.....If the fuel lets you run more timing advance and or compression you will get more effort out of it.
More timing advance also means that more of the gas that is burning is also trying to prevent the piston from rising to top dead center, as the burning fuel is pushing down on it.
Yes, it raises the effective compression ratio, but it does not help as much as one would think by that parameter alone.
Theoretically, having less spark advance is better.
Obviously, the best approach is to have direct cylinder injection, as it gets around all the normal compromises of cylinder pressure, spark advance, etc.
Timing, and cam profile is a major factor when considering either economy or performance.
Excessive timing will create knock as the engine is trying to turn it'self backwards. The knock sensor in the Insight does what it is supposed to do.
The secret to how the Insight gets away with a lot of negative or positive timing is the "crank offset".
When the piston is at TDC, the crank mass and rod mass is already 12 degrees ATDC.
(My opinion)
Willie
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01 MT "Little Red Rocket"
The first "TURBOCHARGED" Hybrid, Insight G1- (01/2003)
MaxIMA Battery (Serial #2), on 8/25/12 @ 301,520 miles
Use: 320,000 mi. @ 57.8 LMPG
Washington D.C. is in complete gridlock most of the time. Folks are busily fighting idealogic battles while nothing really gets done.
Unfortunately D.C. has done a lot these last ten years..... and not good either. Installed a new agency called TSA (and VIPR teams) to prod & strip & irradiate us at airports, bus depots, train stations, along Tennessee interstate highways, within 100 miles of the border (checkpoint charlies), and yes even public parks, post offices, and malls.
Passed the anti-freedom Patriot Act. Raised our taxes, given huge chunks of our money to corporations, installed new rules to force us to buy hospital insurance (or be fined), waged wars on 5 different countries, arrested people for their Prochoice option to smoke marijuana, passed guns across the borders to Mexican druglords, and on and on.
I'd be genuinely happy if D.C. stop abusing us & do nothing for awhile.
__________________
OWN: 61mpg Insight (greenercars.org score: 57)
both blue and silver,
and a 45mpg BeetleTDI (score: 47).
More timing advance also means that more of the gas that is burning is also trying to prevent the piston from rising to top dead center, as the burning fuel is pushing down on it.
Yes, it raises the effective compression ratio, but it does not help as much as one would think by that parameter alone.
Theoretically, having less spark advance is better.
Jim.
Exactly. Advanced timing actually causes the engine to work against itself; piston still going up on compression stroke AFTER the fuel has been ignited and is pushing against the piston. Less timing would indeed be best. However, you would have to find a way to make the gas burn faster. Hydrogen would do this and I think that is what most of the people pushing their H2 systems are saying. The problem with those systems is that they don't address the fact that the car's ECU won't allow the full effects of H2's faster burn rate to be realized not to mention that they don't take into account the added load on the electrical system that makes the engine work harder.
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Silver '00 MT
90.2 LMPG
80+ psi in RE92's for the past 2 years without incident
Calpod switch
Warm air mod
Grill block
EPS fuse removed
FAS/fuel injector interrupt circuit
grid charger
OBDII C&C gauge
Washington D.C. is in complete gridlock most of the time. Folks are busily fighting idealogic battles while nothing really gets done. In the mean time, we borrow and spend and become Greece - a little bit more each day. Why would any intelligent person want to go there and subject themselves to that useless abuse
We sent the current set of politicians there - we deserve them!
A friend of mine says, "Just be happy we don't get ALL the government we pay for."
I read somewhere, "We have the best government money can buy."
Quote:
Originally Posted by Subdewd2
a 54 cent tariff on brazilian ethanol expired with the subsidy for domestic produced juice last january, supposedly. I would think there would be an increase in the use of imported ethanol. that said e85 here in Missouri is running $3.89/gal reg @ $2.99!
In affect they charge you 90 cents more a gallon to get ~34% less gas mileage.
Exactly. Advanced timing actually causes the engine to work against itself; piston still going up on compression stroke AFTER the fuel has been ignited and is pushing against the piston.
