Just started playing with Innovate LM-2 on Mikuni 44 2.9L stroker

[Tony D]

"Blowing Black Smoke" on an un catalysed L-Engine is very low 10's and into the mid 9's AFR!

 

That is a DEFINITE "way too much fuel" condition!

 

Short blasts really don't give you accurate indications of fuel delivery. Really if you had a long gradual uphill grade so you don't accelerate so fast, it makes getting things stabilised in the system easier.

 

You would be amazed by what looks good for short blasts, but as mile marker three at WOT passes at B'ville you start seeing some strange things happen!

 

That's where that dyno comes n, you can only get "so" close on the street. Holding the max horsepower load point for 5 minutes straight is a bit impractical in most metro areas, and frowned upon universally by all law enforcement!

[inline6]

Rated according to actual flow, not wire diameter hole drilling like Rochesters!

 

It's why "jet drills" so commonly used on Holley & Rochester stuff, with somewhat repeatable results can be maddening with Webers & the like. I think there is an admonition in the manual against "drilling he jets" due to the "ream-test-stamp based on flow" procedure.

 

Should I just trust the numbers then - assume the flow was done correctly?  I'm having some difficulty with the fact that the flow on the various jets I have differs a lot with the same size hole in them - there isn't much to them except a hole!  I've got some 170's and 185's that measure the same size opening.  Now that you mention this, I do recall stumbling across an article once about someone measuring flow rates of jets to get everything matched up.  I'll switch to my EFI before I get that deep in into it.  I have just wanted to have a triple Mikuni engine since my teens...  so I am doing it, but will put the EFI on after I have my fun.  

 

So, for me, playing with these carbs is sort of like the moment when you finally get to drive that Exotic car you had posters of in your room.  When you actually drive it, you realize that you really shouldn't have because the actual experience can't live up to the dream.  

[Tony D]

Been there, done that, bought the ITB's...

 

"Never assume used jets have not been altered."

 

My nephew routinely drills his jets on American Iron, and laughs at the guys who think he's ACTUALLY running an "XXX" jet wherever!

Edited February 20, 2013 by Tony D

[inline6]

Took it for two test drives tonight.  I also put some miles on it over the weekend, so hopefully it is breaking in nicely.  So, the change for the first run was to put in main fuel jets one size smaller - 160's and then see what that did.  I went out on the interstate and played with some acceleration runs in 5th, 4th and 3rd, with revs from 3k to around a little south of 6k.  The goal was to spend at least a few seconds with throttle open 50% to 80% while looking at AFR.  On this outing, during those moments after transitions, when the car was pulling well, I was seeing 16's and 17's. 

 

Another thing I tried was quick and substantial throttle openings.  The quicker they were and the deeper they were, the lower the AFR dove.  With really quick and really deep throttle applications, even in 3rd at something north of 4k RPM, it would go down into the 10's.  With 4th or 5th, it would go down into the 9's.  It was dark out, so I couldn't see any smoke.  Anyway, as a result of those tests, I decided I would try smaller accel pump jets.  

 

So after that test, I changed back to the 165's (main fuel) I had in there before, and I lowered the accel pumps to 40's.  

 

For test number two, I went out to the same interstate and repeated the tests.  Again, depending on how quick and deep I got into the throttle, I was still seeing 10's and even an occasional 9 something just after initial throttle opening, but as RPM's went up, the AFR climbed, only this time it didn't go as high as before.  I was seeing low 15's and the engine seemed to be pulling noticeably harder.  Perhaps going with 165's was the right move.

 

And here is something really interesting.  On the way back home, I was playing with very slight dips into the throttle and noticed a hesitation that seemed like it was consistently in the transition from pilots to accel pumps - throttle opening had to be "enough" but not more than "a little" - in other words, it felt like it was right around 20% throttle opening.  I did it repeatedly and every time the AFR would show a very brief lean spike.  I'd be cruising at 70 mph or so, dip just that right amount into the throttle, and then see the AFR spike up with one brief instant to 17 something before blinking back to something more normal like 15.  And again, with heavy and quick throttle openings, I could send the AFR down into the 9's and choke the engine up.  

 

Having read quite a bit of what others have posted in various carb tuning threads, I think what is going on is I am too lean on the pilot jets so the transition off of the pilot circuit is causing a brief lean condition.  Again, I am running 55's and I am 1 and 3/4 turns out on the pilot screws.  The consensus from the experienced seems to be to go with the richest pilot jet you can get away with and keep the turns on the pilot screw to no more than 1.  With either 57.5's or 60's, I hope to get down to 1 turn out... and still get the same overall driveability experience from idle to 20% throttle as I am getting now, but to eliminate or minimize that brief lean spot in the transition away from the pilot circuit.  

