Spark plugs

Road-race engines and ancillaries - general discussion
Sandro
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Re: Spark plugs

Post by Sandro »

Hi,

the pictures make it clearer thank you... apologies for the delay in replying to you....

As for the smaller plug, the tip is significantly retraced so there will be a difference in combustion, however, I was told by the Alfa Engineers that if you removed the small plug and blocked off the hole on all cylinders you would lose only 4-5 Hp (so the effect of this plug on the performance should be minimal)...how true this is I cannot quantify this is what they had told me at the time I was working on these engines. I was also told that the Alfa Twin Spark 1.8 and the Barchetta engine are the same except the cylinder head, I believe blocks are common, known as the B family within Fiat - digressing sorry...

Anyway...you have done the correct thing with regards to the small plug, going a heat range cooler from 7 to 8 but keeping the firing end the same so we can close this side of the discussion off.

As for the main plug, you say the double ground electrode design is the OE version if that is the case it must have changed because when I was testing these engines it was a single ground electrode design similar to the BKR8EIX, this must have changed later on. As I said earlier on the idea is to try and push the spark position further into the chamber on std engines to ensure it is away from the cylinder head so flame propagation is not affected. On race engines you tend to to the reverse as you have improved the mixture preparation, increased CR etc, so the spark position is retracted, also for reasons of ground electrode temperatures etc. F1 engines do not have ground electrodes as such for example.

I am still confused why there is such a huge difference with the two designs you have tested, I agree there will be an effect but to the point you notice it, I am surprised. You can also get a single ground electrode design with 5mm spark position but you need it in a "7" or "8" heat range NGK. What you may want to do is try to find a cooler version a design with a 5mm spark position, single, double or more ground electrodes. The 4 ground electrode design you mention BKR7EQUP is actually very good from an ignitability point of view despite it being a multiground electrode design. This is because it has a very long spark length. The spark travels semi surface, ie partly over the ceramic core nose and partly in air. This allows you to manitain sensible voltage demands. I will be interested to see what you think of this design, I found it very good in my Fiat 2l 20v when I tested it 5 or so years ago, also dyno test results on ignitability showed the same. This being a "7" is cooler than the "6" two ground electrode design so it is the direction you need to go. If this design works well I would go this route on this engine, this is the design that was developed for BMW by NGK, (I think for all BMW 1990 on for the aftermarket if I rememeber well) so you are sure it is a good design.

I still want to understand why the difference in performance between the two and single ground electrode designs....I will

Any questions let me know....hope I have helped
GC_33
kpsig
Posts: 35
Joined: May 10th, 2008, 6:41 pm
Location: Greece

Re: Spark plugs

Post by kpsig »

Sandro thanks for your reply.
Finally, BKR7EQUP (4 ground electrodes-Q, Platinum-P, semisurface discharge-U) are performing exceptionally well.
In the meantime I did a lot of research and I found that some people who replaced BKR6EQUP (1 grade hoter than mine, all other aspects the same) to their supercharged Mini Cooper S with BKR6EIX (and -7EIX) had some degrade in performance. So, after a lot of fuss with local sellers of NGK products (the ones who proposed this plug...), they found out (themselves, not the sellers) that NKG in USA actually proposes strictly ZFR7FIX for their cars, which is basically the same with BKR7EIX BUT with 5mm projected tip!! So, it seems that this kind of plug (iridium) is very dependent of its tip intrusion to the combustion chamber.
Most probably, this plug would also perform well in my case. But no other tests, thank you!

The replacement of CR8EIX with PMR7A (small plugs) was worth a lot more than a mere 3-4% hp difference the Alfa engineers suggest (5/150)
My Alfa's engine now with the proper PMR8A and BKR7EQUP the performs very well. Just to give you an idea, It can easily follow 2.0 V6 Turbo Alfa 166 without going beyond 6000 rpm. However, I think I must retard advance a little or make the mixture richer (more on that next week). I can hear some very slight detonation.
Tomorrow I will do a long trip with super unleaded (100) so I will have the chance to see exhaust temperatures with accuracy.

