Idle Speed Motor ***SPLIT from Liner Seals***

[DMCVegas]

Totally off the wall question but we have a vacuum line that runs from the epavp can to the cold start tube then another to the Oil filler from there. Why not a straight line to the intake? it just a vac port isn't it? Wait never mind I think if you plugged those port the Cold star valve would not work well. I guess the let air in to carry the fuel charge down the tube.

BINGO!

As mentioned, that hose from the evap canister is for the purge line. It not only purges the vapors collected whilst the vehicle is parked, but it also prevents excess vapor pressures from building up while the vehicle is running. But that is an entirely different topic there...

I *believe* the reason the oil cap connects to the cold start tube is to facilitate air flow so that the evap system and the cold start valve can both feed their respective vapors down into the intake manifold. Part of the crank case vapors are drawn down that tube to provide an airflow that can push the evap & cold start payloads down into the intake manifold.

It's like if you were sucking on a straw that was in a milk bottle, but the bottle was perfectly sealed at the top around the straw. Without a vent hole to replace the displaced fluid inside of the container, the vacuum you create inside the bottle would pull the fluid up and prevent you from sucking out the milk. Thus you've eliminated the flow of the liquid and can't suck anymore out. BUT, poke a hole in the top to allow for airflow, then suddenly the air rushing in will allow you to suck the rest of the milk out because it will push down on the liquid and force it up the straw.

Thus the small diverted flow of crank case gasses from the oil cap helps carry the gasoline mist from the cold start valve and the carbon canister down into the intake manifold. And of course the reason you wouldn't straight pipe that is so that you don't apply full vacuum directly to the cold start valve or the carbon canisters. Just in case you're also wondering about the gasoline vapors being introduced into the manifold as unmetered fuel, never fear, LAMBDA will tweak the AFR accordingly to fine-tune things so that the engine is unaffected.

P.S. If that oil cap gets too restricted, the crank case pressures will build up enough to purge engine oil through the front main seal. Been there, done that. Overall, if someone else can correct me on any of this, please do. But I can assure you from past experience that you want to leave those hoses in place as intended.

Correct what tried to articulate is that you can know how much air can pass through it is a given position so now you can calculate the amount of fuel needed at that position and develop a way to introduce that fuel The FD and of course now you can determine the best Pressure to send to the FD but you need to compensate for atmospheric conditions so you can't use constant pressure you need to control it, enter the control pressure regulator. Then to fine tune you may need to add a little fuel to get the right air fuel mix FV comes into play there.

Now I know I am gonna get flamed for this but I think would be possible to eliminate the cold start valve by Hi-Jacking the FV just a random thought!
Anyway

No need to reinvent the wheel. All fuel metering is already done by the air flow meter in the mixture chamber, Any and all additional minuscule introductions of un-metered air from the crank case vent have already been accounted for by BOSCH. The fuel map which the engine uses was already predetermined at the factory, and the vacuum lines, vacuum delays, hoses sizes, vacuum curves, fuel flow rates, etc. have all been pre-calculated by BOSCH and are executed mechanically by K-Jetronic. It has all been accounted for, which is why there are so many different part numbers unique to the vehicles which received this fuel injection system. No need to reinvent it.

As for deleting the cold start valve and having the injectors take over it's duties, that can't be done. The mechanical system was never designed to have such a flow rate. Now, EFI injectors are, which is why modern cars don't use choke flaps or cold start valves. They're designed for those massive flow rates during cold starts. In order to accomplish such a task, you've have to graft in a second frequency valve, and then wire it to the CSV's old circuit. Then you'd need hoses, injectors, a fuel distributor, and then a new fuel pump. Because remember, this is mechanical fuel injection which requires hydraulic line pressure to activate the injectors. The wider the injectors open, the more line pressure you need to accomplish that. But even then you cannot know what parts to use until you calculate what the necessary line pressures would be, and then adjust the primary pressure regulator accordingly. Then you'd need to ensure that the warm up regulator's flow rates were acceptable, and have to then also calculate the vacuum activation pressures and delays to get that to work in harmony as well. If you were going down this kind of road, it would honestly be much easier to convert the whole engine to EFI than try and reinvent/reassign the functions of K-Jetronic.

