Compression VS Pump Gas
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coolj30
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Compression VS Pump Gas
I am starting my plans for building a motor and I am trying to figure out what compression ratio I want to go with. I need a compression ratio that I can run 89 octane gas or 87 would be nice but I figure anything larger then stock would probably need 89. I would like to have 8.5:1 but is that too large to run 89 octane gas? If it is then can I run 8.0:1 with 89?
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MASSIVE TYPE IV
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James2
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Too many varibles. I think that was one of Bergs faults was he tried to set across the board CR ratios.
Items that affect CR and octane need-
1. wieght and gearing of the car.
2. Carb size/ exhaust.
3. Valve size/ head flow
4. deck hieght
5. cam timing
6. Ignition timing
7. cooling system
Second, running cheap gas is a false economy.
If regular is 1.80 a gallon and premium is 2.00 a gallon then look at this.
If you set you car up with low CR and retarded timing to run on the "cheap stuff" you might get 25 miles per gallon, for a cost of 7.2 cents a mile.
With higher CR and more timing, not only will you have more power, but if you get just three more miles to the gallon, 28 mphit will cost just 7.1 cents per mile.
So set you motor up fro the good stuff, it will actually be cheaper!
Items that affect CR and octane need-
1. wieght and gearing of the car.
2. Carb size/ exhaust.
3. Valve size/ head flow
4. deck hieght
5. cam timing
6. Ignition timing
7. cooling system
Second, running cheap gas is a false economy.
If regular is 1.80 a gallon and premium is 2.00 a gallon then look at this.
If you set you car up with low CR and retarded timing to run on the "cheap stuff" you might get 25 miles per gallon, for a cost of 7.2 cents a mile.
With higher CR and more timing, not only will you have more power, but if you get just three more miles to the gallon, 28 mphit will cost just 7.1 cents per mile.
So set you motor up fro the good stuff, it will actually be cheaper!
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MASSIVE TYPE IV
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Muffler Mike
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lol.
the only reason i stay out here on the left coast is my winters are 60 degrees and summers are 80. (along the coast) there is no better weather. although some times you cant actually see very far from the smog, but i like to see what i breath.
and yea, the earth does move once in a while. but thats a good thing, because we all want to rotate the earth under our car, and its just a simulation of that.
the only reason i stay out here on the left coast is my winters are 60 degrees and summers are 80. (along the coast) there is no better weather. although some times you cant actually see very far from the smog, but i like to see what i breath.
and yea, the earth does move once in a while. but thats a good thing, because we all want to rotate the earth under our car, and its just a simulation of that.
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MASSIVE TYPE IV
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- Joined: Fri Jul 07, 2000 12:01 am
I personally like being able to step out my back door and go on my own Safari if I want....
I lived there for a tad over 5 years and did like the weather, but 90% of the people are jerks, everything is expensive and there is no where to go without a traffic light or a line that is 5 miles long...
My town has two traffic lights, I don't wait in line anywhere I go and I if I wanna take a leak off my front porch there isn't a damn soul gonna see me!
I lived there for a tad over 5 years and did like the weather, but 90% of the people are jerks, everything is expensive and there is no where to go without a traffic light or a line that is 5 miles long...
My town has two traffic lights, I don't wait in line anywhere I go and I if I wanna take a leak off my front porch there isn't a damn soul gonna see me!
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Muffler Mike
- Posts: 3186
- Joined: Tue Feb 20, 2001 12:01 am
oh yea. food for thought.
those labels read MINIMUM octane.
some time and some places its good, and some on the minimum.
out in california, they change the mixture almost every day. so its never consistant except for the minimum.
per insider at a refinery i know. has stated on some days, the regular will have just as much octane as the premium rating.
then the EPA dictates to the refinerys out here in cali what they need to add to each batch per the air quality that day. (for cali used fuel) thats a small reason we pay a few cents more. the other reasons are ???????
I can tell you, i get better gas mileage when i buy gas outside of california. a lot less additave junk put in.
funny thing is, fuel that goes to places like Arizona out of california can come from a few different manufacturers and gets put in ONE pipe and pumped out, then redistributed by volume put in at the other end to the differnt companies again. i would imagine its a raw stock and additaves are put in at the local regon.
those labels read MINIMUM octane.
some time and some places its good, and some on the minimum.
out in california, they change the mixture almost every day. so its never consistant except for the minimum.
per insider at a refinery i know. has stated on some days, the regular will have just as much octane as the premium rating.
then the EPA dictates to the refinerys out here in cali what they need to add to each batch per the air quality that day. (for cali used fuel) thats a small reason we pay a few cents more. the other reasons are ???????
