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bosch or autolite?

11K views 11 replies 10 participants last post by  ND40oz 
#1 ·
hello all...
just curious, i currently have bosch plat. 4 plugs in my 2000 D. i think this is causing me to lose about 2mpg in efficiency :bawl: because its such a hot spark. and burning alot of fuel from take off, doesnt help my wife has an extremely heavy foot :drivingz: . and its not because she is fat, she's accually quite shapely :D
i was going to try a set of the autolite 3923 plugs just because everyone here seems to like them. i get to the auto parts store, and look up the autolite plug for my vehicle, and it told me the plug for me is the autolite 5224, so... there i sat scratchin my head :huh: for a few minutes wondering what do i do now? someone tell me what is the difference between the 3923, and the 5224? because i obviously dont know.
 
#2 ·
While the factory and factory replacement spark plugs work, the Magnum engines have shown slightly better performance with the Autolite 3923 Spark Plugs. The Autolite 3923's are a standard tip spark plug that is one heat range colder than stock, as compared to the extended "Special Power Tip" plugs that the engine came with. Why the difference? A standard tip plug is less susceptible to detonation, is a good replacement for modified Magnum engines, and work very well with modified engines as well...especially when using Nitrous or a Supercharger. In some cases, the Autolite 3923's also showed a 4-5HP difference at the rear wheels on the Dyno. (The test was performed with new OEM Spark plugs vs. the Autolite 3923's. No changes to the engine and the plugs were tested on the same day under the same conditions.)


from intense-dakota.com
 
#3 ·
I am running the standard 3923's in my D and they are working very well. I think there is a platinum version that also runs cooler, but someone else will have to chime in and maybe leave a part #?

Good luck.
 
#4 ·
I run the platinum 3923's. They're simply the P3923 plugs. There was definitely a slight performance gain over stock.

As for going to any auto store, if you tell them you want the colder heat range plugs, they'll just give you a blank stare and not know what you're talking about. The 5224's are what is listed at all of them. I don't know who originally thought of the 3923's, but thank you to whoever it was. :)
 
#5 ·
I just installed platinum 3923's in my s/c'd 318 and I noticed a nice mid range increase in power. I also run an aftermarket ignition and coil with taylor spiro pro wires. It really does make a difference from oem.
 
#6 ·
On a 1995 Magnum 5.9V8 I found very slightly less MPG in 4 test using the Bosch+4 plugs - but it was not as much as 2 mpg - more like half a mpg.

Don't expect much mpg increase with any sparkplug change.

Here's another update to the Sparkplug FAQ 11-7-2002.

For those looking for colder heat range sparkplugs,
note the Stealth Turbo V6,
and 1990 Jeep I6 tips near the end of this FAQ.
==========

What sparkplugs will fit a Magnum engine in a 1994+ Ram or Dakota pickup? '
Here are some sparkplugs that will fit with brief comments.

Where a resistor value is given, it was measured by the author from terminal
top to center electrode tip using a Fluke 87 multimeter.

RAM 4.7/5.2/5.9 V8 Magnum PLUGS
=======================

Champion RC12YC is the 1993-1998 factory installed plug. (resistor inside
measures 75,000 ohms)

Champion RC11YC is one heat range cooler and is part number 3344.

Champion RC9YC is an even colder heat range available.

The Champion RC9YC4 sparkplug has been reported by Ram owners as being helpful
in reducing pinging.

Champion RC12LC4 is a longer projected nose plug installed at the factory on
V8 Rams since approximately 1998. The plug change was probably for emissions
purposes.

Champion RC12LYC is a longer 'projected nose' plug previously recommended for
the Viper alum. V10 and Chrysler 3.2/3.5L V6's.

The '95 stock factory sparkplug for the iron block Dodge V10 engine was a
Champion Copper Plus RC9MC4.

The 1995-1999 iron block Ram V10 is a QC9MC4, where the Q instead of the R
means the resistor inside is a "wire wound" instead of the SAC semiconductor
that Champion primarily uses to surpress radio interference.
An email to Champion in 1998 got a reply that the '9' in the above numbers
does mean that these plugs are 3 heat ranges cooler than the '12' heat range
plugs like the RC12YC used in the V8's.

Why the truck V10 uses a 3 heat range cooler sparkplug is not known, but
perhaps since the heavy trucks don't have to meet as stringent pollutions
standards, this is a more ideal sparkplug for performance instead of
emissions.

Champion RC12MCC4 are stock in the 4.7 Magnum V8.

Champion RC10PYP4 is a projected tip, double platinum plug that is standard
equipment in some of the Chrysler 2.5L V6's that have 3 almost impossible to
reach plugs in the rear. Being two heat ranges cooler with double platinum
tips for long life it might be an interesting replacement for the Magnum V8's.

