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 Posted: Jul 19, 2018 04:48PM
jeg
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Blue Potato - 

//browsemags.com/mini-magazine-may-1-2013/982-su-carburettor-tuning.html 

Don't know if you've read this article, but it's got some really GREAT information in it. 

For example, check out the paragraph on dampers - 

The peasants are revolting...          

"Gone with the Wind" - a brief yet moving vignette concerning lactose intolerance

 Posted: Jul 19, 2018 04:26AM
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US
I have mailed over a set of AH2 s since we live so close together. It only took three hours round trip last visit. I'm also confused as I have talked with AC Dodd about needles many times. And watched the videos of a hand drill chucked in a vise to spin needles. I did not know KD was hands on since his son in law took over the biz. Steve (CTR)

I like books and had a good collection of both SU and Weber info. Have a SU needle chart book at home and the shop. as well as the big SU book. I do comparisons on old scraps of paper. My O2 gauge has been the biggest help. O2 , EGT and vacuum are all helpful. With twins a Unisyn is a must. 

 Posted: Jul 18, 2018 06:00AM
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US
Quote:
Originally Posted by h_lankford
Quote:
Originally Posted by thebluepotato
There is no way to tell based on this what specific needle you have - you need to start with one (lets say M needle for now) and get on a rolling dyno in order to see what your A/F is at different stages on the RPM range. 
That " no way" may not always be true. I started with my 1275 "Stage 1" and going by butt dyno through BFY, BDL, too lean- BDK too rich ( soot all over back bumper) that this website's recommendation for "lightly modified use" BCE worked well. Then went to dyno and found it was good based on A/F ratio, BCE was what I needed. Slightly rich on low rpm end but that gave good driveability.

Howard's 2 carb set up and more advanced cam and state of tune may make for a different carb-tinkering experience.
At the end of the day, you cannot get an accurate reading of the optimal burn and HP/TQ for your modified mini engine.  Case and point - take a look at my before and after dyno run from two weeks ago.  This is a good example as to why it is critical to do it on a dyno to get the right idea of where you are. 

Before (red line): This was my first run with my mini where I assumed the car was set up correctly.  Ran great and had a needle that was recommended with no dyno runs or understanding where the A/F was.  This is not the right way to do it and was dangerously lean and lower power.

After (green line): after cross referencing needles and trying some and using others to make up the optimal A/F gap, we found the right one during the session - but you can clearly see that I am still running rich at tip in.  My pal and I are no cross referencing the 300+ needles to find one that can slightly lean out the mixture (i.e. going slightly ticker at top of needle) and keep the optimal A/F after 3k.  And will also be trying out a new dashpot damper (AUC8114) and possibly a different SU spring - again, looking at another dyno run to get that green line smoothed out.

So I do not side with the "read a book at pick your perfect needle" concept - unless you combine that with a couple hours on a rolling road to truly understand where the optimal power is.  This is the only way to know what needle to use.  Otherwise, you are guessing like I did on that red line you see above.

/// Basil - 1974 Mini 1000 /// THE BLOG: www.thebluepotato.net/blog

 Posted: Jul 18, 2018 03:57AM
 Edited:  Jul 19, 2018 04:57AM
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Quote:
Originally Posted by Scargo
Does anyone out there with more knowledge than me care to take a stab at making a recommendation for a needle selection for my street driven Sprite? Engine spec is: 1293cc Kent 276 cam 1.5 roller rockers 12G 1316 Smog head slightly ported Compression ratio approx 10:1 Header with single box exhaust Pertronix Dual HS2's w/ K&N single box air filter
Howard, Keith? Dodd was very good with helping Joe Schott on a needle selection when he built his 1293 engine. The end result was he took the needle suggested by KD and "fine tuned it" in a drill with some 2000 grit sand paper to get it where he needed it.
The air fuel ratio was spot on when he was done.

If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Jul 17, 2018 01:30PM
 Edited:  Jul 18, 2018 03:01AM
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Quote:
Originally Posted by thebluepotato
There is no way to tell based on this what specific needle you have - you need to start with one (lets say M needle for now) and get on a rolling dyno in order to see what your A/F is at different stages on the RPM range. 
That " no way" may not always be true. I started with my 1275 "Stage 1" and going by butt dyno through BFY, BDL, too lean- BDK too rich ( soot all over back bumper) that this website's recommendation for "lightly modified use" BCE worked well. Then went to dyno and found it was good based on A/F ratio, BCE was what I needed. Slightly rich on low rpm end but that gave good driveability.

Howard's 2 carb set up and more advanced cam and state of tune may make for a different carb-tinkering experience.