 

And I think the 40 accel pump jets that I put in are still too dang big.  I don't have enough 35's - only have four, so I will have to buy some.  With the 165's main fuel jets, I am seeing what looks to be a fairly stable AFR in the 15's.  This seems to indicate the need for bigger main fuel jets, so I will give that a try next.

 

I'm really not sure how the air correction is going to play into this.  My basic understanding is that I need to play with that to adjust AFR in the 6k-7.7k rpm "high engine range" (whatever that is) territory.  Best to put some more miles on the engine before testing up there.

 

Also,  I need to find a way to check for constant fuel pressure from the pump as Tony said...

Edited February 22, 2013 by inline6

[Tony D]

Bigger pilots, less screw opening. Yep!

[madkaw]

'noticed a hesitation that seemed like it was consistently in the transition from pilots to accel pumps'---If you have had the carbs off the car and activated the throttle you would see that there is no transition between pilot and accelerator pump. The slightest throttle input pumps fuel out-the pumps are very sensitive.

 

What setting is the pumps on?-What hole?

 

 

Don't be afraid to turn out those pilots some more. You still have adjustment that will be noticable. I've ran them 2.5 turns out before I ran out of adjustment. Crack them a .25 turn and drive around again. Get your idle AFR close to 12

 

 

Where is the power band for that cam? You might need to be around 4k+ hard tip ins to judge jetting. Which may also tie into what you are saying about main air jet selection. 

 

Todd at Wolfcreek  might be a productive phone call once you have the motor broke in and have tried everything you know. 

[Tony D]

Remember that by opening the pilot screws out further than recommended, instead of getting the larger pilot jet, you SET UP the lean transition!

 

The transition ports use the pilot jet as fuel source. The recommendation on pilot jet turns out is a calculated annular discharge area that is not exceeded, allowing all additional fuel flowing in through the pilot jet to be available to the transition ports.

 

It is predicated that if you need a lot of fuel at high vacuum idle, it should be available through a set area and adjustable through a very narrow range of adjustment.

 

Corollary to that is if you need big fuel at high vacuum, you need it in transition. Open those screws up, beyond recommendations, you rob transition fuel available.

 

The limit on turns FORCES people to change the jets (for proper operation)

 

You look at a 1973 GSS Corolla with an 18R-GR making 140HP out of two litres, the Mikuni PHH's from he OEM were set up EXACTLY as stated: pilots barely open, huge pilot jets....but it drove like a Corolla with a single carb, silky smooth no bogs no coughs.

 

Instead of reinventing the wheel, listen to those guys that designed them! They aren't Rochester YH's, turning the screw out further will not make your job any easier... In fact, thes niggling things show up and confound people repeatedly.

Edited February 21, 2013 by Tony D

[madkaw]

In the interest of research, PM me and I will send you pilot jets. I have a slew of them and be willing to let you borrow some to get dialed in. I'm up to 70's now, so I have all the smaller one available. I have 40's(mikunis), but I believe jets are the same.

 

Tony knows way more than I, and I have used his advice. My car runs good, but still do suffer a slight studder or hesitation during moderate tip-ins below 3500. I show leaness on the gauge, but I haven't tuned long enough or know enough to attribute it to pilots or pumps. I have very little to complain about, my Mikuni's run better than I ever expected and the car is a great DD.     

[Leon]

FWIW, my Webers idle at 14.5:1, cruise at 13:1 (I will lean this out further) and go to 11-12:1 at WOT (this needs some trimming). I can stomp on it in 1st gear, at 1200rpm and take off without a hitch. I've reached this point by using proper e-tubes (Keith Franck's design), fine-tuning the idle jets (KF's hypojets), and finishing up with the accel circuit. Accel enrichment tuning should be done last, just as if you're tuning EFI.

 

There's a scientific approach to tuning these carbs, jumping from circuit-to-circuit will have you chasing your tail. Take a look at Keith's "White Paper" in the Files section of Sidedraft Central. You'll have to register there first. Although the site is Weber-focused, the approach is the same for any DCOE-like carburetor.

[inline6]

What setting is the pumps on?-What hole?

