Youve probably all seen a thread of mine, pretty much all asking a similar thing, but i hope this will be the last.

My car has a decat, no backbox (mufflerectomy) and a Unit 18 remap. Its just recently started acting strange. In high gears it seems to cut the power if I accelerate hard. There is an increased noise from the exhaust, and only turning the car off will solve it. I had this problem last week, a scan showed it to be a boost control valve, which I replaced and solved the problem.

These past few days it's been doing it again. Ive had a scan which showed no faults, and Ive tested the Air mass meter, and that works fine.

Ive been given two different pieces of advice by two different sources.

The remapping company suggests replacing the cat or backbox as there is no backpressure.

The company that did the scan suggests the remap needs to be tweeked as it was written for a KKK turbo, which has been replaced with a Garrett unit off the newer models.

Can anyone give me the real answer. Id love to replace the backbox and solve it, as I have the backbox in the shed, but would it actually solve anything?

Thanks all

Point 2 sounds like your problem, your map was setup on a different turbo. you have changed the turbo and not the map to cope.

Back Pressure i thought was only needed for Petrols....

Not so much a definative answer but... If i was having these problems with my car i would go down the line of replace the backbox (as its free to do) see if its cured the issue. Failing that you could try a map for that specific turbo

Did it start behaving like this after you changed something (remap, turbo, backbox)

My first idea was to get a remap, since you changed turbo.

Don't think back pressure from the exhaust is an issue on a car with a turbo (but could be wrong with this)

I thought the turbo needed the back pressure to stop it overboosting?

Back pressure on a diesel has 2 effects:-

1) It increases the boost you can run without getting an overboost from a given base engine and map.

2) It supports the exhaust turbine bearing seals, and reduces the chance of getting oil leaks into the exhaust.

Youve probably all seen a thread of mine, pretty much all asking a similar thing, but i hope this will be the last.

My car has a decat, no backbox (mufflerectomy) and a Unit 18 remap. Its just recently started acting strange. In high gears it seems to cut the power if I accelerate hard. There is an increased noise from the exhaust, and only turning the car off will solve it. I had this problem last week, a scan showed it to be a boost control valve, which I replaced and solved the problem.

These past few days it's been doing it again. Ive had a scan which showed no faults, and Ive tested the Air mass meter, and that works fine.

Ive been given two different pieces of advice by two different sources.

The remapping company suggests replacing the cat or backbox as there is no backpressure.

The company that did the scan suggests the remap needs to be tweeked as it was written for a KKK turbo, which has been replaced with a Garrett unit off the newer models.

Can anyone give me the real answer. Id love to replace the backbox and solve it, as I have the backbox in the shed, but would it actually solve anything?

Thanks all

When you state "newer models", does that mean a "PD150" or "PD160" turbo - GT1749B? If your map was written for the slightly smaller KKK turbo, I'd say it's likely tweaking the map may help if it's overboosting, which it may be. Replacing the cat and/or backbox is also likely to help in this respect.

J.

Wow thanks all for the quick replies.

To answer some questions:

The turbo is just the Garrett unit used in the later PD130 engines, I think the ones with the BLT engine code.

When I first had the map it dropped off the power on the drive home, but never happened again from then until now. I replaced the old turbo and since the new one was put on its been fine one week, and a niggle next week, but Ive only replaced the standard boost pipes and one boost control valve.

Ive been quoted £250 for an APR map in a garage 5 miles away, is APR good if I do decide to have a new map. The Unit 18 map is good, but a 350 mile round trip isn't really something I wanna have everytime there is a problem

When I first had the map it dropped off the power on the drive home, but never happened again from then until now. I replaced the old turbo and since the new one was put on its been fine one week, and a niggle next week, but Ive only replaced the standard boost pipes and one boost control valve.

This is intresting, you had the same problem happen AFTER the map on the first turbo?

Give Ali a ring if unit18 did it and talk to him, to have a different map you will need your STD map putting back on first

This is intresting, you had the same problem happen AFTER the map on the first turbo?

Give Ali a ring if unit18 did it and talk to him, to have a different map you will need your STD map putting back on first

I spoke to Ali both back then, when the turbo went, and today. Hes the one that told me to replace the cat or backbox.

Ive also been told that the new map can just overwrite the current map, so it wouldn't need to be taken off, apparently.

If Ali and his team do the map they can, but 99.9% of the time, if a 3rd party comes to ammend someone elses map, then they bung the original map back on and start from scratch, its a bit dodgy getting someone else to ammend unit 18s map..... they wont know what has been done :no:

TBH if he says put the back box back in then put it back in, if he mapped it and he knows why its doing it, i would take his word for it.

If Ali and his team do the map they can, but 99.9% of the time, if a 3rd party comes to ammend someone elses map, then they bung the original map back on and start from scratch, its a bit dodgy getting someone else to ammend unit 18s map..... they wont know what has been done :no:

TBH if he says put the back box back in then put it back in, if he mapped it and he knows why its doing it, i would take his word for it.

+1

You can usually swap between KKK and Garrett versions of the turbo on the PD130 without a problem.

You can usually decat without a problem.

Removing the backbox is a different matter and usually requires an adjustment to the map.

TBH, it appears that Ali has given you the definitive answer that you need.

Ye from what I understand they were gonna adjust the standard map, not the Unit 18 one.

im gonna get the backbox put back on this weekend so Ill let u all know how I get on