EDIT: BRUNHILDE IS FAT. Help me put her on a fuel diet.

[2002Scoob]

That's what it took to get my idle and progression circuit in place on Brunhilde. Long post, but I haven't made a topic post in a loooong time anyway. 

 

I drove the new motor I built for a good while with 32mm chokes with the intent not to make a lot of power and keep the RPM's lower to break it in. And while I don't remember the jetting setup I ended up with off-hand, It drove great and I had it pretty dialed, but ran outa' oomf pretty quick. 

 

I then swapped over to 34mm chokes at some point later last year to try and kick it up a notch, and while it goes like stink, it also kinda stank a bit cuz I never got it quite right. (and still haven't) It was either pig-fat or stick-lean, and having not been able to find it's goldilocks zone, I've erred on the rich end of the spectrum cuz rich is safe, and lean means damage. And I'm not talkin' crazy rich, but around town it was in the 11's, maybe low 12's depending on my idle, most of the time when relying on the progressions around town. More than it should.

 

I've been pulling the car out once every few weekends intent on getting the motor running it's absolute best I can get it. Frankly, so I can enjoy the full fruits of my efforts to the fullest before I sell it. (The motor, not the car. Unless someone wants to throw a handful of cash at me for the whole shebang thats enough to do what I really want project-wise) But I really haven't been driving it... Only here and there to fiddle with my latest bag-of-brass-bits, or to just go for some spirited sprints to keep the juices flowing. 

 

Now, I've been well aware for a while I was compensating for an inadequate pump jet with a stout idle/progression circuit to not stumble when matting the loud-pedal at lower RPM's. But trying the typically recommended go-to jetting didn't really seem to apply in one way or another. A while ago I dropped from a 70 spill to a 40, and that cured my lean-ales for what was in there.

 

For Idles, 55f9 was really piggy-piggy-like 10's in the progressions, 50F9 and F6 were sketchy lean, and for all my efforts couldn't tune them in and feel good about it. 55F8 leaned it out a tad more, and worked well with the 40 pump jets/40 bleeds of my lacking accelerator circuit to where I could goose it in most any situation without getting any of that lean-stumble, and she would just pull.  

 

On another front, I was getting frustrated with not being able to really lock-in my idle AFR's due to some sloppy-fitting mixture screws and gritty/rusty springs that would bind. You had to be pretty precise and make sure there was no tension on the springs after adjusting, otherwise they'd 'settle' after being subjected to extended freeway buzzing. But even then, after several hours of driving anyway they'd tend to migrate the tinyiest amount to take a dead-nuts 13.5, to something that's jumping between 11.5 and 14.5. So I threw more money at Eurocarb and got all-new short-taper mixture screws (They're the oldschool italian variety carbs) ,springs, washers, and O-rings.

 

I then had a very happy, very steady idle. So I decided to apply the squirrel cage gage.

 

I noticed that I still must have a very slight twist to the thottle shaft on my forward carb, as the forward throat was reading a bit high. It's been that way since I got 'em, but I did some gentle persuading to get them allot closer the last they were off the car but obviously not enough. It showed up on the squirrel gauge with the forward throat reading around a 6 when the rest were close to 5's. 

 

Drove around, runs well, still rich, but not perfect. So i thought, heck why not... I haven't practiced carb syncing in a while, and it's been a topic of late anyway.

 

So, I popped off the linkage of the forward carb, got some wrenches on the shaft, rolled the throttle forward, and started twisting. It's not perfect-perfect, but I now got it darn good enough to be just a smidge off of it's carb-buddy. 

 

And after 5 min of getting nerdy with the squirrel cage and tiny wrenches I had the carbs pulling pretty tight numbers as I rolled thru the progression circuits by gradually turning in the idle screw. Pretty happy bout' that. Forward throat it still a tad higher than his 3 neighbours, but not by much. I'm still having the mental debate of if, in such a situation, you'd want to-

 

A. Sync to the Highest#. So, if the back carb pulls 5's, do you set the forward runner to 5, and let the 2nd be like a 4.5?

 

So- 5---4.5---5---5

 

B. Do you do the opposite, and do

 

- 5.5---5---5---5

 

C. Or Split the difference?

 

- 5.5---5---5.25---5.25.

