The Official Venturi Delete Thread
05-24-2007, 07:48 AM
#1
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The Official Venturi Delete Thread
Since there is so much confusion as to what exactly the venturi delete entails, I figured I'd make this thread so people searching can find the info easily. I was as confused as everyone else until I had an epiphany (light bulb turning on over the head) one night while looking at diagrams and finally understood. It was quite a glorious moment. lol
I have attached pictures instead of including in the post so that the pictures will remain with the post instead of disappearing due to hosting issues at a later date.
*edit*
I realized after posting this that I was incorrect about the hose that runs between the ICV and hardpipe, in that it is changed by the deletion of the venturi pipes. I have updated the description and pictures to fix this error.
Definition:
The venturis are two Y-connector pipes used in the large vacuum lines on 86 and 87 turbos. They are shown in attached picture #1 and #2. These pipes were not used on later cars. Looking at the simplified diagrams I've attached below, you really do wonder why the factory even put the venturis in place at all. It simply makes more sense to have the seperate vacuum lines.
The two vacuum lines affected by the venturi pipes are the vacuum line that goes from the hardpipe to the Idle control valve to the intake, and the line that goes from the intake to the brake booster. In attached pictures #3 and #4 you can see a basic diagram of where the venturi pipes come into play and how they connect the two vacuum lines. In attached pictures #5 and #6 you can see the specific parts related to the venturi lines and how the lines are routed when the venturis are removed. In the 5th and 6th pic the red line is the line that goes from the hardpipe to ICV to intake, the blue line goes from the intake to brakebooster and the yellow line shows the venturi pipes.
Venturi Deletion:
NOTE: The removal of the venturis does not require the metal control line assembly to be removed. The control line is the piece of three metal tubes that are welded together. You can see the assmebly of the control line in attached pictures #5, #6 and #11, and in the diagrams you can see that it is not touched in the process of removing the venturis.
As the attached diagrams show, the process of deleting the venturis is actually fairly simple.
Several companies sell "venturi delete kits," such as Lindsey Racing, however these are not necessary. These kits include three hoses: one from the hard pipe to the ICV, one from the ICV to intake, and one from the brake booster to intake.
Why you don't need the kit: (not trying to ruin sales or anything, just being helpful)
hardpipe to ICV hose: This hose does get changed by the deletion of the venturi tubes. The hose position and running is the same in early and late cars, but the cars with the venturi pipes have the smaller metal venturi piece in the middle of this line. I tried to show this in picture #7, but unfortunatly the that is the only picture I have of the hoses and it isn't very good. Because of the fact that there is the metal venturi splitter in the middle of this hose piece (between the hardpipe and ICV), you will have to change things.
Option 1 would be to buy the replacement hose from the later model car, as shown in picture #8, which is essentially the same just without the venturi splitter in the middle. Part number 951.110.217.01.
Option 2 would be to keep the venturi setup rubber hoses, but remove the metal venturi splitter and replace with a section of pipe to connect the two hose pieces (I believe 3/4" pvc pipe works for this).
Option 3 would be to keep the metal splitter in place and block off the third connection on the piece, by either putting a bolt into the end or some other method.
ICV to intake hose: This hose is the exact same on all 951's, so unless your current hose is broken there is no need to buy a new one.
brakebooster to intake: Again, this is technically a different hose between the later and early cars, but should not be needed. From attached picture #9 you can see that the original brakebooster line is longer than the replacement one due to the placement of the venturi system, so this means the hose will connect up to the intake without issue once you cut the venturi pipes off. (I need to confirm this as well, but it definitely looks like it will work from pictures)
Check Valve:
The only remaining difference then is the small check valve at the end of the metal control line assembly that is on the pipe that runs between the j-boot and oil-air seperator (OAS) (this can be seen circled in green in attached picture #6). You can run without this piece; the car will smoke slightly while under boost, but otherwise there are no issues. However, if you do want to run with the valve, there are two ways you can get this piece.