When the plug fires, the fuel is just starting to ignite and a flame front is created and spreads. The flame front and pressure build up isn't instantaneous in a well designed engine unless you then get pre ignition which the knock sensor would control by retarding the next spark slightly.
Less timing would indeed be best.
Less than what? If the knock sensor does it's job it allows [almost] the max amount of spark advance without pre ignition so the BMEP can be higher than with a less advanced timing. Max BMEP should occur after TDC.
The Insight crank is basically offset to allow the piston/con rod to push straight down at maximum BMEP (& to also offset side forces & increased friction of the piston against the cylinder if the rod was at an angle at that time). A very clever application rather than offsetting the wrist pin as done in the past.
My first car was a Model T which had a spark timing and gas throttle on the steering column. The car always ran faster (all of 48 mph) with the spark lever well advanced. Even when running Kerosene. With all of 4.5:1 compression it would pretty much run on anything that would ignite.
However, you would have to find a way to make the gas burn faster.
Hydrogen would do this and I think that is what most of the people pushing their H2 systems are saying.
If it's the water bottle H2 systems then it's probably baloney. They are injecting an uncontrolled [and insufficient] amount of H2 into the engine. H2 has quite a bit less energy than old fashioned gas. Just check the F/A ratio that H2 requires vs gas and do the calculations on a cost per mile basis.
The problem with those systems is that they don't address the fact that the car's ECU won't allow the full effects of H2's faster burn rate to be realized not to mention that they don't take into account the added load on the electrical system that makes the engine work harder.
Exactly!
I did the calculations years ago and to run my car down the road on pure water derived H2 and air would take more power (amperage @ 12v) to separate the water fast enough to run the engine than my engine can produce. Actually several times MORE hp than my engine.
To do the calculations I called a local welding gas supplier to get the energy content per unit of H2. The guy I talked to said he hated to work with compressed H2 because if you get the slightest leak in the connections the friction of the escaping H2 causes enough heat that it bursts into flames when it hits air!
That ought to be fast enough ignition. Just start to open the injector and BOOM!
Passed the anti-freedom Patriot Act. Raised our taxes, given huge chunks of our money to corporations, installed new rules to force us to buy hospital insurance (or be fined), waged wars on 5 different countries, arrested people for their Prochoice option to smoke marijuana, passed guns across the borders to Mexican druglords, and on and on.
Is Godwin's Law being borne out here? LoLz.
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Possibly to allay/or perhaps add some confusion as to fuel choices, it's not always about the timing of the 'boom' all on it's own as to what's specified for fuel:
fwiw: One reason other than the sparked combustion process to use premium fuel for a Chevy Volt and possibly other newer serial hybrids more biased toward electricity use, may well be that these plug-in vehicles can conceivably go for a very long time indeed without requiring any fresh gas tank fillings be added .i.e. when running on pure electric plug in power mode exclusively for relatively short trips. If you check the chev volt vid youtube link above you will see the fellow gets 218Lmpg and not much call for gas.
The extra additives in premium aid's long term storage, hence Volt's choice of same and tailoring of engines operating parameters.
Well, at the shop I worked at in the 90s we got a lot of old vehicles. Many had a v8 and a distributor with points, sometimes dual points and such setups. Some of the older bugs used a magnetio just to name a few.
Anyway, we did stuff that other shops didnt like reset the timing, make sure plugs were gapped, checked the dwell, wires and coil output. It must be the rotating of the distributor that made it retard the timing over the years as they were all out of time and we would reset them. We set them like the afr of the carburators using the vacuum reading.
Man, it made the car behave like a new vehicle with the proper set ignition. Then on performance cars like mustangs and such we went for a test drive and set it high as it could go before it pinged.
Looking at the SG2 I was just shocked as it was always retarded on the i2.
id be curious to know if early ecm versions for the gen1 have different values for the advance (among other parameters) vs latter years.--I may take a ride this weekend and test just how much advance i can get. i have a original ecm (2000) with no updates, so it would be interesting to see how some of the newer versions compare
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