 

(Obviously the answer is muck up everything I just did, and keep twisting those butterflies back to plumb, but common. That would take less time than writing this post, and who wants that?)

 

Went for a drive and she's runnin a treat. But still fat. I threw back in the 50f6's I had in there before that didn't work for shit before, and sure enough, they still didn't. So I tried the last set of Idles I hadn't tried.

 

55f2. Anybody else runnin' that?

 

Yah, I'm back to being lean if I get on it too quickly... The largest pump jet I have is a 50, with a 40 valve... BUT the bumble-round-town-ability is pretty great. Idling at 13.5, mild accelerations stay around 13.5-high 14's. steady-state cruising on the progressions around town is no longer 11's with the F8's, it's high 14/mid 15's... I'm stoked. 

 

Now... I just need to decide how to adjust my accel pump circuit to compensate. It's not even in the ball-park to be able to punch the throttle without falling on it's face, but I was able to slow roll past the progressions into the mains just fine.

 

I've got 50 accell w/40 spills in there now,.

 

Whatcha'll think? Am I on the right track?

 

Should I go to 55 or right up to 60 pump-jets? And what do ya'll think I should do to counter with the spill valves? I've got a set of 70's as well in the brass-bits-kit, a single 50, and a single 0... (somebody screwed up my order) so I could get matching pairs for those as well handily.

 

Just thought I'd share, since it seems several people are trying to dial in their winter cars/projects too. And if anyone in Europe wants a low KM motor (Jet kit included!!!) just lemme know

Edited May 28, 2020 by 2002Scoob

[rcf925]

I have a .292 cam, 9:8 CR, Racetek pistons balanced blueprinted motor with dual italian 45's. I started with 50 idle and had stumble off idle, Tried 55,60,65 idle, It likes 60 best no stumble with F9, 34 venturis, 135 mains. I don't have a way to check AFR but car is running great, I know is somewhat rich at idle but I'm ok with that. I also just re-synced my carbs which got rid of a underload 4th and 5th gear stumble

[2002Scoob]

Yah, I remember a few of your posts about 60 idles, but I think that if it works for your 45's, it doesn't for my 40's/motor.

 

I think if I were to throw in 60 idles and a spark-plug in the muffler I could shoot flames, haha.

 

Also, you say 55, 60, etc. But I'm finding there's a pretty big variation in idle jets when you factor in air-correction to those numbers. a 55f9 vs. a 55f2 is the difference between 10.5:1 and 13.5-8 on the progressions with my setup. 

 

Now... A 60 pump jet? Or a 50/55 with a 0 spill Possibly? I dunno... That's why I ask

 

Edit- I see you said 'with f9' so I'm assuming you're running 60F9. I do have a set and tried them a while ago, and the bottom fell outa' my wideband. SUPER duper rich. 

 

Edited May 21, 2020 by 2002Scoob

[rcf925]

I'm finding it's all pretty much trial and error, What works for one doesn't necessarily work another

[2002Scoob]

Here's my running tuning theory- Have WOT, idle, and Light throttle progression tuning as dialed as possible. Leaving the accel. circuit to make up the gaps inbetween, throttle application dependant. Right now I can lightly roll into the throttle and get to the mains while sicking to the 13's and 14's without edging higher than the 15's, till I'm in the main circuit and can get into WOT.  And I with the 55f8's and my main-stack I've had no issues being 12.5-12.8ish at WOT on the freeway, and cruised all day at 160kph in a safe AFR/temp zone. 

 

I can't remember what my main stack is off the top of my head... 130 or 135 main/170 or 175 airs? I can't remember.  I'd have to go down to the car to check so don't hold me to it. 

 

So if Idle is solid at low-mid 13's, Progressions are in a good place AFR wise, Mains/WOT is good, but I stumble with moderate-heavy throttle between the two, and when prodding it more aggressively outa' progressions below say, 1300rpm, I need to look at how to enrich, and possibly modulate the duration of the pump/accel circuit. Yah-no?

 

 

 

 

Edited May 21, 2020 by 2002Scoob

[2002Scoob]

I'm going to add to the above....

 

Current Main Jet stack is 130/175, which worked well with the 55f8 40/40 combo. 

