406oc.co.uk

Hi to everyone on the Forum from the newbie.

History - 405 DTs (about 4 of them) 405 MI-16 Le Mans - For fun a little Fisher Fury with a Fireblade motor. 460kg - 130 bhp @ 11k with a 6 spd sequential box, low gearing, makes me smile.....

However, I now have a 406 SRI with a single point closed loop LPG conversion. I put 40k gas miles on it over the last 14 months, but now the engine is sat on the garage floor with 100,49,80,80 psi on a compression test. Putting oil down the pots didn't lift the pressures. The motor only smoked abit on tickover, was otherwise smoke free. Anyway, Hiflow Heads are putting another motor together with MR2 turbo pistons (I gather they fit!), and all sorts of new bits. I don't know too much about turbos, especially a wierd French one!

1. In my haste, I didn't take pictures! Most of the pipes I can sort out, but could someone post a few close ups of an engine bay as a reminder?

2. In the hot weather last summer, I got intermittent full boost then no boost. Since the autumn, no problems. Wastegate? Actuator? Recirculation dump valve sticking open? Should I be worried? The turbo spins OK, no oil leaks, clip missing off actuator lever to wastegate, that's all I can see. What jobs would you do to the turbo? Can I, should I do a DIY recon job on it?

3. Can't follow the Pug boost control system at all! The actuator is connected directly to the turbo intake pipe - so it works on a vacuum!? What is the boost solenoid doing and how - where is it Does the ecu allow the wastegate to drift open at low boost? I was hoping to fit a GB Enterprises boost controller to hold the wastegate fully shut before full boost - but it was designed for +ve pressure actuators.

4. I will replace pipes and clips around the turbo. But some of the small plastic pipes have broken. Folk say fuel pipe will hold off 30psi - Can I use that rather than expensive Pug bits?

5. Has anyone any experience of FSE Fuel pressure valves - do they work on an SRI? (for the time I'm not on gas).

I could go on - but may be I'm pushing my luck - if anyone could help out ( and with the pictures) I'd be grateful.

Hi fella,

Sounds like the 'Gas' has goosed your engine to me.

You need 'Niz406' on here, he's had his car in bits more times than anyone.

Thanks for the reply, Welton.

You could be right - the gas needs to be checked and there's a guy not too far away that supposed to know how to test it. It is supposed to look at the lambda sensor, look at the boost and work a little stepper motor to give the right mixture. But gas does burn hotter, and despite knock sensors etc, and might have goosed it.

But gas is only 39-45p/litre and it does 25mpg on gas at 70, and the company pays 40p/mile!

Niz406 - where are you?

i see endless problems with aftermarket lpg systems at work, as the gas is less dense than the petrol it seeps past the piston rings allowing the rings to weat prematurely, it also destroys all the oil seals and raises combustion temperature to the point were pistons can get melted, the first sign of this happening are permenant knock sensor faults, then the engine just runs like shite, and has no compression

You're starting to depress me!

Actually my mechanic complains bitterly when he gets MOT failures in which have been running on gas and have failed emissions on the petrol side.

His comments were the same, the gas burns hotter affecting proper lubrication and combustion. Petrol acts as a very affective in-cylinder cooling medium.

Still, with the money you've saved on gas you can buy a new engine (sorry)

Hi and Welcome Just40in,

Sorry for the delay, only just stumbled across this post, i'll try and answer as much as I can.

Pictures I can do, I've just been really, really busy recently and not had much time to do anything!

1) Only charge pipes or breather as well?
2) My Guess would be the std recirc valve, I used to suffer this many years ago when I first got mine. Turbo wise you can stick a 360 degree thrust bearing kit on it, add a T28 Compressor Wheel and cover ( requires balancing ). Install a -31 Actuator or similar and fit a ported Exhaust Manifold. These will all help increase your turbo's response and flow rate. Lower charge temps from same boost levels but increased density = increase in output!

You can recon it yourself if you have the tools and some mechanical knowledge, its amazing how much places charge for what they actually do!

3) Pug Boost Control System is Fantastic ! No seriously it is, its so clever!

