deac666
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| posted on 19/2/14 at 07:23 PM |
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throttle bodies question
 
Description
Hi all recently bought a new toy (see archive)
What I need to know is where does the outlet on the top of the blue valve need to go to.
Hope some one can help
cheers jon
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edthedrummer
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| posted on 19/2/14 at 07:26 PM |
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That's your fuel pressure regulator. Just leave it open, it's just a breather for the diaphragm inside from memory. We use them all the
time at work and they never get connected.
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Dave Bailey
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| posted on 19/2/14 at 07:29 PM |
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It connects to the inlet manifold so that a vacuum pulls the diaphragm.. Most don't connect it.
Dave B
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coyoteboy
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| posted on 19/2/14 at 07:30 PM |
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Hmm that's a tricky one, if it's the FPR reference it would normally go to the manifold to maintain a constant pressure differential
across the injectors. With no plenum that's obviously a bit tricky and I think a lot of bike negines use a sort of "mini plenum"
that connects all 4 ports with very small diameter hoses to provide a constant load reference.
Could just leave it, it's less ideal for control but can be worked around with correct mapping.
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deac666
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| posted on 19/2/14 at 07:42 PM |
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thanks for the reply's. its a pain in the arse to start could this be affecting the starting???
How would I connect it to the inlet and does it just need to connect to one inlet tract or all four??
Cheers jon
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coyoteboy
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| posted on 19/2/14 at 08:04 PM |
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How is it fueled? If it's injection (hence the throttle bodies, not carbs) then it will probably have been mapped with it like that so I
wouldn't change it, as you'll affect the rest of the running and it should not change the starting. It's useful purely to get a more
linear flowrate-to-dutycycle curve when tuning (meaning you can make more sensitive adjustments at idle,andaccount for boost if turbocharged) so
there's no NEED to have it connected, it can just help if it's needed.
If you were to connect it you'd need to do some experimentation, which won't be easy or useful unless you really know what you're up
to.
[Edited on 19/2/14 by coyoteboy]
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mark chandler
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| posted on 19/2/14 at 08:04 PM |
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It really needs connecting, you need to tap into all the TB's between the butterfly and head, there should be barbs then collect into a single
pipe and plug into the FPR.
If the signal is very bouncy then add something like a small fuel filter to act as an air reservoir.
It will affect starting, not a huge change as it depends how much throttle you apply when starting, and it depends if you car is mapped having it
connected. as the car starts it draws a vacuum on the pipe which lowers the fuel pressure so really affects throttle off idle and fuel on the
overrun.
Regards Mark
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coyoteboy
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| posted on 19/2/14 at 08:09 PM |
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I don't think it'll affect starting much at all, I've never seen <80% load during cranking with TBs on a few engines, so it
won't be having much effect. I've mapped identical engines both with and without and not seen a noticeable difference other than in the
values in the table (hence thinking it'll be fine unless he has a problem he wants to fix)
[Edited on 19/2/14 by coyoteboy]
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beaver34
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| posted on 19/2/14 at 08:10 PM |
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depends if its been mapped or not,
it adds fuel pressure based on vac pressure
they can be mapped with fixed rate fuel pressure, 3 or 3.5 bar looking at the reg or if connected its a 1-1 rising rate reg so will see a max of not a
clue at the moment 
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MikeRJ
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| posted on 19/2/14 at 09:12 PM |
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quote:
Originally posted by mark chandler
It really needs connecting,
It really doesn't. With alpha-n fuel control the change in effective fuel pressure is automatically corrected for when it's mapped. For
a speed density system it would make a bigger difference. There must be many thousands of cars running throttle bodies quite happily without this
being connected.
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deac666
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| posted on 19/2/14 at 10:58 PM |
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thanks for the replys.
If it makes any difference the throttle bodies are jenvery and running omex management.
Also its on a base map according to the previous owner.
Ive never run a car with throttle bodies and management. Its just a real pain in the arse to start and was not sure if this could be the problem.
cheers jon
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coyoteboy
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| posted on 20/2/14 at 01:22 AM |
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Base maps are, generally, designed for a bone-stock engine system with no account taken for mods, potential critical changes and finessing of
starting/drivability. They're just there purely to get it moving so it can be taken to a proper rolling road.
Get the FPR hooked up properly and get it to a rolling road, I'm fairly sure you'll see a world of difference from a generic map!
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Paul Turner
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| posted on 20/2/14 at 09:56 AM |
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Very few N/A cars have regulators that have the vacuum pipe fitted to the manifold especially on installs using individual throttle bodies. To get a
meaningful vacuum with no spikes it would be necessary drill all the headers and link them together. After all that work and the necessary re-map
there would be little (if any) improvement to the way the car runs.
Basically if the pipe is connected the fuel pressure varies with your throttle position. If its disconnected the fuel pressure remains constant at the
pre set value (normally 3 bar).
Mapping with them connected is much more time consuming for no noticeable benefit. If the car is well mapped without them there is no need to fit
them. Mine has run without them for over 9 years now with no issues. Some kits have clear instructions to leave the connection open to the
atmosphere.
If it ain't broke don't fix it as they say. One less thing to go wrong.
And having the pipe disconnected will make no difference to your cold starting.
[Edited on 20/2/14 by Paul Turner]
[Edited on 20/2/14 by Paul Turner]
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daveb666
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| posted on 20/2/14 at 10:42 AM |
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Never had the van pipe connected on the last 4 cars I've had with Tbs, including my current one.
dec666; if you fill in the location in your profile you may find there are people local to you 
2007bc Photography - Commercial and Wedding Photographer based in West Yorkshire
http://www.2007bc.co.uk / http://www.huddersfieldcommercialphotographer.co.uk
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deac666
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| posted on 20/2/14 at 12:49 PM |
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Thanks for all the reply's.
I am currently stripping the car down at the moment. and was just wanting to see if this was important. I shall leave it off for now until it goes to
rolling road. but I will tap into the intake after I remove the engine just so the option is there when time comes to get it mapped.
Cheers all.
jon
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coyoteboy
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| posted on 20/2/14 at 01:25 PM |
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quote:
Basically if the pipe is connected the fuel pressure varies with your throttle position. If its disconnected the fuel pressure remains constant at the
pre set value (normally 3 bar). Mapping with them connected is much more time consuming for no noticeable benefit
Sorry but I totally disagree. You seem to be missing how they work. The point of manifold referencing is to maintain a constant delta-p across the
injectors so 1ms pulse at idle delivers the same fuel as 1ms pulse at WOT. If you don't do that you find your idle regions can have insufficient
resolution to give good control. All OEM cars I've ever worked on, N/A or turbo, have referenced the manifold, and I've almost always
built it into every car I've added an aftermarket system to for that very fact?
But I do agree don't touch it if it wasn't mapped that way (but don't run around on base maps).
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Paul Turner
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| posted on 22/2/14 at 09:11 AM |
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quote:
Originally posted by coyoteboy
You seem to be missing how they work.
Understand fully how they work. Did loads of research before buying and setting my car up, all research said it was important on a Turbo but not
necessary on N/A. ALL the companies I spoke to with regards to buying parts/mapping said not to bother with a vacuum connection.
Providing its mapped correctly at the pressure set in the regulator the car will run perfectly. Mine idles smoothly, cruises smoothly, picks up with
no hesitation and is pretty economical. The CO's at idle are well with what is required for an MOT pass, mine is a Q thus not relevant.
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