At the same time, BKR8EIX will go into my 205 trackday car with its 106 Rallye 8V 1600 engine (12,5/1 CR, Honda CBR600 ITBs, Megasquirt, 8 injectors etc). Those plugs ARE suggested by NGK for those Peugeot motors. I am very curious to see how they will perform there. Good thing is that my Megasquirt is fully programmable in all aspects (in injection sector among others i can alter dwell time, discharge time etc).
Kostas, Greece
Sandro
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Joined: August 30th, 2006, 12:30 pm
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Re: Spark plugs

Post by Sandro »

Gents,

an interesting article on F1 spark plugs from my racing collegue in the US.....Guy the file is big unfortunately it came for the US and its a pdf. I dont have the original, and I dont have the software to reduce it sorry.

The plugs fitted to the Renault engine that failed at the start of the season we not ours as the article says. I was involved in the meeting renault called us to to discuss continuation of spark plug supply to their F1 team. We had been supplying them for 20 years, 15 of which free of charge, and they decided they wanted two suppliers homologated so they could switch whenever they wanted. However they wanted us to be a back up supplier to our competitor that could not make our M8 design, so they changed to an inferior M10 design, losing power in the engine in the process, we declined to supply. In 20 years we have never had a spark plug cause an engine to fail. It took our replacement one race to do so.

In summary its a shame we are not supplying them anymore, we did have a good relationship over the years with Renault, and I do try to keep the racing division alive.....just.....

regards

sandro
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MinorTC
Posts: 83
Joined: April 28th, 2009, 9:30 pm

Re: Spark plugs

Post by MinorTC »

I fitted a new set of Champion NY7CC spark plugs, and set the ignition timing to 10 degrees BTDC @ 850rpm (at least, I assume it was 10 degrees - I timed it to the last (4th) marker, third marker away from TDC on the silver cambelt cover; can anyone confirm this to be correct, as the Haynes manual showed only 3 markers in total, including TDC?)

The performance is greatly improved, as before it was running N9Ys which as we know are too hot, and the timing was on TDC!

However, having had these in for a week of running about, I checked them today and noticed that No 1 spark plug was sooty whilst the others were suspiciously clean! Can anyone advise as to what may be causing this? I did a compression test back in July and all four pots came back with 190psi. Carb is the standard single Weber 34ADF 15/250, air filter is new. Starting is easy enough, and it runs fairly smoothly.
Sandro
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Re: Spark plugs

Post by Sandro »

Hi,

it sounds like you have one cylinder not burning correctly or and my first concern is related to the electrode gaps. Have you checked these, it may be that on number 4 it is a little smaller than the others. From memory the gaps should be around the 0.8mm mark but you can go a little higher if needed but ultimately they need to be all the same.

If the gaps are all the same try changing the fouled plug into another cylinder and if it represents the same issue then you have a faulty spark plug.

I doubt it is carb related as it is a single carb so I would assume if it was running rich all 4 would foul.

Assuming you have checked the ignition lead connections on to the plugs and the distributor cap as well as the condition of the internal part of the distributpor cap.


let me know how you get along..

regards
Sandro
MinorTC
Posts: 83
Joined: April 28th, 2009, 9:30 pm

Re: Spark plugs

Post by MinorTC »

Thanks for tips, Sandro :)

I did as you said, and swapped the plugs between No.s 1 & 3 cylinders, and it's still running richer on No. 1 than the others. The gaps were set correctly at approx. 0.8mm.

I checked the resistance of the plug leads, and all came in at between just over 1 and 1.5 kilohms, also checked the distributor cap and all seems well.

So, although the engine for the most part runs smoothly and with quite decent power and torque, it does occasionally feel a little lumpy as if running partially on 3 pots. It has now covered 500 miles since rebuild (by previous owner) and doesn't use oil or water, so headgasket is presumably OK.

Somewhat mystifying...
WhizzMan
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Location: Amsterdam, the Netherlands

Re: Spark plugs

Post by WhizzMan »

Since this is a single carb setup, I suspect false air coming in between the head and the carburetor for 3 of the 4 cylinders. Can you check with brake cleaner or something to rule that out? Is your exhaust manifold not blocked for the one cylinder?
MinorTC
Posts: 83
Joined: April 28th, 2009, 9:30 pm

Re: Spark plugs

Post by MinorTC »

Today, I removed the air filter assembly and took a good look at the carb. Checked the inlet manifold nuts for tightness - all good, and looks to be a new gasket. The exhaust manifold, a tubular 4-2-1 item, was removed last summer, and I don't recall seeing any blockages. The exhaust note certainly sounds normal.

