Carburetor EGR port question

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The explanation is in the post you're responding to.

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Simpson wrote:

I don't know that particular carb, but have seen that kind of failure before. When I saw it it was a gasket in wrong or the wrong one in so a notch in the base plate was covered when it was supposed to be open.
The other times I have seen the base plate in upside down. There are notches in some that need to be on the carb side, not the manifold side and if folks don't know this, the plate can be in wrong.
I would figure the port you are using was blocked or it would have one or the other types of vacuum.
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos: http://mikeromainjeeptrips.shutterfly.com
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Mike Romain wrote:

Could this 'base plate' be a one inch aluminum spacer with a single manifold vacuum port? Or are you referring to the actual throttle portion of the carb? That would be kind of hard to put in upside down. In any case, as in my reply to MasterBlaster, I suspect a leak in the canister purge line, which enters the carb just above the closed throttle plates, same as the EGR port.

It's brand new, straight from the Holley factory, after sitting on some shelf for about 20 years or more.

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Simpson wrote:

Yes it could. Sometimes the kits come with multiple types of base gaskets with different holes or slots.
Or are you referring to the actual throttle

There is an easy test for that though I don't think it can be the trouble unless you were measuring the vacuum downstream vs at the carb nipple, just pinch the line closed.

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Mike Romain wrote:

Mike, I solved the problem. See my detailed reply to BigIronRam in this thread.
Thanks, for the help. You were on the right track as far as the port probably being blocked goes. Whatever the reason, it just wasn't developing EGR vacuum characteristics and would not even make it to 2 pounds at 2,000rpm.
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Simpson wrote:

Your response was to ignore the advice given. The suggestion was made that the EGR was designed to run off the very low vacuum port. From there it goes to a vacuum amplifier which uses the low vacuum signal to control the EGR using vacuum coming from intake manifold. If I understood your response - you ignored that advice and hooked it up in a different way.
    The low vacuum plus amplifier may or may not be how your engine vacuum lines are supposed to be configured. But it does sound like the carb was designed to work with that configuration. Is there an under-the-hood vacuum line diagram?
-jim

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jim wrote:

My response was to investigate what a vacuum amplifier was and then to determine that the EGR system on the 87 Dakota V6 did not incorporate one.

And that is *all* that it was... a suggestion.
that

But not in this case.
I hooked up the EGR valve the way it was hooked up stock. There is no vacuum amplifier. The vacuum hose from the EGR port on the carb goes directly to the CVSCC (coolant vacuum switch cold closed) which prevents the EGR system from kicking in when the engine is closed. The vacuum line then goes directly to the EGR valve.

You're starting to repeat yourself.

I hooked it up in such a way that passed the smog inspection.

Now you're getting it.

It may be that the *carb* was designed to work that way, but the EGR system on my truck was designed to to work without a vacuum amplifier.
I made it clear in the thread that the mixture control solenoid for the original, stock carb can longer be purchased and that the carb I am working with is the non-feedback version of that carb. I also made it clear in my last post to Mike Romain that I modified the carb to work like the original as far as the EGR function goes and that the mod was successful.

Of course there is. There is also one in the shop service manual.

Are you the hall monitor for this group? Do you go around busting people for not following the advice of others to the letter? If so, you have too much time on your hands.

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Simpson wrote:

Your reply made no mention of that. That is you completely ignored the advice and didn't explain why you ignored it until now. You didn't even give a hint that you comprehended what was said.

Maybe - Maybe not. How the hell would I know.

When people fail to indicate they understand the advice the tendency is to repeat it. No??

Then why are you trying to do additional modification? You've made a half dozen posting since you passed the test asking for help with modifications. What's that all about?

You still don't "get" that when you fail to provide adequate information the reader has no choice but to guess what the actual facts are.

But given that you now have a different carburetor the range of vacuum coming from the EGR port will not be exactly the same as the original and it is possible that the way it was hooked up in connection with a vacuum amplifier might give you better performance. The EGR affects the mixture that the carb delivers. If the flow thru the EGR is not in synch with the carb mixture controls you may not be getting optimum mixture at all the different possible engine loads and RPMs. So the original advice to hook the EGR thru a vacuum amplifier still may have produced better results than you got.

