by Roman | November 22, 2006 5:27 am
Okay, so this seems to come up every now and then, usually people wanting to know if they can fit an Altezza engine into their MR2.
A few people have fitted FWD engines in a RWD setup, which is easier on some regards, but has it’s own set of problems too.
Okay, so what are the main differences between the two engines, and how/why are relevant to wedging a dual VVTI engine into that MR2 engine bay?
(Note… any time I say ‘fwd’, I mean ‘transverse’, as in east west configuration. Any time I say ‘RWD’ I mean north/south)
engine power/benefits
Firstly, I think that this is the most important thing to consider here.
To put a RWD engine into a FWD car, you need FWD beams bits anyway (Which arent cheap/easy to get!), will have a lot harder time with wiring etc, will be hugely more expensive. For what gains? A measly 10hp, and exhaust side VVTI which is more trouble than it’s worth.
Adjusting the cam profile on the exhaust side has a negligible effect on power output… It’s primary function is to increase fuel efficiency.
So what other benefits does the RWD engine get, that make it worth all of the hassle?
It’s got 11.5:1 compression; FWD engine has 11:1
The Altezza dual VVTI engine has Titanium valves on the intake side, sodium filled valves on the exhaust side.
The FWD engine has the sodium cooled exhaust valves, but not the titanium valves on the intake side.
The cam profiles are more than likely different too, but I cant confirm that.
Higher rev limit: RWD engine goes to 7800, FWD goes to 7400.
So the million dollar question still remains: Are these features worth all of the extra struggle and pain, compared to fitting a FWD engine instead?
Not in my opinion, but some disagree.
I’m doing exactly the opposite to this; fitting a FWD engine into a RWD setup.
I’d rather have the RWD engine; but I’ve already got a rebuilt redtop sitting in the garage that’s looking for a home, and the RWD engines are still expensive and hard to come by. It’s far more economical, for me to convert the FWD engine to RWD instead.
Which is how I’ve come across most of this information, as I need to know which RWD bits I need to buy/steal/make/etc.
At this point, I’d just like to say a huge thanks to Glenn AKA CelicaRA45, who has been a huge help, and has shared with me the majority of this information.
Okay, so here’s the basic differences that you need to know about:
Sump/dipstick
On the Altezza engine, the sump is waaay at the front of the engine, to clear the RWD cross member. It’s also on the wrong angle, as the RWD engine stands upright, instead of leaned over. To make this work in a transverse setup, you’ll need a FWD sump, dipstick, and oil pickup. These bolt straight on either engine, so no problems there.
Intake manifold.
A RWD intake manifold faces away from the engine; the FWD one wraps over the top.
A FWD intake manifold on a RWD car will want to stick through the top of the bonnet;
A RWD manifold on a FWD car will want to stick through the firewall. (Into the boot on the MR2)
It’s also worth noting, that the throttle body is on the other end of the plenum… The FWD one faces the gearbox, and will basically be touching the firewall in a RWD setup, and the RWD one in a FWD setup will point into the right rear corner of the engine bay, (Or more to the point, into the boot!) Where it isnt really practical to have an air intake setup.
So you really need the correct manifold for either situation.
They are interchangable, but you’ll definitely want to run the throttle body to suit the ECU that you’re using, if factory. You’ll need to make custom mounts to fit the altezza throttle body onto the FWD intake manifold, or vice versa.
Exhaust Manifold
The FWD exhaust manifold faces directly down, and goes under the sump, and out the back. Whereas the RWD one runs down the length of the engine, and exits at the bottom rear. Obviously not suitable for a FWD setup.
The redtop exhaust manifold will bolt directly onto an Altezza engine, or vice versa.
Cam covers, RHS/front engine mount
The Altezza engine only uses two engine mounts, which are on either side of the engine block. In a FWD setup, the only mount that’s on the engine is at the ‘front’. I dont know for sure if the FWD engine mount will fit to the Altezza block, from memory I believe that the Altezza cam belt setup interferes with the FWD mount position. I believe that using the FWD cam belt tensioner, and a few other FWD bits alleviates this problem, but I cant comment for sure.
