MIller cycle motor back to a "normal" cycle

The miller cycle motor in the millennia S has always fascinated me. However I was thinking (Ya I know bad idea) on the way home last night that if you took a millennia S motor and had the cam's re ground back to NA spec could you then just add a standard forced induction system and run the motor with a MS or other stand alone system?

One of the things I don't know is the static compression ratio on these motors so low or to high that this would not be feasible.

Ok yes I am thinking of a project.

Anyone know more about these motors? Any good leads on tech on these motors?

i've wondered this for some time.

just add traditional cams, leave the rest of the engine alone.

Can someone give a cliffs notes synopsis of the miller cycle? To busy to Google it.

Essentially the supercharger pressurizes the compression stroke with the valves partially open, IIRC, instead of closing the valves like a normal engine. Good for emissions, so-so for power and MPG I believe.

How Stuff Works wrote: A Miller-cycle engine is very similar to an Otto-cycle engine. The Miller-cycle uses pistons, valves, a spark plug, etc., just like an Otto-cycle engine does. There are two big differences: - A Miller-cycle engine depends on a supercharger. - A Miller-cycle engine leaves the intake valve open during part of the compression stroke, so that the engine is compressing against the pressure of the supercharger rather than the pressure of the cylinder walls. The effect is increased efficiency, at a level of about 15 percent.

http://www.howstuffworks.com/question132.htm

I wonder about just hanging the blower on a normal 2.5 and leaving the 2.3 and weirdo cams behind.

I would imagine the 2.3 is forged.

Isn't the 2.5 the same or at least very similar to the original engine in the Noble M12 that made over 400 HP in standard turbo charged trim? I'm getting close to scrapping my wife's 626 with 2.5 V6 and 5 speed trans if anybody want to make an offer.

I don't know about the internals but the block is a significant upgrade in design. If I remember it is a split block making the bottom end much more robust. I just spent some time goggling but I can not find the page I read a year or so back that gave a very good write-up of the motor.

The other interesting thing is that this motor was introduced before fuel costs went through the roof and thus the added cost of the motor was not negated by the savings in economy. This motor was supposed to give you the performance of a 3L motor with the economy of a 2L motor. All from a 2.25L motor.

In reply to tr8todd:

I think that they may have used the Ford Duratec. However, That may not have been the "first" motor. It was what they used in later models though. I would love the 626 motor but you aren't located anywhere near me, sadly.

In reply to tr8todd:

nobles use a 3.0L duratec with some stronger internals thrown in to live longer. how much longer seems to be highly dependent on whether or not the car sees much track time... at least with the 'as shipped' spec engine. we're working on an engine swap kit for them so as to not be quite as blowy uppy come trackdays.

pres589 wrote: I wonder about just hanging the blower on a normal 2.5 and leaving the 2.3 and weirdo cams behind.

Won't really work. Motors arent real similar. And the suoercharger is a liability, not a boon. Hideously expensiveto replace.

singleslammer wrote: I would imagine the 2.3 is forged.

Nope. It's really not a good motor.

My guess is that what would happen if you put normal cams in it would be that it would blow up in short order. Unless you found a way to drastically reduce the boost the supercharger would put out.

Swank Force One wrote:

singleslammer wrote: I would imagine the 2.3 is forged.

Nope. It's really not a good motor. My guess is that what would happen if you put normal cams in it would be that it would blow up in short order. Unless you found a way to drastically reduce the boost the supercharger would put out.

Source? I am looking for a tech article I found on these motors and I can not find it.

I did some research on this. The heads and intake are differenough that they don't really swap. The v is different. I think the cams swap though. I was looking into it for an xp build so I don't know about the pistons.

Swank Force One wrote:

singleslammer wrote: I would imagine the 2.3 is forged.

Nope. It's really not a good motor. My guess is that what would happen if you put normal cams in it would be that it would blow up in short order. Unless you found a way to drastically reduce the boost the supercharger would put out.

You could not run the motor with normal cams and keep everything else stock. The motor runs a constant pressurized intake tract to counter the intake valve being open for the first 20% of the compression stroke. This reduces the drag on the motor by caused by the pumping action of the motor by more than 30%. However the force needed to spin the supercharger reduces this and thus you only see a moderate gain in effincy but Still impressive. Think about it the millennia S is not a small light car. It had a curb weigh of about 3500 lbs. And yet it still moved along pretty well and got economy numbers of about 30 MPG.

As for the motors being "good". That is subject to debate. In stock form compared to modern motors that is a fair statement. But if you strip away all the stuff that made it a miller cycle it is my understanding that you have quite a marvel of engineering the basic long block is a very good piece. The only thing I read that is a problem is if you don't keep up with the oil changes you get oil return problems in the head and or oil starvation to the valve train. I have not see anywhere where these motors blow up, spin bearings or fail catastrophically.

I thought we had discussed this motor before.

http://grassrootsmotorsports.com/forum/grm/mazda-millenia-s-turbo/18650/page1/

I am going to have to get to my local junk yard and see if they have any motors in the shelf. I really want to take a look at one of these. The block was a split block design similar to F1 motors making the bottom end much more stable compared to comparable motors. I also for some reason think that they are all aluminum motors as well (I can not find where I think I read this)

My thought is to strip the motor of all the external plumbing and what not. Ditch the stock supercharger. Replace the cams with ones that have been re ground to eliminate the intake valve overlap with the compression stroke (it stays open for the first 20% of the compression stroke). Then put it back together with either a M62 or possibly the turbo from the mazda 3 that uses the 2.3L turbo. (Since I have both on the shelf from other projects.) Run about 6-8 LBS of boost and have fun.

What I don't know is how the motor is balanced and if there is a junkyard swap that would allow it to run a manual trans (flywheel and clutch are my unknown at the moment) I also don't know what would be required to mount it in a RWD application.

And I have even asked the same question before. LOL

I hope when the site gets a revamp that they can sort out the ability to search.

http://grassrootsmotorsports.com/forum/grm/rwd-with-miller-cycle-motor-aka-millenia-s-motor/7428/page1/ More good info in this thread that I started back in 09.

I really can't stress that every advantage this motor has fundamentally is already available in the bigger KL already enough.

The Milly rods are stronger but still cast. Off the shelf K1 rods for the KL are stronger. The KL is still the 3 piece block. And you don't have to do a bunch of custom work to make it run like a normal motor. And the guesswork to run a turbo or supercharger has already been worked out.

I'm also not sure the cams swap over. Never seen it done and the head dimensions are not identical.

I was not going to swap cams just have the intake ones re ground to get rid of the overlap with the start of the compression cycle.