turbocharging

S&D,

Wow ! A can of worms opened here ... (smile)

I can give you some food for thought ......

Adding a turbocharger to a naturally aspirated engine is fine if certain basic facts are adhered to and then compensated for .....

1. Air in ...

Fact : Compressing air heats it up !! Hot air is thinner than cold air. Hot intake air causes detonation if not compensated for.

A naturally aspirated engine on a summers day will be drawing air at under bonnet temps of say 75 deg C ... if it has a cold air intake (snorkel etc) it will be drawing air in at ambient .. say 35 deg C.

If we now turbocharge this engine the air reaches the turbo at 35 deg C from snorkel and is then compressed which raises the temp markedly. Some turbos heat the air less than others and the term is called Adiabatic Efficiency. I have seen air come in to a diesel turbo (pre-turbine) at 35 deg C and then at the engine intake manifold we measured 130 deg C !!!!

This is why turbo engines are intercooled ... the intercooler sits between the turbo and intake ports and cools the hot air from compression back to a reasonable level for delivery to the engine. An intercooler can be responsible for 10% of engine power by bringing the air density up for delivery to the engine. More air in (denser for a given volume- cylinder fill) the more fuel can be burnt per stroke .. giving more power per stroke.

If going aftermarket turbo an intercooler is a must in my opinion and is pretty well standard fitment these days.

2. Fuel in ...

Now that we have air going in under pressure (around 7-17psi) and it is reasonably cool by comparison we need to fuel it to the ideal fuel/air ratio for combustion. This might not necessarily be adding more fuel in the case of a diesel because a fair proportion of the fuel in a diesel is unburnt.... but it usually means a recalibration of the fuel metering.

Ideal diesel motor fuelling comes from exhaust gas temperatures. Go outside the range by fiddling with fuel pumps and or adding a turbocharger and you need to bring it back to safe levels. If it was mine (especially as this engine was going to tow a 3500kg van and be on boost a fair bit) I would be taking sample EGT's from the standard motor and then again after fitting turbo and recalibrating fuel and adding towing weight.

There is a max temp for diesel engines before serious damage is done. It can be a simple blade deformity on the turbine because it goes soft with too much heat and bends backwards (wont compress air well then) ..... right up to etching an exhaust valve or melting a piston.

My limit is 1200 deg F, EGT measured at exhaust port ...and I back off !!!

3. Cooling

Making 25-40% more power in an engine places a much greater load on the cooling system. A larger radiator ( preferably aluminium ... 25% more thermally efficient) should be on the drawing board. Possibly a fan size change ....need real world testing in summer towing the load to be sure of the airspeed through radiator. Air-con condenser in front doesnt help either ... intercooler goes in front of condenser and radiator also .... almost going backwards here (smile) !! Radiator upgrade is a must IMO.

Last but very certainly not least ...

4. Drivetrain wear ...

The naturally aspirated engine drivetrains might be somewhat smaller than the components used in the factory turbo diesel. Increased power through the drivetrain, especially towing, might prematurely wear the drivetrain components. Not sure on this one as I'm not familiar with vehicle that intimately. Worth a mention though ...

Heaps of these conversions are done so these areas might be covered well by the various people doing the fitting. I would be asking questions though and looking at some data from the conversions ..preferably from a dyno ???

Its an expensive outlay and you dont want problems down the track from drivetrain failure or cooling problems.

A naturally aspirated diesel toyota and a turbo diesel from toyota are very different beasts ...technically and pricewise for a good reason.

Anthony

Stephen & Deborah

I agree with Anthony and would like to offer my simple experiences having had 5 landcruisers in the past 25 years.

1980 60 series 4.2 diesel (naturally aspirated - sluggish but reliable, 170,000km. Limited towing of box trailer, horse float and 600gal. water tank trailer (4 tonne - on-farm only). NO PROBLEMS.

1986 70 series 4.2 factory turbo 180,000km. Increased towing usage, larger box trailer, Horse Float, water tanker, ski-boat trailer, 16ft Franklin Caravan and, a lot of hard work in sand. Great vehicle - NO PROBLEMS

1992 80 series 4.2 with Schwitzer after-market turbo, 145,000km. A better performer than the previous vehicle. Similar towing work. - NO PROBLEMS.**

1998 100 series 4.2 with DTS Dynamic Turbo 165,000km. Not as good as 80 series in towing ability. Picked up BT in June 2002 and became an 80km/h traveller. Yes, a bit sluggish on the hills. This was not an intercooled turbo and I believe it was producing about 135kw. I have been told an intercooler will produce about 12% more power. The vehicle worked hard and I towed BT about 8000km. NO PROBLEMS with motor or transmission.

