Replacing A Motorcycle Battery With A Capacitor

[PRR]

> electronic ignition timing ...based on time before TDC rather than degrees.

Yes, the ignition delay is a "time", not an "angle", so that seems good.

But Centrifugal Advance gives an angle which increases with RPM. If linear, it would be "time".

Except for the lag between RPM rise and shifting the weights. Which is probably negligible on a loaded engine: load inertia makes rate of rise of RPM "slow". The 2-ton car picks up speed, the 2-gram weight lags a bit, but not much.

But the "time" needed is not constant. It is strongly affected by turbulence. At high RPM (approaching the valve airflow limit) the turbulence is fierce, fuel droplets violently broken apart and rubbed against air molecules, the flame spread speed increases, and the turbulence disperses globs of flame all over the chamber. In say the top octave of the engine's RPM range (for '66 Mustang, 2,200-4,400RPM, most of the working range), the delay time falls about as fast as RPM rises. A constant-angle timing is not perfect, but pretty darn close. A constant-time scheme is liable to shift the pressure peak ahead of TDC, which is bad.

And that is just to get pressure peak to happen soon after TDC. The real reason we have variable advance is Detonation. Hot-gas engines need high expansion ratio for good efficiency. In a cyclic system, the compression ratio is semi-symmetric. But when we squeeze a fuel-air mixture too hard, it go BOOM. There is a delay between squeeze and boom; at high speeds it won't go boom or the spark will spread first. At low speed, boom happens. Different fuels take different squeeze: straight gasoline (Zippo or Coleman fuel) about 4:1, Benzene 10:1, NatGas 20:1. We want "high compression", but not high fuel (or tank) cost.

For more fun: spark engines use variable effective compression to control power. Slinking along at 20MPH, you put 8:1 squeeze on a 70% vacuum, like 2.4:1 compression.

So the compromise used on sedans, light trucks, cycles, etc is: the market finds a fuel, currently gasoline good for about 6:7 or 7:1 compression. And then put a 8:1 or 9:1 squeeze on it. At slinking power, it won't detonate. At high RPM, it won't detonate. Torque and efficiency are good. The problem is that wide-open at low RPM, it pings (light detonation). We used to dump fuel in the jug, rich is hard to light. And retard the spark: the sum of compression pressure and combustion pressure is what makes the mix go BOOM, shifting the combustion peak well after the compression peak "fixes" this, though at lower efficiency and thrust. Dumping fuel is unfashionable, so my Honda pulls a big retard on the spark, gets gutless at low RPM. My same-size Willys was much stronger at 1,000RPM (worse everywhere else).

Again with the '66 'Stang: the centrifugal advance was 10deg below 1,000RPM for easy starting, rising to 20deg at 2,000RPM where pinging was unlikely. They could add springs and cams to bend more, but few cars did. (The '79 BlunderBird didn't, but should have: the lean carb and crude spark control made it marginally pingy right at freeway cruise.)

> I always felt like mechanical ignition timing was like a stopped clock (correct 2x a day)

Not that bad.

> require prediciting the future

Or causing it.

We had an outboard motor. The "Speed" lever was on the magneto, not the throttle. You set speed by putting the spark ahead, forcing the engine to catch up with the spark. A 3-step cam put the throttle in idle, cruise, or MAX position, basically for mixture bias. It mostly ran advance- versus load-limited not throttle-limited.

> I could get my two stroke running backwards.

Most 2-strokes will run backward just as well. The HUGE ones are sometimes made to do this. The slow boat from China, full of $69 BeeRinger mikes for Banjo Barn.... if it has to back into a parking spot, they stop the engine, flip something on the starter, and start it up again. This avoids having a 100,000HP reverse-gear or swivel-blade propeller.

> with a small micro would be trivial

The "maps" in modern ECUs are still crude but 10 times more refined than spring contraptions.

> back in the '70s when I was messing with this I'd be dealing with crude one shots and such.

