wankel=awesome

At this point Mazda did a pretty good job on the Etubes with the holes lowest in the well it appears. Thats actually a carb "trick" that the factory implented, which i think is awesome.

If you start with the lowest holes in the straw and slowly move down your sizes of high speed air bleeds, that circuit will come on faster and faster until its too rich at your highest RPM's (you likely arent shooting that high anyways, so it wont matter).

You shouldnt even have to mess with your primary etubes, but if you DO it would only be to strengthen the signal from your primaries when the load is full on to help cover the lean spot. (smaller holes at the lowest part of the tube)

You have two choices at this point. But first, questions:

1) How does it respond to a larger secondary jet during the lean bog? Better or worse?

2) How rich is your goal AFR@WOT for this thing?

Depending on those, its pretty simple from here. Shrinking that high speed bleed will bring the fattest part of the signal a bit lower and helping to minimize that lean bog and help it correct itself faster.

Or, enlarging the jet until the lean bog is gone, and then opening up the very lowest emulsion holes to correct your mixture by slowing your jet down when the floats drop under heavy load. Don't overdo this though, it could be dangerous on a boosted engine.

Jeff20B

iTrader: (13)

1)I'll swap in a set of drilled .065" jets (around 1.61mm or more) and let you know.

2)I was told to aim for 11:1 but I've seen it range anywhere from 12 to 10.

I'm thinking I'd like to machine a set of spare sec high speed bleeds to accept some fuel jets. I'll try 130, 120 and 118 (which is actually bigger than factory 120, so around 122 or 123).

Then if this makes my secondary AFR too rich, I assume I could do something to the etubes or throw in smaller fuel jets. I've got 155, 150, 145 and 140.

As for what you said about opening up the very lowest holes in the etube, I'm thinking that might only work if the float level drops low enough for them to be uncovered. But by then the mallory should be pushing lots of fuel in so they might not ever be uncovered except when the mallory is occasionally allowing a lean condition.

Jeff20B

iTrader: (13)

I did some flood testing today.

It turns out some of the flooding was due to the float bowl vent solenoid valve never opening very far. I removed a couple of them today and the results were less flooding when driving them kinda medium, but these two carbs still tend to flood when you really get on it and it takes them a while to recover. That is, they sputter for a while after boosting and read 10.something on the wideband for up to a minute or more. Maybe the needles and seats aren't "burnished" enough yet and they keep getting stuck. I'll revisit boost for these two carbs later.

As for the 3rd carb I tested today, it was virtually flawless in boost! No delays or bogs when you step on it. Just acceleration. And then when I was done, it returned to idle perfectly. No flooding! This carb's only flaw is under vacuum it has kind of a choppy primary circuit. I went ahead and tried two sets of 90 primary air bleeds. One has 6 sets of holes and the other had 7 sets. I thought the choppy primaries might get smoothed out with more or less holes but I couldn't tell the difference. I'm willing to put up with a carb that has slightly less than perfect primaries for this much fun!

wankel=awesome

primaries on or off boost? If idle is working properly, and your actual fuel circuit feels odd, look to your wideband to see if its leaning out of going fat.

My guess, is that you have a lean initial tip in, that almost directly smooths out. You'll have to match you primary low speed to whatever your 45 mph cruising speed is, then see how it tips in. As far as the nikki is concerned, variations in the pump shot are hard to make, so good luck if it is a transitional issue.

But congrats on the success you've had! It makes me want one pretty bad. Now find out what kind of gas mileage its getting, that should be fun.

Jeff20B

iTrader: (13)

Primaries on and off boost. Basically it feels like there is a lag, for lack of a better term, when you get on the primaries with this carb. That is why I tried the 6 and 7 hole etubes. Couldn't really feel a difference. This carb is only powerful when you open the secondaries. At least it doesn't flood anymore.

On one carb yesterday, I'd get on it (holding the pedal at one position) and watch the wideband spike to 12, then the car would lose power and go back to 14. The accel pump shot was used up by then. So you may be right that the primary is slightly too lean on this carb.

Yeah, it could be a lean tip in like you say. The accel pump does seem to have a tiny flat spot when you first press the pedal. A little adjusting of the 7mm nut was next on my list. But I'm testing four carbs in total and sometimes they tend to run together or I forget.

