Proper Carb Needles
Created by: Smithengineered
Orig. Posting Date | User Name | Edit Date |
Nov 7, 2019 03:18PM | 1963SV2 | |
Nov 7, 2019 09:27AM | Smithengineered | |
Nov 3, 2019 01:55PM | katmaster | |
Oct 26, 2019 01:30PM | 66Cooper'S | |
Oct 22, 2019 07:09AM | CooperTune | |
Oct 21, 2019 06:04PM | 66Cooper'S | |
Oct 21, 2019 04:45PM | malsal | Edited: Nov 4, 2019 09:23AM |
Oct 21, 2019 12:47PM | Spitz | |
Oct 21, 2019 08:40AM | Smithengineered |
Total posts: 1716
Last post: Oct 18, 2020 Member since:Oct 18, 2011
|
Cars in Garage: 0
Photos: 0 WorkBench Posts: 0 |
"....HS2’s might struggle a little on this tuned engine..."
Depending on how well the mods originally mentioned were done, this is a distinct possibility.
But you have to remember that the determinant controlling how much you can get out of your engine is how air you can get through it rather than the amount of fuel.
The needles are there to provide the "right" amount of fuel to whatever air flow the engine can achieve. Vizard provides good explanations as to the need to determine where the choke point is that determines the airflow through the engine. Only be opening up this choke point can you increase power .... and of course, as soon as you do this the choke point moves somewhere else.... and so on
IMO people tend to concentrate on the needle when tuning SUs and tend to ignore the spring... The 1.25" dimension is only nominal.. the actual bore is determined by the interaction of engine vacuum and spring strength. With the correct spring the carb bore will be completely open at WOT under full load.... Too much spring = a reduced carb bore = restricted air flow.. Too little spring = wide open bore = all the fuel possible ..without sufficient air flow..
This load+carb opening is why you can't really tune an SU without a dyno ... or as they used to do it with "plug chops" or more recently O2 meters (and a lot of unrestricted road
You can start with a recommended needle (and spring) and then go through as many variations on the dyno (that you choose to afford) until you get to the optimum. BTDT .. it took 3 set of needles before we decided enough was enough..
Cheers, Ian
Depending on how well the mods originally mentioned were done, this is a distinct possibility.
But you have to remember that the determinant controlling how much you can get out of your engine is how air you can get through it rather than the amount of fuel.
The needles are there to provide the "right" amount of fuel to whatever air flow the engine can achieve. Vizard provides good explanations as to the need to determine where the choke point is that determines the airflow through the engine. Only be opening up this choke point can you increase power .... and of course, as soon as you do this the choke point moves somewhere else.... and so on
IMO people tend to concentrate on the needle when tuning SUs and tend to ignore the spring... The 1.25" dimension is only nominal.. the actual bore is determined by the interaction of engine vacuum and spring strength. With the correct spring the carb bore will be completely open at WOT under full load.... Too much spring = a reduced carb bore = restricted air flow.. Too little spring = wide open bore = all the fuel possible ..without sufficient air flow..
This load+carb opening is why you can't really tune an SU without a dyno ... or as they used to do it with "plug chops" or more recently O2 meters (and a lot of unrestricted road
You can start with a recommended needle (and spring) and then go through as many variations on the dyno (that you choose to afford) until you get to the optimum. BTDT .. it took 3 set of needles before we decided enough was enough..
Cheers, Ian
Total posts: 14
Last post: Mar 11, 2021 Member since:Mar 14, 2019
|
Cars in Garage: 0
Photos: 0 WorkBench Posts: 0 |
Thanks for all of the replies! Been crazy busy at work lately. The carbs have AAA needles in them now. The carbs were new and have been ran very little since going on the car. I’ve been told the HS2’s might struggle a little on this tuned engine and that going to a HIF44 might be less of a headache. Hahaha
Total posts: 313
Last post: Nov 3, 2019 Member since:Jul 3, 2003
|
Cars in Garage: 0
Photos: 6 WorkBench Posts: 0 |
|
My 1275 engine Inno Mini Export With HS2s has AAP needles and that is what is listed for it. Joe Curto said the engine is more like a 1275 GT or AH Sprite and is why the needles are different from other Mini carbs.
I have an oxygen sensor and gauge.
I have an oxygen sensor and gauge.
Total posts: 3523
Last post: Jul 9, 2023 Member since:Feb 26, 1999
|
Cars in Garage: 0
Photos: 0 WorkBench Posts: 0 |
|
I checked this afternoon and find I am running V3 in mine.
Total posts: 4134
Last post: Oct 13, 2020 Member since:Oct 8, 2011
|
Cars in Garage: 0
Photos: 0 WorkBench Posts: 0 |
|
If compression is in the 10 to 1 region 5 or 6 should get you close. I find my O2 gauge is the answer to all my questions. Steve (CTR)
Total posts: 3523
Last post: Jul 9, 2023 Member since:Feb 26, 1999
|
Cars in Garage: 0
Photos: 0 WorkBench Posts: 0 |
|
Quote:
Originally Posted by Smithengineered
Anyone have recommendations on proper needles for hs2 carbs on a 1310, ported/polished head, cam, roller rockers, lightened flywheel, exhaust? Trying to dial in the fuel on my Innocenti with a colortune kit. Seems to be lean at idle and super rich under acceleration. I have yet to take the needles out to see what’s currently in there.
Look up what was used on the 1275 - they list a weak/standard/rich needle ( as noted above /M/AH2 )
Check the cam specs and see which needle they recommend for their cam.
Check the specs on the head - what do they recommend for their head.
Which rockers - standard or 1.5:1 ratio? there again what do they recommend.
Look at Vizard, "How to modify your Mini" where he goes over the spring/needle to use ( Red/AH2 )
When was the last time the carbs were serviced/rebuilt
Check the cam specs and see which needle they recommend for their cam.
Check the specs on the head - what do they recommend for their head.
Which rockers - standard or 1.5:1 ratio? there again what do they recommend.
Look at Vizard, "How to modify your Mini" where he goes over the spring/needle to use ( Red/AH2 )
When was the last time the carbs were serviced/rebuilt
Total posts: 8382
Last post: Jan 13, 2022 Member since:Feb 7, 2006
|
Cars in Garage: 0
Photos: 0 WorkBench Posts: 0 |
|
Check out mintylamb.co.uk there is a comprehensive list of needles there with a chart to compare them.
Joecurto.com in NY is a good source for harder to get needles.
Joecurto.com in NY is a good source for harder to get needles.
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.
Total posts: 13978
Last post: Jan 15, 2024 Member since:Jan 22, 2003
|
Cars in Garage: 4
Photos: 381 WorkBench Posts: 1 |
|
M is a standard 1275 needle and AH2 is the rich needle........so I'd use the AH2 as a starting point.
( or switch to twin HS4 or H4 )
( or switch to twin HS4 or H4 )
"Everybody should own a MINI at some point, or you are incomplete as a human being" - James May
"WET COOPER", Partsguy1 (Terry Snell of Penticton BC ) - Could you send the money for the unpaid parts and court fees.
Ordered so by a Judge
Total posts: 14
Last post: Mar 11, 2021 Member since:Mar 14, 2019
|
Cars in Garage: 0
Photos: 0 WorkBench Posts: 0 |
Anyone have recommendations on proper needles for hs2 carbs on a 1310, ported/polished head, cam, roller rockers, lightened flywheel, exhaust? Trying to dial in the fuel on my Innocenti with a colortune kit. Seems to be lean at idle and super rich under acceleration. I have yet to take the needles out to see what’s currently in there.