13 replies to this topic

[luismx123]

Hey all,

Just done a few changes over the last few weeks. Ill start by chronological order:
-about 1.5 months ago I changed the timing on my stage 1 998 to the setting "F" on my 123ignition which is 34* at max advance and 22.5 at 2000rpm.
    Performance was improved a bit so I left it there

 

-about 2 weeks ago I "vizarded" my hs4 by cutting the butterly spindle and and aerofoiling the butterfly+spindle. 

   once again, performance went up, throttle was really responsive and got my 998 to rev to 6000 without any issues. Something my mini wouldn't manage on my daily test route on  some B roads behind my house. The AAA needle was slighty lean as there was more air flowing through so I turned the nut a 16th or 2

-today I swapped my old battered RC40 for a Maniflow center exit (small bore) and the smallbore LCB that was installed for a maniflow cooper freeflow. 
   and once again, performance has gone up a touch. Definitely feelable. sounds a plus too ;) but!!! something doesn't suit the current setup. Downlow its fine, at around 2000-3000 rpm theres a bit of a hole, then from 3.5 up to 6000 it revs like crazy. By feel, Id say its running slightly lean in the middle there and after adding 2/6ths richer, the hole went, but ofcourse the plugs go black at idle.

Whats on my mind is: where do I start now?
When do I know if the timing is correct? 
When do I look for a balance between carb needle, dashpot oil, spring? 

What is the norm: get idle to run smooth and mixture correct, then change/find needle to match rpms, then check mixture under acceleration to change dashpot oils/springs, and then set the timing?

 

I am looking for someone with an exhaust measuring machine thingy to find out whats going on mixture wise....I know its not best practice to do any of the above without measuring the exhaust gases...

 

 

edit: added image if anyones interested in seeing the bore diameter difference of the freeflow vs the smallbore lcb

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Edited by luismx123, 09 November 2019 - 05:08 PM.

[Spider]

In regards to sorting the fueling and ignition requirements yourself, with some test gear and loads and loads of time, along with hopefully keeping the peace in the neighborhood, you might get it close, but really, you need to take it off for a rolling road session. Take it to someone who will take the time and trouble to sort through it thoroughly and not just 'tweak' what's in there.

 

Generally, the first thing that is sorted is the Carb Spring. It's selected so at perk torque, the carb piston is at around 98- 100% open. Then the Carb Needle. These two wil likely be back and forth a bit until that sweet spot is reached. Then the ignition timing curve can be sorted with checks back to the Carb Spring and Needle again. Usually by this point though, the spring will be right, but a possible tweak in needle selection maybe needed. It's also worthwhile sorting the Plug Heat Range too.

[luismx123]

In regards to sorting the fueling and ignition requirements yourself, with some test gear and loads and loads of time, along with hopefully keeping the peace in the neighborhood, you might get it close, but really, you need to take it off for a rolling road session. Take it to someone who will take the time and trouble to sort through it thoroughly and not just 'tweak' what's in there.

 

Generally, the first thing that is sorted is the Carb Spring. It's selected so at perk torque, the carb piston is at around 98- 100% open. Then the Carb Needle. These two wil likely be back and forth a bit until that sweet spot is reached. Then the ignition timing curve can be sorted with checks back to the Carb Spring and Needle again. Usually by this point though, the spring will be right, but a possible tweak in needle selection maybe needed. It's also worthwhile sorting the Plug Heat Range too.

yea i totally agree. Problem for me is that the nearest RR is around 500km away and the "specialists" here in my area (area....pffft more like 200km distance) do everything by "feel". I think an exhaust tester would help me tremendously, but Im still lookin -.-

In regards to the piston height, how do i check this. Should I strap a gopro/my phone in the front of the carb mouth and run the engine on full throttle without the air filter to see how it rises? I have a gunson colourtune but a friend is borrowing it out atm.
I have 2 springs here. one is stronger and is currently installed. it was the original spring on the original HS4 my mini had. The vizarded was a spare hs4 i had lying around but was freshly rebuilt and came with a really soft spring....

[Turbo Phil]

If you have no access to a rolling road but you foresee yourself tinkering with the engine and further modifications in the future it will be cost effective to invest in a wideband AFR gauge and build a carb piston lift indicator. You can dial the fuelling in spot on using this combination.

Phil.

[luismx123]

If you have no access to a rolling road but you foresee yourself tinkering with the engine and further modifications in the future it will be cost effective to invest in a wideband AFR gauge and build a carb piston lift indicator. You can dial the fuelling in spot on using this combination.

Phil.

i like the sound of this. tell me more! 
what information would the piston height give me that is worth getting the tool? 

[unburntfuelinthemorning]

I have a wideband air/fuel ratio gauge.  I'll still be going to a rolling road as soon as possible but at least I know I'm not running wildly lean or rich in the meantime.  Doesn't help much with the ignition timing though.

 

[Mini Manannán]

 

If you have no access to a rolling road but you foresee yourself tinkering with the engine and further modifications in the future it will be cost effective to invest in a wideband AFR gauge and build a carb piston lift indicator. You can dial the fuelling in spot on using this combination.

Phil.

i like the sound of this. tell me more! 
what information would the piston height give me that is worth getting the tool? 

 

 

Here you go: https://www.terryhunt.co.uk/tips.html

 

 

 I haven't done  that myself yet but I'm in the process of fitting an endoscope into my (custom) airbox so a passenger can watch my needle going up and down

Edited by Moke Spider, 10 November 2019 - 07:46 AM.
Edit to fix link

[unburntfuelinthemorning]

Here you go: https://www.terryhun...picsb/pics.htm  I haven't done  that myself yet but I'm in the process of fitting an endoscope into my (custom) airbox so a passenger can watch my needle going up and down

 

Link isn't working

[Spider]

 

Here you go: https://www.terryhun...picsb/pics.htm  I haven't done  that myself yet but I'm in the process of fitting an endoscope into my (custom) airbox so a passenger can watch my needle going up and down

 

Link isn't working

 

 

I've just fixed it - sort of. Try the link again, then click on ' Detecting SU Piston Lift '

[luismx123]

ah so to make sense of it all, what I want to know is the height of the needle and the exhaust gas analysis (sorry I don't know what it's called) to see at what stage maly engine is running lean/rich and then cross reference this with the needle lift stages to find the right thickness/needle type?

[unburntfuelinthemorning]

Here you go: https://www.terryhunt.co.uk/tips.html

 

 

 

Fantastic, that's such a simple way to see piston height!  Nice needle polishing advice too.

[Mini Manannán]

ah so to make sense of it all, what I want to know is the height of the needle and the exhaust gas analysis (sorry I don't know what it's called) to see at what stage maly engine is running lean/rich and then cross reference this with the needle lift stages to find the right thickness/needle type?

 

 

Yes, you've got it.

For  "exhaust gas analysis" insert AFR - Air Fuel Ratio. https://x-engineer.o...-performance/  

[HUBBA.HUBBA]

Here you go: https://www.terryhunt.co.uk/tips.html

Fantastic, that's such a simple way to see piston height!  Nice needle polishing advice too.

Aldon sometimes have sometimes used one of those on mine when on the rolling road, well it's just a stick with a little flag on the end.

[Ethel]

In case it's not clear, the engine needs to be under load, so you'd have to be able to see your lift indicator while on the road. Another useful tool is the accelerometer on your phone.