I can apparently chip my 140bhp TDi up to 200bhp. The question is, if I declar it to my insurance company (direct line) will they really sting me? Is there a certain percentage I can increase the power by that they will allow without a massive hike in premium?

FWIW I am more interested in the fuel economy benefits, with the power as a bonus, but the guy acted as though I'd said I was from Mars when I asked about keeping the power the same but increasing the economy…

Any "run-of-the-mill" insurance company will just see it as a power modification, and will almost definitely increase tyour premium. Cheaper insurance may be had by looking at specialist insurerss, but the hike in your premium is likely to take a dent out of your economy increase!

HTH

Depends on the company. Direct line will probably refuse to insure you, most wont even quote with a power-modified vehicle. Nominally 10% is the increase allowable (with premium hikes) before it is considered a major mod and at that point you seek specialist insurance). Direct line refused to insure my mildly modified 200hp vehicle, so I found a decent insurer (Sky) who charged me less for 300hp.

There are sod all fuel economy benefits in a TDi. The way you increase power in a D is to inject more fuel at the correct time. You may be able to keep the same economy and get more power, but if you use that power you will lose economy, this is proved time and time again by owners who start out with good intentions but get addicted to the right foot 🙂 ).

if you increase the performance, then the insurer will increase the premium – pretty obvious I suppose. They will care not a jot if your intent was to improve economy.

How much is down to the individual insurer (and, it seems, the phases of the moon. I reckon they just guess a number anyway). Only answer id to call them ans ask. Most are OK once you get to speak to a human – tell them the plan, and they will check with the underwriter, and call you back with the joke of a price.

I've had 3 diesels remapped and in every case the extra power has increased fuel economy. I suspect it's down to being able to drive more gently/use less throttle for the same speed.

As you say it's a 140bhp I'll guess it's a vag 2.0 tdi of some sort? If so be a bit wary as that's an enormous increase to offer at about 45%, mine previous ones have been more like 25-30% and also as VAG had lots of ptoblems with the genuine 170bhp versions of that engine (most were remapped/updated at services with a different software giving lower power after lots of problems).

Some remaps are easier for dealers to identify than others, and you can also get units that allow you to flash the original map back at service time. Not condoning witholding info from your insurance company of course, but I know some people do it that way.

A good remap can make a *massive* difference to performance and economy in my experience.

It still takes the same amount of energy to accelerate the car over a longer or shorter time (laws of physics here), so the only difference a remap could offer fuel economy is if it vastly increases the thermodynamic efficiency of the engine above what the manufacturer could manage (while trying desperately to achieve good mpg figures to beat competition). I'd be surprised if anyone managed that, I'd be less surprised if peoples driving subconsciously changed to drive more gingerly to test their economy if that were their interest, and more harshly to test power if that were their interest.

Any remap is easy to identify. All dealers have access to the exact file your car has in its system,any change from that is as simple as spotting spelling mistakes in a copied word document. You could re-map it back when required, but the noly time it woudl be required is when you need to cash in your insurance, and you'd best hope that both it and you are in a state to be able to do that before it gets taken away by the insurance company.

There are sod all fuel economy benefits in a TDi. The way you increase power in a D is to inject more fuel at the correct time.

CK – more fuel at lower revs = more economy. The expansion of hot gasses can do more work if it's contained in the cylinder for a longer (time) power stroke – since less of it will be exiting the exhaust.

If you were correct, then driving at 70 in 3rd would be equally efficient as driving at 70 in 6th, but it's not. If you do the former your EGTs will go up which means more wasted heat.

At least that's my theory – I've never driven with an EGT gague 🙂 The difference in valve timing could also affect economy, but it still stands that lower revs = better economy.

The FE increases spoken about by mapping companies are due to being able to better use higher gears at lower speeds, as I understand it. So on the motorway would make no difference I guess, but around town it would.

