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Project Honda Insight, Part 18 – Stage One’s conclusion

Assessing the results of Stage 1

by Julian Edgar

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At a glance...

  • 0-100 km/h time
  • Fuel economy measurements
  • But what about driveability?
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This series is based around a 2001 model hybrid Honda Insight.

The Insight remains one of the most aerodynamic and lightest cars ever made, with a Cd of 0.25 and a total mass of about 850kg from its 2-seater aluminium body.

The intent of the project is to turbocharge the engine, add water/air intercooling and programmable engine management, and then provide new high voltage batteries and a new electric motor control system.

The aim is to build a car with the best performance/economy compromise of any in the world.

The series so far:

Project Honda Insight, Part 1 – Introduction

Project Honda Insight, Part 2 – Fitting an Alternator

Project Honda Insight, Part 3 – Building an Airbox

Project Honda Insight, Part 4 – Intercooling Requirements

Project Honda Insight, Part 5 – Intercooling System #1

Project Honda Insight, Part 6 – Intercooling System #2

Project Honda Insight, Part 7 - Turbocharging

Project Honda Insight, Part 8 - Building the Exhaust

Project Honda Insight, Part 9 - First Electricals

Project Honda Insight, Part 10 - Alternator (again!) and beginning the MoTeC wiring

Project Honda Insight, Part 11 - New ignition system and cam sensing

Project Honda Insight, Part 12 - The MoTeC CRIP

Project Honda Insight, Part 13 - Idle Speed Control

Project Honda Insight, Part 14 – First road tuning of the MoTeC

Project Honda Insight, Part 15 - Refining the on-road tune

Project Honda Insight, Part 16 – The digital dash

Project Honda Insight, Part 17 – Lean cruise and driver adjustable controls

This issue: Assessing the results of Stage 1

Last issue we developed a very sophisticated lean cruise mode for the Insight, and added two driver-adjustable knobs. Now it’s time to wrap-up the first stage of the Insight project – did we meet our stated fuel economy and performance goals?


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The goals of the first stage of our Insight project were a 0-100 km/h time somewhere in the seven second bracket, and open road fuel economy in the Threes (in litres/100km).

I wish now I’d added another criterion: driveability better than the factory car without electric assist working – but more on this in a moment.

So those were the goals – now, were they met?

No they weren’t!

But I got close….

The Stage 1 modifications

A brief recap of the car’s modifications:

  • Hybrid system not working - DC/DC converter, HV battery pack and motor controller removed

  • Denso copy alternator (90 amps) and three belt idlers fitted on custom-made brackets

  • Larger 12V battery relocated to rear

  • Mitsubishi TF035HM-13T-6 turbo

  • Water/air intercooling system

  • New airbox

  • 2-inch mandrel exhaust with two resonators and cat converter

  • Larger 12-hole injectors

  • Triple Bosch MEC-723 coils

  • Two steps colder NGK R7437-8 competition plugs

  • MoTeC M400 engine management

  • MoTeC ADL3 dash (replaced CDL3) and SLM LED display

  • MoTeC E888 CAN expander


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Measuring a good 0-100 km/h time proved quite difficult. Give the car too many revs on launch and the little 165 tyres just spun. Give the engine too few revs and it would bog down before coming onto boost. The best, consistent result came with just the right amount of wheel-spin.

This approach resulted in a 0-100 km/h time of 8.2 seconds.

To do any better than this would require increasing peak turbo boost, or holding it at a higher level for longer – neither of which I want to do. My reluctance to go higher in boost from its current peak of 80 kPa (11.6 psi) is based on:

  • the amount of ignition retard already required to avoid detonation on this 10.8:1 comp ratio engine

  • the thinness of the factory con-rods

Putting this another way, I reckon the car’s quite happy on this much boost; I don’t think it would stay happy on anything much higher. In addition, the injectors, despite being 63 per cent bigger than standard, are right on their limit. Going higher in boost would need another injector upgrade.

So the 0-100 km/h time is 8.2 seconds – a time that does not meet the goal of being in the Sevens.

Fuel Economy

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So what about fuel economy? Did we meet the goal? It depends so much on how you measure it!

Driven with an eye towards economy, on the open road the car will easily turn in fuel economy in the Threes (litres/100km).

Note that this does not mean the use of 'hypermiler' techniques like pulse-and-glide, or coasting down hills in neutral – or even crawling away from traffic lights. Instead I am talking about early gear up-changes, using low amounts of boost, and reading traffic a long way ahead so that throttle lifts can occur early. It also involves dropping (say) 10 km/h on open-road hills – so from 110 km/h to 100, for example.

However, unless you are chasing max fuel economy, driving in this way isn’t so much fun.

Driven with a bit of verve, fuel economy will worsen to being in the Fours. Indicatively, this approach uses a burst of boost every now and again, perhaps redlining occasionally, and pushing a bit through traffic.

