>>>The world is so gullible to waht is printed within the pages of a book!<<<
6.6:1 requiring 88 octane is what the mexican acvw factory documentation said... i saw it, back in the '80's, and that's how i ran my 1776 back then... with great results.
knowing what i know today about running too much deck height, tho, i'd be looking at those new mexican heads... i believe that semi-hemi cutting is only good for maybe 5-7 cc's(?), so more deck is required if you want to get the c.r. down low.
has anyone heard of the s.a.e. j312 publication, "automotive gasolines - recommended practice"?
"For a typical carburetted engine,
without engine management:
( Full Throttle )
Compression Ratio vs. Octane Number Requirement
6:1- 81
7:1- 87
8:1- 92
9:1- 96
10:1- 100"
and then there is: "Increasing the water jacket temperature from 71C to 82C, increases the (R+M)/2) ONR(octane number requirement) by two." -Technical Publication - Motor Gasolines Chevron Research and Technology Company (1990)
clyde berg has documented a 100 degree/f increase in type 1 head temps under severe load... apply that math to the s.a.e. recommendations, and see how much static c.r. is really safe for your engine.
>>>on the semi-hemi cut acvw heads the head is cut above the valves to your sticking the valves toward the bottom of the combustion chamber instead of keeping them at the top(where they should be).<<<
what kind of gibberish is this? the semi-hemi acvw head cut does NOT take place "above the valves"... and you are NOT "sticking the valves toward the bottom of the combustion chamber".
dan
oceanstreetvideo.com
[This message has been edited by danimal (edited 10-31-2001).]
2110 Compression Ratio Suggestions
-
Bruce2
- Posts: 7105
- Joined: Sat Oct 13, 2001 1:01 am
2110 Compression Ratio Suggestions
Something dosen't add up Dan.
"6.6:1 requiring 88 octane is what the mexican acvw factory documentation said... i saw it, back in the '80's, and that's how i ran my 1776 back then... with great results."
Since the pumps in Mex haven't had octane ratings up until last year, why would the factory spec the octane knowing the car's owner couldn't comply with the spec? And, on what scale is that 88 octane requirement?
Today's engines at 7.75:1 do spec Magna Sin, which is 87 octane. True, injection allows higher CR, but since you can get all the way up to 91, wouldn't this support at least 8 or 8.25:1 with a stock carb?
"6.6:1 requiring 88 octane is what the mexican acvw factory documentation said... i saw it, back in the '80's, and that's how i ran my 1776 back then... with great results."
Since the pumps in Mex haven't had octane ratings up until last year, why would the factory spec the octane knowing the car's owner couldn't comply with the spec? And, on what scale is that 88 octane requirement?
Today's engines at 7.75:1 do spec Magna Sin, which is 87 octane. True, injection allows higher CR, but since you can get all the way up to 91, wouldn't this support at least 8 or 8.25:1 with a stock carb?
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danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
2110 Compression Ratio Suggestions
>>>Since the pumps in Mex haven't had octane ratings up until last year, why would the factory spec the octane knowing the car's owner couldn't comply with the spec? And, on what scale is that 88 octane requirement?<<<
first off, i can't see how any automotive factory can build a car engine for the general public without specifying an octane requirement... even in mexico, where anything is possible :-0
good point about the octane scale... america moved to clc standards in, what, the mid '70's? if mexico still had a ron scale in the early '80's, that high 88 octane figure would have made more sense... i should have checked it out before i went to 6.6:1.
fwiw, there is a webpage on the 'net that details a bmw bike trip to guatemala a few years ago... they claimed to have brought back mexican gas, tested it, and found it to be 67(!) octane.
>>>True, injection allows higher CR, but since you can get all the way up to 91, wouldn't this support at least 8 or 8.25:1 with a stock carb?<<<
those octane figures i posted would seem to indicate that... until you calculate in the affects of those head temp changes, AND the affects of air temps and humidity on octane requirements:
"An increase in ambient air temperature of 5.6C increases the octane requirement of an engine by 0.44 - 0.54 MON"
"An increase of absolute humidity of 1.0 g water/kg of dry air lowers the octane requirement of an engine by 0.25 - 0.32 MON"
i believe that high humidity lowers e.t. at the drag strip with an all-motor car, but it also prevents detonation(ala water injection).
so the octane requirements for a motor in the dripping backwoods of georgia would be different from 115+ degree summer heat in phoenix... same thing with a mex motor, the factory has to build it for the worst possible scenario.
dan
oceanstreetvideo.com
first off, i can't see how any automotive factory can build a car engine for the general public without specifying an octane requirement... even in mexico, where anything is possible :-0
good point about the octane scale... america moved to clc standards in, what, the mid '70's? if mexico still had a ron scale in the early '80's, that high 88 octane figure would have made more sense... i should have checked it out before i went to 6.6:1.
fwiw, there is a webpage on the 'net that details a bmw bike trip to guatemala a few years ago... they claimed to have brought back mexican gas, tested it, and found it to be 67(!) octane.
