Six speed gearbox in a BDR?

[anthonym]

Is this a good idea? Will it fit?

 

I have a BGH in it (lengthened 1st, the Sierra box I think - is that the "type 9" I keep seeing mentioned?) which has done only a few hundred miles, actually maybe a very few thousand. Calais and back once or twice. Anyway, not far for a gearbox.

 

I've always wanted to do it - though cashflow remains the issue of course. My question has always been whether this would transform my experience of the car - which is that it's always in the wrong gear (well, between gears that it doesn't have) except motorway cruising which is fine - and a six speed doesn't have "overdrive" so that might be a bit of a pain (on my pocket and ears).

 

What experiences ho?

 

Anthony

[rgrigsby]

Anthony I've had quite a few different gearboxes in my car over the users starting with a standard "Type 9" 5 speed, then a 6 speed and now a BGH sporting close 5 speed.

 

Could of questions, what ratio diff have you got? 3.92 I would guess

 

What does you engine rev to? where does it "need to be" in order to have fun?

 

A 3.92 diff and a 6 speed box is excellent if you have a revy engine that needs to at 5k plus all the time, I had my 6 speed with an all steel 8.5K rpm crossflow and it was fantastic on track although very hard work (and very entertaining!) on the road.

 

Is your BGH box just a lengthend first or have they tweaked 5th as well? I'd definetly recommend having a long chat with Brian at BGH before doing anything, if you describe your typical usage and your engine characteristics to him I'm sure he'll have a few ideas.

 

Cheers

 

Rob G

www.SpeedySeven.com

[anthonym]

hi Rob, just the man to be passing by by the looks of it :-)

 

let's see:

Diff is whatever was bog standard in 1987..

Revs to max 7 say 6260 The fun is 5 - 6 I guess (it's been a while)

BGH is just a tweaked 1st - what's the 5th tweak?

Yes chat with Brian: very good idea .

 

thanks :-)

 

Anthony

[Alex Wong1697456877]

I had a 3.92 with a Quaife T9 and it was a good match. I now run a six speed with a 3.38 which is als good for my Vx. See http://www.blatchat.com/T.asp?id=149610 for the maths.

 

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[rgrigsby]

Hmm ok I'm guessing you'll have a 3.92 diff, you could fit a 6 speed with the diff/engine combo but it will be pretty manic most of the time.

 

You're BDR sounds very similar to my tweaked RK155 spec crossflow I ran years ago, that seemed to be quite happy with a standard 5 speed although there was a bit of a gap from 1st-2nd.

 

You could fit a 6 speed and change the diff to a 3.62 but tbh I'm not convinced it's the best solution, I'd have a chat with Brian and see what he suggests.

 

Cheers

 

Rob G

www.SpeedySeven.com

[anthonym]

it's the gap 1st to 2nd that the longer first was intended to deal with - and there's an awful crunch if I make the change too quick (Brian has said to take it back for a look, but I kind of left the country and have not had the chance). Keeps coming back to a chat with Brian. :-)

 

Yes I was thinking 6 speed might be a bit manic (nice choice of word) with no "overdrive" 5th. I can't help wondering how that (i.e. BDR mit 6 speed) might be different or the same as R500 with 6 speed as regards cruising experience.

 

Anthony

[Willie.]

The 6spd is super on any engine with a narrow power band, so you don't drop too many revs when you change gear (So you stay in the power band).

 

If you're changing gear and dropping out of the power band, you need closer gears. You should download gearcalc (Email me and I can email you a copy tonight) and have a look at your current setup compared to a 6spd setup.

 

sorry if this goes off topic>

 

A with a 3.92 diff, you'll be about 4k rpm at 70mph with the 6spd. It is quite noisey, but if you don't do much touring, its fine.

 

Willie

[Bilbo]

anthonym

 

My BD is peaky and I have already changed to a quaife close ratio 5 speed. I thought about a Caterham 6 speed but its rather set up for a 3.62 and that leaves me back where I started.

 

Currently its fine on the road but not all I want on the track. I was going to change to a 4.44 diff but after the problem with my feet I never did it. I would loose top end but the power would be more usable on track and sprint days as I would always be much higher in the rev band for the same speed. the downside is motorways would become a bit of a pain on the ear.

 

I would say 3 different rolling roads have recommended either a 4.44 or a 4.11 diff.