 

Where is the power band for that cam? You might need to be around 4k+ hard tip ins to judge jetting. Which may also tie into what you are saying about main air jet selection. 

 

 

Middle hole.  Not positive on the cam power band, but probably something like 3000-7700.  Redline from the manufacturer is 7700.  

 

Remember that by opening the pilot screws out further than recommended, instead of getting the larger pilot jet, you SET UP the lean transition!

 

The transition ports use the pilot jet as fuel source. The recommendation on pilot jet turns out is a calculated annular discharge area that is not exceeded, allowing all additional fuel flowing in through the pilot jet to be available to the transition ports.

 

It is predicated that if you need a lot of fuel at high vacuum idle, it should be available through a set area and adjustable through a very narrow range of adjustment.

 

Corollary to that is if you need big fuel at high vacuum, you need it in transition. Open those screws up, beyond recommendations, you rob transition fuel available.

 

The limit on turns FORCES people to change the jets (for proper operation)

 

You look at a 1973 GSS Corolla with an 18R-GR making 140HP out of two litres, the Mikuni PHH's from he OEM were set up EXACTLY as stated: pilots barely open, huge pilot jets....but it drove like a Corolla with a single carb, silky smooth no bogs no coughs.

 

Instead of reinventing the wheel, listen to those guys that designed them! They aren't Rochester YH's, turning the screw out further will not make your job any easier... In fact, thes niggling things show up and confound people repeatedly.

 

Hear ya.  I switched to the biggest pilots I had tonight - 60's.  Was able to achieve high 14's, low 15's AFR with 1.25 turns out, but as soon as I cracked the throttle at all, the AFR dropped into the 12's.  It sounded fat, and throttle response was noticeably subdued.  Switched from those to 57.5's and was able to get the AFR around high 14's low 15's at close to 1.5 turns out.  Slight opening of throttle gave me 13's instead of 12's - the engine was clearly happier - throttle response was happier.  I didn't get a chance to road test because it started raining.  I will do that next to see if the lean spot is subdued to any degree.

 

In the interest of research, PM me and I will send you pilot jets. I have a slew of them and be willing to let you borrow some to get dialed in. I'm up to 70's now, so I have all the smaller one available. I have 40's(mikunis), but I believe jets are the same.

 

 

Thank you! for that offer.  I think I have all the pilot jets I need.  You wouldn't have any 35 or 30 pump jets would you?

 

 

There's a scientific approach to tuning these carbs, jumping from circuit-to-circuit will have you chasing your tail. Take a look at Keith's "White Paper" in the Files section of Sidedraft Central. You'll have to register there first. Although the site is Weber-focused, the approach is the same for any DCOE-like carburetor.

 

Thanks for the info.  I'm all over it - learning so I can make improvements.  

[Tony D]

Pilots will interchange between 40/44PHH, change away!

[inline6]

Did some more testing yesterday and today.  With the 57.5 pilots, I am no longer seeing (lean AFR on the meter) or feeling that brief lean spot during light throttle tip in - which felt to me to coincide with the transition off of the pilot circuit and onto the pump circuit.  

 

I also tried hooking up the analog cable today - for RPM input only.  Not sure what is going on.  I tapped into the negative lead on the coil (Crane PS 9 I think).  When I checked it briefly at idle before actually splicing (and after running through the configuration), it seems to read the RPM's.  I saw it read 900 or so at idle briefly, so I turned the car off and ran a wire from the neg on the coil into the passenger compartment (the cable that comes with the LM2 is not long enough) and spliced it to the black with white stripe wire on the LM2 analog cable.  Now, it will intermittently read like this 50......0.......200........80.......  at idle.  Each number shows for a few seconds. Anyone have any ideas what the problem is?  

 

Since the engine has enough run time on it now, I decided to get into the revs a bit more and to record some data for the first time.  It would have been nice if the RPM hookup had worked, but oh well.  

 

I also put 180 mains in before going for another road test.  I did this specifically because during previous testing with the 165s in there, I was seeing 15s after opening the throttle about 60-75% but also holding it in a fixed position for many seconds... the car was accelerating briskly but with no movement of the throttle.  I am confident I was completely out of the pilot circuit and I did spend a significant amount of time accelerating after all pump jet effect should have been out of the picture.  With the 180s, reproducing this same situation as best I could, I believe I am seeing low 12s to 13s instead of 15s.