Driven hard – full boost, lots of throttle, lots of acceleration – and fuel economy will turn into low Fives.

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Note: the same economy – Fives - will also be achieved with more gentle driving but if the air conditioning is run all the time. The air con worsens fuel economy by about 15 – 20 per cent.

Driven really, really hard, the car will deliver low Sixes. I am talking redlining every gear, top speed, almost all driving done at either full throttle or zero throttle.

My judgement is that this does meet the stated fuel economy goal of 'Threes' on the open road. However, I don’t think I will be seeing this much – but that’s because I want to be able to sprint up hills at speed and whoosh past trucks!

So the open-road fuel economy goal of being in the 'Threes' is met.


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Driveability should have been one of my initial criteria of success.

Having never mapped programmable management before, let alone from a blank slate, I wasn’t aware of how incredibly finicky and precise the tune needed to be if driveability was to be better than the factory Insight (and similar to how most unmodified cars are).

Getting the required degree of driveability (ie what I was happy with) took infinitely longer than tuning the basics of fuel, ignition, boost, EGR – and so on.

And there’s another very interesting point to keep in mind about driveability.

Decisions made in the tuning to improve driveability have made a large difference to the fuel economy outcome. For example, I deliberately forsook best fuel economy for better driveability in three key tuning areas:

  • Throttle enrichment

  • Air/fuel ratios on boost

  • Lean cruise

In each of these areas I started off with strategies that gave better fuel economy, but then changed them in order to improve driveability. So I pour in the fuel on throttle transitions, run richer than stoichiometric on any boost, and delay my transition into lean cruise - and then don’t go quite as lean as is possible.

The change to greater throttle enrichment gave these improvements:

  • Better on/off throttle transitions

  • Smoother response after gear changes

  • Greater smoothness when others drive the car

  • Improved in-gear throttle response

The use of richer air/fuel ratios on any boost gave the following advantages:

  • Earlier development of boost, especially when climbing hills

  • Better throttle response in transition to boost (ie around 100 kPa absolute)

The use of a less extreme lean cruise mode gave the following advantages:

  • Better throttle response on hilly roads, winding roads and urban roads (because transition into lean cruise is delayed until the car is being driven with only small throttle movements)

  • Smoother driving (because air/fuel ratio enleanment doesn’t reach the point at which engine smoothness starts to suffer)

  • On/off status of lean cruise, and transitions in and out of lean cruise, often not perceptible to me, and almost always imperceptible to other drivers

So to retrospectively add another criterion to list: the need for excellent driveability was met.

The good and the bad

There were a few things that turned out to be enormous pains in the butt. And, other things that worked really well straight out of the box, so to speak.

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The alternator mounting took a huge amount of time – it was difficult to fit in, the brackets needed to be precise and very strong, and no less than three idler pulleys needed to be used to achieve correct belt path and wrap. At idle with the air con working at full blast, and the lights on, the 90 amp alternator’s output is only just adequate (70 amps at idle). If I knew then what I know now, I’d think very carefully before choosing to fit an alternator to an Insight.

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The pump for the water/air intercooler had to be twice changed so that cavitation did not occur. Of the three pumps tried, the only one that was acceptable was the factory water/air pump from a Subaru Liberty RS. I wonder how many other aftermarket water/air intercooler systems have cavitating pumps?

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The Bosch ignition system – three MEC-723 coils and an 0 227 100 203 ignition module – works extremely well, lighting even very lean mixtures, and the coils and module running quite cool.

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The larger Denso 12-hole 23250-03010 (US market - 00-01 Toyota Camry four cyl) injectors work flawlessly, even giving an excellent idle.

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The MoTeC M400 ECU and ADL3 dash, while boasting some idiosyncratic tuning and programming approaches, are given excellent support by MoTeC and are capable (especially when working in concert) of achieving extraordinarily flexible and creative outcomes.

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The Miro Module, produced by eLabtronics, that takes the output of the two inductive cam sensors and turns them into a single square wave for the MoTeC ECU, has worked perfectly. The development of this custom module saved a large amount of work over doing it in any other way.


So that’s the end of Stage 1. Stage II will involve a new electric motor controller, new High Voltage battery pack and a new Battery Management System.

The new system should be able to over-rate the 10kW standard electric motor for short periods, and with all that torque available just off idle rpm, the engine (and so turbo) should be able to be brought up to speed very quickly.

Estimates suggest that the torque at 2000 rpm should be able to be doubled. If that’s the case, the torque curve should then be flat from around 2000 – 5500 rpm… something that should give incredibly good driveability.

The original aims for this next stage were 0-100 km/h performance in the Sixes, and fuel economy on the open road in the Twos (litres/100km) – I now doubt that I’ll achieve the latter but I think it’s possible I’ll scrape in the performance figure.

That’s the plan, anyway…

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