Also, the RWD cam belt cover sticks a considerable distance further away from the engine block than the FWD one, and wont physically fit inside the engine bay. It’s often said that the exhaust side VVTI clashes with the strut tower, this isnt true. The exhaust side VVTI wheel is strangely huge, but it is actually clear of the tower. It’s the cam belt cover that’s bigger, on account of the exhaust side VVTI.
The intake side VVTI wheel appears identical to the FWD equivilent, and therefore shouldnt be problematic to fit.
From personal experience, my cam belt cover is HARD up against the strut tower running a FWD engine, so I know that you’d have no chance of fitting a RWD cam belt cover on it. I’d imagine that using a FWD cover and notching the exhaust side for the oversized wheel would be the way to go.
Running a FWD in RWD configuration gives no problems here, using the FWD covers etc is fine.
Water lines/galleries/etc
The FWD rear water outlet is different between the MR2 and Celica. The MR2 one has two hoses on it, one for the radiator hose to the radiator, and one for the filler cap. The Celica one obviously only needs one hose, as the filler is on the radiator itself.
I’ve studied the RWD water lines a little so far, and I’d say that you wont have much of a problem running them in a FWD configuration with some creative running of waterlines.
If you want to run the FWD waterlines, you need to run a FWD headgasket. The Altezza gasket has the water outlet at the other end of the engine, so it has different holes in it for the galleries.
Conversely, you need to run a RWD gasket to suit the RWD water outlet etc.
It’s a bit harder the other way around though, as the FWD outlet wants to stick through your firewall.
It’s also worth noting, that despite what I thought earlier, the RWD engine only has one oil gallery from the block through to the head for VVTI, despite having dual VVTI. It’s in the same place as the FWD one, but is a larger diameter. If you wanted to run the FWD head gasket on the RWD engine, you’d want to oversize the hole on the gasket there, or at least check it to see what size it is.
I cant see why you couldnt run a dual VVTI head on the FWD engine, however you’d need a stand alone ECU to do it.
Oil drain from the head
The Altezza engine runs an oil drain down from the head, that the FWD engine doesnt have.
The FWD engine has something similar, but it’s at the top of the rocker cover; the RWD one is down lower.
The FWD engine obviously uses gravity to drain the oil back out of the head, as it’s on a lean.
If you wish to use a FWD engine in a RWD setup, this is potentially important. You could get oil drain back issues, where the head fills up with oil, and the oil pickup sucks dry, which usually results in your bearings giving up.
If you use the Altezza rear water outlet, (Which has the oil drain integrated) and tap a hole into the FWD head to suit, you can run this oil return to the sump.
The FWD engine has a big pipe running from the rear of the rocker cover back down to the sump, it leads to the same place in the sump as the RWD one.
You’d want to block this off, if you’re using the RWD oil drainback.
Wiring issues
Well… I cant comment too much here, as I have never attempted this.
All I can say, is that someone got as far as getting the engine in with all of the FWD bits needed, and ground to a halt when they got to the wiring required.
One thing I can say for sure, is that running the Altezza dash unit is necessary. The FWD beams computer outputs the signal to the dash unit in the traditional way…
One wire for water temperature, one wire for speedo, one wire for tacho, etc.
However the Altezza system runs differently. It only runs one wire to the dash for all of these, called ‘MMC’ or ‘MMX’ if I recall.
I cant remember what it stands for, but basically it sends this one signal to the dash with all of the information imbedded in it; this signal is interpreted by the circuitry in the altezza dash; and sent to the appropriate gauges etc.
I dont know if it’s possible to split the MMX signal back into traditional ones, you could probably get the factory MR2 dash working, using the circuitry from the Altezza dash as the inputs. I’m not sure about that one.
I’ll be trying to wire an Automatic Celica loom into my Carina, which since it currently has a carby engine, doesnt have much wiring to integrate to at all. So it should be an interesting (read: nightmarish) experience.
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