It doesn’t ping at all, it hesitates occasionally but I think that’s a PV thing, it also does it when it’s cold. It doesn’t spit out the top of the carb or anything like that either, just kind of bucks every couple seconds if I get on it too much when it’s too cold.
Fine Tuning a 360 Magnum with a Brawler "Double Pumper"
- Thread starter jmanhoff
- Start date
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How are you determining when the booster starts?
I can see it in the O2 sensors. You can’t miss it.
With the engine at operating temperature I would set the idle mixture correctly and see if any drivability issues crop up when driving on the slot. See if the powervalve adjustment fixes your lean tip in then go to work on your timing. anything cold related might be a separate choke issue. You can ballpark the choke so it isn't miserable to drive but I would get everything sorted with the motor at operating temperature first then dial the choke in.
If your choke is still behaving like it was in the video back on post 19 it's because either the choke pull off is misadjusted ( needs to pull open farther) or it's not working.
By looking in the carburetor and watching the booster for the moment fuel begins to discharge from it.
I have for the most part figured out the basics of the choke and how to get it setup. I have the choke setup currently where it’s not pig rich at a cold start, it idles somewhere around 12.5 at first then slowly creeps up to 13 or so. It’s at a point where I can actually drive immediately after starting the truck, which is not something I’ve been able to do before. I have the choke set to open slightly sooner as this engine doesn’t like a lot of choke, and the fast idle is setup to be about 1500rpm when fully closed
This is probably a stupid question but what could cause the idle to randomly be lean and randomly be rich? I tuned my idle at temp before going on a drive and set it to peak vacuum and backed the screws out a bit for cushion, and after the drive it was idling super lean and surging. This happens semi-often, especially recently.
Is it likely just something stuck in one of the IFRs/IABs? Or could it be some sort of intermittent vacuum leak say from the brake booster or something?
Is it likely just something stuck in one of the IFRs/IABs? Or could it be some sort of intermittent vacuum leak say from the brake booster or something?
TT5.9mag
Two atmospheres are better than one
Could be trash in the carb, could be a vacuum leak, could be exhaust leaks, could be misfires, could be the o2 is too close to the end of the pipe, lots of possibilities.
PRH
Well-Known Member
I’m not saying this has anything to do with the OP’s current complaint, but is more of a general observation…….
While a/f ratio gauges have greatly help a large percentage of people tune their own carbs, I feel like some people spend too much time “chasing the numbers” and have lost site of what I feel is a more fundamental element of carb tuning…….which is……it has to “run good”.
Regardless of what the gauge is telling you……if there are some unhappy driveability antics being observed during operation…….the carb isn’t doing what the engine wants.
Rule #1……..it has to run right.
While a/f ratio gauges have greatly help a large percentage of people tune their own carbs, I feel like some people spend too much time “chasing the numbers” and have lost site of what I feel is a more fundamental element of carb tuning…….which is……it has to “run good”.
Regardless of what the gauge is telling you……if there are some unhappy driveability antics being observed during operation…….the carb isn’t doing what the engine wants.
Rule #1……..it has to run right.
Yeah I’m using the afr as more of an aid now. My peak vacuum at idle is at around 13.3 AFR, it starts to surge at around 15.7 afr cruise, etc. I mainly use it to see when the engine starts to struggle from being lean.
I can watch the AFR dip lean and the vacuum dip down as well, and have been using that as well as the sound of the engine and how it feels in the seat, etc, to get an idea of what’s happening and what I should ask on here.
I ordered a 10.5PV and I’m probably going to get slightly larger TSRs in to get a better starting point and experiment with it and go from there.
Mattax
Just the facts, ma'am
Maybe. And of course changing the PV could prove or disprove that.
^^^This. I'd not be surprised if this is still one of the main issues.^^^
Vac advance connected? If so, do what someone else suggested. Go mechanical only and the engine will better tolerate the less then part throttle and light throttle ideal timing.
That's what Shrinker would do.
You all know what I've done without a dyno as I've posted it a few times.