>>>True, injection allows higher CR, but since you can get all the way up to 91, wouldn't this support at least 8 or 8.25:1 with a stock carb?<<<
those octane figures i posted would seem to indicate that... until you calculate in the affects of those head temp changes, AND the affects of air temps and humidity on octane requirements:
"An increase in ambient air temperature of 5.6C increases the octane requirement of an engine by 0.44 - 0.54 MON"
"An increase of absolute humidity of 1.0 g water/kg of dry air lowers the octane requirement of an engine by 0.25 - 0.32 MON"
i believe that high humidity lowers e.t. at the drag strip with an all-motor car, but it also prevents detonation(ala water injection).
so the octane requirements for a motor in the dripping backwoods of georgia would be different from 115+ degree summer heat in phoenix... same thing with a mex motor, the factory has to build it for the worst possible scenario.
dan
oceanstreetvideo.com
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Steve Arndt
- Posts: 7420
- Joined: Sat Mar 10, 2001 12:01 am
2110 Compression Ratio Suggestions
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by yeahmag:
<B>Ok... Here is the update on the engine.
2276 (82x94)
Scat I Beam rods
WebCam 121/125
Fancy pants lifters with the hole in 'em
around 9.0:1 CR
AJ Simms heads 42x37 full p&p matched manifolds
New Case (RIMCO machine work)
Dog house
Full flowed
1.5 deep sump
(external cooler by summer time)
Still the 36 Dells until more $ is available
[This message has been edited by yeahmag (edited 10-31-2001).]</B><HR></BLOCKQUOTE>
I can say first hand, you will drop a load in your pants the first time you grab second gear!!!! I have the same combo except more radically hogged out heads, 86B webcam, and 9.4:1.
Oh yeah, I'm pulling it down to shim up my intake springs for more pressure and upgrading my oiling system, at the same time I'm going to flycut the heads AND reduce deck. You guys will know first hand if it works or not, and how it runs.
I had 70 miles total (total, 100% brand new) on the said 2276 and drove it 750 miles round trip to SLC from Boise and back this August in 102 degree heat. No problems.
[This message has been edited by Steve Arndt (edited 10-31-2001).]
<B>Ok... Here is the update on the engine.
2276 (82x94)
Scat I Beam rods
WebCam 121/125
Fancy pants lifters with the hole in 'em
around 9.0:1 CR
AJ Simms heads 42x37 full p&p matched manifolds
New Case (RIMCO machine work)
Dog house
Full flowed
1.5 deep sump
(external cooler by summer time)
Still the 36 Dells until more $ is available
[This message has been edited by yeahmag (edited 10-31-2001).]</B><HR></BLOCKQUOTE>
I can say first hand, you will drop a load in your pants the first time you grab second gear!!!! I have the same combo except more radically hogged out heads, 86B webcam, and 9.4:1.
Oh yeah, I'm pulling it down to shim up my intake springs for more pressure and upgrading my oiling system, at the same time I'm going to flycut the heads AND reduce deck. You guys will know first hand if it works or not, and how it runs.
I had 70 miles total (total, 100% brand new) on the said 2276 and drove it 750 miles round trip to SLC from Boise and back this August in 102 degree heat. No problems.
[This message has been edited by Steve Arndt (edited 10-31-2001).]
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yeahmag
- Posts: 343
- Joined: Wed Jul 11, 2001 12:01 am
2110 Compression Ratio Suggestions
Ha!!!! OMG! Thanks!
-Aaron
-Aaron
-
MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
It never ceases to amaze me that these conversations reiterate the same words...
Tell ya what:
I have a dyno, sitting 12 feet from this computer, and would be willing to prove several points, I normally don't even fool with Dynoing our different type I engin combos, as they are set in stone, however i would be willing to donate my time to see the changes under exacting changes and post it all to the forums, and maybe even some journalist.
