LCR 249 Bypass

[cuprajim]

Right, I have read and researched and now, as the cows have just arrived home, I need clarity.

Looking through the 'how-to's' and the gallerys, the only information and pictures available to bypass an N249 valve is for Ibizas or 180 Leons.

Is there anything that I need to be aware of for an LCR? The bypass unit pipework looks considerably different to the pictures on SCN. Has anyone completed this mod on an LCR sucessfully and noted any difference in partial throttle performance?

Also, has anyone got any pictures of the mod on an LCR?

As I can determine the following would be suitable:

1. Remove DV signal pipe and block.
2. Cut a T-Piece into FPR line (a'la Boost Gauge)
3. Run a new piece of 4mm hose from T-Piece to the DV.

Job done???

 

[cuprajim]

I cannot believe for one minute that no one has tried this on an LCR?!

Anyone out there with some finite guidance?

 

[karlosR]

i had it done on mine and it did make a difference to throttle response. i took it off after a session on some dodgy rollers where the operator didn't know his arse from his elbow. i'll be putting it back on when i remember where i put it. send a PT to alex (TTS roadsport) or post in their section of the forum to ask whats involved.

 

[DPJ]

I've removed EVAP, N112, SAI and N249 - but hey, mine's only a lowly LC.

 

[karlosR]

at the TTS/backdraft open day on saturday there was a BT TT that had everything removed and was running a manual boost controller in place of the N75 valve. it looked a lot tidier on top of the engine with everything gone.

 

[cuprajim]

Right, done this last night.

The definitive guide to LCR N249 Bypass.

Piece of p*ss really. 10 mins max. A bit Heath Robinson but will be tidied up when I can be bothered.

1. Remove Engine Cover
2. Remove hose from the top of the DV to the N249 valve completely
3. Cut a small piece of 5mm ID hose (approx 3" long), stuff a 5mm bolt in the end and cable tie it.
4. Attach the blocked piece of hose to the outlet of the N249 valve (where you removed the DV hose from) and cable tie or jubilee clip in place.
5. Cut a new length of 5mm ID hose to go from the top of the DV to the Fuel Pressure Regulator hose.
6. Attach one end of the hose to the top of the DV and the other end needs to be cut in to the Fuel Pressure Regulator hose (a'la Boost Gauge) with a T-Piece.
7. Crack open 3rd celebratory beer.
8. and another, hic!

Materials and Tools required:

Beer
Flat Blade Driver to remove engine cover and to prise off hoses and tighten jubilee clips
Sharp cutters or Stanley Knife to cut pipe and dress cable ties

Length of 5mm ID hose (Halfrauds)
T-Piece (Halfrauds)
5mm bolt (Floor of Garage)
Cable ties and jubilee clips as required.

No difference in power; however a lot smoother in mid throttle delivery and part throttle lift off.

CAVEAT: There is a downside to all this 'DIY', Darth Vader under the bonnet is now LOUDER, much to my dismay. How a closed loop dump valve can be so bl**dy loud is beyond me. The car sounds more akin to a CVH powered Southend Chariot.

AIII, booyakka.

 

[bud-weis]

i'll be totally honest and say i have no idea what the N249 is lol.

Any pics? ( i've seen the other threads too, but no LCR pics ).

On the airbox to turbo inlet pipe i have a bailey recirc' dump valve, and a standard looking valve ( is this the N249? )

 

[cuprajim]

No the N249 is below the engine cover just above and between Cyl 3 and 4 coilpacks. It is a square Valve with a network of pipes, a Non-return valve and a Vacuum Reservoir.

I will try and take some pics tonight if I can make it past my beer fridge. Damn that beer fridge!!

 

[DPJ]

No the N249 is below the engine cover just above and between Cyl 3 and 4 coilpacks. It is a square Valve with a network of pipes, a Non-return valve and a Vacuum Reservoir.

.............

the vac reservoir is above coilpack 4.

 

[bud-weis]

Thanks...i'll have a Pat Butchers tonight

 

[andycupra]

so i presume the original vac reservoir is there to aid the operation of the DV?
removal of which would in theory slightly increase the possibility of issues with a non operating DV? which may or maynot be offset by having a better DC fitted?

 

[DPJ]

so i presume the original vac reservoir is there to aid the operation of the DV?
removal of which would in theory slightly increase the possibility of issues with a non operating DV? which may or maynot be offset by having a better DC fitted?

- or the vac reservoir is there to be used by the ECU to control the DV when there isn't vacuum............ / when it wants the DV to open........

 

[andycupra]

- or the vac reservoir is there to be used by the ECU to control the DV when there isn't vacuum............ / when it wants the DV to open........

oo interesting... so if a car was used with little throttle and accelerating slowely the DV appeared to operating alot for no reason this could be due to a hyperactive ecu?

 

[DPJ]

I wouldn't quite go that far... when accelerating slowly you wouldn't have boost to dump, but I think there are circumstances when the ECU will decide to dump that are less than necessary.

 

[andycupra]

ok... issues ive seen happen when there is no vacuum or boost. (ie gauge is at zero). It just doesnt seem to make a decision as to what its doing.

anyway getting off topic now, ill get a slapped wrist by a new mod...

 

[DPJ]

ok... issues ive seen happen when there is no vacuum or boost. (ie gauge is at zero). It just doesnt seem to make a decision as to what its doing.

anyway getting off topic now, ill get a slapped wrist by a new mod...

Nah you're on topic, f*** them.

 

[cuprajim]

For reference, pre- Fly-by-Wire Throttle days, all DVs took their signal from the vacuum direct from the inlet manifold.

i.e. when there was pressure against the throttle body, it was dumped by the action of a closed TB creating the vacuum in the manifold.

The N249 allows a vacuum to be available regardless of TB position and relies on the ECU to judge when the DV should be opened. This can be problematic on mapped cars running higher boost as part throttle actions can appear jerky as the boost is dumped earlier than a fully closed TB.

By bypassing it and relying on the inlet manifold vacuum to Dump Boost, 'seems to' eliminate the jerky part throttle feel (in my recent experience). I can't think of any dangers this will cause to the engine apart from if you get Boost Spikes (Overboosting) where the N249 would be able to regulate this regardless of TB position.

I am fairly new to all this, so my understanding could be slightly wrong here, I am free to be criticised on any innaccuracy.

 

[bud-weis]

i'm fairly sure i've done this correctly...but i now have an engine warning light illuminated! lol

 

[andycupra]

is it stil plugged in?

 

[big eck]

Sorry to dig this thread up but does anyone have any pics to show where the parts are on how to do this???

Also is there really a danger doin this mod on a remapped car???