 

I guess another approach, and maybe this makes more sense, is to actually fatten up the main jet, perhaps to a 135 so perhaps there's less gap between the progressions.... and increase the air corrector to compensate.... Maybe that's a way to go too....

 

Just Thinking (typing) out loud (silently) to myself

-J

[Son of Marty]

You could try moving your throttle return spring to the front of the front carb to help bring it into sinc at idle, I think if you tune your carbs to go from idle to wot in one burst your overall drivability will suffer, your flashing more than 6 1/4" of throttle plate to a 2 liter motor. IMHO you'll be faster to roll the throttle to the point your on the mains then punch it, from idle to 3k rpm's only takes a second or less then your good to go. Again just my opinion and I'm the last guy to tell anyone how to tune their car. 

[rcf925]

Currently my main jet stack is 135/160

[2002Scoob]

20 minutes ago, Son of Marty said:

I think if you tune your carbs to go from idle to wot in one burst your overall drivability will suffer, your flashing more than 6 1/4" of throttle plate to a 2 liter motor. IMHO you'll be faster to roll the throttle to the point your on the mains then punch it, from idle to 3k rpm's only takes a second or less then your good to go. Again just my opinion and I'm the last guy to tell anyone how to tune their car. 

 

Agreed on several points. And honestly, I'm puttin' myself out there for people's opinions or suggestions! So offer away, discussions are welcome. 

 

Yah for sure rolling into the throttle, i'm never flat mashing it from idle. And if I do need to move in a hurry, I'm blipping up to a good RPM and slipping the clutch. I'm still on an e21 4spd that still works and in no hurry to break things, I treat my girl well . But do I wanna be able to roll as quickly in as possible without the fear of lean stumble,  step out the back end on-command, and be confident in being able to punch it if I need to when entering traffic from a stop or slow roll without hesitation.

 

Ideally, the tires loose grip before the motor looses power

Edited May 21, 2020 by 2002Scoob

[Son of Marty]

Yeah keep it up, playing with Weber's is fun.

 

 

Ideally the tires loose grip just at the point the engine looses power?

[Stevenola]

Where are your throttle plates in relation to 1st progression holes?

[TobyB]

and here, I thought...

 

t

 

[2002Scoob]

1 hour ago, TobyB said:

and here, I thought...

 

t

 

Ha, missin' a 5 for the 555! Back when race car drivers were the manliest of men. 

 

At first I thought you meant I needed skinnier tires, or to get an open-top, open wheeled race car  While I'd disagree with the former, I whole-heartedly support the latter!

 

6 hours ago, Stevenola said:

Where are your throttle plates in relation to 1st progression holes?

 

I didn't pay too much attention, but can run down later today and put a light down the bores to give real data on where it's at now. 

 

But if the first progression hole was the moon, and the leading edge of the throttle plate defined as shadow- When eyeballing the forward carb plates thru the progression holes before I pulled off the linkage to torque the throttle shafts, #1 was closer but not quite 'waxing crescent' on the first hole, while #2-4 were a little nearer to first quarter, so nearly shut. 

 

 

When it's warm, it'll idle with the adjustment screw completely backed out and the throttles fully closed, just not fast enough to be smooth. I'd guess it's in the 6-700's. The weekend is almost here, and I'll do some more tinkering then. I'm trying to form a game-plan that I can fuss around with with the brass bits I got.

 

Main and air correctors I've got in-mass, and I know I've got 135's, but sadly nothing larger than a 50 pump jet. That's another parts order. 

[TobyB]

(those are formula 2 cars from 1955, mostly)

 

Does sound like your throttle plates aren't fully closing, tho.  The unevenness sounds

like they're not exactly syched at idle. 

Which is stupidly hard to achieve, btw, and ALSO have them exactly synch on the throttle linkage.

 

There are a lot of 

reasons they can bind, and it's worth finding out why.

Because one of the reasons is that the plates aren't exactly

centered in the bores, and that will wear grooves into the bores.

Then each 'bypass air' groove will be different, and smooth idle

will become damned near impossible to achieve.

 

t

 

[2002Scoob]

On 5/22/2020 at 5:59 PM, TobyB said:

(those are formula 2 cars from 1955, mostly)

 

Does sound like your throttle plates aren't fully closing, tho.  The unevenness sounds

like they're not exactly syched at idle. 

