My understanding of the combustion engine, is that the vacuum is created by the thermal dynamics of the engine. From my understanding the timing is what controls where the heat is in the motor. This affects the cacuum being pulled through the Venturi.

On a Holley carburetor all functions except for the Excelerator pump are vacuum operated. The Excelerator pump is controlled mechanically with the throttle linkage. There are three variables to Excelerator pump, the diaphragm, the linkage Cam and the squirters.

Suck, squeeze, bang, blow.

Vacuum is created on the initial stroke which fills the cylinders. The up stroke compresses the air/fuel mixture. Spark ignites the mixture which forces the piston down or the power stroke, then final stroke back up is to exhaust the gases and empty the cylinder to begin again.

Poor choice of words on my part. Should've said, vacuum strength can being manipulated with timing. Without overthinking it, I believe this is because of the thermal aspect. Am I wrong in theory?

I am pretty keen on the four cycles btw, but still appreciate your knowledge.

Cam timing yes. The reason you hear "big" cams having a lopey idle is they are struggling to stay running due to valve overlap. You have both valves open at the same time, but not fully, and vacuum quickly goes away. This is why some radical cars need to run a vacuum pump.

Temp of course will affect it as well, but cam timing is the big determining factor.

God damn gubernment.  Just did my taxes and am NOT happy.  

 

 

 

 

And J, you can get by with much cheaper knives. I bought exclusively based on fit. The MAC is cheaper. There is a price point worth stepping into though. Below that restaurant depot knives win.

What would you consider that price point?

Keep in mind I am a huge fan of Cutco, and Wustoff (spelling??) in the past. I won't be buying them for a few years unless something odd changes.

I still hate that buying is cheaper than renting down here,

J

Wustof. I dated a girl whose mom was the head of sales at the time, i believe she was promoted since then but she gave me a 17cm knife... LOVE that knife.

That is a garlic knife. Nearly useless size...

With a little skill you can use a 28-30cm knife for the same tasks.

For what i, and her husband (a gourmet chef) use that size knife for, it's more that enough of a knife to cut what we (usually) make. Seems pretty presumptuous to assume we are carving turkeys or slicing a ham with that tool. Thats just the knife we feel most comfortable using for most of our projects.

 

Show me a gourmet chef that uses a 17cm knife as his primary knife and I'll show you a really shitty chef.  It is a super inefficient size.  Yes I have one.  Global in fact.  Nice blade, but I use it for cutting open celophane and other packaging that I don't want to dull a knife that actually has some use in the kitchen.

 

I will use something that long for coring strawberries and such if that is my ONLY task, but otherwise I'll reach for a real knife.

Curious at what rpm you are experiencing the issue to J.

 

My problem now is that 1) I've never adjusted anything beyond the choke and idle on a carb, and 2) I've read Banish's book on tuning once (almost 2 years ago now, lol) and think of the myriad of ways you can adjust whatever with fuel injection and more importantly what you can log.  Of course this makes me want the equivalent even more on my sled than my car.  A 2 stroke can gain a ton of pull from having optimized temperature injector cycles based on rpm, load, & temperature (air/engine).

 

For some reason the OE's are having trouble keeping them alive under hard use though in particular on sleds.  Emissions and lubrication are generally what is blamed, but if everything was optimized AND measured with a better controller I don't think that would be the case.  

God damn gubernment.  Just did my taxes and am NOT happy.

All of my tax monies go to folks on welfare..I feel your pain!

I am jetted safe.

 

ie, I can ride at 20F one day and then at -30F the next without blowing up.  Pretty much means it runs rich as shit when its warm and gets absolute horsehit gas mileage.  (read <7mpg, less than 4 in really a lot of correspondingly wet snow.  I've also seen nearly 14mpg on but as cold days.

I like to do some steady pulls at WOT early on in a cold day to make sure the EGT's stay in check.  Don't really think that is a good mechanism, but I set those conservative as well and say fuck it with needle changes all the time.  Takes about an hour to pull the carbs and put them back on.  Some dudes do them in the sled, but I guarantee I'll drop some brass something or other and have to pull the motor to get it back.

Although at this point I think I can pull the whole motor in 45min.

Curiosity is one of my strongest motives.

Mine is pussy and cola.

