Build Thread Enola- Finishing touches

#501
I am using a mini cooper bypass opened when under vacuum. 1"hg will open the bypass fully. It is a 1 3/4" pipe.

I believe that the purpose of the bypass is to prevent SC surge. Not feed the engine air at idle/part throttle. The SC is still spinning, forcing air through the system. The bypass creates an equal pressure on both sides of the SC, quieting it's operation and reducing heat. I believe that all the piping is creating dry flow drag reducing the air velocity thus requiring the engine to Rev higher to stay running. But as of yet this is all theory.

My previous setup utilized 2 TB worked well but was ugly as sin. I may revert back too the dual TB setup to elevate this issue.

For the record the TB I am using is a 75mm piece. The intake was ported to match.
 
#504
hmmm I have a 75mm piece off of a 4.6 the only problem is that I will have to modify my current setup to bolt the thing into place..... I would rather have another tb that will bolt in place and use the same type of linkage. The cable setup will be my biggest issue, getting 2 tb to move in perfect sync with each other.

if I do, I will still use the remote mount iac. this way I can keep the sc tb closed to prevent unwanted wine at part throttle but allow the engine to receive enough air to idle smoothly. this will require some finaggleing to say the least and another throttle cable....

Off to the JY meca, where I find all my best ideas.
 
#505
a91what said:
I am using a mini cooper bypass opened when under vacuum. 1"hg will open the bypass fully. It is a 1 3/4" pipe.

I believe that the purpose of the bypass is to prevent SC surge. Not feed the engine air at idle/part throttle. The SC is still spinning, forcing air through the system. The bypass creates an equal pressure on both sides of the SC, quieting it's operation and reducing heat. I believe that all the piping is creating dry flow drag reducing the air velocity thus requiring the engine to Rev higher to stay running. But as of yet this is all theory.

My previous setup utilized 2 TB worked well but was ugly as sin. I may revert back too the dual TB setup to elevate this issue.

For the record the TB I am using is a 75mm piece. The intake was ported to match.
Click to expand...

That all makes sense and you are right about the extra piping adding loss (drag) and reducing the flow velocity. I'm still trying to understand why it idles well with the throttle body in the stock location. You don't change anything else when you put the TB back in front of the intake manifold right (SC and bypass are hooked up the same way)?

Regardless, it sounds like you have a way to get it working with the two throttle bodies. I'm just continuing to think about the issue more out of personal curiosity.

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#506
You are correct, nothing else changes.

My frustration stems from the fact that the supercoupes have there system plumbed in a similar manner.... but in that system the IC piping is smaller and the intake manifold is just a small "pancake" with almost no volume. Oh and the piping system is a much shorter run.

At least my current setup looks much more appealing, even after I implement the second TB the system will look less cobbled together.
 
#508
taking a shot in the dark here and I've only been poking my head in randomly, but what is the difference in vacuum with the TB in the stock location versus with it on the blower inlet? If you've already been through that, I apologize.
 
#510
Oh, that's the issue then right? Vacume can't hold with the closed throttle plates being so far away from upper plenum. Or at least the vacume dies with that distance from closed plates and can't recover enough vacume before the engine dies.

Does this mean your pipes aren't sealed enough or is this just too much open area that 800 rpm idle doesn't produce enough for that amount of volume? So then if you had a smaller volume upper intake it might work? I'm a little slow, just now clicking...

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#512
No leaks in the system it's speed density so a leak would not matter anyhow. I believe the volume is the issue but I'm not educated enough on the subject of fluid dynamics.. your vortec feeds the tb. So no issues there anyway.

My system has to have an intercooler in it, I'm not sure I can reduce the volume enough to fix the issue. Maybe a milder cam would idle lower, the e303 cam is a bitch.
 
#513
Well, after thinking about it a little more and seeing the recent responses, I agree that the extra length between the supercharger and intake manifold is the problem at lower rpm. In a simplistic sense, the flow rate into the engine is a function of delta pressure between the plenum and the cylinder (let's say delta p = positive intake pressure - vacuum). At higher rpm, your vacuum is higher, as well as the pressure of the incoming air from the supercharger spinning faster. I'm going to go with my initial theory. With the throttle body right at the intake manifold, the supercharger is drawing in air at atmospheric pressure with the flow rate dictated by the pipe area. At 800 rpm in this setup, the supercharger is pressurizing the flow enough to produce the required delta p at the intake manifold to sustain the engine. With the throttle body in front of the supercharger in the closed position, you are creating a big enough drop in flow and pressure that the pressure rise across the supercharger at 800 rpm is not enough to cover the extra loss from the piping and the required delta pressure at the manifold. In other words, both the lower vacuum and the lower pressure out of the supercharger are effectively reducing the delta p. You can't do anything about the vacuum but you can impact the intake pressure. The three options I see are:

1. Figure out a way to make the throttle body more open at 800 rpm than it normally would be (increase flow, reduce pressure drop across throttle body).

2. Figure out a way to draw some outside air into the intake behind the throttle body (if you already have a method for this, I apologize for missing it).

3. Two throttle body setup.

All of these let the supercharger add work to more flow at a higher pressure which would result in more pressure going into your intake manifold.

