Why did mazda retard timing at idle on carb'd 12A?
04-10-07, 08:18 AM
#76
Absolute Power is Awesome
Originally Posted by Rogue_Wulff
Engineers have no credibility with me. As for Yaw's write up, I already answered that. Yes, it's wrong, and I told him so. He never bothered to respond.
Hook it however you want, I don't care. I know what the correct method is, and I use it.
I'm done with this rediculous thread. You can make a person go to school, but you can't make them learn.
Hook it however you want, I don't care. I know what the correct method is, and I use it.
I'm done with this rediculous thread. You can make a person go to school, but you can't make them learn.
Last edited by purple82; 04-10-07 at 08:30 AM.
04-10-07, 08:22 AM
#77
Absolute Power is Awesome
Originally Posted by REVHED
I believe you are the one who is under a misconception. Read the WHOLE article. The vacuum is taken from just above the throttle plates so there is no vacuum at idle. But, as soon as you crack the throttle it uncovers the port which is then exposed to manifold vacuum! Having the port way above the throttle would be redundant as it would advance at virtually the same rate as the centrifugal advance.
The part I've underlined explains this clear as day. Vacuum advance is for low engine speed/load. The only reason it's above the throttle is to prevent advance at idle in some cases. I hope this puts an end to this nonsense.
The part I've underlined explains this clear as day. Vacuum advance is for low engine speed/load. The only reason it's above the throttle is to prevent advance at idle in some cases. I hope this puts an end to this nonsense.
Even though the port is above on the outside of the throttle, there will still be a small vacuum signal due to the idle control pulling air around the throttle plate. It's not going to be as large as when the throttle is open though.
But vacuum advance follows load folks, and as load increases the vacuum advance decreases. It's because of mixture variation at different loads. As the mixture changes so does the flame speed so to get the max pressure at the right cranck angle, you have to vary the spark point.
Last edited by purple82; 04-10-07 at 08:29 AM.
04-10-07, 08:24 AM
#78
Absolute Power is Awesome
Originally Posted by Kentetsu
But you're saying the same thing I am! No advance at idle, only at low rpms when you put a load on it (open the throttle plates). The two sentences after the part you underlined explains how this works.
Last edited by purple82; 04-10-07 at 08:31 AM.
04-10-07, 09:19 AM
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Originally Posted by Kentetsu
But you're saying the same thing I am! No advance at idle, only at low rpms when you put a load on it (open the throttle plates). The two sentences after the part you underlined explains how this works.
04-10-07, 09:21 AM
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Originally Posted by djjjr42
The only nonsense I hope to see put to an end is a$$holish remarks and interactions with others like this from kids with no human relations skills. See sig. 
04-10-07, 10:56 AM
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Originally Posted by REVHED
**** off newbie. No one cares what you think.
You have no concept of respect for others, and contrary to what that tiny thing rattling around in that thick skull of yours may be telling you, you're not always right, no one is. If you ran off at the mouth like that around where I come from, you'd be smacked across the head by any elder within earshot - in what would most likely be a futile attempt to knock some sense into you. 
Grow up already!Since you're obviously a superb retainer of what you read, here is some suggested reading for you: ""How to Win Friends and Influence People" by Dale Carnegie
Last edited by djjjr42; 04-10-07 at 11:21 AM.
04-10-07, 11:00 AM
#82
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Originally posted by purple82
And I understand why you don't have respect for engineers.
And I understand why you don't have respect for engineers.
...we're ALL engineers..Still waiting on the mpg results from the folks who have gone with the red diagram...better than 25 mp avg or just wasting your time following questionable advice?...
04-10-07, 12:07 PM
#83
Yes I went with the red diagram but I can just as easily move the tube to the other nipple. I don't see what the big deal is.
It's not my car so I can't perform any long term comparisons.
It's an '84 auto that REQUIRES a smooth strong idle. Good gas mileage is a plus but having already upped the primary jet size to 95 and modded the accel pump for more volume, it's not as important to me as the idle quality.
mar3, are you confirming in the public record that the red diagram is incorrect? Have you tried it both ways yourself? Has anyone tried it both ways?
