Author Topic: *** Spark Plug Q\'s & A\'s for the FD RX-7 ***  (Read 27186 times)

Offline Glenn Butcher

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« on: December 20, 2002, 02:01:11 PM »
Special thanks to Philip Palmer for helping me compile this document.

Spark Plug Q & A









Spark Plugs Q & A for the FD (3rd Generation) RX-7

Q. Why did we put this document together?

A. There appears to be some misinformation out there on what type of Spark Plug to run in your (non-racing) "standard" 3rd Generation RX-7. So we thought it would be a good idea to put this together. Of course - everyone has their opinions on spark plugs, however there is some good information here, so you may or may not change your mind by the time you get to the end of it.

Spark Plug recommendations from the Mazda Factory Manual:

Plug Position
NGK
Colour
Leading Side

BUR7EQP*, (BUR7EQ)

(BUR6EQP), (BUR6EQ)

-
Trailing Side

BUR9EQP*, (BUR9EQ)

(BUR8EQP), (BUR8EQ)

Blue
P - Denotes "Platinum" - which is the standard plug
* - Standard Plug

Pictures

"Click"Click"Click

Note the "L" and "T" underneath the plug number on the pics. above

Plug Diagram

Spark Plug "Temperature Ranges" and what they mean:

The lower the number, the "warmer" the plug. The higher the number the "colder" the plug. I.e. A heat range "7" plug, will run much hotter than a heat range "9" plug.

What does this mean?

A "warmer" plug cleans itself during normal running by burning off the excess carbon etc.. It will start cleaning itself quicker on start-up and can reduce the occurrence of the infamous \'Flooding\' problem.

A BUR7EQ plug has the electrode much higher up inside the plug, thus it runs far "warmer" than a BUR9EQ.

"BUR7EQP"

NGK BUR7EQP

"BUR8EQP"

NGK BUR8EQP

A "colder" plug is not able clean itself as well as the carbon build up conducts the high voltage, and the spark will jump down the insulator instead of the electrode - causing little or no ignition of the fuel under compression where the resistance\'s are much greater.

Note how much further up inside the spark plug the insulator is. This makes it run cooler than the "7" due to it being further up the inside of the plug protecting it from the heat.

Q. What do the Trailing spark plugs do?

A. These are to ignite any extra fuel that was not burnt from the Leading plug, on the Le Mans winning 26B 4rotor there were 3 plugs per chamber - this also reduces fuel consumption, and emissions.

Q. Why are there "colder" plugs in the Trailing holes?

A. The reason the trailing hole needs a colder plug is because the Leading has already ignited the fuel therefore the trailing is much hotter in the combustion chamber.

Q. How often should I replace the plugs?

A. This really depends on the way you drive your car. Generally speaking the rotary can be a heavy user of spark plugs, we would recommend changing them every 6,000miles at most.

Q. Why run a colder plug for racing?UPDATE TO THIS QUESTION 28/10/2003 - I had kind of covered this by the following answer here, but I thought I had better add in some information about high speed running.  For high speed running even with 9\'s in the trailing and leading the conditions will be too extreme for the plugs and engine.  If you are doing high speed running quite often then it is recommend you run really cold plugs - even up to 11.5\'s, in all four holes.  But these of course can cause problems if you also do a lot of city driving as the cold plugs can foul (also see section below).  You can also run 9\'s or 10\'s in the leading and 10\'s or 11\'s in the trailing (consecutively).

A. When you are racing the engine all the time, the engine itself is hotter - therefore it will be cleaning itself already.

You can certainly use 9\'s in all four holes is if you are doing 1/4 mile runs with a modified engine or racing round the track, in both cases the engine will be running far hotter than just normal road/motorway driving. Yes most people run 9\'s and yes they will say they don\'t have any problems but it doesn\'t mean it is correct does it? :) It will work and the car will boost fine as the plugs won\'t really make much difference to the actual boost unless they are badly misfiring.

Ultimately you should start-up an engine on warmer plugs if it is stone cold, then when warm put the colder plugs in. You will often see people doing this at a racetrack at the very beginning of the day.

Q. What is the best way to clean Spark Plugs?:

A. Use Carburettor cleaner - do not use a "Sand blast" type cleaner as sand will lodge itself in the plug.

Q. Problems with flooding?

A. Using the NGK BUR7EQP/BUR7EQ or BUR6EQP/BUR6EQ in the Leading spark plug holes is \'VERY\' likely to cure any flooding problems. Please note however, if your engine is low on compression you will still have starting problems - but running the warmer plug should still help.

