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110Matty

Member Since: 20 Apr 2023
Location: Somerset
Posts: 129

The Ashcroft calculator is interesting and shows slightly conflicting info - but that's probably for two reasons:

1. I'm a numpty and have probably input something incorrectly
2. I don't know if the road speed in the calculator is actual road speed (by GPS or recalibrated speedo) or if that's what the speedo would read, incorrectly due to the increase in tyre diameter?

Anyway, it's probably pretty accurate, based on the photo's below.

The first one shows what a stock defender TD5 90 should be (pretty bang on with mine, albeit my tyres are 31.6" diameter).

The second one is the more detailed calculation and you can see my recorded RPM next to the 5th gear figures for 50/60/70 and 80mph Ashcroft suggested speeds. I take from that, that it seems to make sense that my speedo is under-reading by several % and so my 80mph revs of 3000 is more likely 85mph or even a little more.

I think in all honesty, it's a very good and worthwhile guide, but with a 20+ year old vehicle with many previous owners, I personally can't be sure 100% that other things (e.g. diff) haven't been changed from standard, thus skewing the results. Inaccurate speedo, rev counter slightly out etc etc. I tried to follow the wife on cruise control to ascertain my road speed accuracy and although my speedo definitely under reads (i think due to tyres / wheel combo) I can't be 100% accurate, so like i said, it's a good guide, but not a NASA experiment.

Also just noticed on the Ashcroft site - The ideal target RPM is 2,700 revs at 70 mph in top gear. If you use the ratio calculator to get as near to this as possible. If you look at the table below, I'm bang on that (by speedo).

I'm also aware that there is no mention of Remaps (I have) or heavy towing (I will not), but it's near perfect for me.

There are folk far cleverer than me that might understand all this better !!

Click image to enlarge

2nd May 2024 10:00am

rustandoil

Member Since: 08 Sep 2012
Location: Cotswolds
Posts: 735

2005 Defender 110 Td5 XS DCPU Bonatti Grey

This has arrived 😎

Click image to enlarge

4th May 2024 7:25pm

34064

Member Since: 12 Dec 2023
Location: South Central
Posts: 162

I am very interested in how people find the 1.3s as I am considering making the swap when funds are available 110 Td5 Ex Utilities slowly converting into a pop top camper one day

Build thread:https://www.defender2.net/forum/post1024784.html#1024784

4th May 2024 9:33pm

110Matty

Member Since: 20 Apr 2023
Location: Somerset
Posts: 129

rustandoil wrote:
This has arrived 😎

Click image to enlarge

All the best with it 👍

4th May 2024 9:37pm

Procta

Member Since: 03 Dec 2016
Location: Sunderland
Posts: 5136

110Matty wrote:
MarkBrown wrote:
I’ve a 1.2 in my 110 and want a 1.4 as it’s too high ( for my use ) From my experience they are much the same, it’s just some of the fittings are different. Mine originated in a disco 2, but apart from the drive flange being larger and the high low fitting slightly different, my other 1.4 box looks the same. Although thinking about it the disco box has no speedo drive hole, I remember swapping the tail piece for one with the drive. Winchester gears will most probably do it for you.

Cheers Mark, my use is mainly A and B roads, no significant towing and will be combined with a mild remap. From what i've heard and read, the 1.2 would be fine for me. Thanks for reply.

my TD5 has this sort of setup, as the Ashcroft transfer box, which i think does have the disco ratios, and a mild remap, which was what pushed me for this defender, not the remap but Ashcroft itself. The owner said it was to quiet down and the remap was to make it keep up with current traffic. Mine has not towed yet, but the previous owner has, but that's been a very small trailer. I am in two mines in looking at bumping it up to a stage 2. Just to spice it up a little more.

Defender TD5 90 ---/--- Peugeot 306 HDI hatch back

Success is 90% Inspiration and 4 minutes Preparation # you can make it!

5th May 2024 1:42am

MadTom

Member Since: 10 Sep 2013
Location: Olomouc
Posts: 615

Calculator has no idea of speedo correction and use just the tire diameter you wrote in for calculations. Small differences like 1MPH or 10RPM is nothing, just real reading from car and some numbers rounding in calculator. Just try different transfer box ratio and you will see completelly different results, not only some minor changes.
Gearbox and diff ratios are simple to choose, a bit bigger problem is how to measure exact tire diameter. Numbers written on tires are really not very accurate. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo

5th May 2024 5:45am

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 7986

2011 Defender 110 Puma 2.4 USW Stornoway Grey

I had a 1.3 in my 130 tdci on 31s, 3.54s, worked much better than std 1.2 (puma). Am keeping it for m57 conversion as it sits nicely in boost range at most usable speeds and then130nis heavy and towing alot.

For comparison have 1.003 in my 90, m57, 4.11s and 33s. Cheers

James
110 2012 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

5th May 2024 8:59am

MarkBrown

Member Since: 03 Oct 2022
Location: Mid Wales
Posts: 442

1983 Defender 110 Other HT Auto Keswick Green

The calculator doesn’t also take into account the amount of power the engine produces and at what rpm. My 110 200 tdi with 32 inch tyres was hopeless with the 1.2, 1st gear was just too high. Changing it back to 1.4 was much better, as it should be. However my OM606 110 automatic with 33 inch tyres has no such problems, but it’s nearly three times as powerful, plus the way the automatic works allows the revs to rise from standstill. The only problem I have with that is that it won’t go into lockup ( overdrive/ sort of 5th gear ) until 56mph, which is a little bit late for most A and B roads, perfect on the motorway though.

5th May 2024 9:08am

rustandoil

Member Since: 08 Sep 2012
Location: Cotswolds
Posts: 735

Well, it's in..... Did it with the help of my son in the end.... Tomorrow should get a long way towards finishing up.
👍🏻

Click image to enlarge

9th May 2024 8:02pm

jst

Member Since: 14 Jan 2008
Location: Taunton
Posts: 7986

Nice Cheers

James
110 2012 XS Utility
130 2011 M57 bespoke Camper
90 2010 Hardtop
90 M57 1988 Hardtop

9th May 2024 9:17pm

rustandoil

Member Since: 08 Sep 2012
Location: Cotswolds
Posts: 735

Finished up the installation yesterday... A test drive shows my 110 still pulls away as I like, not a massive difference overall but probably worth doing if you are having a rebuild.
I've got 50mph @ 2000rpm and 30mph @ just about 1200rpm in 5th gear.
This only matches the Ashcroft ratio calculator if I reduce the tyre size down a bit.... Not sure I'm worried about such detail, glad to have the 110 back on the road.

11th May 2024 7:25pm

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