Thread: Progress on My Unimog

Nice bit of fabrication. You have become a gun welder with this project.

Can I ask a slightly off topic question, seeing that you have both a Land Rover and a Unimog, about what you think of the acceleration of the Unimog compared to a Land Rover. I test drove one on the weekend (a U2150) and I was quite taken aback at how slow it was. In general, the condition of the one I drove was poor, so perhaps the turbo was not working properly or something, but am interested to hear your thoughts on this.

Thanks
David

Edit: this is the other thread on my driving experience: http://www.aulro.com/afvb/parking-lo...erwhelmed.html
and this is a thread on the condition of the Mog: What part of 'Exellent Condition' includes panel rust you'd put your finger through?

Other progress involves sizing up a new turbo to make more boost a lower rpm, whilst giving a modest power increase.

The old turbo did not have a wastegate, and only came on boost around 2000rpm. The new one is a GT2860 - a "disco potato" - I've learnt a lot about turbo sizing over the past two weeks:

This is what I got from the suppliers:

Selecting turbocharger:
BSFC= .38
AFR= 22:1
Wa= airflow actual (lbs/min)
Hp= horsepower target (200)

Wa=200x22x(.38/60)
Wa= 27.86lbs/min (Bottom side of graph)

Pressure ratio:

MAPreq = [Wa x R x(460+Tm)]/Ve x (N/2) x Vd

WA= lbs/min
R= gas constant (639.6
Tm= intake manifold temp (130deg)
Ve= volumetric efficiency (.98%) I re-worked the calcs with 0.85 and it hardly makes a difference
N= engine speed (2600)
Vd= engine displacement (Ci= ltresx61=347.7)

=[27.86 x 639.6 x (460+130)]/ .98 x (2600/2) x 347.7
= 10513361/442969.8
=23.73psia (this is absolute pressure including ambient)pressure needed at intake manifold

= 23.73 + 2psi (intercooler drop) (Drop through the Charge cooler will be a lot less - around 0.5psi)
= 25.73
= 25.73/13.7=1.87:1 pressure ratio(13.7 is intake air pressure minus 1psi for air filter restriction) vertical side of graph

This works out to about 12 psi boost to get 200hp so if you reduce boost back a little you will still get 180hp easily and be above your 160hp and far more efficiently.


I checked all their calcs myself from the articles found at this site: Garrett Diesel Tech everything lines up nicely and is well within the recommended area for the turbo.


The Garrett site has a few interesting articles about how to set-up your turbo - this one in particular says a whole lot about compressor sizing TurboByGarrett.com - Turbo Tech103

Then there is some informative articles about turbo installation TurboByGarrett.com - Turbo System Optimization

The photos show the old turbo and the new physically smaller one, which due to modern design flow more than the old one.

If only I knew what I do now about turbo - I would not have gone with the MTQ kit.

Originally Posted by Iain_B

I'm also putting quik-connects at each corner for the air lines to pump up the tyres, air tools etc.

Please don't these are very good at developing leaks and costing you air pressure.

IF you really have to look at the ones with a screw down dust cap and fit an isolator valve between your brake system and your QD's.

If it was a U2150, then it is a large truck but does have a 210hp engine. It should not be that slow. You need to remember that it is a truck - so to compare it to a Land Rover is not really a fairly comparison unless the Land Rover is a Series 1 or 2.

Unimogs are slow - mine will have a top speed of 110kph hopefully, and will probably take around 30+ seconds to get there if it makes it at all. I've made a lot of modifications to mine to make it more reliable, and hopefully more fun to drive - by that I mean not having to drop down to 40kph going up a hill on the highway, but I'll guess I'll find out when I get it on the road.

Originally Posted by spudboy

Nice bit of fabrication. You have become a gun welder with this project.

Can I ask a slightly off topic question, seeing that you have both a Land Rover and a Unimog, about what you think of the acceleration of the Unimog compared to a Land Rover. I test drove one on the weekend (a U2150) and I was quite taken aback at how slow it was. In general, the condition of the one I drove was poor, so perhaps the turbo was not working properly or something, but am interested to hear your thoughts on this.

Thanks
David

Edit: this is the other thread on my driving experience: http://www.aulro.com/afvb/parking-lo...erwhelmed.html
and this is a thread on the condition of the Mog: What part of 'Exellent Condition' includes panel rust you'd put your finger through?

OK - thanks for that info. It would not surprise me if something was wrong with the one I drove. Guess I was expecting more from215HP.

Ben (From Canberra) is importing a little U1250 from the USA which should be arriving around Xmas, so I am going to run over there and take a look at it. It's a DoKA and I've attached a few photos (used to be owned by TRUKTOR in Montana, from the MB forum).

Exactly the plan Dave - manual valve to shut off the air system. I'm also working on a system that will allow me to dial in an air pressure, connect the tyres up have it automatically adjust to the air pressure

Originally Posted by Blknight.aus

Please don't these are very good at developing leaks and costing you air pressure.

IF you really have to look at the ones with a screw down dust cap and fit an isolator valve between your brake system and your QD's.

thats the easy bit...

from your supply tank -shut off valve- pressure regulator as per any normal compressor- your QD's-airline...

unless you want to goto CTIF then you need to look at the axles under the current mog wrecker.

This weekend's work was re-fitting the air lines and it took a few goes to get the airlines from the engine compartment back to the air tanks. First time I forgot the route around the radiator and inner fender - luckily I had the photos from the strip down and when Dan brought his Unicat U1300/37 I took some more of how his airlines were routed.

This weekend I also painted the air tanks, and the various bits of metal that hold the rubber surrounds on the inner fenders, and various other bits an pieces. I'm mounting the air tanks on rubber mounts, to help isolate them from the frame flex.

My set of XM47's have also arrived - I'll use them for driving on the beach and some of the shorter trips, keeping the MPT's for longer distances. Since I have no space left on the ground floor - I had to roll them up the stairs - the whole 1/2 ton of them.