Option one is to buy the oem replacement hose from a late model car. The part numbers for this hose is 944.107.311.03 and the check valve is 944.107.324.00. However, buying these new will cost close to $100 and will require that you remove the metal control line assembly because the new pipe is a shaped piece. This hose and check valve is shown in attached picture #10.
Option two is to get the control line assembly, or specifically the piece with the check valve, from a late model turbo that is being parted. This is what I did - attached picture #11 is the used control line I bought from a 88 that was being parted. It ends up being a lot cheaper buying the used piece, and you are able to keep the metal control line pieces in place. The specific hose and check valve can be seen in the diagram in attached picture #6 circled in green.
Anyway, I hope this clears the whole venturi delete thing up for everyone.
If anything is incorrect, please let me know and I'll correct it.
I have attached pictures instead of including in the post so that the pictures will remain with the post instead of disappearing due to hosting issues at a later date.
*edit*
I realized after posting this that I was incorrect about the hose that runs between the ICV and hardpipe, in that it is changed by the deletion of the venturi pipes. I have updated the description and pictures to fix this error.
Definition:
The venturis are two Y-connector pipes used in the large vacuum lines on 86 and 87 turbos. They are shown in attached picture #1 and #2. These pipes were not used on later cars. Looking at the simplified diagrams I've attached below, you really do wonder why the factory even put the venturis in place at all. It simply makes more sense to have the seperate vacuum lines.
The two vacuum lines affected by the venturi pipes are the vacuum line that goes from the hardpipe to the Idle control valve to the intake, and the line that goes from the intake to the brake booster. In attached pictures #3 and #4 you can see a basic diagram of where the venturi pipes come into play and how they connect the two vacuum lines. In attached pictures #5 and #6 you can see the specific parts related to the venturi lines and how the lines are routed when the venturis are removed. In the 5th and 6th pic the red line is the line that goes from the hardpipe to ICV to intake, the blue line goes from the intake to brakebooster and the yellow line shows the venturi pipes.
Venturi Deletion:
NOTE: The removal of the venturis does not require the metal control line assembly to be removed. The control line is the piece of three metal tubes that are welded together. You can see the assmebly of the control line in attached pictures #5, #6 and #11, and in the diagrams you can see that it is not touched in the process of removing the venturis.
As the attached diagrams show, the process of deleting the venturis is actually fairly simple.
Several companies sell "venturi delete kits," such as Lindsey Racing, however these are not necessary. These kits include three hoses: one from the hard pipe to the ICV, one from the ICV to intake, and one from the brake booster to intake.
Why you don't need the kit: (not trying to ruin sales or anything, just being helpful)
hardpipe to ICV hose: This hose does get changed by the deletion of the venturi tubes. The hose position and running is the same in early and late cars, but the cars with the venturi pipes have the smaller metal venturi piece in the middle of this line. I tried to show this in picture #7, but unfortunatly the that is the only picture I have of the hoses and it isn't very good. Because of the fact that there is the metal venturi splitter in the middle of this hose piece (between the hardpipe and ICV), you will have to change things.
Option 1 would be to buy the replacement hose from the later model car, as shown in picture #8, which is essentially the same just without the venturi splitter in the middle. Part number 951.110.217.01.
Option 2 would be to keep the venturi setup rubber hoses, but remove the metal venturi splitter and replace with a section of pipe to connect the two hose pieces (I believe 3/4" pvc pipe works for this).
Option 3 would be to keep the metal splitter in place and block off the third connection on the piece, by either putting a bolt into the end or some other method.
