Turbo low end performance

[piper109]

Car is 300tdi Disco. Turbo is T28 upgraded by TurboCentre to have a slightly bigger turbine. IP has not been optimized but very slight changes tried by me, otherwise stock.

I want to make sure that the turbo is doing the best it can at lower rpm as I have some problems on very steep hills.

My driveway is about 200 yards long and is very steep. If I turn into at a good speed in 2nd gear and hold it to 23-2400 rpm, I can sail up the road in second. If I'm a bit slower turning in and the revs drop below about 2100-2000, its all over and I have to change into first gear. I can scream it in first but forget getting it into second. Once it goes off turbo I have black smoke.

I have read that the engine produces max torque at 2100 rpm and the turbo comes on at 1800 rpm. I would expect it to lug a bit better at lower rpm than it apparently does. Altitude 3100ft.

Am I expecting too much?

I am buying a boost gauge to install. What boost should I see at lower rpm? Is it just going to depend on throttle amounts?

I know a VNT turbo comes on at lower rpm but I'm not ready to sink a lot of money into as the vehicle is great for what I use it for otherwise. I just want to make sure its adjusted correctly and what I can try to improve it a bit.

Thanks, Steve

[disco_al]

to be fair that sounds about right for a 300, once they go off boost they are a bit of a 'mare. your not going to see any gains below 1800rpm from turbo mods, as that is where it kicks in, so you're only really going to get improvements from the fuel/air side of things. i would suggest looking at the off boost fuelling (the star wheel in the top of the IP), which may help. IIRC there is a tuning guide in the tech archive, if not, google bosch ve pump tuning to throw up lots of info - or try the turbo diesel owners forum (sorry, can't remember the link) lots of info on there.

i don't think you're altitude helps too much either

[CwazyWabbit]

I understood that if you put a larger turbo on the low rev performance would deteriorate due to the extra mass of the turbine needing more oomph (technical term that). Now that may just affect acceleration, I don't know.... but it may explain why a 2000-2100rpm drive attack just dies and ends sadly....

I'm sure a grown up will be along shortly to explain all

[discomikey]

bigger turbo = higher exhaust pressure needed to get going

is the diesel pump tuned, try fiddling with that as it can make one hell of a difference and wont affect MPG much at all, in fact i wouldnt surprise if it did more to the gallon as you arent foot to the floor as much.

also get a boost guage and see whats what and if you can adjust it

[Turbocharger]

This is why I went for a VGT - that and I can't live without the endless hassle of a homebrew project that's never quite finished. I've now got 1 bar boost at 1400rpm and pushing 1.5bar by 2000rpm - it's the first figure that makes the driveability work (though I then went and ruined it with an autobox but it tackles the same issue two ways round).

If you're seeing black smoke at full throttle & low revs then you're already overfuelling and you won't get any more performance from the star wheel.

First things first - is the air filter clean, pipe runs not pinched or delaminated, intercooler not clogged with old oil etc.

Get a boost gauge, make sure the wastegate's pinned shut (use a regulated workshop airline to feed it directly, you shouldn't see any movement until 0.8bar & fully open by 1.2bar, don't stuff 10bar into it accidentally because you'll need to buy a new one).

Then, and only then, consider throwing money at turbochargers etc.