We need more posts about practical tests and less argumentative pissing contests. Because of this thread, I've lost respect for one person and the credibility of the other person has remained steady. I wasn't expecting much of practical value from the third person, and his didn't dissapoint.
I will appearantly need to inform the owner about this thread (and tell him to avoid the argument posts), to try it both ways and pick which ever works best. It takes like 10 seconds to pull the tube off and push it on the other nipple while swapping the vacuum cap. Quicker than checking your oil. No need for 6 freaking pages.
It's not my car so I can't perform any long term comparisons.
It's an '84 auto that REQUIRES a smooth strong idle. Good gas mileage is a plus but having already upped the primary jet size to 95 and modded the accel pump for more volume, it's not as important to me as the idle quality.
mar3, are you confirming in the public record that the red diagram is incorrect? Have you tried it both ways yourself? Has anyone tried it both ways?
We need more posts about practical tests and less argumentative pissing contests. Because of this thread, I've lost respect for one person and the credibility of the other person has remained steady. I wasn't expecting much of practical value from the third person, and his didn't dissapoint.
I will appearantly need to inform the owner about this thread (and tell him to avoid the argument posts), to try it both ways and pick which ever works best. It takes like 10 seconds to pull the tube off and push it on the other nipple while swapping the vacuum cap. Quicker than checking your oil. No need for 6 freaking pages.
04-10-07, 12:35 PM
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Originally Posted by Rogue_Wulff
But I ain't wrong. Using the workshop manual to find the right port is excellent advice, as it backs up what I have been trying to tell you. Even the vacuum diagram under the hood shows where the vac line should be hooked up.
Manifold vacuum drops as the throttle is opened, while venturi vacuum increases as it's opened. Don't take my word on it, though. Use a vacuum guage and test it for yourself.
I don't come on here trying to prove I'm right by backing up what I say with degrees and other stuff that says I be edumacated, instead I stated what every old-school hot rodder has known for years.
The vac advance increases timing under lower RPM's and engine loads by using venturi vacuum, because under those conditions, manifold vacuum is actually decreasing. Why do you think the brake booster has a check valve in it?
Manifold vacuum drops as the throttle is opened, while venturi vacuum increases as it's opened. Don't take my word on it, though. Use a vacuum guage and test it for yourself.
I don't come on here trying to prove I'm right by backing up what I say with degrees and other stuff that says I be edumacated, instead I stated what every old-school hot rodder has known for years.
The vac advance increases timing under lower RPM's and engine loads by using venturi vacuum, because under those conditions, manifold vacuum is actually decreasing. Why do you think the brake booster has a check valve in it?
This guy knows what he is talking about. As much as I hate carburetors and all the stupid things that come with carbs they are pretty easy to understand. As engine load increases more fuel is needed. So its fairly easy to understand that the carb needs to ingest more fuel to maintain the correct air fuel ratios. For the carb to suck in more fuel it needs to draw vacuum.
Personally I would never buy a car without Fuel Injection though!
http://auto.howstuffworks.com/question377.htm
From what I have heard from tuners is that Jeff Hartman's book isn't god's gift and shouldn't be treated so.
Education does not make you a car mechanic, tuner, or an engineer for that matter IMO. Only experience, self learning and applying principals are the only way to fully understand engines and how they operate.
04-10-07, 12:52 PM
#85
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Originally Posted by REVHED
I believe you are the one who is under a misconception. Read the WHOLE article. The vacuum is taken from just above the throttle plates so there is no vacuum at idle. But, as soon as you crack the throttle it uncovers the port which is then exposed to manifold vacuum! Having the port way above the throttle would be redundant as it would advance at virtually the same rate as the centrifugal advance.
The part I've underlined explains this clear as day. Vacuum advance is for low engine speed/load. The only reason it's above the throttle is to prevent advance at idle in some cases. I hope this puts an end to this nonsense.
The part I've underlined explains this clear as day. Vacuum advance is for low engine speed/load. The only reason it's above the throttle is to prevent advance at idle in some cases. I hope this puts an end to this nonsense.