ICV to intake hose: This hose is the exact same on all 951's, so unless your current hose is broken there is no need to buy a new one.
brakebooster to intake: Again, this is technically a different hose between the later and early cars, but should not be needed. From attached picture #9 you can see that the original brakebooster line is longer than the replacement one due to the placement of the venturi system, so this means the hose will connect up to the intake without issue once you cut the venturi pipes off. (I need to confirm this as well, but it definitely looks like it will work from pictures)
Check Valve:
The only remaining difference then is the small check valve at the end of the metal control line assembly that is on the pipe that runs between the j-boot and oil-air seperator (OAS) (this can be seen circled in green in attached picture #6). You can run without this piece; the car will smoke slightly while under boost, but otherwise there are no issues. However, if you do want to run with the valve, there are two ways you can get this piece.
Option one is to buy the oem replacement hose from a late model car. The part numbers for this hose is 944.107.311.03 and the check valve is 944.107.324.00. However, buying these new will cost close to $100 and will require that you remove the metal control line assembly because the new pipe is a shaped piece. This hose and check valve is shown in attached picture #10.
Option two is to get the control line assembly, or specifically the piece with the check valve, from a late model turbo that is being parted. This is what I did - attached picture #11 is the used control line I bought from a 88 that was being parted. It ends up being a lot cheaper buying the used piece, and you are able to keep the metal control line pieces in place. The specific hose and check valve can be seen in the diagram in attached picture #6 circled in green.
Anyway, I hope this clears the whole venturi delete thing up for everyone.
If anything is incorrect, please let me know and I'll correct it.
Last edited by billthe3; 06-06-2007 at 06:57 AM.
05-24-2007, 10:46 AM
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Hey Bill,
You are welcome to use any of the information that I complied in the original writeup. I keep trying to find the time to update that information, but alas, it always gets put on the back burner. I really want some newer clean pictures for the word document. Maybe this will kill 2 birds with one stone
You are welcome to use any of the information that I complied in the original writeup. I keep trying to find the time to update that information, but alas, it always gets put on the back burner. I really want some newer clean pictures for the word document. Maybe this will kill 2 birds with one stone
05-24-2007, 12:51 PM
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On my 86 turbo, I had no check valve originally. If this is case for anyone else and not just me, you can simply just buy two 3/4inch hose connectors, a piece of 3/4inch radiator hose, and a 90 degree 3/4inch elbow and replace that hose yourself. That is what I ended up doing and it looks like this...
You would only need to do this if you were deleting the cycling valve and wanted to get rid of the 3 metal pipes welded together.
You would only need to do this if you were deleting the cycling valve and wanted to get rid of the 3 metal pipes welded together.
05-24-2007, 01:14 PM
#4
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Originally Posted by 5speed300
On my 86 turbo, I had no check valve originally. If this is case for anyone else and not just me, you can simply just buy two 3/4inch hose connectors, a piece of 3/4inch radiator hose, and a 90 degree 3/4inch elbow and replace that hose yourself. That is what I ended up doing and it looks like this...
You would only need to do this if you were deleting the cycling valve and wanted to get rid of the 3 metal pipes welded together.
You would only need to do this if you were deleting the cycling valve and wanted to get rid of the 3 metal pipes welded together.
05-24-2007, 02:26 PM
#5
Three Wheelin'
I'd like to discuss the necessity of the check valve on MAF/MAP equipped cars. I have no hard data, just thinking things over a little. As I understand it, the purpose of the check valve is to alleviate some of the vacuum that the crankcase sees when under boost. Apparently the valve maintains some vac in the crankcase, which is good, but too high of vac can lead to too much oil vapor being pulled into the intake, which degrades octane and therefore performance.
In a MAF/MAP equipped car, I would speculate that the vacuum induced in the j-boot is lower than the vacuum in the j-boot of a car running the stock AFM due to the higher restriction to intake air.
So, is the check valve necessary on a MAF/MAP equipped car? To know, we would need to find out at what pressure the check valve is set to open, and what levels of vac the j-boot sees for both MAF and AFM cars. It would be pretty cool to hook up a vac gauge to the AOS-> J-boot line and take a few readings under boost.
