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Diff advice please - ZZR1400
f27 - 24/8/15 at 08:39 AM

Hi,

I've just had a ZZR1400 put into my Formula 27, and I thought I had a 3.89 diff in there (English axle). We used the diff calculator before the engine transplant, and it looked as though with the new engine and my 15" wheels I would have a max speed of 135ish at 15,000 rpm. After driving it for a few days now, my top speed is only about 105-110mph...

I'm now guessing my diff might be a 4.something, but either way I need to change it.

Due to it being english axle I have limited options, but it looks like the lowest is a 3.54. I know this isn't ideal as I know another ZZR1400 car running a 3.14.

I have two options and am looking for advice -

option 1 is to buy a 3.54 diff - there is one on this site for sale and one on ebay and get someone to fit it.

option 2 is to buy the internals from Quaife (also 3.54) and get someone to swap them into my diff.

Both work out at the same price without the fitting.

My current diff is an LSD, but I know very little about how all this stuff works. I know I want to keep it LSD but not sure how the above options would affect that.

What would you do?!?!!

Thanks in advance

ali f27 - 24/8/15 at 09:23 AM

Give me a ring 07933787810

minitici - 24/8/15 at 09:57 AM

A ZZR1400 doesn't rev to 15,000rpm!
(not more than once anyway....)

f27 - 24/8/15 at 10:09 AM

You're right - we put a koso dash on and the Rev counter doesn't seem to be working properly but shows 15,000 at the top of the range. Need to get that sorted too!

r1_pete - 24/8/15 at 10:11 AM

quote:
Originally posted by minitici
A ZZR1400 doesn't rev to 15,000rpm!
(not more than once anyway....)


My mates didn't, when he dropped it and the throttle stuck wide open, so much for the fuel cut off!!

I'm sure it redlined at about 11,000.

Cortina 1600E & GT used a 3.77:1 diff, not 100% sure what you refer to as the English axle but on those the diff comes out of the front.

hkp57 - 24/8/15 at 02:06 PM

If you already have a LSD and are happy its in good condition buy the open 3.54 and have the crown wheel and pinion swapped over.

Without a custom made set of gears that will always be your limit which will be a waste of that great engine.

All the race / rally ratios for that axle tend to go in the other direction above 4:1


For fast road work I would be going for a ATB diff rather than a plate diff which are quite harsh.

Another option would be for you to build an Atlas Axle, you get standard gear sets for them down to 3.09:1 ratio. Would take a fair bit of fabrication to make it work but plent rally companies out there that can build them any way you want.

http://www.evansandsonrallyspares.co.uk/index.php/axles-gearboxes/product/130-atlas-axle-3-09-cwp-set





After that its the next option of converting to IRS

[Edited on 24/8/15 by hkp57]

ian locostzx9rc2 - 24/8/15 at 03:01 PM

A 3.54 diff will give you a top speed of 120 to 125 mph which would be ok for smaller tracks .

twybrow - 24/8/15 at 05:38 PM

Is the zx14 geared very differently to the zx12? I run a ZX12 with an ATB lsd fitted into a 3.54 live axle and it will happily get to 130+mph....

CosKev3 - 24/8/15 at 07:43 PM

quote:
Originally posted by twybrow
Is the zx14 geared very differently to the zx12? I run a ZX12 with an ATB lsd fitted into a 3.54 live axle and it will happily get to 130+mph....


Is that with a speedo known to be accurate at 130mph?

twybrow - 24/8/15 at 08:13 PM

quote:
Originally posted by CosKev3
quote:
Originally posted by twybrow
Is the zx14 geared very differently to the zx12? I run a ZX12 with an ATB lsd fitted into a 3.54 live axle and it will happily get to 130+mph....


Is that with a speedo known to be accurate at 130mph?


Yes.

f27 - 24/8/15 at 08:14 PM

Thanks for all the advice. I'm also wondering if the ZZR1400 might have some kind of speed limiter on it? I've heard of some bikes been limited to 180mph and maybe putting it into a car can confuse it and make it kick in earlier? Is that why people use speedohealers

[Edited on 24/8/15 by f27]

twybrow - 24/8/15 at 08:57 PM

quote:
Originally posted by f27
Thanks for all the advice. I'm also wondering if the ZZR1400 might have some kind of speed limiter on it? I've heard of some bikes been limited to 180mph and maybe putting it into a car can confuse it and make it kick in earlier? Is that why people use speedohealers

[Edited on 24/8/15 by f27]


The zx14 is limited to 186mph as standard (triggered by the speedo signal on the bike). My Zx12 is an A1 which does not have a limiter, so it will pull to a higher top speed as stock. I wonder if with your higher gearing, that maybe why you have such a low top speed at the moment.

K13JOB - 24/8/15 at 08:57 PM

quote:
Originally posted by f27
Thanks for all the advice. I'm also wondering if the ZZR1400 might have some kind of speed limiter on it? I've heard of some bikes been limited to 180mph and maybe putting it into a car can confuse it and make it kick in earlier? Is that why people use speedohealers

[Edited on 24/8/15 by f27]


Yes, you will need the speedohealer otherwise it will limit the revs (and thus speed) quite low in top gear. I also recommend fitting a power commander.

minitici - 25/8/15 at 08:26 AM

The 6th gear top speed rev limiter will come into play at a lower speed (than 186mph) due to your different overall gearing.

As said a speedo healer will solve that problem.

The other thing to watch out is the zzr1400 speed sensor needs to pick up the correct pulses from your propshaft otherwise it puts a 9800 rpm rev limit on the engine.

The speed sensor normally picks up pulses from the end of the gearbox sprocket but if you have removed the sensor to fit a prop adapter you need to refit the sensor to get the required pulses.

minitici - 25/8/15 at 08:30 AM

One final thing - are you using the standard zzr1400 clocks?

If you are not using the clocks, you may be missing the power feed to the speed sensor as this is fed from the clocks.

If the feed is missing the ECU will again impose the low rev limit.