Talk to me about fuel & air
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right, this is assuming the engine's timings etc. all sorted

standard 1275 carb'd (high velocity low pressure air)
atmosphere + 3.5psi fuel pressure should be enough to get the fuel through

turbo 1275 (converts to low velocity high pressure air)
atmosphere + 3.5psi fuel pressure at no boost

then your compressing air blowing it in the carb to force more air through
along with more fuel = poweerrr


we regulate are fuel through a diaphragm that raises letting in more fuel from the rising pressure signal at the carb
which inturn fills the resevoir on the carb faster to cope with pressure changes within the venturi

then the mixture how much air to fuel is controlled by the screw under the carb


my question really is, why 9.5psi fuel pump would be no good when all it needs to do is fill the carbs reservoir enough to not lean out
and why for every psi of pressure does it need to be 3.5 over?
and if thats the case why didnt the metro turbo's come with 15psi fuel pumps instead of 40?


Im being told by a very experienced mechanic that i should be running the 9.5 pump as 40 is too high
i wasnt running too rich before but now its overfuelling at idle
so will too much fuel pressure will force the float on the carb open, overflow the resevoir an spray too much fuel into the intake?
or even force the diaphragm open without splitting?
stiffer spring needed?

i did say i need to set up the fuel pressure but apparenlty that doesnt matter and its the air pressure thats the problem?

im massively confuzzled

Edited by WRLondon on 12th Aug, 2013.

Reading up on RTS Clutches

im at the stage of thinking i should take the 40psi pump back out and put the 9.5 psi one in
as my only problem was fuel delivery above 5psi boost
now it doesnt it even run without washing the plugs

would be alot easier via injection as you can tell the engine almost exactly how much fuel you want according to manifold pressure >.<

Edited by WRLondon on 12th Aug, 2013.

Reading up on RTS Clutches

you need the pump to be able to over power the boost pressure
fuel pressure should be boost pressure + 3.5 ish psi

you can actually run the engine on boost with the pump turned off, because the carb feeds fuel in to the engine out of its own reservoir ( float bowl ) the problem comes when this is empty (rather quick on boost)
the fuel pump needs to be able to push fuel in there whilst the boost tries to push it back out


the carb is blind to the pressure almost ( thanks to the plenum) whilst it does react slightly differently on boost i doubt its anything you would notice

i dont understand what your saying here -

Yes i moved to the darkside

Instagram @jdm_brett

Yes i moved to the darkside

Instagram @jdm_brett

sorry my minds abit mashed at the moment haha
right by atmosphere i mean air under no pressure
will check the float valve now

what i think is happening is because of the immense fuel pressure its forcing its way past the regulator, opening the float valve and spraying wildly regardless of the butterfly being opened or closed

cant find any highstreet store that sells a fuel pressure gauge either :(

Reading up on RTS Clutches

exactly what i thought
fuel pressure regulator
REGULATES THE FUEL FLOW
apparently not its the air pressure not the fueling thats the problem :S :S
and a fuel pressure gauge wont help either

On 12th Aug, 2013 Brett said:

On 12th Aug, 2013 WRLondon said:

Im being told by a very experienced mechanic that i should be running the 9.5 pump as 40 is too high

and tell him from me if he doesnt know what the fuck he is on about.. keep his trap shut!

40psi is to high at idle but your pump does not produce this...what you think the fpr is for? and why does it increase the fuel pressure with boost
if you set the fpr to 3.5 psi at idle the whole fuel system is at 3.5 psi

this is the most basic of stuff aswell

Edited by WRLondon on 12th Aug, 2013.

Reading up on RTS Clutches

Yes i moved to the darkside

Instagram @jdm_brett

i meant diaphragm @ the regulator

ok will order a fuel pressure gauge now set it at 3.5 then mess about with the mixture and idle

then get it RR'd for the needle profiling

Reading up on RTS Clutches

I bought one of these
http://www.ebay.co.uk/itm/Fuel-Pressure-Ga...=item27b6ca9ed6
No issues with it and comes with a blanking plug so you dont have to have the gauge in there all the time. As has been said, all you can do is speculate if you dont actually know whats going on.

http://www.turbominis.co.uk/forums/index.p...tid=469104&fr=0

which fuel pump then?
9.5 psi? or 40psi?

im still getting told insistently that the fuel pressure regulator doesnt control how much fuel pressure there is or how much is being chucked through it :S

Edited by WRLondon on 13th Aug, 2013.

Reading up on RTS Clutches

40psi.

The whole point of the regulator is to control the fuel pressure seen throughout the fuel system. With the engine idling and the pressure at the carb set at 3.5psi, if you put the gauge before the regulator it will still show 3.5 psi.

I have a fuel pump off some porsche and a metro turbo regulator and i do have to wind the screw most of the way out but it will give you 3.5.

http://www.turbominis.co.uk/forums/index.p...tid=469104&fr=0

the proper metro one
check the plumbing and the return line, if the return cannot flow more fuel than the feed the fpr cannot do its job

Yes i moved to the darkside

Instagram @jdm_brett

Edited by WRLondon on 12th Aug, 2013.

