Stirlsilver's Disco Ute Project

**stirlsilver** · 24th December 2012, 10:16 PM

Originally Posted by Skiboy

So a suggestion might be to use sheet metal just like the rear with a fold (maybe rounded) and the corner. Then cut and rubber the side windows in as per the rear. Like on defenders etc.

That is a thought, but the area where the whole thing would become unstuck is the curved surface. It would be tricky to form up a folded section that is curved for me. I think I'll carry on how I am currently going. An alternative could be to stitch weld in some thin sheet metal across all gaps and then bog it so it all blends. At this stage, i'm still leaning towards fibreglass

Originally Posted by Skiboy

Auto
Did you unbolt the auto from flexi plate via the hole in bottom or the front plate? You may know all this but I made up a socket on a bent steel bar so can use socket from front to undo flexi plate bolts. Done 3 auto conversions with this now. Works a treat.

And a tip for holding torque converter in place while installing (so not slip out and then stuff oil pump lugs when bolting in (experience

) - bolt an alloy bracket bent to hold torque converter in place - see below

I'm not very familiar with automatic transmissions to be honest. I've always had manual cars, this is the first auto. To illustrate the point, when I pulled the engine out, I was told to make sure to unbolt the torque converter before pulling the motor out. So I proceeded to to remove all the bolts along the circumference of the flex plate. Later when I had the engine half out, to my horror I saw the torque converter coming with it! Turns out I unbolted the ring gear!

I did have a read through your build thread (nice work by the way), and I did notice the tips you mentioned. Would have been nice to know about the purpose of the hole before I pulled the engine out! Anyway, such is life.

Back to the build:
Over the last couple of days, I've been spending time trying to figure out what size turbo I should start looking for. First I went about trying to figure out what volumetric efficiency I should be using.

Obviously it is known that 2 valve engines typically have a volumetric efficiency of around 80%. But I knew that volumetric efficiency changes with RPM. After doing quite a bit of searching around the internet I found a couple of references that indicated that an engine's torque curve closely follows the volumetric efficiency (Not2Fast: Turbo Glossary). So I went off to find some dyno curves of rover v8s. Below is what I found:

Rolling Thunder - TVRs on the Dyno

Tuning the Rover V8

In the above two instances used maximum torque to be 4,000rpm and I made this the 81% point. And then scaled it from there according to the curve.

The problem I had with the above was that the volumetric efficiency went down with reducing RPM and this didn't make any sense to me. So I looked around some more and I found that torque reduces with RPM because of the geometry of the engine being tuned in certain ways, more heat being soaked into the block and the rate of combustion of the gas. That all made sense to me (info from Why Does the Torque Curve Drop Off at Low RPM in a Typical Piston Engine?)

So I looked around some more and then found this:
ScienceDirect.com - Fuel - Alternative fuel and gasoline in an SI engine: A comparative study of performance and emissions characteristics

The diagram above confirmed my suspicion that volumetric efficiency remained approximately constant at lower RPMs. So I then used the following as my Volumetric Efficiency Table:
1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000
81.00 81.00 81.00 81.00 81.00 81.00 79.16 77.32 73.64 68.00

I could be a little ambitious by using 81%, but anyway.

I used the excel sheet on this website (which is an excellent reference by the way):
Chevy Twin Turbo Project - Reading Compressor Maps and Selecting a turbo

And with some adjustment I got the following:

The values were cross checked with this calculator, and seemed to be agreeing with each other:
Not2Fast: Turbo Calculator

I then spent some time checking through what possible garett turbos could be used and below are the results:

At first it looks like the GT1548 is the best candidate as the curve starts nice and early and the points are close to the peak efficiency. However, when you look at the efficiencies you find that it is a very low efficiency compressor 68-72%.

So perhaps the GT2052 52 Trim is the better option as its efficiencies are in the region of 74-77%.

It would be great if anyone can confirm i'm doing this the right way. Because I've never done any of this before so I could be doing something wrong somewhere.

**Skiboy** · 26th December 2012, 09:16 PM

Thanks for comment re build - as you know a long run on these projects and hard to keep going with other time demands popping up. It is worth it when have something unique on the road.

Autos we learned by doing a swap on an manual ute after the gear box failed 1 week into ownership. Auto give great control up hill on rocks etc. Takes some more skill on down hill as not just stick in 1st and let it run. We put hand brake part on to get the torque converter to lock up - ours is all stock standard.

Note the issue on my build re installing the torque converter - also see the link to the technical post on testing if got it right.

We added an after market oil cooler (alloy matrix) to front of car as standard unit was not keeping the temp down enough in hot summer hard hilly 4x4ing. We put a temp sender in the line to monitor and just as well as would not have known we had a problem with the standard cooler not being enough.

Turbo on 3.9 with gas? I thought I read somewhere you had to build the engine differently if wanted to get max reliability from engine on gas - higher compression? Top hat liners to stop slipped cylinder liner - a common 3.9 problem.

Have you looked into that at all? Plan a rebuild on the 3.9? That is where I would put the $ not the auto - autos can replace fairly cheap.

