Over boosting LCR

[NottsLCR]

Evening all,

I need some help with my LCR constantly over boosting. I get the codes below and once cleared they come back within afew minutes of driving.

17705/P1297/004759 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
17963/P1555 - Boost Pressure Control: Upper Limit Exceeded

I have ran the car with and without a MBC to limit the peak boost but this has made no difference. I have done alot of reading on here as I know most people will say boost leak/hose but all seem ok. I have ran with the MAF unplugged as read this could be a cause but made no difference.

I'm hoping to go back to Will and P Torque to get it checked out but wanted to know if ther could be anything simple or obvious to check before hand as this might not be till the new year.

Thanks

 

[8bit]

DV could be sticking? If it sticks open then it'll cause the 17705 - pressure drop code (i'm getting this sometimes at the moment, i think for that reason). I guess if it's sticking shut sometimes then maybe it could cause the 17963 over-boost code.

Try the pen test - take the DV off and push the piston in with a pen, then put your finger over the small pipe on top. Let go of the piston and it should drop back a few mm but stay open. Remove your finger from the top and it should drop back into place. If it's too hard to push in sometimes or doesn't snap shut when you remove your finger from the top then it needs serviced.

 

[Pyro]

Second one could also be N75 valve I think lol

 

[8bit]

Second on could also be N74 valve I think lol

N75 (not trying to split hairs tho!) but yes, could be that too, although if that's shot then there are usually other codes showing too. Given the other code then if the DV has been on the car for a long time without being serviced then I'd bet on it just being gunked up and all the lube grease has broken down then it's likely to be sticking.

 

[Pyro]

Cheers 8bit need to read things befor I press post lol

 

[brad1]

I'm a bit late to reply, but DV or N75 sounds like the culprit

 

[NottsLCR]

Cheers Guys,

Will test DV on saturday so see if its sticking - hope it is that simple.

Wouldnt of thought it was the N75 as when the MBC was used the N75 was only connected electronically so wouldnt influance the actually boost i believe?

 

[Pyro]

Log actual vs requested and tgat will rural out N75

 

[NottsLCR]

I'll give it ago, not done any logging before but how hard can it be.........

 

[8bit]

My money's still on the DV

It should take firm pressure to push inwards but not feel "sticky". When removing the finger it should pop shut straight away. Do this a good few times and make sure it's always consistent. How long/many miles has it been on the car? Take it it's a Forge 0087p?

 

[NottsLCR]

Yeah its the Forge 007p with yellow spring if i remember correctly. been on the car about 1 1/2 years it think so about 10,000

 

[8bit]

Hmm when I asked forge about it recently they said they recommend servicing (i.e. replacing the o-rings, piston and grease) every year or 12,000 so it might be fine then. That's probably the easiest thing to check so worth checking anyway.

Other thing might be to run your MBC in parallel with N75, I haven't used one but remember reading in one of Bill's threads about hybrid K04 cars that he reckoned that was the best way to do it, I think to allow use of the MBC to cut back on boost spikes but keep the boost up the rev range. Might be worth a bit of research and giving that a go?

 

[rsmith]

I have seen my car over boost due to leaks, get it leak tested, failing that I would put my money on the map that's on it.

 

[t32er]

i dont think its the N75, easy way to rule it out... is the car a little jumpy at lower revs and lower boost? BUT what N75 are you using
i dont supose at any point you have or had some one play with your nuts.... on your actuator... it will more than deffo start overboosting if they have been tweeked to much..
has it just started doing it for no reason and out of the blue?
it could be a dodgy MAP sensor... its normaly chucked in to limp for over boosting by the map sensor, there is a resistor mod you can do on them,
my old cupra started kicking in to limp for no reason for about a month, i poped a risistor and solved it, just had to keep an eye on boost, mbc sorted it

 

[brad1]

Thats a good point about the map, the hybrid K04 takes along time to set up and get it perfect with boost etc as they can spike quite high

 

[NottsLCR]

I'll check the DV first then get it tested for leaks just incase. I have the N75J on the car and its fine at low revs.

Actuator hasnt been altered since the Turbo came from CR Turbo's. If its neither of the 2 above then i'll try to check MAP sensor.

Will spent around 6 hours setting the map up and well over 10 runs and the code didint appear once during this, it only appeared a day or 2 after.

Appreciate all the input guys would like it sorting now I've got the Hybrid and other bits fitted!

 

[t32er]

how long has the J been on there?? the caused my LCR to over boost twice then i put a H on there

 

[8bit]

I'll check the DV first then get it tested for leaks just incase. I have the N75J on the car and its fine at low revs.

Actuator hasnt been altered since the Turbo came from CR Turbo's. If its neither of the 2 above then i'll try to check MAP sensor.

Will spent around 6 hours setting the map up and well over 10 runs and the code didint appear once during this, it only appeared a day or 2 after.

Appreciate all the input guys would like it sorting now I've got the Hybrid and other bits fitted!

Cars behave slightly differently on RRs compared to real roads, they're not having to overcome air resistance on a RR so the engine load is higher, also you'll not get the same amount of air moving over the intercoolers and into the intake on a RR no matter how big the fan is, that may explain why the codes didn't appear until later on. ECU controls boost partly related to engine load, maybe with extra load once on the real road it requested too much?

That said there's other people more knowledgeable than me already in this thread so that theory may be off the mark...

 

[NottsLCR]

The N75J has been on the car well over a year.

I haven't got the old one to try so can't rule this out but like I say its been ok for a year or so

 

[NottsLCR]

I took the DV apart this morning after testing and their wasn't much grease around the piston. Anyway when doing the test the piston dropped around 5mm, it stayed open but thought this was quite a big drop?

Put it all back together after abit of a clean up and went for a drive and as soon as i hit about 23 psi the car went into limp. Came home and VAGCOM and same 2 codes are back.