Before changing to my present 100 series V8 petrol, I test-towed the BT with both a 100V8 petrol and a 100 series with a 6.5 litre Chevvy V8 intercooled turbo added, complete with high ratio diff. The chevvy was better all round but the $20,000 could not be justified in adding it to a vehicle that had 150,000km on it already. So, we went for the V8 petrol and now are a little sorry for two reasons:-

1. 26 litres per 100km towing the BT and 17 without. (the 100 series with DTS turbo would do 19 with BT and 13 without, and

2. Towing down steep hills is harder on brakes in both LC and BT as the petrol simply does not have the compression braking that the diesel has.

Whilst at Copeton I heard that Toyota were testing a 5.7 V8 twin turbo diesel in Oz at present. Don't know how true this is but I rushed back to my dealer and placed my order, even though they knew nothing about it!!!

The other alternatives of course are the yank tanks (F250, Dodge Ram of Chev Silverado) but we (especially Liz with a bad back) found the ride a little harsher, the build quality not as good, and the 17m turning circle is a disadvantage in tight manoeuvring areas such as in in our driveway, at shopping centres, some caravan parks, (such as the one at Mooloolaba), tight creek crossings and bush tracks that come to a dead end or become too narrow for the BT - or, any where you have to make a U-turn.

They do, however, have superior straight line towing ability, can keep up with or even overtake B-doubles, and the whole rig is safer at these higher speeds. If your itinerary is tight on time, this is obviously important. It is also important for people like the Jaunty Jordans who have to travel long distances on a regular basis.

However, for us, the plod from camp to camp should be as short as possible. Even on a long trip such as going from the east coast to the Top End or WA, the maximum day drive will only be about 500km. (9am to 3pm).

Hope this helps.............Rob ** best Landcruiser I've had.

By the way, was it you we were speaking to on your pick up day at BTI 4 Oct.?

Howdy all,
I would like to widen this very informative discussion. One of the reasons among the many for the proponents of diesel is the availability or more to the point the NON availability of petrol in very remote areas. If anyone has had experience of this I would be interested. The reason for non-availability is to reduce substance abuse.

I have heard that BP are not long away from selling a "sniff-free" petrol which may change the situation dramatically. The price differential between the two fuels is huge at the moment which must play a part in solving the bottom line equation. It is probably safe to say if the price difference remains the same for some time you won't be able to give away the truck- type tow vehicles. 145 cents is the minimum price in the bush I have been told. Some years ago a collegue did an exercise with diesel verses petrol with all the variables thrown in and his conclusion was that petrol was by far the best economic choice.

OK fellas over to you
Ernie

Let me throw in my 2 cents without repeating what has been said.....
I have considerable experience with engine building and supercharging V8 petrol engines. There is no doubt that the best bang for your buck can be obtained from any engine by compressing and after-cooling the air induction provided everything else necessary is correctly done as related by Anthony in this thread.
Turbo charged diesel engines are the best torgue generators producing more cost effective torque than a supercharged or turbocharged petrol engine can achieve.
Notice that I have not mentioned h.p. or kw, they are are not half as important as the torque generated by the engine when talking about a tow vehicle.
My LC100 TD with 530 nM torque has a power to weight ratio equal to the F250
and tows my BT effortlessly. There are numerous other difference in the vehicles which renders the F250 are better tow vehicle. My fuel consumption is 11 L/100 km around town and a mximum of 16.5 km/100 km when touring with the BT fully laden. I believe that that compares very favourably with anything else being considered.

Ernie, In the past I have travelled far and wide across much of the outback and have never had problems obtaining unleaded fuel, regardless of price. There are not many distances, apart from a few very remote desert tracks, where you cannot fill up withing 400 - 500 km at the most. In addition to that, the volume of diesel typically consumed is about 50% of the amount required for a petrol engine.

Has anybody thought of using a Isuzu NPS 250 4X4 to tow a Bushtracker.
I'll Give you some details:-
4 cylinders 4751cc, Turbo intercool, 103 kw, 363 Nm, 14 m turning circle, and I use 18 L per 100 km. I have fitted a extra 300 L tank (plus original 125 L) which gives me a safe 2000 km between fill ups.
The down side, 90 kph tow speed (Top speed114 kph) and you would have to rearrange the rear springs as it would be too stiff. Ideally fit air bags.
Far cheaper than F250 4X4. A little harder to get into the cab. Other than that a very good vehicle. Think of what you could carry on the back.

Regards
Brian

certainly a can of worms anthony but useful
no rob it wasn't us at bti in oct our date is may 2005 when we hit the road time will hopefully be on our side ( planning to do the curcuit taking around a year & then picking out the favourites to revisit with a lot of criss crossing to get there) so speed not especially important
from my understanding of diesels you get around twice the range as petrol which dave seems to agree with this coupled with the compression braking & the low down flat curve torque seems to be a real advantage for us as towers
dave from what ive read on this, exploroz & the caravanners sites your consumption is indeed impressive have you done any other mods added a chip ?

i read on exloroz where people where claiming remarkable differences in consumption & top speed depending on tyre type size & pattern especially changing to offroad tyres with high profiles ( be good brands )

regards