Thread: 300Tdi boost pressure - how much is enough?

Originally Posted by Leo109

But is this for an otherwise standard engine - or a competition truck with steel-topped pistons, ported head, bigger turbo, bigger intercooler etc. etc. etc.

He's pulling your leg.

You can't boost a standard 300TDi much more than the factory set level of boost. I believe and am happy to be corrected that 18psi is about the max level of boost you want to see if you want set and forget reliability. I replaced the turbo on mine a couple of years ago and it came set to max out at 16psi which is where I left it.

Run too much boost and you'll blow head gaskets.

I have read about people over-torquing heads to provide more clamp-down on the head gasket to run higher boost but that doesn't strike me as being a good solution for people wanting a reliable engine.

So, if it's stock, err on the side of caution and keep it at 18psi or less.

kindly keep your opinion to yourself and do not inform my stock gasketed stock internaled and stock bolted ti300 that it cant run 30psi... The only reason I cant keep it there for prolonged periods is cooling, the standard radiator just isnt up to all the heat I want it to off load. especially up in darwin

the most you'll efficiently get out of the stock turbo, intercooler, hosing and exhaust is around 21/22 you can push it to 26/7 but you're going to burn exponential amounts of fuel and will be pushing the heat and design limits o the turbo (the td04 or the 2.8's VVT are much better replacemetn options) and he main reason you dont often run past 25psi do it is more to do with fuel, road, driving conditions, and practicality than the inability to do so.

once of the better things you can do is wind in the waste gate actuator without messing with the fuelling.

if you havent already done so the first mod I reccomend and put on for most people looking to tweak a tdi is to move the feed for the wastegate to the inlet manifold and plumb a boost gauge to the same spot.

Yes, but your 300TDi is special The owner of mine is somewhat less talented.

So the answer to this question;

"By the way any thoughts on how much boost (and associated fuel) a 300Tdi can handle and still enjoy a long life?"

is actually 21 - 22psi

Is there much to be gained going from stock levels to low 20s psi with the pump tuned to suit?

I have been considering moving the boost compensator line to the inlet manifold and fitting a boost gauge. Just not sure where to put the gauge...

There's nothing particularly special about my tdi,

a tdi will handle 30 psi on stock bits, thats the safe limit, much above it and you blow the inlet mainfold gasket peak 35 and it'll fail almost instantly

the biggest issue with going past 25 is the overall efficiency of the turbo going past and holding 30 is the total heat production of the engine exceeds the cooling systems ability.

over coming the inefficiency of the turbo needs an exponental amount of fuel and exhaust pressure which means high EGT's which is the initial limiting factor for the TDI. getting past that is easy, use a better exhaust, and better intercooling to get more cooler air in and faster extraction and if you really want to find the next limit you need better turbo charging.

Once you have that in place the next limit is the overall ability of the cooling system (which for short periods you can ignore so long as you let it recover)

once you beat that its your inlet manifold at 35

when you beat that its a toss between the head gasket and the haed bolt clamping, at a guess at 45 psi (thats as far as I got before I hit instant manifold failure)

when you beat that its the pistons integrity and underside cooling which I guess will be around 50/55

once you beat that at a guess it'll be your rods or the stack thrust exceeding the wedge pressure of the oil in the big ends and mains causing bearing scuff failure, over heating and seizing

then by that stage you'll be looking at low comp pistons otherwise you'll be exceeding the pressure integrity on the valve recesses or injector orifice. or maybe the integrity of the bore but by then you're going to want to be looking at skirt guide rings or tefloned skirts and hell, are you sure it wouldn't have just been easier to retrofit a better engine or are you just doing this because you want to see eactly how far an engine can be made to go?


My engine is dangerous for someone who will ignore gauges and idiot lights and warning bells and drive it by just burying the boot and holding it pinned at all times. The really nice thing about turbo diesels, especially old school ones is while you can tweak them up so that they can self destruct them selves they will only ever push out as much as you ask them to.

just because you have an engine that can handle 30 psi doesnt mean you have to make it do that...

Remember the original question was what CAN it handle not whats economical and easy to do.

the tdi300 (and this really applies to all engines) is a very capable little engine but it cant do everything I don't think I've ever tweaked up any two of them the same because every owners opinion of what it should do is different to every other owners opinion.

do the opening mod of rerouting the waste gate actuator pick up first, see what you think of that, then fit a boost and EGT gauge and learn how its reacting and then start thinking about modding it.

generaly and vaguely most people wind up with about 19/20 psi on an extra 1/4-1/3 of a turn on the max fuel screw then the compensation adjusted to suit.

FAIR WARING.
getting there is not as simple as that last paragraph just read.

Originally Posted by Leo109

Gees Dave, aren't there any other options?...

He forgot Rapid Fix.

hi
30-35psi sounds like it would go very well.
Is that through a snorkel?
I have a snorkel and seem to drop a couple of psi of boost at high revs,
not sure if its normal or not.
Mine runs 17.5-20psi with a boost controller that's supposed to hold wastegate shut till 8psi.
It does seem a bit quicker in the traffic.
That's nothing compared to 30psi though, must go like a rocket.


Do your intercooler hoses last at that boost?
Cheers

the silicone ones do yes.

in honesty 30 psi was only a side effect of what I was setting out to achieve. but the bug bit so lots of research was done and some engines were experimented on.

unfortunately due to the divorce the money ran out after I got the boost sorted but before I got the cooling system squared.

That's an impressive amount of boost , I'm in the process of wiring up a boost gauge (in manifold aswell as the waste gate feed ) and Egt gauge and water temp gauge but procrastinating more than I'm working . I too want to get a little more out of the engine , blknight what is ur boost pressure when cruising at 100km/h heading to town ? Would it still be around 10psi on flat road