Vacuum???

Mine is reading about 9-10 in hg at idle, and I am having issues with getting my HKS bov to actuate.
 
That sounds about right. Is it connect to 1 port, or all 4?

Also you trying to get it to activate just free revving or when you're actually in boost and let off?
 
Thanks for the response.

I was connected to TB #1 only. However, when I connect to all TB's, or 3 TB's, the vacuum stays the same at idle at around 10 inches. I thought that my vacuum should increase when hooked up to multiple TB's?

I installed the BOV and ran it in the bike. It would not actuate at all, so I removed the intake and tried to free rev it. Nothing. I then bench tested it with my vacuum gauge, which can pull about 24 in hg, and it will not open (probably because there is no boost pressure on the other side).


I should note that I just bought the bike over the winter. I am trying to work out all the issues. When I took it for a ride, it pulls 7-8 lbs of boost, and feels good, but threw a C21 code when I leaned on it.
 
You won't gain move vacuum as its only gonna pull what the motor will make.

Those valves are adjustable and it's way too tight if you pulled 24 and it didn't open.
 
I have solved the issue. I now have the BOV working properly, tied in to all 4 TB's. I now, however, am getting a C21 air temp code, when the bike is under load. Faulty sensor, or other issue?
 
It seemed like I was not getting enough vacuum on deceleration to activate the BOV, so I tied into all 4 to pull more vacuum. At the same time, I ended up cutting the spring and grinding it down to soften it up. The result is that the BOV is now being activated. Because I modified the spring at the same time, I am unsure which fixed the issue, or if it was a combination of the 2. However, now that I am tied into all 4, I am only reading 4psi of boost in my gauge. I am confident that there are no boost leaks. Our also only shows 4 psi of I disconnect the BOV and cap the line. My A/F ratios at WOT are good, and it is pulling very hard, so I am thinking it is misreading for some reason. I am going to tie the boost gauge back into a single TB to see if i get the same reading.
 
Just my thoughts and I have been an NA/displacement guy my whole life until now and I could very well be wrong, which is often the case. But vacuum is vacuum. Pressure difference isn't multiplied by multiple outlets coming from the same source. If you have 1 or 4 throttle bodies pulling the same vacuum from the source, it doesn't increase the vacuum with more lines. 4 lines of vacuum at the same level tied into one line should give you the same vacuum as one single line. You are necking it down into a single line anyway to get into the BOV. If it were a volume issue, the bottleneck would be the entrypoint into the BOV. I only have put this into practice once on a car that had such a big cam that the vacuum wasn't sufficient to run the power brakes at idle. So I tried running vacuum from instead of just manifold to manifold plus carb and anywhere else I could find it. The vacuum ended up being the same and equally inefficient at running the brakes, in fact I think it may have gotten worse although I cant explain that.
 
Not true as each cylinder fires differently, which will pull more vacuum, if you do not believe me connect a single vacuum line from a single cylinder to your factory map sensor and let me know how it runs,

Richard
 
I don't have a hundredth of the knowledge that you do to argue. Neither have I ever tried it on a motor with independent carbs/throttle bodies. And I certainly have had enough map sensor problems to know that I don't want to mess with it again. What do you think is going on with his BOV?
 
So the difference in your quote here to a motorcycle with individual throttle bodies is cylinder vacuum vs engine vacuum, the vacuum of an individual cylinder is definitely different than engine vacuum, think of each intake stroke on an engine, and if you measure each one by itself with a vacuum gauge you get the vacuum of the engine once every 2 revs, now connect it to another cylinder, while still attached to the first and you have a vacuum pulse every 1 revolution, and as you add more, you also add more vacuum pulses, so your vacuum becomes stronger and a lot more steady, you end up with more of a constant vacuum with engine vacuum, vs a vacuum pulse with individual throttle bodies. In you car application you mention you were already using engine vacuum, so it could not be increased,

Richard


Just my thoughts and I have been an NA/displacement guy my whole life until now and I could very well be wrong, which is often the case. But vacuum is vacuum. Pressure difference isn't multiplied by multiple outlets coming from the same source. If you have 1 or 4 throttle bodies pulling the same vacuum from the source, it doesn't increase the vacuum with more lines. 4 lines of vacuum at the same level tied into one line should give you the same vacuum as one single line. You are necking it down into a single line anyway to get into the BOV. If it were a volume issue, the bottleneck would be the entrypoint into the BOV. I only have put this into practice once on a car that had such a big cam that the vacuum wasn't sufficient to run the power brakes at idle. So I tried running vacuum from instead of just manifold to manifold plus carb and anywhere else I could find it. The vacuum ended up being the same and equally inefficient at running the brakes, in fact I think it may have gotten worse although I cant explain that.
 
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