Oh, by the way, a highly modded engine may only be able to pull 5-10" of manifold vac, but that same engine can pull far more venturi vac.
04-10-07, 03:47 PM
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Worry not, Mnsr. Wolff, Smokey Yunick had similar humble beginnings and "gearhead" knowledge as well as Mickey Thompson.
mar3, are you confirming in the public record that the red diagram is incorrect?
I'm trying to get evidence that it is valid. We have, on the one hand, PROOF of which nipple and "theory" is capable of a smooth idle and 25 mpg on a street-ported engine. Now, we need proof of the Red Diagram Theory's effect on mpg.
Have you tried it both ways yourself?
I haven't tried it all...I'm looking for the evidence in the field as any scientist would using the Scientific Method to discern the Truth of a matter or theory.
Has anyone tried it both ways?
Unless they had nothing hooked up at all, I would think the vast majority of the peeps who chimed in that they were going to try the RDT would have been on the other nipple, right? These are the people we need to hear from...my own particular DD, although capable of 19 mpg itself, is in need of serious tuning, so there's no point in using my data since everyone will say, "Yea, but your car ran like crap, you said it yerself..."...
mar3, are you confirming in the public record that the red diagram is incorrect?
I'm trying to get evidence that it is valid. We have, on the one hand, PROOF of which nipple and "theory" is capable of a smooth idle and 25 mpg on a street-ported engine. Now, we need proof of the Red Diagram Theory's effect on mpg.
Have you tried it both ways yourself?
I haven't tried it all...I'm looking for the evidence in the field as any scientist would using the Scientific Method to discern the Truth of a matter or theory.
Has anyone tried it both ways?
Unless they had nothing hooked up at all, I would think the vast majority of the peeps who chimed in that they were going to try the RDT would have been on the other nipple, right? These are the people we need to hear from...my own particular DD, although capable of 19 mpg itself, is in need of serious tuning, so there's no point in using my data since everyone will say, "Yea, but your car ran like crap, you said it yerself..."...
04-10-07, 04:38 PM
#88
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Originally Posted by Rogue_Wulff
Read the parts I highlighted again, and remember, they are your exact words. Then try telling me I am wrong. You just said exactly what I have said since my first post in this thread. No vacuum to the advance at idle, but as soon as you open the throttle, vacuum starts getting pulled.
Oh, by the way, a highly modded engine may only be able to pull 5-10" of manifold vac, but that same engine can pull far more venturi vac.
Oh, by the way, a highly modded engine may only be able to pull 5-10" of manifold vac, but that same engine can pull far more venturi vac.
04-10-07, 04:41 PM
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Originally Posted by djjjr42
Apparently you do since you responded, junior whopper. You have no concept of respect for others, and contrary to what that tiny thing rattling around in that thick skull of yours may be telling you, you're not always right, no one is. If you ran off at the mouth like that around where I come from, you'd be smacked across the head by any elder within earshot - in what would most likely be a futile attempt to knock some sense into you. Grow up already!
Since you're obviously a superb retainer of what you read, here is some suggested reading for you: ""How to Win Friends and Influence People" by Dale Carnegie
You have no concept of respect for others, and contrary to what that tiny thing rattling around in that thick skull of yours may be telling you, you're not always right, no one is. If you ran off at the mouth like that around where I come from, you'd be smacked across the head by any elder within earshot - in what would most likely be a futile attempt to knock some sense into you. Grow up already!Since you're obviously a superb retainer of what you read, here is some suggested reading for you: ""How to Win Friends and Influence People" by Dale Carnegie
04-10-07, 05:41 PM
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Originally Posted by REVHED
What have you contributed to this thread? Show me were I made a personal attack before you crawled out from under your rock. Maybe you should take some of your own advice. Once again, **** off.
