OKA 413 _ A New Hope

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05 Aug 2019 08:33 #21 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: OKA 413 _ A New Hope
Hi Holmz, standard Oka fitment all round. It uses the same fixing points as the original.note. LT bull nars have two extra mounting bolts (than XT). Chris also provided new mounting brackets to suit.
Like many things Oka there's variation in the fit so mount fixings were drilled to suit when installed. Chris also supplied cuztom light and aerial mounts to suit..
A very professional job.
Deano :)

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05 Aug 2019 08:39 #22 by nugget
nugget replied the topic: OKA 413 _ A New Hope
Looking great Deano...holding Chris's ally bullbar up the sleeve incase I get too close to 4.5 at the end of #050's build

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09 Aug 2019 19:57 #23 by Joseph Baz
Joseph Baz replied the topic: OKA 413 _ A New Hope
Deano can you please txt me Chris's mobile number ?
Cheers,Joe

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11 Aug 2019 13:32 #24 by Harry
Harry replied the topic: OKA 413 _ A New Hope
Yes deano I totally agree with you as I also got the bull bar in aluminum before you and talked you into one . The bull bar on Oka413 is actually the bull bar that Oka 045 rejected, ha ha ha that is a personal joke between dean and myself The fuel tanks but in steel and the folding steps and a very big YES to his ability and workmanship thanks Chris

Jenny and I both enjoy the great outdoors. We try to get away 4 to 5 month a year.

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11 Aug 2019 18:19 - 11 Aug 2019 18:20 #25 by Holmz
Holmz replied the topic: OKA 413 _ A New Hope
He is a hard bloke not to like... I keep trying... but alas I am failing.
Last Edit: 11 Aug 2019 18:20 by Holmz.

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02 Oct 2019 19:24 - 02 Oct 2019 20:37 #26 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: OKA 413 _ A New Hope
Well, we're back into the real world of cold, wet and miserable Gippsland after our 'annual adventure', this year up to the Kimberley and Gregory NP region and returning via WA north west, Oakover River Region, Gary Junction Road and the outer West McDonald ranges. A wonderful trip with other like minded Oka owners in the Kimberley/Gregory NP area. Thanks to Chris and 'H' for all the hard work in making this a success. :)



Six Okas near Kununurra July 2019

Well as usual after our annual jaunt I go into 'I can make things work better mode' and embark on improving the Oka for the next trip. (sometimes I get the feeling that Kaye would be a lot happier if I just let things be, but I could be wrong :) )

Last year was no different and there were a number of 'improvements' made prior to this years holiday.

1/. Change diff ratios from 4.88 to 4.10 and changing tyres from 38" 325/85R16 Michelin XML's back to 36" 305/70R19.5's
2/. Significant weight reduction and axle load distribution revamp
3/. Major house electrical upgrade with new LiFePO4 battery(s) with new distribution and charging systems

Well, as can be expected some of these 'improvements' were successful :) and some not so much :(

Diff ratio and wheel/tyre change

IMO the Oka factory diff ratio (4.88) is just about a perfect match (in a touring setup) for the factory Perky and manual transmission with 35"/36" tyres such as 900R16, 255/100R16, 285/70R19.5 and 305/70R19.5's. A 'liteweight' or well tuned factory spec. Oka can even run 38"s, 325/85R16 XML's in 5th gear but it can be a push on anything but flat ground.

It's a different story though with the additional power of a Cummins 6BT or other power upgrade engine which can result in unnecessary over revving of the engine, as was the case with #413. This can be addressed a number of ways. 1/. fitting larger diameter wheels/tyres, 2/. changing gearbox/TC (high) final drive ratio or 3/. changing the diffs to a higher (lower numerically) ratio.

I was already running 38" 325/85R16 XML's which IMO are the absolute best off road/mud tyre of all time, bar none. Not so bad on road as you might think if run at 60 psi so that the tyre is running on the centre of its tread and not the outer lugs. As the tyre wears though (approx. 30K Km in my case) the lugs start running on the bitumen and the ride/noise/drag is appalling :( If I lived in Alice Springs or Kununurra for example I'd run these full time but not when I've got thousands of K's of bitumen driving to get to my off road destination.
40" tyres are available and would be a 'good fit' but are as rare as rocking horse excrement in Melbourne/Sydney so totally unobtainable in the sticks so IMO not a good choice in the long run. Truck tyres/rims in 20"/22.5" are way too heavy for easy handling IMO so not an option.
Changing the gearbox is a good option for those so inclined ie. Allison (auto) 2400 has a 0.60 2nd overdrive (vs. Turner/Spicer std. Oka 5th gear of 0.78) from memory so a good option. Dodge RAM manual and auto (47RH) have final drive of 0.72 ish so also a good option with suitable tyres. Good options but a lot of work and expensive.
Diff ratio change is another option and IMO probably the best bang for buck/easiest.



