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PostPosted: Fri Jul 13, 2018 12:14 pm 
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998cc
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I don't know what needle they supplied with the kit. It was changed by the tuner to a different one.

There was limited chance to open it right up this morning, but I did manage this one. Not very promising :(

Image

Maybe I do need to change needles...

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PostPosted: Fri Jul 13, 2018 9:39 pm 
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Get a metro turbo needle .Load the car up .Get a little file and make your own needle.Ive done it with wet and dry in a drill for twin SUs .I used a micrometer also.
File to make richer.Needles are cheap .You will get there


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PostPosted: Fri Jul 13, 2018 10:46 pm 
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Yep will do thanks Ian.

I gotta say, I've flirted with the idea of converting a Holley accelerator pump for use in an SU :idea: :shock:
Image
But I think at that point I'm better off switching carbies :lol:

By the way my attempts to get the carby apart to get the needle number have been stymied by parenting duties, but I haven't forgotten :)

Do I need to observe where the piston height is in order to find the right location to file? Or is there a particular section you think I should start?

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PostPosted: Fri Jul 13, 2018 11:38 pm 
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I found 4-600-ish grit wet and dry emery paper worked the best when modifying my needle - spin it up in a drill and gently grip it with the sandpaper

if you have a USB snake camera you poke up the intake, you can watch the piston position

this chart (example needles only!) shows where you'd want to take material off

Image

In theory you'd want to take it off in the area just cruise - imagine the piston jumping that first little bit as you open the throttle, but the damper holds it back. This is the point where you want the air across the bridge to draw a shitload of fuel all of a sudden, and keep drawing it as the piston keeps going up. So stations 5,6,7 ish

I had an SY needle when I still had an SU feeding my blower, I'd taken heaps off it in that range, it was OK, but still leaned out at sudden WOT - like I said, injection was a lot better, but still too many compromises

Was a long time ago, but a mate of mine suggested finding an SU copy from something like a Mazda 808 (not sure what car, but that's what I have in my head) that is nearly the same, but has an accelerator pump

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PostPosted: Sat Jul 14, 2018 7:55 am 
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Fantastic thanks Simon. I do have a snake camera to double check. I'll get filing. I have a spare Metro Turbo needle so I could experiment with that. And/or buy another similar to my existing one but with finer dimensions at that section of the needle and go from there.

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PostPosted: Sat Jul 14, 2018 9:48 am 
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I pulled apart the Metro Turbo HIF44 I have (NOT the one currently on the supercharged 1275).

Image

The turbo unit has a BDL needle

Image

This is the needle in the car that I am tuning - a BCF needle

Image

And here's the info on these needles from the WinSU program - I just paid the 20 bucks to use it myself as I think it'll come in handy.

BDL from Metro Turbo carb
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BCF from current supercharged setup
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Of note is that they are already the 0.100" needle. I think I'll find a needle with richer early to middle section and buy that and tinker from there.

And just out of interest, here is the damper piston - less play in this one than on the one in the HIF44 on the car at the moment.

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PostPosted: Sat Jul 14, 2018 10:23 am 
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I've looked through the 0.100" needle list plots and sought out ones that have the same high rpm needle profile but with smaller early to mid profiles. Here's the list I've compiled of possibles that I'll go through in greater detail:
BDK
BDP
BFC
KK
KS
KV
MC
RA *
RB
RC
RE
RI
SS
SY
SZ
ZG

For example, here is the comparisin between the existing BCF profile and the RA needle.

Existing BCF needle

Image

Possible replacement RA

Image

Do you reckon that profile change is in the right sort of area? Advice welcome. I might grab maybe one of the RA or similar and also a second BCF needle so either the new profile will be better or if not, I'll start from the known quantity of the BCF.

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PostPosted: Sat Jul 14, 2018 11:04 am 
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the 2 letter needles are for fixed dampers, 3 letter needles are springy

you should just richen up the BCF needle a bit, it has a sudden reduction in diameter after station 6, I reckon you should basically extend that back to station 4. Seriously, it'll take you 30 seconds

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PostPosted: Sat Jul 14, 2018 11:51 am 
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Alright, will do. I'll post the AFR trace after the mod. I'm a bit scared that I'll munt the needle since this is a daily (ish) driver (well about 3.5 kays trip 3 times a week to drop the boy off at daycare :) ). But if I take it slowly I'm sure it'll be fine and would run well enough to do taht run.

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PostPosted: Sat Jul 14, 2018 2:13 pm 
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Looks like it might be on the right track with the needle sanding, I took just a small amount off here - at the 5,6,7 area shaded here (and a little more towards the number 4 position too)

Image

and the trace...

Image

It looks like it's not clipping at the 18:1 plus mark like it was before and nudging down towards 17 or 16:1. More to come off, just doing it slowly.

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PostPosted: Sat Jul 14, 2018 2:56 pm 
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You can change the setting in winsu to show richness versus taper.It was better for me anyway.
At low airflow coming off idle where I had problems it was real critical.
At higher flow it is far less critical how much you take off.
My Cooper S has 286 kent cam modified head with silly big ports and has a modified BF needle by two in 1.5 inch sus


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PostPosted: Sat Jul 14, 2018 3:53 pm 
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Ian_B wrote:
You can change the setting in winsu to show richness versus taper.It was better for me anyway.
...


Thanks, there's a better comparison table than I was using too that I just found.

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PostPosted: Mon Jul 16, 2018 6:20 pm 
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I think I'm heading in the right direction. I've posted some scatter plots below, showing data from full test drive sessions. It shows AFR reading for various manifold pressures. I think it bettter shows the result of multiple pulls rather than one example pull like I've been posting before.

Here's data from a test drive from several modificattions ago...

Image

Then the next test drive data set is from after the first needle profiling work. Note that the 'hole' in the top right of the scatter plot is growing - ie there are fewer data dots in the mid-range boost and high AFR section, suggesting some improvements when immediately on the throttle.

Image

And then after some further needle profiling. I worked further down the pointy end. Note the hole is growing bigger. and the hole is growing twoards the high boost area - ie fewer high AFR data points in the high boost area.

Image

So I'll do a bit more of that profiling including a little more towards the pointier end of the needle.

One thing to note though, these are prettey small sample sizes, about 5 or 6 WOT pulls. So I'm taking the data with a grain of salt, but it does look like its making progress. The low AFR section is growing though, as I richen up the needle, there are 11.5:1 data points in the mid and hi boost area now, but I guess that's the trade-off of modifying the needle?

Here's an example pull from teh last test run session so you can see the improvements in the trace...

Image

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Last edited by Morbo28 on Mon Jul 16, 2018 6:53 pm, edited 2 times in total.

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PostPosted: Mon Jul 16, 2018 6:46 pm 
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Great its working out.Not sure I can read those doctors scans though :)


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PostPosted: Mon Jul 16, 2018 7:25 pm 
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Ian_B wrote:
Great its working out.Not sure I can read those doctors scans though :)

Thanks, yeah fair enough I've been playing with the data to help make sure I'm on the right path.

Basically each dot is a single piece of data, showing that it received a signal at x PSI and x AFR. If you look at the vertical line of where 4psi is, as I made the modificatiosn the data dots moved from 18:1 AFR down to a maximum of about 16:1 AFR for those times that the engine is at 4psi manifold pressure.

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