Economic RWD engine swap

[diurno]

I know it almost sounds like an oxymoron for a kit car, but I’m looking at alternatives to my current NB MX5 1.8L engine fitted in my MGB GT.

It has done great over the years but it has now unfortunately developed an oil leak from the bottom seam and rocker cover + the clutch needs changing. I have therefore been considering an engine swap as a nice summer project.

I’m looking for a petrol engine that is economical and offers a bit more mpg than the NB. Strangely enough I drive the car around 10k miles a year, and will more than likely continue for the next few years. I’ve been looking at the NC MX5 engines as that would be an easy swap. But does it really behave any better mpg wise? Does anyone have any other suggestions for other engines that can be used as RWD + economic?
Thought about the zetec and Duratec? Are they any better?

P.S. yes I know I should just get a cheap electric or hybrid or diesel daily, but I don’t really want that as I enjoy driving the MG too much and just spent the last 4 years restoring it from ground up

Thanks!

[CanAm]

Frontline do a conversion using the 1800 K-series.

[Equus]

diurno said:

Thought about the zetec and Duratec? Are they any better?

The MZR engine in the Mazda MX5 NC is a Duratec, to all intents and purposes (albeit the later versions of the MZR come with a forged crank as standard).

The Zetec is nowhere near as good as the Duratec.

[diurno]

Do they do any better mpg wise? Both the K series and MZR engine?

[Equus]

I don't know, because I haven't got the graphs of their specific fuel consumptions. It's no good trying to compare their consumption in donor cars, 'cos there are too many variables that would affect the outcome.

The Duratec/MZR is the most modern of the units, so it's likely to be the most fuel efficient, but that's about all you can say.


ETA: If you're fitting it to an MGB with the MG's standard rear axle (3.9:1?), by far the biggest factor on fuel consumption will be gearing.

Edited by Equus on Monday 18th June 15:11

[TheSurveyor]

Watching this with interest as an avid MGB modifier.

Rally boys in their escorts favour a Zetec or Duratec which can be bought as a warrantied crate engine.

A Toyota 4AGE can be made to produce < 150 BHP and with a few grand in excess of 200.

What characteristics are you after?

[diurno]

Very good point regarding the axle, and I am currently considering swapping the rear axle to a different ratio - perhaps 3.3:1 from the Sierra/Granada diffs.

About the Duratec/MZR good suggestions, and I’d assume the Mazda option may be easier to do a direct swap as the prop should be the same and mounting points fairly similar.

Not thought about the Toyota engine but will investigate that.
Mainly looking for reliability and economy as I drive the car on a daily basis. Even thought about the ecoboost engines, but there doesn’t seem to be many kits/ECUs available for them yet which would make the whole thing very expensive

[killerferret666]

The MR2 / celica engine 3s-GE or 3S-GTE. Depending on power and space you have (GTE is turbo). I think the non turbo came in varying powers from about 140bhp - 200bhp

In terms of electrics. I found the engine loom / rear loom to its fusebox had everything required past that point and just ignition, battery and alternator wires was required to get it running (5 in total).

[TheSurveyor]

Just for my information more than anything, is there a good website to read up on the electrical set up for aftermarket engines anywhere?

I know the likes of Omex has to be used to run the thing, but the rest of the electrics is a mystery to me.

[CrutyRammers]

Well they vary, but in principle the ECU takes inputs from various sensors (airflow/pressure, crank position, cam position, water temperature) and has outputs to the injectors and spark plugs. Sometimes a couple of ancilliaries like the fan as well. Not really a lot more to it than that for aftermarket stuff - though even that quickly mounts up to being a lot of wires! Emerald's website has the manuals for download which give the full details, I can't remember if OMEX do the same.

[diurno]

Think I might try get a MK3.5 MX5 engine MZR 2.0 and fit an Omex ITB kit?

Might be interesting? Hopefully still mpg friendly

[Turn7]

Equus said:

I don't know, because I haven't got the graphs of their specific fuel consumptions. It's no good trying to compare their consumption in donor cars, 'cos there are too many variables that would affect the outcome.

The Duratec/MZR is the most modern of the units, so it's likely to be the most fuel efficient, but that's about all you can say.


ETA: If you're fitting it to an MGB with the MG's standard rear axle (3.9:1?), by far the biggest factor on fuel consumption will be gearing.

Edited by Equus on Monday 18th June 15:11

Wont a Duratech need standalone management ?

Guessing current setup is std Mazda ?

[diurno]

Current setup is a 1.8L NB engine + Mazda gearbox with MS2

[dmulally]

There are so many cool after market toys you can do with the NB engine (ITB's, turbo etc) but if your heart isn't in it then no point.

I drove an S2000 locost a mate built and that was rather fun. Mine has a 4agze and is much more fun than my old 4age. It had no torque so pulling out to overtake in a headwind was a bit of a pain on the highway.

[Equus]

dmulally said:

There are so many cool after market toys you can do with the NB engine (ITB's, turbo etc) ...

Ditto the Duratec, of course: 300+ bhp superhcarged is straighforward, and Caterhams use it in nat. asp. form up to 260bhp.

Not likely to improve your fuel consumption much, though.

[the_stoat]

If you are doing this from a cost perspective will an engine swap really add up. By the time you consider the cost to change I would doubt a minor change in MPG would make up for it. For example cost up a rear wheel drive sump for a Zetec.

These engines are so cheap they are nearly a consumable item. Additionally they seem to like high revs too. I have driven several Zetec kit cars and they all seem to just give up above 5.5k rpm which spoils things when trying to have a bit of fun.

[Mr2Mike]

Replacing the NB engine with something of similar power and displacement isn't going to buy you anything significant in terms of fuel economy, assuming that you don't want anything new and complex (e.g. direct injection). Definitely not a good justification for the time and expense required to fit a completely different engine.

[aka_kerrly]

Have you considered rebuilding the existing mx5 lump and swapping to ITBs combined with a 6 speed gearbox setup. That could help balance performance increases and economy.

[Tony427]

Turn it into a modernish MGB V8.

I bet a Toyota 1UZFE would fit snuggly in there.

Would probably get high 20's mpg mated to a manual box though the automatic comes free with the donor Lexus LS400.


Cheers,

Tony

[spyder dryver]

killerferret666 said:

The MR2 / celica engine 3s-GE or 3S-GTE. Depending on power and space you have (GTE is turbo). I think the non turbo came in varying powers from about 140bhp - 200bhp

In terms of electrics. I found the engine loom / rear loom to its fusebox had everything required past that point and just ignition, battery and alternator wires was required to get it running (5 in total).

Hi killerferret! I'm curious as to why you have suggested the 3SGE for a RWD conversion. Have you done one? I've done this install in my car, initially with a modified T50 box and latterly with a modded IS200 AJ6 6 speed.
Getting it under an MX5 bonnet would need ITBs and wouldn't achieve any MPG benefit in any case.
I'm presently building a new engine for my car. Higher comp, better cams, etc. Its not the easiest engine to convert to RWD but I enjoy a challenge.
There is, of course, the RWD 3SGE VVTi engine from the Altezza which comes with a 6 speed box but it is too tall for my car and too tall for an MX5 too, I suspect.