Q. Are spark plugs country specific?

Yes - they can be, as colder and warmer climates effect the starting of the engine. However from reading the Mazda Factory Manual\'s for Australia, and the USA, and going on what a new FD RX-7 comes installed with from Japan (7\'s in the leading and 9\'s in the trailing) there is no difference to what is shown in the Table above.

Checking to see how your plugs are:

You can check to see how your plugs are by removing their plugs after a gentle drive round the block to see if the insulator is black with carbon or clean white. I\'m sure you will find the 9\'s really quite black and dirty, and ready to start to fouling up or even non start (Flood!).

Q. What does a fouled Spark Plug look like?

A. This:

"Old

Pictured above is a fouled BUR9EQ from an (incorrect) Leading hole. Note: the "black" ( normally "white" ) insulator within the electrode. To check if a plug is fouled - this is the part you need to be looking at, not the outer (metal) part of the plug.

From the US and Australian "Factory Workshop Manuals":

"From

From the UK "Factory Workshop Manual":

Below is a picture from the 1992 Mazda Factory Manual, the diagram on the left-hand side clearly indicates to use a BUR9EQP in the Trailing, and a BUR7EQP in the Leading. However on the right-hand side (in the table), it shows to use BUR9EQP in the Leading and BUR8EQP in the Trailing. We are 100% confident that this is incorrect as it is telling you to run a Warmer Plug in the Trailing - WRONG WRONG WRONG! (Must have been a misprint my Mazda - bit scary!)

"From

In closing

Mazda and NGK have spent many many years developing Spark Plugs for the Rotary, and for day to day (non-racing) use - it certainly makes sense to go with what they recommend. Afterall - look what it reads on the box, and the plug itself (T=Trailing, L=Leading)!:

"Read

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Offline Fish

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #1 on: December 20, 2002, 05:46:15 PM »
Glenn, great information. My UK owner\'s manual say\'s that 8\'s and 9\'s should be used!

I have 9\'s all around at the moment, and a change is coming up soon. I will try 8\'s leading and 9\'s or 10\'s trailing. I dont drag the car, but I do drive it hard, and it does see the odd trackday.

Dan

Offline Glenn Butcher

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #2 on: December 20, 2002, 05:54:09 PM »
Hi Dan!

Yeah - very conflicting how Mazda UK put what they did in the Factory Workshop Manual of all places!

8\'s in "L" and 10\'s in "T" would be good for Track Day usage, and Drag Racing.  As long as you don\'t putt around with it, I\'m sure you won\'t ;)
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Offline 20B_boy

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #3 on: December 21, 2002, 10:31:47 AM »
Hi mate!

I\'m running some HKS racing plugs in my 1bar FD daily driver (dont know numbers of em atm) and have had a few probs with flooding now its gotten cold (largely I believe because of the RE-A ECU which runs really rich). In fact she\'s sat outside flooded at the mo. It was compression tested by Geff a couple of months ago after it flooded the first time and the results were all roughly +/- 90psi which sounds ok for a 42K mile 13B which is abused every day....

Any way, I have some NGK plugs, the box says \'Racing\' on them but they are BUR7EQ and BUR9EQ\'s. My question is, are these plugs ok to run fairly hard at 1bar on a daily basis or should I may be run some thing colder? My setup is a kin to Ant\'s.

It only needs to \'fix\' it for a month or two because things will be being replaced after that as you\'re aware :-)

Cheers bud,
Rich
R.

Offline Glenn Butcher

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #4 on: December 22, 2002, 08:13:34 PM »
G\'Day Rich!

How\'s it going?

Your car should be the classic example of one where you could try the 7\'s and 9\'s and see if she floods - I\'m sure the warmer plugs in the leading would stop it flooding.

Engine sounds good, but maybe the plugs are too cold for it?  If it is used as a daily driver I would put some warmer plugs in.

I think you should be ok with the 7\'s and 9\'s (@ 1bar) - the reason it will be flooding is generally because the Leading plugs are too cold.  Put them in and see how it goes, if you are going on a track day or Santa Pod (unlikely - for your engine change) put your colder plugs in.

