What turbo is it on there?
Looks like a Garrett T25 on my 200tdi which would be fairly useless for anything over a bar. I know the T28 can run about 1.2bar before it just starts heating the air. Both fairly familiar tubbys to me as they are what's fitted to the rs13 and s14 200sx's respectively (been a member on sxoc for a while now).
Has anyone done enough extensive testing on these engines to find out exactly where the weaknesses crop up? As in, at what point is the exhaust too restrictive, when do the pump and injectors struggle, what boost shreds the HG? It all seems remarkably "try it and see" at the moment with a few people who seem to know the answers :shock: :D
Depending on the spec, a T25 can run a 14/15psi before it starts it going past it’s max efficiency point, and as mentions starts heating up the intake air… it will still run a max of about 17psi… but there will be a trade off between heating the intake air, and volume of air supplied.
Although not the best situation, in some applications it won’t make that much difference.
If your doing prolonged high speed running, where your making the turbo spinning near it’s max rpm, and running higher than standard boost, the intake in air temperature will rise considerably and this will effect the intake air (and on a petrol - especially - will cause problems!!)
This can be overcome by running a bigger intercooler, in the hope of chilling the intake… but really if you’re after max power it’s not the sort of thing you want - as ultimately performance will still suffer (the point in which the heating becomes detrimental will be raised though with a larger IC)
However, in a Land Rover application… off road you generally only want quick squirts at max power, and often the turbo will not be running at max boost for that that long.
So although not ideal, the performance gain you can get by running more fuel and boost should easily mask the power lost by allowing the intake air to be heated slightly by the turbo.
Weaknesses is an interesting issue…
There are people like Jeremy Fearn (JF), JE Engineering and Allisport who have (and still do) work on 300Tdi’s (and 200 Tdi’s). What you do find is that for road use none of the then increase the boost pressure above standard on a 300Tdi…however off road usage is a different matter (different ‘customers’ attitudes to engine longevity and usage) and AFAIK JF does increase the boost to anything up to 18psi… but usually with a hybrid turbo.
I’ve known numerous people run 17 and 18psi (up to 20psi) on 300Tdi and have not had any issues with HG failures… however some 300Tdi suffer HG failure even with a standard set up. A lot of it comes down to engine servicing, and how well the owners look after there cars.
What is fine on one engine causes quite a few problems on another!!
If you want to start running over 18psi you will have to look at wiring the block, and be prepared for reduced engine life.
Injector and FIP wise….
Injectors shouldn’t have a problem supplying the necessary fuelling.. I know of Tdi’s that have been knocking on the door of 200bhp still running standard injectors (albeit proper matched ones)
FIP though, if you start running more fuel and boost you will get to its limits as a standard set up. However, you can get bigger internals and even upgrade to a larger FIP from (I believe) a Jap 4x4.
The upgrading of the fuel pumps is something I’m looking into at the moment.
From standard the exhausts are restrictive especially the silencer box design on 200 and 300Tdi Defenders. Even just removing the silencers makes a marked difference. Better still would be to go for a 2.5†exhaust system, there isn’t really much point going to anything bigger IMHO.
In reality the tuning of 200Tdi and 300Tdi’s is a bit old hat now, most people have moved onto TD5’s.
Ian