You implied that you replied to the advice given. You did not reply to that advice you ignored it completely. You didn't even give the slightest hint that you understood what the advice was. Since my crystal ball is in the shop for repairs this week - I thought maybe you didn't understand the advice and perhaps maybe you would want to be aware of that. But apparently you're not interested.
-jim

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wrote:

He has already stated that with the replacement carb installed the HC emissions are barely within limits.

He has already explained that he reconfigured the vacuum slots to match the old carb. And what's to say that his current EGR valve is calibrated to be used on a system that employs a vacuum amplifier? Where does it end? It's a 21 year old truck.

Actually, no. When you say mixture associated with carburetor (or any fuel metering device), It's assumed you mean the air/fuel ratio. Exhaust gas is neither air nor fuel, it's supposed to be inert. EGR doesn't alter air/fuel mixture, it displaces it.

He's not getting optimum mixture because he's using a lean burn carb in a non lean burn application. But what do I know, I only worked on them every day in a dealership in the late 70s.

And if there's an underhood inspection involved with the emissions test, he gets an automatic fail.
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aarcuda69062 wrote:

The 15 mph test was barely within limits. The other was well within limits.

Not a very difficult thing to check if you have a vacuum gauge.

Actually yes.

How is "displace" different than "alter" ? Do you think the engine is concerned with semantics?

You are revealing how little you know. Besides his engine is new enough to be beyond some of the stupidity of the 70's lean burn applications. The reality is the EGR will affect mixture on a carb because it does affect airflow. Even some of your statements seem to be claiming that it was not too lean before the EGR was hooked up but now after it is.     Now if the EGR is the only thing different from the failed test to the passed one (a doubtful theory in itself). He may simply not need as much EGR at 15 mph than he is getting with his current setup. That might entirely account for the higher HC. The carb was designed to work with an EGR that followed venturi vacuum - I'm not saying it will work better if configured like that but it does seem likely. Given that he doesn't have a standard setup. The only way to find out is to experiment.

He will fail for not having the OEM carb?
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wrote:

And he wasn't satisfied with "barely." I wouldn't be either. The frickin cut points are so loose that if it's not below 50% of cut point, something isn't right.

Okay, publish the vacuum specs for both types of EGR systems. That ought to help him considerably.

It's the twenty first century Jim, the old beliefs that you're subscribing to here have been long refuted.

Main Entry: dis?place Pronunciation: \(?)dis-?pla?s, di-?spla?s\ Function: transitive verb 1 a: to remove from the usual or proper place; specifically : to expel or force to flee from home or homeland <displaced persons> b: to remove from an office, status, or job cobsolete : to drive out : banish 2 a: to move physically out of position <a floating object displaces water> b: to take the place of (as in a chemical reaction) : supplant
Main Entry: al?ter Pronunciation: \?o?l-t?r\ Function: verb transitive verb 1 : to make different without changing into something else 2 : castrate, spay intransitive verb : to become different
> Do you think the engine is concerned with semantics?
Do you think a boat floating in water makes the water different?
Your wet sidewalks cause rain fan club membership card is in the mail.

Really? The results of his third test show differently.

Couldn't figure out how to fix them, 'eh?

Not even close to plausible.

Cite?
Gee, I'm pretty sure there was a carburetor change in there.

It might if the CO weren't so low. I will admit to not having fully realized that he connected the EGR to the vacuum fitting for the spark transducer which well would cause an over EGR condition. Should have run like crap at cruise though...

And he has since modified the carb and tested it configured with ported vacuum with positive results.

True that.

Not necessarily due to there no longer being any service parts.
I don't know what your problem is, Simpson has demonstrated amazing ingenuity, intuition and desire to learn and understand.
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aarcuda69062 wrote:

But the point was that only under certain load and RPM it was well within limits.

