NC 2.5l engine swaps ?

[keito]

Just weld up the rear doors in the Mazda 3, cut the roof off and voila......you've ruined a Mazda 3.

Hah!

[ozace]

After a couple of thousand k's since the swap some thoughts.
The engine is not as smooth at idle as the stock 2lt. Not bothering me but I do notice a difference.
the sound is now deeper, more muscular than before. Again I am enjoying it.
The extra torque is amazing, I haven't hit the redline yet as all the go I use on the road is now down around 4.5 to 5k.

Heavy duty clutch has a very different feel to stock, not bad, not good just different. Pedal is a little heavier

Upgraded sway bars keep the car flatter, again a different feel to before

The 4.1 diff hasn't caused an issue, just spend my time a gear higher than i used to, combination of more torque, more power and changed gear ratio.
6th gear is now usable on a freeway without the need to drop down to overtake.

I haven't noticed a change in fuel consumption and there have been no change in the heat.

DSC and TC get a bloody good workout now

Tein edfc active pro with gps has only been in for a few days. So far i am loving it. Set to auto mode it starts off very soft and comfy , as the G's and/or speed rise it firms up.

next is lower seat rail in the hope i can fit with a helmet on and roof up

[ozace]

east bear lowering seat rail in. So very close to fitting with helmet and roof up. I think its time to try different helmets now.

[Custardtart]

Thanks for the update.

Is the 4.1 ok? I’ve been thinking of this but was concerned it might be a big jump from the 3.7?

[ozace]

The 4.1 is great on the road, the car is zippy and I dont need to drop down a gear or two to acceleration. Combination of extra torque and diff ratio I am sure.

The drive back from Sydney had me 500rpm higher in 6th but it wasn't annoying with the added plus of not needed to drop down to go over a hill. I am very pleased I did it

[Regie]

Thanks for the update.

Is the 4.1 ok? I’ve been thinking of this but was concerned it might be a big jump from the 3.7?

4.1 is one of the best things you can do to a NC. Do it!

[StanTheMan]

So the lower diff ratio is all about fuel economy?

Sent from my SM-G935F using Tapatalk

[ozace]

So the lower diff ratio is all about fuel economy?

Sent from my SM-G935F using Tapatalk

The US got 4.1 and slightly different gearbox ratios, better acceleration than we got.
The AU ratio may have been fine with the 2.5 but I am enjoying the extra ZOom Zoom all round.
Real world economy hasn't changed enough for me to notice

[Regie]

if you care about economy, you're driving the wrong type of car

[Spac]

would these go into an NA chasis?

Probably, google shows a couple at least.

Biggest issue is that unlike a B6 to BP swap where a whole lot stays lines up, with the MZR pretty much nothing does, even stuff as simple as exhaust and intake being on opposite sides to the B series.


If you wanted a 2 litre (without boring out a BP) it's probably a bit simpler to go for an F series engine, probably the FE-DOHC (FE3 colloquially)
Intake/exhaust on same sides, MX5 gearbox I believe can fit if you use a B series ute, or E series Van bellhousing (or 929, but they were auto only)

But, you're still stuck with custom sump, and probably having to do something about the subframe.
Plus, the F engines are physically taller than a B engine, so you'll probably need to have a small bonnet hump or something to clear.

Lots of HB 929s were manual.

[hks_kansei]

Ahh, didn't realise.

Only ever seen autos, and assumed the HB was like the HC onwards on being auto only.

[rascal]

The drive back from Sydney had me 500rpm higher in 6th but it wasn't annoying with the added plus of not needed to drop down to go over a hill. I am very pleased I did it

How fast where you going on the drive back??? 3.7 to 4.1 is just over 10% difference.
For 10% to be 500 rpm then you were doing almost 5000rpm... in sixth!!

[ozace]

At 110km in 6th, I think I was up around 3500rpm ish

[Custardtart]

You’ve inspired me to get a 4.1, pick it up in a couple of weeks

[ozace]

I have noticed the goodwin header is very tight fit for a rhd car. Every now and again it runs the steering bits. I am going to try a racing beat system soon.