Triple Mikuni Help

[madkaw]

Leon,

I guess my message box is full and I can't delete them.

 

s_finnerty1018@comcast.net

[madkaw]

I wish Todd would pop in on this conversation;)

[Leon]

Leon,

I guess my message box is full and I can't delete them.

 

s_finnerty1018@comcast.net

 

Email sent!

[madkaw]

Well I have decommissioned my Z for a good cause-I hope.

Leon, got a hold of Keith, and my E-tube with jets is on the way to CA.

I guess he will make a 3D model of it to beable to make new bleed pipes! Sounds like he hasn't seen too many Mikuni set ups since he was a bit suprised of the inner bleed pipe. If this is successful I will have to take both sets of bleed pipes to the dyno so we can see the results documented. Love to beable to see a flat AFR curve!  

[Leon]

Well I have decommissioned my Z for a good cause-I hope.

Leon, got a hold of Keith, and my E-tube with jets is on the way to CA.

I guess he will make a 3D model of it to beable to make new bleed pipes! Sounds like he hasn't seen too many Mikuni set ups since he was a bit suprised of the inner bleed pipe. If this is successful I will have to take both sets of bleed pipes to the dyno so we can see the results documented. Love to beable to see a flat AFR curve!  

 

Sweet! Let me know how it turns out.

[JMortensen]

I am reading "How to Build Horspower Vol 2" and Vizard gives a pretty detailed idea of what the different parts of carbs do, including the emulsion tubes. Made me think of this thread, you guys might check it out. He has suggestions for where the holes should be placed in the tube to change the mixture at different RPMs, etc.

[madkaw]

Thanks Jon,

 

I sent my emulsion tube off to Franck and he made a 3D model of it I guess. He made a suggestion that I followed. The suggestion he offered, suggested to me, that he doesn't know Mikuni carbs or that the operating principles are different then the Webers(which he seems to know a lot about). There was no improvement and it actually ran worse. Not bashing the guy at all, but it sounds like he is going many different directions right now-especially with the Webers. He said he thought there was too much volume in the e-tubes and we attempted to reduce that volume.

 

I'm not sure that I am going to persist to try and get that last percentage of a EFI drivability out of triples. The issue is not dangerous and will not cause any damage to the motor. With the right cam this might be a non-issue. The carbs idle perfect at 750 rpm every time and accelerate like triples should. AFR's are very good in almost all driving conditions. I plan on dynoing with the triples and then putting them on the market so I can pursue EFI. 

 

As far as the bleed pipe holes, I work with a guy that is a carb wizard and runs at 10 second Buick. I described my issue to him and he went straight for the bleed pipe holes. I thought about closing up a couple of the holes to see what happens, but I'm running out of good weather. Not sure if I want to do all the work to cater to my build when I am going to sell these off.      

[madkaw]

OMG-did I finally solve the transition issue!!!!!!!!!!!!!!!!!!!!!!!!

 

So what the hell, why not try something completely different. I took out my bleed pipes and loctited the top row of holes-that's it, that's all I did and no more stumble. My AFR's don't peg lean during mild tip-in like before. I might see 16 just for a second and that it settles back to the 14-15's. It is a DEFINITE improvement.  

I will need to pull out the bleed pipes again to make sure the red Loctite held under the fuel exposure, but I'm stoked

[Leon]

OMG-did I finally solve the transition issue!!!!!!!!!!!!!!!!!!!!!!!!

 

So what the hell, why not try something completely different. I took out my bleed pipes and loctited the top row of holes-that's it, that's all I did and no more stumble. My AFR's don't peg lean during mild tip-in like before. I might see 16 just for a second and that it settles back to the 14-15's. It is a DEFINITE improvement.  

I will need to pull out the bleed pipes again to make sure the red Loctite held under the fuel exposure, but I'm stoked

 

[madkaw]

Suprised none of the "pundants" of the triple world haven't commented on this!  It seemed like from responses to my thread that others have dealt with this too, but have never heard of anyone altering the bleed pipe.