I have tons of parts to play with, maybe one of those journalist could come and observe to be the referee for a no cheat type of atmosphere.....
I have already done the testing, on the dyno and on the street. I know what added CR can do, on both ends of the spectrum...Lets prove it...
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
Tell ya what:
I have a dyno, sitting 12 feet from this computer, and would be willing to prove several points, I normally don't even fool with Dynoing our different type I engin combos, as they are set in stone, however i would be willing to donate my time to see the changes under exacting changes and post it all to the forums, and maybe even some journalist.
I have tons of parts to play with, maybe one of those journalist could come and observe to be the referee for a no cheat type of atmosphere.....
I have already done the testing, on the dyno and on the street. I know what added CR can do, on both ends of the spectrum...Lets prove it...
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
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danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
2110 Compression Ratio Suggestions
>>>I have already done the testing, on the dyno and on the street. I know what added CR can do, on both ends of the spectrum...Lets prove it...<<<
without knock sensors you haven't done squat, because you don't know when the engine is at incipient knock.
so you'll never be able to make the maximum reliable h.p. that a new car does.
and how do you expect to prove anything on a dyno without knock sensing capability? lol... jake, i suppose you could improve your stone age tuning techniques by putting someone out there with a broomstick against the side of the case... i nominate dave cormack
>>>on the said 2276 and drove it 750 miles round trip to SLC from Boise and back this August in 102 degree heat.<<<
yeah, but at only 26 degrees advance... sounds like another caveman using audible knocking to tune his motor.
steve, before you start screwing around with that engine, how about running a few tanks of race gas thru it, with the timing set at 30-32 degrees... i'd like to know if that engine reaches it's optimal h.p. when there is enuf octane to feed the compression...
why? because a 10-degree spread in timing over the optimal mid-point can change the octane requirements by 8 or more points... there can be a lot of power lost when the timing is retarded from optimal.
dan
oceanstreetvideo.com
without knock sensors you haven't done squat, because you don't know when the engine is at incipient knock.
so you'll never be able to make the maximum reliable h.p. that a new car does.
and how do you expect to prove anything on a dyno without knock sensing capability? lol... jake, i suppose you could improve your stone age tuning techniques by putting someone out there with a broomstick against the side of the case... i nominate dave cormack
>>>on the said 2276 and drove it 750 miles round trip to SLC from Boise and back this August in 102 degree heat.<<<
yeah, but at only 26 degrees advance... sounds like another caveman using audible knocking to tune his motor.
steve, before you start screwing around with that engine, how about running a few tanks of race gas thru it, with the timing set at 30-32 degrees... i'd like to know if that engine reaches it's optimal h.p. when there is enuf octane to feed the compression...
why? because a 10-degree spread in timing over the optimal mid-point can change the octane requirements by 8 or more points... there can be a lot of power lost when the timing is retarded from optimal.
dan
oceanstreetvideo.com
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MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
Oh, but Dan.....How about 3 different hall sensors, one of which is actually working through my Pafz2 program from electromotive,even running carbs the hall sensor is still gathering data and sending it to the monitor. I may not be on the west coast, but i do have tons of capabilities.
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
-
JohnConnolly
- Posts: 3336
- Joined: Thu Apr 13, 2000 12:01 am
2110 Compression Ratio Suggestions
I've been quiet for a while, but I can't hold it anymore.
Dan, you are stepping on toes with your ignorance this time. Ignition advance is not like penis size (more/bigger is better; NOT).
Steve runs 26 degrees total, which means his burn is FAST AND CLEAN. I know guys running 18 degrees full advance, with 7 at idle. The power they have will tear the frickin' engine mounts if they didn't have a berg mount on there. You tear the heads off, and there is absolutely NO CARBON in the chamber, or on the pistons. Ever see what the piston tops and chamber on a semi-heme engine looks like after only 10K miles?
I'll be running a similar combo (high compression, TIGHT deck) this spring with our new piston and chamber, and I plan on running no more than 20 degrees full centrifugal advance, with another 10 of vacuum for MPG and cooler running, AND no hesitation.
There is NOTHING WRONG with only running 26 degrees advance, if that's what the engine needs (what's a Vortec run? How about a Honda? I have no idea, I'm asking. They run 40 degrees total?)
Less total advance means less negative torque, which is inefficient and causes engine vibration. This is one of the reasons the 36-40 degrees total advance is ludicrous (semi-hemi) if you desire an efficient VW engine.