 

I have the following gear ratios 2.2 1.54 1.21 1.1 0.93 if I change to a 4.44 I would prefer a 2.04 1st gear but that is an expensive modification as the gears on the main shaft. here

 

If you have loads of money the is interesting here with 2.4 1.694 1.333 1.15 1.1 0.888 and retain the 3.92 diff 🤔. I have not played with the gear ratio programs in case I get too tempted

 

---

'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? engineered by Roger King, on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension.

 

 

Edited by - Bilbo on 12 Nov 2008 20:28:21

[elie boone]

My BDR only has 170bhp and a rev limit of 7200, diff is a 4.11 live axle and the box is a 5spd sc cr. I can cruise at 30 in 3th and accelerate away without hesitation, i don't feel the need for a 6 speed due to the flat torque curve. Maybe thats the problem, it's not savage enough 😬 or its me not trying hard enough.

[Bilbo]

anthonym

 

Your what is your BHP and at what RPM 🤔

 

Elie

 

My engine is not too steep until 70 BHP at 3900rpm then steep but still only 119 BHP @4900 rpm and by 5500 its near 143 BHP then slows down a bit hitting 200BHP at 7750rpm with the limiter at 8200rpm. So on the track you need to be always at least between 5300 and 5500 rpm out of a corner. That is not as easy as it sounds noticeably a bit dead in the water out of the hairpin before the straight at Curborough changing up drops you down to say 4000rpm and around 70 BHP or worse.

 

anthonym does this sound like your problem 🤔

 

Changing to a 4.44 from 3.92 with my CR box lower would you speed by 10 MPH for the same RPM so for the same speed you’re 700ish RPM higher in the rev band or better as gear calculators can be very misleading and my rears are 225 x 60 x 13

 

Have a look on Arnie Webb site it has a better gear calculator than the Quaife one ❗ that only gives speed and RPM rather as max in each gear. Remember its ONLY theory of gears rather than the reality of a car on a road also note that it assumes just 200 rpm on a change that’s a bit low in my opinion so set your change 200rpm above your max power rpm.

 

 

---

'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? engineered by Roger King, on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension.

[anthonym]

My BDR sounds like Elie's: 169 BHP . The drop is massive between 1st and 2nd, and I have great difficulty not crunching 2nd. Honest guv it's the fault of the gearbox. :-) I find it very frustrating.

 

I have a dyno report (that's how I know it's 169 ) if I can find it, with graph. I have no idea where it is, have to have a think... haha, I have an idea. We'll see.

 

Diff not changed since built from the kit (by Geoff Mansell)

 

Anthony

 

 

[Bilbo]

Hi anthonym

 

Well I ahs assumed BHG gear clusters were very similar to Quaife but look

here I see they are not ❗

 

Theres a bigger difference between 1st and 2nd. This does make the rev drop more but enables you to pull away at a lower rpm.

 

You do need to play with the gear calculators its the only way to see the differences.

 

I find the 2.2 1st is fine with the lightweight 7n and can just about hit about 60mph 1st makes a great 0-60 time Still thats only part of the story as you may want to change well before max rev if the backs going light then your much lower in the rev band and less power the sames true in all gears.

 

The rear calculators are not perfect as they do not allow you to put in BHP/rev other than at max.

 

Also tyre diameter is part of the overall gearing are you running 13" rims 🤔 Interestingly my AO48 225/60/13 have about the same overall rolling diameter as the old pilot 185/60/14 rims ❗

 

So what are your tyres and gear cluster ratios 🤔

 

You also have to think in all of this there is driver preference and what you like I might hate that does not make either of us wrong

 

---

'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? engineered by Roger King, on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension.

[anthonym]

I wonder if it's as simple as an even longer first gear... I mean I can start in 2nd as it is.

[Mick Day]

Good gear calculator here

[anthonym]

Thanks,

[anthonym]

it's been a long time since I drove my BDR, I am wondering if it is possible that I simply do not leave it in first long enough (a habit I have in most gears) and as such I am greatly increasing the "drop" between first and second..

 

the other thing is I find that particular change in that car using that 'box to be one where I am often "crashing" the gear change (1st to 2nd). Is that really all me? I'm no longer so sure.

 

Anyone stories to relate of a like kind?

