1	I looking for the ECU wiring diagram for a 1998 A8 as i am performing a 4.2 swap into a Pontiac fiero . I know there are better engines but this engine is nice and short better for longitudinal install plus if you want power these days just put a turbo on it

09-02-2012, 10:19 AM	#6
Omni1969 Audiworld Junior Member Garage is empty, add now Join Date: Jun 2012 Posts: 10	I have the motor, and the ECU with wire harness for you if you want it. just give me a call and we can talk, I have a complete donor car if you need it. 301-379-2624 Mark