Also, please do not think that I am trying to flame you or anything like that. By all means, please do not hesitate to ask questions. It's how I learned.

[Giamanut]

BINGO!

As mentioned, that hose from the evap canister is for the purge line. It not only purges the vapors collected whilst the vehicle is parked, but it also prevents excess vapor pressures from building up while the vehicle is running. But that is an entirely different topic there...

I *believe* the reason the oil cap connects to the cold start tube is to facilitate air flow so that the evap system and the cold start valve can both feed their respective vapors down into the intake manifold. Part of the crank case vapors are drawn down that tube to provide an airflow that can push the evap & cold start payloads down into the intake manifold.

It's like if you were sucking on a straw that was in a milk bottle, but the bottle was perfectly sealed at the top around the straw. Without a vent hole to replace the displaced fluid inside of the container, the vacuum you create inside the bottle would pull the fluid up and prevent you from sucking out the milk. Thus you've eliminated the flow of the liquid and can't suck anymore out. BUT, poke a hole in the top to allow for airflow, then suddenly the air rushing in will allow you to suck the rest of the milk out because it will push down on the liquid and force it up the straw.

Thus the small diverted flow of crank case gasses from the oil cap helps carry the gasoline mist from the cold start valve and the carbon canister down into the intake manifold. And of course the reason you wouldn't straight pipe that is so that you don't apply full vacuum directly to the cold start valve or the carbon canisters. Just in case you're also wondering about the gasoline vapors being introduced into the manifold as unmetered fuel, never fear, LAMBDA will tweak the AFR accordingly to fine-tune things so that the engine is unaffected.

P.S. If that oil cap gets too restricted, the crank case pressures will build up enough to purge engine oil through the front main seal. Been there, done that. Overall, if someone else can correct me on any of this, please do. But I can assure you from past experience that you want to leave those hoses in place as intended.





No need to reinvent the wheel. All fuel metering is already done by the air flow meter in the mixture chamber, Any and all additional minuscule introductions of un-metered air from the crank case vent have already been accounted for by BOSCH. The fuel map which the engine uses was already predetermined at the factory, and the vacuum lines, vacuum delays, hoses sizes, vacuum curves, fuel flow rates, etc. have all been pre-calculated by BOSCH and are executed mechanically by K-Jetronic. It has all been accounted for, which is why there are so many different part numbers unique to the vehicles which received this fuel injection system. No need to reinvent it.

As for deleting the cold start valve and having the injectors take over it's duties, that can't be done. The mechanical system was never designed to have such a flow rate. Now, EFI injectors are, which is why modern cars don't use choke flaps or cold start valves. They're designed for those massive flow rates during cold starts. In order to accomplish such a task, you've have to graft in a second frequency valve, and then wire it to the CSV's old circuit. Then you'd need hoses, injectors, a fuel distributor, and then a new fuel pump. Because remember, this is mechanical fuel injection which requires hydraulic line pressure to activate the injectors. The wider the injectors open, the more line pressure you need to accomplish that. But even then you cannot know what parts to use until you calculate what the necessary line pressures would be, and then adjust the primary pressure regulator accordingly. Then you'd need to ensure that the warm up regulator's flow rates were acceptable, and have to then also calculate the vacuum activation pressures and delays to get that to work in harmony as well. If you were going down this kind of road, it would honestly be much easier to convert the whole engine to EFI than try and reinvent/reassign the functions of K-Jetronic.

Also, please do not think that I am trying to flame you or anything like that. By all means, please do not hesitate to ask questions. It's how I learned.

All true but I am kind of the mad scientist type. JK about the flame part.

[Ron]

BINGO!

As mentioned, that hose from the evap canister is for the purge line. It not only purges the vapors collected whilst the vehicle is parked, but it also prevents excess vapor pressures from building up while the vehicle is running. But that is an entirely different topic there...

I *believe* the reason the oil cap connects to the cold start tube is to facilitate air flow so that the evap system and the cold start valve can both feed their respective vapors down into the intake manifold. Part of the crank case vapors are drawn down that tube to provide an airflow that can push the evap & cold start payloads down into the intake manifold.

