20 replies to this topic

[Lt-SilverDragon]

Hey guys, I'm having an issue with my mini that hopefully someone with more knowledge than I can help with. Basically I've got an lambda gauge fitted and when I'm driving the fuel/air ratio is pretty good, not perfect but usually sits about 12.1:1 to 14:1 under acceleration and when I'm holding the throttle to maintain speed, the issue arises when I need to change gear or slow down. As soon as I release the throttle the meter immediately shows lean and you can actually feel the car lurch because of it then it settles back to normal, I've been trying to drive by slowly reducing the speed I bring the throttle up to get me by the now until I can resolve this issue which isn't ideal.

 

I've got a HIF44 carb fitted with a BBA needle, red spring and ram air pipe, Amethyst ignition and a slightly worked head with a standard cam. Could the spring be forcing the dashpot down too quickly? My only thought at that is because I figure if the dashpot came down too slowly it would suddenly run rich because the needle would be supplying more fuel then air?

 

Hopefully someone actually knows their stuff unlike me and can point me in the right direction.

[Icey]

 you can actually feel the car lurch because of it then it settles back to normal

 

You're going to have to explain that a little more as it just sounds like engine braking.

 

When you close the throttle you'll have pretty much nothing but air running through the engine (injection systems cut all fuel in these conditions), it'll always show lean.

 

But I'm not sure I'm understanding your description.

[Lt-SilverDragon]

Yeah pretty much engine braking but a lot more forceful then I'm use to, my
other minis didn't feel like that when releasing the throttle and it really unbalances it when it happens. I'm perhaps being overly paranoid the now but I'm trying to keep this mini in tip top shape so every lil thing worries me. Admittedly I'm probably use to the creature comforts of modern cars now as it's been a few years since I've been able to drive one of my other minis so it might not be a huge issue but it does bog down a bit if you're accelating upto 60 and you release the throttle to change gear then get back on the gas.

[Retroman]

Has it been on a dyno ? or is it an estimated guess for the needle ?

 

It will have to go lean when you close the throttle or it will keep revving....which is shixxer !!

[Lt-SilverDragon]

No dyno near me unfortunately, just guessed at the needle and been keeping at eye on the air/fuel gauge like a hawk. Tried the standard MG one, BDL I think but drives better with the BBA needle. Actually I canny mind what needle I settled on, I'm pretty sure it's the BBA.

[Spider]

Have you checked your engine mounts and engine steadies?

 

Otherwise, sounds normal and fine to me.

 

If you have your A/F Ratio where you want it (and looks OK to me), then loose the gauge as it will otherwise show 'problems' that aren't there.

[ACDodd]

What piston damper are you using in he HIF 44?

Ac

[Lt-SilverDragon]

What piston damper are you using in he HIF 44?
Ac

What do you mean by which piston damper? I'm using 3in1 oil or possibly 10w40 engine oil and a red spring in the dashpot, sorry for the vague answer. I put the carb on last year so I've forgotten.

[Lt-SilverDragon]

Have you checked your engine mounts and engine steadies?
 
Otherwise, sounds normal and fine to me.
 
If you have your A/F Ratio where you want it (and looks OK to me), then loose the gauge as it will otherwise show 'problems' that aren't there.

Yep engine steadies are fine, new poly bushes in them. I'll not worry too much about it then, maybe try different things to see if I can lessen it a bit though.

[carbon]

 

What piston damper are you using in he HIF 44?
Ac

What do you mean by which piston damper? I'm using 3in1 oil or possibly 10w40 engine oil and a red spring in the dashpot, sorry for the vague answer. I put the carb on last year so I've forgotten.

 

I think there are different types of damper used in the HIF44 - there should be a number embossed on the black plastic cap.

 

And standard SU damper oil is straight 20 weight, the closest multigrade is 5W30. 3 in 1 is less viscous.

[Lt-SilverDragon]

I did not know that, I'll need to look at what damper is on it then. I've got spares so I can swap them about if I've got a different damper, might order the proper SU oil as well to rule that out as well.

 

EDIT: Oh yeah, there's loads of different types of damper.

Edited by Lt-SilverDragon, 08 March 2018 - 09:03 PM.

[Lt-SilverDragon]

I've fitted a different spring now and ordered proper SU oil, the car doesn't go as lean anymore but that might be because I took the needle out to make sure I didn't damage it when fannying about with the dashpot so it's now running a tiny bit richer then it was before. I tried a spare damper I had as well but it was struggle to push it in, felt a lot tighter then the other one so I used the original, now when I push the piston into the dashpot it comes down at the same rate as what I can push it in as. 

[Icey]

I tried a spare damper I had as well but it was struggle to push it in, felt a lot tighter then the other one so I used the original,

 

Dashpot and damper are matched, you shouldn't mix'n'match them.

[ACDodd]

I say again, what damper are you using?

Dampers are not matched.

Ac

[Icey]

Dampers are not matched.

 

I stand corrected! Any idea why that's become an accepted idea? Or is it just old mythology?