SB needles in SU’s

[7tooZ]

Today I found a set of SB needles on my work bench that I had forgotten I ordered. Now I am trying decide Why?

Is anyone currently running these needles in their 240?
 

[siteunseen]

They came with my rebuild kit from ztherapy. My car runs very well them but honestly that's all I've ever had with a rebuilt motor and carbs. Nothing to compare against.

Somewhere on their website it says they're a good all around needle.

[Duffman]

I have run them in my L28 240Z, great AFRs on acceleration but a little rich on cruise (for me).  Randalla uses them on his L28 Z, is very happy with them.  I ended up going with the TF needles; leaner at cruise, still strong at WOT.

Edited May 6, 2020 by duffman

[7tooZ]

Interesting. Now it is beginning to come back. Last dyno run we did as a club I was running lean on WOT and someone said to try these. 
when we made it richer at WOT it was to rich at low speeds. Maybe I will wait till we can get to the dyno again and run both. 
thanks

[AK260]

So gents - I have a small unhealthy SU and needle work obsession and spreadsheets that do all kinds for me. Here is a plot of the “annulus” area (jet opening) with the needles discussed and the SMs that come with the ZT carbs.

I’m currently running KD but soon to test MC. But my engine is very modified.



Hope this chart helps with your deliberations!

[SteveJ]

5 hours ago, AK260 said:

So gents - I have a small unhealthy SU and needle work obsession and spreadsheets that do all kinds for me. Here is a plot of the “annulus” area (jet opening) with the needles discussed and the SMs that come with the ZT carbs.

I’m currently running KD but soon to test MC. But my engine is very modified.



Hope this chart helps with your deliberations!

Any chance of sharing the spreadsheet itself?

[AK260]

They came with my rebuild kit from ztherapy.   Somewhere on their website it says they're a good all around needle.

 

 

 Are you sure they weren’t SM needles? I may be wrong but I understood they shipped SM by default on all their rebuilt carbs. [emoji848]

 

 

 

I have run them in my L28 240Z, great AFRs on acceleration but a little rich on cruise (for me).  Randalla uses them on his L28 Z, is very happy with them.  I ended up going with the TF needles; leaner at cruise, still strong at WOT.

 Interesting how different engines can respond. I found the SB going very rich on my engine. Way too lean at idle if I was to dial them back. Doing this you get very hot idle which in my case is bad as queuing on the motorway or at tracks etc on a hot summer day is a regular occurrence.

 

I also suffer with horrible reversion around 3.1-3.5k rpm so the SBs just didn’t work with my car. There is a chap who posts on youtube with a stroker - he says they work very well for him. But I’m guessing a 3.0 high comp engine needs more fuel than my high revving 2.8 that is still building power at 6.5k rpm.

 

 

 

 

The thing with making a rich needle leaner to make it work better at WOT is that not only can you get lean idle but I found it ruins the quality of pickup and throttle response.

 

 

 

Interesting. Now it is beginning to come back. Last dyno run we did as a club I was running lean on WOT and someone said to try these.  when we made it richer at WOT it was to rich at low speeds. Maybe I will wait till we can get to the dyno again and run both.  thanks

 

 

  

So here’s the thing about dyno runs: my tuner spent 4 hours re-profiling my SM needles that came with the SU carbs. He told me it was going very lean at the top so he backed off and apparently I need triples to get the fuel flow. Actually, on the road at WOT I have never been above 12.8 AFR - why? Because to get to the same conditions he did I would have to be flat out in 4th at 125MPH. I may see that on a race track straight but never on the public road. Flat out in 3rd, uphill on the local motorway at 22:00 when it’s virtually empty is my free dyno time ;)

 

I used KV needles to prove that the fuel flow wasn’t an issue and could happily hit AFR 10s at the top end with jets only 1/2 mm down. So fuel delivery wasn’t the restriction, lack of a properly profiled needle was! Oh and an air leak on the carb insulators that went undetected at the time (but at WOT the effect of that would not be dramatic).

 

So began the obsession with needlework and simulating before buying. At £25 a set it very quickly gets very expensive to do it by trial and error.

 

The AFR meter / sensor was the best investment I ever made for tuning. Because I see real world AFR and carb response with different ways of using the throttle in normal driving not just simulated WOT.

 

 

 

Any chance of sharing the spreadsheet itself?

  

I would love to as I see this as open research for the Z community at large - but I am hesitant to share quite yet. It is currently not at all user friendly - you have to understand how it works to make it work. Once I have it all tied down then I fully plan to share.

 

However, in the meanwhile, I would highly recommend this site:

 

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

 

Drop in your reference needle, select a second needle and use the up/down scroll bar to quickly scan through profiles. It also allows you to download ooodles of profiles (which is where my unhealthy excel based obsession started)!

 

 

Again, I would urge any needle changing to be monitored with an AFR meter in real world driving.

Are all the engines mentioned above running well with SBs totally stock and on stock headers or something else?

 

 

[siteunseen]

You are right. They are SM needles. I looked at the receipt from ztherapy. Sorry about that. ?

[AK260]

You are right.

I hate it when that happens - it means I didn’t learn something new.

Although I also fear that years of marriage have taught me that it’s better to be wrong even if I am right! [emoji12]

[Randalla]

Very interesting AK260. This confirms my experience running 5-6 different profiles and monitoring an AFR meter I mounted on my steering column. My fresh built 2.8L motor has dished pistons (turbo block), an E88 head with port work and un-shrouded valves. I'm running a 276 lift, 480 duration cam and a 2 1/2" exhaust with straight through glass-pack. I used dished pistons to eliminate any possibility of detonation when setting total timing at 36 degrees, even though compression is down. With the SB needles the car runs very strong on the dyno, 180 hp at the wheels (roughly 220-230 at the crank). Torque was 225 ft. lbs. As a regular driver, the SB needles were too rich at lower RPMs for my liking. Couldn't stand the smell. I ended up defaulting to TF needles, which ended up being a compromise I could live with. Your chart shows exactly what I've experienced. Great to actually see it diagrammed. Thanks!  

Edited June 24, 2020 by Randalla
accuracy