Steve ran the 32 total, and 30 degrees, and it knocked big time, so I recommended he back it down. NOTHING WRONG WITH THAT. If it runs great at 10 degrees total, NOTHING WRONG WITH THAT. If it runs great at 40 degrees total, NOTHING WRONG WITH THAT. Slamming him because he's running a configuration that is a "black sheep" compared to what most people consider "within normal range" is short sighted and ignorant. I plan on "breaking" MANY supposed "rules" about what you can and can't do with my new engine, and we'll see how it works out, I won't BS anyone. If it doesn't work, I'll say it doesn't work, and hit the drawing board again. But, if it DOES WORK, the low compression "experts" have a LOT of explaining to do, on how Steve, Jake, and I are accomplishing the "impossible".
How about giving Steve props for his efforts instead of always slamming him since it don't adhere to "your" rules of how an engine should be built? How about saying, "Good job Steve, I'd love to drive your car and see how it runs"? I'm sure he'd welcome you and you can see for yourself first hand how it's working. He's hardly claiming it's perfect, but give him credit for what he's doing, and TRYING to do, which isn't following the formula for a "good engine". If it's all been done before, let's all quit this hobby since it's frickin' boring (someone did it, snore).
After all, we are all VW fans, if you are going to shoot your mouth off and slam him, go to a Honda board or hang out with James Lutz.
I've said this before, and I'll say it again; there is a new generation of VW guys coming into view right now, and it's pissing off alot of the "old school experts" on what ou can and can't do. Either open your mind and try to follow what's going on, or get the hell out of the way, cause' progress is being made, whether you like it or not.
John
Aircooled.Net Inc.
Dan, you are stepping on toes with your ignorance this time. Ignition advance is not like penis size (more/bigger is better; NOT).
Steve runs 26 degrees total, which means his burn is FAST AND CLEAN. I know guys running 18 degrees full advance, with 7 at idle. The power they have will tear the frickin' engine mounts if they didn't have a berg mount on there. You tear the heads off, and there is absolutely NO CARBON in the chamber, or on the pistons. Ever see what the piston tops and chamber on a semi-heme engine looks like after only 10K miles?
I'll be running a similar combo (high compression, TIGHT deck) this spring with our new piston and chamber, and I plan on running no more than 20 degrees full centrifugal advance, with another 10 of vacuum for MPG and cooler running, AND no hesitation.
There is NOTHING WRONG with only running 26 degrees advance, if that's what the engine needs (what's a Vortec run? How about a Honda? I have no idea, I'm asking. They run 40 degrees total?)
Less total advance means less negative torque, which is inefficient and causes engine vibration. This is one of the reasons the 36-40 degrees total advance is ludicrous (semi-hemi) if you desire an efficient VW engine.
Steve ran the 32 total, and 30 degrees, and it knocked big time, so I recommended he back it down. NOTHING WRONG WITH THAT. If it runs great at 10 degrees total, NOTHING WRONG WITH THAT. If it runs great at 40 degrees total, NOTHING WRONG WITH THAT. Slamming him because he's running a configuration that is a "black sheep" compared to what most people consider "within normal range" is short sighted and ignorant. I plan on "breaking" MANY supposed "rules" about what you can and can't do with my new engine, and we'll see how it works out, I won't BS anyone. If it doesn't work, I'll say it doesn't work, and hit the drawing board again. But, if it DOES WORK, the low compression "experts" have a LOT of explaining to do, on how Steve, Jake, and I are accomplishing the "impossible".
How about giving Steve props for his efforts instead of always slamming him since it don't adhere to "your" rules of how an engine should be built? How about saying, "Good job Steve, I'd love to drive your car and see how it runs"? I'm sure he'd welcome you and you can see for yourself first hand how it's working. He's hardly claiming it's perfect, but give him credit for what he's doing, and TRYING to do, which isn't following the formula for a "good engine". If it's all been done before, let's all quit this hobby since it's frickin' boring (someone did it, snore).
After all, we are all VW fans, if you are going to shoot your mouth off and slam him, go to a Honda board or hang out with James Lutz.
I've said this before, and I'll say it again; there is a new generation of VW guys coming into view right now, and it's pissing off alot of the "old school experts" on what ou can and can't do. Either open your mind and try to follow what's going on, or get the hell out of the way, cause' progress is being made, whether you like it or not.
