Gearbox effeciency

[pstreat]

Hi all,

I am trying to track down some sort of comparison of effeciency of racing boxes specifically in respect of those used in Sports 2000.

The rules for the Duratec class allow 5 speed boxes (sequential or H pattern) with no LSD.

The general range of boxes seems to be:
Hewland MK9 (older converted cars)
Hewland JFR (5 speed sequential)
Hewland FTR (6 speed sequential with one not used)
Elite (5 speed sequential - not sure of which model but seems most common)

I have heard it said that the Elite drains more power than the Hewlands, and even that the old mk9s/LD200s are more efficient than the sequential boxes (no paddle shift/flat shift is allowed).

Does anyone know any actual facts on this? Are there any comparisons anywhere?

I guess this is relevant to any 5 speed rear engined sportscar/single seater class so hopefully someone will have some insight

Thanks

Paul

[Peter Mallett]

Welcome pstreat.

We have a member who races a FF2000 and preps everything from Radicals to Lotus X1 via S2000. look for Delta in the members list and pm him.

Mention my name too. You might get a discount.

[THR]

i heard that the sequential ones are less efficent, altho i cant really think why that would be!
Got a massive JCB gearbox in the workshop at the moment, its the same principal .. just bigger !

[Clive Brown]

Does anyone remember the old Staffs Silent Gears 'boxes ? I think they were the first people to mount any real challenge to the erstwhile Hewland monopoly .

IIRC , in the 70s and 80s the hot cheat in the restricted ( hah! ) formulae like FF1600 , FF2000 , and S2000 , was to run a 5 speed Hewland with no reverse . After a while , the scrutineers got wise to this , so teams changed the gearbox internals after scrutineering , but before practice . Allegedly , another good way to cheat was to use the Hewland cam-and-pawl differential , and assemble it with thick grease so that if the scrutineers checked it cold , the pawls were held in by the unmelted grease so that it behaved like a free , and hence legal , diff .

There were some legal stratagems , too . A common one at Mallory , Brands and Lydden , to name but three , was to run a tall first gear in practice for use at the hairpin on these circuits to secure the optimal grid position . For the race , you put in a conventional four-speed ratio set with a first gear more suited to getting the car off the line at the start of the race . The other stunt that springs to mind was running the free diff Hewland Mk.8/9 not on the recommended EP80 , but on ATF , to reduce internal friction .

All of this is of course water under the bridge , for in these enlightened times , no-one would think of cheating now , and even if they did , the scrutineer of today is far too intelligent and diligent to allow miscreants to evade apprehension .

[jedrinck]

What does running a gearbox without reverse do? Is it just done to reduce rotating mass? What happened to a guy who spun out and would have needed reverse? Fairly obvious if he didn't have it then.

[phoenix]

Funnily enough, when I read the question I went and did a Google for the Staffs Silent Gear company! Couldnt find them though.

First of all, there is no reason I can think of why a sequential gearbox would be less efficient, or introduce more drag, than an H pattern gearbox - the gear change itself has no effect on drag that I know of.

I believe that straight cut gears have lower drag than helical, so that is a good thing to look for. The Elite being a production gearbox is probably at a disadvantage as it has helical gears. If you can get straight cut gears for it, however, it might be more efficient than the older Hewlands - who knows? Bearing size and quality have an effect on drag too.

Not over-filling with oil eliminates drag. Running engine oil instead of gear oil - cuts down drag - and some FF people used to do that - but I guess wear rates due to shear and overheating could be an issue.

Warmer oil has less drag than cold, so don't run a gearbox oil cooler without a thermostat correctly set. Best bet must be the lowest viscosity proper gear oil you can find. Better than that is dry-sumping the gearbox and using spray lubrication rather than splash lubrication, which is what most gearboxes use.

From memory I think that in a Mk8/9 hewland the reverse idler gear is always engaged, so removing reverse eliminates that.

A Hewland sounds the best bet - and I wouldn't worry about the sequential causing power losses, unless someone knows that that they do?

[jerryk]

the most efficient gear is usually 4th , the one that is direct drive , any other transfers power through the lay shaft and this uses a lot of power . years ago a friend who worked for Recardos ran some motorcycle gearboxes on a dyno and 2nd and 3rd could absorb up to 10% of total power .

[pstreat]

Thanks all for the info.

Interesting the comments about the Elite helical gears as it is specifically the Elite box I have head is less efficient.

As always I remain amazed at the lengths people go to in order to cheat! On a legal note though running a long 1st in qualifying sounds like a genius idea!

It does sound like hewland boxes remain the way to go though!

Cheers

Paul

[Tony C]

You may find that some of the LD and Mk9 boxes are running 4 speed which would reduce drag but I could not imagine hewland building a new box that was less efficient than the older one.

In formula ford (and similar categories) there have been many 'tricks' used.
4 speeding the box in qual.
Running a zero weight gear oil (and 30 weight in engine) during qual.
Leaving reverse out.
'tight' bearings in diff (artificial locker).

It depends on whether you are racing for sheep stations or fun!!!

[Splatz the Cow]

Originally Posted by jerryk

the most efficient gear is usually 4th , the one that is direct drive , any other transfers power through the lay shaft and this uses a lot of power . years ago a friend who worked for Recardos ran some motorcycle gearboxes on a dyno and 2nd and 3rd could absorb up to 10% of total power .

Hm, interesting you mention that. I didn't know that till now.

At Le Mans the McLarens used fourth gear for many corners where other cars went down to 3rd and 2nd. Of course the obvious payoffs were to limit rear tyre wear and powero'stear; extend fuel mileage; and use the engine's torque.

The road derived car was naturally rough on its gearbox through some of the GT rounds, so using fourth may have helped ease the strain on the gearbox over the 24Hrs, where they were not the quickest, but did last in the end.