24 replies to this topic

[dennisb]

Hello everyone, I hope someone can give me a spot of advice...

My set-up at the moment is that I've got an MPi with an MED phase 3 head, 52mm throttle body, 1.5 rockers, induction kit, fuel pressure regulator and full new exhaust system.

The few rolling road/tuning people local to me are finding it difficult to get my fuelling sorted as the fuel pressure valve seems to have very slight adjustment and even the tiniest turn of the valve changes things.

The car hesitates at different revs and loads. Out-with these flat-spots it performs very well. It also has an uneven idle and 'hunts' a bit between 800-850 rpm swinging between the two quite quickly.



I'd like to disconnect the new pressure regulator and try the car with it's original one, really as an experiment more than anything else to see if it sorts things.



A few questions...


I was wondering if it is possible to re-connect the cars original fuel pressure valve, and therefore let the car's ecu decide on it's own fuelling? (Surely this is the way it should be...) (I didn't want the after-market valve, but a Mini specialist I won't name told me I needed it)

Is this an easy job? I'm a total novice.

Would buying a replacement (better) regulator maybe be a better idea?

Even though I've had all the sensors checked, is there something else that could cause my fuelling problems, like a dodgy injector or something?

[nicksuth]

You have a very similar set up to my MPi and very similar symptoms - runs okay when under load but just doesn't like to sit at constant revs while just feathering the throttle (i.e. motorway driving between 3500-4500 rpm). I also was recommended the adjustable pressure regulator with the assumption that the old one had poor seal (and yes, when I took it out the seals were buggered) and advised that once the pressure was set the valve would just operates quicker than the original set up and be more responsive.

I have changed every sensor apart from the cranksaft sensor, had injectors ultrasonically cleaned and calibrated, K&N induction kit, 52mm alloy throttle body, LCB and RC40, even decatted it to see if that was a contributor? Head off and checked all valves/seats (replaced one bent pushrod - umm, strange???).

Did 100 miles yesterday and 200 mile round trip to Huddersfield today and just had to keep loading/unloading throttle otherwise it just spluttered and popped!!!

It has improved since I replaced all these items but just won't clear completely???

Hopefully get it plugged in to a fault reader this weekend and then rolling road in the next week or so?

It also has a Icon Race Chip fitted which we thought might be the culprit but on linking it out, made no difference.

Just need to keep at it I guess???

Just bought a complete inlet manofold/throttle body/fuel rail/filter housing etc. for £50 just in case I decide to change it all back?????

BLOODY MPI'S !!!

Oh, to answer your question, you can convert it back but the fuel feed and return pipes would probably have been cut and fuel return line blocked coming out of the rail so you will have a bit of "splicing" to do???

Edited by nicksuth, 07 May 2009 - 09:15 PM.

[dennisb]

Good to know I'm not alone.

Had a good chat with an local engine tuner today. He said that the most likely things to be causing bother are either badly set pressure (which we already know) and/or a badly positioned pressure regulator. If my old one is capable of the pressure needed for the new throttle body, he said he'd reconnect it for me sometime and do a test. If not, I should try a better quality regulator in a better position and see what difference if makes. My current regulator's in a mad place - on the O/S inner wing at the very front, so there's long sections of fuel line.

Waiting on Burlen getting back to me to tell me the minimum pressure the 52mm body needs.

Also forgot about something when I wrote my original post... 2 of my plugs are a nice golden brown colour, indicating a decent mixture, but the other 2 are pretty oily and damp, indicating a rich mixture. I found this out a while back just doing some routine maintenance, so changed all the plugs and leads. Didn't make any difference. Any ideas why this would be? I was thinking maybe a dodgy injector, but then again, if I had a bad injector surely the engine would run badly all the time and not just at 2000 under load and at 3000?...

[nicksuth]

Which pair of plugs are wet/oily? If it 1&2 or 3&4? Obviously, each of the 2 injectors feed a pair of cylinders so could be the injector if it's common?

Iv'e positioned my regulator as per photo below, not fixed yet as I'm not sure whether I'm keeping it and don't really know where I'm going to put it eventually anyway??? It really should be mounted vertically to ensure no air is trapped.





