Thread: Turbo boost

Well havent I opened up a can of worms!

Anyway, i adjusted the boost up to 17 psi from 15, and like clarky said It didnt make a difference, or I couldnt tell if it did.

Im getting my egt gauge in 2 weeks and then I will tweak the fuel pump as per the aulro forum notes, then I should be flying!

Might even back the boost off back to standard after that, see how I go.

Thanks everyone for their input.

Cheers

Yes Rick, my bad - extra burn time required for boosted charge to burn completely or you see a sudden rise in EGT. 'retarded' was the wrong word. Just need to listen out for knocking if you've gone too far, which is not good for deisels.

Increasing the boost a few psi DOES make a difference when climbing up long hills with a heavy load on. I ran mine at 17 for around 6mths. It's hard to argue against physics yet it seems some people still try.

Also lower EGT's does not translate to more efficient running (i.e. 4th gear versus 5th at the same speed). In 5th the EGT's may be higher but the flow-rate of the exhaust gas is lower (less RPM and less gas volume). I think like others have said, deisels are most efficient near peak torque, which according to the book is around 1800 for the 300Tdi.

Originally Posted by PAT303

When you blokes talk about tweaking the pump,is that the stop screw or timing?.If it is the stop screw how many turns did you do,1 or 1 1/2?. Pat

Pat, there are four adjustments easily accessible on the pump. I suggest you read this http://www.aulro.com/afvb/attachment...6&d=1152411367
It's in Adobe PDF and is a brief overview of how the pump works and step by step adjustment of the pump.

Originally Posted by rick130

I would have thought there is a direct correlation between BSFC and EGT's ?

mustn't be as clear cut as I thought

Basically the higher power you put out, the lower proportion of engine power is going into internal engine losses.

Here's another bit to chew on. I just got my exhaust backpressure gauge installed again. Backpressure starts out at twice boost and drops as EGT's rise.
650 deg C is the point where boost and exhaust backpressure meet.
I get 20psi boost and 20psi backpressure. That's pretty good for efficiency.

Here's a VW 1.9TDI BSFC map.

Thanks Dougal.
Curious where you've sited the port/tapping for the pressure gauge reading.

I'm guessing pre turbo to get a 'true' reading. Would also be the easiest spot for me on the Tdi to drill and tap a connection in the EGR blanking plate alongside the thermocouple.

Originally Posted by rick130

Thanks Dougal.
Curious where you've sited the port/tapping for the pressure gauge reading.

I'm guessing pre turbo to get a 'true' reading. Would also be the easiest spot for me on the Tdi to drill and tap a connection in the EGR blanking plate alongside the thermocouple.

Yep, about an inch before the turbo mounting flange. I've got the thermocouple in one side and the pressure line in the other.
I plan to put another pressure/temp tap point in the dump pipe just downstream of the turbo too. I've only got soo many gauges, but I can swap the probe position easily enough.

a couple of rough boost observations (I looked at the boost gauge just down the road from the home office, it's a late lunch )

I dropped it into 4th at 50km/h up a small rise and flattened it, full boost (16.5psi) was achieved at approx 62km/h indicated.
I'm running worn out 255/85/16's.

I'll work out the approx. revs soon.