I need to identify the fuel level in relation to the bleed pipe. Keith Franck at sidedraft central wants to include this in his 3D model to help explain the dynamics. Essentially I have eliminated some of the 'bleeding' off of pressure by closing some of the holes. This in turn boosted the signal from my venturi and helped draw from the main jet in a more timely matter. I guess the E-tubes on Mikunis are significantly bigger(volume) then Webers?  

[Tony D]

I wouldn't use red loctite, maybe some Devcon Aluminim or JB Weld...that should hold up on clean brass immersed in fuel.

 

This is what is required some times, look at the Weber Manuals and they have you tapering the throttle blade to tip in quicker, drilling transition holes, etc...

 

The emulsion tubes are no different, but most could mask it in OEM applications, probably not as demanding as yours. 

 

When you go custom, you may need to do that inside the carbs as well... It's probably why Weber has like a million of them, but Mikuini has like two....HAHAHAHA!

 

If it works, you can not argue with it, just note it for the next time and maybe save some time.

 

Now wait 25 years for the opportunity to pass it on to someone needing that bit of knowledge! 

[Xnke]

Don't use JB weld in a fuel environment...I hear about it "working just fine for years" all the time but it DOES dissolve in fuel and it DOES get soft and it WILL peel off eventually.

 

Just solder the holes shut with lead solder and call it good...an electric soldering gun and some electronics solder will do it with minimal clean-up following.

[madkaw]

The loctite seemed to be a good(maybe temporary) fix because it would be easy to drill out later. There is no room for anything as far as covering the holes. It has to be perfectly flush fill or the bleed pipe won't fit back in the E-tube. I need to check to see how it's holding up.

[madkaw]

I wouldn't use red loctite, maybe some Devcon Aluminim or JB Weld...that should hold up on clean brass immersed in fuel.

 

This is what is required some times, look at the Weber Manuals and they have you tapering the throttle blade to tip in quicker, drilling transition holes, etc...

 

The emulsion tubes are no different, but most could mask it in OEM applications, probably not as demanding as yours. 

 

When you go custom, you may need to do that inside the carbs as well... It's probably why Weber has like a million of them, but Mikuini has like two....HAHAHAHA!

 

If it works, you can not argue with it, just note it for the next time and maybe save some time.

 

Now wait 25 years for the opportunity to pass it on to someone needing that bit of knowledge! 

 

 

 

I guess not too many to benefit from the info:)

 

I guess my fix is the same as your suggestion of smaller boost venturi's?

[Tony D]

Sorta, one amplified the signal so the aeration is different.

 

And that is a good point, the parts are brass, soldering them is pretty easy... I'd go with soldering over JB weld... I'm in a third world country and have been epoxying a lot of stuff recently and don't have access to a crack pipe torch and some solder. Drilling out the solder is as easy as heating it up later on and rapping it on the table. I used to solder jets closed all the time, then redrill them in my poorer youth where I was too cheap to buy an array of jets. Just a jet drill set and some solder. Find out which one works and then buy the right one for 'proper' finishing of the job.

[madkaw]

Once again, Tony's advice was spot on. Using the red loctite is not the best method. I drove the car after sitting for months and it started the hesistating again. I pulled the bleed pipes and 4 or 5 of the pipes had bleed holes that opened up again. It only took one hole to open up on each bleed pipe to make a difference. At first I thought it might have been from transitioning to the megasquirt ignition, but the characteristics were too similiar. I guess I will solder them at this point.

 

What has worked pretty well is the balance tube for a signal to my MAP sensor. I have read that with a ITB set-up the signal is too jumpy to tune with, but my signal seems very stable. It's really cool to watch it in real time on the laptop! I would really like to change the mounting set-up for the tube though. I want to clean up all the hoses running everywhere and get the balance tube right down on the intake. I have been searching for pneumatic quick disconnects to direct mount the tube to the intake. Being able to quickly disconnect the tube would facilitate quicker tunes. I have a 'clamp' that pinches all the runner hoses for when I am balancing the carbs, but it is a bit cumbersome. 