I can tell you, i get better gas mileage when i buy gas outside of california. a lot less additave junk put in.
funny thing is, fuel that goes to places like Arizona out of california can come from a few different manufacturers and gets put in ONE pipe and pumped out, then redistributed by volume put in at the other end to the differnt companies again. i would imagine its a raw stock and additaves are put in at the local regon.
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Muffler Mike
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- Joined: Tue Feb 20, 2001 12:01 am
LOL.MASSIVE TYPE IV wrote:I personally like being able to step out my back door and go on my own Safari if I want....
I lived there for a tad over 5 years and did like the weather, but 90% of the people are jerks, everything is expensive and there is no where to go without a traffic light or a line that is 5 miles long...
My town has two traffic lights, I don't wait in line anywhere I go and I if I wanna take a leak off my front porch there isn't a damn soul gonna see me!
i guess we are definitly two different people.
I spent about a year in Millageville. (working at what was Grumman att he time) pissed and moaned the whole time, except when i went to drink and drown night.
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Marc
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coolj30, if this is going to be a basic-issue stock carbureted engine with no special cam or combustion chamber/deckheight tricks I've found the following guidelines to be safe - all (R+M)/2 octane ratings:
87: 7.4:1
89: 7.75:1
91: 8.05:1
92: 8.25:1
Back in the days when gas was way under a buck a gallon the cost-per-mile was least on Regular. At today's prices (with the differential between the grades still about what it was then) Regular-buyers are subsidizing those who burn the good stuff and it's like James2 says, your cost-per-mile can be a little less with the higher-octane fuel if you build a motor that can take advantage of it.
If you build it for 89, someday you'll put in 87 for one reason or another and you may not notice any problems...but resist the temptation to stay on the cheaper gas, it'll cost you in engine longevity.
87: 7.4:1
89: 7.75:1
91: 8.05:1
92: 8.25:1
Back in the days when gas was way under a buck a gallon the cost-per-mile was least on Regular. At today's prices (with the differential between the grades still about what it was then) Regular-buyers are subsidizing those who burn the good stuff and it's like James2 says, your cost-per-mile can be a little less with the higher-octane fuel if you build a motor that can take advantage of it.
If you build it for 89, someday you'll put in 87 for one reason or another and you may not notice any problems...but resist the temptation to stay on the cheaper gas, it'll cost you in engine longevity.
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James2
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Did you know that in Georgia 89 octane is a blend of 60% 87 octane regular and 40% 93 octane premium? Blend them half and half you get 90 octane. 91 octane is 65% premium and 35% regular.
At the pumping station, only two grades of gas are pumped for distribution. All the other grades are blended. All the gas, no matter what brand comes from the same tanks. Each company then adds it's own additive package when it's "dumped" in the fuel trucks.
The gas is pumped from the refinery to the distribution points in an 8 in undergrade gas pipe. I know in Georgia the pipe goes from NYC to Floridia.
There is usaully a distribution point every 50-100 miles where the gas trucks fill up. The also pump diesel in the same pipe. The deisel that is mixed with gas is called "mixed fuel". It sold to some power plants and other users that are set up to burn this mixed fuel. The mixed premium and regular gas is sold as regular, so that 87 octane might really be higher.
Anyway, here the standard retail price difference between gas is 10 cents.
So if you burn "mid grade' or the 89 octane, you can often save a few pennies by pumping 4 gallons of premium and 6 gallons of regular. or blend them 50-50 and get 90 octane for the same price as 89 octane.
Also did you know that the premium gas only cost the retailer about 10 cents more then regular. Often we would sell regular at or below cost and any money we made on gas sales came from our sales on Mid grade and Premium .
At the pumping station, only two grades of gas are pumped for distribution. All the other grades are blended. All the gas, no matter what brand comes from the same tanks. Each company then adds it's own additive package when it's "dumped" in the fuel trucks.
The gas is pumped from the refinery to the distribution points in an 8 in undergrade gas pipe. I know in Georgia the pipe goes from NYC to Floridia.
There is usaully a distribution point every 50-100 miles where the gas trucks fill up. The also pump diesel in the same pipe. The deisel that is mixed with gas is called "mixed fuel". It sold to some power plants and other users that are set up to burn this mixed fuel. The mixed premium and regular gas is sold as regular, so that 87 octane might really be higher.
Anyway, here the standard retail price difference between gas is 10 cents.
So if you burn "mid grade' or the 89 octane, you can often save a few pennies by pumping 4 gallons of premium and 6 gallons of regular. or blend them 50-50 and get 90 octane for the same price as 89 octane.
