matto_89
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| posted on 28/12/13 at 09:31 AM |
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Type 9 ratios and diffs
I'm running a 1700 x-flow in my seven. It's a nice fast road spec and runs out of puff around 6k. I've got a 3.54 diff and a type 9.
Currently I can just about hit 90 in third and the gap between third and fourth is too big. I'm certain that v-max would be reached in fourth.
Fifth obviously has no poke, but the car does get used for long runs (Le Mans ) and general commuting so it does help the generally useless mpg.
I realise i'll never solve this completely within a reasonable budget as the box and diffs just aren't designed for this use. As far as I
can tell, I've got a couple of options:
1) Change the ratios. Looking on the BGH site though, I don't particularly want a longer first, I want tighter spaced ratios (particularly third
and fourth). Is this an option, has anyone else gone for it, and how much was it?
2) Get a shorter diff. 3.54 is the tallest. I'd still have a gap between the ratios, but I'd be able to pull through it better. Long-term,
I'd like an LSD so could use the purchase of one as a chance to change the diff ratio. Even 3.77 should make quite a difference.
Neither option will be perfect. Anyone else done anything different to get round this problem?
Cheers all - Merry Xmas and a Happy New Year.
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baz-R
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| posted on 28/12/13 at 10:06 AM |
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quote:
Originally posted by matto_89
1) Change the ratios. Looking on the BGH site though, I don't particularly want a longer first, I want tighter spaced ratios (particularly third
and fourth). Is this an option, has anyone else gone for it, and how much was it?
2) Get a shorter diff. 3.54 is the tallest. I'd still have a gap between the ratios, but I'd be able to pull through it better. Long-term,
I'd like an LSD so could use the purchase of one as a chance to change the diff ratio. Even 3.77 should make quite a difference.
1) im pritty sure bgh only ajust 1st ratios the rest is std ford ratios but some very from ford
sadly the problem with type9's are the low 1st but there are plenty of kits to sort either 1st or the complete set (£200-1300)
2) 3.54 is quiet a tall diff 3.54 in to 1 out you wil more than likely want somthing closer to 4. almost every rwd gear box i know is direct 1:1 in
4th (5th usualy .85-.75)
there is a ratio calculator herediff link scroll down to final drive ratios and
download the .xls doc
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cliftyhanger
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| posted on 28/12/13 at 10:25 AM |
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And here is a site where you can play with gearbox and diff ratios.
Preselected for triumph stuff, but you can change everything.
Not found a general version of it yet, but not looked too hard.
http://www.mintylamb.co.uk/gearspeed/
[Edited on 28/12/13 by cliftyhanger]
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rdodger
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| posted on 28/12/13 at 12:28 PM |
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http://www.car-videos.net/tools/speedrpm.asp?Car=Select&Num1=195&Num2=45&Num3=14&AxleRatio=4.1&Ratio1=3.13&Ratio2=2.05&Rat
io3=1.48&Ratio4=1.16&Ratio5=0.97&Ratio6=0.81&Ratio7=&Redline=9000&Increment=500&B1=Recalculate
Try this
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Paul Turner
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| posted on 28/12/13 at 05:42 PM |
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When I built my first 1700 x-flow Caterham I used a 3.6 diff and a 4 speed Escort Sport gearbox with 185 70 13 tyres. The combination was excellent in
all circumstances except cruising on the motorway where 70mph equated to about 3900 revs. Over the years I changed many things (including building a
new car) but I struggled to get a better overall set up than the above. Eventually I put a 5 speed BGH box in with the V6 ratios (at the time it was
his basic and cheapest option - about £550 outright in 1998 - now called the E6) with a longer first, a 3.9 diff and 185 60 13 tyres. Bingo, total
perfection. The ratios 1st to 4th were even better than the sport box and the 5th gave me about 3500 rpm at 70 mph.
Now I have the BGH V6 based box (the original box failed 3 times but he replaced each one FOC) with his closer 1st and 2nd plus a shorter 5th along
with a Zetec motor. The box (now called the E7) would cost £1385 +VAT which is 3x what I paid for the original BGH box. Are the ratios any better on
the road, in a word no.
Forget BGH, your best option for a closer ratio box is to give Steve Perks a call on 01527 894232, he can be difficult to get hold of so don't
give up. He can supply a kit that simply replaces first gear and a modified lay gear set for about £250. Allowing another similar amount for him to
build the box from your donor box and you have a box every bit as good a £1500 BGH box for about £500. Got one in the loo downstairs for when the BGH
breaks (again). If you could find a V6 donor box the ratios are even better and the cost exactly the same. Downside is either the input shaft needs
shortening (Steve should be able to get it done) or you need to fit the Caterham spacer between the belhousing and the box plus fit a 30mm shorter
prop shaft.
The Steve Perks box along with a 3.9 or 4.1 diff (depending on your diff type and tyre size) will give you a set up way better than you currently
have.
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scimjim
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| posted on 28/12/13 at 06:33 PM |
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Here's some bits I've collated for the calculators
Type 9 ratios:
1.6, 1.8, 2.0, 2.3 V6
1st 3.65
2nd 1.97
3rd 1.37
4th 1
5th 0.82
2.8 inc 4x4
1st 3.36
2nd 1.81
3rd 1.26
4th 1
5th 0.83
diesel
1st 3.91
2nd 2.29
3rd 1.38
4th 1
5th 0.82
diff ratios:
3.14 (open or LSD) - 7" & 7.5"
3.36 (open or LSD) - 7.5"
3.38 (open or LSD) - 7"
3.62 (open or LSD) - 7"
3.64 (open or LSD) - 7.5"
3.77 (open only) - 7"
3.91 (open or LSD) - 7.5"
3.92 (open or LSD) - 7"
4.09 (open or LSD) - 7"
4.27 (open only) - 7.5"
I've ignored the 6.5" diff but the 7.5" diff can be modified to fit my 7" mounting cradle quite easily - but that's not
always possible 
ETA - sorry you don't have IRS 
plus wheel & tyre sizes obviously (use tyre diameter from tech sheets where possible, not the generic percentage of width as it can vary quite a
lot)
[Edited on 28/12/13 by scimjim]
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beaver34
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| posted on 28/12/13 at 08:30 PM |
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i have a spc semi helical gear set, has long first (but thats an option) 3rd and 4th are very close and a tall fifth for more cruising
sounds perfect for what you need check there site
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