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Home > FAQ / Knowledge > A guide to polishing HIF needles --Edited July 2008--

Turbo Tel

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Delaware, USA

Latest update.

The BDD#2 needle seemed OK but it was hitting 11 AFR which is a bit rich for my liking, with the adjusted avonbar it was still abit rich and I was still seeing leanout in top gear. However when I hold the throttle open just enough to get boost this one leans out like the others. I sat down and theorised what was going on. I came up with the fact that in 1,2,maybe 3 gears the piston is always lagging a bit so It never actually makes it to the highest station in the short time it has in each gear, top gear however gives enough time for the piston to catch up. when it leans with partial throttle boost its at station 9 So Maybe I went Overrich on stations 7,8 and from 9 down its lean.

I love it when a theory works out. I repolished the BDD#1 needle and this time left 6-7 a bit leaner but richened up 9-12 and this needle is nice! going up the gears is at 12, less leanoff with part throttle full boost, and cruise is great all the way to 80mph at 13.5-15.

I may try some 15wt oil just to see what happens but I'm very near now..

Edited by Turbo Tel on 25th May, 2008.

website:- http://www.terryhunt.co.uk


Turbo Tel

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Final?? Update.. I bloody hope so!!

Still fighting the balance between WOT in lower gears and the leanoff I am seeing if I hold the throttle open just enough to get boost.
I can eliminate the leanoff but if I do the WOT mixture gets too rich, remember thats using the same spots there because the oil retards the piston when I floor it but not when I hold a steady throttle. In both cases its stations 8-10.

It seemed to me that the only way to change this relationship was to use thinner oil, I added 15-40 oil and repolished the avonbar needle to make it richer from 6-12. This was better but still lean on the part throttle so I repolished BDD#2 to go even richer and used 10-30 oil. I Think thats IT!! No leanoffs at part throttle with boost, pickup is great, WOT is at AFR of 12. I had already set this ones cruise so Its a good'n and I can get back to some semblance of a normal life without obsessing over this damn needle!!

OK so heres my final 3 needles and a standard BDD for reference.. pretty alarming how much I have shaved off these isnt it?? Keep in mind that the Avonbar and BDD#1 have not had the cruise set yet hence them being leaner on stations 1-4


Edited by Turbo Tel on 25th May, 2008.

website:- http://www.terryhunt.co.uk


Star Mag

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Leicestershire

I have been polishing my own needle this week and i am finding the same problems that you have experienced. i was using th avonbar 12psi needle and found this to be lean in 1,2 and 3rd gear and polishing from station 6 onwards as you have suggested has cured the problem! This is a cracking post with loads of useful info! NICE ONE! :)


robert

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uranus

fascinating tel thanks for sharing.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM


Tom Fenton
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Great info Tel.


On 29th Nov, 2016 madmk1 said:


On 28th Nov, 2016 Rob Gavin said:
I refuse to pay for anything else


Like fuel 😂😂


TurboDave16V
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very good info - especially the oil viscosity!

Which spring was used in the final tests?

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY



turbominivanman

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Thank you very much Terry.

This is fascinating stuff.

I'm having lean out from cruise at the mo and as I'm off to Slark for a setting up session next week the advice will undoubtedly be very handy, albeit with some tailoring for my setup.

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
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Tom Fenton
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I've just topped this thread to keep it prominent as I'm sure many people will find it very useful.


On 29th Nov, 2016 madmk1 said:


On 28th Nov, 2016 Rob Gavin said:
I refuse to pay for anything else


Like fuel 😂😂


Turbo Tel

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On 26th Jun, 2008 TurboDave said:
very good info - especially the oil viscosity!

Which spring was used in the final tests?


I am on the 12oz now but 8 is also OK just slightly different. I am also planning to re-visit the leanoff pipe issue.. I'm thinking that maybe thats why I see the leanoff at part-throttle/full boost and I currently have some comprimises to cure that.

Only way to find out is to start again with the leanoff pipe clamped, I'm waiting for some more needles from Burlen and will update this post when I have them in.

website:- http://www.terryhunt.co.uk


fab

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completely helpfull , thanks Terry,

I'm keeping on this one as I still have my transition to boost way lean , making a very frustrating hesitation at 1/2 ; 3.4 throtlle from vaccum to boost
lambda showing 20 afr


Turbo Tel

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On 5th Jul, 2008 fab said:
completely helpfull , thanks Terry,

I'm keeping on this one as I still have my transition to boost way lean , making a very frustrating hesitation at 1/2 ; 3.4 throtlle from vaccum to boost
lambda showing 20 afr


Be warned.. Once you get into this stuff it takes your life over.. so many variables, so many compromises.. I think I am starting needle number 8 now!!

Once I have done the needle for the clamped bypass tube I plan to rewrite the first two posts with my latest info and add more about the piston lift indicator as its great at nailing down which station you are using when it leans off.. Also I have made a small "jig" to hold the needle when measuring which makes the measurements more repeatable.

website:- http://www.terryhunt.co.uk


fab

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I'm more than warned, completely nut should I say, that's ten years now and still have plans and ideas to work .......


Turbo Tel

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OK I updated the first two posts with my latest info.

I have decided that blocking the leanoff pipe is the best way to go as it eliminates the part throttle leanout I was complaining about and also the needle needs less changes. Here are my latest no leanoff pipe needles



1a was fine but stations 4-5 were too rich on the BDD right from the start. So with 2a I polished stations 1-2 until 4-5 were down to an AFR of around 13.5. How it works is that When you polish 1-2 the idle setting gets rich, you reset the jet higher to get the idle correct and this adjusts the whole profile to be leaner. Its very sensitive!! 0.01 was enough to swing the AFR quite a bit, then I had to polish 3 a lot to get it back

Heres how the polishing went..

