23 replies to this topic

[Mini Manannán]

Is there any logic that can be applied to the lettering system?

 

I have a 1293 running a HIF44 with a BCE needle.  This needle has very likely been doctored at Slark in Bristol when the engine was rebored and put in my car though.  

 

  We don't have a  rolling road here so I'm trying to get my mixture fettled bit by bit.  I've recently been told of a old fella over here "he's been fiddling with SUs all his life".  He'll need a couple of needles either side of BCE to get started though.

 

i've been using Minty Lamb's compare-o-rama and have found that a BDL is just a little weaker through the range, I'm struggling to see a needle that is just a little richer through the range though?  Short of scouring a needle book is there a logic can be applied?

[Awamckay]

Have you tried using win su? Failing that give th guys at minisport, their techs seem pretty clued up on su needles when i had some queries.

[Mini Manannán]

I haven't, but only because I use Macs and Win SU is Windows.  Still, I'd like to know if there is a logic to the needles.

[Awamckay]

I'm also on mac now but will dig out my old laptop and have a look at the charts and needle codes and see if that helps you.

[A-Cell]

No there is no logic. Especially with the 100 thou needles.
The manufacturers of the power units during development take an existing needle and change it's shape to give the optimum fuelling at each engine load, throttle position and ignition advance on the dynamometer. This can be iterated several times during the development process. Once the "tuned" needle is finalised, it was issued for production and allocated a code by SU.

Pretty much what is done today by taking a stock weaker needle and reducing it in diameter at the various heights to achieve a correct, or probably more likely best compromise. Usually on a rolling road. Easier on a bench brake dynamometer. Still relies on skill and experience of the operator though.

Can be achieved on the road but more trial and error required and lots of plug chops!

If you want a richer needle than BCE try a 55.

[Mini Manannán]

Thanks for that A-Cell. I thought as much. All the evidence suggests it needs a weaker needle. I know it needs it but an RR session is an expensive ferry journey away.

[Leonrjohnson]

I have an HIF44 on a 970 S engine, and have been experimenting with MintyLamb in conjunction with an AFR meter. I started off with BDL needle.It was too lean at top end, so tried 

BDR  too rich over most of the rev range. BCE  too rich at bottom end, so I fitted a BBW and seems to be the right one for me.  I spent ages on MintyLamb site plotting all the HIF44 100 thou needles and comparing them, and narrowed my requirements down to the above needles. I am using a red spring. My engine has 32 degrees max advance at 5000rpm (123 distributor with no vacuum advance), and is running a 731 cam with K&N filter and maniflow with RC40 exhaust.I have 10:1 compression ratio and run 97 octane gas. I have an AEG163 head. I dont  run the engine over 8000rpm, even though it will go to 9000, but a waste of time as it flattens out at 8000.

 

 

 

 

                            

Edited by Leonrjohnson, 23 December 2014 - 12:59 PM.

[A-Cell]

Thanks for that A-Cell. I thought as much. All the evidence suggests it needs a weaker needle. I know it needs it but an RR session is an expensive ferry journey away.

One way you can tell if it is too rich (apart from plug colours), is if it starts easily and runs from cold with little or no choke.

In the first instant if you can get the weaker BDL needle, then fit it. Get the engine running right at idle. When fully warm and at an appropriate road location, Fit a clean (new) set of plugs, drive the car at full throttle full load, up a gradient then chop the plugs. By that I mean lift off, clutch in, switch off ignition, come to a halt and remove the plugs to check condition to establish not running rich. If ok then run with this needle for a bit, then check plugs again for overall colour.
Also see how engine performs through the range for drive ability, part throttle light load, Max torque lower rpm as well as full throttle across the revs. Etc. give it a go, good luck.

Also you will have some good info to tell your local SU expert.

[Mini Manannán]

It does start easily from cold, it never needed any choke when i first got it; I've fiddled with it to where it needs some but not much choke now.  I'm used to chopping plugs so I'll find the "appropriate location".

 

  I've just tried downloading CrossOver that is supposed to run a Window program on a Mac.  I failed miserably.  If anyone with WinSU would like to run my specs through it that would help?

[Steve G]

I sat for hours drawing the needles out as graphs on excel. Profile charts were available from Burlen Fuel Systems back then so I picked out the likely ones first. I haven't played with needles since so haven't tried the latest things like win SU. 

[Spider]

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.

 

I have an excel program that I've had for many years now. No, I'm not nearly clever enough to have written it, it was written by A.R. who ever that person is?   I think it's simply called SU Needles. It seems to be a little dated as there is certainly not the full spread of needle profiles in it, but profiles can be added fairly easy. It not only displays the needle profiles but allows you to compare profiles and it lists (extensively) 'options' starting from those that are closest match to those getting further away and where the differences are. Handy program, I use it fairly often.

 

I'm happy to make this available to the TMF, but I don't know how one goes about posting up a program, any pointers?

 

I've paid for a full working copy of WinSU, but I haven't yet received the unlock code (must chase that up), it really does appear a great little gadget. You guys who have used it, do you find that the suggestions are close enough or a good starting point?

[KernowCooper]

A BDP is richer from needle point 6.25 upwards than a standard BCE, and ever so slightly leaner needle point 6.25 down, but set the idle at 3% CO and try that as a base setting.

Edited by KernowCooper, 23 December 2014 - 08:30 PM.

[KernowCooper]

How big a file is SU Needles ? always put it on a upload/download site with a link to download it

[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.

 

I have an excel program that I've had for many years now. No, I'm not nearly clever enough to have written it, it was written by A.R. who ever that person is?   I think it's simply called SU Needles. It seems to be a little dated as there is certainly not the full spread of needle profiles in it, but profiles can be added fairly easy. It not only displays the needle profiles but allows you to compare profiles and it lists (extensively) 'options' starting from those that are closest match to those getting further away and where the differences are. Handy program, I use it fairly often.

 

I'm happy to make this available to the TMF, but I don't know how one goes about posting up a program, any pointers?

 

I've paid for a full working copy of WinSU, but I haven't yet received the unlock code (must chase that up), it really does appear a great little gadget. You guys who have used it, do you find that the suggestions are close enough or a good starting point?

 

I'm fairly sure a spreadsheet would upload to the My Media  section of the site though I don't know what the upload limits are.   Or as KC says, Drive or Dropbox etc would do it easily.

 

A BDP is richer from needle point 6.25 upwards than a standard BCE, and ever so slightly leaner needle point 6.25 down, but set the idle at 3% CO and try that as a base setting.

 

How do know all these KC?!  That sounds like a good starting point.  I'll set up an afternoon of plug chopping after xmas.

[KernowCooper]

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