And J, you can get by with much cheaper knives. I bought exclusively based on fit. The MAC is cheaper. There is a price point worth stepping into though. Below that restaurant depot knives win.

What would you consider that price point?

Keep in mind I am a huge fan of Cutco, and Wustoff (spelling??) in the past. I won't be buying them for a few years unless something odd changes.

I still hate that buying is cheaper than renting down here,

J

Wustof. I dated a girl whose mom was the head of sales at the time, i believe she was promoted since then but she gave me a 17cm knife... LOVE that knife.

That is a garlic knife. Nearly useless size...

With a little skill you can use a 28-30cm knife for the same tasks.

For what i, and her husband (a gourmet chef) use that size knife for, it's more that enough of a knife to cut what we (usually) make. Seems pretty presumptuous to assume we are carving turkeys or slicing a ham with that tool. Thats just the knife we feel most comfortable using for most of our projects.

Lol

The same argument could be used that you presuming a 28cm knife is good for carving.

Do you even circularly logic bro?

Call the guy a Dick for pissing in your chereos, but your logic bomb was horrendous.

I'm going to be up processing photos tonight... Then meet my new boss tomorrow.

Bleh.

 

Curiosity is one of my strongest motives.

Mine is pussy and cola.

 

Isn't that the same thing?

New Boss?

God damn gubernment.  Just did my taxes and am NOT happy.  

 

 

Doing mine tonight.  

God damn gubernment.  Just did my taxes and am NOT happy.

 

 

Doing mine tonight.

I am only happy because I paid in so little. I also refused unemployment, because up until I decided to go back to school, I was job hunting. I also turned down some jobs due to shit pay for insane amounts of work or travel.

J

I'm going to be up processing photos tonight... Then meet my new boss tomorrow.

Bleh.

Good subject matter?

New boss?

J

Your taco meat needs pretty much the exact same love as your chili, just slightly different quantities.

Do you have a good taco recipe?

J

My understanding of the combustion engine, is that the vacuum is created by the thermal dynamics of the engine. From my understanding the timing is what controls where the heat is in the motor. This affects the cacuum being pulled through the Venturi.

On a Holley carburetor all functions except for the Excelerator pump are vacuum operated. The Excelerator pump is controlled mechanically with the throttle linkage. There are three variables to Excelerator pump, the diaphragm, the linkage Cam and the squirters.

Suck, squeeze, bang, blow.

Vacuum is created on the initial stroke which fills the cylinders. The up stroke compresses the air/fuel mixture. Spark ignites the mixture which forces the piston down or the power stroke, then final stroke back up is to exhaust the gases and empty the cylinder to begin again.

Poor choice of words on my part. Should've said, vacuum strength can being manipulated with timing. Without overthinking it, I believe this is because of the thermal aspect. Am I wrong in theory?

I am pretty keen on the four cycles btw, but still appreciate your knowledge.

Cam timing yes. The reason you hear "big" cams having a lopey idle is they are struggling to stay running due to valve overlap. You have both valves open at the same time, but not fully, and vacuum quickly ,goes away. This is why some radical cars need to run a vacuum pump.

Temp of course will affect it as well, but cam timing is the big determining factor.

Yes it has a very lumpy cam. Did not realize both valves are opening at the same time, big clue. Unfortunately I do not know the cam specs.

I started with the timing at 12 degrees before top dead center at idle (factory spec), and it had hard start and was sluggish. Moved the timing to 18 BTDC, and was better, now at 28 BTDC at idle and starts good, and runs like a rapped ape at higher rpms. I changed the mechanical to only advance 8 degrees and all in by 2000 rpms. So idle is 28 and advanced total timing is 36 degrees. Did I get carried away with the idle timing? What benifit does a race car get from locking the timing out at 36, with no advance? Can the cam be clocked when installed, throwing me off?

Ambient temp could play into it. I started setting everything up in the winter. That's another factor I forgot.

New Boss?

Mine is moving to the St Luis market

:-(

I'm going to be up processing photos tonight... Then meet my new boss tomorrow.

Bleh.

Good subject matter?

New boss?

J

It was my old boss going away party.

And I didn't have the ISO high enough.

Grain>nothing in focus.