Along the same lines, imagine what sort of pressure differential exists when a catch can is installed in line. How much vac is the crankcase actually getting then, especially when running a MAF and the hoses are 2x as long to route the can to different parts of the engine bay.
Thanks for reading my ramblings. Comments?
P.S.- Bill- Excellent write up. If this is too off topic for your thread, please let me know.
In a MAF/MAP equipped car, I would speculate that the vacuum induced in the j-boot is lower than the vacuum in the j-boot of a car running the stock AFM due to the higher restriction to intake air.
So, is the check valve necessary on a MAF/MAP equipped car? To know, we would need to find out at what pressure the check valve is set to open, and what levels of vac the j-boot sees for both MAF and AFM cars. It would be pretty cool to hook up a vac gauge to the AOS-> J-boot line and take a few readings under boost.
Along the same lines, imagine what sort of pressure differential exists when a catch can is installed in line. How much vac is the crankcase actually getting then, especially when running a MAF and the hoses are 2x as long to route the can to different parts of the engine bay.
Thanks for reading my ramblings. Comments?
P.S.- Bill- Excellent write up. If this is too off topic for your thread, please let me know.
05-24-2007, 03:10 PM
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Originally Posted by KuHL 951
Don't use radiator or heater hose for anything exposed to hydrocarbons, they will soften up and leak pretty quickly. Finding oil rated hose in the right sizes can be tough but at least they will hold up. I gutted the snake nest, venturi, and cycle valve also. Finding a snug 90 deg elbow for the OAS was the hardest part but NAPA found something from a Ford emissions system.
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06-04-2007, 05:39 AM
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The answer would be 0, 1, or 2. 
The smaller metal pipes in the control line assembly are only there for the cycling valve, so if you are not using the cycling valve anymore they are not really needed. You can get rid of one of the smaller pipes and still use the second pipe for your current boost controller, or you can get rid of both smaller pipes, or you can just leave both the smaller pipes there and not connected to anything.
Crap, I think I was wrong about needing to buy one hose. Time to go look at some pictures.
The smaller metal pipes in the control line assembly are only there for the cycling valve, so if you are not using the cycling valve anymore they are not really needed. You can get rid of one of the smaller pipes and still use the second pipe for your current boost controller, or you can get rid of both smaller pipes, or you can just leave both the smaller pipes there and not connected to anything.
Crap, I think I was wrong about needing to buy one hose. Time to go look at some pictures.
06-05-2007, 10:39 PM
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I did mess up in my description of hoses needed. The one between the hardpipe and ICV is not the same between the early and late cars; one of the venturi pieces is in the middle of what is two hoses, compared to the one piece hose of the later cars. I didn't realize the problem because there was no labeling for direction on the ICV in the diagrams. Anyway, I'll update the pictures to fix the error later tonight.
06-06-2007, 06:55 AM
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Ok, fixed it. The problem was with the hardpipe to ICV hose. Re-read the description to understand the issue. Also added some more pics to aid in the explanation, as well as correction the labeling errors I had made on some of the original pictures.
06-08-2007, 06:41 PM
#14
Ok I swear to god on my 944 this will be the last venturi question. With the updated intake to brake booster hose from lindsey, does that go all the way from the intake directly to the booster? or to the white plastic T that feeds that small vacuum line with the a/c check valve? if the former its ok then to feed that vacuum line off a different line back there. Sorry I am oh so close to ending this saga and feel much more enlightened. thanks to all.
06-08-2007, 11:51 PM
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Originally Posted by Cosmatics951
Ok I swear to god on my 944 this will be the last venturi question. With the updated intake to brake booster hose from lindsey, does that go all the way from the intake directly to the booster? or to the white plastic T that feeds that small vacuum line with the a/c check valve? if the former its ok then to feed that vacuum line off a different line back there. Sorry I am oh so close to ending this saga and feel much more enlightened. thanks to all.
You cut the long brake booster hose where it connects to the big white plastic T. One side runs to the intake from the T, the other to the brake booster.