 

Anthony

[Bilbo]

anthonym

 

You should not be getting a any problems changing from 1st to 2nd. 2nd to 3rd maybe as you need to cross the H... particularly if its square cut with the standard gear lever

 

BDR's like to be revved You do not have a lot of power low down or torque.

 

Still having said that you should be easily able to change from 1st to 2nd at 2000 to 2500 rpm. Think when mine was a standard BDR it was that in town and normal driving 3500 upward in any gear still we all drive a tad different

 

Have a look at the gear stick they can come a bit loose I have had that a couple of times but no more than that.......... If you have the standard gear stick Quaife do a much better one here maybe BGH do as well 🤔

 

Its also worth checking that the little plastic err clip under the gear stick is in place and not broken

 

A change in 1st gear means a new main shaft in the box so expensive see my earlier post

 

Could you post which gear cluster you have at present is it square cut 🤔 and BHP

 

---

'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? engineered by Roger King, on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension.

 

Edited by - Bilbo on 11 Apr 2009 18:06:07

[Normans_Ghost]

Anthony, speak to Brian at BGH and get the ratios changed. In my opinion the BD doesn't NEED a 6 speed as the power band is much wider than the R500. You can see that for yourself.

 

I've got a 4.44 diff and a BGH ultra close ratio set with a .86% 5th.

 

Bearing in mind I'v a lot more power than the standard BD it's very quick off the line. The gearing change dropped top speed from 151 to 134 but it's worth it.

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited

[anthonym]

good morning both,

 

bilbo,

Judging by the noise it's not straight cut.

The box was built by Brian BGH with a long first.

BHP is 169 on the dyno.

 

Norman, You have reminded me I did speak with Brian some years ago now and I was supposed to take the car to him; I've just not been there to do that.

He is somewhere South on the route to Dover so I'll factor that in somehow.

 

Anthony

 

 

 

[Bilbo]

Hi

 

Well if its not square cut there’s no reason for you to have any change problems in any gear ❗

 

I would start by looking at the gear stick but as I said the Quaife one is a lot better.

 

BGH

Unit 8

Verralls Business Centre

Maidstone Road

Cranbrook

Kent

TN17 2AF

Tel: 01580 714114

 

From the web site the long 1st ratio’s on that site are 2.83 1.81 1.26 1:1 and 0.82 there is another option but you have more BHP. I think you need to talk to Brian to be certain which cluster you have fitted.

 

The close ratio option is 2.66 1.75 1.26 1:1 and 0.82 or a 2.75 1st

 

Mine is 2.2 1.54 1.21 1.1 0.93 but not relevant as it’s a Quaife box and has a longer 1st gear.

 

I will have a play with the gear program post something tomorrow.

 

Norman what gears do you have 🤔 2.66 must be very brief with the 4.44 🤔

[Normans_Ghost]

It is and there on here somewhere.

 

I'll have a search later.

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited

[Normans_Ghost]

here

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited

[Bilbo]

Hi

 

Well assuming you have the standard 175 x 60 x 14 tyres you 170BHP is at 6250 rpm and you change at a max of 6500 rpm I know you said its good for 7000 rpm but there is no more power over 6250 rpm in fact could be less

 

So changing at 6500 with 2.83 1.81 1.26 1:1 and 0.82

 

1st to 2nd rev drop 2253 rpm

2nd to 3rd rev drop 1899 rpm

3rd to 4th rev drop 1290 rpm

 

As you short shift in 1st say at 25 mph it drops from 4060 to 2597rpm

 

Now as the engines has been on a dyno you should have the numbers or graph of power v rpm

 

If not I have my old figures err somewhere and I was going to write something when actually looking at it

 

So look at the plot and see how much power/ torque you have at 2597rpm

 

Then look at where say 100-110 BHP is on the graph and change so you always above that rpm as a minimum in the next gear or at the point where there’s no dips in the curve. If you do not have a graph only numbers then draw one in Excel

 

That way you will keep the engine on the boil and not needing to get back on the power curve of the cam that should help with the "it's always in the wrong gear"

 

The other options to go for mine or Normans gear set up

 

---

'Can you hear me running' ......... OH YES and its music to my ears 😬 😬 😬

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? engineered by Roger King, on Weber's with Brooklands and Clamshell wings, Freestyle Motorsport suspension.