Keepu me posted with any developments?

PS - I had also replaced plugs, leads and even the coil pack£££££

[bigmotherwhale]

did you buy your regulator from ebay? my friend has a tubo honda and he said he bought one that drove him crazy, also sounds like the pipe to the regulator is massively long which could affect vaccum if its not super stiff, is it made of rubber or hard plastic?

[dennisb]

Thanks for the reply bigmotherwhale,

The regulator wasn't bought on ebay, the Mini specialist that fitted it provided it for me.

Having seen some others in my friend's cars, I doubt it's of very good quality.

All of the pipes leading to and returning from the regulator are long! The regulator really couldn't have been put in any further away from the fuel rail!



oh aye, the new pipes at the regulator are all quite soft rubber ones.

Edited by dennisb, 14 May 2009 - 02:09 PM.

[nicksuth]

Sorted, see http://www.theminifo...x...30&start=30

[dennisb]

'the pressure regulator is now set at 2.6 - 2.7 bar at idle'

A mighty useful piece of information! I take it this remains the same no matter which head the engine has? I'll give the tuner dude a shout and see how he's fixed to re-locate my regulator and do the necessary adjustments.

Thank you!

ps. hope this is the bit you mean!

pps. Just out of interest - do you happen to know the pressure the standard regulator puts out? Is this 'variable'? Might be best ditching the aftermarket and sticking with the original...

[tmsmini]

Info from workshop manual:
Fuel Pump:
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electric immersible
Pump maximum pressure at 16V . . . . . . . . . . . . . . 2.7 bar
Regulated injection pressure range . . . . . . . . . . . . . 1.0 to 3.0 bar ± 0.2 bar

[nicksuth]

This is where it get confusing.

The Rover manual says..........
Max pump pressure is 2.7 bar @ 16v, also says regulator operates between 1.0 and 3.0 bar +/- 0.2 bar
Haynes Manual says.............
Pump regulated pressure 1.0 to 1.3 +/- 0.2 bar

I had my PBV left at the original factory setting (as recommended) of 2.0 bar, then, 2 x 1/4 turns c/w brought it up to 2.6 to 2.7 bar which is what is now locked off at.

I'm sure someone (Sprocket) posted that the pressure setting of the stanard setup was 2.0 bar?

I think the standard relief valve was regulated by manifold depression? The PBV is just supposed to react quicker to the changing demand?

Lets see what others think?????

[nicksuth]

PS - got my PBV from MiniSport - http://www.minisport...VK384MGF1H.html is this same as yours???

[dennisb]

Yes, the regulator itself looks remarkably similar. Mind you, it doesn't have a red hose connecting to it as shown provided. As far as I can see, it doesn't have the other smaller metal part either...

This is mine fitted in it's bizarre position...









Got an email back from Burlen about the minimum pressure their 52mm Throttle Body needs to operate. They don't know.

[dennisb]

Info from workshop manual:
Fuel Pump:
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electric immersible
Pump maximum pressure at 16V . . . . . . . . . . . . . . 2.7 bar
Regulated injection pressure range . . . . . . . . . . . . . 1.0 to 3.0 bar ± 0.2 bar

So going by this and a later post, if I need between 2.6 bar and 2.7 for my set-up (roughly!), then the existing regulator can handle it with 0.3 bar to spare. The pump itself would be at it's peak output too.

Is the original fuel pressure regulator variable? Will the ECU decide how much pressure it needs?

[bigmotherwhale]

that hose doesnt look like a vcaccum line! replace it with a hard plastic one like the servo has but thinner, and you should get an improved response

[nicksuth]

The "extra bit" is the pressure gauge, goes in where you have the brass plug (not supplied in kit but available from ebay etc.).

Not sure what you mean by the "Red Hose"??? It has fuel feed in via the rail as normal, new relief valve in end of rail with connection for returns to regulator (in side of regulator) and then return back to tank (bottom connection of regulator), the vacuum hose then connects from the top of the regulator to the manifold. The old return pipe from the fuel rail is then cut and plugged.

I'll get some better pictures this weekend when I work out were to bolt the regulator to???

Edited by nicksuth, 15 May 2009 - 11:01 PM.