Oka Paul in his element

Relevant Dana diff ratios are 4.88, 4.56, 4.3 and 4.1. On paper 4.3 is the best fit but unfortunately not available in Dana 70 so barring a rear axle 'upgrade' the Goldilocks ratio is a non event so either 4.56 (too low) or 4.10 (too high), assuming 36" wheels are the choice.

I went for 4.10's and Oka Harry who upgraded at the same time went for 4.56. Both of us run 305/70R19.5's and have the same Dodge RAM Cummins 6BT engine and original Spicer/Turner gearbox. GVM's and vehicle usage are very similar.



Oka 45 (Harry & Jenny) and Oka 413 (Dean & Kaye)

For a one step simple solution Harry's choice of 4.56 works straight out of the box. My choice of 4.10 will work with additional engine power/efficiency/wheel upgrades.
My short term 'fix' is to change the wheels to 34's, ie. 315/75R16's. The long term solution will be a bit more complex.

So overall my diff upgrade to 4.10's (compared to 4.56's) was a bit of a fail :(

Deano :)
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Last Edit: 02 Oct 2019 20:37 by Dean and Kaye Howells.
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03 Oct 2019 14:17 #27 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: OKA 413 _ A New Hope
The standard diff ratio with the Allison's 5th gear at .71 and 6th at .61 works well with 315/75R16 tyres, trundles along at 1850 rpm at 100kph but funnily enough is happier at 1950 rpm at 105 kph and makes no difference to economy which can vary between 14 and 18L/100k depending on which way the wind is blowing ;-))

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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08 Oct 2019 07:22 #28 by Greg Boyle
Greg Boyle replied the topic: OKA 413 _ A New Hope
Gday Dean
Any plans for an Intercooler in the next 6 months pre trip maintenance schedule ?
Greg

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09 Oct 2019 11:51 #29 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: OKA 413 _ A New Hope
The short term solution to #413's 'high gearing' (4.10 diff ratio) problem will be to fit 315/75R16 (34") tyres on alloy rims. From an engine load/speed perspective this combination will give me the same overall final drive ratio as my 'Goldilocks' 4.3 diff ratio on 305/70R19.5's :) ie. At my preferred touring speed of 90-95 Kph the engine rpm's will be approx. 1875 -1975 rpm in comparison to the current 1775-1875 rpm with my existing setup. This increase in engine speed of 100 rpm for the same road speed should make a big difference to engine loading/performance/EGT's and overall fuel consumption. That's the plan anyway :)

Another benefit is a big decrease in vehicle weight. The 315/75R16's on alloy rims are approx. 40Kg EACH lighter than the 305/70R19.5's on factory steel rims so a total of 240Kg weight reduction with the added benefit of a smoother ride and a lot easier to manage when changing tyres. There's no such thing as a free lunch though. The 315/75R16's have a load rating of 127 whereas the 305/70R19.5's have a load rating of 147. What this means in practice is that the 315/75R16's can't carry the high load of the 19.5's and are more puncture and side wall damage prone. For 'normal' touring this is probably not an issue but for rough 'off road' driving this is an issue. eg. on our latest Kimberley trip four of the six Oka's involved had 19.5" tyres/rims and two had 16" rims with correspondingly lighter weight tyres. The four vehicles with 19.5" tyres had one flat/stake between them and the two vehicles with the lighter weight 16" tyres had 6 flat/stakes between them.

The long term solution will be to improve engine performance/efficiency with the addition of a water/air inter-cooler (also called an after-cooler) and a more efficient/powerful HX35 or preferably HX35W (waste gated) inter-cooler. When this is done I can re-fit the heavy duty 19.5" wheels.

An easy inter-cooler fit would be the Cummins factory after-cooler as fitted to the 6BT-A engine but I have been unable to find one with the associated replacement injector plumbing at a reasonable cost.



Factory Cummins 6BTA water air inter-cooler (red arrow)


Otherwise something along the lines of Peter James setup would be the go. It would be nice to have this completed before next June/July but only time will tell.