 

The AFR's are ok in most situations.  The one thing I know I can't do is give 3/4 to full throttle in high gears at low RPM's... that can cause the AFR into the 9's and the motor will start sputtering.  I don't want to wash the cylinder walls with lots of fuel!  Other than that scenario, AFR in quite varied situations is almost always between 12 and 16.  I was pleased to see that I could rev into 7k territory with no problematic AFRs.  

 

I recorded one run from standstill through 3 gears (still not full throttle).  Just finished looking at it on my laptop.  Generally, I am seeing that as the throttle opens, the AFR drops quickly to around 12 or even into the 11s, then it climbs out of that into low to mid 12's and then low 13's .  Hard to know for sure what the plot on the graph relates to during the run without the RPM's showing.   

 

Definitely some pretty cool stuff.  Going to have more fun with this once I get the RPM signal working right. 

Edited February 25, 2013 by inline6

[Tony D]

In fifth gear, on level ground, with the engine at operating temperature you should be able to go slammed to the floor WOT from 1,000 rpms and the car should not lurch or slow, but give the triples growl and slooooooooooooowly start building speed smoothly and increase as rpms come across around 3,500 to what you normally consider "top gear acceleration".

 

Have absolutely NO clue what AFR's you will see during this test once successful, but when jetted right...this IS possible.

 

Every OEM Mikuni car could do this as well... Millions of Toyotas did!

 

A catalog during that test would be quite revealing!

[inline6]

In fifth gear, on level ground, with the engine at operating temperature you should be able to go slammed to the floor WOT from 1,000 rpms and the car should not lurch or slow, but give the triples growl and slooooooooooooowly start building speed smoothly and increase as rpms come across around 3,500 to what you normally consider "top gear acceleration".   

 

  Looking forward to that day... 

 

in the meantime, the learning continues.

[inline6]

Until the learning stops... completely.     Tonight, I again hooked up the black wire with white stripe from the analog cable to the negative on the coil (it is actually a Crane LX91)...  I was watching the RPM's on the display of the LM-2 to see if there was any pattern to what it was displaying.  I'd get all kinds of numbers but generally it would bounce from some random number like 240 to 540 and then to 0... then to 360... and 0.  I was playing with the wire to move it around and see if that made a difference (which it didn't) but the longer it ran, the better it got.  After a few minutes it was actually registering some rapid changes for short bursts of time like 850, 870, 840, 880, and when I revved it a touch it read 1100's, but then it would still revert back to 0 or 300 or 540 for brief periods of time.

 

I got distracted for a minute or so doing something, and when I looked back at the meter, it wasn't displaying AFR any more.  It said "E9".  I turned the car off (because running it with the O2 sensor not working is bad) and pulled the cigarette adapter power cord out and plugged it back in again.  Fired it up and AFR was again displaying but long story made very short, now the AFR is completely wacked... reading completely different readings than before and jumping absolutely all over the place.  I think the 02 sensor is shot - thanks to me running it without power for too long.     

 

I took it for a drive to see if it would "clean up", but no luck.  And the RPMs won't even begin to work at anything over 1100 RPM.  As soon as I give it any throttle, they drop to 0 and stay there most of the time... or go to 10... or 30... but that is it.  

 

So... I'm pretty stuck at the moment with a non-functioning LM-2.  

[Tony D]

Ahh the days of perception of misfire, countless Top Gear WOT Pulls, reading individual EGT's, and maybe a Colortune angled so your passenger can call it out as you drive with the hood off at dusk!

 

Or better yet, sitting in a car with a removed back window, a notepad, and the boot lid removed watching SU Stations while listening with a mechanic's stethoscope for detonation...

Edited February 27, 2013 by Tony D

[inline6]

Read some forums and found where people having same symptoms with AFR readings on their LM-2 fixed it by re-calibrating the o2 sensor.   So, I pulled the sensor out of the exhaust pipe and took the unit outside the garage to another one of my cars (for power) and re-calibrated it.  Then I re-installed it but it was too late at night to fire it up to see if the AFR readings had returned to normal.  

 

As I was trying to go to sleep, I recalled that I had seen "CAL" show up very briefly on the LM-2 screen.  Thinking through the event... I believe I somehow triggered the calibration mode without going through the menus... and the thing calibrated while the engine was running.  Again, E9 is "supply voltage too low", so when I first saw it, I reached in and pulled the power adapter from the cig lighter and put it back... and I did this a couple of times in rapid succession hoping to get a better good connection (I have since then gone through the cig lighter and cleaning everything for good electrical connection).

