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Rolling-road tuning session

Had a great time yesterday morning watching someone clever tune my car on a rolling road. I spent quite a lot of time last year building a new engine for my 1973 MGBGT. Obviously not 'new' new, but rebored, reground, ported, balanced, timed and generally built to be better than new in every way I could reasonably manage. With it finally back in the car I was naturally hoping for about 2000bhp from my little, cast-iron, pushrod one-point-eight. Unfortunately what I ended up with felt like somewhere south of 50bhp, and no amount of tweaking seemed to help. As always, my Dad came to the rescue, and offered to treat me to a couple of hours with Alan Jeffery in Plymouth, trying to work out why my new engine wasn't as powerful as the knackered one I'd replaced.

The first thing Alan spotted as soon as the initial power run had been done (48bhp at the wheels!) was that the distributor was behaving very oddly indeed. It turned out that the "extremely good value" electronic distributor I had purchased a while ago from Powerspark as in fact just cheap, and not very well made, having actually disassembled itself internally. With the connecting rod that links the vacuum advance to the timing adjuster tapped back into place with a bit of Loctite, he was able to do some proper power runs and set the timing to be correct at 4000rpm. He then moved on to the mixture, and the needles. One thing I learned was that the mixture adjustment on the carbs is not actually that important in terms of getting everything right when compared to the needles themselves. Having discovered that the AAA profile needles I was using were far too rich, he dug out some replacements in a different profile, and did another run. These too were deemed not quite right, and were 'adjusted' with a fine file to alter the profile to better suit my engine. I suspect this is the kind of thing you can only do with a great many years of experience, and it was impressive that it seemed to do the trick, taking the final figure just over the 100bhp mark.

I was told that standard MGBs tend to make about 87bhp, so although I was probably hoping for more, that's not a bad improvement when you consider that the engine is only a rebore bigger than normal. More impressive was the torque, coming in at 125lbft at 3100rpm. That's more than you get from a modern Ford Focus of the same engine size, which bearing in mind that this is an engine first built in the 1950s, and of a fairly agricultural design at that, isn't too shabby at all. Here is the graph from the final power run.

I've only actually done about 3000 miles on this engine so far, so I think a return visit may be in order once things have properly loosened up a bit! I'm sure the 2000bhp I was hoping for is in there somewhere...

Categories: Cars, Projects

Tags: engineering, mgb

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Are modern cars too fast?

I love cars. And I love fast, too. Fast and cars, together, in harmony. LIke 'hot' and 'chocolate'. LOVELY. But there's a problem: modern cars are just too fast. Too fast to enjoy in (relative) safety, too fast to thrill at sane speeds, and too fast for the powers that be not to notice.

There's a terrific video on the Autocar website right now - a triple test of the new Mercedes A45 AMG, the BMW M135i, and the Golf GTi. All fabulously fast and capable cars. You can see just how fast by looking at the speedo needle in the footage - at several points Steve Sutcliffe hits three figures, apparently without drama, and well within the limits of the car. A few people pointed this out in the comments. Now I'd probably love to do 120mph in a car that capable over a lovely Welsh B-road. However (aside from the fact that that trio of cars is probably worth more than my house), I'm not sure I ever should, and there's a point to be made here about how fast modern cars are.

For us mere mortals with normal reaction times (Steve is a former racing driver), a car that makes it a doddle to hit 3-figures on a B-road is probably asking for trouble. The best brakes in the world won't make up for how long it takes most of us to spot the sheep in the road and move our foot over to the brake pedal.

Basically, there's a lot to be said for cars that make 60mph feel exciting. It bothers me a little that, should I ever encounter one of those cars being driven at speed over the Black Mountains, the chances are it won't be being driven by an ex-racing driver, or a motoring hack with 30 years fast driving under his belt. The chances are it'll be driven by a moron with lots of money and no talent.

The last such incident I can recall was a brand new Focus ST coming the other way over a bumpy B-road. He went too fast into a bend, seemed to lock a front wheel momentarily, understeered, and only at the last minute swerved to avoid hitting myself, my wife and our daughter head-on in our 40 year old car. As I say: more money than talent.

I really do dislike the relentless encroachment of ever-lower speed limits on my driving pleasure. I don't want standard 50mph limits on B-roads. I don't want speed cameras everywhere. But while there is a market for this type of car, you know that the only way the authorities are going to respond is with lower limits and SPECS cameras as far as the eye can see.

If you're at all into cars you probably already know the story of how our national 70mph limit came into being. Although the official reason was a spate of incidents that had recently occurred in poor driving conditions, it is widely believed that a major cause for alarm within the government was when AC tested the Cobra on the M1, and is alleged to have hit 180mph.

The point I am inelegantly attempting to make here is that, when it's so easy to buy and own a car that can casually do twice the speed limit on a B-road, bad things will happen, and sooner or later the authorities will have to respond.