It's like if you were sucking on a straw that was in a milk bottle, but the bottle was perfectly sealed at the top around the straw. Without a vent hole to replace the displaced fluid inside of the container, the vacuum you create inside the bottle would pull the fluid up and prevent you from sucking out the milk. Thus you've eliminated the flow of the liquid and can't suck anymore out. BUT, poke a hole in the top to allow for airflow, then suddenly the air rushing in will allow you to suck the rest of the milk out because it will push down on the liquid and force it up the straw.

Thus the small diverted flow of crank case gasses from the oil cap helps carry the gasoline mist from the cold start valve and the carbon canister down into the intake manifold. And of course the reason you wouldn't straight pipe that is so that you don't apply full vacuum directly to the cold start valve or the carbon canisters. Just in case you're also wondering about the gasoline vapors being introduced into the manifold as unmetered fuel, never fear, LAMBDA will tweak the AFR accordingly to fine-tune things so that the engine is unaffected.

P.S. If that oil cap gets too restricted, the crank case pressures will build up enough to purge engine oil through the front main seal. Been there, done that. Overall, if someone else can correct me on any of this, please do. But I can assure you from past experience that you want to leave those hoses in place as intended.

FWIW- I think you meant "was parked".

=======

What about the 3rd hole on the other side??

I believe the ISM will supply plenty of airflow to the cold start tube for the CSV, especially if you keep your foot off of the pedal...*
Excess crankcase vapors will go through the oil fill cap and then to the air cleaner and/or the cold start tube while the engine is running. It has to pass the tiny metering hole and it's dumped during off idle anyway, and as you mentioned, nothing the Lambda System couldn't compensate for.

*This made me think about the many times I have heard (and said!) that it makes no difference if you pump or hold it part throttle when cranking... Now I'm thinking the more the plates are shut, the greater the amount of air flow you will have to deliver the CSV's fuel, I.E., keep you foot off the pedal!
This is why I love decent conversation...

As far as flaming goes, who can say getting their tail feathers singed hasn't saved the thing they are attached to a few times?

P.S. I could be wrong here --- Light me up!

[DMCVegas]

FWIW- I think you meant "was parked".

=======

What about the 3rd hole on the other side??

I believe the ISM will supply plenty of airflow to the cold start tube for the CSV, especially if you keep your foot off of the pedal...*
Excess crankcase vapors will go through the oil fill cap and then to the air cleaner and/or the cold start tube while the engine is running. It has to pass the tiny metering hole and it's dumped during off idle anyway, and as you mentioned, nothing the Lambda System couldn't compensate for.

*This made me think about the many times I have heard (and said!) that it makes no difference if you pump or hold it part throttle when cranking... Now I'm thinking the more the plates are shut, the greater the amount of air flow you will have to deliver the CSV's fuel, I.E., keep you foot off the pedal!
This is why I love decent conversation...

As far as flaming goes, who can say getting their tail feathers singed hasn't saved the thing they are attached to a few times?

P.S. I could be wrong here --- Light me up!

No man, I love conversations like this. It's fun to talk of theories, and likewise just discover new things. I've been wrong before about some things, and I'll be wrong again, but I learn and enjoy the whole process. Particularly about just being nice on the internet. An exceedingly rarer opportunity nowadays.

Which 3rd hole are you talking about?


I don't think that during a cranking condition the ISM passes through as much airflow by itself as we think the engine is getting. I don't know the specific CFM values for this, but I'll lay it down like this as a formula:

• x=ISM CFM
• y=Throttle plates CFM
• z= idle screw CFM
• n=Final CFM delivered to the engine.

So lets say that the ISM when fully open delivers x value of CFM. Once the engine is running at proper idle speed, that is when the ISM can then modify the flow rate. Thus the formula is z-x=n because the ISM is subtracting airflow from the engine.