Which is stupidly hard to achieve, btw, and ALSO have them exactly synch on the throttle linkage.

 

 

 

t

 

 

 

Oh, they'll fully close, but it's not a high enough idle to be really stable. maybe only 600rpm or even less. Super low to where the motor almost wants to stall.

 

The  5.5-5-5-5 examples were draw taken at higher RPM's. in the progressions. for around 900ish rpm according to the 123 app (I don't have a tach. Well... I do. But it's in a box, which doesn't do me a whole lotta' good, because BOY would it help to explain the what and where I'm feeling things) its at about 3.25, except for number one being just a tick higher. Maybe 3.5ish. When I set the carb sync rolled around to several RPM ranges with the idle speed screw and tweaked/measured/confirmed. 

 

I'm able to get it to idle pretty smoothly, with the AFR's being pretty dang solid in my book, fluctuating between 12.8 and 13.1ish. 

 

Tonight I swapped in the 135 jets with 175 air correctors and just went for a drive around town.

 

It did seem to help close the lean-gap between the progressions and the main jet, but on the scale of 

 

Light- just barely on the throttle to be able to accelerate-like you would in a neighborhood full of children, or in a slow city-center.

Medium- slightly more than light- you've already left the intersection and you're getting up to cruising speed.

Moderate- looking to get past someone in urban traffic with a little gusto

Spirited- Starting to have fun

Aggressive- You're looking for full power/acceleration.

 

I'm at the following. Note, this is steady-state throttle. If I punch it, it'll go lean and stumble straight-away. 

 

Light and Medium- is no problem. It's in the low to mid 13's, but does start to climb up into the low 14's before the mains come in and it drops down to low 13's again. 

 

Moderate into Spirited is where it starts having issues- while the gap closed a bit with the 135s, with moderate acceleration it's again in the mid 13's but climbs into the upper 14's/low 15's and starts to stumble. Just glancing at the wideband when it happens, the stumble starts to get induced around the mid/upper 14's. I assume there's a delay between the combustion and the sensor reading it, so the cylinders are probably lean before the gauge sees it. 

 

But once it gets into the mains it's fine, and from there I can goose it a little and she'll boogie without missing a step, so I'll assume it's good from there on up. 

 

So in summary- I'm Noticing 

 

1. Seeing a lean stumble with "STEADY STATE' moderate to lightly spirited acceleration in between the progression and main jet coming in in the middle of the rev-range, not engaging the accel circuit. 

 

2. Seeing a lean stumble when 'ROLLING INTO THE THROTTLE' with moderate/spirited+ accelleration at lower RPM's, which would be pushing into/past the progressions and would then be activating the accel circuit. 

 

 

Moving Forward

Either way, I think this points to I still need to enrich the Accel/pump circuit. I just don't know to what just yet.... I ordered a set of 60's, but something tells me that's too far and I'll be ordering a set of 55's soon thereafter. 

 

In basic DCOE Theory, Your Mains should be 4x your choke, which by having 34's is 136... so I'm not far off with the 135 from that. BUT, should I further try to close down the gap by going to a 140 and toss some bigger air correctors in for good luck? That 140 seems SOO rich to me for a main jet and DCOE 40's, considering it was pretty happy with 130's and smallish air correctors before...

But maybe it's not? Not sure I have 140's, but maybe I do. 

 

 

Easily Distracted Sidetracked Thought....

Or am I just barking up the wrong tree entirely, and are the air-corrector holes in Idle jets velocity/volume based like the air correctors in the main stack? (haven't found anything to suggest it so far) Because if that were the case... then i SHOULD somehow be able to run a smaller idle jet, but with a richer bleed-hole....

 

But when I tried the 50F9 and F6's before, things didn't go so hot... 

 

I'm just rambling and shit-shooting. And takin' my sweet time figuring this out. I'm appreciative of any and all opinions or thoughts!

 

Here's my Pizza i made for dinner tonight . Cuz Pizza is Awesome.  fake-steak(plant protein based, I'm actually 99% vegetarian these days, cept for some occasional cravings) Potato, and Artichoke

 

 

Edited May 25, 2020 by 2002Scoob