Timbo's GU 4.2TD

Haha thanks Rossco.. yeah will have to go out wheelin' soon. Just hanging out to get it VIC registered which is this Wednesday!

Well, been driving the truck around a fair bit. Loving it. Few things I'm going to sort out but just need the time! Haven't posted up any pics yet because I'm waiting to get it registered and also waiting to get a part for the gearbox which is annoying. When that happens, there will be pics! Many pics...

Dropped the truck off at Diesel Tec this morning (thanks to AB for pickups and drop offs) for a Dyno tune. I wanted to know exactly how late the boost is coming in and what torque it's making because it's very sluggish to drive. My 2.8TD Patrol is far more punchier around town at the moment. Not good enough! LOL!

Got a call from Diesel Tec about 2 hours later. He'd already had it on the Dyno and had some results for me.

It's making MAXIMUM boost at 3500rpm!!! WAY too late in the rev range. It's also only making 200nm torque at 2500rpm which is too little, too late.

Things that aren't helping;
Chunky Tyres (33" bighorns)
Diff Ratios (I can't think off hand what the factory ratios are.. but I guess that's 4.2 owners love the 2.8TD ratios so much. I was recommended 4.3's).
Turbo too large (It is a sizable Unit)

Also, the dyno shows that there is a bit of improvement to be made in the fuel settings down low. I told Andrew (Diesel Tec) to go ahead and work his magic. He said I may only get a 10% gain down low but he wasn't going to touch any settings for up high. I told him to go ahead anyway, despite minimal gains because I trust his tuning abilities above anyone else.

I got a price on a new Turbo, drive in & drive out price is $5500. Andrew is going to overlay a Dyno sheet of another 4.2TD over mine with the new turbo on it to show me the difference. When I get it, I'll post it up. The results sound pretty damn significant. Can't remember figures, but it's something like an extra 150nm torque lower in the rev range. Trying to get my head around the costs but I'm going to ask what exactly it entails. Would be good if I can sell the Denco on EBAY and get some money back. But anyway, the difference in power & response sounds pretty damn drastic and also a nice smooth power curve. Might be worth it. ;)

As I'm writing this, he just called me. Good news, he managed to get between 20-25% more power from the fuel settings down low. Hopefully this will make it a lot easier to drive around town. While I could get a new Turbo put on, I don't really want to spend that money right now. So we'll see how it goes.

Have the dyno sheets.. will scan tomorrow and post up.

20-25% is a huge improvement mate, I'd be stocked with that.....

Wish my dyno man could of got those figures, i may of still owned it then.

From the dyno sheets, it looks like $5500 will get about +40 rear wheel kilowatts and a bucketload of torque. It's almost too good to say no.

pic 1. Graph shows torque increases between 3 variables on the same vehicle.
RED line indicates standard turbo performance i think.. I can't quit remember.
BLUE line indicates new Garret BB Turbo with 285 tyres fitted.
YELLOW line indicates new Garret BB Turbo fitted with 265 tyres fitted.

I think this is really good info to drum into our heads. We go out into the bush and find something we can't do with our current tyre size. So we go out and buy bigger tyres but then complain the 4WD is slower, consumes more fuel etc. Well now we can see exactly how much power is actually lost through larger tyres!

pic 2. Same variables as above, but shows rear wheel Kilowatts increases rather than torque.

pic 3. This is my 4.2's torque reading. The blue line shows you before the dyno and the red line shows you after the tuning and fuel setting changes.

You can immediately see the difference made. Between 35 & 70KPH there's a real laziness in response. It then starts to ramp up and hit another trough before really ramping up in torque almost vertically. You can imagine how hard it was to drive when changing from 2nd gear into 3rd as that change is right between 65 & 70KPH, right in the flat spot where hardly any torque is being produced.

The red line shows a decent improvement, even though it's only around 20-25%. The torque curve is a lot smoother and gets to peak torque quicker, though not by much. This is due to diff ratios and the turbo itself I assume. A keen eye will also see that I've lost a little bit of peak torque. The number read 4nm of torque less. Considering the improvements made lower in the rev range, I'm not concerned. :D Needless to say, it's improved driving a lot. Although, a new Garret BB turbo looks very appealing. Just look above at those graphs!

pic 4. Not much of a difference here but then again, I didn't want an improvement in kilowatts at this stage. Torque is what gets you off the line and get's your 4WD moving after a gear change. A 2 rear wheel kilowatt difference in power is the total gain going by the figures. There is still a nice little improvement though as it's a lot smoother and the notable dip in the blue line is gone.

While the Patrol is a lot better to drive than it was, I am still seriously thinking about buying one of these Garret Turbos. It's a fair bit of cash upfront but the lasting results would be worth it. When you look at the first 2 graphs, the sheer amount of gain in both HP & Torque for towing and 4WD'ing is phenomenal and it doesn't have to stop there. Even more gains can be had if you then fit an intercooler which will allow you to dial in more boost. Without intercooling you're probably looking at 12-13psi, with intercooling.. well who knows. 18psi? 20psi? Would be awesome and expensive, lol.

You raise a good point about tyres and sizes Timbo . Is going to 265 's to see how it performs before you lash out on another turbo an option or are you happy with the 285 's that are on it and you want to stick with them ?

I'll definitely be sticking to 285's purely because it's a tourer / off roader. You really need a minimum of 33" or 285 sized tyres these days.

If I was just towing a camper on the black top, I'd be thinking of 265's!

With regard to tyre sizing your vehicle may not actually use more fuel with larger tyres. A mate and I compared 33's to 35's on a trip to gympie exactly same running gear same ratios the lot when we got to gympie me being on 33's the trip meter said i had travelled 20km further than he had so fuel consumption may not be a lot different just that your tyres arent doing as many revolutions so your trip meter is say less out of a tank. The power will be noticed as the larger diameter tyre has more leverage on the running gear hence needing more power to get them actually turning in turn robbing you of at the wheels hp

^^ Sounds like a good explanation to me! Cheers bud!