If you could pull ur head out of ur own *** for 5 seconds and look objectively at your post immediately after Kentetsu's you might see what I was referring to. Since you are most likely unable to or won't do that I'll be more than happy to point out how it was offensive. 2nd sentence (if you're counting on fingers, that's the one next to ur thumb) when you implied (with caps no less) that he didn't read the WHOLE article and arrive at the same conclusion as Mr. High and Mighty (again, you). What made you assume that he didn't read it all and just arrive at a different conclusion, or perhaps even the same one but just phrased it differently than you? Oh, I know...it's that "I'm never wrong",
attitude you got kicking in there. Then you go on to say things like "The part I've underlined explains this clear as day" and "I hope this puts an end to all this nonsense", which are disguised ways of saying "I think you're too ******* stupid to see it so let me draw a picture" and "I ALMIGHTY HAVE SPOKEN". Who the hell died and made you king? I would have a battle of wits with you boy but I see that you're unarmed so once again, see my signature line and here's to hoping you get laid soon. 
04-10-07, 05:43 PM
#91
ok fellas. this is getting a little out of hand. i have an idea. i volunteer to be the test subject.
here is my cars specs;
85 GSL
stock port 12a
RB header with full exhaust
RB filter set up with foam filter
carter pump with holley FPR set at 2psi
im not too good with the nikki, but it was rebuilt before i bought the car. im kind of sure it needs a little tuning as my idle is kind of rough, but i should still be fine to test this subject.
my rats nest has been removed via the original way, the nipple to the left. i have driven with it this way for about 6 months. i check my MPG EVERY time i fill up. i drive kind of moderately, but i get on t every once in a while. ill be great for this test as i drive the same every day. i drive to work, home, to the gym, back home and back to work. it doesnt really vary much. i will occassionally have an appointment to go to or run to the store. thats about it. there wont be any long distance highway driving to mess up the results.
so, ill finish my tank thats currently in my car and get the MPG. ill post them on here with pics. after that, ill swap to the red way and post results after that tank of gas. ill post pics to prove and verify all results.
do i need to reset the timing when i switch the lines? ill check to verify just to keep everyone happy.
here is my cars specs;
85 GSL
stock port 12a
RB header with full exhaust
RB filter set up with foam filter
carter pump with holley FPR set at 2psi
im not too good with the nikki, but it was rebuilt before i bought the car. im kind of sure it needs a little tuning as my idle is kind of rough, but i should still be fine to test this subject.
my rats nest has been removed via the original way, the nipple to the left. i have driven with it this way for about 6 months. i check my MPG EVERY time i fill up. i drive kind of moderately, but i get on t every once in a while. ill be great for this test as i drive the same every day. i drive to work, home, to the gym, back home and back to work. it doesnt really vary much. i will occassionally have an appointment to go to or run to the store. thats about it. there wont be any long distance highway driving to mess up the results.
so, ill finish my tank thats currently in my car and get the MPG. ill post them on here with pics. after that, ill swap to the red way and post results after that tank of gas. ill post pics to prove and verify all results.
do i need to reset the timing when i switch the lines? ill check to verify just to keep everyone happy.
04-10-07, 05:46 PM
#92
Absolute Power is Awesome
Originally Posted by AaronPhelps
+1.
This guy knows what he is talking about. As much as I hate carburetors and all the stupid things that come with carbs they are pretty easy to understand. As engine load increases more fuel is needed. So its fairly easy to understand that the carb needs to ingest more fuel to maintain the correct air fuel ratios. For the carb to suck in more fuel it needs to draw vacuum.
Personally I would never buy a car without Fuel Injection though!
http://auto.howstuffworks.com/question377.htm
From what I have heard from tuners is that Jeff Hartman's book isn't god's gift and shouldn't be treated so.
This guy knows what he is talking about. As much as I hate carburetors and all the stupid things that come with carbs they are pretty easy to understand. As engine load increases more fuel is needed. So its fairly easy to understand that the carb needs to ingest more fuel to maintain the correct air fuel ratios. For the carb to suck in more fuel it needs to draw vacuum.
Personally I would never buy a car without Fuel Injection though!
http://auto.howstuffworks.com/question377.htm
From what I have heard from tuners is that Jeff Hartman's book isn't god's gift and shouldn't be treated so.