In the conventional setups you reference, the shorter distance between the supercharger and intake manifold make this pressure loss minimal compared to what you have. Its not so much the volume as the length. The extra surface and turns hurt your total pressure and dynamic head (velocity). In the usual setups, I believe they actually favor the throttle body upstream of the supercharger so that it isn't pounding the TB with pressurized air.

I may have repeated some of my initial post, but hopefully this clarifies what I think is happening. I may be wrong or I may be right. I may be oversimplifying it but it's the only way I can rationalize the results in my head right now.

Either way, I have to commend you for the work you've done so far. It really does look good. I understand the frustration but you are going to have a pretty cool and unique setup working soon.

...I will stop writing such long posts now...

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#514
skyline247 said:
Well, after thinking about it a little more and seeing the recent responses, I agree that the extra length between the supercharger and intake manifold is the problem at lower rpm. In a simplistic sense, the flow rate into the engine is a function of delta pressure between the plenum and the cylinder (let's say delta p = positive intake pressure - vacuum). At higher rpm, your vacuum is higher, as well as the pressure of the incoming air from the supercharger spinning faster. I'm going to go with my initial theory. With the throttle body right at the intake manifold, the supercharger is drawing in air at atmospheric pressure with the flow rate dictated by the pipe area. At 800 rpm in this setup, the supercharger is pressurizing the flow enough to produce the required delta p at the intake manifold to sustain the engine. With the throttle body in front of the supercharger in the closed position, you are creating a big enough drop in flow and pressure that the pressure rise across the supercharger at 800 rpm is not enough to cover the extra loss from the piping and the required delta pressure at the manifold. In other words, both the lower vacuum and the lower pressure out of the supercharger are effectively reducing the delta p. You can't do anything about the vacuum but you can impact the intake pressure. The three options I see are:

1. Figure out a way to make the throttle body more open at 800 rpm than it normally would be (increase flow, reduce pressure drop across throttle body).

2. Figure out a way to draw some outside air into the intake behind the throttle body (if you already have a method for this, I apologize for missing it).

3. Two throttle body setup.

All of these let the supercharger add work to more flow at a higher pressure which would result in more pressure going into your intake manifold.

In the conventional setups you reference, the shorter distance between the supercharger and intake manifold make this pressure loss minimal compared to what you have. Its not so much the volume as the length. The extra surface and turns hurt your total pressure and dynamic head (velocity). In the usual setups, I believe they actually favor the throttle body upstream of the supercharger so that it isn't pounding the TB with pressurized air.

I may have repeated some of my initial post, but hopefully this clarifies what I think is happening. I may be wrong or I may be right. I may be oversimplifying it but it's the only way I can rationalize the results in my head right now.

Either way, I have to commend you for the work you've done so far. It really does look good. I understand the frustration but you are going to have a pretty cool and unique setup working soon.

...I will stop writing such long posts now...

Sent from my Nexus 6 using Tapatalk
Click to expand...
Whew...that was a mouthful:D
Can I take door #3? Because...cool? Didn't you have it idling before with the dual t.b. setup?

Option 1 would probably be the easiest to try. Can you change the ms to read the throttle position slightly different than its actual position? For example..if you adjust where the the throttle blade is open slightly but not increase the rpms?

The above mentioned reasons makes sense. That is a long distance the air has to travel.
 
#515
Hmmm. I never thought of option 1... would the iac and adjustment plate (frpp piece) not perform the same action?

I will try that.

For the record I can do whatever I want with the MS... lol I can tell it 75% throttle is closed if I so desire. Lol.
 
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#517
a91what said:
Oh and I am drawing in a it behind the throttle body... iac feeds plenum directly.
Click to expand...
The IAC has a limit to how much it can draw in and I believe it's supposed to supplement the slightly open throttle body with more air. If you are currently pumping in slower, less pressurized air into the intake manifold than an NA setup, I'm not sure it would solve the problem on its own. You are already maxing out the IAC right?

My thought was something like another IAC in between the throttle body and supercharger so that it feeds the supercharger. This would mean more fabrication so its obviously the most difficult solution. Its probably not worth the hassle if option 1 doesn't work. If opening the throttle body more helps your situation, it would prove that the SC just needs more air. A separate IAC would then be helpful if you want to keep the TB closed as is. I'm very interested in your results.

If it doesn't work...you have already proven that option 3 works.

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#518
Okay so I tried fiddling around with option 1 to no avail. So today on my way home I stopped at the local u-pull-it and scored myself in Explorer upper with 65 millimeter throttle body I may switch to the Explorer upper from my Cobra just so I have more room we shall see. Right now I'm doing some fabrication I will see if I can make this system work again with two throttle bodies it should it work before. I modified the 65 with a new throttle linkage plate obviously even if I have gotten the Fox throttle body one cable is pulled further than the other based on the geometry of the holes so I copied just the throttle pole and duplicated it this way both throttle bodies are pulled the same distance I'm going to try to get any vacuum number in the supercharger piping it probably won't happen or will cause issues so atmospheric will have to be acceptable here's a pic of my modified throttle body
20160217_173044.webp
 
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