John
Aircooled.Net Inc.
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MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
Hell Yeah!!!
John is right, full steam ahead...we are not slowing down.
John and I will make some enemies along the way, but also some friends.
Backing timing off is no problem, we do alot of engines for Shriners and their toys. Alot of them want huge torque so we run a 2275 with 9.5:1 and a 121/125 Web grind...The engines scream and run as cool as most smaller engines..we run 24 degrees full advance on most of these.
Its pretty simple. The more compression, the later you can light the flame safely. With low CR you have to light the flame very early in hopes of burning most of the mixture. Once I made an engine blow engine with 5:1 CR. It ran but it needed over 75 degrees full advance to even fire up...It lasted forever, but still got hot.
I can second John on the way a 10K mile Semi Hemi engine looks, like crap...So rich that flakes crumble off the pistons.
John is right, full steam ahead...we are not slowing down.
John and I will make some enemies along the way, but also some friends.
Backing timing off is no problem, we do alot of engines for Shriners and their toys. Alot of them want huge torque so we run a 2275 with 9.5:1 and a 121/125 Web grind...The engines scream and run as cool as most smaller engines..we run 24 degrees full advance on most of these.
Its pretty simple. The more compression, the later you can light the flame safely. With low CR you have to light the flame very early in hopes of burning most of the mixture. Once I made an engine blow engine with 5:1 CR. It ran but it needed over 75 degrees full advance to even fire up...It lasted forever, but still got hot.
I can second John on the way a 10K mile Semi Hemi engine looks, like crap...So rich that flakes crumble off the pistons.
-
James2
- Posts: 3148
- Joined: Fri Mar 16, 2001 12:01 am
2110 Compression Ratio Suggestions
I like Dan. Well, a little anyways.
I also know that a lot of people are running high CR. And it's working for them.
Dan, how can you say that it's wrong, or will not work, when it does work for so many people?
Why is the total advance important? even with the 26 degrees, he is still making more power then the same engine with 7-1 and 38 degrees.
I also know that a lot of people are running high CR. And it's working for them.
Dan, how can you say that it's wrong, or will not work, when it does work for so many people?
Why is the total advance important? even with the 26 degrees, he is still making more power then the same engine with 7-1 and 38 degrees.
-
MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
2110 Compression Ratio Suggestions
Yes, it does work..
I have not built an engine with less than 7.7:1 CR for a lightweight car in 3 years. Most of them are at 8.3:1 with no problems.
Looks like if It did not work some of these customers would have complained..
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
I have not built an engine with less than 7.7:1 CR for a lightweight car in 3 years. Most of them are at 8.3:1 with no problems.
Looks like if It did not work some of these customers would have complained..
------------------
Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
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JohnConnolly
- Posts: 3336
- Joined: Thu Apr 13, 2000 12:01 am
2110 Compression Ratio Suggestions
Let me elaborate a little bit.
In a conventional otto engine (that's us), you want the cylinder pressure to maximize around 10-15 degrees ATDC. Any sooner than this and the piston and rod have no leverage on the crank, and you have detonation.
Combustion doesn't happen in an instant. Any later than 10-15 degrees ATDC and combustion doesn't do as much pushing of the piston (and spinning of the crank), and then combustion continues IN THE EXHAUST PIPE (hot exhaust? Try advancing your timing).
In a perfect world, we could ignite ALL the air/fuel mixture at 10 degrees ATDC and away we go. But, it's not a perfect world, and combustion takes time, so we have to ignite it ahead of time. This is also why we need an advance curve, the faster the engine is turning, the more "lead" we need to ensure that we are pushing the piston at 10-15 ATDC.
So, any engine that needs 40 degrees of ignition advance, think about how fast combustion is taking place in that chamber. And once it gets to 10 degrees ATDC, "burn" still goes just as slow. All the while guys like Steve, Jake, and me are finding ways to make a chamber that burns FASTER, so we don't have as much ignition lead. THAT means that combustion is done before BDC, or at least one heck of a lot more than a slow burning chamber.
Which brings me to compression.
Example #1: a furnace. How much compression does it run? It's sole purpose is to CREATE HEAT, not "work". The more compression you run, the more work you produce (Thermodynamics, Level 1), which means there is less energy left over to create heat out you exhaust. An efficient engine has very LOW EGTs, since you've already converted a lot of heat energy into mechanical energy.
