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Mazda MX6 2.5 V6 24V conversion
09-22-2014, 10:15 AM (This post was last modified: 09-22-2014 10:20 AM by ian.)
Post: #1
Mazda MX6 2.5 V6 24V conversion
I've had this engine in my Syncro for about 2 years now and have been meaning on starting a thread on it for about the same length of time!

Long story short, Bernard (BHM) bought a Syncro that came with this engine. The conversion was poorly done. Sump almost dragging on the ground and a mess of wiring. They had tried to use only the original FWD engine mounts and had welded in brackets and mountings to try and accomplish this. Understandably Bernard wanted to get shot of it as soon as possible and prep the vehicle for a tdi conversion.

Anyway, I knew the Mazda motors and after a bit of homework a deal was done. I knew if the conversion could be done properly the motor would be awesome. One of the best ever standard production V6's, eclipsed possibly only by Alfa's masterpiece V6. It is also the most compact and lightest standard production 2.5 V6 ever made. Significantly lighter than a Golf 2.0 8v inline 4. The VW/Audi 2.6 5 cylinder puts out 100kw and 200nm and this is considered the upper limit for our fragile boxes. The MX6 engine puts out 125kw and 220nm, so with a bit of understanding and sympathy, it's not a gearbox killer. Basically the same output as the Subaru 2.5, and just like the Subaru, it's a neat, well engineered, and cohesive package. Unlike the VW motors of the time, where the ancillaries look like an after thought project for some students, and covered in a maze of pipes.

The design incorporates a highly-rigid, aluminum split-crankcase engine block design with 4-bolt mains with additional bolts securing the lower block, an internally balanced forged steel crankshaft with lightweight powder forged carbon steel connecting rods.

Mazda introduced a key technology with these engines, known as the Variable Resonance Induction System (VRIS). A series of two butterfly valves coupled with electronically controlled actuators varied the volume and length of a resonant chamber within the intake manifold. The valves actuate at particular engine frequencies (i.e. rpms) to produce optimal torque/horsepower output at any given engine speed.

Apparently there was some technology sharing with Porsche, who were at the time also developing a V6. Mazda shared their VRIS technology and Porsche had some input in the crankcase and head design. As far as I know, Porsche later passed on their unfinished project to F0RD and the engine became the Duratec V6 which is very similar to the Mazda KL engine.

This was a time when the Japanese motor industry was at an all time high and it shows in this engine. Beautiful engineering and no bean counting cost cutting in sight!

Just a pic to show the size of the engine. This is a conversion into the tiny Mazda MX5 engine bay and look at how much space there is.

I decided to go with a dual, equal length exhaust which then allowed me to use the cut away in the sump, which normally accomodates the exhaust, to run a cross member onto which I could attach the engine mounts. Because of this the cross member sits nice and high up. These pics show the cross member and how the engine fits into the engine bay. I have a raised engine lid, but the engine hardly comes any higher than the standard deck lid.


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09-23-2014, 01:36 PM
Post: #2
RE: Mazda MX6 2.5 V6 24V conversion
I drove a couple of MX6s when they first came out and was very impressed with that 2.5 V6 at the time. Do you have pics of your conversion from the top? Also what's it been like to live with over the past year?
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09-23-2014, 03:11 PM (This post was last modified: 09-23-2014 03:14 PM by ian.)
Post: #3
RE: Mazda MX6 2.5 V6 24V conversion
Ah Nico you'll have to wait until the end of the thread to see the finished install! But I can say I am very happy with it. I have put a lot of hard km's on it and the engine has been awesome. Honestly it's the best thing I've done to my Syncro. It is so much more fun to drive and on long heavily loaded trips it is a pleasure. The motor's characteristics seem to suit this application perfectly. I knew the motor had the right specs and on paper the torque curve looked impressive but I never expected a 24 valve high revving motor to pull like this one does from idle. That is what makes the biggest difference. All those slow 90 degree corners in town that required 2nd gear before are now effortless in 3rd. And it is absolutely, fantastically, smooth all the way through the rev range. If you are ever in PE you are more than welcome to pop in and try it.

Most conversions use an adapter plate between the engine block and bellhousing, but the Mazda flywheel is just too big to fit inside the T3 bellhousing. This install uses an adapter that goes between the T3 gearbox casing and the Mazda bellhousing. This enables all the standard parts to be used. Standard Mazda flywheel and pressure plate and standard Syncro clutch plate. I like using as few custom parts as possible so this arrangement works well. It also means you use the standard Mazda starter which is much better and you can get rid of the terrible T3 clutch slave cylinder. And it means the starter can be removed in about 5 minutes, which is very much not the case with the standard T3 starter!

