I ran a cheap tuning box on my B5.5 Passat PD130, of the type that exploited the well-documented "substitute a fixed resistor into the fuel temperature sensor plug" trick that's common to the VAG 1.9 PD motors.

This trick fools the ECU into thinking the fuel is at a higher temperature, and therefore less dense, so it injects a slightly greater volume of fuel per cycle while remaining within the ECU's operating parameters. Never threw a CEL / code while I had it.

It did give a very useful boost in torque (for example, half a second off the 40-60mph interval in 4th gear, which is quite substantial) and had no noticeable impact on economy. In fact, I recorded the only genuine 50mpg brim-to-brim tankful I managed with that car, with the box fitted.

I ran it for about 8,000 miles but eventually removed it, because it made the throttle response absolutely hair-trigger at low rpm in the first eighth of pedal travel, which made town traffic and commuting tiresome.

But it was fun and well worth the money (about £25), in my view.

Edited by craig-pd130 on 12/12/2011 at 16:32

My mate told me about his car which runs on water.....

Have been tempted in the past but if they are so good why don't manufacturers offer them as aftermarket accessories, surely that would not affect approvals.

With dpf's they are a definite no go area, the extra smoke that is a by product of dumping extra diesel in to produce more power and torque kills tham in no time, loads of evidence on continental forums where they have been using dpf's longer than us.

Had my old Focus TDCi remapped and it greatly improved the responsiveness of the engine to the accelerator as well as improving ultimate performance and mpg also went up by 2-3mpg.

I got the feeling that, as standard, the turbo wold not really kick in unless I floored it whereas, post remap, the pick-up at part 'throttle' was much better.

I'm getting my current car done next Saturday.

where they have been using dpf's longer than us.

The cars on the continent use the same engines/emissions systems as UK bound cars. The DPF is one component that should cope with over fuelling without difficulty. Extra smoke is accompanied by higher EGTs, so the soot will burn off without a problem.

Simply not true, dpf's have been mandatory in certain EU countries for many years, in the UK manufacturers only fitted them to Euro 4 cars when necessary, they only became mandatory with Euro 5.

"Not sure but I have a slight inkling that alan 350 might be someone marketing their snake oil product. He doesnt appear to have started any other threads....."

Yes, I wondered too - but as he doesn't comment on the Economy version rather than plugging that too, I think we give him the benefit of the doubt.

Alan, we don't allow free adverts, as our genuine advertisers pay good money, but you might like to confirm that you don't have any connection with the products except as a customer.

What sort of response do you get from your insurance company when you tell them you've had your engine remapped? Swiftcover would't insure mine.

It's an urban myth. All the MOT tester can really do is a visual inspection of the exhaust system to see if the Cat/DPF is there. Even then, they can't tell if the boxes have been gutted.

The MOT diesel emissions test is really just a visual smoke test. If they used the same gas analysers that they do for petrols, then EGR delete/cat gutting would flag up straight away...

But madf, I thought your Yaris never went north of 30mph-extra power is surely redundant?! ;)

Interesting observation about the knock. Did this happen at cruise or just when you booted it? Knock tends to only gets worse when the timing is advanced...

The knock only happened c 1,000rpm to 2,500rpm when cold and accelerating. When cruising there was no noise. It disappeared when warm.

PS: 30mph? Far too fast for am oldie like me. I have a person with a Red Flag...

Are not remapping or any other form of tampering illegal from 2012 in the UK as part of the new MOT regulations.

How will they check, in the case of a remap?

For the last 15 years I think all of my new cars have been remapped at least once by the dealer under warranty to correct slight running problems.

Always thought my Auntie Bob was suspect.

SInce many ECUs have software updates to solve issues, I would suggest checking ECU software is impossible in practical terms.

A dealer updating the ECU software is not the same as a remap.

If you have a remap and them the dealer overwrites it with an update you will have to pay agin for a remap

Recent ECU designs have code that is digitally signed, i.e. it has a secure method of checking its autheticity via the CANBUS interface. A manufacturers update, also updates the digital signature. Third parties cannot do this.

Before long, the I expect the MOT stations will have newly mandated (siemens?) equipment that can be plugged into the standard CANBUS or whatever and check.

This will potentially only affect cars produced in the last few years.

A dealer updating the ECU software is not the same as a remap.

If you have a remap and them the dealer overwrites it with an update you will have to pay agin for a remap

Then surely an update and remap are the same in the sense that the ECU map is changed from the original - an MoT tester has no tools to detect whether the ECU map is original, authorised through the dealer or changed by a tuner.

A dealer ECU update may not change the map but change some other parameter since the ECU controls many of the cars features.

A manufacturers update is carried out for reasons other than supposedly getting loads more power and better fuel economy.

If you do go ahead do not use the figures from the fuel confuser to compare your mpg. One proven fact having looked at many forums is one thing the boxes/chips are very good at is fooling the display to show a much higher figure than you are actually getting. To get an accurate comparison you will need to do at least 3 tank to tank fill ups before and after using the car as "normally" as possible.

If its a recent diesel with a DPF simply don't do it, you will have endless DPF problems, its well documented on continental sites where they have DPF's longer than us.

If the car is still under warranty you will loose that if the dealer finds evidence of changes on an ECU check should you have a problem, some boxes and chips leave fault codes.

Don't forget to tell your insurance company.

Edited by thunderbird on 31/12/2011 at 13:39