The concept is fairly simple, but execution isn't, yet I have no idea why some guys keep professing that LOW compression results in a cooler running engine (it doesn't, they run hotter). What low compression DOES DO is give you a margin for error (cheap gas, etc), to still not detonate. But somehow the true purpose of low compression has gotten lost over the years, and been transmorgified into some "cure all" to the aircooled VW engine. WRONG. Engines with LOW (under 7:1) compression run OK, but they do keep guys that are afraid to maintain or be aware of their car, from getting into trouble since they have a larger margin for error. If you don't want to "worry" about your car, run 6.5:1, and change the oil every 20K miles. If you want to get the most out of it, push the envelope on compression, match it to the application (cam, vehicle, gearing, CLIMATE, etc), and pay attention to it.
Dan,
7:1 may be perfect for your application, but it sure as hell ain't for mine (I don't plan on banzai runs to Mexico City). You did bring up a good point though; if I was building an engine for someone in Phoenix or the Mojave, I would back off on the compression a bit, since those guys see 20 degrees more ambient temp then anywhere else. In addition, it's dry heat, so there's no moisture on these hot days, which means without water, there's more "oxygen in the air" and you run leaner and make more power than in a humid climate.
Anyways, back on topic...... What works for you is fine, what works for us is fine, but if it works, IT WORKS. How about understanding WHY and patting guys on the back, instead of naysaying and slamming their efforts.
John
Aircooled.Net Inc.
In a conventional otto engine (that's us), you want the cylinder pressure to maximize around 10-15 degrees ATDC. Any sooner than this and the piston and rod have no leverage on the crank, and you have detonation.
Combustion doesn't happen in an instant. Any later than 10-15 degrees ATDC and combustion doesn't do as much pushing of the piston (and spinning of the crank), and then combustion continues IN THE EXHAUST PIPE (hot exhaust? Try advancing your timing).
In a perfect world, we could ignite ALL the air/fuel mixture at 10 degrees ATDC and away we go. But, it's not a perfect world, and combustion takes time, so we have to ignite it ahead of time. This is also why we need an advance curve, the faster the engine is turning, the more "lead" we need to ensure that we are pushing the piston at 10-15 ATDC.
So, any engine that needs 40 degrees of ignition advance, think about how fast combustion is taking place in that chamber. And once it gets to 10 degrees ATDC, "burn" still goes just as slow. All the while guys like Steve, Jake, and me are finding ways to make a chamber that burns FASTER, so we don't have as much ignition lead. THAT means that combustion is done before BDC, or at least one heck of a lot more than a slow burning chamber.
Which brings me to compression.
Example #1: a furnace. How much compression does it run? It's sole purpose is to CREATE HEAT, not "work". The more compression you run, the more work you produce (Thermodynamics, Level 1), which means there is less energy left over to create heat out you exhaust. An efficient engine has very LOW EGTs, since you've already converted a lot of heat energy into mechanical energy.
The concept is fairly simple, but execution isn't, yet I have no idea why some guys keep professing that LOW compression results in a cooler running engine (it doesn't, they run hotter). What low compression DOES DO is give you a margin for error (cheap gas, etc), to still not detonate. But somehow the true purpose of low compression has gotten lost over the years, and been transmorgified into some "cure all" to the aircooled VW engine. WRONG. Engines with LOW (under 7:1) compression run OK, but they do keep guys that are afraid to maintain or be aware of their car, from getting into trouble since they have a larger margin for error. If you don't want to "worry" about your car, run 6.5:1, and change the oil every 20K miles. If you want to get the most out of it, push the envelope on compression, match it to the application (cam, vehicle, gearing, CLIMATE, etc), and pay attention to it.
Dan,
7:1 may be perfect for your application, but it sure as hell ain't for mine (I don't plan on banzai runs to Mexico City). You did bring up a good point though; if I was building an engine for someone in Phoenix or the Mojave, I would back off on the compression a bit, since those guys see 20 degrees more ambient temp then anywhere else. In addition, it's dry heat, so there's no moisture on these hot days, which means without water, there's more "oxygen in the air" and you run leaner and make more power than in a humid climate.
Anyways, back on topic...... What works for you is fine, what works for us is fine, but if it works, IT WORKS. How about understanding WHY and patting guys on the back, instead of naysaying and slamming their efforts.
John
Aircooled.Net Inc.
