65 replies to this topic

[Sprocket]

the fuel pump builds pressure behind the regulator, its the regulator that controls the fuel pressure, after all thats its sole purpose.

Sounds like you need to adjust the fuel pressure. Im not sure how that is done with these regulators as they are a rising rate, never looked at one or read anything about them. I know the principle but when it comes to setting one up, you will have to look at the instructions that came with it.

The whole thing with these regulators is that it idealy should match the idle fuel pressure with high manifold vacuum, but at full throttle and zero manifold vacuum the fuel pressure should rise above the norm, by how much, i do not know, is it adjustable or a fixed value?

[nicksuth]

The pressure can be adjusted by an adjuster under the domed nut on the top of the valve but instructions start by saying "it's already pre-set for the vehicle it was purchased for" (purchased via MiniSport so I assumed it was set for an MPi?). - Link - http://home.freeuk.c...ak/pbv_info.htm

I should have done a pressure check before I fitted it really as I beleive the persihed o ring in the bottom of the original releif valve was probably causing the fuel to pass at lower pressure causing the problem?

My concern is over pressurising the system and damaging the fuel pump?

It certainly runs better now but impossible to know which change made the difference? I guess I need to just run it and see and then get it on the rollers before I adjust the pressure any further (1/4 turn = 0.5 bar apparently)?

[tony kenobi]

Hi Nick, great to see you got your problem sorted.
I took mine for a spin on saturday for the first time since the engine build. It all seems fine untill you try and floor it, then it starts coughing so im thinking my regualtor is set too lean. Im hoping a clockwise turn of the screw on top will make it fuel better and higher rpm.
I guess with these things its trail and error. Tho i just bought a gauge to put on it to make sure im not at too high or low. Ill come back to you on my findings.

[nicksuth]

It does run so much better now but I did so many changes I can't be sure which fixed it (got an idea it was the perished o ring in the old regulator?)

I see now why you didn't fix the valve in the engine bay, there's no bloody space (especially when you've got an ultimate top steady bar!!!). I've just left it loose as you have.

I'll be taking it out for a run at the weekend with some regular stopping to check pressures etc. I'll get back to you with the results.

As soon as I've got over the Christmas spend I'll get it down to the rolling road for a full set up.

Keep me posted on your progress.

Nick

[tony kenobi]

Hi Nick, new years day and of course im working on the mini, lol.

anyhow, been trying a few things with the new pressure gauge i got and im finding that after i turn the key to position 2 (just beofre turn over) the fuel pump kicks in as norm, and the reading on the gauge is around 40psi. but if i leave it there, the gauge slowly starts to drop. Is this an indication of a leak somewhere? would this possibly be the cause of my coughing at hig revs when driving only? Im thinking of sending the injectors away for a clean as you have done, and also replacing the orings on the whole injection system. Can you point me towards where to get the rings, and how many i need if i was to replace the ones on the injectors, fuel rail etc.

Thanx for your help!

[nicksuth]

Fuel Rail end O rings are different to the Injector O rings...........



Left one is for Injector and Right one is from Fuel Rail ends. Get them ordered from Moss as they do both types.

If you are going to get the injectors cleaned ultrasonically go to www.injectortune.co.uk - see................

http://cgi.ebay.co.u...E...A1|240:1318

or email [email protected]

This is where it's getting confusing,

Sprocket is saying if you do manage to get the fuel pump running without the engine, fuel pressure should be 3bar. If the engine is running and idling, fuel pressure will be around 2.7bar. The differential pressure remains the same at 3bar.

KLAS is saying you should see around 2,5 bar with closed throttle and 3 bar at wide open throttle

mini 4o is saying around 2.7 as soon as the regulator lifts, leave the gauge for at least 10min to settle with the ign on. No need to start the engine, just watch to gauge if it fluctuates then look for a petrol leak, noisy pump, or faulty regulator

Confused???? I am

[tony kenobi]

Yeah, tho they are around the 2.5 figure. But the fact that when i turn the key pressure is good, then it goes down and down, slowly but still does not remain at a set level. Well, ive the injectors out now (god these are great little engines to work on, 5 mins and its done,lol)

Im intrested nick in how you blocked the return feed from the fuel rail when fitting the regulator. Ive mine in bits now, so its a good time to block it off proper-meaning mabe tapping it and screwing in a bung, or welding the end of the pipe shut.

[nicksuth]

40 psi (3 bar) with ignition ON and engine NOT RUNNING is as per Sprockets info. I would expect the pressure to drop over a preiod of time due to wear on seals in pump etc. but at some point you would expect the pump to pulse and take the pressure back up again?

Does anyone know the pump operation? Does it pulse on "Pressure" in system, i.e. on pressure fall?

What does yours do when you rev the engine? Mine snaps to 3 bar immediately (just as it says on the tin !!!) which suggest to me it is responding to the fuel demand correctly?

I thought long and hard about blocking off the return line and ended up doing as you have - fitted a bolt with some sealant ad a couple of jubilee clips. If everything works okay I'll look at blanking the end of the fuel rail by cutting back the tube and tapping for suitable plug?

[Sprocket]

NO no no no

The fuel pump is only energised for a second or two when key on, nothing more, there is no pressure sensing, the pump or the ECU does not know what the fuel pressure is. When you start to turn the engine over, the ECU senses activity on the crank sensor and then energises the fuel pump. Simple

The pump will move fuel through the pipes as much as it will pupm, so if its a 75 litre/ hour pump, it will move 75 litre/ hour. The pressure regulator causes a restriction, lifting the pressure to its set pressure then diverts the remaining 'flow' of fuel back to the tank, so as to maintain the set pressure

The fuel pump is not directly responsible for the fuel pressure.