If its not Timing, then it could be how you are setting up the idle mix. Or somehow the fuel is getting real hot. Seen this with open air cleaner and winter fuel in hot weather.
A lot of things change from when the engine is cold to when its running fully heat soaked.
Not sure what you think the relationship of these are???
IMO 15.7 AFR is a very lean cruise. How fast is the truck moving? What's the rpm?
It cruises at 15.7 at 45mph, in OD so around 1600rpm. At 65mph in OD it’s around 15:1 at 2100rpm, I’m assuming the boosters are starting to come in at this point
I do have an open air cleaner but I’m not running winter gas, not cold enough here yet for that.
I have the vac advance hooked to ported, but obviously it is doing something at cruise so I’ll leave it unhooked for now. Going to dig around to see if I can find my timing adjustment set that I ordered awhile ago. Last time I checked my mechanical timing it adds 20 total all in at ~2500. I backed initial down to 16, so 36 at 2500
I do have an open air cleaner but I’m not running winter gas, not cold enough here yet for that.
I have the vac advance hooked to ported, but obviously it is doing something at cruise so I’ll leave it unhooked for now. Going to dig around to see if I can find my timing adjustment set that I ordered awhile ago. Last time I checked my mechanical timing it adds 20 total all in at ~2500. I backed initial down to 16, so 36 at 2500
Mattax
Just the facts, ma'am
@92b I don't want to revive another thread for your sidebar there.
A. Outstanding experiment.
B. We can see that of the variables changed, the biggest impact effecting the booster start rpm is the load. That makes perfect sense because the main system is driven by air flow.
C. In my opinion your experiment fits well with the published graphs from the old books Tuner and Shrinker shared and posted about. IF the emulsion holes are ballpark correct, then the primary job of the main air bleed is AFR correction at high rpms (higher MAF). Main circuit initiation is, or should be, impacted by the upper e-hole(s) and to some extent a 'kill-bleed'.
So my prefered approach, is idle - off idle, then some degree of drivability, followed by a full load test with WBO2. That could be drag strip, or IMO better, chassis dyno. Chassis dyno has the advantage of better controlling the variables and being able to run 3rd (or 4th gear) through the power peak. Other than drag race focused cars(trucks), we're through the 1/4 mile well below peak HP. When looking for AFR drifting richer or leaner I want to see max load at max rpm. Once MAB is there, I'd leave it unless a majpor change is made to the jetting and/or PVCR. I know Mark Whitner and others prefer to stay in sequence building the tuning of each circuit from idle up but I htink for a lot of us its often more practical to jump ahead to some full throttle tests and at least see if the AFR is staying flat.
Mattax
Just the facts, ma'am
Depends on the engine load. At 65mph I would normally think so too, but 2100 could be fairly low throttle position.
I've posted how I've found it when out its really on the main circuit. Not saying you should do that, but its a method. Depending on how the rig is instrumented you could do a less drastic step test.
Its not about the air temps. That would be too logical but also logistically a nightmare. Unfortunately its as soon as the refiners can switch over legally. Winter fuel is cheaper to produce.
We can look up the dates. Hopefully its not for another month as I forget when the regs permit it.I'm not going to repost about this. TT5.9 has more experience with magnums that I by far, and I think we agree.
Just thought I'd pop in and see how you're doing.
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Yeah I’m kind of throwing everyone in a tornado right now lol. Entirely new environment, and I was halfway into dialing in my tune on the carb with a different cam. Now I have a new cam, new environment, etc so every variable has changed.
Read post 560 over and over until you get it.
Turn off the O2 sense and make it run. Look at the plugs and learn to tune and THEN go back to the O2.
You can NOT tune to a number. Give it what it wants as best you can, look at the number and the tune it.
Then it’s most likely you’ll need to change the timing curve.
A decent ignition will fire 16:1 on flat ground. When you get the PV opening at the correct time it might help with that.
Okay the misfire thing actually makes sense. I watched a video from thunderhead289 yesterday about setting idle mixture, and he said to set it to the FIRST point of highest vacuum, meaning set the plugs out about 1.5 turns, and turn them until they read the peak vacuum the first time. Then back out a bit. The idle smells rich, that’s why I’m thinking it’s rich but I get I’m not used to not having cats lol.
