Powerlite high torque starter motor

[dmitchell]

I have just fitted a new Powerlite RAC404 high torque starter motor to my 1973 series 3 V12 automatic transmission etype.
When test driving the starter motor pinion touches the drive plate ring gear. I have removed the new starter motor and measured the distance from the end of the pinion to the flange at 18mm, I have checked my original Lucas starter motor and the distance is 11mm which explains why the pinion contacts the ring gear.
I have called Powerlite who were very helpful and advised me that there should be a 10mm spacer between the starter and bell housing, I advised them that there was not a spacer fitted on my vehicle and none is shown in the V12 Jaguar parts manual that I can find.
I also asked if there was any difference between the ring gear position on a manual or automatic transmission engine and appropriate starter motor, they said not.
Has anyone had any experience of this situation as advice would be appreciated.

[phil.dobson@mac.com]

Yes but not on a V12. Not that you want to hear this but having tried these replacement starters from a number of manufacturers I am totally convinced they are a waste of time and effort. In the case of the later etypes the original is perfectly adequate. Always ask yourself 'what problem am I trying to fix'
Forget the weight saving. Forget the lower current consumption.
Just my experience.
Best regards
PAD

[MarekH]

What the people at Powerlite meant to say was "Our starter motor doesn't fit your car, but it will if you fit the 10mm spacer which we should have provided with the starter. Sorry, here's a 10mm spacer for you."

If you want to read my thoughts on these starters, on the jag-lovers.com forum, search for "starter, MarekH" or some other similar search term.

kind regards
Marek

[abowie]

Forget the weight saving. Forget the lower current consumption.
PAD

What he said.

[mark10337]

On cold winter days I'm very pleased I have my lower power, geared, high torque starter motor. It is massively superior at cranking the car than the original. Depends what problem you are trying to fix...

[Hugo]

I would have thought the main gain is that they are more efficient & suck less power from the battery. This can and will make the difference between go/nogo in a marginal situation.

[chrisfell]

Those of us that have fitted these will attest, the main advantage is starting speed - the speed it turns the engine. Mine is so quick that there is enough fuel air mixture to fire on the second or third compression. In other words my engine fires from cold in less than one revolution. The old starter required two or three revolutions, at least five compressions, before it drew enough fuel to fire. The draw in the battery, the weight saving, these are additional benefits, but not the main reason to fit.

[Hugo]

I would think the slower starting with the old starter has as much to do with the amount of current it is sucking out of the coil. Engines don't need to turn over fast to start as long as there's a healthy spark.

[chrisfell]

I would think the slower starting with the old starter has as much to do with the amount of current it is sucking out of the coil. Engines don't need to turn over fast to start as long as there's a healthy spark.

That, and the speed of air drawn through the carbs.

On the subject of starting an E-Type with SUs, I have never opened the throttle when starting. My engine will start just with the lowered jets and slightly opened butterflies.

[Hugo]

You'd be surprised - the old hand cranks were quite fast enough. Older engines had smaller venturis (venturii?) of course, and when the throttle is closed or almost closed it will such enough fuel out of the jets.

[Mark Gordon]

I would think the slower starting with the old starter has as much to do with the amount of current it is sucking out of the coil. Engines don't need to turn over fast to start as long as there's a healthy spark.

That, and the speed of air drawn through the carbs.

On the subject of starting an E-Type with SUs, I have never opened the throttle when starting. My engine will start just with the lowered jets and slightly opened butterflies.

Pushing on the throttle pedal with an SU carb does nothing until a significant amount of air is drawn through them once the engine is running. That causes the piston to rise and allow more air/fuel to pass. The first setting on the choke lowers the bridge and enriches the mixture, so it's not a true choke in the traditional sense of restricting air flow to pull more fuel past the jet. The proper procedure for starting a cold Series I E Type is gearbox in neutral, foot off of the clutch pedal, choke on (amount depends on ambient temperature, but I just set it "full on"), ignition switch on and allow the carbs to charge (wait until the fuel pump ticking stops) and then push the starter button. A properly set up ignition and carburation system should allow instant starting; after sitting for a week regardless of the ambient temperature (as long as it's above freezing), my engine with its original Lucas starter fires in less than two seconds of turning.

[Hugo]

I'm not sure that is totally correct. I think you will increase the airflow simply by opening the butterfly, even if the piston initially stays where it is. Not by much, maybe, but enough to make a difference. I think.

[MarekH]

Absolutely correct Hugo. You get tons more airflow if you open the throttle. The carburettor piston then has no choice but to move to where the air pressure difference between the top and bottom of its rubber diaphragm dictate it must and that is a function of manifold vacuum.

Airflow is also the way to hot start a carburettored v12 - you clear out the plenums, move new fuel and plenty of it through the manifolds and into the cylinders with airflow.

What the high torque motor does for you is buy you a bit more cranking time to get the mixture right before your battery croaks. We know that's ALL it does because a fuel injected car starts very quickly - it has the same engine but meters the correct amount of fuel and delivers it exactly to where it is needed at the exact time it is needed. The carburettored v12 by contrast needs to atomise the fuel, send it into the plenum, up and over the cam covers, along the runners and to the cylinders. It won't surprise you to know that with poor airflow and a host of cold metal srfaces between these two points, not much of the fuel atomises in the first place and of that that does, much simply condenses back out on the metal surfaces a long way from the insides of the cylinders. In the mean time, you are cranking away until enough of it gets into the cylinders for the three or four combustion events which tip the engine into "running".

Essentially, if you wait for the float bowls to fill up and have the right amount of choke for the temperature you are at, then the high torque motor's spare capacity for useful work is never required.

The high torque motor for the v12 runs at 160rpm and the standard Lucas item at 120rpm. My car is fuel injected and has a data logger on it. From that I can see what the engine speed is and that it often starts within 0.1seconds of turning the key, which corresponds to about the 4th cylinder to fire, i.e. within 2/3 of a single crank rotation and it has already taken off past 350rpm. This is with a standard Lucas starter.

I also know that perfect fuel atomisation has ocurred - I run LPG.

Even when starting on petrol it can be just as quick - the computer is set to dose it with what it takes to make it go.

Being able to see all of this on a graph on a computer screen means there is really much less " mystique" and "maybe" to all of this.

In short, if the gear reduction motor is the same price or cheaper than the repair to your current starter and that needs replacement or repair, then most certainly go for it. If not, then it's personal choice as to whether you feel the incremental cost is value for money or not.

kind regards
Marek

[Hugo]

Absolutely correct Hugo. You get tons more airflow if you open the throttle. The carburettor piston then has no choice but to move to where the air pressure difference between the top and bottom of its rubber diaphragm dictate it must and that is a function of manifold vacuum.
Marek

That wasn't quite what I meant - the piston does have a choice - it can stick! If it sticks closed, I was speculating that you would still get a bit of increased airflow purely by virtue of the butterfly being open. And Strombergs have diaphragms whereas SU's don't I believe. Although the first SU carburettors had a calf-skin bellows instead of a spun aluminium dashpot & piston - hand-stitched by old Mrs Skinner (of Lilly & Skinners shoes - SU standing for Skinner's Union).

[MarekH]

I was referring to the v12, as that was the subject of the original thread. This will have originally been fitted with a Lucas starter and Stromberg carburettors.

kind regards
Marek