Green Sally

[MKE40]

I think the effect would be marginal at best. The oil film begins to break up at 25 m/s, and there is not a lot that can be done about it. Below that speed, wear is negligible, provided the air and oil is clean. And a lighter rod would only have minor influence on the side force on the piston, that force stems mostly from the fact that the rod is at an angle to the direction in which the gas press down on the piston. When increasing the stroke, the rod usually becomes shorter, the angle greater, and the side force larger.

Lightweight components should be used to reduce the power used to make them go up and down, although some might also class that effect as minor. Lighter components do reduce the stress, thus the engine can attain a higher speed without breaking up instantly, while incurring wear. All very useful in racing, where the next rebuild is never far away. And titanium has the added bonus of being immune to fatigue.

Sustaining high speeds is another matter (sustaining here taken to mean clocking up many hours of high speed use, not necessarily all in one go). High piston speeds bring wear. There are medicines with which to postpone certain death (such as nicasil), but as far as I know there is nothing to bring immunity. A stock 4 pot Esprit is capable of reaching 30 m/s, but since the majority of driving is done on the road with much lower revs, wear seems to occur at an acceptable rate.

Increase the piston speed, and wear builds much quicker. Use the range above 6200 rpm often, and wear builds much quicker.

Can you increase the maximum piston speed? Can you increase the usage of the high speed regime? That depends on how long you want the engine to last.

What kind of boats do you make?

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DONT ASK.................

Classified !!!

Mike B) B) B)

[lotusmotors]

Are you sure an Esprit engine will reach 30m/s; on the road?

You'll have to allow me a bit of slack here as I'm a feet and inches man; but the Esprit has a 3" stroke; it's red line is 7400 rpm so:

7400 rpm x 3" x 0.166 = 3685 ft / min, or 61.42 ft per second, which is I think 18.7 m/s.

To get to 30m/s wouldn't you need to rev it past 11,500 rpm? Which I am not sure anyone has acheived with an Esprit. I've had one hitting 10,250 for short runs; but that is a long way from stock and is running around 26 m/s.

[hovgaard]

I think you are talking mean piston speed, I'm talking max piston speed.

25 m/s max speed corresponds to 15 m/s mean speed at the same RPM number.

[scoule]

I've had one hitting 10,250 for short runs;

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Wow! Which bit broke at 10250? :-)

[lotusmotors]

Wow! Which bit broke at 10250? :-)

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Well nothing broke actually - it's been running 10,250 rpm regularly for about two years; with 3.8 bar boost it hits 0-170 mph in just over 8 seconds. Not bad for a Talbot Sunbeam; but to be fair; it's had a bit of work done...

Richard Jenvey's group 5 Esprit circuit racer ran to 10,000 rpm in the late 70's; but I would be the first to acknoweldge these cars are the exception rather than the rule.

[Bibs]

Well nothing broke actually - it's been running 10,250 rpm regularly for about two years; with 3.8 bar boost it hits 0-170 mph in just over 8 seconds.  Not bad for a Talbot Sunbeam; but to be fair; it's had a bit of work done...

I'm arranging for your canonization asap...

[hovgaard]

Wow! Tell us more.

[B33 ENN]

-----------------------------------

Explain please,.............

Titanium equals  lighter /stronger, therefore centrifugal force  of the "smaller " end of the rod is reduced and thereby reducing the load on the cyl. wall.

Cannot therefore, the pistons accept more revs/piston speed by virtue of  oil film strength which must be where most breakdown starts ?

...

Mike

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My impression of lightening the internals of the engine is really to help reduce the energy used to drive the engine itself. This is then available to be used to turn the drivetrain-wheels instead. Then what's left goes to the road as normal.

I would expect that this reduction in internal mass will increase the acceleration of the overall package. The reduction should also, as observed, reduce stress on the components involved.

In an NA motor, I would speculate that this will show up best in performance, making a more lively and responsive engine for the driver. I would presume this should output more torque as a result.

A lighter flywheel would be consistent with this direction too. Adding lighter wheels to the car makes sense too and is easy to follow with.

That is the direction I will be taking with this project.

[MKE40]

LEAD US , Heavenly Father ............

lead US,.......................... the Unworthy followers of The Truth in black and white ( with a dash of yellow) !

Faithful Bumble Bee,

[lotusmotors]

Wow! Tell us more.

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The main challenge with this engine was keeping the head gasket in place; over about 380 hp they get a bit marginal. From the outset the plan was to at least double that figure. The liners were substituted for dutile iron; the head is dowelled to the block and head studs were custom items from the USA. The head gasket was replaced with an annealed copper gasket and a stainless steel wire ring is inserted into the top of the liner. The top deck of the block is machined and the liners are fully supported around the edge with a deck closing plate.

While the tuning is quite extensive it is fairly standard stuff; bigger valves, gas flowing, bigger chargecooler, bigger throttle bodies, twin injectors per cylinder and a BIG turbo. The core components though are stock Lotus: Bearings, block, head, even the SE / S4 pistons are standard.

The original turbo (a T5) was replaced with a larger turbonetics unit that is, as you might guess, as responsive as a supertanker. At launch the engine gets a 250hp hit of nitrous to wake up the turbo; which as I said earlier gives 3.8 bar of boost when up to speed. The car has been known to hit 60 in just over 1 second and go on to 170 in about 8.2 seconds. I can't say for sure; but I imagine it is probably the fastest Talbot Sunbeam in the world... :-)

[scoule]

I can't say for sure; but I imagine it is probably the fastest Talbot Sunbeam in the world...  :-)

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Got any pics?

[hovgaard]

Coooool.

Impressive. B)

May one inquire what compression ratio you have? Or do you just fill her up with toluene?

You say that you have been using it for a couple of years, but not knowing how often you floor it, that info is sort of incomplete... The million dollar question here is, what kind of load cycle does it see, and how long does it last (say, in terms of hours at full bore, or whatever)?

How do you like the NOs/turbo combination? Would you say that it is drivable on the road?

And how wide are your rear tyres?

[lotusmotors]

I have some pictues; not sure how you post them though.

The compression is 7.8 to 1; the fuel 105 octane racing unleaded. I am sure you must realise it is a drag car; so it doesn't see any road driving; most people would find re-packing the parachute a bit too much trouble after each prod on the brakes...:-) with two 650cc injectors per cylinder the MOT emissions test might be a bit tricky too...

It only sees WOT for about 8 seconds at a time...

The tyres; I am sure you can imagine are a little wider than standard. It has been very durable; on one occasion the driver forgot to turn on the electric water pump before his run; it returned to the pits with the header tank looking like a geyser and coolant at 145 degrees C. It did not break the head gasket.