I couldn't get the settings right in for auto I SO and I got greedy.

Had to shoot way too much at 1.2.

It was so low light...

Curious at what rpm you are experiencing the issue to J.

 

My problem now is that 1) I've never adjusted anything beyond the choke and idle on a carb, and 2) I've read Banish's book on tuning once (almost 2 years ago now, lol) and think of the myriad of ways you can adjust whatever with fuel injection and more importantly what you can log.  Of course this makes me want the equivalent even more on my sled than my car.  A 2 stroke can gain a ton of pull from having optimized temperature injector cycles based on rpm, load, & temperature (air/engine).

 

For some reason the OE's are having trouble keeping them alive under hard use though in particular on sleds.  Emissions and lubrication are generally what is blamed, but if everything was optimized AND measured with a better controller I don't think that would be the case.

Not really an at rpm, just when I gun it. Collates with the vacuum dropping from 8-12 to 1 at best on the gauge. Then the vacuum Rockets back up and the car takes off. Yes the holley has a retarded amount adjustment. The Excelerator pump works off the mechanical linkage, so I would think it would fill the void, once set correctly.

I only adjust one thing and then test drive. I bumped up the squirter nozzle, so more fuel sooner. This should be correct based on the power to weight ratio of the car, and tall axle gear ratio. The vacuum still dropped the same but, was a lot less hesitation. Then I tighten down the carburetor more to the manifold, as I suspected I had over tightened, and got a severe vacuum leak. Then I pulled the carburetor, and cleaned the mounting surfaces, and checked the gasket. My torque wrench does not go low enough, so just tightened less than before. Also added washers, don't recall why hadn't added them before. Think I had a slight vacuum leak that I solved. Vacuum still drops to zero when I punch it parked in the garage. And was too late for a test drive, so no test under load yet.

So recap, fixed a vacuum leak, and added more fuel sooner via mechanical. Didn't get a test drive yet.

If I can't get it in the morning, I will use my phone a friend to call my step brother who is a mechanic.

Jared

Possible the fuel pump isn't wucking enough fuel on demand? Taking a sexond or two to catch up to the request for more fuel?

J

This is very possible J. Ideally the Holley would have a 3/8 fuel line and electric fuel pump. I replaced the factory 5/16 before I realized this. I have a fuel gauge installed out the carburetor, which reads correctly at 7 lbs. The car runs great once it is through the hesitation though, and screams when you punch it on the highway!!

I have the correct electric fuel pump, and may have to replace the line again to 3/8.

I think I about have the holley carburetor figured out. I have the idle circuit dialed, I have the transfer slot circuit dialed, and appropriate size jets and power valve.

The vacuum drops to almost 0 when I punch it. I would say there is more likely hesitation than a bog. I believe I should install a larger Excelerator pump nozzle, to introduce more fuel quicker.

Ryan or anybody else have input on this?

Stock cam?

Does it fall instantly, or gradually, or at high rpm?

It has a very lumpy cam. The fall is instant when you try to get into it.

J - you aren't hearing any knock are you?

I am not following the jump from Temp to Vacuum.

From what I know, the ideal gas law states. PV=nRT

Therefore more cylinder pressure = higher temp. You can surely adjust your pressure with spark timing and along with it pressure.

As for vacuum, it is created by the piston moving up and down. The carb restricts flow of air causing there to be vacuum. In a completely efficient engine the rate of flow of air would be the overall displacement of the engine multiplied by the number of strokes it takes during that time. The only time then you should have "positive" vacuum is when you are not delivering that much air via some restriction. Obviously at idle you will have more since the throttle/carb is nearly closed.

I see that as efficiency, so on one aspect less heat = more efficiency and more efficiency has more capability to "suck" air but I am having a problem connecting the two.

I am far from a guru on anything engines in the cause and effect realm, but something I'd like to learn more about.

No knocking sounds.

More timing=more heat=more power? Not looking for efficiency, but more POWER!

I have a 650 cfm carb, the engine is a 289ci. The reason I'm not asking the mustang forum is they will just tell me carb is to big. I disagree with them for my setup. Might need to find a racing forum.

Install a wideband

 

Get your cheap wideband controllers here: 

http://www.14point7.com/

 

Found them by accident, they even have an open source wideband controller.