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HIF44 tuning question
https://www.ausmini.com/forums/viewtopic.php?f=2&t=97480		 Page 1 of 3
Author:  Morbo28 [ Wed Jul 11, 2018 5:22 pm ]
Post subject:  HIF44 tuning question
Hi everyone,

I'm running a suck through HIF44 setup on the supercharged engine. Runs superbly as far as power and driveability. However when you look at the AFR trace, it looks like it is severely leaning out when you transition to full throttle - past 16:1, often up to the wideband's sensing limit of 18:1. At its worst it can have a slight stumble in revs, but mostly not.

I have replaced the yellow mid-strength dashpot spring with the heaviest green spring. I have put slightly heavier dashpot oil in there. I could go even heavier as a trial. I just took this trace this afternoon after that change.

Image

I am wondering if I am at the limit of what I should be expecting from an SU? given the supercharger setup, it can go from full vaccuum to drawing enough air to create instant boost (anywhere up to 9 psi max) very quickly. I'm wondering if something with an accelerator pump like a Webber would be better suited. Or even fuel injection. Is it a common wideband error perhaps.

Any people experienced with tuning who might have ideas how to get rid of this lean spike? Or thoughts on what you'd do in my situation.
Author:  Ian_B [ Wed Jul 11, 2018 5:43 pm ]
Post subject:  Re: HIF44 tuning question
I had a Holden 6 suck thru 1.75 cd stromberg
The needle supplied went real thin. Was custom called a Z1JA.
Have you tried filing a flat in the needle at the point where it is lean.
Is the fuel supply keeping the float bowl full under full load.
Reccommended mods for the Holden was larger diameter fuel line from tank and angled drillings in the needle and seat to increase flow.
Probably doesnt apply to a mini however.
I would look at 100 thou jet and needle profile.
Author:  Morbo28 [ Wed Jul 11, 2018 5:50 pm ]
Post subject:  Re: HIF44 tuning question
Hi Ian, thanks for the reply.

I think the fuel float level is fine - it has a spacer installed to increase capacity. And the mixture richens up after a second or so after I hit the accelerator. But I will double check the float level in case I've incorrectly ruled that out.

I haven't messed with the needle itself. I had it dyno'd by an experienced tuner in Sydney recommended by the engine builder. Maybe I'll buy a second needle to mess with and I can always reinstall the original one.

I will research the 100 thou jet and needle profile you mention, I've not come across that so far.

I appreciate the info thanks :)
Author:  Ian_B [ Wed Jul 11, 2018 6:25 pm ]
Post subject:  Re: HIF44 tuning question
What needle you running.I have winsu program Can have a look for you
Author:  Morbo28 [ Wed Jul 11, 2018 7:13 pm ]
Post subject:  Re: HIF44 tuning question
Ian_B wrote:
What needle you running.I have winsu program Can have a look for you
Hmmmm actually I'm not sure off the top of my head. When next in the shed I'll have a look, I've been planning to check that out...

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Author:  Ian_B [ Wed Jul 11, 2018 8:12 pm ]
Post subject:  Re: HIF44 tuning question
The taper on the needle combined with the spring is your mixture curve.
As long as the supply dont run out.
Let me know I have lots of experience with su needles and not just mini
Author:  s-c1293 [ Wed Jul 11, 2018 9:21 pm ]
Post subject:  Re: HIF44 tuning question
I had the same problem with the three Supercharged Minis I’ve set up.
What I do to reduce it, is to fit a small washer between the damper piston and the circlip on the end of the damper rod.
This limits the pistons movement to richen initial throttle response.
If you can’t find a small enough washer, you can cut the top flange off a 1/8” pop rivet and use that.

Image


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Author:  Morbo28 [ Wed Jul 11, 2018 9:39 pm ]
Post subject:  Re: HIF44 tuning question
Ian_B wrote:
The taper on the needle combined with the spring is your mixture curve.
As long as the supply dont run out.
Let me know I have lots of experience with su needles and not just mini

Thanks Ian, will do, much appreciated. I'll get onto that tomorrow and get back to you!

s-c1293 wrote:
I had the same problem with the three Supercharged Minis I’ve set up.
What I do to reduce it, is to fit a small washer between the damper piston and the circlip on the end of the damper rod.
This limits the pistons movement to richen initial throttle response.
If you can’t find a small enough washer, you can cut the top flange off a 1/8” pop rivet and use that.