I know this truck can run 16:1 with the ignition setup I have when it’s cruising flat. I’m watching the vacuum gauge and listening to when it sounds like it’s starting to sputter in a low gear at cruise speed which ends up being right around 10.5, but I think with the right TSR and PV tuning I can make that work and maintain my lean cruise at flat ground.
Should I read the plugs for idle or is that really something that never works because every engine wants something different to idle?
I know this truck can run 16:1 with the ignition setup I have when it’s cruising flat. I’m watching the vacuum gauge and listening to when it sounds like it’s starting to sputter in a low gear at cruise speed which ends up being right around 10.5, but I think with the right TSR and PV tuning I can make that work and maintain my lean cruise at flat ground.
Should I read the plugs for idle or is that really something that never works because every engine wants something different to idle?
Mattax
Just the facts, ma'am
IMO you're forcing it. if its 16:1 at cruise what's the AFR go to as the throttle opens and load increases? 18:1 ? 20:1? Yea its possble but I suspect not in this case.
As far as setting idle mix, that's a partial description, very partial.
In post #560 Duane basically said in his own way, what I always write, tune for performance.
As far as setting idle mix, that's a partial description, very partial.
In post #560 Duane basically said in his own way, what I always write, tune for performance.
When cruising it stays around 14.8-15.1 when I slightly open the throttle. More throttle it stays lean but my PV isn’t opening like we said. When my 10.5 shows up I’m going to open both sides of the carb and spray them down, spray out the ports, etc. and start over for tuning. I think a .080 tsr or so will give me a good start and I’ll go from there. Also going to see if I can find my dizzy stuff, if not order some.
Mattax
Just the facts, ma'am
Power valve should not open until the primary throttles are getting close to fully open.
The engine wants leaner fuel mixtures as the throttle opens further - until it hits a point when the load is so great that it starts need richer mixes again.
See the graph from Larew that Tuner shared and I marked up here
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The link didn’t work for me, but I thought the whole purpose of the power valve was to provide extra enrichment when load is high (vacuum low), not based on the throttle opening? If it was to open at basically full primary throttle wouldn’t that defeat the purpose of allowing the jets to be leaner for low-mid throttle normal driving?
Mattax
Just the facts, ma'am
Correct, When on the main circuits and the load is high. Accelerating a bit or going uphill on the interstate should not be anywhere close to heavy load. Working up the steep sides of a western Virginia hill might get there, or puling a boat out of the water on a trailer, or things like that, in addition to the obvious.
Fixed the link _ hopefully. Forum software still doing weird things.
Fixed the link _ hopefully. Forum software still doing weird things.
So on a normally setup DP, half throttle is just about 75% or so open on the primaries right? Give or take.
If I’m feeling it right, I think I can tell in the pedal when the secondaries are about to open because the pressure on the gas pedal changes, feels like the cable gets stiffer (the linkage getting ready to move on the secondaries). When I’m cruising at 45 in high gear on flat ground and I get on the throttle, this is around the point where I can hear the engine start to bog/sputter (which happens at about 10-11 inches vacuum). Does this mean I should still be looking at a 10.5PV?
I would imagine this would overlap with lower throttle input on a grade with payload or something. Or is that going to be way too much enrichment too early, and I would not really be able to easily tune a true WOT scenario because the PV is dumping its fuel early
If I’m feeling it right, I think I can tell in the pedal when the secondaries are about to open because the pressure on the gas pedal changes, feels like the cable gets stiffer (the linkage getting ready to move on the secondaries). When I’m cruising at 45 in high gear on flat ground and I get on the throttle, this is around the point where I can hear the engine start to bog/sputter (which happens at about 10-11 inches vacuum). Does this mean I should still be looking at a 10.5PV?
I would imagine this would overlap with lower throttle input on a grade with payload or something. Or is that going to be way too much enrichment too early, and I would not really be able to easily tune a true WOT scenario because the PV is dumping its fuel early
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