I did discover, however, that the throttle wasn't fully opening both choke butterflies, so adjusted it all to achieve near to, but not full opening (I think a new cable is required before full opening will be possible, as I am using a Fiat throttle cable with a Marina pedal box, and the Marina pedal doesn't provide alot of movement).

Although it runs quite well, again I encountered the momentary missing and backfire along a stretch of dual carriageway tonight.

Perhaps this is a normal characteristic of these Webers?
Sandro
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Joined: August 30th, 2006, 12:30 pm
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Re: Spark plugs

Post by Sandro »

Hi,

assuming the compressions are still all good as you said you measured them last July if I remember correctly...

has anything changed since then? If there was an air leak the cylinder would run lean and not soot up in theory.... but I wonder if it was so lean that misfires left unbrunt fuel in the chamber that then once the cylinder fired would be overirch...if it is an air leak on one cylinder it would have to be a gasket leak or....is the cylinder that soots up the one that has the vacuum take off in the manifold, I cannot remember where the vacuum take off is on single car set ups and this maybe a silly option.

You need to isolate any items that relate to that cylinder, which from what you have said you have done. Distributor cap? have you tried a different one?

Just a question, when does it misfire or sound as if it is misfiring? under what conditions, engine speed and load?

are you sure the valves are opening fully , ie the cams are not worn on that cylinder? Im clutching at straws here sorry...
MinorTC
Posts: 83
Joined: April 28th, 2009, 9:30 pm

Re: Spark plugs

Post by MinorTC »

Hi Sandro,
No need to apologise - clutch at as many straws as you like! ;)

The misfire mostly occurs while on a dual carriageway, cruising along at say, 60mph, but also occasionally misses when accelerating hard. It literally feels as though the engine has cut out, then it backfires and picks up again and all is well for some time after that.

I also was wondering if the valve shims have been correctly set up, as the engine does sometimes sound a little tappety, but then I don't have any previous experience of Fiat twin cams (or any engine that uses shims to set valve clearances), so this may be quite normal. After all, the E30 M3 S14 engine also has shims and they can be rather tappety.

I'm going to try reverting back to the original block-mounted mechanical fuel pump, as I suspect that the Facet electronic pump may have something to do with it.
Guy Croft
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Re: Spark plugs

Post by Guy Croft »

I think that misfire & backfire fault is the LT ignition system not plugs and carb.

Sorry but to save me reading from the beginning again - what is the ignition system on this one?

G
MinorTC
Posts: 83
Joined: April 28th, 2009, 9:30 pm

Re: Spark plugs

Post by MinorTC »

Hi Guy,
The ignition system is a Lucas 2CE 'Constant Energy Ignition Unit', made in the UK. It appears to have the same basic connections as the Magnetti Morelli AEI 200A. Certainly, it is an electronic system, as there are no contact breaker points.

Today, I have reverted it back to the standard engine-mounted mechanical fuel pump, and so far, so good...
Guy Croft
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Re: Spark plugs

Post by Guy Croft »

I'd like more detail on that ignition system - distr type esp. Have you in fact wired the Marelli distr to the new amp unit?

A photo or two would help.

G
MinorTC
Posts: 83
Joined: April 28th, 2009, 9:30 pm

Re: Spark plugs

Post by MinorTC »

Hi Guy,

The distributor is the engine-block mounted one, with Magnetti Marelli cap. It came pre-wired to the ignition coil/amp and I presume it to be a standard Fiat fitment:
Image

Some shots of the electronic ignition module:
Image
Image
Last edited by MinorTC on February 15th, 2011, 4:25 pm, edited 1 time in total.
Maurice,
East Kent.
Guy Croft
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Re: Spark plugs

Post by Guy Croft »

I'm not sure I can find what I need in those photos (BTW please delete the last as it's just a blur).

What I was trying to discover was whether you had married a Marelli (same applies to Bosch) electronic distributor to a non-Marelli powerpack because that is inadvisable - it may be imcompatible and cause misfiring.

G
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