The House Doctor

Cam shafts and off idle performance

HenriSteyn
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#16

Post by HenriSteyn »

"This decreases the combustion temps and allows the plug to cool below its self cleaning temp and carbon foul."

I may be way off the mark here but maybe a cooler plug will stop the carbon build up?

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Wooky
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#17

Post by Wooky »

A spark plug needs to run in a certain temperature range to work as deigned.
This is usually ~400deg C to 850 deg C range at the plug tip.
If the plug tip temp falls below the ~400deg C carbon will build up and foul the plug as it is no longer being burnt off.
In this case more heat must be retained at the plug tip to keep it above ~400deg C so that the plug will burn off the carbon. This is controlled by the actual design of the plug.... this is a hotter plug.
A colder plug will dissipate heat away from the plug tip quicker

HenriSteyn
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#18

Post by HenriSteyn »

Thanks Wooky. I am a bit rusty from my two stroke racing days.

Cold plug = shallow recess = B5ES and down
Hot plug = deep recess = B7ES and up.

Something like that.....

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Wooky
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#19

Post by Wooky »

Close....

For NGK.... Higher number = colder
I currently have been running BPR5 plugs and now going to BPR4 as a test

Not sure about the numbers for other manufacturers.

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grips
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#20

Post by grips »

You said you have a modified dizzy from contact breaker to Electronic.
Does your modification includes a new coil. Most of the dizzy conversions I knows of uses the contact breaker coil
The R in BPR is for resistor. The Plug have a build in resistor. Plugs specially designed for electronic ignition systems. They fire at best with a super high voltage coil.
You might be using the wrong plugs for your ignition system.
You will never find me without Stroh or a 4x4 :D

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Wooky
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#21

Post by Wooky »

Actually swapped the whole dizzy for an electronic one so not a modified version.
Also fitted the correct coil to match (as per the dizzy instructions).... if I recall correctly it is a 1ohm 12v coil

You are correct about the R in the BPR being a resistor plug, but the resistor is only really a radio noise suppressor much the same as running suppressor leads or plug cap.
The standard plugs on the stock coil and points dizzy for the nissan 1400 (A14 motor) are also BPR5EY plugs

http://www.ngk-sparkplugs.jp/english/te ... index.html
Last edited by Wooky on Wed Jul 15, 2020 1:40 pm, edited 1 time in total.

HenriSteyn
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#22

Post by HenriSteyn »

Wooky wrote:
Wed Jul 15, 2020 11:23 am
Close....

For NGK.... Higher number = colder
I currently have been running BPR5 plugs and now going to BPR4 as a test

Not sure about the numbers for other manufacturers.
Others like Champion if I recall have the same number but just different letters

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Wooky
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#23

Post by Wooky »

HenriSteyn wrote:
Wed Jul 15, 2020 1:22 pm
Others like Champion if I recall have the same number but just different letters
I did find cross-reference charts on the net somewhere but never bothered to download.

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Paul#25
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#24

Post by Paul#25 »

HenriSteyn wrote:
Wed Jul 15, 2020 10:00 am
Thanks Wooky. I am a bit rusty from my two stroke racing days.

Cold plug = shallow recess = B5ES and down
Hot plug = deep recess = B7ES and up.

Something like that.....
Henri, the hot to cold numbering for NGK and Champion are opposite.
Somewhere in my "racing" file on my computer is a full NGK catalogue with the full explanation of what the different letters and numbers mean for the plugs. The new plugs with the iridium tips have an IR at the end of the number and their standard gap is 0.9mm not the standard 1mm or 1.2mm. It also gives a cross reference from their numbering to other manufacturers equivalent. It lists the standard plus for almost all car's, trucks and boat engines. It's a big file in pdf format but I can try send it to you if you are interested.
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HenriSteyn
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#25

Post by HenriSteyn »

Hi Paul.

Dont worry but thanks for offering.

Just curious and trying to remember.

Cheers

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Wooky
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#26

Post by Wooky »

Had the morning to test the hotter plugs compliments of Eskom.... :D

Looks like we have a winner with the hotter plugs.
Once the engine was warmed up I can now lean out the idle mixture 3/4 turn and still have a solid idle which it would not do before.
Idle is now in the low 14's in AFR - before it was ~13.5.
That leaned out the transition some and I had to raise the needle 0.5mm to get a clean pull back accelerating from a stop.
On road drivability is about the same but the 1500- 2000rpm misfire is almost completely gone (doing a low load, low speed crawl).

I would say about a 90% improvement at this point. Plugs are still black after holding the revs at 1500 rpm for a minute or so, but not nearly as fluffy as they were before.The rest I am sure I can get rid of with a bit of tweaking of the carb.

Will have her out on a trail on the 25th so that will give it a real-world test.

Thanks for all the input with this.....

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#27

Post by BushWacker »

Is that Motor the same as used in the little Nissan Champs ?
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Wooky
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#28

Post by Wooky »

It is from the same series of motors... the A series.
It has a lot of common components with both the 1200 and 1400 motors but has a 5mm longer stroke.

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grips
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#29

Post by grips »

What is the total timing at 3000 rpm ? Still think you should advance the timing a few degrees.
You will never find me without Stroh or a 4x4 :D

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Wooky
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#30

Post by Wooky »

Spent the day playing with it again on Saturday.
1/ Set the base timing up from 7 deg to 10 deg ( the next mark on the cover).... no real change to the condition at 1500 rpm so I reset it back to the spec 7 deg as I don't know the total advance in this distributor and at 7 she is pulling well in the higher rev range.
grips wrote:
Sun Jul 19, 2020 7:09 am
What is the total timing at 3000 rpm ? Still think you should advance the timing a few degrees.
Not 100% sure as I don't have a dial-back timing light. Timing marks end at 20 deg on the cover and I would estimate it to be in the region of ~25 deg at 3000 by adding an extra 5 deg spaced mark.

2/ Went through a whole series of re-jetting of the pilot circuit and needle. Went down as much as two jet sizes and leaned out the transition to barely drivable ( no accel pump) and the condition is still there and I can't say that all that much changed either. Plugs are still carbon fouling to a point of misfire but does take a while longer for the condition to occur.

3/ Tested the ignition system again. Built a 5mm spark test gap....Good blue to purple spark on all plug leads.
Oh and the HT circuit has healthy bite.... :lol:


At this point I am starting to think it might be a symptom of the actual modification to fit a side draught carb to a down draught manifold.
My intake adaptor was built as a test to see if I could get this carb to work but haven't got around to improving on it. It is a 90 deg bend which is not great for maintaining a well mixed air stream.... might be part of the problem.
Also the intake has been lengthened by about 150mm. Maybe this has set up a reversion pattern that plays havoc at 1500 rpm.

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