As for one of the other carbs that likes to stay flooded after boost, its primary circuit is perfect and just wants to make the car go during vacuum. I'm wondering how swapping the tops of these carbs will affect the flooding. We know the needles, seats and floats of one carb are perfect (I spent hours getting them just right), while the accel pump tip in and primary circuit of the other carb are perfect. Maybe a hybrid is in order? Or maybe some more careful float adjustment? Or maybe some needle break in time (burnish time) is needed.

Just so much carb testing lately has made them all kinda run together in my mind.

Fuel mileage? If you keep your foot out of it, probably similar to an NA Nikki. Of course these carbs are tuneable to get basically whatever you want.

Jeff20B

iTrader: (13)

I did more flood testing today in between rain storms. I removed the float bowl vent solenoid valve from the last carb that still had one and took it for a spin. The tires wanted to spin a lot but I think I got my answer. The carb will still flood mildly but I found a little massaging of the pedal will relieve its excess fluid. Think of that what you will. Sicko.

This carb's specs:
24.9mm primary venturis
90 air bleeds with 6 progression holes
118 drilled primary jets that seem a little leanish
solder filled secondary slow bleeds

It has a small delay in the accel pump that leads to a minor lean spike when you first step on the pedal. I think a minor adjustment will fix it but due to the way all the parts fit together, the stock 7mm nut needs to be ground down by 1mm so the nylon part grips the threads better, which I'll get around to later.

Also today the idle circuit was way off. Like super lean (16 to 17 with a lean brap) where it wanted to stall and the throttle stop screw needed some cranking in a bit to raise the idle speed. Weird. Maybe the removal of the FBVS valve changed one of the carb's dynamics. Or maybe cooler temps with some humidity played a part. Though the removal of the valves on the other carbs didn't have that result.

wankel=awesome

All of my carbs do this. Some days they start up and idle at a perfect 13.5:1 , and some days it idles at 12.5 lol. My experience with the nikkis is that the carbs temp plays a big role idle mixture. I had one that if you left running for a long period, it would start to "hunt" no matter what the idle mix was. Just because something would go nuts when the carb was physically hot. Then, other days it didnt. Lol they are myterious creatures sometimes.

And it sounds to me like your main jet size on the primaries should go up, and then the accel pump loosened a bit on tip in. although, 14.0:1 is a pretty nice mix for cruising on the primaries.

Jeff20B

iTrader: (13)

Ok I figured out why this carb's idle was so far off. I recently swapped the cast iron base plate (throttle body I guess you'd call it) from another boost prepped Nikki to see if I could solve some issues and discovered a very worn accel pump rod, which I changed out for a good low mile one, but forgot that maybe a little mixture screw adjustment might be needed.

I think the reason why the idle speed changes so much with temp is due to the cast iron TB vs the steel shafts. The stock fabric (or whatever weeved material they are) bushings can't account for the different exansion rates of the two metals. Kinda interesting.

Yes the primary fuel jets probably need to be 125 or maybe 130 as my custom drilled 118 is actually closer to about a 122 or so. However, like you said, that 14 at cruise is nice. Just gotta keep an eye on coolant temps. Apparently 14.4 makes a piston engine (air cooled VW) run the hottest. Not sure that applies to a rotary. Just something I read the other day.

Jeff20B

iTrader: (13)

I tested three carbs in a row.

Test 1) baja's carb with the red truck's top to see if the needles and seats had anything to do with flooding. Result = it still flooded.

Test 2) red truck's carb with its top swapped back on. Result = still didn't flood any more than usualy, which is quite mild and doesn't ruin your day.

Conclusion: Flooding has more to do with the carb main body and/or cast iron base than it does with the top.

The red truck's carb runs fairly well but still has that lagging primary circuit. It also has about 1/2 second delay when the secondaries are opened. It seemed to do it in 1st 2nd and 3rd. It also runs a little choppy in boost. It's gotta be the tune. I was only aiming for an 80% tune on this carb. I'll fine tune the carb later. But at least it doesn't flood and the secondary delay is down to just 1/2 second which I think can be further reduced with tuning.

This brings me to...

Test 3) brown car's carb back in the brown car after a brief test drive yesterday. Result = an improvment from yesterday and an improvement over the other carbs!

This carb runs almost as well as the baja's in vacuum with similar tip-in but handles boost quite well with only 1/2 second delay like the red truck's carb, but doesn't have the choppiness in boost. I think we have a winner finally. I can see about fine tuning the secondaries later.