Yeah, I played with that. I could come up with somewhat elegant electronic ideas. PLL wrapped around a variable duty-cycle multivibrator? The thing is, if it falls into a mode which is out of sync with the engine, the engine can be broken. I've had trouble with a sticky weight trying to blow my heads off, and it was just 20deg off from "right". An electronic system which goes off the track will explore every possible bad timing and find the worst case.

Had enough fun with the BlunderBird's "DuraSpark Electronic Ignition". It was just transistor ignition plus a CMOS delay one-shot for starting. It ALWAYS had to be cranked twice.

 

[JohnRoberts]

Yes, I grok ignition timing.. Had a dual point Mallory on my old 54 ford.. I hooked up the choke cable to the distributor so I could retard the timing enough to start it, then dial the advance back in to take advantage of the full race isky cam (Give me more power, Scotty). You can see the mechanical advance working with a timing light on the crankshaft. You could tweak the springs on the mechanical advance to change where the advance comes in, but electronic would be soooo much easier.

More recent fun was when I put a Vortech puffer on my '93 stang. Flame speed in the cylinder is also increased by charge density. A motor with a blower acts like different compression ratios bewtween lo/no boost at low RPM and when the pump is pumping. I was at risk of melting my pistons from detonation at high RPM when the boost was really coming on, before I put on a trick ignition that cranks in retard based on amount of boost pressure. I miss that car. Stuck it into a guardrail in the rain before I got it completely dialed in [RIP]... It rains here in MS.

One thing I liked about the trick ignition is it had plug in chips (probably a resistor value) to set the rev limiter... If I dropped it off for service I could set the rev limiter for 2,500 RPM

JR.

 

[SSLtech]

I remember that SAAB were playing with variable-compression-ratio motor design a few years ago. -The idea was that you could up the comrpession at lower revs before the puffer woke up, but back it off at higher revs, to become an effectively larger motor without the 'automatic' detonation penalty...

Not sure if it made it all the way to production, but I always thought it was promising. -Presently one of my cars is a low-compression-ratio turbo, and while there's a definate "whoah, Nelly!" factor abofe the boost threshold, off-the line pickup is definately something which wouldn't scare Grandma...

[edit] -Ah... Here's some info on the SAAB motor... -looks like it's using a twin-screw compressor instead of the (more usual for SAAB) turbo. -Thus it's demand-operated with less need for a direct-rev-relationship, I suppose.

Keith

 

[JohnRoberts]

Interesting engine.. my SAAB memories are of old 2 stroke cars pushing blue smoke.

I've always been fascinated with superchargers. I bought a a old compressor off a wrecked studabaker back in the '60s but never managed the rest of the job. I would have to come up with a box to pressurize the carburetor, high pressure fuel pump, and what ever... I didn't finally get around to really doing it until my second childhood. I think I've read about some modern engines mixing crank drive blowers for low RPM boost with exhaust driven turbo for high RPM assist.

Another thing I've pondered is electronic valve timing... While it's true you get most of the energy back from compressing the valve springs, there are surely friction losses, etc. Solenoids or some kind of linear motor might be interesting. Imagine if you could dial in not only valve timing but overlap, not just by RPM, but pedal position. I guess it's possible to get most of the way there with a 4-valve/4-cam engine to play with relative and absolute intake and exhaust cam timing mechanically for at least a RPM based timing/overlap tweak. But again, I'd love electronic control of fuel delivery (already have), ignition (already have) and valve timing (?). Get your 500 rpm smooth idle, and serious power through the entire range. Some car companies are finessing the whole thing by coming up with variable ratio transmissions so you can dial in the motor for a fixed optimal RPM and vary everything else, but that sounds like even less fun than driving a normal automatic transmission...

JR

 

[mikep]

[quote author="JohnRoberts"]
Another thing I've pondered is electronic valve timing...[/quote]

doesnt Honda do that? they call it VTEC

 

[SSLtech]

Not really. VTEC is two possible sets of timing lobes, and a switch between the two. IIRC, there's a ram that 'shifts' the cam along so that the cam followers meet one or other sets of lobes, hence one or other sets of valve timing.

-In my opinion, the "V" in VTEC is false advertising. it's not "Variable" at all. It's "Switchable".

