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rough running after high revs


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dvderlm

Vehicle Wiring Products part 192175 female terminal.  

 

cable seal 0.5 to 1mm 192177

 

Junior power timer 192148

 

From the paper catalog

 

Is vehicleproducts.co.uk up?

 

 

 

 

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nice mpi conversion would solve all this 

https://www.ebay.co.uk/itm/141550095001?hash=item20f50b0a99:g:Y1IAAOSwEZdZ90xd

Nice new Hall sender cable. Crimped and soldered both ends. Used proper VAG plug and Micro Superseal 3 way  in convoluted tubing with good quality cable.        

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dvderlm
Posted (edited)

twice?

Edited by dvderlm
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dvderlm

Ran with 119/155 on ye olde Dignition... whose Hall sender plug is okay. Idle and low rpms are fairly rubbish, as not. enough advance for the twin carbs lower vacuum. 

 

At W_o_t which has same 30+5 advance as the Amethyst, I see AFRs from 11.3 at +0.305psi  to 14.3  at +0.387 psi 

So 155 air corrector is a bit too rich. 

 

Or faulty sparks, were causing wideband to think unburnt fuel was lean condition.

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dvderlm

 

The WR5DS did not foul when idle at 14, but low RPM (600?) due to Dignition advance expecting single carb and 19in Hg, not 12.

 

Cruise at 2500rpm ish was 15.3 AFR.

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dvderlm

Making the AMP plug have protruding pins was quite a fiddly job last time. Desoldered the plug pins, as they were extended with crimped solid copper wire in the DIY plug.

 

Soldered the existing DIY plug back to stripped and tinned leads with some new heatsink sleeving.

 

Refitted and idle is back to normal.

 

The multi strand copper wires I used are fairly thin (insulation displacement telephone extension wire in convoluted sleeving).  Lasted 4 years. I imagine they became brittle as they flexed, (and unplugging when testing compression finally did for the joint) so I'll make a better replacement with fatter 3-core automotive rated cable and a micro Superseal AMP 3 way to the correct 443906236 VAG plug (Amp 962379), got one in my spares box.

 

In the meantime I'll fill the insulating boot with some Sugru mouldable rubber glue to keep any flexing from vibration down.

 

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dvderlm

I also redid the main jets to be 122 with 182.5 air correctors (in .7 tube).

I wonder what the AFR gauge will think about that.

 

120 main with 190 air (in .5 tube) is good for a tuned Fiat 1290cc.

 

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dvderlm

122 is good over 3000 (12.4 to 12.8) but now appears to be too rich at the top end. Sure I saw it reach 11.9 out of the corner of my eye.

 

So 190 or 200 airs I guess.

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dvderlm

AFR log say 11.8 to 13.2 at +0.346psi

and 10.8 at +0.305psi. Hard to know if that as throttle closed...

but trend looks it goes from 13 down to 11 while accelerating hard.

 

Bigger air.

 

 

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dvderlm
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With 200 airs AFR log says 13.0 to 11.9 at +0.305psi.

Slightly cooler weather so lower ambient pressure I assume.

It sounded loud before this swap but it's now a more efficient vroom noise. 

 

Definitely richer as throttle closes from the log. A Porsche tuner says you can use this artifact to work out main jet/air corrector balance.

 

See the "roll-off" method bottom of this page of performance tuning part 2.

Performance Oriented

 

image.png.4fbf6a8edfd84ac53eb1e048b3d9e449.png

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dvderlm

Filled with Momentum 99 as the unleaded pumps already had E10 stickers on, although a piece of card said changing from September.

 

With that knock resistant fuel using 210 airs appears to level off the top end, so I see around 13 to 12.5 ish while accelerating hard, (the highlighted bit)

 

I tried to do the roll-off test - see the curve starting at 49:57 to 50:03 but it's a bit too easy to overshoot 5000rpm on the flat in third and then hard to ease off to 80% not 20%. I think it went from 12.35 to 12.1. Didn't feel dull or fluttery so inconclusive. Need a long hill or a dyno.

 

Hit the soft cut limiter too and it was much more refined than with a melted plug and dodgy Hall sender connection.

The Dignition's hard cut at 6800rpm (or 7140rpm with a changed crystal allegedly) used to  send the tacho needle bouncing around, in a "stop being silly, I mean it!" manner. This was more polite "I'm sorry sir, wouldn't want to destroy the engine, let's just ease off a bit shall we, bubububang, pop."

 

 

122_7_210.PNG.ce98cdd814266f8b032841fd4d9bd13e.PNG

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dvderlm

Nice new Hall sender cable. Crimped and soldered both ends.

Used proper VAG plug and Micro Superseal 3 way  in convoluted tubing with good quality cable.

16281032519383700399030067419496.thumb.jpg.cfa2edbd4a3706cf25c09f086fb77b5f.jpg

 

 

 

 

Edited by dvderlm
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dvderlm

The Sugru repair in the old lead has also worked well. The rubber boot is quite hard to peel away now the rubber glue has hardened inside it. This means the bare  leads can't waggle. Covered with insulation they should be safe from breakage too.

 

Of course it might fail at the Amethyst end...

 

So gonna carry the new Hall sender cable as a spare.

And 4x W4CS plugs.

And some SAEJ30R9 7.9mm fuel line.

 

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dvderlm

I've not observed the positive pressure peak of +0.428 PSI since the rough running journey. It's not the short trumpets then...

 

Doing a long journey soon, so I can look out for it. 

 

 

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dvderlm

The pressure is read at inlet manifold and AFR about 80cms down the exhaust pipe.

 

Could I be seeing lean 15.2 from misfire due to plug, but high pressure from reversion overlap pulling in fuel NOT burnt in exhaust?

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  • 2 weeks later...
dvderlm

Well the long journey went reasonably well. No melted plugs using Momentum99 then some BP Ultimate 97 (£1.47 a litre!) over 450 miles. Fuel gauge descended quite slowly too.

 

But the incredibly bumpy M54 wrecked the satnav's USB micro cable connection.

 

However, 122 main is overdoing it. I saw as rich as 11.6:1 AFR climbing uphill.

Not at high enough revs for the air corrector to be in play, say 3500rpm.

Idles serve up to ~3200rpm apparently.

122 main is a 5% cross section increase over 119.

So I could try just a 1.7% increase using 120 mains and then ream if not big enough, so long as I can do four the same... else 121 mains.

 

Or an emulsion tube with more holes. Sure I've got some very holey 10 tubes somewhere. Definitely got some 5 tubes. 

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dvderlm

Need to drive up a hill with the .5 emulsion tube.

 

Drilled four skinny 98 mains with a 1.20mm drill bit.

Cheaper than actual 120 jets, and probably made a tad larger 1.205mm hole

in the brass.

 

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