Our technical editor, Robert Pepper, is here to answer your questions about, well, technical and this week he talks about whether you should tune your car engine.

LAST WEEK, I received a letter from a reader asking about whether they should tune-up the engine of their near-new Toyota LandCruiser 200. He wrote:

“About six months ago I bought a near new 200 series and have been considering the myriad of after-market additions I want to add to the car (and in what order). Obviously you have covered things like snorkels, bull bars, suspension, etc in detail in your book [Robert is the author of the off-roaders bible, the 4WD Handbook] but one thing I was interested in was your opinion on ECU tuning/remapping/chipping (usually in conjunction with exhaust) as an upgrade.

“Again I realise this is a very personal question because if you ask 100 different 4wders, you will probably get 100 slightly different responses as to how much they would or wouldn’t modify their cars.”

And here’s the answer:

Personally, I wouldn’t bother. I think modern vehicles have enough power – how often do you find yourself flooring your 200, wishing it had more grunt? Would you get to your destination any quicker? Be able to make more overtakes? I can’t see it. Sure, we all like the thrill of acceleration, but in the real world 0-100 in 10 seconds doesn’t shave any significant time off a journey compared to 0-100 in 7 seconds.

All these mods offer extra power, economy…and they do work, the power is there.  But do you think the manufacturers, who use engine outputs for many cars for selling, would not squeeze out and extra 50kW, 80Nm if they could? The fact they haven’t should give buyers pause for thought. Any time an engine is asked for more power it is a tradeoff – emissions, consumption, life – and there’s extra stress on the drivetrain too. There’s no such thing as a free lunch. Also, with the best will in the world, the engine tuners simply cannot test to the same degree as the original manufacturers.

I have not engine-modified any of my cars for this reason, not even the Defender TD5 which actually could do with more power. My Ranger came with a mod which was deleted during fault-finding, and I’ve not put it back. It has a 3″ exhaust which I’ll leave on, but that doesn’t make any appreciable difference.  In fact, that exhaust developed a hole which had to be welded shut.

If you want better performance then try weight reduction, which has the same effect as more power on acceleration. Let’s say your 200 weighs 3000kg, and it is good for 195kW. That means each kW has to push 15.3kg of Cruiser. If you reduce weight to 2700kg that becomes 13.8kg per kW, similar to a power increase to 217kW. Except of course the lighter car now performs better off-road, takes less braking effort, sinks in less.

There is also a huge variety of power modifications, chips, tunes and the like.  Some are carefully thought out and mapped to the car and engine, with minimal impact to either.  Others are less well developed.  It is hard to tell which is which until several people have run the system and discovered problems, or not.  I’ve seen several cars with intermittent errors, then a tuning module is removed and the error is no more.  Choose carefully, based on how other people are going with the modification, and beware big claims.  The better systems make smaller claims, carefully worded, and are open about how they work.

So my advice to people wanting more grunt is to reduce weight. Problem is finding accessories that are both light and strong, because the aftermarket attitude is make it big and heavy, then keep adding power to deal with the weight problem.

Got a technical question for us? Email robertp(at)practicalmotoring.com.au