Someone (BMW and others perhaps? -I'd have to search) does variable valve timing by altering the position of idlers on the timing belt/chain, which is much more variable. You can probably get an a mighty torque curve if you do that right! However, duration is still fixed, only open/shut points are movable by that approach.

John, I think that the problem with 'electronic' valve timing probably isn't choosing the timing, lift or duration... it's actually opening the valve. Yo're basically trying to bang in a nail. And you want the total mass of the moving parts to be low, or the springs will never shut it fast enough. Formula 1 engines use air instead of springs to reduce the mass and bounce... plus 'witholding' air pressure can reduce opening resistance (a little!) and help with shut-timing... but they're only expected to run for a few hours before they are expected to turn into grenades... not to mention the cost is frightful!

VW sells a 'twincharger' in Europe, which may be what you've heard of. -HIGHLY efficient, I gather. I think it's a 1.4L engine with an Eaton charger for boost-on-tap-at-idle, and a (presumably series) 'snailshell' turbine supercharger to help things along once the things are moving along. I was looking into that since I'm touring the VW dealers over here at the moment, fishing for a new GTI with that twin-clutch/torque-converterless DSG transmission... I did install an Eaton twin-screw charger on my present MkIV VW, and it's been fine for about 70,000 miles now, though an under-the-hood inspection last week did turn up some wear on the overboost relief valve linkage, so I'll have to replace that... about $100 including a replacement valve... not too pricy, I suppose.

The variable ratio CVT's ARE wierd to drive, if you're used to gear-rowing yourself. Even though the Audi multitronic (titanium chain instead of a rubber belt) IS significantly faster than both the conventional slushbox auto AND the manual, it actually FEELS slower, because of the lack of 'impules' at shift points (even in slushboxes), which tend to subconsciously reinforce the driver's appreciation of speed. I test drove the Audi when it came out (I test-drive everything LONG before I'm in the market... hate informing myself and making decisions in a hurry!) and it's definately not a driver's transmission... and I wondered about its durability... -VERY economical though.

Keith

 

[JohnRoberts]

My dislike for CVT is a perception over reality... When I was a kid, the ability to catch second gear, and power shift third (who could afford a 4-speed?) actually made a difference in street racing (who me?). Who cared that automatic transmissions were kicking ass at the drag strip?

Regarding a first order valve timing and overlap variation imagine two moving cam chain idlers so you could tweak the intake and exhaust valve-train relative to each other as well as relative to TDC.

I suspect electric valve operation would not be trivial to get robust. Rather than some linear up/down perhaps a variant on Desmodromic valve train (after Ducati) but with a stepper motor driving each cam. The stepper motor could tweak general offsets and even small ramp timing variance with some flywheel effect from cam inertia for general operation.... or not.

JR

 

[PRR]

> electronic valve timing... While it's true you get most of the energy back

Good springs and well-oiled bearings give back 98% energy. Good electrics are lucky to do 95%; 50% may be more like it in severe pulse duty. I think you need a bigger generator. Mechanical gizmos are reliable (if only because of 100+ years of trial and failure); the electric valves I've seen were not (even when just an electric stop on a mechanical valve, like Caddy's 4-6-8 engine).

Honda's VTEC is interesting. You get, as Keith says, two cams. One "lawnmower", one "race". In my 2002 Accord, the low speed cam is even more conservative than a lawnmower. No overlap at all. Torque is falling at just 3,500RPM, despite four good size valves. But at some point above that (influenced by throttle demand), it switches to the "race" cam, it roars like an Offy, and hauls to 5,500RPM (which is fairly fast for a small-bore long-stroke engine this size).

The cheapo Accord gets a partial VTEC. Mine only has a race cam on the exhaust. I'm not sure why they thought that was more important than the intake; probably to do with holding a long expansion ratio for full burning, good economy and low smog. It's pretty thrifty and sweet in routine low-RPM work. But the extra 10% kick in the top half-octave comes in handy merging up freeway on-ramps.

Honda has snazzier models with VTEC on both cams.