Hartman's book is a good source of information on how the ignition system works. I didn't make any other claims about it. I've shown 3 sources that say the same thing that I am. There's also a link to Paul Yaw's site and a link from someone who didn't know they were supporting what I was saying. That's 5 different places countering Rogue_Wulff and none supporting him.
I hope anyone reading this thread makes their own decision on what to believe.
Originally Posted by AaronPhelps
Education does not make you a car mechanic, tuner, or an engineer for that matter IMO. Only experience, self learning and applying principals are the only way to fully understand engines and how they operate.
04-10-07, 10:23 PM
#93
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Originally Posted by Rogue_Wulff
But I ain't wrong. Using the workshop manual to find the right port is excellent advice, as it backs up what I have been trying to tell you. Even the vacuum diagram under the hood shows where the vac line should be hooked up.
Manifold vacuum drops as the throttle is opened, while venturi vacuum increases as it's opened. Don't take my word on it, though. Use a vacuum guage and test it for yourself.
I don't come on here trying to prove I'm right by backing up what I say with degrees and other stuff that says I be edumacated, instead I stated what every old-school hot rodder has known for years.
The vac advance increases timing under lower RPM's and engine loads by using venturi vacuum, because under those conditions, manifold vacuum is actually decreasing. Why do you think the brake booster has a check valve in it?
Manifold vacuum drops as the throttle is opened, while venturi vacuum increases as it's opened. Don't take my word on it, though. Use a vacuum guage and test it for yourself.
I don't come on here trying to prove I'm right by backing up what I say with degrees and other stuff that says I be edumacated, instead I stated what every old-school hot rodder has known for years.
The vac advance increases timing under lower RPM's and engine loads by using venturi vacuum, because under those conditions, manifold vacuum is actually decreasing. Why do you think the brake booster has a check valve in it?
Take two minutes and Google it for crying out loud! Do a little of your own independent, unfunded, short term investigating. Everywhere you look, you will find the same explanation.
Some people are making excellent arguments here, but they are based on misconceptions. Stop listening to convincing arguments and start thinking for yourselves. Do your homework and come back with your results.
04-11-07, 12:21 AM
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Originally Posted by REVHED
Yes, but as soon as the throttle passes the vacuum port it is exposed to manifold vacuum which then decreases the further you open the throttle. The highest vacuum advance is at very small throttle openings and decreases with load. You have been saying the opposite.
Manifold vacuum is only pulled when the throttle is restricting the flow (closed, or part closed). At wide open throttle, there is almost no manifold vacuum, unless the carb is way too small for the engines needs.
04-11-07, 02:59 AM
#95
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Originally Posted by Rogue_Wulff
Ummmm, no, not quite. When you open the throttle, it is not exposed to manifold vacuum. It is exposed to the vacuum pulled at the base of the venturi, which increases as the airflow increases thru the venturi of the carb. Remember, the venturi's purpose is to increase the velocity of the air as it flows thru the carb. Where the vacuum is pulled from, is below the narrowest part of the venturi, where the velocity is the highest. This higher velocity air can actually pull far higher vacuum than manifold vacuum. It works like a paint gun, in that the airflow thru the gun actually sucks paint out of the cup, and up into the sprayer.
Manifold vacuum is only pulled when the throttle is restricting the flow (closed, or part closed). At wide open throttle, there is almost no manifold vacuum, unless the carb is way too small for the engines needs.
Manifold vacuum is only pulled when the throttle is restricting the flow (closed, or part closed). At wide open throttle, there is almost no manifold vacuum, unless the carb is way too small for the engines needs.
The higher the vacuum signal, the greater the timing advance. High vacuum signals are indicative of low engine loads at a closed or nearly closed throttle position
Last edited by REVHED; 04-11-07 at 03:09 AM.
04-11-07, 03:05 AM
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Originally Posted by djjjr42
I was following this thread because I did the rats next removal and had the vac advance where the tutorial said it was supposed to go. Even though I've just put in the weber dcoe 45 I am interested in the possible application of vacuum advance to my setup as it is not hooked up at the moment. I saw a cocky jerkoff (that would be you) stepping out of line and chose to call him out on it.
