REMLR 243
2007 Range Rover Sport TDV6
1977 FC 101
1976 Jaguar XJ12C
1973 Haflinger AP700
1971 Jaguar V12 E-Type Series 3 Roadster
1957 Series 1 88"
1957 Series 1 88" Station Wagon
No, it doesn't. It becomes blow, bang, squeeze and suck. Anyone will tell you this doesn't achieve the required result.
You mention a broken valve spring. Could it have dropped a valve? Seems far more likely than the running backwards scenario.
Otto cycle engines. which make up the vast majority of four stroke petrols, shouldn't be able to run backwards, as the "suck" stroke in your analogy becomes blow, which would give a blowback through the carb, rather than through the exhaust as normal. Running backwards happened on old engines on shut down due to carbon build up and also due to badly timed engines, but this was due to a hotspot in the combustion chamber and never lasted more than a second or two on petrol engines, as the fuel/air mixture was quickly exhausted. Seriously, how does a combustible fuel/air mixture come through a carburettor backwards? It flies in the face of all carburettor science.
I'm with Dave ( Blknight ) on this. It should be impossible. Of course, a DC starter would turn the engine backwards if the polarity was reversed, but what would that mean? Everything that clears going forward will also clear going backwards. It's simple engineering, and doesn't change with direction.
People often describe situations inaccurately. Ask any cop about eye witness reports. I don't mean to insult you or your contact, but it is true.
Without further evidence I'm going for a dropped valve.
JayTee
Nullus Anxietus
Getting involved in discussions is the best way to learn.
2000 D2 TD5 Auto: Tins
1994 D1 300TDi Manual: Dave
1980 SIII Petrol Tray: Doris
OKApotamus #74
Nanocom, D2 TD5 only.
a combuastion chamber injected diesel or a 2 stroke will happily run in either direction..
as there are very few 2 stroke petrols with valves I'm assuming its a 4 stroke.
anyway...
for a four stroke, normal operation starting at TDC with both valves on the rock.... (end of exhaust stroke)
1. the exhaust valve finishes closing and the intake valve opens, the piston moves down and draws in a fresh air/fuel mix. thats intake (suck)
2. the inlet valve closes, the piston swings past BDC and begins to compress the fuel air mix on the way up. Thats compression (squeeze)
3. approaching TDC the ignition system (points, mag, reluctor, coil pack) lights off the fuel air mix and as the piston over centers the burning mix raises the pressure and shoves the piston down, near the bottom the exhaust valve begins to open. thats power (bang)
4. as the exhaust valve opens the piston moves up the cylinder forcing the exhuast gasses out the exhaust and near TDC the exhaust valve begins to close and the inlet valve begins to open. Thats exhaust (blow)
Lets do that backwards...
1. the exhaust valve opens and draws in an air mix (no carby so no fuel, and while it would be nice we havent worked out how to appease the hippies by unburning things) near BDC the exhaust valve closes and the piston continues up into the power stroke.
2. the air is compressed and after TDC a spark turns up (wont work with some reluctor or electronic ignition systems)
3. the air expands and helps move the piston down the cylinder (but entropy means you dont get as much effort out as it took to squeeze the air in the first place)
4. near BDC the inlet valve opens and as the piston rises forces air out the inlet valve through the carby (which if its a very simple carby means you now have a flammable mix in the air intake and air filter)
now...
on a diesel.....
some (especially centrifuge blown and oiled 2 strokes) can run backwards (if you know someone with a unimog 1700 or 1750 that you dont like too much ask them to lend me their mog for a demo...) because a diesel only compresses air and then the fuel turns up. If the engine is warmed up enough and you can fling it fast enough the combustion chamber will be hot enough to light off the fuel even though its turning up late for the party.
IF you really work it hard you can set fire to the air filter...... (go on ask....)
Dave
"In a Landrover the other vehicle is your crumple zone."
For spelling call Rogets, for mechanicing call me.
Fozzy, 2.25D SIII Ex DCA Ute
TdiautoManual d1 (gave it to the Mupion)
Archaeoptersix 1990 6x6 dual cab(This things staying)
If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
If you think you're in front on the deal, pay it forwards.
The only 4-stroke I've seen run backwards was a N/A diesel dumper truck in the UK years ago, 3 reverse and 1 forward gear !
If he'd 'flooded' it to get it started it might run backwards very briefly, I tend to think it was the spring failing that caused the problem.
Colin
'56 Series 1 with homemade welder
'65 Series IIa Dormobile
'70 SIIa GS
'76 SIII 88" (Isuzu C240)
'81 SIII FFR
'95 Defender Tanami
'58 Series II (sold)
Motorcycles :-
Vincent Rapide, Panther M100, Norton BIG4, Electra & Navigator, Matchless G80C
A couple of points - some two cylinder engines have a single coil, no distributor, with a spark every turn of the crankshaft in both cylinders. If Haflinger has this, could this allow the engine to run backwards?
In the distant past, a relative had a boat with a single cylinder two stroke petrol engine - reverse was engaged by throttling back to an idle and rotating the magneto 90 degrees (lever provided for the purpose), whereupon the engine would run in the opposite direction. The engine was, from memory, a "Blaxland Pup".
John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
JayTee
Nullus Anxietus
Getting involved in discussions is the best way to learn.
2000 D2 TD5 Auto: Tins
1994 D1 300TDi Manual: Dave
1980 SIII Petrol Tray: Doris
OKApotamus #74
Nanocom, D2 TD5 only.
I have no knowledge of that particular engine, but two stroke, no cam no valve engines can run backwards. It's not so easy with 4 stroke, camshaft engines. Everything is against it, as Dave points out. It still requires a fuel/air mixture to be drawn through the carburettor. Doing it in reverse simply won't work.
JayTee
Nullus Anxietus
Getting involved in discussions is the best way to learn.
2000 D2 TD5 Auto: Tins
1994 D1 300TDi Manual: Dave
1980 SIII Petrol Tray: Doris
OKApotamus #74
Nanocom, D2 TD5 only.
Thanks for that Dave - you articulated what I was trying to conceptualise.
The guy is still claiming that the engine ran backwards but clearly not possible - seems a strange coincidence though that it drops a valve, most likely caused by the broken valve spring just as the starter is trying to turn the engine the wrong way but I guess these things happen.
Has solved my curiosity on this but I am not game to go back to the guy as he is already dirty on me for suggesting the damage was caused by a broken valve spring or sticky/dropped valve.
Cheers and thanks
Garry
REMLR 243
2007 Range Rover Sport TDV6
1977 FC 101
1976 Jaguar XJ12C
1973 Haflinger AP700
1971 Jaguar V12 E-Type Series 3 Roadster
1957 Series 1 88"
1957 Series 1 88" Station Wagon
No John it is just a standard layout with dizzy, points and a coil - same as any old series LR.
However I can run my engine without a dizzy cap or rotor.
Here is my engine running
YouTube
Garry
REMLR 243
2007 Range Rover Sport TDV6
1977 FC 101
1976 Jaguar XJ12C
1973 Haflinger AP700
1971 Jaguar V12 E-Type Series 3 Roadster
1957 Series 1 88"
1957 Series 1 88" Station Wagon
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