2.7 swap for 2.5? (Blown motor)

[The Radium King]

here's the important info from the pelican engine swap article:

- These cars ran the Bosch Motronic 5.2.2 system, which uses a cable-driven throttle body, similar to nearly all earlier Porsches. When installing an engine into one of these early cars, you need to use a cable-driven throttle body and corresponding crossover tube that matches that engine. (I.E. use the cable-driven throttle body from a 1999 996 Carrera when installing a 3.4 engine: the standard 2.5L throttle body is too small). The Boxster cable attaches directly to the 996 throttle body with no modifications necessary.

- Very early 1997 cars had non-programmable DMEs. If you have one of these cars, you might need to purchase a new DME and matching immobilizer to go along with it. Immobilizer codes for these early cars are not stored in the Porsche dealer information system, so there's no way of linking the existing immobilizer to a new DME. Don't buy a 1997 if you are definitely planning on doing an upgrade as you might get stuck with one of these non-programmable DMEs.

- Boxster engines from 2000-02 and all 996 engines have an extra crossover tube with a variable resonance flap that is controlled by the DME. When you reflash your 5.2.2 DME to control the new engine, you also need to add some wires to the DME harness. The resonance flap is controlled by a solenoid switch that then applies vacuum to the flapper. You wire this solenoid by running one wire to a 12V source and the other wire to pin 59 on the DME (the DME controls the valve with a switchable ground).

so, you may be able to just bolt on your entire 2.5 intake, otherwise you will have to address the resonance flap issue (or replace it with a straight tube, or use an rpm-driven window switch) as well as the throttle body issue (2.7 has a larger throttle body than a 2.5 so you can't reuse your 2.5 tb without replacing the plenum as well and not sure how it will mate to the rest of the 2.7 intake runners, etc. - soln is a 996 tb which requires the 996/997 plenum). and there is the non-programmable ecu issue. i don't think you want to get into a dme swap (unless perhaps the new 2.7 is coming with the required electronics?) so i think you are going to have to cross fingers and hope the 2.5 ecu can adapt to the larger displacement of the 2.7 (i know raby would run their 3.6 builds with a 3.2 tune ...). of course this means no re-pinning the ecu to drive the resonance flap.

[truegearhead]

Originally Posted by The Radium King

here's the important info from the pelican engine swap article:

- These cars ran the Bosch Motronic 5.2.2 system, which uses a cable-driven throttle body, similar to nearly all earlier Porsches. When installing an engine into one of these early cars, you need to use a cable-driven throttle body and corresponding crossover tube that matches that engine. (I.E. use the cable-driven throttle body from a 1999 996 Carrera when installing a 3.4 engine: the standard 2.5L throttle body is too small). The Boxster cable attaches directly to the 996 throttle body with no modifications necessary.

- Very early 1997 cars had non-programmable DMEs. If you have one of these cars, you might need to purchase a new DME and matching immobilizer to go along with it. Immobilizer codes for these early cars are not stored in the Porsche dealer information system, so there's no way of linking the existing immobilizer to a new DME. Don't buy a 1997 if you are definitely planning on doing an upgrade as you might get stuck with one of these non-programmable DMEs.

- Boxster engines from 2000-02 and all 996 engines have an extra crossover tube with a variable resonance flap that is controlled by the DME. When you reflash your 5.2.2 DME to control the new engine, you also need to add some wires to the DME harness. The resonance flap is controlled by a solenoid switch that then applies vacuum to the flapper. You wire this solenoid by running one wire to a 12V source and the other wire to pin 59 on the DME (the DME controls the valve with a switchable ground).

so, you may be able to just bolt on your entire 2.5 intake, otherwise you will have to address the resonance flap issue (or replace it with a straight tube, or use an rpm-driven window switch) as well as the throttle body issue (2.7 has a larger throttle body than a 2.5 so you can't reuse your 2.5 tb without replacing the plenum as well and not sure how it will mate to the rest of the 2.7 intake runners, etc. - soln is a 996 tb which requires the 996/997 plenum). and there is the non-programmable ecu issue. i don't think you want to get into a dme swap (unless perhaps the new 2.7 is coming with the required electronics?) so i think you are going to have to cross fingers and hope the 2.5 ecu can adapt to the larger displacement of the 2.7 (i know raby would run their 3.6 builds with a 3.2 tune ...). of course this means no re-pinning the ecu to drive the resonance flap.

Thanks! I saw that info as well. I wonder if I could bolt on a 3.4L cable throttle intake. I don’t believe those have the flap. I also don’t understand why can’t just delete the flap.

[78F350]

I'm in the middle of putting a '97 2.5 into a 2001 base, sort of the opposite swap. In my case, I swapped over all of the 2.7L intake, fuel, harness, and vacuum stuff to the 2.5. The only real creativity involved was making a template and re-drilling some of the mounting holes in the intake a few mm over from where they were.


There's a big difference in the 2.7L intake and the 2.5L intake. By my HF calipers the intake port on the 2.7L engine is 54mm vs 43mm on the 2.5L. Between that and the resonance tube, I'd want to keep the 2.7L intact and look at swapping the DME and adding some wiring and pedal for e-gas.

Easiest way to do it and be back on the track would be a direct swap of all the intake, throttle, engine harness, vacuum, and injector stuff from the 2.5 onto the 2.7 - the reverse of what I did. To re-drill the intake mount, just make a template, knock out the steel spacers, (fill the old holes if you want quality) and drill holes in the replacement intake.

[78F350]

I just realized there may be a problem putting the 2.5L intake runners on the 2.7L engine: The rubber seals may not contact the intake ports on the head due to the smaller diameter.
Solution? ...Fabricate a bolt-thru adapter plate to fit the 2.5L seals and cover the excess port.

[911monty]

Originally Posted by 78F350

I'm in the middle of putting a '97 2.5 into a 2001 base, sort of the opposite swap. In my case, I swapped over all of the 2.7L intake, fuel, harness, and vacuum stuff to the 2.5. The only real creativity involved was making a template and re-drilling some of the mounting holes in the intake a few mm over from where they were.


There's a big difference in the 2.7L intake and the 2.5L intake. By my HF calipers the intake port on the 2.7L engine is 54mm vs 43mm on the 2.5L. Between that and the resonance tube, I'd want to keep the 2.7L intact and look at swapping the DME and adding some wiring and pedal for e-gas.

I will be following this swap with great interest!! I would imagine there would be a dramatic loss in low end torque going to that large an intake on a 2.5. Intake velocity should take a major loss. It will be interesting to hear your impression. Of course if it works out then Porsche really did put the hurt to these engines!

[truegearhead]

I still don’t understand why a 3.4L 996 manifold wouldn’t work. If you don’t have this problem on a 3.4 than why can’t you just use the 3.4 manifolds