OUR CARS The Total MX-5 fleet
We’re as passionate about MX-5S as you are because, as you can read on the following pages, we’re owners, too. Each issue Total MX-5 brings you the highs and occasional lows of our various ownership experiences
Editor Fraser tests new Davefab induction kit on the rollers. Bennett tarts up his new mk2 and Simon Fox fits an ECU
AT BLOOMIN’ LAST
After many months – maybe close to a year – I’ve finally gotten around to fitting the Davefab cold air induction kit. When I say ‘I have’, of course what I really mean is that Michael Cleverley has. He assures me that I could probably have done the work myself, despite my mechanical ineptitude, but the prospect of cutting a hole through the bulkhead, which the kit requires, simply confirmed to me that this was a job best left to the professionals.
Just to recap the point of a cold air induction kit of this nature: it pulls cold air from the windscreen side of the bulkhead, which is completely separated from the heat of the engine bay. The cooler your intake air, the greater its density, so there’s more oxygen going into the combustion chambers, helping create extra power. Hopefully.
Davefab supplies its cold air induction kit not only with comprehensive instructions, but also a printed paper template for cutting the aforementioned breach in the bulkhead, complete with positioning holes, through which you insert the washer bottle’s two fixing bolts on the bulkhead to ensure it’s in precisely the correct position.
Before any of that could happen, though, there was the existing airbox and its associated plastic pipework to remove, as well as the washer bottle, which was sitting right where the hole needed to be. My earlier observation that some things are best left to the pros was borne out by the speed at which Michael dived in, undid bolts and clips, pulled out piping, and left exposed a considerable chunk of engine bay. Left to my own devices I would still be fiddling around in the dark, trying to discover what it was doggedly holding a big bit of plastic in place.
With the assistance of the paper template Michael scribed the appropriate diameter circle into the metal of the bulkhead, at which point he realised that he didn’t have a 64mm diameter hole saw on the premises. Ever one to rise to a challenge, he set about cutting the hole ‘the old fashioned way’. That is, by using a regular metal drill bit to cut closely spaced holes all the way around the diameter of the scribed circle, then using a punch to chisel through the
remaining metal between the holes, then finally perfecting the circle and smoothing away rough edges with a small abrasive disc. It might have taken longer than doing it with a hole saw, but I get the feeling that Michael enjoys the more hands-on, manual approach.
The Davefab airbox is a curious-looking thing, but beautifully welded and finished, and crowned by a badge that’s etched onto a little metal plate that’s copper pop-riveted to the top of the device. Getting its cylindrical inlet pipe to poke far enough through the bulkhead
(in the direction of the base of the windscreen) so that Michael could affix its alloy bellmouth collar on the other side of the bulkhead was trickier than we thought it would be.
Enlarging the main hole slightly gave us a little more wiggle room, but still an insufficient length of protruding pipe to attach the bellmouth to. Eventually Michael had the brainwave of elongating one of the bolt holes on the box’s fixing plate, allowing the whole thing to shuffle backwards a couple of millimetres, which did the trick. What you must remember to do, though, before bolting everything firmly in place, is pull the airbox back out slightly so that you can open it and insert the air filter.
With everything in place, attached, and bolted securely, Michael turned his attention to the Davefab scuttle-mounted replacement washer bottle. It’s another neat piece of steel fabrication and is supplied with everything required to get water to and from it, plus the relevant electrical connections. Even Michael was impressed, especially with the heat-shrink plastic sleeves for protecting the electrical connectors. He did point out, though, that for all the bottle’s stylish looks, it doesn’t actually hold much washer fluid, but then I don’t ever use much washer fluid.
Prior to getting the Davefab gear fitted, I’d been back to see Sam and Matt at nearby Hybrid Tune to get ‘before’ power and torque readings. In fact, I’d first
gone there last August, on a day that was genuinely hot, but Sam insisted that what I really must have was winter temperature ‘before’ readings. And back on a nippy day in February my MX-5 achieved a maximum power figure of 121.8bhp with the bonnet down, and 123.4bhp with it up for greater cooling. The torque figures were 111.9lb ft and 114lb ft respectively, both at just over 5000rpm.
Annoyingly there was quite a gap between Michael fitting the Davefab kit and me being able to get back to Hybrid Tune: I really wanted to know those ‘after’ figures. Particularly as my MX-5 now sounds awesome, all deep-throated and old school twin-cammy. Rorty you’d have called it back in the day. You don’t get the full audio theatrics until the tacho needle passes 3000rpm, but then it builds steadily in volume and aggressiveness, turning almost to a shriek as you reach 7000rpm and need another gear. Even if there were no power increase from the kit, this evocative soundtrack should ensure you’ve no regrets about splashing out on it. And this is in conjunction with just a standard mk1 exhaust.
It’s all very much subjective, I know, but a good induction sound can transform what you feel about your car and affects the way you drive it. I’m now much more inclined to rev mine out to near the limiter in every gear, and I’m driving it quicker point-to-point, too, a fact I know not from keeping an eagle eye on the speedo, but because I’m having to brake far harder on the approach to familiar corners. The MX-5 is more satisfying to drive, sportier.
As a consequence of the disruption caused by the Beast from the East, Hybrid had a spare slot to put the MX-5 back on the rollers once the snow had cleared. And the results were interesting. The Davefab kit produced 126.7bhp at 6500rpm regardless of whether the bonnet was open or closed, proving the value of sourcing your intake air from outside the engine bay. Compare that with the 121.8bhp achieved bonnet down with the standard induction setup: Sam, however, reckons the comparison should be against the bonnet up figure of 125.8bhp from the factoryspec induction system, reasoning that an engine generates more heat on a rolling road than it would on the open road, and therefore is ‘owed’ as much extra cooling as it can get.
Now I know Sam’s the expert – and I’m sure many of you will share his opinion – but I’m sticking with the 4.9bhp increase from the bonnet down scenario. Makes me feel happier. Frankly, though, the kit’s worth it for the noise it makes alone.
Thanks to: Sam Weller and Matt Willgoss at Hybrid Tune (07552 238737), and Michael Cleverley of Cleverely Repaired Cars (01379 384046).
Standard induction apparatus seems huge once you’ve removed it from the engine bay
Davefab cold air induction kit draws cool air from the other side of the bulkead, away from the heat of the bay
Paper template for hole’s position
…and get chiselling
No hole saw? Start drilling…
Editor Fraser’s mk1 gets the rolling road treatment courtesy of the lovely chaps at Hybrid Tune: owner Sam Weller is the man behind the wheel
The Beast from the East couldn’t stop Fraser’s mk1 from travelling