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 Tach flutter 
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Joined: Sun May 12, 2013 5:21 am
Posts: 319
Location: Michigan
Ok been chasing a tach flutter at high rpm only, the last 500-800 before shift. As well as some other problems with the car and now I'm pretty sure it's electrical or ignition related. Awhile back someone suggested valve springs and that was plausible but after I just installed a new better set at the correct install height, the problem is still there. I've also done many fuel system changes to correct any possible issues.

In fact after I leaned out the carb some it got worse and happens with less intensity at lower rpm(4000ish), that is why I am pretty sure it's weak ignition. I am currently using a HEI with msd green module and have tried to re-wire the coil, plugs, change coils, plug/coil wires, make sure it's well grounded and powered, new alt. I also tried to change to a Mallory dist but that was a mess. Plug gap is .040 barely 8-1

It has also been suggested by tuner that it could be a faulty battery and after I change to a msd setup I'll try that if it persist.

Also it is still possible it's just the tach(it's well grd and not doing it at idle like the common grd problem)

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Tue Jul 05, 2016 8:36 pm
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Joined: Fri Feb 08, 2013 2:37 pm
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Now, you are describing a "tach flutter" .... but I think (thought) previously you were describing a misfire.

About a misfire, I recall relating to you (and others) a problem a friend had with an engine that would not RPM clean above about 6000 and acted as if the ignition had a rev limiter, and in that particular case an Optima AGM type battery was the culprit.

Are you confusing the suggestion that your alternator may have a diode problem with this??


Tue Jul 05, 2016 9:05 pm
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Joined: Sun May 12, 2013 5:21 am
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Location: Michigan
I just included the alt in things I changed to rule out weak power source or w/e. Not that I changed it because of the flutter, that was because of the Mallory dist issue that is prob that dist being faulty.

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Tue Jul 05, 2016 9:46 pm
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Sorry I'm old and getting absentminded, but you are saying "tach flutter" and I don't understand what you mean. Does the engine actually misfire or is it just the tach needle acting erratically?


Tue Jul 05, 2016 11:39 pm
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Joined: Fri May 20, 2016 5:18 am
Posts: 105
tuner wrote:
Sorry I'm old and getting absentminded, but you are saying "tach flutter" and I don't understand what you mean. Does the engine actually misfire or is it just the tach needle acting erratically?


tuner are you sure you're not Absinthmined like other high intelligent open minded creative effective artists,
might bee better than absentmined i am not sure haven't tried the first one "yet" :O


Thu Jul 07, 2016 5:07 pm
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Joined: Sun May 12, 2013 5:21 am
Posts: 319
Location: Michigan
It's not the ignition I think, just installed msd 6a box, new billet dist, and tfi coil with new wires.

I'll either try a new batt or tach next.

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Sat Jul 09, 2016 7:03 pm
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Joined: Fri May 20, 2016 5:18 am
Posts: 105
If the ignition is "weak" it will show at the rpm when the combustion is such that it puts the most demands on the
spark. It can bee of all kinds of different reasons related to combustion procedure as carb tuning ignition timing
together with cylinder pressure for example.
I remember back in late -80is when we was racing a -71 HEMI Cuda in A/SA (YEAH a matching number car) back in the days when NHRA stock still was a stock class. After relocating the MSD box to the trunk we got a "tach flutter"
between 4500-6200 and above that it was "clean" up to 7000. It was so small you could not hear it in or outside the car going down track, and the driver didn't see it at first.We first noticed it looking at the run on the eminent
re playable tach with a very small tape recorder and loudspeaker (those days racepack) and it didn't show on time slip any particularly either that suggested there was any problem. The problem was us wiring all cables along side with each other between the engine and the trunk, disturbing the "signal" wiring from the MSD box.
Why just "fluttering" between 4500-6200 because that's when cylinder pressure was at is highest and putting the most demand on the spark.
We cured the problem with using a parts twisted cable like you use for computers.
Howe we did find out? Skinne brothers "prostockers" way up in Norway told us when we went to Norway to dynoing the engine it was something like 450 miles one way trip from south Sweden wear we is living. When we addressed the problem we had they immediately responded that it was wiring problems. They had experienced something similar putting a new 90 hp on the dyno stronger engine in there pro stocker and it went .15 sec slower.
The ignition in the car could not cope whit the higher cylinder pressure in the new engine but with a better wiring "parts twisted" the same ignition went along just fine.
What! how much the stock HEMI made on the dyno, 586hp and i can tell all of you, reading what tuner tell us
about how god calibrated muscle car carbs really was "back in the days". That engine was serving us fore 7 years with the compleat original stock carbs with staggered jetting 2 numbers up on sec jets and "spives"on the boosters and those carbs never ever gave us any problems. It was a complete "turn key operation" the performance tuning of the car was all in the chassis, converter, suspension .
What! how fast was the car? 10.71 A/SA 10.80 B/SA NHRA legal in 1993. then we quit racing it.
That 71 HEMI Cuda held the European A/SA record for 10.years after racing service.
Sorry just an old man babbling

l


Sat Jul 09, 2016 9:09 pm
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Om de gamla män inte babbel, unga män inte lära sig någonting.


Sat Jul 09, 2016 10:38 pm
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Joined: Sun May 12, 2013 5:21 am
Posts: 319
Location: Michigan
Forgot to mention I'm gonna close the gaps on the plugs before I buy anything else.

I twisted the main power and grd(10ga both, it start just out of the shot) to the batt up until they split off, I also used shielded twisted wire for the signal(routed away from the coil). The coil wires come out of the same side of the box as the main power, so can't do nothing bout that but I shorted the coil wires about two feet to keep it clean. I try to leave nothing to chance. edit: 18" coil to cap wire only.

Image

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Sat Jul 09, 2016 10:49 pm
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Joined: Fri May 20, 2016 5:18 am
Posts: 105
Closing the sparkplug gap to "investigate" the performance or rader "chasing" a combustion
problem one think you may have is certainly one of your tools in the toolbox.
the same way as opening or closing them seeking to gain more power.
All this "combustion stuff" is in the upper region of understanding high tech relationship
between interacting components as Compression, Fuel,combustion chamber layout,intake exhaust runner
length volume,headers, laminar ore turbulent flow and so on and on but just because its very complicated to trying to understand" fore me anyway" don't let it hinder you from"asking the engine" what it likes as MR.tuner would putt it.
VW has doctors and professors in combustion engine technologi spending millions and millions of dollars trying to figuring out (and other company's as well) how to gain more power with less fuel and environment harmful exhausts, and they do have the equipment we haven't heard of yet.
When they fail to live up to the demands of legations they cheat sorry to say and so is other company's doing as well i believe.
Just keep on trying asking and reading on forums like this and open your ears up when people like tuner and jmark is talking and especially the late MR. shrinker. His powerful voice can still be heard of thanks to internet.


Sun Jul 10, 2016 7:20 am
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