Fitting engine and gearbox

[Solo]

Ok, I'm after some suggestions please.  I'm in the process of fitting the engine & gearbox into my 420R.  The assembly is in the car, all mounts are loosely fitted but I'm struggling to get the gearbox centralised in the tunnel - it's touching one side and pretty close to the other.  Is it just a case of leveraging the assembly around or is there something else I need to do? There seems to be pretty much no space anywhere!  It's the new Mazda gearbox if that makes a difference.  Any suggestions welcome!  Hoping for inspiration whilst watching qualifying.

cheers

Steve

[Jonathan Kay]

I don' think there's much experience yet with that gearbox and I can't recall any special hints or tricks.

Can you add a photo from underneath of the area around the gearbox mount?

(I think it will be a case of wiggling for the best compromise.)

Jonathan

 

[Solo]

So here's a photo.  As you can see, the gearbox is too close to the passenger side.  The manual simply tells you to adjust gearbox on its slotted mountings - but there's only very minimal adjustment fore and aft on the bolts though the chassis rail and zero adjustment in the central two holes.

[Mucus72]

Can't help with the fitting, and genuinely not wanting to thread hijack when you are in your moment of need. I'm also self building a 420R next year and I am in two minds about whether to stick with the Mazda sourced 5 speed or go with the 6 speed (damn expensive option). Can you tell me your thoughts on this and why you picked this choice? With a good amount of Duratec torque I'm not sure whether the 6 speed would appreciably add more fun for track days. 

[Solo]

Re choice of gearbox, I tried box options and preferred the Mazda.  Clearly this is very subjective, but I thought the gear change was much sweeter.  On some tracks I guess the 6 speed option will be better, but I'm not fussed about ultimate lap times. On the road I think the Mazda option will be much nicer.  So, for the mix of use i will have with the car I think the 5 speed makes most sense.

I've left the engine / gearbox for now and will check with Derek on Monday. The gearbox is touching the heat shield on both sides and the bellhousing is just touching the heat shield in one place, but it is all clear of the chassis members. This is as good as I can get it and will double check with Caterham before I start connecting everything!

[Mucus72]

Thanks Solo. Good luck with the ongoing build! Is there a blog of your efforts we can follow?

[Jonathan Kay]

... and I am in two minds about whether to stick with the Mazda sourced 5 speed or go with the 6 speed.

What final drive ratio are you thinking of? And where in your priorities is relaxed cruising at, say, 70mph?

Jonathan

[Mucus72]

Don't really know anything in detail about the final drive ratio differences of the boxes. My old K series was a 5 speed and I was happy. I spend more time on track than on the Queens highways though. However, I've had a few tours over the years and will be attempting the highland 500 next year after the build. But I picked R pack over S pack. I kind of sit on the fence Jonathan. 

[Alan Reeves]

Steve I have been helping with a 360r build and that box is tight ! but as you say its not hitting the chassis

so I would not be that concerned...im back on it tomorrow and I will take another peak at how this one sits etc.

as for boxes, I had a 175 sv 5 speed and borrowed a 6 speed at the time...i prefered the 5 , much sweeter rev band for the road

but the 6 speed i am sure makes a better track car...

i happen to have a 6 speed in my CSR and have changed Diff ratios as I did not like the high revs

that the 6 speed creates unless you specify a higher rear end.

alan

[Mucus72]

I see from another post that the Mazda 5 speed ratios are: Ratios 1st 3.136 2nd 1.888 3rd 1.330 4th 1.000 5th 0.814

Does anyone have the standard 6 speed ratios close to hand please for comparison?

[Mucus72]

Ahah found them: 1st 2.69 2nd 2.01 3rd 1.59 4th 1.32 5th 1.13 6th 1.00

[Jonathan Kay]

AMENDED: Crossed post.

...

I think it's:

1st 2.69:1
2nd 2.01:1
3rd 1.59:1
4th 1.32:1
5th 1.13:1
6th 1.00:1

Jonathan

PS: What's the best online gearing calculator at the moment?

[Mucus72]

So there's a big gap between 1st and 2nd in the Mazda 5 speed. Everything is much closer in the 6 speed, and 4th in the Mazda is the same as 6th in the 6 speed so it will be revving it's nuts off on the motorway.

I'm aware I'm giving a rubbish assessment here. Can someone who knows what they are on about break down the issues with each of these from a ratio perspective, assuming that we are not changing diff ratios?

[Jonathan Kay]

The key question for cruising is the engine speed at 70 mph. It's widely reported that the non-overdriven top in the 6 speed gearbox and commonly used final drive ratios are a problem for that. 

For the other factors it is worth using a calculator that will show all the engine speed drops.

Jonathan

[Mucus72]

I found this and am trying to work it out: http://www.cargister.com/calculator-gear-ratio

[Mankee]

This thread is going proper off-topic, but here goes...

As fun as I think a 6-speed box is, every extra gear requires time over a 5-speed box. I know that trackdays aren't for timing though. But considering piling into a big braking zone from big speeds into a hairpin and having to drop 3 or even 4 gears. My brain and limbs can't cope with heeling and toeing my way that far down the box and I don't really like block-changing.

The 6-speeder was designed for the old 1.4SS K-series to keep it on the boil. I spoke to one of the engineers who designed the Mazda 'box fitment and, as shown by the ratios above, they are much more suitable compared to the old Sierra box with a silly short 3.65 1st and even the V6 3.36 1st isn't that much more cop.

I use this gearing calculator tool:

http://www.gearboxman.co.uk/inforatios.html

Well, I used to use it when I was perving over aftermarket Type 9 gear clusters, but I've now made my choice for the use my car gets and am sticking firmly with it.

[craigyb]

I'm going to start another thread on this

[Mucus72]

Yep, sorry to the OP Solo, completely my fault

[Solo]

Thanks to those who contributed here and to the two people who sent me private messages.  

I spoke with Derek today and he confirmed that everything is ok.  For the benefit of others who fit a Duratec / Mazda combo in future, it is normal for the gearbox to be in contact with the heat shield all along the passenger side of the tunnel. Equally, the bellhousing pretty much touches the front of the footwell on both sides. It's reassuring to know that this is normal, but it still seems odd that everything is so very tight!

cheers. 

Steve

[Jim 123]

What does the feedback from Derek suggest about future access to the Gearbox Filler Plug, i.e. it still accessible for top up?

[Jonathan Kay]

Thanks for posting about the heat shield. That will save others a lot of time.

On Jim's point: do you know about the traditional solutions to topping up? 

1. From underneath with restricted access.
2. From the cockpit through a purpose-made hole.
3. From above through a non-standard cover plate with a filler and dipstick.

I don't think anyone's described which of these are transferable to the Mazda box. Is there a filler plug somewhere?

Thanks

Jonathan

[7 wonders of the world]

In your position I'd be ordering the basic stock 5 speeder (cheapest option) and then take it to Steve @ SP Components and have him build it with one of his helical kits with the 2,29 1st gear, you can even opt for an alloy case too.

Vastly superior box box to the 6 speed and much better ratios and a massive wright saving over the Mazda too.

http://www.spcomponents.co.uk/