MBC question

[carlukepeugeot]

Hi peeps. I've fitted a Mumby boost controller to the XUD Dturbo. Plan to adjust the pump soon, but currently still running at 14 psi boost. I noticed that the spool time is much better, the car feels more responsive. Also my slight haze on boost is gone. Just trying to get my head around it - is there any way in which this is bad for the engine? Can the MBC result in a lean condition at all?  like there is higher boost levels (still below the 14psi though) at lower engine speeds ?

To me it seems like even just having the MBC in line without adjusting fuel has improved responsiveness and spool times but just curious if there is any downside to that.

Cheers
Craig

[Martin306]

The short answer is no (the long answer is too complicated), you can't run a diesel too lean. fuel quantity regulates engine speed which in turn will regulate the amount of boost the turbo can make.

To me it sounds like your turbo has a weak actuator spring and it's opening too soon - fitting the boost controller has artificially "strengthened" it. so I would be fitting a new actuator before you do anything. So your car is basically now performing as it was intended.

Pretty much no smoke is what you want. if you have access to something that can measure the AFR you'd probably want to target anywhere between 16-20:1 at full load.

We really need to leave this "light haze" stuff back in the 90's - a time when diesel tuning was a relatively new thing. It's a very rough guide and it's totally useless if you've got a downwards pointing exhaust tip and small mirrors!

[carlukepeugeot]

So turned the pump up today. Found initially that my car was fuel limited - it would get up to 14psi nice and quickly with the MBC installed, but didn't matter if I kept screwing it in further, still 14psi. So I backed it off a bit then upped the max fuel by about 30 Degrees. Now at 16 psi ( almost 17 flat out at top end in 5th) and the car is much quicker, also nicer to drive with improved throttle response.

Very little to no smoke either on boost or off boost, so I think I have found the sweet spot- could add a little more fuel and aim for 18psi but might not bother. I was surprised to see no smoke as I have read that the lucas pump is always smokey on a tune. Interestingly the car is now less smoky (I can't see any) than before I tuned.

Seem OK what I have done?

[Martin306]

So turned the pump up today. Found initially that my car was fuel limited - it would get up to 14psi nice and quickly with the MBC installed, but didn't matter if I kept screwing it in further, still 14psi. So I backed it off a bit then upped the max fuel by about 30 Degrees. Now at 16 psi ( almost 17 flat out at top end in 5th) and the car is much quicker, also nicer to drive with improved throttle response.

Very little to no smoke either on boost or off boost, so I think I have found the sweet spot- could add a little more fuel and aim for 18psi but might not bother. I was surprised to see no smoke as I have read that the lucas pump is always smokey on a tune. Interestingly the car is now less smoky (I can't see any) than before I tuned.

Seem OK what I have done?

ach aye it'll be fine min!

I've found my Lucas pump to run less smokey than the VE I had. I think maybe people can't be arsed with the hassle of adjusting the fuel screw so just turn it too much, then add boost

[carlukepeugeot]

Brilliant Martin, thanks for all the help!