The contraption is simple. There's two valves, three rockers and lobes. The center lobe is "race". The center rocker normally idles. There is a pin which can link it to the two other rockers which work the valves off the two lawnmower lobes. Oil pressure pushes the pin when the ECU tells it to. The next time all three rockers align, the pin links the three rockers. Since the race profile is "bigger", it dominates valve motion.

Since one lobe works two valves, there is an assumption you won't run on the race profile all the time or it would wear out. This is so for all sane drivers. I hear the young guys with coffee-can tailpipes cruising 70MPH in 3rd gear "rrrrrrrrrrr!!!" and pity their center lobes, but WTF, they wanted new cams anyway.

> it's not "Variable" at all. It's "Switchable".

It's a variable with two states. In computers we call it a "bit". You gotta know that for your first Computer Science quiz.

We don't need fine control of timing. A single profile will give nearly flat torque over a 3:1 range of RPM. If you "need the very best" in economy or smog, that may be 2:1. Automatic transmission cars (98+% of the US market) just cycle 1,800 to 3,600RPM all day long. Their excursions to 5,000RPM are so few they don't count against smog or economy.

If you always want Maximum Power, then you want to stay at Maximum-Fat RPM, your Max HP point. Or given the limitations of switched-gears, within a 1.4:1 range near Max Power RPM. You fatten your cam for the sweet-spot between airflow and turbulence, and to heck with a nice idle.

Top Fuel Dragsters violate this theory. In drag racing, shift-times are killer. The big boys discovered they could give up shifting if they had More Power! I gather they run 2,000RPM-8,000+RPM. Below that they slip the clutch, at the top-end (300MPH) the tire diameter grows and acts like a taller gear. The cam and valves are "mild" for 6HP per cubic inch, because these monsters barely breath air. The "fuel" is a liquid low explosive, can explode in a full tank. Air is used to urge and agitate the fuel down to the cylinders, but the "air intake" manifold in action looks more like a toilet pipe: as much liquid as air. It is all very inefficient. But they only run for 4 seconds a few times a week. So who cares if the fuel costs $100/second? (The total cost per run is MUCH higher, because stretched and fatigued engine parts get replaced after every run. A weekend rebuild in 19 minutes.)

The maximum total range of a spark engine is hardly over 10:1. I can feather the Honda down to 600RPM and move, but it really doesn't like it (partly: the engine mounts are tuned in that zone and can shudder violently). Also a throttle plate can't give good control over a 10:1 range of air flow (drive-by-wire would change this). Working the very-low RPM range is a rare thing; if done a lot, it might be better to add a granny-low gear. Indeed I shudder 600RPM only to move along with 300 slushboxes in a traffic jam. If I'm not constrained by a bumper a foot ahead of me, I'd never be below 1,500RPM.

> Formula 1 engines ... they're only expected to run for a few hours before they are expected to turn into grenades...

They run whole seasons now. Many of them are rented. The team mechanics can't open them. They use a borescope to look for loose bits, and otherwise the ECU handles everything (probably including a sudden-death when the rental period expires).

> not to mention the cost is frightful!

That's true.

Blowers: two basic kinds.

Positive Displacement gives a fixed boost ratio. If overdriven 3:1, you have 3 Atmospheres intake pressure at any useful RPM. Torque curve is flat. The flame-spread thing leads to detonation at low speed or under-boost at high speeds.

Centrifugal gives rising boost with RPM. This neatly misses the low-RPM detonation problem. You may get nearly no boost and nearly no drag below 3,000RPM. But the rising boost can end up over-boosted at top RPM.

This is worse with turbo-superchargers, which want to raise boost faster than engine RPM, and usually need a limiter (dump valve).

 

[SSLtech]

I must confess, I haven't kept up with the creeping regulations in F1...

Last time I was at the track it was 3.5 litre V-10s and V8's. Last time I heard they were running 2 races per engine (revolutionary!) and a 10-grid-slot penalty for an engine swap... A season on a block seemed unthinkable...

