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[Turk]

Yesterday my mate fitted one of these electronic"tuning boxes" to his '07 Fiat Sedici 1.9 (I think) TD.
On starting the car the revs were erratic and increasing for the 10-15 seconds until he got a bit concerned and switched the engine off. He removed the tuning box and the EML light stayed on.
I told him not to worry about the EML as it would probably clear after a few "clean starts", which it did.

I've used the box manufactured by Tunit myself on my previous Mig and that was a 10 minute to fit, "plug 'n' play" affair...well, until my AR25 autobox gave up about 200 miles later due to the increased BHP.

My question is, are the erratic and upward revs normal for these boxes and is it just the electronics "learning" the settings etc with the tuning box ?

[Marks DTM Calib]

No thats not normal.

I assume he has the multijet common rail.

I dont like these boxes, they do nothin more than modify the fuel rail pressure signal to the ecu so it thinks the rail pressure is lower than it really is and hence fires a longer duration dose of diesel in.

[Turk]

He's not entirely sure he had it "in-line" on the right plug connector. Would that have resulted in the erratic revving ?   

[hotel21]

There was a big selling pitch/stand at the Pikey Palace show at the Scottish Exibition Centre last week.  Tried to get the guy to quote what the boxes actually done in a non snake oil language and he failed miserably....

[Marks DTM Calib]

Pretty much impossible to get wrong...it just fits in series with the pressure sensor....which is on the end of the fuel rail

[Marks DTM Calib]

There was a big selling pitch/stand at the Pikey Palace show at the Scottish Exibition Centre last week.  Tried to get the guy to quote what the boxes actually done in a non snake oil language and he failed miserably....

There is a bit more to them than just a resistor network.

They have a small (and very cheap) microcontroller in them and it applies 'a map' (it is just about a map in the loosest terms of the word).

As the main high pressure pump is engine driven, the real rail pressure is proportional to engine speed and hence the micro can get a rough estimate of the revs. It can them apply a factor to the modified pressure signal to the ECU....hence they do not add additional at idle and only modify the signal at higher revs.

[Marks DTM Calib]

Its worth adding a few thoughts about the serious limitations of such a tuning approach.

• Its buggering with a critical signal for the engine operation in order to up the fueling, this is far from ideal.
• It does nothing to the turbo pressure and hence could (and most probably will) overfuel and result in more soot out the exhaust (NOT GOOD FOR UNITS WITH A DPF!)
• Its a crude approach as its only input is a guess at rpm.

A proper remap is a much better option as this will have the ability to add 'extras' e.g.

• It can increase the boost as well as the fueling.
• Its able to apply a modified map based on all engine parameters.
• It can add extras like disabling the EGR.
• It can stop the power increase occuring in gears 1 and 2....where its not needed.

Much better all round and if you shop around.....not dissimilar in price.

Of course, when they are trying to sell you these 10 quid boxes (as they cant cost more than that to make) they dont tell you this.

Also be vert careful of claims of economy increases as the ecu is now being fooled as to just how much fuel is going in.....so its reporting a value to the fuel computer when in reality more is being used due to the higher than reported rail pressure.!

[Turk]

Had a look at it this evening and it had been connected to the plug. It's fitted and working now. Thanks for the input 

[Squealey]

I had a tuning box on my Passat 110 TDi which took power up to 124bhp. Not sure of the make but it had a Cheetah type animal on the blue box and it wasn't cheap (£350ish if I remember correctly)

Definitely worked, but the car smoked like hell with it on. Ended up removing it and selling it on Ebay as I was a bit concerned what damage it may be causing.