2.5TD - anybody tried increasing the power

[whitehartbookss]

Dear List,

Has anybody tried upping the power of a 2.5 Turbo Diesel XM???

It looks like i'm about to strip an engine, so I might start with new valves and guides, and gas flowing the cylinder head.

Matching the inlet and exhaust manifolds, and flowing them will also help.

I'm not just after top end power, but more torque across the whole of the rev range - esp bottom end pulling power , which afterall is what Diesels are SO good at!!!!

The air to water intercooler looks like it might benefit from a re-vamp!!

If I do have to strip my spare engine - then i'll also balance the bottom end. That should make it run a lot sweeter.

I'm wondering about boost levels and those plug in devices - though the 2.5 TD engine might be a bit too early for all this.

Looks like I might be tweaking the fuel pump.

Jonathan

[AndersDK]

I dont think you can get any more torque below the 2K mark - precisely where the 2.5TD is so impressive. If you can lift your foot before it reaches the 4K mark I'd say this engine would withstand extensive mod to gain in the midrange 2.5-3.5 K torque. Thats exactly where you wanna leave others behind in 5.th on the motorway - the most impressive way.

After all the XM is not exactly born as a racer - but as a very comfortable vehicle. The more torque you can get the more relaxed you can drive.

I think NiSk came out with a very good explanation as why the intercooler is watercooled on this engine.

[Peter.N.]

I dont think you will gain much by gas flowing it as its allready a pretty efficient engine as is the 2.1, similar head. It would be much easier just to increase the turbo pressure/ fueling but, these engines are prone to overheating so dont overdo it!

[whitehartbookss]

I know what you mean about overheating.

Cracked heads on 2.5 seems to be a common problem.
Also head gaskets.

My XM came with radiators with a very low percentage of cooling fins!!!!
So 2 brand new rads immediatley fitted!!!!

As for the idea that the 2.5 engine is already optimised!!!
Please!!!!
All mass produced engines are built to a price.
That is the fundamental design criteria - and it's a great shame that car manufacturers are run by accountants.

I have no doubt that I can get my 2.5 to pull far stronger from tickover to 4,000 rpm (higher revs too - but I want a car that pulls rather than revs, and diesel engines are quite wasteful at high revs - esp indirect injection old smokers like the 2.5).

However - there is a cost/performance curve here.
New valves, valve guides, radius cut valve seats, gasket matching and gas flowing - all take time and money.
My cylinder head bills aren't ususlly much short of £1,000.
We will see when I take it off.

Balancing up the bottom end usually frees up a few HP as the engine can spin more freely with fewer unwanted harmonics flying about the place.

We will see what the new week brings forth!!!

Jonathan

[NiSk]

Chipping the 2.5TD will give you about 35 extra h.p. and enough torque to burn rubber in 3rd gear. And it will only cost you about £400 from a reputable supplier. And your fuel consumption will not deteriorate unless you have your foot in the carpet all the time - more likely is that you loose your flying license!
The air/water intercooler is a mixed kettle of fish - this time of the year it's brilliant, as apposed to all other TD's, which take absolutely yonks to get warm enough to melt the ice on the INSIDE of the windscreen, just give the 2.5 TD a bit of welly and the intercooler heats the cooling water up a treat!

Come the summer though, and you will wish you had something else if you sit steaming in an Italian traffic jam - give it the same welly when you get moving again and all the lights start flashing! Shame there isn't an easy way to combine the advantages of the water/air system with a straightforward air/air intercooler in the summer.

//NiSk

[Peter.N.]

I think the cooling problem is due to trying to put a quart into a pint pot (if you'r not metric) I am on my fourth 2.1 td and although head gasket failures are the norm after about 150k, I have never had or even heard of a cracked head, unlike the 1.9 td. When they redesigned the head for the 2.1, they quite sensibly put the thermostat in the return from the rad, it makes it a pig to change but stops you getting airlocks in the head, which I think was the main cause of failures on the 1.9. The 2.5 has only about the same size rad as the 2.1 and I have never had cooling problems with those, in fact the temp gauge rarely goes above normal.