Lean when setting off
Turbo Mini Forums

HGF has now been fixed and mini is ruuning Sweeeeeeeet boosting around 1 Bar on the gauge but going to plug in the laptop and check what MJ says.

The issue is nothing to do with Boost but with going lean when setting off.

At tickover the mini AFR shows 13.6 ish but when setting off the AFR goes all the way to the RED for a second or two then reutrns back to normal. The part throttle lean off is connected at present so may look at blacking it off.

Whats your thoughts gents?

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

Does it hesitate or miss because of this?

If it pulls of nicely and is good upto and on boost I wouldn't let it bother you

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

its flat as a pan cake when in the red for that second, then no issue at all.

It just seems to lean right off when kissing the throttle like the bowl isnt lifting or the part throttle lean off is kicking in.

Other than that runs perfect now.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

Van used to do this, can't remember what we did to cure it?

If something is worth doing, it's worth doing half of.

Its just a pain as for a split second its flat then off it goes, may be Andy can remember......

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

more rev's

That was one way! I seem to recall something like thicker oil & a heavy damper spring.

If something is worth doing, it's worth doing half of.

Didn't we change from 20/50 to proper dash pot oil? If it's too thick to let the piston rise when setting off, then you don't get any fuel.

May try the good old 3 in 1 oil, currently has 20/50W millers in.

Or just buy some SU oil?

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What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

Just get SU oil, doesn't cost much.

That's it. We ended up with a BCA needle, 12oz spring, new piston damper and SU dash pot oil. Worked well on van but not so well on my clubby.

If something is worth doing, it's worth doing half of.

Ordered

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

used a green spring and thicker dashpot oil in mine to cure this...

I'll try the SU oil then look at the spring!!!! Has standard turbo spring fitted at present.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

Brett may chime in here later but I seem to recall him saying that the more boost he ran the stiffer the spring he required

If something is worth doing, it's worth doing half of.

I believe green is the stiffest. also run 75/90 transmission oil in the dashpot here

dont have an issue on boost as yet, its just the initial setting off with minimal throttle.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

for enrichment on acceleration you need thicker dashpot oil but if your on 20/50 already you may well need 0.05mm taking off the needle around stage 2-4 depending on spring, tapering out either end BUT this will also give slightly more fuel at low speed cruse ( unless you use the lean off pipe to pull the fueling back on stable state cruising)

a heavier spring would need a higher pressure drop across the bridge to lift the needle the same amount the result being more fuel will be sucked through for the same station and would seem to solve this issue BUT..
there are downsides to 'just fitting' a heavier spring. if there are no changes to the needle it may run lean ( or leaner ) on higher loads if your having the needle profile changed after fitting the spring go for it it does help

Yes i moved to the darkside

Instagram @jdm_brett

Cheers Brett,

Changed the dash oil to 3 in 1 to try it out.
Didn't seem to drop the afr when pulling it in the garage.

Got some su oil on order and should arrive Monday so will try that.

Will try and keep an eye on the afr tomorrow on way to Tatton hall performance and classic car show.

Going down with some peps I don't really know and they think mini is standard, should be fun.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

The A35 has developed the same symptoms and has been a right PITA on the visit last week to Devon, making me look a right pillock revving to pull away and then nearly ramming the car in front.

Robert has suggested restricting the free movement of the piston on its rod in the carb - but he also advises that there should be some free movement.

Didn,t want to get my hands mucky on holiday so haven,t tried it yet !

something i looked into but decided i didnt have the tooling to test,
if you look at the piston part of the su damper it moves, this is so it only dampens while the piston is rising but allows it to fall freely
there is a slight delay before it starts to dampen ( as the collar (sp?) around the piston moves up to seal)
you can increase or reduce this delay by lengthening or shortening the collar(sp?) around the piston
allowing the needle to 'jump' up a station or two now i havenot tested this so its hard to say if that would make it leaner or not without changing the needle profile ( due to the pressure drop change ( that i predict))

my disclaimer lol !!
everything ive learnt about the SU HIF carb is self taught from testing and data logging so if some of my theorys go against what a book would say tuff, i found this works

Yes i moved to the darkside

Instagram @jdm_brett

So........... you'll need to increase the initial allowed travel of the plunger to posibably over come this issue ?????????

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

Tbh get the needle right and you wont have this issue

Yes i moved to the darkside

Instagram @jdm_brett

SU oil arrived today so going to give that a go first, also having fluctuating oil pressure so new releif plunger ordered.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

interested in the findings Lee; I'm experiencing similar issues