Deano.
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09 Oct 2019 17:15 #30 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: OKA 413 _ A New Hope
Dean the bit I couldn't get my head around with a factory aftercooler like in your picture, was that if it was connected as standard and using the engine coolant to cool the incoming air then as that coolant is at a nominal temperature of 80C why would you want to HEAT the air to that temperature? Especially when that is a minimum that might be possible.
I know that the aftercooler draws the coolant from the returning cooled water in the radiator before it goes into the engine so yes it might be down around 50-60 degrees but it still won't be cooling the air much if at all especially in cold weather, typically block temperatures are in the 75-85 C so everything attached to the engine is that temperature as well.
I have temp sensors going into and out of the intercooler and typically air into the engine from the intercooler is around 40 -45 degrees C with my setup so if the factory aftercooler is to be used then an external cooling system would be better than using the engine coolant.
I have a factory aftercooler in the shed but like you I found the cost of the matching injector lines made it cost prohibitive to use.
After this years 10k outback trip where more than half that was on rough corrugated tracks and sandy desert tracks nothing broke or fell off with my intercooler setup so my backyard engineering was up to spec ;-)))

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.

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09 Oct 2019 18:13 - 09 Oct 2019 18:14 #31 by Outback Jack
Outback Jack replied the topic: OKA 413 _ A New Hope
You can get from UK piping for around 300 or 400 a set for memory. I have several discussions with Cummins Engineer in regards to Aftercooler and replacing it with something like Peters. He went into a lot of maths and science, but at the end of the day, the gains would not be great compared to costs etc. I already have the 6BTA and have a spare set of lines. I going to replace them when I sort pump out.

I think both have good and bad points.
Last Edit: 09 Oct 2019 18:14 by Outback Jack.
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09 Oct 2019 18:55 - 09 Oct 2019 19:15 #32 by Dean and Kaye Howells
Dean and Kaye Howells replied the topic: OKA 413 _ A New Hope
What you're saying is right on the money Peter and with (at best) 65 degrees C coolant from the back of the head feeding into the after cooler and returning to the 'cold' water engine inlet there's not a lot of advantage, but probably better than nothing, or is the coolant flow the other way ?. Another negative would be having the after cooler radiator up high in the engine compartment potentially radiating heat into the cabin.

I'd install mine a bit differently. In #413 I've got a highly efficient (too efficient in my application) 5 row copper radiator which except in the most extreme of conditions, and really not even then cools the coolant down so much that the thermostat cycles and doesn't fully open in normal operation. I get around this by running a blind in front of the radiator between it and the air con 'radiator'. This allows the coolant equilibrium to be at 82 degrees C with the thermostat fully open. The return coolant to the engine is always very, very cool.

I'm looking to kill two birds with one stone here and tap off the return coolant pipe (from the radiator) and circulate this using a small pump through the after cooler returning it to the engine in the normal way. The only thing I haven't decided on is whether to use a heat exchanger similar to an auto transmission cooler in the radiator tank to preserve cooling integrity in case of un-forseen leaks or just use the existing coolant directly which would be a lot easier thus killing two birds with one stone and ditching the blind altogether :)
Deano
Last Edit: 09 Oct 2019 19:15 by Dean and Kaye Howells.

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09 Oct 2019 20:03 #33 by Holmz
Holmz replied the topic: OKA 413 _ A New Hope
Does anyone have intake temps before the intercooler?
Unless I am missing something, I would have expected the boost to produce a lot higher temperatue than 80C.

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10 Oct 2019 04:41 #34 by Peter and Sandra OKA 374
Peter and Sandra OKA 374 replied the topic: OKA 413 _ A New Hope
Holmz I typically see anywhere from 80 - 150 C into the intercooler depending on how much the welly is buried, on a 40 degree day it has gone higher. As I said earlier temps out of the intercooler are around 40 - 55 with the occasional spike to 80 on a really hot day on a long hill at full throttle where I think the intercooler can't shed the heat due to either not enough coolant in the system or water flow too fast or too slow, I've not bothered with more development as it works fine 99% of the time.
The system only has about 5-6 litres even with a three core radiator of about the same size as the Oka's and just the plumbing and intercooler where Ralley has a 1/3rd bigger intercooler, a header tank and a bigger pump so has more coolant in the system and faster circulation which gives him better cooling.
With my setup the minimum of 50 degree drop in intake temps dropped the EGT's by up to 150 degrees which in turn allows a little more fuel and in turn more power ;-))
Before fitting the intercooler I had to drive it on the EGT gauge on hills and at higher altitudes it was easy to raise EGT's too high without even trying, now with the intercooler I never have to worry even at 4,500 to 5,000 feet (highest around here to test) even though I've upped the fuel a wee bit more.

OKA 374 LT Van, converted to camper/motorhome,
400ah Lithiums, 680w solar, diesel cooking heating and HWS,
Cummins 6BT, Allison 6 speed auto, Nissan transfer.
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10 Oct 2019 17:17 #35 by Outback Jack
Outback Jack replied the topic: OKA 413 _ A New Hope
This is a good place for intercooler parts and kits


Frozenboost
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11 Oct 2019 18:59 #36 by Ralley
Ralley replied the topic: OKA 413 _ A New Hope
Frozen boost is the place I deal with.
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