Oh just to answer your question, it seems to cruise at around 13:1 but it spikes 14 to 12 and back to 13. Not as lean as you'd like, but not that bad over all. Oh and the idle mixture screw and throttle stop screw I had to adjust yesterday were still correct today so I think the adjustment is good. The accel pump nut on this carb also seems to be just about right. After the drive the idle was a little high. To be expected on a warm carb without an altitude compenstator, I suppose.

Not much else to talk about. Oh there was one thing. When I took it to the top of the primary circuit in 2nd gear going up a hill, it starts to sputter a bit as the wideband reads 10.0. Obviously the turbo is spooled up and the mallory is responding as it should. Then you floor it and have to wait 1/2 second. Then the secondaries begin to flow and it makes the car go a little sideways. It even wants to break them loose in 3rd gear now. Gettin' better. Oh and when you let off, no flood. I did smell the leaking shaft gas dripping on hot intake manifold again, but it only lasts a couple seconds. But they all do this without the drilled shaft hole trick which I might look into later. But over all, I'm very pleased with this boost prepped Nikki journy and I'm grateful I had four to test only to discover that some carbs like boost better than others. I must have done something right when I boost prepped this carb and more or less on the other one. If only I could repeat it for the two others.

Hmm, thinking about it more, if I could deal with my incorrect 3/8" and 5/16" fuel lines, it might make the flooding go away. It's worth a revisit to boost on these other carbs later.

Jeff20B

iTrader: (13)

Today I swapped some linkages around to see if the baja's carb could be used in the red truck at some point. This means the unfloodable red truck's carb can go in the baja for turbo testing. This also means the excellent driving and great tip in of the baja's carb can be taken advantage of in the much heavier REPU with potentially a turbo setup, but I have to solve the darn flooding issue at some point.

Another option is to throw the brown car's carb in the red truck with a turbo and call it good while the baja's carb goes in the brown car. Nah, the truck has a reverse runner manifold that isn't very easy to get most carbs to run right on. However the slightly choppy red truck's carb's problems should be masked by the NO manifold in the baja with its smaller higher velocity runners at the expense of some high end power. In the baja, I only need low end so I'm fine. The REPU needs low end and high end with a fat midrange, which the rev runner can provide. The brown car just needs a kick in the pants all around fun factor setup, which the 74 manifold can do with the current carb (the one I affectionately call the brown car's carb which has the nice 24.9mm venturis, which could technically go in the truck with its rev runner, but it would need more testing which I can't do with an S5 turbo without a custom exhaust manifold, plus I gotta wind things down as the colder weather sets in so not gonna do much more testing for now).

Sorry if any of this sounds weird. I've taken to refering to the carbs as which vehicle they were originally built for. It can be confusing when plans change.

erick31876

iTrader: (8)

great thread I'm learning a lot from it,if you need any parts for any of the carbs,let me know,somebody gave me a whole big Rubbermaid tub full of carbs ,manifolds, and parts.I'm looking to return the good will to somebody else

LizardFC

iTrader: (1)

FWIW, I haven't touched any of the air bleeds on my Nikki and I don't have any problem with stumbling or flooding, on or off boost. I've only drilled the main fuel jets and the accel pump jet. Here's my current jetting:

Primary fuel: ~105
Secondary fuel: ~200

Lead timing is locked @ 0 degrees for the time being, with about a 15 degree split. I know, not the best for performance but safe for now while I tune the carb.

AFR data, taken a couple weeks ago when it was still close to 70 degrees outside:
@ Idle after cold start: ~14
@ Idle warmed up: ~11.5
@ 3k RPM cruise: ~12.5
@ 5psi, 4k-6k RPM 75% throttle: ~13.1

That last number worried me a bit so I'll definitely be stepping up the secondary fuel jets to maybe ~220 for the next test.

Jeff20B

iTrader: (13)

LizardFC, I don't think your answer is bigger fuel jets. I think you need to hook up your mallory to a different boost reference source. I use the carb hat and it makes my setup run really rich with plenty of fuel to spare, even with small jets, by your standards. I'm even thinking of going smaller on the secondaries because my in-boost AFR is 10.0 at 7psi. Of course if you do use a different boost reference, it might lead to a flooding problem like I'm having. I found hooking the Mallory to the intake manifold just like everyone recommends, caused my carb to fuel starve.

