Vacuum take offs...

[davecara]

As I'm fitting throttle bodies between my plenum and head I need to take my MAP/Fuel Reg readlings from between the throttle butterfly and the head.

To get consistant readings has anyone ever used a vacuum manifold? Something I can attach the 4 runners to and then take my metrics from there. Just thinking it'll be more reliable than T pieces etc

[davecara]

Following further research, I'm going to make one of these from an offcut of fuel rail. As you were.....

 

 

[ElBlandito]

About halfway down page 3 is a good example of a shared vacuum tube for your reference.

 

Also, relating to your question in turbo bike, these are the tap locations I plan to run.

Plenty of folks on this site have laid out the work, I take the easy route and bookmark anything of interest for reference later on.

 

Good luck Dave and get it going!

Edited March 17, 2021 by ElBlandito
corrected location callout

[Gixer1460]

1 hour ago, davecara said:

 

Should turn out neat - might pinch that idea myself LOL!

[MeanBean49]

2 hours ago, davecara said:

As I'm fitting throttle bodies between my plenum and head I need to take my MAP/Fuel Reg readlings from between the throttle butterfly and the head.

To get consistant readings has anyone ever used a vacuum manifold? Something I can attach the 4 runners to and then take my metrics from there. Just thinking it'll be more reliable than T pieces etc

Wouldnt that just allow boost/air to bleed off from the firing cylinder into to others?

Ive only ever paired them up in pairs if that makes sense, 1+4 and 2+3 

Probably doesnt make any real difference

Edited March 17, 2021 by MeanBean49

[davecara]

50 minutes ago, MeanBean49 said:

Wouldnt that just allow boost/air to bleed off from the firing cylinder into to others?

Ive only ever paired them up in pairs if that makes sense, 1+4 and 2+3 

It will in effect make the spaces between the Inlet valve and the butterfly one big vacuum chamber. I cant see it having any impact on AFR to be honest but time will tell! The MAP and FPR need to be referenced from the same place so I cant think of any other way of doing it really

 

[MeanBean49]

28 minutes ago, davecara said:

It will in effect make the spaces between the Inlet valve and the butterfly one big vacuum chamber. I cant see it having any impact on AFR to be honest but time will tell! The MAP and FPR need to be referenced from the same place so I cant think of any other way of doing it really

 

I wasnt thinking about it affecting AFR, was thinking more about boost pressure and the loss off it. 

I guess even though air can flow from one cylinder to another freely if they are all linked they will still be pressurised roughly the same irrelevant of what stroke each cylinder is on

[davecara]

11 minutes ago, MeanBean49 said:

 

I guess even though air can flow from one cylinder to another freely if they are all linked they will still be pressurised roughly the same irrelevant of what stroke each cylinder is on

Thats the plan, we'll see if it works soon enough!

[Askamaskinservice]

Put an oriface in on each tube to dampen the pulsating as you do when syncronizing carburators.

(I hope this makes sense)

 

//Hasse.

Edited March 17, 2021 by Askamaskinservice
Wrong words used.....

[davecara]

35 minutes ago, Askamaskinservice said:

Put an oriface in on each tube to dampen the pulsating as you do when syncronizing carburators.

(I hope this makes sense)

 

//Hasse.

Good idea 

[Arttu]

I have that kind small manifold for MAP and regulator, connection to each throttle is through small orifices. Works well but on the other hand just connecting all the take-offs together with typical vacuum hoses and T-joints seems to give almost as good result. In contrast using just one throttle results quite badly jumping MAP readings.

Typically take-offs on the throttle bodies are so small that air flow through them can't cause any noticeable effect for cylinder balance.

[Gixer1460]

1 hour ago, Arttu said:

 but on the other hand just connecting all the take-offs together with typical vacuum hoses and T-joints seems to give almost as good result.

That worked well enough for me also - I added a nipple into each inlet rubber to allow common connection across them with take offs for MAP, BOV and FPR. I do think the manifold idea would tidy up the plumbing though.

[ElBlandito]

This is how mine is currently setup NA, with the single port only going to the MAP. The bare brass nipple was capped later on prior to running

Edited March 18, 2021 by ElBlandito

[davecara]

Couple of bits to sort out and make my vac manifold and we’re good to go 

[colinworth79]

Used a vac manifold on my bandit for 5 years , it's on carbs tho .Taking the pipes off where you would fit a carb balancer . 1 pipe to each port . No t peices .On my 7/11 turbo with gsxr 600 k1 tb's I have drilled and tapped the underside of each inlet port and fitted a small an-3 fitting . 

[colinworth79]

[davecara]

Made a thing

[Fredrik_Steen]

The regulator don´t want to see vacuum, just fit it to the plenum.

Vacuum makes the fuel pressure unstable and it drops below your base setting. (idle and part throttle)

 

Wastegate don´t need vaccum fit it to the plenum or turbo.

Edited March 31, 2021 by Fredrik_Steen

[davecara]

A rising rate regultor wants to see the same as the map sensor sees so the fuel pressure can rise in direct correlation to the boost pressue. And yes, the wastegate doesnt want connecting but the BOV does 

[Fredrik_Steen]

10 hours ago, davecara said:

A rising rate regultor wants to see the same as the map sensor sees so the fuel pressure can rise in direct correlation to the boost pressue. And yes, the wastegate doesnt want connecting but the BOV does 

"fuel pressure can rise in direct correlation to the boost pressue" it will do that connected to the plenum.

You get a nice stable fuel pressure that rise with boost pressure.

If you have vacuum the pressure will jump up and down and you get of your set base fuel pressure.

[Arttu]

Ideally you want the fuel pressure react to vacuum too. That way the pressure over the injectors stays constant and you get always the same amount of fuel with certain injection duration. Without vacuum to the regulator the effective pressure will get higher when there is vacuum at the intake and that results worse resolution for tuning.

If the take-offs are done properly the pressure shouldn't jump too much.

[Gixer1460]

23 minutes ago, Arttu said:

Ideally you want the fuel pressure react to vacuum too. That way the pressure over the injectors stays constant and you get always the same amount of fuel with certain injection duration. Without vacuum to the regulator the effective pressure will get higher when there is vacuum at the intake and that results worse resolution for tuning.

If the take-offs are done properly the pressure shouldn't jump too much.

I would guess that either method would be ok - vacuum sense or not, if the map was created whilst using vac sense or not, the mapped values would automatically include the differential in pressure but as said it is a minimal effect in reality. My bike got mapped NA first and included vac sense to create a baseline map to which boost was added as a compensation. As the FPR saw both + / - pressure it gave the injectors delivery a 'static' pressure of 3 bar.

[Arttu]

Yes, both will work and usually difference isn't huge. But if you are using big injectors it may become more important. With big injectors the challenge is to get good enough fuel delivery resolution for idle and low load. And now if you don't have vacuum connected to the regulator the injectors will effectively get even bigger exactly where you would need the maximum resolution.

Otherwise it's like you said, you will just tune around the varying injector flow. But naturally that's yet another variable to be compensated by the tune.

[Gixer1460]

Good point re: Big Injectors - that's the advantage running 8!