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Helical Gears And Forces Induction


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#16 JonnyAlpha

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Posted 31 December 2021 - 12:39 PM

 

 

Don’t just look at the speed in top as all 4 speed boxes are 1:1 helical or straight cut. It is all the other gears you need to look at. A SCCR box with a 3.1 CWP can make first gear fun and a right pain to use.

that standard set up is stronger than many people think.

remember the Metro turbo only changed the bearing size for the input gear nose in the transfer housing.

work out it all out before spending

for example if you have no torque below 3k a standard box means it would be fun until about 15mph while the MiniSpares clubman gear set raise it to about 20mph now if you live in the country this will not be an issue. But town/city traffic.

again I have no idea about how your engine will work but you need to consider it all. Is the 3.1 correct for the box you need?


The AC RS Cam delivers power from 1250 - 6000 RPM

From AC's documentation "In a typical example build (1293 to 1330cc) this cam will deliver 83 to 85bhp with a gas flowed head and 84 to 86lbft of torque with a single HIF44 SU and a typical stage 1 kit fitted. Power would rise to a typical 92 to 95bhp with the addition of 1.5 rockers on the same engine."

Before adding the SC, I will be porting my head and using Metro Triple collet Valves (35.6mm Inlet and 29.2mm Exhaust). I will also hopefully be fitting a set of AC's zero tolerance 1.3 Rockers. Weber 45DCOE with the long inlet manifold, LCB and RC40 Exhaust.
This should produce around 85 lb/ft Torque.

I have been advised that, in preparation for going Forced Induction, I should swap the 3.44 Diff to a 3.1.

So will the Eco Primary / Eco 1st Motion Gear on a standard A+ box DAM 5262, with the 3.1 Crownwheel be suitable?

The power band is that, but doesn't suit boosted applications. You need to reduce the valve overlap, not many N/A cams provide that as they rely on scavenging to clear the cylinder and draw air in during the exhaust stroke.

 

 

Steve,

 

I spoke to AC and he said the Cam would be OK but the FI Cam would obviously be better.

Here are the specifications. Is the overlap shown? I understand that this occurs when both the Inlet and Exhaust valves are open at the same time?

 

A6Z9dgD.png



#17 GraemeC

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Posted 31 December 2021 - 01:24 PM

So in your first comparison, with the Eco drops the speed in each gear is higher for the same rev point.  So faster speed but slower acceleration.  There will be a point, even with the FI that the acceleration becomes too slow.

 

Looking at your second comparison, they are almost identical.

 

So - I would build the gearbox with the 3.44 and normal 1:1 drops which will be good for whilst your are NA. Then when you go FI change the drops to the Eco ones which will give you the same result as having a 3.1 would, but without the hassle of splitting the engine from the 'box and having to undo those tight nuts again.  In fact it can probably be done without removing the engine from the car.

Fit the appropriate speedo gears as needed each time - again these can be changed without removing the engine.



#18 JonnyAlpha

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Posted 31 December 2021 - 03:43 PM

I have already taken the 3.44 Diff out and it’s packed up ready to send to John Guess who has a 3.1 to swap out. At the same time he’ll be fitting a X Pin.
I I stick with the 3.44, I only have Eco Helical Gears and would need to buy a set of 1:1 Drop Gears only to swap them if I don’t go FI from the outset. I’d prefer to build the engine / gearbox ready for FI and if I cant fit the Supercharger straight away, take the hit.
So two questions:
1. What would be the best Diff and Drop Gear setup for this engine when it’s Forced Induction.
2. Are A+ Helical Gears suitable for a engine outputting 130ft/lb or do you absolutely need straight cut?

#19 GraemeC

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Posted 31 December 2021 - 03:49 PM

In that case go with what you have - no point in sourcing other parts only to then find you may not be happy with the performance. Fit what you have, drive it for a bit and then decide whether or not you want to change anything. 

There is no 'best' combination as everyone has a different want from a cars performance, but the 3.1 with eco drops will give you a car that cruises well, however the acceleration will be a bit more sedate, especially when NA.

 

The A+ helical gears will be absolutely fine.



#20 Steve220

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Posted 01 January 2022 - 12:10 PM

 

 

 

Don’t just look at the speed in top as all 4 speed boxes are 1:1 helical or straight cut. It is all the other gears you need to look at. A SCCR box with a 3.1 CWP can make first gear fun and a right pain to use.

that standard set up is stronger than many people think.

remember the Metro turbo only changed the bearing size for the input gear nose in the transfer housing.

work out it all out before spending

for example if you have no torque below 3k a standard box means it would be fun until about 15mph while the MiniSpares clubman gear set raise it to about 20mph now if you live in the country this will not be an issue. But town/city traffic.

again I have no idea about how your engine will work but you need to consider it all. Is the 3.1 correct for the box you need?


The AC RS Cam delivers power from 1250 - 6000 RPM

From AC's documentation "In a typical example build (1293 to 1330cc) this cam will deliver 83 to 85bhp with a gas flowed head and 84 to 86lbft of torque with a single HIF44 SU and a typical stage 1 kit fitted. Power would rise to a typical 92 to 95bhp with the addition of 1.5 rockers on the same engine."

Before adding the SC, I will be porting my head and using Metro Triple collet Valves (35.6mm Inlet and 29.2mm Exhaust). I will also hopefully be fitting a set of AC's zero tolerance 1.3 Rockers. Weber 45DCOE with the long inlet manifold, LCB and RC40 Exhaust.
This should produce around 85 lb/ft Torque.

I have been advised that, in preparation for going Forced Induction, I should swap the 3.44 Diff to a 3.1.

So will the Eco Primary / Eco 1st Motion Gear on a standard A+ box DAM 5262, with the 3.1 Crownwheel be suitable?

The power band is that, but doesn't suit boosted applications. You need to reduce the valve overlap, not many N/A cams provide that as they rely on scavenging to clear the cylinder and draw air in during the exhaust stroke.

 

 

Steve,

 

I spoke to AC and he said the Cam would be OK but the FI Cam would obviously be better.

Here are the specifications. Is the overlap shown? I understand that this occurs when both the Inlet and Exhaust valves are open at the same time?

 

A6Z9dgD.png

 

Any cam will work, however I always try to maximise and benefit the engine's potential. I don't think you can work it out from that table.



#21 REDICE

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Posted 11 January 2022 - 07:19 AM

add to the whine. just like your chips straight cut are better.






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