Thread: VNT Turbo Setup??

Yep - mechanical gauge. Not overly concerned about it as long as other people have the same issue Will put a restrictor inline and see how she goes.

I had t bolt clamps and plain stainless pipes, never blew one off

I can tig some beads on if it's not clamps to loose, seeing as my nuts are healed and I can do stuff again

Originally Posted by mike_ie

Well, we've sorted out a couple of fuel pump issues, ...

If you have time, what did you sort out with the pump - an earlier post from Vern mentioned surging - so if you did something that fixed this, a few others would be interested.

Originally Posted by mike_ie

...
With the VNT vanes fully closed (vacuum actuator on full vacuum), I'm getting 20psi uphill and about 450°C. What values should I be aiming for? Bearing in mind that this will be used for travel, not a weekend hill climbing competition rig

Firstly, you want the vanes to open, not shut at that boost pressure. Open vanes reduces the pressure in the exhaust manifold.

Too high exhaust manifold pressure increases pumping losses - power reused to pump out the exhaust under higher pressure. And higher boost pressure is required to move the same mass of air through the inlet port during valve overlap.

Get it right and you can achieve same power/torque with less boost pressure and less fuel.

Similar applies when boost pressure is higher than needed to get the air mass flow for the amount of fuel you are injecting.

Back out the adjustment on the Dawes valve, and use same hill for testing and note how performance changes with boost pressure. Once performance drops dramatically screw it in a little.

Remember the setting of the Dawes valve is controlling the opening of the vanes.

If the turbine is not oversized (I don't expect it would be, unless I'm confusing your VNT turbo with others in some other threads I read recently), with the vanes fully open, boost pressure will increase further as the load and fuel being burnt increases the energy in the exhaust gasses - this is where your measurement of EGT is your best guide.

If EGT is low, <650C, when the engine is seeing maximum load, then fuel rate can be increased, or boost pressure lowered, or both. If EGT is too high >700C, increase boost pressure to get more air, or reduce fuel. Remember also high EGT makes the turbo more efficient (good), just don't go too high, for too long, for the sake of the pistons, etc.

It is possible you are getting transient boost pressure much higher that what the boost gauge is reading. This might be one reason you are blowing hoses off - unfortunately other issues, like the oil, can still be contributing.

IMHO, you should put some effort into getting the vane control system operating smoothly, and the vacuum actuator lifting off the stop screw early (moderate boost pressure). Use you seat of the pants dyno in conjunction with what the boost and EGT gauges are revealing.

John, thanks for the feedback. I've been reading up on how to set up these turbos for a couple of weeks now, and this is probably the most concise and straightforward explanation I've been given so far. Much appreciated.

Originally Posted by rovercare

I had t bolt clamps and plain stainless pipes, never blew one off

I can tig some beads on if it's not clamps to loose, seeing as my nuts are healed and I can do stuff again

Might take you up on that. Steve's suggestion of spot welds at 3,6,9,12 o'clock positions seems to be a good one.

So roughly what figures have you ended up with for boost and EGT Mike?
I realise that you're not able to fuel it up fully due to the hose issues, but would be interesting to know what you're currently at and how close that is to max fuel. Would be great if you could get some figures from a rolling acceleration in top gear from say 60k's (or whatever speed its comfortable to pull from) ie boost/EGT at 60,70, 80 etc with foot flat.

I'm still surprised that your not running into issues with the exhaust flow given the large drop in EGT that I had with my conventional turbo when I went from the 2.5" to the 3". I really felt that it was going to start to choke up on you, but seems that's not the case which is great. Confirms I don't know squat about how everything interacts

Are you running any sort of air filter service indicator? Would be very interesting to know what restriction you're seeing prior to the turbo.

Steve

down load G-Meter on to your phone and post the results. its how i tune 300 and 200 TDIs