Even 'CrassCar' ran 'qualifying grenades' last time I was interested enough to check... O course 'Bubba' will often take an old transmission which is right at its sell-by date, then drain the oil out for a friction-reduced last-lap o' glory... -but that's way over the line where racing improves the breed, and into the land where racing just blows stuff up in the name of going faster. :twisted:

I'm all for a revision of Sleeve Valves. When I was ten years old I got the Bosch Book of the Motor Car, and it had a diagram of the 'Silent Knight' engine in there. Of course, now I know how tough it must have been to seal those things, but it could be varied at least as easily asa camshaft bangin' in the nails, I shouldn't wonder!

I know I cant be the only one who derives this much edification from reading PRR's math-connected explanations. :thumb:

Keith

 

[Gus]

I have been looking on the web for a site I was at some time ago, it had a BMW335 engine write up. I have not found it yet

IIRC
Cool engine
twin turbos,
direct injection
no thottle plate
a few things going on with the valves
inline 6
lots of power

 

[SSLtech]

Webmaster at work just got one. (NEW 335. Ordered from Germany, delivered 3 days ago.)

VERY nice. Almost completely lag-less. Feels like a big motor, but able to sip the juice... well... relatively speaking. I think I can wrestle the keys out of him next week for a lunch... -Will report back if I do. -Of course I might have to swap him the keys to the 951 (Turbo 944) if I do, but we'll have to see how that negotiation runs...

Keith

 

[PRR]

> I haven't kept up with the creeping regulations in F1... ... A season on a block seemed unthinkable...

I admit I have not really cared about racing since the mid-1960s. When Bill France looked at the Ford SOHC and said "NO!", he called a stop to "improving the breed". Now, he was correct that the SOHC was hardly a "stock engine"; in that it has little advantages and many problems as a street engine. But he allowed the Hemi to return after Chrysler had proved it was pointless in street use. He let the Chevy Porcupine run, and while GM happened to quit that year, the porcupine became a great street engine, emulated by others, "improved the breed". Yet the current NASCAR engines are all pre-1966 thinking.

I may be getting confused with the US circus... "iRock"? (Why hasn't iMac iPod Mac sued them yet?)

I think that all formulas based on engine size with well-funded teams eventually "improve" to dangerous speeds. When you talk about reducing engine size, they whine about having to start all over again.

NASCAR did manage to downshift from 427 to 355. Partly because sedans stopped getting big-blocks. Partly because a big small-block can hang with the big blocks pretty well.

Even so, NASCAR runs restrictor plates. I gather the open-wheel formulas now often limit boost pressure. They are trying to make the least-possible changes to keep the cars on the track and all moving at similar speeds, making nostalgic noises.

And if you keep engine size constant, continually improve engine details, and then get Limited by your race organization.... then engine stress drops from 99.9% of breakage to 95% of breakage, and engine life might rise by a factor of 10.

An additional issue is Infant Mortality. A small screw-up in assembly may cause early failure. Dropped nuts and stray flakes happen. If the machine runs an hour or three it probably has no unknown defects. There's also some wear on the parts which are not normally replaced in a rebuild. So if you reduce the number of times you re-assemble the engine, reliability will be better. And random DNF has lost a LOT of races.

> 'qualifying grenades'

NASCAR and Indy have Traditions which must be upheld.

But how often do the Lows, HugeDepot, Corgy-Chaw and other Big Brand Teams fail to "qualify"? If NASCAR put them 34th in a 33 car field, that's millions of dollars into the business which could just walk out permanently. Putting a few megabucks in a team does not buy you a slot, but NASCAR listens to money. Most of the entrants expect to get on the grid; anybody who has no hope soon stops trying. The size of the community which can field competitive racers is just right for the number of slots on the grid. There may be some shuffling for the last slot, when major drivers or teams have a real bad week and don't field a full team. But another major team will pull out a backup car and junior driver. Or a couple of teams, so they can "compete" to "qualify" for the slot. If they get in, great; if not, well they have better cars already in the field.