If you could pull ur head out of ur own *** for 5 seconds and look objectively at your post immediately after Kentetsu's you might see what I was referring to. Since you are most likely unable to or won't do that I'll be more than happy to point out how it was offensive. 2nd sentence (if you're counting on fingers, that's the one next to ur thumb) when you implied (with caps no less) that he didn't read the WHOLE article and arrive at the same conclusion as Mr. High and Mighty (again, you). What made you assume that he didn't read it all and just arrive at a different conclusion, or perhaps even the same one but just phrased it differently than you? Oh, I know...it's that "I'm never wrong", attitude you got kicking in there. Then you go on to say things like "The part I've underlined explains this clear as day" and "I hope this puts an end to all this nonsense", which are disguised ways of saying "I think you're too ******* stupid to see it so let me draw a picture" and "I ALMIGHTY HAVE SPOKEN". Who the hell died and made you king? I would have a battle of wits with you boy but I see that you're unarmed so once again, see my signature line and here's to hoping you get laid soon.
If you could pull ur head out of ur own *** for 5 seconds and look objectively at your post immediately after Kentetsu's you might see what I was referring to. Since you are most likely unable to or won't do that I'll be more than happy to point out how it was offensive. 2nd sentence (if you're counting on fingers, that's the one next to ur thumb) when you implied (with caps no less) that he didn't read the WHOLE article and arrive at the same conclusion as Mr. High and Mighty (again, you). What made you assume that he didn't read it all and just arrive at a different conclusion, or perhaps even the same one but just phrased it differently than you? Oh, I know...it's that "I'm never wrong",
attitude you got kicking in there. Then you go on to say things like "The part I've underlined explains this clear as day" and "I hope this puts an end to all this nonsense", which are disguised ways of saying "I think you're too ******* stupid to see it so let me draw a picture" and "I ALMIGHTY HAVE SPOKEN". Who the hell died and made you king? I would have a battle of wits with you boy but I see that you're unarmed so once again, see my signature line and here's to hoping you get laid soon. 
04-11-07, 05:45 AM
#97
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Here's the diagram straight out of the 85 FSM. It shows the vacuum port just above the throttle plates. So, as soon as you open the throttle the port is exposed to manifold vacuum. But, even the factory manual must be wrong seeing as it doesnt agree with your view along with the countless other articles, engineers. etc.
04-11-07, 07:46 AM
#98
Lives on the Forum
Even with your diagram, I fail to see how manifold vacuum has anything to do with this. The only vacuum source shown is above the throttle plates, which means it will increase as rpms and throttle opening increase.
You're overcomplicating things by picturing that opening as being exposed by the throttle plates. It is always exposed, but there is not always high vacuum present. As the throttle plates open, the velocity of the air being drawn into the engine becomes the vacuum source. Manifold vacuum has nothing to do with any of this...
Mechanical advance is based strictly on rpms, and not engine load.
Again, a great argument but it is based on misconceptions.
You're overcomplicating things by picturing that opening as being exposed by the throttle plates. It is always exposed, but there is not always high vacuum present. As the throttle plates open, the velocity of the air being drawn into the engine becomes the vacuum source. Manifold vacuum has nothing to do with any of this...
Mechanical advance is based strictly on rpms, and not engine load.
Again, a great argument but it is based on misconceptions.
04-11-07, 07:49 AM
#99
Wonderful thread, I read the whole thing and now I think I understand vacuum advance on my car a little better, thanks for all the excellent contributions. But as one of Mario's "PhD kind of guys" I have to say the the most important thing I learned was why I haven't taken my rat's nest off in the first place.
Maybe when I get older, wiser and retired I'll give the rat's nest removal a try.
Ray
Maybe when I get older, wiser and retired I'll give the rat's nest removal a try.
Ray
04-11-07, 08:29 AM
#100
Absolute Power is Awesome
OK, who's got a pressure gauge (with vacuum)? Take the line from the distributor and go for a drive. It's got to be an impartial member with a stock vacuum system.
Last edited by purple82; 04-11-07 at 08:39 AM.