Let me see if I can mimic your AFR data list and fill it with my info:
@ Idle after cold start: ~14 (wants to stall so I keep it running with my foot)
@ Idle warmed up: 12.1-12.3 but varies between 11.6 and 13.1
@ 3k RPM cruise: 12.3 to 13.5 (so a little leaner than yours)
@ 7psi, 4k-6k RPM 100% throttle: 10.0 but I've seen 11.x - 12.x on occasion this summer with various carb testing.

I don't do 75% throttle. I go from 60% which seems to be the top of primaries/secondary opening point, to 100%.

One thing to note about my experience. When I went to test some custom drilled 208 jets, the secondary bog was over 3 seconds so I aborted the test. Then tried 150 jets which brought the bog back to the familiar 1 to 1.5 seconds, and the AFR was 12.1 - 12.5 in boost (kinda worried). Then went back to 160 and saw anywhere from 10.0 to 11.x so that is where I've kept it for safety.

My timing is a semi-locked dizzy that starts at 0 at idle, then only advances to about 10 degrees as RPMs rise. The split is around 10 degrees. Direct fire with DLIDFIS helps with igniting less than perfect air fuel ratios.

My next project is to test some smaller primary and secondary air bleeds and some smaller secondary jets. My current jets are:
pri air 90
pri jet 118
sec air 140 (stock)
sec jet 160 (stock)

Gonna try:
pri air 80 or 70
pri jet 118 same
sec air 130 or 120
sec jet 155 or 150

This might reduce the bog to 1/10th second or get rid of it completely. It will improve gas mileage too.

Remember I've got a 74 ported R5 13B so I needed to hog out my carbs so they'd be big enough for low RPM/off boost driving, which leads to some of my carb problems. You also should know this but a turbo tune is going to be a lot different from an NA tune which I've discovered on the primary circuit so far. Secondary tuning is next on the list.

Jeff20B

iTrader: (13)

I took it for a short drive to the store today and it's really quite tame and pleasant in vacuum. Didn't flood at all but ran rich for a couple seconds after a little bit of throttle opening, then back to normal. The roads were wet so no boosting.

I feel that a change of fuel lines to Mallory's recommended sizes will get rid of its minor flooding issue during spirited driving.

Jeff20B

iTrader: (13)

I swapped in a set of 80 air bleeds into the red truck's carb today to see how much it would help the weak tip in and other driveability issues. It helped pretty well but a new problem popped up. Now it wants to flood any time after it sees boost. So that's three carbs out of four that want to flood.

It's gotta be the fuel system. I'm changing the fuel lines as soon as I can.

LizardFC

iTrader: (1)

What pump are you running? And what pressures are you seeing?

I have a walbro gsl 392 (255lph) and my regulator couldn't keep the pressure below 9. I added some resistors to drop the voltage and got pressure down to 4-5 psi at idle, which is still too much but at least manageable in cool temps. I used a 3/8" return, which was the biggest aluminum tubing I could get my hands on at the time. 1/2" would have been much better. I may switch to a weaker pump.

BTW, I drilled my secondary jets with a 3/32 bit, equivalent to ~240. AFR was still around 13.1 under boost but it was about 15 degrees colder than the last test.

Jeff20B

iTrader: (13)

MSD 2225. I can see anywhere from 2psi to 3psi with 2.5 being the average, but I find it depends on the fuel pump's mood and whether the moon is full.

I recall you and I discussing ways to get the mallory pressures down but I gave up and swapped the MSD pump in. This brought the lowest psi down from 5.5 with the mallory to 2.5psi average with the MSD. Much improved but my send line is still 3/8", which I went with because the mallory has 3/8" nipples. I left my 8mm GSL-SE return line stock. Now I know I should have left the send line stock 8mm and swapped out the return line for the 3/8".

1/2" return line you say? What if I ran a 1/2" line from the mallory to just past the fuel pump area and then squeeze it down to 8mm so it can go into the stock return fitting in the tank? Think the fuel will "bottleneck" for lack of a better term?

Wow, your AFR is still really lean. Mine is really rich with stock 160 jets. Weird. It could just be the fuel lines.

Jeff20B

iTrader: (13)

Small correction. I meant to say walbro, not mallory.

LizardFC

iTrader: (1)

So you're still running the stock return line, but at the regulator, and deadheading the carb? That would be one difference in our setups. Since I made a new return line for the regulator, I was able to leave the stock return line connected to the carb. I think this helps bleed off excess pressure and keeps things more stable, since the Nikki is supposed to have an internal regulator.