SKiboy

**MacMan** · 27th December 2012, 08:37 AM

Looking from the outside in, I'd also treat the engine as the main priority. Second hand Discos can be bought so cheaply these days that I reckon you'd have an endless supply of transmissions if you really thought you were going to stuff them but a good engine is for keeps.

**stirlsilver** · 28th December 2012, 07:29 PM

Originally Posted by Skiboy

We put hand brake part on to get the torque converter to lock up - ours is all stock standard.

Thanks for the tip! Which automatic transmission do you have and on what engine are you using it on? Also are you using the standard sized torque converter? And is this on the rangie or the stage 1 hybrid? Also how much have you used it?

Based on your info, I may stop considering doing the 4HP24 upgrade.

Originally Posted by Skiboy

Turbo on 3.9 with gas? I thought I read somewhere you had to build the engine differently if wanted to get max reliability from engine on gas - higher compression? Top hat liners to stop slipped cylinder liner - a common 3.9 problem.

Have you looked into that at all? Plan a rebuild on the 3.9? That is where I would put the $ not the auto - autos can replace fairly cheap.

You are right, LPG can allow you to have a higher compression ratio. I actually started a thread here regarding the turbo sizing and implementation:
The V8 Owners Forum - :: View topic - Rover v8 3.9 Twin Turbo Build - Turbo Selection

Just to figure out the size that I need, and right now I'm trying to work out if I can get away with the boost I need and keep the engine at a compression ratio of 10.5:1.

With the engine rebuild, yes of course I'll do that along with getting everything balanced and matched. The liner slipping issue is something I hadn't thought about though. I haven't looked into it, but top hat liners sound expensive!

The reason I am making a fuss out of the Auto is they are a pain to put in and pull out (admittedly if you disconnect the torque converter, they are easier than a manual). So I figure I might as well get it all worked on while out and not worry about it later then.

Originally Posted by MacMan

Looking from the outside in, I'd also treat the engine as the main priority. Second hand Discos can be bought so cheaply these days that I reckon you'd have an endless supply of transmissions if you really thought you were going to stuff them but a good engine is for keeps.

This is a fair point, the engine will be a priority, but the gearbox upgrade is something I came across on the ashcroft website. But if that is overkill, I won't go that way. I've already been told that the basic overhaul price of a 4HP22 is $3,000!

**stirlsilver** · 2nd January 2013, 10:11 PM

Below is the concept for the tray skinning I have come up with. I'll get the compartments with the 3 hatches made by a local toolbox shop I think.

**stirlsilver** · 2nd March 2013, 08:56 PM

I'm back everyone. After a 2 month break. What did I do? Well I had a short trip to the USA, and then after that I went on a 3 week holiday to India for a friends wedding and some sight seeing. If you are curious what india looks like, have a look here http:stirlsilver.smugmug.com.

Anyway, I got back last weekend and today I got back in to the workshop. I did a bit of a clean up and then got into making the small angled panel that will join the rear wall panel to the floor of the cabin. Cutting and folding sheet steel is not so easy without the right machinery. But I got there. Finally TIGed in place and the seams sealed with flexible brush-on sealant

**VladTepes** · 2nd March 2013, 10:57 PM

Love this build....

**Skiboy** · 3rd March 2013, 03:49 PM

Pressure is on - your audience out here has be starved of good build content to read - so glad you are back and back on the job!
Skiboy

**stirlsilver** · 10th March 2013, 09:27 PM

Originally Posted by VladTepes

Love this build....

Originally Posted by Skiboy

Pressure is on - your audience out here has be starved of good build content to read - so glad you are back and back on the job!
Skiboy

Thanks for the comments guys! It means a lot.

I was in the workshop again over the last couple of days, (and I will possibly go again tomorrow)

I bought a tow ball receiver and tongue from BTA towing (they are next door to where I work). This will be welded in soon.

Cutting and starting to fold up the sheet that will make up the edges of the rear wall.

Very happy with how everything is lining up. It's a bit of a challenge doing folding only using a mallet, some thick steel plate and a vice! It's a bit hard to see but the sheet is folded in two different directions to get the alignment to work with the existing floor.

Left:

Right:

The panel welded and seam sealed.

And trial fitment:

**stirlsilver** · 11th March 2013, 09:58 PM

Right, public holiday work. I managed to get in about 9 hours today which is excellent.

I added a couple of extra studs to hold the rear panel more securely for the soon to be started work on the rear quarters. For anyone that is curious, this is how I did the studs.

With the rear wall properly mounted I cut down the rear quarter so they would fit and then started marking where the future cuts will need to be to make the corners out of fibreglass. Happy with the way it is all starting to come together!

I wanted some more time to think it over before doing the final cuts to the rear wall and the rear quarters, so I set to welding in the trailer hitch receiver. I certainly am not going to win any awards with this welding. But it will hold. I'll run an FEA model later to see if there is anything I need to worry about in terms of failing under load.

And a quick trial with the winch roller fairlead, everything seems to be fitting correctly. My bet is I will be hung up every now and again on this towbar receiver, but i'm willing to sacrifice that for the ability to tow something.

And this marks the end of the long weekend progress!

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