The boost is controlled both RPM and Gear Based, the idea of this is to keep traction available in the first two gears. e.g:

1/2 gears 4-6psi
3rd gear 8-10
4/5 10-12 max

No boost is sent to the actuator until such a time that the boost exceeds the set rpm/gear limits, then depending on the rpm/gear a percentage of boost will be directed to the actuator upto 6700rpm ( 0.9bar max std setting ), over this all of the boost is directed onto the actuator ( boost drops to 0.3bar ). When the detected boost ( MAP sensor reading ) is within normal range the charge is redirected back into the intake system.

The ECU shouldn't allow any boost to cause wastegate creep, unless you have a faulty WCS ( Wastegate Control Solinoid ) located on the drivers side suspension turret. Brown Plug. These are a common failure on the Turbo petrols. A weak spring setting on the actuator can also cause the wastegate to creep. Fitting an uprated actuator and bov will improve boost response.

The Stock Actuator is a +ve boost application, actuator pot fills with boost... diagphram pushes spring loaded cup inside which pushes rod and opens wastegate!

4. Which Pipes have broken? Pictures ??

5. A rising rate FSE Fuel pressure valve does work on the SRi, but I wouldn't bother unless you plan on increasing the standard boost levels.

Pictures wise, just let me know the hoses you need and i'll sort something out for you

Thanks Niz406 for the reply - extremely helpful.

It's all a bit of mess under the bonnet - The WCS has the front connector snapped off! I found the actuator connected directly to the plastic airfilter to turbo duct, under vacuum (hence my confusion). The wastegate can never have worked then!

There are 3 connections to the WCS - front, back and downwards

Front - to plastic airfilter to turbo duct ???
Back - to wastegate?
Bottom - to inlet manifold?? Is this where the actuator picks up +ve boost pressure?

(due to time, and because I could prise the thing apart etc, I gave the turbo to T. Technics as there were some very wobbly bearings - they've sent it back all nice and tidy - they did want paying. Motor is a bit of a parts bin - MR2 Turbo pistons (laying around the workshop), long throw crank to get the CR up from 7.4 and now 2.1 litre - all I asked for was a rebuild! Due to be delivered Tuesday)

No Problem, were all here to help where we can..

I take it you are going to replace the WCS before putting it all back together?

The 3 connections to the WCS are:

Front - Turbo intake ( black Plastic Pipe which connects to airbox )
Back - Wastegate connection
Bottom - Inlet pipe from Intercooler outlet to inlet manifold, and yes this is the +ve feed for the WCS

It takes a +ve and vacuume feed to read differnences in charge pressures from the turbo's inlet to the inlet manifold, obviously if the air going into the inlet manifold is less than the air being drawn in to the turbo then the ECU adpats to this change and see's a potential fault.. i.e. boost leak! Here it will try and prevent overboost which could result in turbo damage( wobbly bearings ). lol

Just out of curiosity how much did T.Technics charge you and was it just a rebuild? or did you have anything added?

How much has your engine cost you from High-Flow heads?

T' Technics charged £385 (ex vat) for remaking the turbo with new parts where necessary, balancing, actuator test and adjustment, new rod end and reassembly in manifold.

Hiflow charged £1,500 for the 2.1 with MR2 pistons. If it lasts 4 years and 100k + miles, I be happy enough. It's got a s.steel exhaust anyway, and all sorts of bearing, suspension arms, master cylinder, handbrake shoes replaced. In for a penny, in for a £ now. May as well get the thing right.

Thanks for the pipe connections, all clear to me now - I'm getting a new wastegate control valve. There are cracked plastic and split pipes all over the engine bay. No wonder the motor was struggling!!

after all this you might want to ditch the lpg and save yourself all this hassle again

Hi

Sorry to invade your thread but quick question. I don't suppose anyone would know what was required to get those MR2 Turbo pistons to fit? I would imagine they're pretty strong which is just what i could do with given how hard I drive it.

Thanks
Andy

I don't think there is a problem fitting them, (according to Hiflowheads) it's just the very low compression ratio (maybe not a bad thing). I understand mine is up to 8.7 with the long throw crank.

(It still hasn't arrive - sleeping couriers)

i read somewhere that you can also fit vauxhall c20let pistons but im not sure if this is true