Jump to content


Photo
- - - - -

Slow Throttle Response, What To Do?

engine

  • Please log in to reply
27 replies to this topic

#16 harrythehat

harrythehat

    Mini Mad

  • Members
  • PipPipPipPip
  • 258 posts
  • Location: wisbech

Posted 14 June 2018 - 06:50 AM

try changing your damper oil,

in the past have used other oils found 20/50 way to thick slows revving up down if that makes sense

always used three in one oil never had a problem



#17 90anlu92

90anlu92

    Learner Driver

  • Noobies
  • PipPip
  • 15 posts
  • Location: Halland

Posted 14 June 2018 - 10:01 AM

It didn't sound that bad to me.

Some tune up basics:

Always start with the ignition - the engine doesn't need to be running to gap the plugs and points and set the static timing. You can also check the dynamic timing against the specs independently of how it's running.

It's pretty much a waste of time trying to tune a carb if the ignition isn't up to scratch and it's not got up to running temperature.

Similarly, any other fault will have you chasing yourself in circles adjusting the carb if not fettled first. Clogged air filters, manifold air leaks, worn throttle spindles, dodgy float valves....

I don't know If I'd say it's bad, I just feel like the throttle response slowed down after I put the kit on... It seemed to rev better before, which is why I assumed it probably had something to do with exhaust, inlet and/or carb. Since that's what I've meddled with. You're absolutely right though, its best to start from the beginning. But like I said, the car ran well before so I thought it made sense to look for fault in something that I've affected in mounting the stage 1 kit.

Edited by 90anlu92, 14 June 2018 - 10:02 AM.


#18 90anlu92

90anlu92

    Learner Driver

  • Noobies
  • PipPip
  • 15 posts
  • Location: Halland

Posted 14 June 2018 - 10:03 AM

try changing your damper oil,
in the past have used other oils found 20/50 way to thick slows revving up down if that makes sense
always used three in one oil never had a problem


Right now I have 10w/40 in there, but maybe that's too thick as well... I've heard atf fluid is supposed to work, maybe I'll try that. What's three in one oil if I may ask? :)

#19 racingbob

racingbob

    Up Into Fourth

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 3,061 posts
  • Location: Hampshire

Posted 14 June 2018 - 10:07 AM

try changing your damper oil,
in the past have used other oils found 20/50 way to thick slows revving up down if that makes sense
always used three in one oil never had a problem

Right now I have 10w/40 in there, but maybe that's too thick as well... I've heard atf fluid is supposed to work, maybe I'll try that. What's three in one oil if I may ask? :)
it's that handy oil in a small white and black tin it's quite thin I use that gave more response or su oil ok

#20 90anlu92

90anlu92

    Learner Driver

  • Noobies
  • PipPip
  • 15 posts
  • Location: Halland

Posted 14 June 2018 - 12:37 PM

try changing your damper oil,
in the past have used other oils found 20/50 way to thick slows revving up down if that makes sense
always used three in one oil never had a problem

Right now I have 10w/40 in there, but maybe that's too thick as well... I've heard atf fluid is supposed to work, maybe I'll try that. What's three in one oil if I may ask? :)
it's that handy oil in a small white and black tin it's quite thin I use that gave more response or su oil ok

I'm swedish so we might not have that (or we do but in another kind of packaging), but I'll keep a lookout :)

I'm gonna try and change to a thinner oil and see if that works. That is definitely one of the things i've affected by cleaning out the carb so could very well be that it had thinner oil before.

#21 carbon

carbon

    Up Into Fourth

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 2,583 posts
  • Location: UK

Posted 14 June 2018 - 07:09 PM

Anton,

 

The standard damper oil supplied by SU Burlen is straight 20 weight. The closest multigrade equivalent is 5W30.

 

You will get differing advice on what damper oil is best for the SU. A lot depends on your driving style and your personal preference.

 

But as Ethel says, check that ignition and other basics are sorted before tweaking the carb settings. Also check carefully for any air leaks, including the plastic pipe to the vac advance, and that the vac advance can on the distributor holds vacuum OK.



#22 harrythehat

harrythehat

    Mini Mad

  • Members
  • PipPipPipPip
  • 258 posts
  • Location: wisbech

Posted 15 June 2018 - 06:33 AM

never had 5/30 in my days being an old wrinkly,

your local diy shop will stock an 3in 1 or oil similar



#23 alex-95

alex-95

    I am THE CLAMP MAKER

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPip
  • 5,620 posts
  • Location: Cornwall

Posted 15 June 2018 - 08:06 AM

As said the it'll need tuning after fitting the stage 1 kit, I would fit the standard air box back on rather than the K+N cone filter. I had one fitted and it ran a lot worse.