I dunno exactly how it works. But like pro wrestling, it is well managed. The number of players who can and will appear is about right for the event. The specific winner may be in doubt, but everybody knows that if Hulk Hogan or Plymouth wins EVERY week, the audience will lose interest and attendance will drop. So they try to level the field and thereby randomize the winners. Losing isn't bad, it makes you the underdog in next week's rematch and upset victory. In restrictor-plate racing, random luck and DNFs give most entries a chance. In the WWF, luck may be a coin-toss in the locker room, which guy feels like working harder tonight, or Vince's sense of what the crowd want to see.

> into the land where racing just blows stuff up in the name of going faster.

I like it, but it seems to work only in the field of $400 claimer races.

 

[SSLtech]

Claimer races... I used to run a car in a UK national one-make series where you could 'claim' sealed engines. Nobody got caught cheating in that one... well, not in the engines anyhow... but oversize sway-a-ways and illegal gear ratios are easily caught without tear-downs.

I rediscovered (as we all did) the only surefire way to make a small fortune from racing:

Start with a large fortune.

Keith

 

[beatpoet]

Wow, many of you have years of knowledge accumulated on engines, whereas the first engine I rebuilt was just last year.

Very enlightenening stuff though. I have gotten most of the basics of operation and assembly and this thread has run away with far more topics to chase than replacing the battery, although I haven't given up on that idea.

I am thinking hard about pre-ignition now, and am fascinated by the concept of changing the cylinder displacement based on RPM! This brings to mind some kind of trumpet or trombone-like servo/valve system that fine tunes the cylinder displacement based on rpm vs. applied torque perhaps.

I don't see a lot of info on rotary valves on the web, I would think they could be made to become even more efficient than a spring attached to a 'nail.'

 

[JohnRoberts]

As PRR noted, IC engines are a mature technology so there have been many generations to work out the kinks and optimize. There have been many variants along the way with some merit that either never reached critical mass, or had some tragic flaw.

I am enthusiastic about the marriage of nonlinear digital techniques to tweak more performance out of these mature platforms.

JR

PS: Yes rotary valves finesse the back and forth travel of conventional valve trains but IIRC introduced other issues. I really liked the simplicity of some 2-stroke motors but lubrication issues were not tailpipe friendly (visible oil smoke).

 

[Gus]

Do vettes still use a pushrod engine?

 

[SSLtech]

Ahhhhh... found a pic from the old one-make/sealed-engine race series that I ran a car in... It used to hurt a LOT to look at this picture.

Brands Hatch, 1994: Mine is the blue one. The red car had spun directly in front, and is facing the wrong way...

The SAAB system could be made RPM-driven, of course now we have computers, we can use many sensors to optimise things...

Keith

 

[PRR]

> a revision of Sleeve Valves.

Darn your loose mouth! You cost me $23.

Sealing may be an issue, and the death of the sleeve seems to be improved poppets with less leakage.

But any time I look at a sleeve engine, I wonder how you cool the piston. Most heat flows out the sides to the cylinder walls. This is not a great thermal connection, and control of piston heat is an issue. With a sleeve, you have TWO such poor thermal connections in series. Against this, the sleeve motion does "spread" heat over a larger length of water jacket; still seems to me that a high specific output sleeve engine must cook pistons.

But on the other hand... I just discovered the Rolls-Royce Crecy. It brewed through WWII. Ricardo had predicted that poppet valves would reach their limits, and that higher power/displacement (roughly: higher power/weight) would need something else, and he urged sleeve valves. Bristol made a series of sleeve Radials, which my USA WWII aero-engine books hardly touch, but turn out to have been potentially marvelous engines (initially handicapped by careless management and hasty production). R-R pondered these thoughts in Vee form, and added Direct Injection so it could be run as a 2-Stroke (or a Diesel, but despite Packard's small success with an aero-Diesel, spark engines dominated). The flaws of 2-stroke are less when you commit to a blower anyway (aircraft generally want a blower) and wait until valves are closed to add fuel (may also marginally delay detonation). Aircraft speeds were already high enough that rear-directed exhaust added significant thrust (this is true of the big Radials too, above 400MPH); exhaust losses are not losses. The stresses of war focused work on the tried-and-true pre-war poppet Vee engines, and only a few test-stand Crecy sleeve-mills were built. Post-war demand was low and growth was in those silly jet-engine things; R-R did well in that market. New pistonenginess vanished from the air. But someone dug in the archives and wrote a book: The Rolls-Royce Crecy (Historical) by Nahum, A.; Forester-Pegg, R.W.; Birch, D. And I had to get a copy.

