Forced induction fuel economy and durability

[Chris71]

Hi,

Out of interest, what sort of MPG figures do turbo'd or supercharged MX5s return and do they require much more looking after than NA cars?

I appreciate both will vary on how far you've taken the tuning to a degree, but principally interested in fairly mild states of tune (up to about 200hp).

Chris

[Chris71]

So, two questions:

Is there a big difference between supercharging and turbocharging from an economy point of view?
Does the 6 speed 'box in the later cars make a huge difference (not strictly FI, but curious...)?

[Chris71]

Does sound tempting. I'm pipedreaming a little here, but if you'll indulge me, what do you reckon the best donor car and the best form of forced induction would be for a driveable, relatively economical daily driver running 160-200hp?

[Chris71]

MX-5 Lazza said:

Filled up today. 260 miles on 45 litres so pretty much 26mpg. Not bad considering I've been "testing" my new Hankook RS2s

Your car is running over 200bhp too isn't it? So, that's quite an impressive figure for a car with (realistically) more power than a base spec Griffith.

Gearbox comments are interesting. When I had my RS (with a lowered FDR) everybody said it would be screaming on the motorway, but it wasn't too bad - certainly pailed in significance to the windnoise from the hood! One of the best things about that car was its beautifully precise gear shift, so it's interesting to hear that the 6 speed isn't quite as sharp.

[Chris71]

Another question out of interest - with only 200cc between them and as much boost as you dare is there any preference between the 1.6 and 1.8 for forced induction?

[Chris71]

MX-5 Lazza said:

GravelBen said:

I seem to recall reading somewhere that its easier to turbo the 1.6 but easier to supercharge the 1.8, any merit in that?

With the 1.6 just about all of the turbo kits are available but only the M45 SC kit will fit (I think the MP62 1.6 kit is about to be released).
With the 1.8 most of the turbo kits are available but with SC you have a choice of M45 or MP62.

One isn't any easier than the other, it's just the availability of parts/kits.

Something to keep in mind though is that the 1.8 comes with a bigger clutch & flywheel and bigger brakes, both of which are desirable. They can both be fitted to a 1.6 though. The 1.8 LSD (Torsen) is stronger than the 1.6 (viscous).

Ah, interesting. So if you could pick either as a donor it'd probably be a 1.8? Must admit I've always wondered what the split between Torsen and viscous LSDs was. I'm told the viscous ones can unlock after a while, but the Torsen ones don't?