23 replies to this topic

[Spider]

I know it because I have the  SU Book "Needle Charts" and I spent a week profiling my custom needle, good little book shown every needle made

 

Only a week?  Goodness, you did really well!

[KernowCooper]

I had people standing on the flat out bits watching, here he comes again, but I did have a on board calibrated CO Meter to take readings to help out between plug chops, it made the cruse profile so much easier.

[Mini Manannán]

Thanks to this thread's suggestions I have 3 suggestions:

 

I'm only guessing but I reckon the BDP might be a tad on the rich side for top end?  We will see...

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[Dan]

I know it because I have the  SU Book "Needle Charts" and I spent a week profiling my custom needle, good little book shown every needle made

The needle charts are on SU's website, along with a whole host of info if you read the tuning documents for your type of carbs. They have the basic workshop manual type setting up guides but also more detailed pages.

[Mini Manannán]

Bhahaa,,,, as A-Cell has said, there is no logic.

 

Keep in mind too that you need to sort the dashpot spring too.

 

Basically the spring should be selected such that at peak torque the dashpot piston has risen to about 95 to 99% all the way up, you definitely don't want it reaching 100% before the engine reaches peak torque and you'll be loosing out a little on what the carb can do if it doesn't rise to that 95 - 99%.

 

After sorting the spring, then the needle can be sorted, and then check the spring suitability once again, but I'm sure that your SU man already knows this.

 

 

Back to the spring, because the 'round' throttle is turning in a cylinder it essentially becomes elliptical so it is an exponential curve, has anyone done a ratio for this?  Someone must have done!

[Mini Manannán]

 

I know it because I have the  SU Book "Needle Charts" and I spent a week profiling my custom needle, good little book shown every needle made

The needle charts are on SU's website, along with a whole host of info if you read the tuning documents for your type of carbs. They have the basic workshop manual type setting up guides but also more detailed pages.

 

 

I can see the needle book but they want £5.50 p+p to post a £3.95 book.  I can't any readable charts.

[Dan]

I think it's actually just a link to Mintylamb to be honest but it's there. I also seem to remember that the needle charts are in the back of the reference catalogue, as well as in the actual needle chart book, but the reference catalogue is free. I'll have a look if it's in the book when I get home tomorrow but I'm pretty sure it's all there. I know I've got them somewhere, and I've never bought the needle book itself.

[Spider]

 

 

Back to the spring, because the 'round' throttle is turning in a cylinder it essentially becomes elliptical so it is an exponential curve, has anyone done a ratio for this?  Someone must have done!

 

 

I think we may have our wires crossed???   The spring I was refering to is hat inside the carb dashpot (or bell)  eg:  http://minispares.co...|Back to search

 

 

Dan's referal to the SU Website is a good one

 

http://sucarb.co.uk/

 

but in regards to Needle Charts, apart from the book they sell, they refer you back to Mintylamb's (as Dan said)

 

http://www.mintylamb.co.uk/suneedle/

 

also excellent. I use this in conjunction with that program I mentioned to obtain the profiles that are not in it.

[Mini Manannán]

 

 

 

Back to the spring, because the 'round' throttle is turning in a cylinder it essentially becomes elliptical so it is an exponential curve, has anyone done a ratio for this?  Someone must have done!

 

 

I think we may have our wires crossed???   The spring I was refering to is hat inside the carb dashpot (or bell)  eg:  http://minispares.co...|Back to search

 

 

Dan's referal to the SU Website is a good one

 

http://sucarb.co.uk/

 

but in regards to Needle Charts, apart from the book they sell, they refer you back to Mintylamb's (as Dan said)

 

http://www.mintylamb.co.uk/suneedle/

 

also excellent. I use this in conjunction with that program I mentioned to obtain the profiles that are not in it.

 

 

Ah... It must be time for bed, I read 'torque' as 'throttle' Doh!  There must be a chart for % throttle opening out there though.