 Posted: Jul 17, 2018 06:17AM
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US
Quote:
Originally Posted by Scargo
Does anyone out there with more knowledge than me care to take a stab at making a recommendation for a needle selection for my street driven Sprite? Engine spec is: 1293cc Kent 276 cam 1.5 roller rockers 12G 1316 Smog head slightly ported Compression ratio approx 10:1 Header with single box exhaust Pertronix Dual HS2's w/ K&N single box air filter
There is no way to tell based on this what specific needle you have - you need to start with one (lets say M needle for now) and get on a rolling dyno in order to see what your A/F is at different stages on the RPM range.  This is done through a lambda or something similar.  It is only then where you will start to hone in on the right needle for the perfect mixture.

Just spent 5 hours myself a couple weeks ago and was astonishing what you can learn and dial in for the perfect needle.

/// Basil - 1974 Mini 1000 /// THE BLOG: www.thebluepotato.net/blog

 Posted: Jul 17, 2018 01:26AM
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I will have a go .... m needles 

 Posted: Jul 16, 2018 10:09AM
 Edited:  Jul 16, 2018 04:40PM
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Does anyone out there with more knowledge than me care to take a stab at making a recommendation for a needle selection for my street driven Sprite? Engine spec is:

1293cc

Kent 276 cam

1.5 roller rockers

12G 1316 Smog head slightly ported

Compression ratio approx 10:1

Header with single box exhaust

Pertronix

Dual HS2's w/ K&N single box air filter

 Posted: Jul 14, 2018 03:49PM
jeg
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Quote:
Originally Posted by tmsmith
Graham:
There is a replacement tool from the MK-1 forum.
It does require you to install Open Office as there is some programming that is not compatible with MS Office.

from a forum post:
In the meantime, if you have "LibreOffice" or "OpenOffice" on your computer,
you may be interested in this needle comparison tool:
(IT'S NOT DESIGNED TO WORK WITH M$ OFFICE)
//mk1-performance-conversions.co.uk/technical_carb.htm

Terry
The Mk1 'Needles' tool is far superior to both the MintyLamb and Teglerizer needle selectors in that rather than simply compare needle dimensions - which you can do yourself using a needle chart book and Excel sheet - the Mk1 'Needles' comparison tool compares the annular area between the needle and jet of your selected needles. 

There's also a function which allows you to lower or raise the jet and 'see' the effect change in annular area as a percentage, as with the usual compare a handful of needles, similarity recommendations and the ability to modify a 'test needle' for comparison (fx. removing 0.002" from position 5 of an AAA results in (x)% change from the standard dimension.

Using this tool, you can also compare 0.100" needles to 0.090" needles - as sometimes, with HIF carbs, one fits a larger jet to a smaller carb or vice versa. 

Ian presented this comparison tool to Berlen Fuel Systems last year or so and they were highly impressed.  I haven't spoken with Ian since the last revision, so I don't know if Berlen will be incorporating his work to their website.  Yes, I'm biased - I assisted Ian with some development opinions and quality checks, making the odd data correction and giving feedback prior to release.

The peasants are revolting...          

"Gone with the Wind" - a brief yet moving vignette concerning lactose intolerance

 Posted: Jul 11, 2018 06:50AM
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this might help

scroll down to taper selector section

//teglerizer.com/sucarbs/index.html

 Posted: Jul 11, 2018 06:42AM
 Edited:  Jul 11, 2018 06:45AM
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Howard
 - I just tried it and got nowhere also

does this one help any?


www.winsu.co.uk

this hyperlink does not work, so copy and paste

 Posted: Jul 11, 2018 06:03AM
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Does anyone have an update on this? I need to make a needle selection and I'm struggling with the Burlen site.

 Posted: Nov 10, 2017 02:42PM
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US
Story posted on that web site, now. Sounds like it will be resurrected.

 Posted: Nov 10, 2017 12:53PM
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Graham:
There is a replacement tool from the MK-1 forum.
It does require you to install Open Office as there is some programming that is not compatible with MS Office.

from a forum post:
In the meantime, if you have "LibreOffice" or "OpenOffice" on your computer,
you may be interested in this needle comparison tool:
(IT'S NOT DESIGNED TO WORK WITH M$ OFFICE)
//mk1-performance-conversions.co.uk/technical_carb.htm

Terry

 Posted: Nov 10, 2017 11:17AM
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US
Anyone know what happened to the "Minty Lamb" website for SU carb needle comparison graphs?
It was a great way to compare the hundreds of needle option when doing modified engines.
If anyone know how to reach the person who created it please let me know.

Graham 949-646-6404