> the only surefire way to make a small fortune from racing: Start with a large fortune.

Arguably STP and Bud got more out than they put in. The leverage of offering cash for any top finisher with a snake oil decal was fantastic: pretty fair fortune from nearly nothing. Bud/Busch invest more but probably earn it all back: large fortune into larger fortune.

As for the racers: sure, money down the hole. But they do what they love.

> Do vettes still use a pushrod engine?

Of course. Overhead cam is a scam.

OK, everything equal the smaller monkey-motion in an OHC can move 10%-20% faster/further, the engine give 5%-15% more power.

Funny thing is, OHC tends to be larger. Some race and tax classifications go on displacement. But in most street cars, displacement is unlimited, engine bay space is limited.

And if you use the high-RPM potential of OHC all the time, the engine wears out sooner.

So a larger engine with rockers can fit in the same bay, and keep up with, a smaller OHC, and maybe live longer.

As an extreme: the Flathead is not a bad engine. The valveworks tuck to the side, long strokes never hit the hood. Breathing and heat-loss are issues but not fatal. The main problem seems to be detonation in a chamber much larger than the piston.

The comparison between the recent Ford Modular V-8 and the rocker Corvette is probably unfair. Ford has never made a good engine except by accident. But the Ford Mod is HUGE and heavy for the power it gives.

Corvettes were running well at Le Mans against exotic OHC machines, last I noticed. No doubt about the old-school technology: the Vettes boomed along like runaway trucks, instead of like ripping zippers. Not winning, but most of the exotics didn't win either of course. Gone are the days when a US company could buy a Le Mans victory.

There's life left in rockers.

But particularly for V-engines. Share one cam-stick across two heads, and hardly be in the way. Since the arrival of rubber belts, 1-bank engines (all our Fours) can be built cheaper as OHC. Add a belt and lose all the pushrods. Are there any non-Vee rocker-arm engines left?

Also for 4-valve (per cylinder) engines. The pushrods do get in the way (a fact Ford repeatedly missed even in 2-valve heads) and with two intake ports and pushrods in the same place, it just gets too tight to do much good. 4-valves are traditionally "grenade" engines, all top-end and no grunt, but it appears that a tamer 4-valve has a bit more turbulence (smoother better burning) at low RPM while still breathing well at high RPM, and lower valvework wear.

There's a lot of "don't change what works". GM has 100 years experience in pushrod engines, 50 years in "the modern OHV sedan engine". The Chevy OHV V-8 comes from thoughts which struck while implementing the Olds, Caddy, and Buick OHV engines. There is a lot to be said for decades of refinement instead of radical change. Heck, look at the 1963 "Ford" DOHC Indy engine (not a Ford design). It was better than the Offy because it had more cylinders. It took a couple years to catch up with Offy power; the Offy mechanics knew their mill. The Offy kept winning because it was a hair less thirsty and most samples were more reliable: they knew what broke and had fixes. Took a decade for New Improved to drive Old Obsolete off the track.

 

[electrog]

just a quick side note for accuracy: current F1 engine regs mandate 2.4 litre v8's which must last for the Saturday & Sunday of two consecutive race weekends (Friday practice is now exempt, in order to promote more cars on track & less non race weekend in-season testing). As mentioned, a 10 grid position penalty is imposed if an engine must be changed prior to completing 2 weekends.

The upcoming regulations for 2008 & beyond will likely include even longer required duty cycles...

david

 

[sonicmook56]

So, did you ever replace the battery with a cap?

If so, can you draw a diagram?

I think I could just get away with a 12v regulator and a cap maybe?

I want to use a cap on my motorcycle. It's a kick start diesel that needs no power at all. The magneto/cap will just run the headlight and brake/turn signals.