Also did you know that the premium gas only cost the retailer about 10 cents more then regular. Often we would sell regular at or below cost and any money we made on gas sales came from our sales on Mid grade and Premium .
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Marc
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We have several refineries nearby where the crude comes in by tanker from Alaska; the gas is all trucked to the stations and is "brand-name" stuff unless you go to an independent station that buys it wherever they find the best deal.
Back when leaded Regular was still available we played the "brew-yer-own" game by adding a couple of gallons of it per tank of unleaded Premium - the lead seemed to help the antiknock properties of the mix more than the presence of the lower-octane gas hurt it (my wife's 340 Duster was content on such a mix but pinged like a biatch on straight Premium, proof enough for me). You get some funny looks from the gas station clerks, but scrooom, it's your money.
Back when leaded Regular was still available we played the "brew-yer-own" game by adding a couple of gallons of it per tank of unleaded Premium - the lead seemed to help the antiknock properties of the mix more than the presence of the lower-octane gas hurt it (my wife's 340 Duster was content on such a mix but pinged like a biatch on straight Premium, proof enough for me). You get some funny looks from the gas station clerks, but scrooom, it's your money.
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Dave_Darling
- Posts: 2534
- Joined: Thu Apr 27, 2000 12:01 am
A few numbers from the 914 owners manuals.Marc wrote:... I've found the following guidelines to be safe - all (R+M)/2 octane ratings:
87: 7.4:1
89: 7.75:1
91: 8.05:1
92: 8.25:1
The stock US-spec 2.0 liter 914 ran 7.6:1 compression and was spec'ed to use 87 octane fuel. The stock European-spec 2.0 914 ran 8.0:1 compression and was spec'ed to use 89 octane fuel. (Actually 94 RON, but that's 89-90 (R+M)/2 rating.)
I know people who have run 91 in 8.5:1 914s (and a few 9:1, even!) with otherwise stock engines without apparent problems. The 9:1 car sucked a plastic bag into the cooling fan and was rebuilt with 8.5:1 96mm pistons after a relatively short while, though.
Note that the 2.0 914 has the improved spark plug location and larger valves than the other Type IV motors.
I believe the stock 1.7 was 8.2:1 compression, and it was spec'ed for ~91 octane fuel.
--DD
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Piledriver
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I personally know that James2 is right about "premium is cheaper"...
I have been running it fow the last several months since gas prices got stupid, bumped my timing, and only run Chevron Premium...
(1.7 914 44IDFs, with euro pop-ups, no cylinder shims or head gaskets, ~8.5:1)
Hauls and gets significanlty better mileage... Odometer is currently dead, but I get ~ an extra 80 miles/tank. (6 instead of 5 days between fillups, 80 mile/day commute)
One of these days I will rig up the vacuum advance again...
I have been running it fow the last several months since gas prices got stupid, bumped my timing, and only run Chevron Premium...
(1.7 914 44IDFs, with euro pop-ups, no cylinder shims or head gaskets, ~8.5:1)
Hauls and gets significanlty better mileage... Odometer is currently dead, but I get ~ an extra 80 miles/tank. (6 instead of 5 days between fillups, 80 mile/day commute)
One of these days I will rig up the vacuum advance again...
Addendum to Newtons first law:
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
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farmer
- Posts: 2399
- Joined: Fri Dec 07, 2001 12:01 am
Hey Piledriver.
If your engine is stock cammed, I´d be carefull with the vacum advance. Especially in warmer climats like yours. - You might very well get some overheated heads on your hands. You are also closer to 8,7 - 1 with the domed pistons.
I recently had to modify a set of 1,8 heads, ( 412S engine in a T2 bus tho) that were left out of the shims, resulting in 9,1 - 1 CR. On 95 RON. It pinged uphills with 30 degr. advance, even up here. So I raised the deck height a little and massaged tthe chambers so it came down to 8,8 - 1. now the Safeguard tells us we are OK. I made a 009 for it with shorter advance.
T.
If your engine is stock cammed, I´d be carefull with the vacum advance. Especially in warmer climats like yours. - You might very well get some overheated heads on your hands. You are also closer to 8,7 - 1 with the domed pistons.
I recently had to modify a set of 1,8 heads, ( 412S engine in a T2 bus tho) that were left out of the shims, resulting in 9,1 - 1 CR. On 95 RON. It pinged uphills with 30 degr. advance, even up here. So I raised the deck height a little and massaged tthe chambers so it came down to 8,8 - 1. now the Safeguard tells us we are OK. I made a 009 for it with shorter advance.
T.