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1987 110 2.5 NA Transfer Box Ratio


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1 hour ago, Eightpot said:

Had to drop of a customers car & make the last flight home before xmas - never want to be that tired again..

I did a full day trackside at a World Superbike round in Portimao on the Algarve and then drove home in one hit to Croydon. I was young and stupid, but I was also in a BMW M5. The idea of doing it in the Landy... no. I'd have thought twice about it when The Queen was still paying me for carp like that!

Edited by Junglie
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10 hours ago, Eightpot said:

You really won't notice a huge difference with the 1.4, it will just drop engine rpm, there's enough torque in a good engine to disguise the gearing difference but you won't necessarily go any faster as there isn't the hp to overcome the wind resistance. 

Thanks for your insights - that's really useful and just what I was looking for!

So my conclusion is that with what I believe to be a very good engine (3,500 miles, 1,100 running hours, looking good inside), and a low ratio gearbox, my best option is going to be the Ashcroft 1.3 ratio LT230 gear set.

If I compare what I would get in terms of the MPH and RPM that the Ashcroft ratio calculator spits out, then for my vehicle I get the following engine RPM:

Ratio                                 1.41                1.31

10MPH in 1st              2,158           1,991    <- a standard 90 2.5NA diesel would be 1,941

60MPH in 5th            2,700           2,491

 

Yeah, I'd only get 60MPH downhill with a following wind and I'll need to change down slightly earlier on hills, but the aim of the 1.31 ratio set would be to be a little kinder to the engine in RPM terms, and reduce the decibels. Hill start capability much the same as a stock 90 (with two 9 stone people in the back). And as Sigi says above we also have the low ratios for more challenging hill starts. Also, If I decide to go for a more powerful engine at some point, the transmission can (probably?) remain unchanged.

Think that's the way I'm going...

...until further notice.

Don't think I'd be contemplating this if it weren't for Mike's videos!

https://www.youtube.com/channel/UCRssffMP_F8_SCJcqFLq4Ow

 

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17 hours ago, Junglie said:

Some good experience there...

Florence in 24 hrs though? That's hardcore.

When I worked in Vienna my regular time from work in Vienna to home (Conway, UK) was under twenty-four hours, including the channel crossing, in my 300 Tdi 110 CSW.  Even long distances can be relatively stress-free, especially when you have an overdrive unit.

Mike

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Yeah I'd be happy with 1 3:1 box, especially if you want to go to Morocco etc - it's a tough climb over the Alps, Pyreneese, Atlas mountains etc and as the air gets thinner the power drops off even more and the low gearing will help a little. 

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Sorry, not sure where my heads at today, getting my numbers fuddled - I would not recommend a 1.3 box unless you're using 205 tyres

With 235's or 7.50 tyres I wouldn't go any higher than a 1.4 ratio

I was thinking of a 1.5:1 if you know whatvI mean..

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Ok!

Incidentally,. should anybody wish to know, there's a handy calculator here that will take you between torque and HP:

https://spicerparts.com/calculators/horsepower-torque-calculator

Seems to give the right answers on my checks. Then at least you can get two points on a graph. My gutsy 18J will then put out a magnificent 39.1BHP at 1,800 RPM

Oh dear...

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On 4/29/2021 at 1:31 AM, Eightpot said:

Yeah I'd be happy with 1 3:1 box, especially if you want to go to Morocco etc - it's a tough climb over the Alps, Pyreneese, Atlas mountains etc and as the air gets thinner the power drops off even more and the low gearing will help a little. 

Sorry, I think that this is wrong, but I'm prepared to be corrected  Your wastegate is controlled by a spring, which is not affected by altitude, so the air to the engine will be at the the samepressure, regardless of elevation/altitude.  My experience crossing the sierras in California (8000+ft) bears this out.  Please don't confuse an N/A carburetted engine with a turbo- breathed engine.

Mike

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The problem with a forced induction engine at altitude is that while you may be able to get to the same boost pressure, you are having to compress the air more which heats the charge more than if it were at sea level, add to that the less efficient intercooling (if you have one) and intake temps can rocket, killing power. 

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Posted (edited)
6 hours ago, Troll Hunter said:

Sorry, I think that this is wrong, but I'm prepared to be corrected  Your wastegate is controlled by a spring, which is not affected by altitude, so the air to the engine will be at the the samepressure, regardless of elevation/altitude.  My experience crossing the sierras in California (8000+ft) bears this out.  Please don't confuse an N/A carburetted engine with a turbo- breathed engine.

Mike

Valid point...except that the OP has an NA diesel (as per the thrread title) 

You are, however, bang on with wastegates etc - in fact in theory you may even get better perfomance higher up because turbos love cold air. 

...or not, reading the next post. It's been a long week. Though supercharged or turbocharged aero engines seemed to do pretty well with much higher boost pressures at altitude - no noticeable power loss at all, in fact far from it I think.

Edited by Junglie
Correcting/second guessing myself
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2 hours ago, Junglie said:

Though supercharged or turbocharged aero engines seemed to do pretty well with much higher boost pressures at altitude - no noticeable power loss at all, in fact far from it I think.

Yes, but they *require* forced induction to maintain any sort of power level, plus, they tend to be a lot higher up than most people can drive, and quite a bit of air flow for cooling any intercooler ;)

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18 hours ago, Troll Hunter said:

Sorry, I think that this is wrong, but I'm prepared to be corrected  Your wastegate is controlled by a spring, which is not affected by altitude, so the air to the engine will be at the the samepressure, regardless of elevation/altitude.  

Yeah, we're talking n/a here rather than turbo - but from experience the tdi's aren't immune to altitude problems either - I keep a 200tdi in Johannesburg which is around 1700m above sea level and performance is definitely lagging with much more black smoke till it drops down to lower altitude, but not in the same way as a n/a chugging over a mountain..

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Posted (edited)

Keep in mind, that a turbo with higher pressure will try to reach that pressure! It will reach the pressure up to some altitude for the price of spinning a lot faster, which you can't feel. If the turbo spins to fast, it will be killed. So don't use max boost in high altitudes to often.

But no problem to a NA

Edited by Sigi_H
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Hey - I do appreciate you flagging that up - hadn't realised there was a for sale section on the forum!

However, having totted up costs of getting it from Derby to Penzance, plus an overhaul kit etc, I'm going to stick to plan A and modify the unit I've got. It's only done 3,500 miles, and apart from that I've already started dismantling it.

Thanks though

Phill

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