Over the next month or so, you could go with some 8\'s in the leading and 10\'s in the trailing? but if it is only for a short time - may not be worth it.

Best way to really check the plugs would be to take it for a run then check the colour of the plugs afterwards, experimenting with the different temp. ranges.  It is difficult on a street car that is modified - you really need to find the happy medium.
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Offline 20B_boy

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #5 on: December 22, 2002, 09:05:25 PM »
Cheers mate. I\'ve now got 7\'s and 9\'s. Havent been able to test her though as despite removing all plugs, \'flushing\' her and following the \'deflood\' program she started kind of well and then died again. And hasnt started again since :(

Didnt have the time or inclination (cold, wet, dark and I was really pissed off :mad: !) to remove plugs again (first time I\'ve had all the plugs out - took a while to work out where I could get a spanner on each of them I can tell you!) so she\'s still sat sleeping on the drive way at the mo :(

I\'ll let you know how things go *when* I get her going again....

While I\'m typing, do you need to take all 4 plugs out to deflood? Can I do just the leading plugs? or even just the \'trailers\' as I can actually see those from the top of the engine! I guess as she must be badly flooded that the leading ones REALLY need to be done at the least. Do you agree with the injection of ATF down the plug holes by the way? Only Geff popped around last time it happend, whipped a couple of plugs out, cranked her for a bit, stuck em back in and hey presto i.e. no putting oil down the holes. Help or hindrense do you think??

Cheers mate,
Rich
R.

Offline Glenn Butcher

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #6 on: December 23, 2002, 10:43:26 AM »
Hi mate,

I personally think that engine oil in the plug holes would work very well.

Definitely will help putting a smear of oil in a flooded engine, the petrol tends to clean it out completely.  The idea of putting the oil in the engine is to create a better seal between the Apex Seal and the Rotor Housing.

Take all 4 plugs out (mainly to clean and dry them), do the flushing, put some oil in (not too much), then turn the engine over by hand (using the alternator belt) this will smear the oil through the engine - bringing your compression back.

Put the plugs back in (make sure they are completely clean and dry).

Then try and start - hopefully she will.

Let us know.
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Offline Fish

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #7 on: December 23, 2002, 05:54:04 PM »
When I had this problem, Gary T. came over with his van and helped me out, by showing me all the tricks in the book for de-flooding, then when the battery was starting to drain in came the van. Jump start helped turn mine over a treat. My poor little battery didnt have the energy to turn it over. They take quite a bit ot juice to do it.

Dan

Offline 20B_boy

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #8 on: December 23, 2002, 06:13:00 PM »
I\'m able to turn the old girl over sufficiently with the assitance of a recharged battery, the old mans \'Scort and a car starter power pack thingy. But she\'s just flooded/ing too badly. Knowing how rich the ECU runs I\'m not surprised, and as I was running 11\'s all \'round which probably didnt help.....

Hopefully reverting back to 7 and 9\'s will alleviate further problems to some degree *when* I get the bitch going again! Some thing to do over xmas at least!

Cheers,
Take care over Christmas every one!

Rich
R.

mmilner

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #9 on: December 27, 2002, 06:45:44 PM »
Hi all. I\'ve been following this thread with interest. I\'ve currently got a 1989 EGI RX7. (gen 2, I believe.) I\'ve had it for about  3 years now and although my Haynes Manual says use BUR7EQ/BUR9EQ, my local Mazda garage who I get all my parts from insists that the BR10ET is the correct plug. (For both leading and trailing.) I\'ve had no problems at all with that arrangement either, which is strange. Any comments?

As far as flooding goes...well, suffice it to say I had a lot of experience of that in my first (1981) Gen 1 RX7. It usually happened due to some other root cause. (Eg: drained battery, deteriorated HT leads, etc.) But then I had the same problems as mentioned here.

I must admit that I never tried squirting oil in, as the compression seemed to be pretty good. (Ie: turning the engine over with the plugs out produced loads of noise and big squirts of petrol vapour at every compression stroke.) However, one sure fire way I found of getting it started involved using a fan heater pointed at the sump for a few hours. (Best in a garage to retain the heat.) Eventually the block would warm up to the extent that the excess petrol would start to evaporate off and after a few goes, hey presto, a started engine.

Hope this might help a few people!

Cheers,
Martin.