But dig this: Due to the low RPMs present during engine cranking (200±?) until engine speed goes above 775 ± 50 RPM range, then the ISM will not deviate. Thus during engine cranking, the formula becomes x+y=n because the Idle Speed Circuit is using the metric of engine RPM via the pulse signal rather than CFM via an MAF or TPS sensor like an EFI engine has. So when you hold down the gas pedal during cranking, it absolutely makes a difference because the Idle Speed Circuit has no idea what you're doing, and is totally out of range. Thus the engine gets fed a whole lot more air and fuel to start up since as n increases, so doe the fuel flow to the injectors.

I can also tell you as well that it absolutely makes a difference when cranking when you've got other problems with the engine. I once decided to try and "upgrade" my ignition coil with a POS Accel ignition coil. The damn car would not start unless I held down the gas pedal while cranking. Also had problems with my resting fuel pressures thanks to a blast of ethanol ruining my accumulator and eventually the O-rings in the PPR. Holding down the gas pedal during cranking and hard starting helps maintain airflow against the metering plate to keep the plunger pressed in to build line pressures back up quickly.

[Ron]

Which 3rd hole are you talking about?

The one going from the ISM to the Cold Start tube.

(Reading the other now...Is it getting warm in here to you? ;-)

[Giamanut]

The one going from the ISM to the Cold Start tube.

(Reading the other now...Is it getting warm in here to you? ;-)

I can't believe this thread is still going, I think I was just being random in another thread and it got split. Good stuff though!

[Ron]

Robert, to get on the same page- For Z= Idle screw CFM, you're talking the brass bypass screw that is shared by both banks. And when shut no air passes it, or the butterflies when at idle. Correct?
If so, Z-X=N would always be negative...
I'm thinking, it shut, at idle, all air goes into the intake, past the metering plate, out through the Pipe of Agony (Aux 102503), through the ISM, through the Cold Start Tube (Aux 102374), back in, and into the combustion chamber. Lots of airflow to carry the CSV spray.

Or do we need to back up?

[Ron]

I can't believe this thread is still going, I think I was just being random in another thread and it got split. Good stuff though!

+1!

I knew the conversation would take on a life of its own and split it, but who would of thought...

All I can say is, COOL!

[DMCVegas]

Robert, to get on the same page- For Z= Idle screw CFM, you're talking the brass bypass screw that is shared by both banks. And when shut no air passes it, or the butterflies when at idle. Correct?
If so, Z-X=N would always be negative...
I'm thinking, it shut, at idle, all air goes into the intake, past the metering plate, out through the Pipe of Agony (Aux 102503), through the ISM, through the Cold Start Tube (Aux 102374), back in, and into the combustion chamber. Lots of airflow to carry the CSV spray.

Or do we need to back up?

No, you're absolutely right. Both on the function, as well as the formula being incorrect.

I was counting upon the ISM subtracting CFM from it's metering due to the brass screws being opened. Which is true, but still it's still an addition. The values of the variables change, not the operations of the formula.

So let's recap the legend, add to it, and explain the functions.

• x=ISM CFM
• y=Throttle plates CFM
• z= Idle screw CFM (including a sub operation of ratios b=left cylinder bank, c-right cylinder bank)
• n=Final CFM of metered delivered to the engine.
• f=Metered fuel delivery
• v=Vacuum leak
• Σ=Final AFR

For for the sake of simplicity, we'll break this down into the individual sub operations first. Let's go back and start with that initial brass screws vs. ISM formula. I was wrong before. What it should be is x+z=n. I'll stick with nice large, whole numbers right now, but let us say for instance that at idle speed the engine requires 20CFM of air to operate. The formula then looks like this: x+z=20. If the brass screws are fully closed, the value of z should be zero, so the equation becomes 20+0=20. But lets say that the screws are in fact opened a bit to allow for a cushion, and we allow a modest 6CFM though. The value of n still has not changed as that is our intended value we wish to obtain, but z becomes 6. So now our equation becomes x+6=20. To solve for x we know that the value is now 14, thus the equation changes to 14+6=20. The decrease in the first value of x is indicative of the ISM reducing it's air flow in order to compensate for the screws being opened.

If by chance we had the throttle plates sticking, we would simply insert y into that equation. Which *technically* it should be there anyway, and it's value should be 0 by default in an idle condition. But if not, just subtract it's value from x like we did prior to acquire it's value. IF by chance the throttle plates are too far open and the CFM exceeds the default idle value, then we're just exceeding 775±50 with the result of a fast idle condition due to stuck throttle plates. Example: 0+0+40=40 using only the ISM, or with those screws opened as per our previous scenario: 0+6+40=46.

