Yeah, probably has something to do with the applied force being shared between the meshing teeth.. more teeth meshed in a helical set means less wear per tooth which means longer life.. I suppose

So what's all this noise (pun not intended) about straight cut drop gears then? Is that application susceptible to end thrust causing increased bearing wear? (I read something about the drop gears being a weakness in the A-series design, but I can't remember why)..

Oh, and sorry for the hijack!

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Simon

The adventures of an owner builder in the Tallarook Ranges

Aftermarket gear sets should be made of stronger materials to make up for the higher shear stresses associated with straight cut gears. If they are made of the same materials then straight cut can't be stronger, it doesn't make sense as the shear planes are smaller and the torque transfer is more intermittent.

The main problem with the Mini box is gear separation, either due to wear or from casing distortion. Once this happens then the contact point on each gear moves further toward the tip and this increases this shear stress dramatically at the root, shearing the teeth off.

Building a box with new bearings and layshaft will give a good service life but at high torque levels its possible it will still come undone.

Straight cut gears produce low thrust loads and result in less power loss, generating less heat as well.

Daniel

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Videos - Turbocharged A-Series on Dyno & at Wakefield
Mafs waz not my strong subgeckt at skkol

Port injection is a waste of time, the common opinion is port injection will reduce fuel consumption, as most commerical systems inject fuel on a closed valve, and thus the fuel atomizes nicely as it warmed by the valve.

However port injecting in a siamese head is pointless, as you can't injected on a closed valve. you have to use tuned seqential port injection, which would injected on a open valve to prevent charge stealing.

Mega squirt can't do tuned seqential port injection, and thus even on a 8 or 7 port head, is just going to batch fire on all 4 ports. It has only 2 injector channels.

The reason for going to fuel injection in turbo, is easy of setup for blown threw setups (people disagree, but in my humble opinion, blown threw is better as it prevents the fuel from being thrown out of the air), no need for special carb work. Also it allows highly specific turning, and also as protection factor if a knock sensor is fitted, it can detect and retard ingition.

Go for the 1275, and if you go 8 port, you'll need a plenuim with mega squirt.

And as it is a mini look at microsquirt, it's what i plan to use for my injection/ignition setup.

I was under the impression I could batch fire in pairs with megasquirt. Ie. 1 + 4, 3 + 2. But isnt batch fire how most efi setups work?

I know sequential is what would be the best setup, as if setup properly is most efficient and all that, but what will work with megasquirt and 8 port?

I slightly disagree. If the inlet valve is open or closed it is still hot and helps to atomise the fuel irrespective of the time it's injected, however this is not the reason for port injection.

If you have the injectors anywhere else then the manifold must have turbulance to keep the fuel in suspension, this means lost power or fuel distribution problems if it's not employed.

New cars are using fuel injecting direct into the cylinder. The atomisation issue is therefore a spray pattern issue, not a heating issue since they don't spray onto the valve at all.

Using EFI is not for fuel consumption, it's about managing the tuning requirements in real time. Carby's cannot achieve the flexibility of different fuels for example, with the right managment system it will adjust to suit 91 or 95 or 98 if required. There is no leaded fuel anymore and pretty soon there will be all sorts of fuel blends given the current climate, what are people going to do then, adjust their SU's at the servo?

Regards

Daniel

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Videos - Turbocharged A-Series on Dyno & at Wakefield
Mafs waz not my strong subgeckt at skkol

For a 4cyl turbo you will have relatively large injectors so at idle & low throttle openings it obviously would be best to have sequential to fire the fuel at the correct time to not have it sitting in the manifold.

Running the batch fire will be ok for port injection on the 8-porter, obviously some of the fuel will evaporate (and not burn), fuel consumption may be slightly higher but I doubt you will notice.

The biggest problem with running a turbo is the reduced compression ratio, this is more of a problem for fuel consuption/economy than anything else, except when under boost conditions of course.

Regards

Daniel

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Videos - Turbocharged A-Series on Dyno & at Wakefield
Mafs waz not my strong subgeckt at skkol

You can batch fire like that, but isn't ideal.

Have a look at vemms it a offshoot of megasquirt, it documentation is not the best.



Completely agree, in closed loop operation of efi it is very adapterable. This does however require a exhaust oxygen sensor. It the reason why i plan to TBI on a small bore, and just change ejectors over when i convert to big bore.

Any more details on vemms, has a quick google but couldn't find anything.

Nevermind, but for anyone else interested:
http://www.vems.hu/wiki/index.php?

sorry for the spelling mistake.