NEW BDD = 2=lean 3=ok 4=rich(12) 5 =rich(12) 6-12 lean

4 and 5 are rich so I need to adjust the idle point (1-2) to bring them down

0.02 off of 1-2
2=leaner 3=lean 4-OK 5=rich12.5 6-12 lean

adjust 1-4 0.01 to get 5 down
2-3-4=lean 5=OK
adjust 2-4 0.01 to get them up
2=ok 3=lean 4= lean
adjust 3-4 0.02
3=lean 4=ok
adjust 3 0.01
1-5=OK

at this point I know 6-12 need to be richer so I set them 0.02 above the previous needle.


A ll looked Ok, a little lean 6-12. there was a little hesitation
but before I fixed that tried 15w oil not much different so set 6 down another 0.01

Finally I dialled in 7-12 one at a time to get 13 opn the AFR, in real world use this gives me around 12.5.

Edited by Turbo Tel on 13th Jul, 2008.

website:- http://www.terryhunt.co.uk


TurboDave16V
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I don't know how many hours you've spent perfecting this - but you are the needle Guru IMO.

:)

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY



Turbo Phil

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Lake District

Indeed, excellent work. I thought i spent ages doing mine, clearly not compared to you ! :)

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Turbo Tel

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I took the car out for a spin in the freezing cold today.. The mixtures are a lot different. I theorised earlier that I may need to use thinner oil in the dashpot during winter because its colder and the oil will be thicker.. That seems to be wrong.

It seems that the biggest factor is that with the air being so dense (and full of oxygen) when its cold, the mixture leans off quite a lot. I found my perfect summer settings were not so good in the winter even though I had reset the idle mixture to suit. There was still quite a lot of leanoff when I accelerated.

W40 oil in the dashpot though seems to have settled things down a bit and its acceptable now, My car is not going to be used much in the winter so thats all I intend to do for now..

Terry

website:- http://www.terryhunt.co.uk


joeybaby83

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tel im hooked!!

ive been thinking about this recently in respect to NA engines.

im hoping that the piston lift is directly proportional to the depression at the bridge/dashpot vac?

if this is the case, could you not rig a vac gauge to the dashpot, and calc dashpot vac to piston lift/needle station?

and thus map afr readings to vac readings/needle stations easily on the move?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"



Turbo Tel

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Delaware, USA


Yes, in theory but you will have to work out how to calibrate it, i.e what depression equals how much lift..then if you change the spring you would have to calibrate again, so you would probably have to make a lift indicator to do that.. but having it mapped electronically would be nice..

Someone else was looking into that, but they were talking about looking at the pressure below and above the piston as it was a turbo..

Edited by Turbo Tel on 10th Jan, 2009.

website:- http://www.terryhunt.co.uk


gr4h4m

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Chester

great guide. interestingly I was thinking that the outside temps can make a big difference with my car I have also found a needle which I think is a bit closer to to my setup of
998 - 12g295 1.5 rockers 8.7:1 8-10 psi supercharged sc12

A BCG needle I have also shrunk your pic so when it prints is about correct size for a needle.

Thanks for all of this info.
Station No BCG BDD
1 0.0990 0.0990
2 0.0950 0.0962
3 0.0914 0.0937
4 0.0886 0.0907
5 0.0837 0.0850
6 0.0786 0.0795
7 0.0736 0.0753
8 0.0665 0.0720
9 0.0582 0.0694
10 0.0493 0.0673
11 0.0414 0.0653
12 0.0331 0.0635
13 0.0331 0.0618
14 0.0331 0.0602
15 0.0331 0.0585
16 0.0331 0.0570

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!


psimini

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the time and study put into this chart is awesome. top job....

na engine + turbo + boost = ya hewwww


Brett

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cant praise this guide enough, cheers for sharing :)

Yes i moved to the darkside *happy*

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Jay#2

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Northern Ireland (ex AUS)

Pffff, this needle polishing business is crazy! My latest needle is pretty good but it leans out for a second if you snap the throttle open quickly. Should I try thicker oil to get more of a accelerator pump effect?

This is a great write up though! Theres no way I'd even try doing this without it.

On 7th Nov, 2008 Nic said:
naeJ
m
!!!!!!sdrawkcab si gnihtyreve ?droabyekym ot deneppah sah tahw ayhwdd


Turbo Tel

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Delaware, USA

Yup, its can get to be an obsession.. I'm on the wagon at the moment, havent touched one for a year now!!


Thicker oil is the best bet for that, but I would worry if you are getting a long way from 20 weight.. 30wt or 40 but not much more.. remember come the winter and the extra oxygen in the cooler air you will probably need something even thicker..

website:- http://www.terryhunt.co.uk


Jay#2

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I have managed to keep the 10W oil but tweek the needle profile to richen up off boost acceleration. I think I am about 80% there so that's good enough for me!

On 7th Nov, 2008 Nic said:
naeJ
m
!!!!!!sdrawkcab si gnihtyreve ?droabyekym ot deneppah sah tahw ayhwdd


Turbo Tel

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Nothing wrong with 20wt, thats the standard SU oil weight.. It will help, I would try it..

Terry

website:- http://www.terryhunt.co.uk

Home > FAQ / Knowledge > A guide to polishing HIF needles --Edited July 2008--
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