Now let's talk about those idle speed screws. If we crack open that initial screw to allow for the aforementioned 6CFM through to the two remaining screws, we have to ensure that the screws are equally opened to flow an exact 3CFM each in order to properly balance each cylinder bank to achieve an equal AFR across all combustion chambers. Otherwise we could be imbalanced anywhere from 0:6/6:0 on the ratios between each cylinder bank. The connecting tube between the 90° manifold tubes on the B27F 2.7L PRV allowed for automatic equalization between the two banks using ΔP. The leaner side could automatically siphon off the additional CFMs from the opposing bank to naturally balance both out. The first idle screw's CFM is directly proportional to the value of z. The only thing that changes is the ratio between b & c that feeds the cylinder banks. z=b/c if I'm not mistaken. Opening one, or both of the remaining screws for the individual banks without opening the first one that feeds both has no direct impact upon anything. With unbalanced cylinder banks, one bank would be more sooty than the other, which that one would burn much hotter. The result would be fowled and burned plugs, potential engine damage, poor economy, and the fun enigmatic problem of puking both excessive hydrocarbons as well and NO_x!

So in the end, we should have a formula that looks some thing like this:

(x+y+z=n)f+v=Σ

Now this is the fun part; we're only talking about air flow here. As you can already assume, the value of v should always equal zero! If it doesn't, then we've got some huge problems. On a purely mechanical system we have that unbalanced cylinder bank issue. But once we through LAMBDA into the mix...

f is influenced by many factors and actually has it's own separate formula that gets calculated first to determine it's final value before it is in turn calculated into this one. In the purely mechanical system we have the CSV to intervene during low temps, as well as the WUR...which also affects AFR during hard accelerations when significant engine vacuum is present. But LAMBDA also apes those values, as well as fine-tunes the AFR for optimal efficiently beyond what K-Jetronic itself is able to do alone. That of course hearkens back to the problem of surge idling. LAMBDA is fighting to control the AFR by adjusting fuel flow rates while unmetered air from a vacuum leak influenced by the constantly changing fuel flow rates keeps fighting those corrective attempts by changing engine speeds and sabotaging the AFR.

Two independent closed loop systems generating separate mathematical formulas that inadvertently become at war with one another. Modern cars with fully integrated PCMs would see this problem, go into a default open loop cycle choosing a stabilized condition over an optimal operating one,then just flash a Check Engine light and call it a day. But not these old modular systems.

I know it's intimidating, but it's really not. Just make sure the systems are running as intended and you won't have any problems. This is why I say that switching over to EFI if you're looking to radically change the system is a far better option. You just have to let Tuner Studio perform all of these calculations to achieve the optimal fuel map you want to generate.

It's also why anytime someone tells you, "My car runs so much better once I disconnected the LAMBDA system!" never actually solved anything. They just hit a proverbial mute button and never really fixed anything.

[Ron]

COOL!

Going with the previous assumption that the "initial screw" being shut means z=0 (I believe that is the case, but not 100% sure), I'd suggest the following:
Change z=b/c to z=b+c
Change (x+y+z=n)f+v=Σ to ((x+y+z=n)+v)/f=Σ

And, if we're going to delve deeper, being VERY picky:
Include the time duration (per minute) when defining f and v , so they will properly cancel out in the calculations.
Σ should be simply AFR (or A/F, A:F, for convention]

Not that the changes would affect your comments/conclusions -- I follow you and agree 100%! (Not intimidating...flows right along ;-)

Lots of analogies for "the war": K-Jet Storm...mechanical section brutally bombing the battlefield, in preparation; IAC's ECU commanding the troops at the front; and don't forget Lambda's special ops... There MUST be control conflict's, lol. ...It would be fun to discuss in person, but I hate typing (victim of co-ed PE v/s Typing class scheduling ;-) and OT&OTT.

FWIW: (Cut, pasted, and butchered -- Use at own risk ;-)
FlowShut.jpg