Offline Glenn Butcher

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Plug Guide for the "non-turbo" 2nd gen. RX-7
« Reply #10 on: December 28, 2002, 10:16:02 AM »
Hi Martin!  thanks for the info.  got some here on your car also:

I happen to have a hardcopy book here on your model car - and it definitely runs BR10ET plugs in Leading and Trailing.  This is for the non-turbo version - EGI (a.k.a. the Series 4 or 2nd Gen. non-turbo RX-7).

Plug guide here for your car:

Recommended Spark Plugs (1989 non-turbo RX-7
NGK

SR10A, SD11A (For Australia)

BR9ET, BR10ET (Except Australia)

NIPPON DENSO

S-29A, S-31A (For Australia)

W27EBR, W29EBR (Except Australia)



The Turbo version of your car runs the 7\'s in the leading an 9\'s in the trailing. Check out www.iluvmyrx7.com Actual PDF Link here - Page. A7.
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Offline 20B_boy

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #11 on: December 28, 2002, 01:04:34 PM »
Success. Finally had time to give the deflood another go yesterday :-)

First time the other day taking plugs out took about 3 hours what with trying about 10 different plug wrenchs and levers and access methods! Yesterday took about 5 minutes out and 5 minutes back in. Easy peazy when you know how and have the \'right\' tool for the job. My new best friend in the toolbox is a slim 3/8 drive ratchet with a short 1/2 drive adaptor and a Halfords spark plug socket on the end ;-)

Any way, plugs, egi and fuel pump pulled; turn over engine as many times as you can bare to using some ones car to  give you a bit extra battery oomph. Have a rest and a cup of tea while drying the plugs well. I used the gas hob to dry/warm them up and then put them back in when the were still nice and \'hot\'. Egi and relay back in. Foot to floor, cross fingers and turn key. Started after about 5-10 seconds. Tried to idle on and off, with some single rotor action intermittently as it tried to sort it self out. Walked away (fingers still crossed) and she stalled after about 20 seconds. Started swearing *a lot*, restarted her though and proceeded to successfully rev the bollocks off her - dont try this to begin with though as it may well flood again.

10 minutes later took her out for a blat and all was fine. Trauma over, quite satisfying as it happens!

Now to see if the 7\'s and 9\'s stop further flooding. I\'ll pull them in a week and see what they look like. The 11\'s that came out were pretty sooty.

Thanks all!

Rich
R.

mmilner

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Re: Plug Guide for the "non-turbo" 2nd gen. RX-7
« Reply #12 on: December 28, 2002, 08:35:42 PM »
Quote

I happen to have a hardcopy book here on your model car - and it definitely runs BR10ET plugs in Leading and Trailing.  This is for the non-turbo version - EGI (a.k.a. the Series 4 or 2nd Gen. non-turbo RX-7).

The Turbo version of your car runs the 7\'s in the leading an 9\'s in the trailing. Check out www.iluvmyrx7.com


Thanks for that Glenn.  Good to know I\'m using the right ones...http://www.iluvmyrx7.com is a good site, (just had a look around), however it\'s weird that the Haynes manual and even the one on the above web site specify the other plugs. (They don\'t seem to differentiate between the turbo and non-turbo models on that score at least:-/)

mmilner

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #13 on: December 28, 2002, 08:58:10 PM »
Quote
Originally posted by 2b_bad_20b
Success. Finally had time to give the deflood another go yesterday :-)


Excellent news! My old gen1 engine used to take a while to get going properly, presumably building up compression. I used to take the wet plugs out and rest them on the body and they wouldn\'t spark when the engine was turned over whereas a dry plug would spark straight away. Like you I dried them on a gas stove and they\'d spark again once dry.

The wet plugs dripped \'black petrol\' which at the time I thought was oil contamination, but in hindsight was probably dissolved carbon deposits. The oil injection might well help in these cases.

Anyway, another tip if anyone tries the \'heating\' route to deflooding...put a nice thick blanket on top of the engine and close the bonnet. You\'d be surprised at how much this speeds up the process. (Just remove the fan heater before cranking the engine as petrol and fan heaters don\'t mix. Obvious, I know!)


Cheers,
Martin.

Robertio

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*** Spark Plug Q\'s & A\'s for the FD RX-7 ***
« Reply #14 on: July 08, 2003, 10:42:31 PM »
As it turns out 7s are not available in the UK, does anyone have a way of getting them?