-
danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
2110 Compression Ratio Suggestions
>>>Ignition advance is not like penis size (more/bigger is better; NOT).<<<
good buddy, you have certainly convinced me that your penis size goes "hand in hand" with the c.r. you run
>>>There is NOTHING WRONG with only running 26 degrees advance, if that's what the engine needs... Steve ran the 32 total, and 30 degrees, and it knocked big time<<<
of course it knocked big time... wtf did you expect was going to happen with 9.4:1 c.r. on a pump gas acvw motor?
after all, he's running the same basic combustion chamber shape we have all been running for decades... plus he's running carbs to boot!
did it ever occur to you that steve's motor almost certainly has inaudible knocking at 26 degrees advance?
so it's NOT a question of "what the engine needs"... it's a question of what octane is required for the c.r. he's using.
>>>Why is the total advance important? even with the 26 degrees, he is still making more power then the same engine with 7-1 and 38 degrees.<<<
yeah, but how long will his motor live?
o.k., it's quiz time for all you geniuses:
1)would steve's engine make more h.p. if octane didn't matter, and he was able to run 30-32 degrees advance?
2)would steve's engine make more h.p. if he was able to lower the c.r. just enuf to run more advance on pump gas?
>>>I've said this before, and I'll say it again; there is a new generation of VW guys coming into view right now<<<
building a high c.r. time bomb that is not capable of running factory advance on pump gas is nothing new, my friend... people have been doing it for decades.
you guys basically went in and stupidly ignored all the acvw automotive engineering data that's been accumulated over the last 50 years... let's re-invent the wheel, right?
and then steve conveniently forgot to mention to everyone that his motor can't handle factory timing... DUH.
how many poor kids like "yeahmag" have you guys lead astray?
dan
oceanstreetvideo.com
good buddy, you have certainly convinced me that your penis size goes "hand in hand" with the c.r. you run
>>>There is NOTHING WRONG with only running 26 degrees advance, if that's what the engine needs... Steve ran the 32 total, and 30 degrees, and it knocked big time<<<
of course it knocked big time... wtf did you expect was going to happen with 9.4:1 c.r. on a pump gas acvw motor?
after all, he's running the same basic combustion chamber shape we have all been running for decades... plus he's running carbs to boot!
did it ever occur to you that steve's motor almost certainly has inaudible knocking at 26 degrees advance?
so it's NOT a question of "what the engine needs"... it's a question of what octane is required for the c.r. he's using.
>>>Why is the total advance important? even with the 26 degrees, he is still making more power then the same engine with 7-1 and 38 degrees.<<<
yeah, but how long will his motor live?
o.k., it's quiz time for all you geniuses:
1)would steve's engine make more h.p. if octane didn't matter, and he was able to run 30-32 degrees advance?
2)would steve's engine make more h.p. if he was able to lower the c.r. just enuf to run more advance on pump gas?
>>>I've said this before, and I'll say it again; there is a new generation of VW guys coming into view right now<<<
building a high c.r. time bomb that is not capable of running factory advance on pump gas is nothing new, my friend... people have been doing it for decades.
you guys basically went in and stupidly ignored all the acvw automotive engineering data that's been accumulated over the last 50 years... let's re-invent the wheel, right?
and then steve conveniently forgot to mention to everyone that his motor can't handle factory timing... DUH.
how many poor kids like "yeahmag" have you guys lead astray?
dan
oceanstreetvideo.com
-
danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
2110 Compression Ratio Suggestions
>>>Oh, but Dan.....How about 3 different hall sensors,<<<
hall effect Definition: The production of an e.m.f. within a conductor or semiconductor through which a current is flowing when there is a strong transverse magnetic field.
in other words, hall effect sensors are what's used in breakerless ignition.
afaik, they are NOT used for knock/vibration sensing... the electromotive hardware specs recommend a purpose-designed microphone for that useage: gm part number 1997562.
so you really don't have knock sensing capability in your shop... you are using the same caveman tuning techniques that we all use.
dan
oceanstreetvideo.com
hall effect Definition: The production of an e.m.f. within a conductor or semiconductor through which a current is flowing when there is a strong transverse magnetic field.
in other words, hall effect sensors are what's used in breakerless ignition.
afaik, they are NOT used for knock/vibration sensing... the electromotive hardware specs recommend a purpose-designed microphone for that useage: gm part number 1997562.
so you really don't have knock sensing capability in your shop... you are using the same caveman tuning techniques that we all use.
dan
oceanstreetvideo.com