On the subject of engine mapping – the Bluemotion TDIs have a different map for better fuel economy, and this results in apparently less low end torque. I want to know what they've actually done, and can I have it done too? It could possibly be due to a smaller turbo with less backpressure I guess… But then again, it'll be a VNT turbo so maybe they just keep the vanes closed for longer…

I've insured with Brentacre (broker in Wales somewhere – google them) for years. They've always been cheapest for modified / quick stuff for me, often insuring a modified car for less than I was getting quoted for a standard model. I've no personal affiliation with them…

To be honest, I'd be wary of that size of power hike. I had a 25bhp increase on a 406 (110HDi to 135), and the bloke told me he could do more, but you risked lunching the dual mass flywheel, which is a big bill. 60 bhp is a big increase and I think you'd be seriously risking drivetrain damage with that. I eventually lunched the flywheel anyway…

On the other hand, 25bhp wasn't seriously noticeable – felt adequate rather than gutless in 1.5 tonnes of car, whereas some people would tell you it's like a rocket booster. The power increase was there – measured it with some RaceTechnology kit. I didn't notice any fuel economy difference to write home about. You'd probably make a bigger saving switching to EcoContacts or another low rolling resistance tyre, but I think they're hateful things – noticeably less grip. Or tape over all the panel gaps & fit all the undertrays from the Bluemotion model.

I've had modified cars before, and always gone with "specialist" insurers – Adrian Flux, Sky and (oddly) Elephant have always been best. Currently with Sky. Generally not too much of a premium increase for most mods or first 3 points. The big changes all seem to be in line with chips/remaps/ECU swaps. Conversely, noone at Sky seemed bothered when I told them about the whopping great turbo I strapped to my previous car. Anyway, Elephant don't like chips at all, and with the other two I've seen big premium increases with aftermarket ECU that up power by more than 25%.

Forgive my ignorance, is "chipping" actually changing a chip on whatever electronics runs the engine?

You can increace fuel economy and get more power, but only if the manufacturer really ballsed up the first time arround. Take an old car form the 70's, fit megasquirt, disconect the fuel hose form the carbs and get 25% more power and 25% better economy. I'm tempted in the midget but hear too many stories of snaped driveshafts.

5th gear did an economy test and did as you suggested, as well as stripping out all the spare parts, emptying the boot, fitting low rolling resistance tyres, waxing the bodywork etc. Gave lower mpg, their conclusion IIRC was that chipping and anticipating economy gains is utterly futile.

I suspect if you ever saw a difference before it was becasue you were looking for one, and probably gave the engine a service at the same time?

Normally it's a reprogramme via the diagnostics port. On old cars (ie, Bosch K-jetronic injection & VW Digifant – pre 1990s tech) people actually swapped physical chips.

Coffeeking…not true about how easy it is to identify a remap. This varies greatly between cars & manufacturers. Some are only at best able to look at a map flash counter to identify any changes for example.

Forgive my ignorance, is "chipping" actually changing a chip on whatever electronics runs the engine?

Depends on the car.

Some just reprogram the existing computer, others are a case of an entire new circuit board. Others cheat and just trick the ECU into believeing its in a different gear or cold air to make it put more fuel in as if in doubt more fuel is usual more powerfull (within reason).

Aftermarket systems like megasquirt replace the ECU completely and can simply be fiddled with via a laptop as your driving allong!

Well the guy I spoke to was at Celtic Tuning which is a pretty well respected organisatin as far as I can tell, and they said you would see 2-5 mpg increase (depending on the type and style of driving) due to being able to use lower gears more.

And yes I am talking about remapping ie installing several new fuel maps; chipping as it used to be was just sticking a chip in place of the old one that changed the injector opening times I think, which was crude.

The car is indeed the VAG common rail job. It comes in a 140 and 170bhp version with I think mostly the same stuff on it, so you could argue that a 140 is just a de-tuned 170.

In the case of diesels, the manufactuers hugely de-tune the cars to make them look reliable.

And as for Bluemotions, they have longer top gears, they are lighter, they are also lowered, and they have lower rolling resistance tyres as well as a different engine map and possibly turbo (not sure about the turbo, tis just a theory).

PS I have michelin energy saver tyres on the Prius and have not noticed any difference between them and the previous Michelin Premacy ones. I don't rag the car of course, but I do corner reasonably briskly to increase MPG, and it was one of the ony cars to make it up our hill in the snow.

Forgive my ignorance, is "chipping" actually changing a chip on whatever electronics runs the engine?

Can be, but not necessarily.

At least that's my theory – I've never driven with an EGT gague The difference in valve timing could also affect economy, but it still stands that lower revs = better economy.