Well bugger me, that sounds like a mod worth trying! Thanks for taking the time to post that tip, I'll give that a crack!!
Author:  simon k [ Thu Jul 12, 2018 3:01 pm ]
Post subject:  Re: HIF44 tuning question
how much does it reduce it Jeremy? makes it a bit better, or nearly gets rid of it completely?

it's still simply due to the lack of a throttle pump in an SU, and trying to get a decent squirt of fuel through the blower without it falling out of the air...
Author:  Morbo28 [ Thu Jul 12, 2018 6:28 pm ]
Post subject:  Re: HIF44 tuning question
Simon, I'm interested in Jeremy's reply too. I think theoretically it will have some effect but not totally eliminate it, but I'll be able to give you solid data tomorrow in the form of an AFR trace.

My damper piston has quite a bit of play up and down on the damper rod, so it would seem to make sense that no matter how thick the oil, the (big) piston can move that amount before the oil slows it down. Maybe that'll make the difference...

In hindsight Webber with accelerator pump or fuel injection may have been the way to go...who knows, maybe this'll work. I'm going to throw thicker oil at it too as a final trial after this piston mod.

But btw I don't think I've had an issue keeping the fuel in suspension through the supercharger. Eg idling is fine and that would be less airflow than under the conditions that I'm finding it problematic.

I'll also post the needle number Ian.
Author:  simon k [ Thu Jul 12, 2018 7:59 pm ]
Post subject:  Re: HIF44 tuning question
nup... the idea of putting fuel through the blower, then turning this way and that to get into the inlet valves is fundamentally flawed

I got rid of the leaning out under sudden WOT with 2x530cc injectors, made it idle and run nicely by staging them - AFRs were probably as good as it could get, but there was still fuel puddling, still 100°+ intake temperatures when the water wasn't going, just too many compromises....

maybe it works on V8s because they have gravity helping the fuel down into the ports where it can sit on the back of the valves - I don't think our motors can do it
Author:  Morbo28 [ Thu Jul 12, 2018 8:40 pm ]
Post subject:  Re: HIF44 tuning question
Ah okay interesting!

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Author:  s-c1293 [ Thu Jul 12, 2018 8:57 pm ]
Post subject:  Re: HIF44 tuning question
On my car, and the other Supercharged engine i built (both with custom needles, HP Performance 1040 Superchargers and Megajolt ignition), it has eliminated this initial lean out condition.
The other car I set up (with BDD needle, SC12 and 123 ignition with boost retard) still has a very slight lean out, but is so much better than it was.
All 3 carbs are HIF44s with yellow springs and 20w/50 oil.
I have just fitted a larger 1050 Supercharger on my car, and am now going through the joys of setting up another needle again :(
Morbo, it will be very interesting to see how your car responds tomorrow.
Author:  Morbo28 [ Thu Jul 12, 2018 9:27 pm ]
Post subject:  Re: HIF44 tuning question
Thanks for the extra info Jeremy much appreciated!

So interesting that you're running yellow spring and 20W50 weight oil. Looks like I've been chasing my tail there, given your experience and given my own experience - it hasn't changed my lean out issue at all!

You're running HP Performance superchargers - that's what I'm running, the 1050. So when I get the needle details for you that might cut out some of your tuning headaches to get you in the ballpark. It's a 1310cc 9psi max boost, with head and valve mods.

So an update, fresh in from the shed...here's the range of travel that the damper piston had on the damper rod.

Image
vs
Image

I couldn't find an appropriate washer in a quick drop in to supercheap, so I took your advice and used rivets :D Drilled out and shaved down to ensure no rubbing on the walls to score them (though the rivets are quite soft aluminium anyway).

Image

and here's the spacers added and secured.

Image

By the way I chat with Hans from HP Performance from time to time, so if this works, I'll pass it on to him so he can consider doing that mod standard with his kits.

My driveway runs by my 3 year old's bedroom so no testing til tomorrow sorry! I'll be trying to keep my expectations in check until then.

Edit: Looking at your damper piston and rod, looks like you may have had less play in yours. A quick google image search shows dampers with much less play than mine. Such as below

Image

Edit 2: Also interesting is this article... http://mgaguru.com/mgtech/carbs/cb105.htm
Author:  s-c1293 [ Fri Jul 13, 2018 9:46 am ]
Post subject:  Re: HIF44 tuning question
It will be very interesting to find out which needle they supplied with your kit.
The BBC needles that came with my kits are way too lean in the mid section, this is the section that controls cruise and initial acceleration, which is where the biggest problem is.


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