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3000rpm hiccup


Lucky Phil
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Not not interrupt @Chuck's reply,  but I rerouted my HT lead. Now to await some way of making a reasonable assessment of change once I get enough motor-minutes built up to get out again.

FWIW, here is another view of the right side of mySport showing the HT lead zip-tied closely to both the phase sensor connector and wire (lower left):

IMG_2772.JPG

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7 minutes ago, docc said:

Not not interrupt @Chuck's reply,  but I rerouted my HT lead. Now to await some way of making a reasonable assessment of change once I get enough motor-minutes built up to get out again.

FWIW, here is another view of the right side of mySport showing the HT lead zip-tied closely to both the phase sensor wire and connector (lower left):

IMG_2772.JPG

Ok cool docc. Remember I was looking at the huge change in ignition timing at the hiccup point a little while back and postulating on that as well. Did anyone adjust/play with that in Tunerpro and see if that had an affect? 

Ciao

Screenshot 2021-09-16 103308.png

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12 hours ago, Lucky Phil said:

Did the Centy hiccup as well Chuck?

Ciao

Yes. That was the *last* issue I had after I finally had it running perfectly, except it would hiccup very occasionally at 3400 rpm (from memory) The final solution was the brass temp sensor holder.

When I was playing with the CO setting on the Mighty Scura, I could get the hiccup when it was too lean, FWIW.

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23 hours ago, Chuck said:

That was one of the things I tried when sorting the Centauro back in the day.

It didn't help. :rasta:

Also on my '97 Sport. When purchased, the cam sensor was already bad. When replacing, I carefully moved everything away from the plug leads and coil bodies as much as possible- this really should be standard practice always. 
Still that dip was there, noticeable to me even after tuning the MyECU. What cured it was the timing gears. I still have no solid explanation for that.

I haven't even looked, are the plug cables replaceable? In any case where it matters or I have the opportunity, I use Packard-style USA made plug leads for replacement, or Nology HotWires in critical applications. EFI control is good in both. 

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2 hours ago, Pressureangle said:

Also on my '97 Sport. When purchased, the cam sensor was already bad. When replacing, I carefully moved everything away from the plug leads and coil bodies as much as possible- this really should be standard practice always. 
Still that dip was there, noticeable to me even after tuning the MyECU. What cured it was the timing gears. I still have no solid explanation for that.

I haven't even looked, are the plug cables replaceable? In any case where it matters or I have the opportunity, I use Packard-style USA made plug leads for replacement, or Nology HotWires in critical applications. EFI control is good in both. 

The plug wires are replaceable. I've heard of Nology, but what are "Packard-style USA made plug leads?"

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8 minutes ago, docc said:

The plug wires are replaceable. I've heard of Nology, but what are "Packard-style USA made plug leads?"

"Packard style" references the origin in the Packard Motor Company. Loosely, Packard style wires have a conductive wrap around the center conductor to absorb and redirect EFI, as opposed to using center conductor resistance to mitigate EFI. This also reduces the pressure to jump through the insulation, making them far more resistant and durable to rubbing and point failures. Nology is the best, FireCore has proven themselves to be without fault over 10 years of personal use, and I can't recall the name of the company in Cleveland that manufactures their own wires, and may be the source for 'USA' branded wires like Taylor, Moroso etc. which have pretty good history. FireCore and Nology will both custom make wires for you if you give them dimensions. With Nology, it's mandatory since you can't make them up on the bench.

As you know, the 'Sport hasn't had any electrical upgrades, so is running with the stock wires and new NGK caps.

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Worth a bash though.

I’m wondering what the hiccup or cough or spit is?  Like what’s happening?  It kind of feels like a pulse back thru the intake… Is it an intake shockwave, or some unburnt fuel popping into the exhaust?

My current V11 has it around the 2750 mark;  I recall getting my old bike to occasionally run very buttery without any pops whatsoever… buggered it i can remember how i dialled it out though!

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23 hours ago, Lucky Phil said:

Ok cool docc. Remember I was looking at the huge change in ignition timing at the hiccup point a little while back and postulating on that as well. Did anyone adjust/play with that in Tunerpro and see if that had an affect? 

Ciao

Screenshot 2021-09-16 103308.png

That timing advance at 2700-3500 rpm seems excessive, IMO. This is exactly where my Sport stumbles unless it is under the slightest load (slight uphill).

I would be interested in looking at the rest of that table, @Lucky Phil. Where could a fellow see the whole thing up to full throttle opening?

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39 minutes ago, docc said:

That timing advance at 2700-3500 rpm seems excessive, IMO. This is exactly where my Sport stumbles unless it is under the slightest load (slight uphill).

I would be interested in looking at the rest of that table, @Lucky Phil. Where could a fellow see the whole thing up to full throttle opening?

Here you go docc

std V11 2000.png

 

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It really is a pain as that part of the rev range is the ‘cruising’ section.  And also around-town-manoeuvring.

Forgive me if this is being thick, but is this all tied to the tps base setting?

I’m wondering if I got around the issue a few years back by setting the tps base setting a bit lower, or higher, than 157mv

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9 hours ago, Chuck said:

I personally think it is involved with fueling.. or maybe needing to be a little rich in that area to cover up poor ignition. :rasta::grin:

Interesting.  Today, another 70 mile checkride after moving the CO Fuel Trim from zero to +11 (an arbitrary figure I was using previously). I am reminded that the Fuel Trim only makes a significant difference at idle (throttle plate against the idle stop), but I figure it also influences this barely cracked (4.2º) traffic-slog hiccup.

So, at +11 today I had to work much harder at making the Sport hiccup. The brap-pop-crackle on deceleration with closed throttle is better (not gone) and the transition out of a corner from closed throttle is smoother.  Whether a greater increase of the CO Fuel Trim might further mitigate this 2700-3500 hiccup with barely cracked throttle is an opportunity for another day.

Again, as long as there is the slightest load (uphill, or wind resistance above 50mph/80kph), the stumble in those rpm at light throttle opening disappears. It also is not significant below 2500 or above 4000 rpm.

I am left agreeing with Lucky Phil that my Sport does not need 41-43.5º of ignition advance between 2700 and 4000 rpm at a steady 4.2º throttle opening. It seems reasonable that those steps should look more like the progression under the 5.2º sequence in those rpm ranges.

small.849923537_stdV112000.png.f1b2ac261

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The engine obviously has issues around this rpm/Throttle angle which is probably a combination of combustion chamber shape and burn speed, intake tract length, cam timing, header size and collector design. A "problem area". I don't know whether the hiccup is the engine missing an ignition ( skipping a beat for fuelling and ignition interplay) event OR it is "loading up" and coughing back into the inlet either because of a really slow fuel burn due to the much reduced advance that has the combustion still happening when the inlet valve opens again on the overlap. From my memory of my original engine it feels like the latter, a small cough back into the inlet on 1 cylinder. Adjusting the fuel could well mitigate it to a certain extent as might changes in engine and OAT. Just random thoughts but I'd be interested to see what effect an ignition advance change has.

The Daytona engine FWIW has totally different mapping in that area which is to be expected I suppose.  

Ciao 

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