I've driven with an EGT gauge, my highest EGTs are at WOT and light cruise, but that's a petrol car 🙂

You need to make the same power to maintain the same speed, yes, and using a higher gear means you can slow the engine down. However the reason you won't get good economy in 3rd is because the brake specific fuel efficiency of the engine tails off at high revs, but it also happens at lower revs too (and this is why your EGTs are lower) because the heat in the combustion has more time to escape through the cyl walls rather than do useful work. The engine has a specific thermodynamic profile, its brake specific fuel use dips at a lovely mid point where things like flame front progression, rpm, turbo pressures and intake/exhaust resonances form the ideal minimum for that engine. Throwing more fuel in wont change those physical parameters, it just increases the amount of fuel used at those revs and possibly wastes some of it. Unless your engine management is programmed from the factory to be particularly naff you should not see any increase in efficiency with more fuel, only an increase in power. Sure you may be able to stay in gear longer (at the low end) due to higher torque but if you compare that to being in the next gear up under a lot less load I'm not sure the gains stack up. Your friends in the diesel tuning place can well get 2-5% economy increase (bear in mind that's what 3mpg max?) but "depending on driving style" says it all really. You can get more power easily, obviously, but efficiency is a different matter.

I'm not saying don't do it, and some cars react better than others depending on how good the manufacturer is, but I'd suggest you accept that it's not an economy mod, unless you need to convince your wife etc, then hide the fuel receipts.

Going from 140 to 200bhp might give you clutch issues.

I know that the 1.9TDI 130 can be remapped to 170-180bhp without too much bother, but the standard clutch can cause issues soon after the remap.

the brake specific fuel efficiency of the engine tails off at high revs, but it also happens at lower revs too

Well what are those engine speeds? That's the question. Most of these eco-model cars (bluemotions etc) achieve great MPGs partly by making 5th gear longer. Interestingly they only have 5 gears instead of 6 which would imply that the very minor weight penalty made more difference than using close ratios to keep the engine in its efficency band.

Also interesting is the claim that the new 7 speed DSG is actually more efficient than the manual. The only reason for that I could imagine is the opposite of what I just said: that keeping the engine in its efficient rev band more often helps the fuel economy.

I got the impression from the guy I spoke to (and forum posts about them) that he'd done loads of these cars and people had reported 2-5mpg improvement.

Bear in mind that this is a common rail engine so may even be able to control the flame front using the engine map, as well as turbo pressures and whatnot. What's also a strong possibility is that they might change the injection timing. More advance means more NOx so they back it off at the factory, but if you advance it you get more power and economy.

How much of peoples claims of increased fuel efficiency do you think could be put down to the trip computer telling them so? Can you rely on the computer after a remap or will it still be thinking its putting in the same amount of fuel from before the remap?

Well what are those engine speeds?

Depends entirely on the engine in question, they tend to have a small plateau but there's a definite peak such that from one gear to the next you're likely to drop off either side of it. I don't have any example values to hand. But bear in mind also that your blue motion type cars do have a taller 5th rather than a 6th, but that's actually mroe likely to be manufacturing cost issue IMO, unless they already have an existing 6spd box that can be easily tweaked.

Bear in mind that this is a common rail engine so may even be able to control the flame front using the engine map, as well as turbo pressures and whatnot. What's also a strong possibility is that they might change the injection timing. More advance means more NOx so they back it off at the factory, but if you advance it you get more power and economy. Bear in mind that this is a common rail engine so may even be able to control the flame front using the engine map, as well as turbo pressures and whatnot. What's also a strong possibility is that they might change the injection timing. More advance means more NOx so they back it off at the factory, but if you advance it you get more power and economy.

Yup, with common rails you can time main injection, pre injection vols and times etc, but I'm not convinced that the tuning makes that much difference. I'd say fractions of a percent are more likely but even 2% is easily absorbed by mistake and mis-calculation. No two pumps have the same cut-off pressure so unless you brim the tank to a visible brimming location every time, and know you're using standardised fuel (not mixtures of winter/summer D, old and new D etc) you can never rule out that sort of change size as just a combination of factors.

When I first re-mapped my petrol car (done myself, road tuning) I manage to get 34mpg from a car that didn't do more than 24 originally. I then spotted I had warped my exhaust manifold as I was running too lean and too retarded (oddly). On bringing the AFRs back in tow and keeping EGTs within reason, I was back fairly close to the stock fuel economy, but masses more power. I can't get my lean cruise much better than the manufacturer had it despite having more variables to play with.

We'll have to agree to disagree. I was planning on getting the remap kit for my D at some point in the near future, I'll see if I can make any gains in economy to rubbish my own theory!

Can you rely on the computer after a remap or will it still be thinking its putting in the same amount of fuel from before the remap?

That does indeed depend on how they calculate it. If done right they should monitor injector durations and pressures. If done cheaply and easily they may just measure load and speed.