It would probably be a bitch to try and quick disconnect 6 runners at the same time though-LOL

 

It will be interesting how the tune goes now that I have full control of ignition. I have looked at Lazeums ignition table and know that I can go way more on the advance at cruise. I have thrown in numbers for now and the engine runs pretty damn good so far. I will be curious how much I can lean out things now that I can advance the timing with so much control. My only concern is that the MAP sensor loading scale is narrow. It seems that other then very light cruise, loading shows in a very narrow band of 80-100%, which is going to make tuning a challenge. Since I haven't done this type of tuning, not sure if this is normal or a symptom of my Mikuni's and the balance tube. Will repositioning of the balance tube closer to the intake make any difference in the signal?   

[Xnke]

That narrow loading is a function of ITB's. That's why Alpha-N gets used for fueling with ITB's, because you normally don't get enough vaccum signal to have a clean running car at part throttle.

 

Normally, you'd like to see at most 60kpA of vacuum at idle, with 35kpA being stockish...you say you see 80kpA or so minimum...this points to either a large cam profile with a late intake valve opening, or the classic profile of an ITB car...both of which can sometimes use Alpha-N better than speed-density fueling.

 

You're doing ignition timing, so it doesn't make a LOT of difference for that here, being naturally aspirated.

[madkaw]

Hate to speculate whether the changes are big -especially the butt dyno. I haven't done enough tuning, but I am amazed how well it runs-PERIOD! I spent very little time with the numbers and it accelerates and cruise better then ever. Not a glitch-hope I didn't just jinx myself-LOL

I believe I do see about 60 kpa at idle. OTHER then idle it seems a narrow range and as you said it will be a struggle with the ITB syndrome. BUT, the balance tube is doing it's job especially as far as giving me a stable signal. I need to hook up my datalog wire to a switch so I can start datalogging.

The other thing that's really stable is my rpm signal-so my flywheel sensor is doing it's job!

[madkaw]

Well soldering was almost too easy -once I found a method, which was less solder the better.

I found holding a small iron against the hole for a bit then tinning the tip slightly and smearing it over the hole worked best.

I used a minature fine file and then some fine sandpaper to smooth everything out

[Tony D]

Well soldering was almost too easy -once I found a method, which was less solder the better.

I found holding a small iron against the hole for a bit then tinning the tip slightly and smearing it over the hole worked best.

I used a minature fine file and then some fine sandpaper to smooth everything out

HAHAHAHA! You just brought me back to a sweltering garage in NE Michigan in 1980...

 

As for quick disconnect tubing---look up LEGRIS fittings. There are generic and chinese crap out there now---connecting them with the rigid HDPE or High Temp Plastic Tubing stubs, it's a press and pull proposition to disconnect them. Simply pushing a similar diameter solid plug, or cap in the hole plugs it for tuning. They also make small ball-valves that you can put in the lines...but that might get spendy for something you aren't doing all that often.

 

A carb jet in the MAP line, or even a small engine fuel filter can give some capacitance to dampen the pulsations to a more realistic 'average' MAP signal without degrading the MAP higher up in the rpm range where you want high resolution.

 

Alpha-N is nice on ITB's for Idle. And that's about it, going with the TEC2 PAFZZ Blend program, on the Bonneville Car, it was like night and day. Alpha N at closed throttle and a graduated Alpha-N/MAP based phase in based on rpm or MAP (forget which, may have been both) as the rpms rise and the cam comes on to give a good steady signal.

 

I like that comment "Once again, Tony's advice was spot-on" I will screen shot that and use to to make others apoplectic... The royalty check is in the mail, but I need to get a security deposit from you first...to my bank in Nigeria....