Pros & cons of swapping 4 speed to 5 speed?

[stoneageman]

Hi all, i am considering swapping my gearbox for a 5 speed. It's a 1984 1.9 petrol Kamper conversion. The present gearbox is fine, however was thinking about economy really. Is it worth doing this swap or would it be more beneficial to go down the LPG route?

Thanks all, i don't do decisions and would appreicate some advice from those who know

[keith]

its not about the number of gears.

its about the gear ratios....

its about matching the number of ratios against the power of the engine.

there are many different boxes...but a 5 speed may have the same final ratio as one of the 4 speed varieties.

bigger final ratios by definition require more power to use the extra gearing....so beware of that. Increasing either the wheel size or even the tyre wall size will have a similar effect of lowering the RPM for any given engine speed.

lpg will surely give you a massive return on economy...far more than a box swop.....and your van stays as vw intended.

hope that helps...

[stoneageman]

Fantastic, cheers Keith! That's really good advice, particularly as the conversion is completely original, so it makes sense to keep original box too. I have previously looked into LPG, i will resume that now

Cheers Keith

[keith]

there are lots of good guys on here who know lots about LPG conversions....i think the key is to have the installation done by someone who really knows the vw engines...Steve at Gasure in Chester only ever gets good feedback.

its an initial outlay...and then happy days motoring from there on in...according to the boys in the know.


(im a diesel man myself...and have a modified big 5th gear box......but its all horses for courses...pros and cons)

[billy739]

what sort of mpg are you getting ?

also remember the little things , servicing ,tyre pressures ,driving technique , only carry what you need ( weight = fuel) ect ect


next time you fit tyres to the rear try 195's instead of 185's


4 spd 1.9 petrol high top when I had mine I got 27mpg constsantly , cruise speed was 60-65

[richlaz]

If your existing gearbox was buggered, then it may have been a good idea, but personally I don't think it would be worth the expense...

Plus the "upside down" gearboxes are a pain in the a***

[what2do]

@billy, educate me, why do you recommend wider tyres in order to improve mpg? In my mind, they must have a greater rolling resistance due to the increase in footprint - but I'm probably wrong lol.

[markhale10]

next time you fit tyres to the rear try 195's instead of 185's

What difference will the width of the tyres make? Surely it's the radius that would help efficiency? Bit confused with this comment.

[billy739]

radius is based on size .
the tyre size profile ie 82 (185 82 14)

82 is a % of the width so a 195 is taller (bigger radius) so a 195 tyre is taller than a 185
http://www.brick-yard.co.uk/VehicleSpec ... ltwhls.htm

I currently have 215 14 tyres on my van

its only a minor difference , but everything helps , and I get to keep the og wheels


185 82 14 tyre = 654mm diam
195 80 14 = 668mm +14mm
215 80 14 =700 +46mm

overall 14mm bigger

[kevtherev]

I bet some folks thought the sidewall was a measured distance billy.
Tyres and their radii are your fifth gear
But what you gain on the flat you lose on the hill.
Larger radius will indeed drop the rpm, but without power or rather torque its all academic.

My pal had a taller 4th fitted to his DG box but also fitted a DJ 2.1
With the extra power it cruises at 3200rpm @ 70 mp.....haviing LPG as well....

[markhale10]

Thanks for that billy. I learned something new there.
I also thought the 82 in your example was a fixed measurement regardless of tyre width.
It's good to learn, that's what the forum is all about I guess.

[ghost123uk]

And of course when billy says 14mm "bigger" that is diameter. So the extra distance travelled by the tyre is 44mm more than standard (Pi x D) Which I think is a 6.7% increase (someone will correct me if that is wrong).

(If I am right) a 6.7% higher gearing is not insignificant (is it ?)

[billy739]

(If I am right) a 6.7% higher gearing is not insignificant (is it ?)

I know its not very much , but every bit helps. it dosent cost much more if your were buying tyres anyhow

you could go extreme and get some 15 inch wheels , and fit 195 80 or 205 80 , I think you may be able to fit 215 80 but not sure may depend on wheel offset - this would give you an idea as a test bed but expensive if it dosent work.

also changing tyre sizes is not quite like changing gear ratios , its similar but the results aren't quite the same like as you said width ect will have a neg effect , but it will be good enough to get an idea.

[keith]

be careful the extra diameter doesnt sap your power though.

i went from 205 60 16 to 215 65 16.....and the difference in acceleration was noticeable.....(as was cruising rpm of course)....its a tradeoff

[richlaz]

So from 185's to 195's... 14mm extra diameter... (assuming same profile)

But you also have 10mm extra width on the road... so more resistance

I can't personally see it making a difference