2.5 to 3.4 conversion

[yfz/700R]

Originally Posted by pecivil

I am supposed to get my 00 box back from the shop tomorrow from its 3.4 conversion. :dance:

I can speak for Steve Timmons at Instant G. I bought the entire instant g header/cats/muffler set up for the conversion. The quality of his product is outstanding. It takes a awhile to get it, as he makes them when he gets an order. It is not cheap, but the stock boxster header/cat/muffler strangles the 3.4. Of course you can't use the 3.4 stock exhaust stuff cause it dont fit.

You can probably sell your 2.5 for something. I bought a used 2001 3.4 with 31k miles taken from a front end wreck. Subtracting out the price I got for my 2.7l (with 56k miles) the 3.4 cost $4500. My mechanic was able to throughly go over it before I paid.

On the clutch, you cannot use 996 components with the boxster 5 speed tranny. The splines dont match. Plan on buying completely new clutch stuff. My clutch was shot at 56k, and I also needed a new flywheel, as it was too messed up to resurface. I went with the AASCO lt wt flywheel. At least, you pay no extra for labor, since the tranny is already out.

The 996 carrera came with the center radiator, like the Boxster S. You need to think about wheather or not to add it. There are a couple of places that sell a add on kit for it, or your mech can just buy the stock porsche parts. I decided to add it to be safe, but my mech told me that you are probably ok without it for the street. Of course, if you do add it, you will need a boxster S or 996 or GT-3 front bumper cover with the opening for it.

Have you mech replace the RMS on the 3.4 as a precaution. Use the new, revised seal.

You will need a 3.4 throttle body. The boxster one does not work. You will also need some "revised" intake tubing, as again the stock boxster one does not make it distance wise to the filter.

Another easy thing to add is a oil temp & pressure gauges. You use the 3.4 oil pressure sender already on the engine. Add a temp sender on the opposite port (to the oil pressure sender) on the block, and run the wires in to the cabin. I am going to mount then in one of the cubbies below the radio.

You can also do a ECU remap for the 3.4 from GIAC or FVD. They take into account the exhaust mods if you get them. I am going with GIAC.

FVD also has "sport cats" for this engine, which they add to their conversions, I believe. I will see how it feels without the cams. I may add them later. Supposedly they make a big "feel" difference in the motor.

Hope this helps

Monte

so how does it run? did they do a good job on the install?

[Rail26]

pecivil...thanks for the great write up. I am not interested in doing the conversion, but always wondered what was involved. I would love to know how the conversion stands up to the new '07 box.

[pecivil]

still waiting to get her back..... the shop doing it is a very good shop, but it is only a 2 man shop and they are taking forever!! They work on several racecars, so every Friday, they tend to only work on racecars going out that weekend, and on Monday, they tend to only work on broken race cars coming back from the weekend. So all the "street" cars they work on get squeezed into Tues, Wed, Thurs.

Friday was the 2nd "it'll be done" that didnt happen. But the bottom line is they are doing an excellent job, which is what really matters.

So....I should get it this week. As soon as I get it, I will do a write up on how it feels.

[WillieB]

I should have my 3.4L Conversion back as well by Wednesday. It has been approx. 3-4 weeks. But went to look at her on Sat. and she is looking great. Fired up on the first crack. Remaining parts to be added cats, exhaust, etc. I have a 99 Boxster pre-egas. Can't wait! Props to Todd Holyoak and Trent Carter for their assistance on this. The information they have provided on this has been awesome!!!

[z12358]

Are there any limitations that prohibit dropping a 3.8L engine into a pre-2000 Boxster? Is the 3.4L the largest engine that fits? How about in a post-2000 Box? In other words, is a 3.8L mid-engine track car possible for around $30k ($15k for old Box + $15k for mods)?

Z.

[RandallNeighbour]

All you 3.4 conversion guys need to post observations, impressions, pix, movies, etc. for all of us 2.5 Boxster owners wanting to do this one day but being too broke today to do it!

[pecivil]

based on what I found out, it isn't the physical size of the engines, its the electronics that control them.

If you have a pre 00 boxster you do not have Egas. So the easy swap (easy meaning that the ECU and wiring stuff all is pretty much P&P) is a 3.4 carrera engine that did not have egas.

If you have a 00 or 01 boxster (I am not sure about 03) then you want a 00 or 01 carrera 3.4. This engine has egas, and has variocam, exactly like the boxster 2.7 does.

If you have a 00 Boxster S, then you go with a carrera 3.6. This engine has variocamPlus, which the boxster S has. Plus it has the 6 speed tranny, that is the same as the 996.

If you have a 03 or later boxster, I think you go with the 3.6 carrera engine.
If you have a 03 or later BoxS, then I think you can do the 3.8. Not positive on this.

If you have a 987, then you definitely go with the 3.8.

So its not that you can't do the 3.6 or 3.8 in the earlier boxsters, but you need lots!! of electronic wizardry to make the electronics work right. I think it has been done, but it makes the swap much more difficult, time consuming.

I would have loved to done a 3.6, but my 2.7 doesnt have variocamplus, only variocam, so I needed a 3.4 to be plug & play with my stock harness & ecu.

Make sense?