The stock return fitting would probably be a bottleneck. The larger line might help some though. I tapped my new return line into the nipple at the back of the tank that vents to the filler neck. IIRC, that line was larger than 3/8". I capped off the nipple on the filler neck. There's another vent on top of the tank, so I haven't had any issues with vapor locks or pressurizing. I just have to be careful when putting gas in, as the pressure in the neck tends to make the pump shut off and/or overflow a bit if I get careless.

I think my mixture is still lean because of my stock air bleeds. My guess is the small air bleeds don't have a strong enough signal to pull in more fuel. I might try drilling the secondary main air bleeds next.

wankel=awesome

Actually, your air bleeds are only affecting the speed of the circuit and the range of airflow it can see and still be in effect.

SMALLER Idle air bleeds would raise your idle circuit up a bit higher than the stock 750 rpm area (yours is probably higher than that anyways). The smaller you go, the longer that circuit will stay on. You want it to cover the transitional area where your mains are coming on, but not totally engaged yet.

Your secondary main air bleeds have a similar effect. Drilling them out will *delay* your secondaries mains from their highest signal until later and higher air speeds. Just as I explained to Jeff20b, your best bet would be to either keep them stock, or even go smaller than stock if you arent seeing over 7k RPM's...

If you *needed* better fuel signal at much higher RPM's I would tell you to drill them out a bit, delaying the main jet a bit and moving the fat part of its fuel supply to lower vac/faster air (later RPM's)

If you want more fuel at idle, you need to open the restriction to the fuel side of your idle circuit, not the air side.

Jeff20B

iTrader: (13)

Lizard, yes, stock 8mm return line from the reg back to the tank. Yes the carb is dead headed.

Hmm, I don't want to mess with the vent at the fuel filler neck. Sounds risky. My tank used to pressurize until I just removed the vent line from the charcoal canister. I went through three of those things where each one would basically fill up with gas fumes and then clog up causing excess pressure to push past the fuel pump and make the carb flood out, even at idle, and would continue to run the engine even after the fuel pump was manually turned off. As you can guess, I was chasing that one for a while. (This, being my first factory EFI gas tank and all - the carb tanks never did this.)

The simple temp fix was to remove the vent line from the canister and suddenly everything worked right! I recall PercentSevenC removed his entire vent line from under the car and never had my kind of flooding issues. I'm still working out where to route the vent line but I'm thinking of some kind of purge valve and a nipple on the filter elbow where it goes into the turbo air inlet. Hmm, I realize I don't have any pics of my engine bay. It might help you guys see what I'm talking about. I'll see about shooting some later today if I remember.

I agree with wankel=awesome about your air bleeds. Make them smaller and see about increasing your fuel jets (or not). Also see about dead heading your carb. I think the Mallory was designed for a dead headed carb like a Holley, weber and other typical carbs most people boost prep. I'm willing to bet the reason my Nikki gets so much fuel with small jets is because it's dead headed too. I'm sure if you dead headed yours with your large fuel lines, you'd get more fuel too. Oh and if you still have a resistor on the power wire, well, you know.

Jeff20B

iTrader: (13)

wankel=awesome, I tried a set of 80 primary air bleeds in a carb that had lousy tip in. It helped this carb. First I tried 90 air bleeds with 6 and 7 progression holes. Little change. Then I tried the 80s with I think 6 prog holes. I'll have to check my notes.

The result: Better tip in, easier starts, and the interesting thing: this carb now can run all the way up to 6500 on primaries without getting sputtery where as all the other carbs with 90s tend to get weird up there. So I think we have a winner with the 80s! Too bad I only have one factory set of these. Oh well, gives me something to shoot for with some machined stock air bleeds and some Holley replaceable air bleeds.

Jeff20B

iTrader: (13)

Today I drilled and tapped one of these for a second 5/16" nipple opposite the threaded end.

I couldn't find what I was looking for locally so I had to get one of these and drill/tap it. It will install on the mallory for fuel from the pump going into the carb, like a Tee fitting. This should help my flooding problems.

Jeff20B

iTrader: (13)

Speaking of Holley replaceable air bleeds, a set of 51s (.051") were ordered which is about 130 metric.

These are good for secondary air bleeds on boosted carbs with tuneable air bleeds and primary fuel jets on NA carbs with hogged primary venturis like mine. They come in a 10 pack (that's 5 pairs) from Amazon.

wankel=awesome

thats where I get mine too