I only have a poor pic of the adapter attached to the Syncro gearbox. Not a thing of beauty but it works.

The other thing I wanted to get away from was VW's horrible collection of rubber hoses. I made up stainless pipes and bends and used a few pieces of standard size, off the shelf, hoses to connect them.


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09-25-2014, 04:47 AM
Post: #4
RE: Mazda MX6 2.5 V6 24V conversion
(09-23-2014 03:11 PM)ian Wrote:  Ah Nico you'll have to wait until the end of the thread to see the finished install! But I can say I am very happy with it. I have put a lot of hard km's on it and the engine has been awesome. Honestly it's the best thing I've done to my Syncro. It is so much more fun to drive and on long heavily loaded trips it is a pleasure. The motor's characteristics seem to suit this application perfectly. I knew the motor had the right specs and on paper the torque curve looked impressive but I never expected a 24 valve high revving motor to pull like this one does from idle. That is what makes the biggest difference. All those slow 90 degree corners in town that required 2nd gear before are now effortless in 3rd. And it is absolutely, fantastically, smooth all the way through the rev range. If you are ever in PE you are more than welcome to pop in and try it.

Most conversions use an adapter plate between the engine block and bellhousing, but the Mazda flywheel is just too big to fit inside the T3 bellhousing. This install uses an adapter that goes between the T3 gearbox casing and the Mazda bellhousing. This enables all the standard parts to be used. Standard Mazda flywheel and pressure plate and standard Syncro clutch plate. I like using as few custom parts as possible so this arrangement works well. It also means you use the standard Mazda starter which is much better and you can get rid of the terrible T3 clutch slave cylinder. And it means the starter can be removed in about 5 minutes, which is very much not the case with the standard T3 starter!

I only have a poor pic of the adapter attached to the Syncro gearbox. Not a thing of beauty but it works.

The other thing I wanted to get away from was VW's horrible collection of rubber hoses. I made up stainless pipes and bends and used a few pieces of standard size, off the shelf, hoses to connect them.
Ian
Can't wait to see this once it is done! I am always amazed what you guys come up with back in SA. Please take lots of pics and update this thread I will be following closely.

Regards
Gerrie
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09-25-2014, 11:04 PM
Post: #5
RE: Mazda MX6 2.5 V6 24V conversion
And here is the end result.


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09-26-2014, 09:39 AM
Post: #6
RE: Mazda MX6 2.5 V6 24V conversion
That looks very nice. I had thought about the MX6 V6 as a possible conversion choice a while back, but never new anyone had actually done a project like this. Do you have dual exhausts?
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09-26-2014, 10:23 AM
Post: #7
RE: Mazda MX6 2.5 V6 24V conversion
Thanks Nico. As far as I know this is the only one in the world. Another reason I like it. I do have dual exhausts and the sound is great. Pretty quiet but just enough volume when you let it sing. Especially up a mountain pass with the windows down. But I don't like the aesthetics very much as the silencers are very visible. I'm going to look at doing something like the white 911 exhaust soon, with small silencers and then protection bars that go all the way up to the bumper, so that the silencers are protected and also mostly hidden.


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09-26-2014, 01:47 PM
Post: #8
RE: Mazda MX6 2.5 V6 24V conversion
Lovely Ian!!

Pray tell what your fuel consumption figures are like?

Cheers
Johan

Syncro or bust....
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09-26-2014, 02:19 PM
Post: #9
RE: Mazda MX6 2.5 V6 24V conversion
Ah the akward question! Fuel consumption is not great to be honest! But not bad either. If I drive nicely I get 7km/l fully loaded, and if I push it a bit it will drop to 6.5km/l. It's about what I expected really, and power and driveability is way more than I expected, so overall I'm happy. With my 2.0 litre I was getting no better than 7.5 km/l and power wise there is no comparison. If you consider the power difference between the two motors the fuel consumption should be worse! To me the little bit extra fuel cost is well worth it.

I don't think you can have this kind of power with much better fuel economy unless you go the turbo diesel route. Maybe 1.8T might be better in terms of power/fuel consumption ratio?
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09-28-2014, 10:59 PM
Post: #10
RE: Mazda MX6 2.5 V6 24V conversion
(09-25-2014 11:04 PM)ian Wrote:  And here is the end result.

Damn Sexy!!Wink
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