The reason they introduced the vacuum amplifier was not because they changed the way the EGR worked but because they changed the location that the vacuum signal that operated the EGR came from. The EGR valve for his vehicle probably was the same for a 10 or 15 year period. During that time they had all sorts of different carbs and vacuum line configurations.     The signal from venturi vacuum was to weak to operate an EGR valve in a reliable way so it needed to be amplified and then the same old EGR could be used. The reason it was tied to the weaker venturi vacuum was that would allow for more accurate metering of air and fuel under a wider range of operating conditions. The feedback carberator wouldn't need that because the feedback system itself would be able to compensate for any changes in airflow that affected the air/fuel mixture.     As for the Chrysler lean burn crap - that was easy to fix. What was so incredibly stupid was it took Chrysler engineers 10 years and near bankruptcy to figure out how to fix it.
-jim

Air fuel mixture is controlled by the flow

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wrote:

No one drives at only 15 and 25 miles per hour. There is no data for other speed ranges so, the word "only" is a bit disingenuous.

It couldn't possibly be. His was the first year of production for both the chassis and the engine, the year following his was throttle body fuel injection and used a SMEC controlled pulse width modulated solenoid and back pressure transducer to control the EGR.

No they didn't. One year only. 4 cylinder or six cylinder.

That was Chrysler's way of doing it. That's all that can be said.

Love to hear about it some time. Hope you research it better then your claims about the 10-15 year spread where they used that exact EGR valve/scheme on a vehicle that was produced in that configuration for only one year.

That's the way innovation is.
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aarcuda69062 wrote:

For someone who claims to know something that is as good as saying you don't. I didn't say chrysler used the same engines for all those years I said the EGR's were all pretty much the same in that era. The means of controlling the vacuum, which determined how much exhaust gas was delivered and when it was delivered is what changed depending on make, model and year.     That was the purpose of vacuum hose configurations, vacuum amplifiers or transducers and different vacuum ports. The difference in the valve itself had more to do with how they fit on the engine rather than how they behaved.
    At any rate EGR clearly has a huge effect on NOX emissions and does completely change the way air and fuel burn inside an engine. That mains the entire way the engine is tuned needs to change to accompany the changes that EGR creates. For the most part EGR is beneficial. It is a lot like getting an octane boost (at no extra cost) and does allow for better fuel economy as well as overall better emissions *if* the engine is tuned to accommodate the changes in burn characteristics. That means changing air/fuel ratio as well as timing. The modern vehicle's computer takes care of all of that for you so yes you can get along quite nicely with any knowledge of it.
-jim
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wrote:

That's hilarious coming from someone who's above statement describes the EGR as metering air and fuel.

Must be why they all had the same part number (not).

Now you're getting it. Did the 87 Dakota V-6 use a vacuum amplifier?

Sounds like something the guy at the junkyard would say.

Never said otherwise.

Indeed.
Which is not the same as asserting that the EGR changes the air fuel ratio.

Absolutely.
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aarcuda69062 wrote:

Ultradrive innovation?
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In article
snipped-for-privacy@whoever.com wrote:

Yes.
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jim wrote:

You can't possibly realize how quickly this situation has progressed since I first posted. I stopped mid-post in my 3/21 4:19pm reply to Mike Romain in order to pull the carb, tear it down and make modifications to the ports in the throttle body based on the ongoing suggestions that I was given and my own very intimate knowledge of this carb and it's various configurations. I am doing this work as I see fit based on my understanding of the situation at any given moment. I am also trying to reply to all posts and explain the work that I have done, the reasons for doing it and the results I have gotten.
I'm sorry if I don't do it in a way that you deem proper.

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Simpson wrote:

I don't particularly care much how you do it. I was trying to empress upon you that the advice you get is only as good as the information you supply. For instance why is it you changed the carb in the first place? And how much have you driven with the new one? If someone cared, they might guess that the old carb was running very rich and you haven't driven very many miles on this one. It may pay off to just drive it a few hundred miles. It may take a while to recover from whatever was previously wrong. Also fiddling with the idle mixture is not likely to help much. When your going down the road the throttle is usually open enough that the idle circuit is no longer doing anything.
-jim

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jim wrote:

Actually, I'm doing quite well, thank you. I appreciate your suggestion about advancing the timing. Perhaps you should limit your posts to asking questions and making suggestions instead of trying to correct what you seem to regard as my inappropriate posting methods in my communications with others.

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