850 tdi POWER!!!!!!

[brickman]

Egr has been blanked for a year now as it was seized partially open.

Bcv solenoid would explain the way it behaves. How have you bypassed it without throwing codes?

It's plumbed the right way, tried the reverse to make sure that the labels on it were not the wrong way around and it wouldn't boost at all.

[martin_r_smith]

1. That bit of extra pipe won't make a difference
2. As Troublemaker says, it's not a bleed valve.
3. No you don't need to disable the bcs, but you can it will work either way.
4. My guess is your plumbed in wrong.

When you fit the mbc, if you have it almost screwed right out your boost should behave normally. The more you screw it in the more pressure is needed to move the ball inside the valve and thus increase boost. Make sure all the pipes to the actuator are connected still, especially the one in the center, and try it with the mbc unscrewed. This should be back to normal. Then try screwing it in a turn at a time and it should increase boost. It may take a few turns so maybe do 3 to start with.

[martin_r_smith]

Thinking about it you say you tried it the other way around and it wouldn't boost, did it maybe boost to 7psi? And was the the screw in or out?

If yours is like mine then the pipe from the compressor housing goes in the bottom of the mbc the the top one goes to the actuator. As the boost increases it has to push the ball up to be able to let the pressure through to the actuator, hence screwing it in increases resistance allowing the extra boost.

[brickman]

Should I just blank off the bcv pipe to the wastegate so it thinks it's controlling it, but actually it's going nowhere?

It's reverse threaded this one, screwing it in the way appears to reduce available boost to normal spec, but as I say, with a lot of time spent building boost.

[martin_r_smith]

I've never come across a reverse threaded one to be honest.

As I said there's no need to blank it it will work fine with it connected. Try blowing through the mbc, if you wind it in does it really reduce pressure required to open it? Have you got a link to the one you have?

[thetroublemaker]

That dosent make sense. But i am happy to stand corrected if there is a different version.

On my car with the BCS in the circuit i was getting weirdness. I would look at the below and replicate it.

[brickman]

Mmmmm something is a miss, just tried it screwed down hard and above 3k it will get 18psi, but again tail back off to 13/15psi pretty quickly, so bcv must get the issue, or is it....


Just tried leaving the pipe work open to atmosphere on both sides of the mbc, and no change, still spiking 18 then rapidly being reeled back down, so the mbc is doing next to nothing?!

My issue must be with either the bcv or wastegate, or even the plumbing between these two.

[thetroublemaker]

Boost control solenoid could well bleed off boost if the wastegate spring is weak.

Bypass it as per my diagram above.

[fuller0554]

Hi guys, great thread btw, iv just finished reading through it all. I think im getting the general workings right. Im getting my belts pullies and some upgrades done soon before i star playing with my engine, mainly brake upgrade and new struts all round but does any one have some pictures of a working setup of there mbc as this would be great help when it comes to setting mine up as im sure it will others too. Also it was mentioned earlier on in the post by martin i think, that he is useing a programable ecu? Do you mean a mega squirt unit or similar or is it a chip you have put inplace of another in your ecu which allows you ecu to be flashed as and when you need to.
Iv been talking to a guy from sweden for a while now who programmes chips for volvos for a living and does it for older cars to make some pocket money, i think id rather go this route as i would think a programmed chip would be more prossice than a box and probably be healthier for the engine to but thats just my opinion.
A friend of mine has a tuned 850 auto with somewhere around 200bhp and he has a turbo from a vw transporter fitted, (same 5pot 2.5 audi block but as stardard they are fitted with a bigger turbo) and hes also had a map done, well his friend did before he sold it to him. I didnt get chance to ask in more detail what had exactly been done but you can be sure il b picking his brain next time i see him. Has any one else though of going down this route or know some one who has?
Ok think that enough for one post :-). Sorry i know its alot to try and answer but im abit engine crazy and could waffle on for hours. Many thanks

[thetroublemaker]

I would be interested in finding what turbo this was - I was unaware that they used a different turbo on the t4's and the R5 engine is completely different that has a vnt on it iirc....the volvo is the 140 .205 injectors version which is the bigger of the 2 audi blocks.

Setup is exactly as per my diagram., setup Is exactly as per your boost gauge for the mbc, increase fuelling however you want then add boost to clean it up. 90% of the gain is fuel related the boost only gives a little extra.