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Old 04-01-2020, 04:00 PM   #1
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2.5 auto/manual differences?

Hi all, just wondering if there is any issue installing a 2.5 automatic trans engine into a car with a manual?
Is the only difference the flex plate/flywheel?
Does this swap work with no issues?
I have seen online that the wire harness is different. Is that true?
This is going into a racecar that currently has a 2.7 with manual trans.

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Old 04-01-2020, 04:22 PM   #2
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Yes, an engine from an auto trans car can be installed in a car with a manual trans. I did this on my Spec Boxster. You'll need to do the following:

Swap the following parts from the manual engine to the automatic engine
1. Engine wiring harness
2. Clutch, pressure plate, flywheel
3. Remove air conditioning compressor and all a/c lines on auto engine
4. Under-drive pulley and shorter serpentine belt
5. Check cooling hoses - there should be a 4 way "T" and a 3 way "T" cooling hose on the Tip motor. Use the 3 way hose and the "L" shaped hose from the Manual motor
6. Check vacuum lines - The vacuum line on the tip at the intake has a 4 way tee. Use the 3 way "T" from the manual motor.
7. Use the larger "S" oil cooler and use new o-rings
8. New plugs, air filter, oil, oil filter. Refill coolant.
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Old 04-02-2020, 09:14 AM   #3
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Also, you might want to remove the 2.5 secondary air injection pump (SAI) and install the SAI line blocking plates (this may or may not have been done on the 2.7 but you might want to do it on the 2.5).

Or you can just remove the pump and then plug the existing hose. That will at least get rid of the weight of the pump.
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Last edited by thstone; 04-02-2020 at 08:31 PM.
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Old 04-02-2020, 06:54 PM   #4
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Quote:
Originally Posted by 986buzz View Post
Hi all, just wondering if there is any issue installing a 2.5 automatic trans engine into a car with a manual?
Is the only difference the flex plate/flywheel?
Does this swap work with no issues?
I have seen online that the wire harness is different. Is that true?
This is going into a racecar that currently has a 2.7 with manual trans.
You say that the car currently has a 2.7L engine. Have you already addressed the differences between the 2.7L engine and the 2.5L engine? THAT is bigger than the change from the auto to manual. Does the car have an eGas throttle or cable? Which DME/ECU? Which intake set-up will it use?

I have swapped a 1997 2.5L manual engine into a 2001 Tiptronic. I have also swapped a 2001 manual with a 2001 Tiptronic. In addition to what Tom mentioned the vacuum hose for the brake booster on the manual set-up connects to the left front of the engine. It is right rear on the Tiptronic. It's simple to just swap the fittings from one to the other.

Edit: I just back-tracked through your earlier threads. I'm assuming now that the car is an actual '99 and that the 2.7 was set-up to run as a 2.5 as far as intake, DME, and throttle. Hopefully that makes it a pretty simple drop in swap with the harness, flywheel, and a little plumbing as noted.
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Last edited by 78F350; 04-02-2020 at 07:05 PM.
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Old 04-03-2020, 05:30 PM   #5
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Thank you all for your replies. Some great points were brought up so I need to do a little looking around to see how this car was set up. I know nothing about Boxsters so this will be a learning moment.
I can google the DME number to see if it is a 2.5 or 2.7.
Once the local track opens back up I can go do a test day with the 2.7 and verify all systems are good and then start sourcing a 2.5.
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Old 04-04-2020, 04:54 AM   #6
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Quote:
Originally Posted by 986buzz View Post
Thank you all for your replies. Some great points were brought up so I need to do a little looking around to see how this car was set up. I know nothing about Boxsters so this will be a learning moment.
I can google the DME number to see if it is a 2.5 or 2.7.
Once the local track opens back up I can go do a test day with the 2.7 and verify all systems are good and then start sourcing a 2.5.
If your dme has one big connection, it's a 2.5. Multiple connectors will be 2000+

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