Reading up on RTS Clutches

Also the return pipe is plumbed to the top of the petrol tank so not a lot of pressure needed to return

Reading up on RTS Clutches

9.5psi pump is theoretically only good for 6psi boost. I certainly wouldn't trust it at even that little boost.

The guy you are talking to hasn't a clue what he is talking about.

Get a fuel pressure gauge as suggested many times between your threads on this topic, set it to 3.5psi at idle, then see what's happening.

Without a gauge, you could well be putting far too much pressure to the carb, causing it to leak and cause your problem.

As suggested above, it could also be due to your return pipe being too small. But you won't be able to determine what the problem is until you get a pressure gauge.

In the 13's at last!.. Just

have a look at this from about 35 seconds on....

https://www.youtube.com/watch?v=Kub3q1-YNZA


the 40 psi pump will not make 40... it is "capable" of 40 psi.

with no spring in the regulator all the fuel will piss back to the tank and there will be no fuel pressure.

the reason metro's cam with 40 psi pumps is they just used what was available... ie same as the montego efi.

Edited by Joe C on 12th Aug, 2013.

Fuel squirts out regardless if I set the FPR screwed out to the max or in
The diaphragm isn't split and I've got 2 good ones :s
So think I need to re-adjust or rebuild the float valve anyway

Lol that's the video I watched yesterday
And the name suggests it regulates the fuel pressure

Ordered a gauge so we'll see

Edited by WRLondon on 12th Aug, 2013.

Reading up on RTS Clutches

Had you rebuilt the carb before you fitted it? if not then i'd get a rebuild kit for it and do that while you wait for a pressure gauge

http://www.turbominis.co.uk/forums/index.p...tid=469104&fr=0

ok, sounds like it could be the float valve as you say,

if you pull the pipe off the carb you should easily be able to block the flow of fuel with your thumb... if it squirts like fuck like a garden hose then the pressure really is high.

Was meant to be a rebuilt carb but Ebays like that
Will get a kit and watch some videos on YouTube lol
Keep me busy until the pressure gauge arrives

Reading up on RTS Clutches

what pump do you have and what pump are you being told to use?

The original Metro Turbo pump is more akin to a fuel injection pump., It is not one of these Facet ticker pumps such as the 'Red Top'. You need a rotary vein pump. Selection is huge as pretty much every fuel injected car has one, either in tank or external.

Pumps generate volume flow (CC/Minute, Litre/Hour) it is the 'restriction' against the flow that generates the pressure. Pumps have a maximum pressure rating after which the pump will stall and flow nothing. The flow of the pump decreases as the pressure rises, so most pumps are rated with X.X flow at X.X pressure. A pump rated with a maximum pressure of 9psi will, over this pressure, flow less and less, until such a point it stops pumping all together (if it doesn't overheat and burn out beforehand). For you to be successul you need a pump that can flow enough fuel to satisfy the demand of the engine, and be able to do that at the desired fuel pressure. That of course depends on the boost pressure.

The magic number for setting carburetor fuel pressure regulators in any case is 3.5 to 5psi. This ensures that there is a posative pressure difference that will allow fuel to flow into the carburetor. It needs to be high enough to allow the fuel to flow, but not so high that it forces the needle vlave open.

In a boosted carburetor application the carb and fuel float chamber are all exposed to boost pressure (at a slightly different level, which is the real reason for the restrictor in the plenum, but lets not let that confuse anything any more than we need to here). The pressure regulator raises the fuel pressure proportionally with boost pressures o that even at 20psi boost, the fuel pressure is still 3.5 to 5 psi above, which means that fuel still flows into the carb under boost conditions.

Simples :)

There seems to be a mix up in how the pumps are being rated. Just spoke to my brother to make sure I have this right but I do believe pumps are rated by flow rate. A pump free pumping into an open Vessel creates flow but no pressure it is the restriction of the return path that creates the increase in fuel pressure we see between the fpr and carburettor. The standard pump fitted to the metro turbo is the same item fitted to the SD1 Maestro and Montego efi and is capable of sustaining a fuel rail pressure upward of 8bar, now this is a rough figure comparing it to the Bosh unit fitted to XR3i which I know can go much higher. According to my brother he would expect to see around 100psi or more in the fuel rail possibly lower but but 100 is already low.

The fuel pump has to produce a flow rate that can maintain the 3.5psi over pressure against the varying leak created by the needle and jet. This is why the old diaphragm pump had to be replaced with a vane type pump. And being Rover it was a parts bin special. Most any pump can make pressure but can said pump maintain pressure and demand with low flow? Also can a low flow pump create pressure on demand across the range some cars on here require.

An example of this is the pump for my Subaru Legacy GTb. It uses the same pump as fitted to the WRX. In the spec for the pump it states it has a flow of 450 litres per hour no mention of psi.

So it is the flow rate the pump is capable of that you need to concentrate on. A pump with excessive flow will create an adversely high system pressure due to the return path not having sufficient volume to cope with the excessive flow. This I probably why a ballast resistor was fitted to the metro turbo fuel pump to slow it down and reduce flow.

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Started writing the above about an hour ago dinner got in the way but two explanations saying the same thing.

Own the day

Are you usingna genuine turbo carb or an hif44. I had the same issue when using an hif44. Ive also had the same issue when I put the wrong pipe direction into the regulator. All a leqring curve.