Categories: Cars, Comment

Tags: speed

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Automotive fatties and a hybrid I actually want

One of my favourite automotive whinges is the seemingly ever-increasing size and weight of new cars. With a few notable exceptions (the Mazda 2 and Chevrolet Corvette spring to mind), each new car is always slightly bigger and slightly heavier than the car it replaces. And as modern cars have become more similar in pace, construction and appearance, the differentiating factors (outside of brand image) have focussed almost exclusively on comfort, space, safety and refinement. I'm not necessarily talking about high-end stuff here: that tends to play by different rules. I'm talking about everything from a Ford Ka up to a BMW 5 Series.

Economies of scale as well as the implementation of strict safety legislation seem to have led to a sort of convergence in car design, and meant that manufacturers are forced to compete on what was once the minutiae of the road test review. An average group test of new cars in the motoring press today will often conclude one car superior to another thanks to a few more litres of boot space, a slightly better ride, and slightly less noise on the motorway. This sort of thing is unavoidable: manufacturers are competing within quite strictly defined boundaries: must seat five, must hit 62mph in about 10 seconds, must get 4+ NCAP stars and so on. The problem is that something has to give, and what gives is weight and size. If what it takes for your new hatch to be seen as better than the opposition is another couple of centimetres of legroom, a bit more sound-deadening, or a few more electric toys, then that's what it will undoubtedly get. And so the weight-gain continues. The consumer only validates these choices by discriminating on the basis of size and motorway quietness. If we simply accepted that we could live with less of the heavy sound-deadening, and rarely needed to carry a wardrobe home in the boot, the current car market would be a very different place indeed.

The problem manufacturers are increasingly facing is that they are now judged on the economy of their vehicles too, and weight is the enemy of economy. Pretty much any very light car, with sensible gearing and an smallish engine designed after 1960 will do 40+ miles to the gallon. Speaking as one who has owned several ropey Minis, I can promise that this is true. And they aren't economical because an overhead-valve, cast-iron A-series engine fueled by carburettors is especially efficient or advanced (it isn't), but because they only weigh about three quarters of a tonne. Fit one with a modern fuel-injected lump and the economy figures can be hilarious (in a good way).

What annoys me about the status quo is that currently economy is judged by an unrealistic government test that in no way replicates real-world conditions, and in which weight has little, if any, effect at all. This test (conducted on a rolling road), is what manufacturers are designing their cars to excel in. The inevitable result is cars being sold with staggering official economy figures, and absolutely no chance of reaching them in the real world. Autocar's recent first drive of the Fiat 500 TwinAir resulted in a distinctly unimpressive overall economy reading of 37mpg. Compare this to the official combined figure of 69mpg, and it's clear that the official economy figures are nothing if not inaccurate. Likewise a recent Auto Express group test of city cars revealed vehicles that claimed to be capable of mid-50's economy on the combined cycle, but in reality on returned low-30s.

What's more, hybrids - cars who's soleraison d'etreis to be economical - are subject to the same misleading tests, and so present similarly skewed results.

I find it disappointing that they all seem to take an engineering approach similar to the Bugatti Veyron - set a goal and then add ingredients until you get there. Thus you end up with a car like the Prius, which sports a regular petrol engine, an electric motor, and a heavy pack of batteries, not to mention all the regular safety and comfort features that customers have apparently come to expect. And therein lies the problem:everythinghas become an immovable feast. Which means you end up with a car that, whilst still only seating 4 (5 at a push), is 4.5 metres long and weights nearly a tonne and a half, and manages fuel economy figures likely to be no better in real life than a diesel engined car of similar space and performance.

There's no doubt that the Prius is an incredibly clever bit of engineering, but the current belief that everything you find in a modern car absolutely has to be there is a fallacy. To paraphrase Colin Chapman, 'just add lightness'. Essentially, the lighter you make a car, the lighter you can make the components - it becomes a self-fulfilling prophesy. Lighter cars need smaller brakes, smaller engines, lighter-weight suspension components (because the forces involved are so much lower), and so on. If manufacturers can start to sell vehicles on the basis of light weight, rather than equipment and refinement, we might actually see some genuine progress in the real-world efficiency of our vehicles.

What has caught my eye recently, and inspired this post, is the Volkswagen XL1 concept. A properly light kerb weight by modern standards - about 800kg - combined with a super-slippery shape means that this plug-in hybrid could deliver real-world economy figures of over 100mpg. I hope that the rumors of a short production run are true, even if the resultant cars are likely to be unattainably expensive. It may only have a tiny diesel twin and a 26bhp electric motor to get it moving, but thanks to that low weight, that is more than enough. Keeping the weight down also means that the battery pack can be kept small, and yet still deliver a 22 mile electric-only range. The fact that VW have created this apparently genuine hyper-economy car through reductionism is something to be applauded. Hybrids aren't really my thing, but I think the XL1 is fabulous.

Finally, this little rant would be incomplete without mentioning the Murray T25, a car that can't be built soon enough as far as I'm concerned. As you might expect from the brain behind the McLaren F1, it's a work of design genius. I truly hope that the presence of a 550kg, 3-seater city car gives other manufacturers the wake-up call they need as they prepare to turn out yet another 1500kg hatch. However, this will only happen if we, the consumer, can learn to appreciate that there are more things to the suitability of a vehicle's design than noise suppression, electric seats, and how many sets of golf clubs you can fit in the boot.

DB2011AU00070

Categories: Cars, Design

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