Car modification goes in cycles, in trends of popularity and enthusiasm. Sometimes stupid ideas are abandoned; other times they’re fervently embraced.

When I first started writing about car modification – it would have been back in about 1987 or 1988 – almost no workshops had dynos. Back then, performance claims were largely the stuff of description. You know, this exhaust will give your car just fantastic power, mate.

Pradoxically, some of the first companies to use dynos to ‘prove’ power gains were the very same companies that had no power gains to prove. But they knew that with so few dynos around, and with knowledge of how to fudge dyno figures commensurately low, their advertised dyno improvements would have credibility.

For a while at least.

But now every serious workshop has a chassis dyno. Mods which give no power gains are still being widely sold (polished throttle bodies, restrictive aftermarket cold-air intakes, exhaust systems with no engine management changes) but for the inquisitive, finding the efficacy of the mods is only a few dyno runs away. One dyno run at the place selling the goods and another at an independent workshop.

But the ubiquity of dynos is leading to an outcome which is nearly as bad as the times when they didn’t widely exist. Instead of simply taking advantage of the research and development tool that gives enormous flexibility and freedom, workshops are being increasingly constrained in their modification approaches by dynos. As in, some tuners spend literally all of their time on them.  Which’d be fine if their customers drove cars only on dynos… and not on the road.

We’ve driven modified cars that detonated like crazy when road tested – they’d never been off the dyno for final engine management tuning. We’ve talked to tuners who believe that all the mapping can be done on the dyno – despite the fact that their brand of dyno cannot replicate trailing-throttle events. We’ve talked to modified car owners who swear blind that their car makes more power on one dyno than another. And now we’ve got to the bizarre situation where dyno manufacturers no longer even have universal power measurement. Was this run done in shoot-out mode, sir? WTF? Are you telling me that a horsepower is no longer a horsepower? That kilowatts are no longer kilowatts? Well, in that case, how long is the metre rule that’s used in your workshop?

The slowness of the aftermarket to embrace electronic system modifications that don’t involve engine power is largely because modified car mechanics are becoming increasingly besotted by their dynos. Where’s the traction control, stability control and gearbox control interceptors? Where are the electronic throttle control mods? But hey, on a dyno you don’t turn any corners, the drive wheels aren’t supposed to ever spin, and there’s only one throttle position – flat to the boards.

As many of you will know, together with electronics magazine Silicon Chip I have been developing a range of DIY electronic kits. These will be able to modify pretty well any electronic system in the car – including such things as stability and traction control systems. However, they can also be used to modify air/fuel ratios.

And where did we do our prototype development air/fuel ratio tuning? Despite having access to a dyno, we did it all on the road. That way, every moment of the testing could also be used to assess driveability, ease of tuning, transient mixtures – and so on. Cos it’s a road, you see. And with a Motec air/fuel ratio meter for mixture strength, with amplified and filtered earphones for detonation detection, with an OBD readout (in cars equipped with this facility), all the information needed was readily available.

Of course, this way you spend plenty of time doing the tuning, and you need to have a mate along, but the end result is guaranteed good driveability. Because the tuning hasn’t been done in an artificial environment with poor airflow, non-representative acceleration rates, little throttle-lift inertia – and all the rest of the drawbacks that dyno operators never seem to remember to tell you.

In fact, I was prompted to write this column because I read in a discussion group some comments on one of our upcoming projects. Said one guy: I see that they’re doing an electronic boost control – I can’t wait to get it on the dyno and see how well it works.

Words almost fail me – the dyno is the very worse place to test a turbo boost control system.

Let’s take a look at the drawbacks.

1) The acceleration rate in each gear is not representative of what is achieved on the road. This one’s a killer because boost overshoot on transients is hugely affected by the rate of engine rpm increase.

2) Very few people do full throttle gearshifts on the dyno. You know, race up through the gears – to the redline, change gears, to the redline, change gears. Again, it’s in just these conditions that you look for boost overshoots and/or slow increases back to peak boost after each gearchange.

3) I have never seen anyone do a full-bore launch from a standstill on a dyno. And how quickly boost can be brought up in these conditions – ie controlling wastegate creep – is a major aspect of good boost control.

3) On a dyno the intercooler never works as well as on the road, so in those systems that don’t use boost pressure feedback, the actual peak boost is likely to be different from that achieved on the road.

4) On the dyno people never bother trialling all the different combinations of throttle position, load and engine rpm that you’ll find in 10 minutes on the road.

A dyno is a great tool. But unless it’s inside a windtunnel, can replicate all the different acceleration rates and inertial characteristics of the driveline, and is completely climate-controlled, it’s only a starting point.

And for many of the coming chassis control system modifications, it’s an irrelevancy.