#24 unburntfuelinthemorning

unburntfuelinthemorning

    One Carb Or Two?

  • TMF+ Member
  • PipPipPipPipPipPipPip
  • 1,112 posts
  • Location: Bedfordshire

Posted 15 June 2018 - 08:39 AM

I don't understand why so many people dislike the K/N cone filter.  I had one with a stub stack inside fitted to a 998 years ago and after it went to Peter Baldwin to have the correct needle installed it ran beautifully. 



#25 Ethel

Ethel

    ..is NOT a girl!

  • TMF Team
  • PipPipPipPipPipPipPipPipPipPipPip
  • 22,936 posts
  • Local Club: none

Posted 15 June 2018 - 09:53 AM

I think the theory is cone filters reflect the shock waves from the valves closing more than the standard elbow and that disrupts the flow somehow. On a simpler level dyno testing has shown there's little in it and cones are a lot noisier, if that matters to you.

 

Since we've started a discussion on damper oil it's worth mentioning what it does - The carb uses the Bernoulli effect* to suck fuel up the jet, the piston needs damping to resist flutter. It follows more damping, i.e. thicker oil, means there's more resistance to piston rise, so more initial restriction of the venturi between the the jet and piston and consequently a bigger pressure drop to suck fuel through the jet faster. The oil provides the acceleration enrichment that more complicated carbs need a pump for. Thinner oil can have the opposite effect to what you might imagine by making the carb go lean when you put your foot down. It's a balancing act of oil viscosity, piston spring and needle profile that controls fuel metering, but the oil hardly has any effect other than when the piston is moving. When the engine is actually working to push your Mini along the road the engine can't rev up as quickly as it can out of gear so be wary of tuning the carb to a condition that's irrelevant.

 

*That's a proper mad scientist that is! 



#26 cal844

cal844

    Crazy About Mini's

  • Members
  • PipPipPipPipPipPipPipPipPipPip
  • 6,692 posts
  • Local Club: www.scottishmini.net

Posted 15 June 2018 - 09:53 AM

My engines run spot on with stage one kits. AAU needle, keep the spring that's in the carb and run on 20/50 oil, you may need to richen it up slightly.

#27 unburntfuelinthemorning

unburntfuelinthemorning

    One Carb Or Two?

  • TMF+ Member
  • PipPipPipPipPipPipPip
  • 1,112 posts
  • Location: Bedfordshire

Posted 15 June 2018 - 10:24 AM

I think the theory is cone filters reflect the shock waves from the valves closing more than the standard elbow and that disrupts the flow somehow. On a simpler level dyno testing has shown there's little in it and cones are a lot noisier, if that matters to you.

 

Since we've started a discussion on damper oil it's worth mentioning what it does - The carb uses the Bernoulli effect* to suck fuel up the jet, the piston needs damping to resist flutter. It follows more damping, i.e. thicker oil, means there's more resistance to piston rise, so more initial restriction of the venturi between the the jet and piston and consequently a bigger pressure drop to suck fuel through the jet faster. The oil provides the acceleration enrichment that more complicated carbs need a pump for. Thinner oil can have the opposite effect to what you might imagine by making the carb go lean when you put your foot down. It's a balancing act of oil viscosity, piston spring and needle profile that controls fuel metering, but the oil hardly has any effect other than when the piston is moving. When the engine is actually working to push your Mini along the road the engine can't rev up as quickly as it can out of gear so be wary of tuning the carb to a condition that's irrelevant.

 

*That's a proper mad scientist that is! 

Yes, Keith Calver says that about shockwaves.  As there's little in it I don't think there's anything wrong with them if you don't mind the noise.  I used to love the sound when I was twenty years younger but am not so bothered now!

 

Nice explanation about the accelerator pump effect.



#28 paul748

paul748

    Stage One Kit Fitted

  • TMF+ Member
  • PipPipPip
  • 73 posts
  • Location: Yorkshire

Posted 15 June 2018 - 10:53 AM

I recently fitted a minispares stage 1 kit (AAU needle) to my otherwise stock 998.

It ran OK but, because I had done the airbox mod (remove the air divertor thing and drill some 20mm holes in the bottom of the airbox) it was running lean.

Had it on a rolling road and I ended up with AAM needle. Car now runs great making just over 50BHP.







Also tagged with one or more of these keywords: engine

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

Mini Spares