 

I also read through the Crane Hi-6 manual and the LM-2 manual in search of answers for why the RPM's weren't being read correctly.  I'm using a MSD tach adapter with my Hi-6, which I had to put into the loop to get the stock tach to work.  Not sure, but I am guessing that wiring the tach adapter into the mix could be causing the signal the LM-2 is looking for to be unusable (the negative from the coil).  

 

So tonight, I took the LM-2's black and white wire which was hooked to the negative wire coming from the coil and changed it to the tach output wire on the Hi-6 (green wire). Seems logical that with so many people having good results with hooking that wire to the MSD 6AL tach outputs (more forums) that the LM-2 should be able to use the Hi-6 tach output signal.

 

Then I fired it up.  First, the AFR readings are back to normal.  So, the O2 sensor isn't fried yet.     

 

The change I am seeing as a result of moving the RPM wire location is basically twofold.  First, RPM's almost never read 0 now.  Second, I get a few, somewhat accurate readings around idle speed, but when I get into the throttle at all, the RPM reading on the LM-2 screen jumps to various readings in the 1k to 5k range.  They are pretty random.  The LM-2 manual has a brief section on "Attenuating a Tach Signal" which involves putting a potentiometer into the circuit.  I figure that is worth a try next.  

 

Progress can be painfully slow sometimes.

Edited April 6, 2015 by inline6

[inline6]

Got the potentiometer from radio shack.  They didn't have a 20k or 50k one, so I got 100k instead.  Wired it up as instructed in the LM-2 manual, turned it all the way clockwise, and started the car.  The LM-2 was reading 0 RPM's (as the manual indicated it would).  I then slowly turned the potentiometer counter clockwise and "voila", RPM's are showing on the screen now - nice and constant... and changing with engine speed.  

 

I was going to go record a couple runs, but the transmission has been leaking and it seems to be getting worse.  I'm not 100% positive, but I think it is leaking from the O-ring on the "striking rod".  That is the main shifting shaft.  There is also an oil seal in there.  I rebuilt the transmission a couple of years ago, and definitely didn't replace those.  So, I think I'll try to order those up and see if that fixes my leak. 

[2eighTZ4me]

I have quite the assortment of jets if you need to borrow some locally - we are on opposite sides of the ATL - but it beats paying for shipping - AND you get a chance to drive your car! My 44's came with a divided compartment box with probably 3-4 different sizes of each type of jet.

[inline6]

I have quite the assortment of jets if you need to borrow some locally - we are on opposite sides of the ATL - but it beats paying for shipping - AND you get a chance to drive your car! My 44's came with a divided compartment box with probably 3-4 different sizes of each type of jet.

Cool.  Thanks for offering...  I just started doing some more testing and when I feel like I know what direction I need to go, I'll be in touch.  

 

Basically, what I have been doing is taking the car up on the highway and doing 2 pulls in 5th, 2 in 4th, and 2 in 3rd.  With each, I start our 65 or so MPH.  I had the car running pretty well with one combination, but the thing that is bugging me is the 5th gear pulls.  Consistantly, shortly after giving full throttle, the AFR drops down... down and then, when it gets below 10, the motor starts acting up, so I immediately let off.  So... to rich on the mains right?  

 

To see if I could alter this behavior in 5th specifically, I went with the leanest sets of jets I have on hand.  150 Mains and 190 Airs... along with the 57.5 Pilots and 40 Pumps.   And here is what happened:

 

 

Sooooo... how could that be?  Mains too big?  I think not - as here is a run through a couple of gears with moments of full throttle, but it was leaning out big time with this combo.  This graph shows that pretty clearly.

 

 

I have a run in 4th also, but I just stopped making runs with this combo because it is clearly too lean.  I guess it is possible the air is too big, and the main could be sized correctly, but based on my results from this following combo, I don't think that is the problem:

 

180 Mains, 220 Air, 57.5 Pilots, 40 Pumps... these are the two 3rd gear runs:

 

 

 

 

And, yes, I totally have a hesitation for a split second when I snap the throttle open.  I'll try larger pumps... which should shorten the duration of the fuel stream event.  The way I read these graphs, it seems that right at full open, the AFR jumps lean, but then is followed by a brief rich spot before it seems to come into a steady line.  This can more readily be seen in this 4th gear run:

 

 

 

Perhaps larger pumps will put more full into the first half and less into the second... and smooth it out.  We'll see.

Edited March 22, 2013 by inline6