Again, fuel pressure measured with a compound gauge on the supply fuel line is considered 'gauge' pressure, and will fluctuate with different throttle openings. The reason for this is that the fuel pressure regulator diaphragm is exposed to the manifold vacuum. This keeps the 'differential' pressure accross the fuel injector constant despite the change in manifold pressure. So with the engine not running and the fuel pump on, fuel pressure should be ~3bar 'gauge' pressure as the manifold is at atmospheric pressure. With the engine running at idle the 'gauge' pressure will be the 'differential' pressure minus the manifold pressure (vacuum) this is, despite what I may have said in previous posts, will be ~2.3bar. This is because the manifold vacuum will be ~0.3bar absolute, or 30 Kpa absolute at idle, this is ~520mmHg Vacuum. The differential pressure inside the injector will still be ~3bar but the gauge pressure will be ~2.3bar.

setting the idle fuel pressure to 2.3bar should give the results you are after.

Do remember that the ECU will need time to adapt to the extra fuel the rising rate regulator provides.

If when you turn off the fuel pump the fuel pressure slowley drops to zero over a period of time, this could indicate leaking injectors.

[nicksuth]

Okay, I understand.

Pump supplies fuel at variable pressure but fixed flow rate which recirulates back to tank, pressure in fuel rail (and thus available to Injectors) is controlled by the adjustable pressure relief valve. Return rate back to tank varies dependant on how much the Injectors (engine speed/load) is using?

The improvement given by the new valve is,
- variable pressure adjustment
- faster pressure change response (snap)

I'm sure the "Rollers" will help the set-up process.

[Sprocket]

Okay, I understand.

Pump supplies fuel at variable pressure but fixed flow rate which recirulates back to tank, pressure in fuel rail (and thus available to Injectors) is controlled by the adjustable pressure relief valve. Return rate back to tank varies dependant on how much the Injectors (engine speed/load) is using?

The improvement given by the new valve is,
- variable pressure adjustment
- faster pressure change response (snap)

I'm sure the "Rollers" will help the set-up process.

The 'Power Boost Valve' is a rising rate regulator. This type of regulator does not maintain a constand set pressure. Its design allows the 'differential' fuel pressure to rise as the Manifold pressure rises. In simple terms at idle you may have a differential fuel pressure of ~3bar, but at full throttle the 'differential' pressure may be ~4bar. The main reason why people fit these regulators is to provide more fuel to the engine using the standard injectors and ECU, usualy when the engine tune is such that the standard regulator, injectors and ECU would not be able to supply enough fuel causing a lean condition under load, which is normaly bad.

The 'faster response' is mainly attributed to the fact that there is more fuel entering the engine as a result of the higher fuel pressure at higher manifold pressures.

Like I siad before, im not sure how these regulators are set up, whether you can adjust the amount of rise in fuel pressure as well as the initial set pressure

[Sprocket]

I just had a read up. The FSE Power Boost Valve has a fixed rising rate of 1.7.

Its sole purpose is to increase fuel pressure by 70% on acceleration only, rather than my original thinking of it raising fuel pressure dependant on manifold pressure. baisicaly when you accelerate the fuel presure rises, then returns to normal , what ever you set it at.

I supose this will help especialy when you fit the larger throttle

[nicksuth]

Managed to climb out of my Man-Flu pit and take the Mini for a quick spin, just to keep battery charged up and to let the PBV settle down before taking some readings.

All pressures are after a 1/2 hour run to get things up to normal working temperature..................

- Ignition ON but engine not running = 2.4 bar
- Left on for 10 mins and pressure dropped to 2.0 bar
- Ignition OFF and left for for a further 10 mins = no change (steady at 2.0 bar)
- Engine running on tickover = 2.4 bar
- Engine running and "blipped throttle" = 3.0 to 3.2 bar then back to 2.6 bar
- Engine running and held throttle at 3000 rpm = as above then steady at 2.6 bar

Performance during run up the dual carriageway (once warm)............................

Very good throttle response in all gears and will rev up to 5500/6000 no problem, even in 5th gear (KAD 5 Speed Box fitted) it will pull from 1500 all ther way to 5000ish (maybe 5500+ anyway it was nearly 100mph and was running out of carriageway so watched the road rather than the tacho!!)).

That was the good news. The bad news is there is still a slight hesitation when feathering the throttle (similar to before but much less) i.e. trying to keep a steady 70mph in top. Maybe it just wants to "GO" and doesn't like steady running????

Just awaiting delivery of 52mm Throttle Body before I go to the expense of having the Race Icon Chip checked and then put it on the Rolling Road at Southam (when the Bank Balance has recovered from Christmas!!!!!)

Some photos of installation for Tony Kenobi below............

[nicksuth]

One last thing.

I guess with a 52mm Throttle Body, if I want it to "breath" adequately, I'm going to have to fit one of these ? >>>>>>>>



in place of the standard filter casing even though its got a K&N filter in it, like this ? >>>>>

[tony kenobi]

Im having another problem now. Got my injectors back from their clean, fitted with new seals etc. now when i turn the key to 2 position, the gauge shows me hitting round 3 bar, then what sounds like a relay or something clicks, releasing the pressure and the gauge hits zero again. What would be doing this? also took it for a quick spin, still getting the slputtering at over 3000rpm, anyone any ideas??

as soon as i turn the key off, the gauge alsways now drops to zero, but beofre i sent them off for a clean, i was keeping pressure, but it slowly went down over 10-15 mins. starting to get very fustrated now.