Champion Truck Plugs P/N 4071
Many Ram owners have reported they were pleased with a change to this plug.
The main differences between the Truck Plug 4071 and the stock RC12YC seems to
be that the new center electrode metal rod is longer, and the insulator is
black color instead of white. (Resistor inside 85,000 ohms) It is possible
that the extra 10,000 ohms of resistance retards spark firing a little bit,
and may account for why some report that this plug reduced pinging on their
Ram.

http://www.federalmogul.com/products_main/am_underhood/ignition_spark_plu gs.htm

another better descriptive Champion sparkplug website at:

http://www.edelbrock.com/automotive/sparkplugs.html

If unavailable locally, Champion sparkplugs can be mail ordered from
http://www.edelbrock.com

Kenne Bell company says they did extensive research and testing on their
in-house DynoJet 148C, and recommend the "V" design NGK ZFR5F11 (stock number
2262, resistor inside 4,000 ohms) for non-supercharged,
and ZFR6F11 (one heat range cooler) for blown 5.2/5.9 Dodges.

These V design NGK sparkplugs have a v-notch cut into the center electrode
that increases the sharp edges and moves the spark away from the center. Sharp
edges reduce the voltage need for the spark to start. The nose of these plugs
seem to be slightly more projected than the Champion RC12YC. The ZFR5F11 is
also NGK's recommended Viper Aluminum V-10 plug.

One Ram owner reported on ********* that he purchased 12 of the ZFR5F11 plugs
and "indexed" the 8 that 'by chance' stopped in the threaded hole with the
ground electrode post toward the fender side of the truck. This puts the open
gap toward the valves and is done that way in hope that it would aid
combustion speed.

Increased combustion speed is generally a good thing, but if
the engine is already pinging this may increase detonation tendency.

If you put a piece of white tape around your sparkplug socket and make a black
mark on the tape, it is easy to insert the plug so that the ground electrode
post is lined up with the mark. this way you can see where the ground post
ends up.

These ZFR5F11 plugs were reported to noticeably pep up the 5.9 V8 engine
compared to the 30,000 mile old Champion plugs.

See this webpage for an article on indexing with good pictures:
http://www.fordmuscle.com/archives/2000/07/indexplugs/index.shtml

NGK's standard recommended sparkplug for the 3.9/5.2/5.9 Magnum engines is the
FR4 (stock number 5155) or FR5-1, (stock number 7252).

http://www.ngksparkplugs.com/products/cars_trucks_suvs/

NGK platinum plugs (part#ZFR5FGP, stock#7098) have also been reported to work
well in a 2001 5.2V8.

NGK also makes an Iridium plug. If your running the ZFR5F-11 (4593) the
Iridium plug would be the NGK ZFR5FIX-11 (2477). Here is a website that has a
cross reference for plugs.

http://www.clubplug.net/retail_iridium_ngk.html


NGK has a very good set of pictures for reading the ends of used sparkplugs
at:

http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqread2.asp

Some of the most expensive sparkplugs available ( $10-13) are the Denso
'Iridium' with their tiny center electrodes made of a very high melting point
iridium alloy. For the 5.2/5.9 V8 Magnums Denso recommends their IK16. for
the V10 Denso recommends their one heat range colder IK20. Despite the high
cost, Kenne Bell company recently used 16 of these Denso Iridium plugs in
their Supercharged Hemi 5.7 show vehicle.

http://www.densoiridium.com/default.asp

Mopar Performance now recommends {and sells} Bosch conventional metal tip
sparkplugs in their 2000 year catalog for mopar engines, and gives a table of
interchanges on page 125.

The Mopar Performance plug (Mopar Perf p/n P4876926) from the catalog for
Magnum 5.2 or 5.9 V8 engines {also A engine and Hemi} is a repackaged Bosch
FR8DCX, Bosch part number 7557. (Resistor 5,600 ohms)

Note the 'C' in the DCX that indicates a copper core center electrode tip
rather than the 'P' that indicates platinum. Mopar Perf lists the 'retail'
price of this plug as $12.50 for a pack of 4. Parts Plus auto stores sell one
Bosch p/n 7557 for $2.02 plus tax. Some Napa stores have the 7557 at $1.22.
Several Ram owners report good performance from switching to this plug.

Bosch also makes a sparkplug with a longer projected nose similar to the
Champion RC12LC4 that is Bosch part number 7562 with descriptive number
FR8LCX. There is also a FR8DC (part number 7527) that comes with a smaller
pre-set gap.

If you need a colder heat range plug, the Bosch FR6DCX (part number 7553,
Resistor 5,500 ohm) is also widely available.

Bosch Platinums {old style, not +4's}
FR8DPX, (part number 4102, Resistor 4,700 ohms, gap .043)

Bosch Platinum FR7DPX p/n 4202 is a similar but colder heat range plug.
(Resistor 6,600 ohms) These are 'fine wire' sparkplugs with surprisingly tiny
tips that seem to give quick cold starts and good mpg on Interstate driving.
Increased gaps up to 0.050 from the Bosch factory setting of 0.043 seem to
work ok.

http://www.boschusa.com/Consumer/Automotive/SparkPlugs/

Bosch Platinum Super+4, P/N 4418 (Resistor 3.6 kohms)
This 4 ground electrode plug with a platinum "fine wire" center is presently
being heavily advertised, but is not recommended by Bosch for:
(1) truck,
(2) heavy towing, or
(3) "high performance/racing" applications.
The +4 plug is said to be designed for reduced number of misfires, low
emissions, and is said to be durable enough to last for 100,000 miles.
There is a brief article on this sparkplug design at:

http://www.babcox.com/tr/tr119832.htm

NGK also makes multi-ground sparkplugs and calls them the 'Multi Power'
design. Here's how NGK describes their good/bad attributes:

"NGK Multi Power Spark Plugs
NGK Multi Power Spark Plugs feature multiple ground electrodes for
extra-long life in a variety of applications. Spark plugs wear out when the
sharp edges of the ground electrode round off. Therefore, multiple ground
electrodes provide additional surfaces for the spark to travel to, extending
the plug's effective life. Multi Power Plugs are not for all applications, as
they can tend to quench the spark, or hamper the ability of the flame to grow
from the initial ignition point. However, the multiple ground electrode
configuration can help alleviate a number of problems, including hard
starting, excessive fouling or misfiring. They are also effective for vehicles
with very high ignition system voltages and/or combustion chamber
temperatures. Remember that Multi Power Spark Plugs, or any other multiple
electrode type spark plug, cannot provide more than one spark at a time. The
primary purpose of the multiple electrode spark plug is to achieve greater
spark plug durability and reliability over the life of the spark plug."

In a 1995 5.9V8 Magnum the Bosch+4 seems to give quick cold starts, and the
smoothest idle of any plug tested - but this plug seems to be prone to
increased pinging, perhaps because its large gap (0.065 inches) and long
projected nose may be equivalent to a slight ignition advance. This is not the
plug to try if you have a Mopar Perf computer already installed or insist on
using 87 octane all the time.

Bosch advertises increased MPG with this plug, but Consumer Reports found no
mpg difference when compared to factory NGK sparkplugs on a Honda. 1995 Ram
5.9V8 owner on four 300+ mile test runs over same stretches of Interstate 95
from NC to FL found 2% worse mpg with Bosch Super+4 plugs going northbound
compared to going southbound with Bosch FR7DPX gapped at 0.050 inches. It is
possible this was due to the direction of prevailing winds.

There is also a version of the +4, part number 4478 with the larger hex size
of older sparkplugs. The heat range of this plug is not known.

http://www.boschusa.com/index.asp?div=2&sud=1&grp=1&sgp=1

For the 4.7 V8 Magnum,
Bosch recommends the part number 4230 regular single electrode Platinum or the
copper tipped Bosch Super Cu part number 7562

The Bosch F6DP spark plug
(part number 4227, resistance from tip to electrode 1,400 ohms) has been
recommended by engine guru Larry Widmer as a good plug for supercharged
applications.
In a 1995 5.9V8 these F6DP plugs seem to work as well as the FR8DPX if
the gap is increased from 0.025 to 0.043 inches.

The missing 'R' after the F indicates this is one of the few Bosch platinum
plugs that does not contain a resistor for radio interference surpression,
even though when measured with an ohmeter a F6DP still read a resistance from
top terminal to electrode of 1,400 ohms versus the 5,500 ohms of a FR6DCX.

The pre-set factory gap of a F6DP is a small 0.025 inches, which is
advantageous to reduce misfires when cylinder pressures are very high. The 6
in the F6DP indicates this plug is two heat ranges cooler than the FR8DPX that
Bosch literature says cross-references to the Champion RC12YC that comes from
the factory in Magnum engines.

Bosch Tech support: 800-521-5462
-------------------------------------------
Autolite Double Platinum Pro APP3924
(APP3923 is a colder heat range platinum plug)
The two P's indicate two platinum nibs on the electrodes where the spark
jumps.

Autolite 3924 or cooler 3923
Many Dakota owners who drag race their trucks recommend this relatively
inexpensive plug, and some claim to have chassis dyno results showing 4-5 hp
improvements. Many use this plug with the MP computer and a 180 degree
thermostat. See dyno graph at this site:

http://www.fast4x4.net/dyno.htm

Autolite 5224 conventional metal tip (Resistor 5,400 ohms)
Autolite 5223 is a colder heat range plug
The 522? series is similar to the 392?, but has an extended tip that puts the
spark farther down in the chamber, which has an effect similar to slightly
advancing the ignition timing.

http://www.autolite.com/products.html

Autolite is advertising a new plug called the 'Titanium' that has two platinum
nibs but no titanium parts.

---------------------------------
AC Delco Rapid Fires, P/N 5 (Resistor 3,700 ohms)
Some Ram owners report the Rapid Fire plugs give a smoother than stock idle,
and the p/n 5 is supposed to be a 'one-size-fits-all' relatively cool heat
range that is also the same plug recommended for the Dodge Stealth turbo V6
3Liter DOHC. In a manner similar to the NGK V design, the old style AC Delco
Rapid Fire P/N 5 had 'gear teeth' cut into the center electrode to create more
sharp edges for the spark to jump from, but this plug was recently designed
and looks more like a conventional plug now.

GM did hire an independent firm to test these sparkplugs in fleet use, and
some mpg gains and idle smoothness improvements were reported to be found.

http://www.acdelco.com/parts/1380b.htm

The standard ACDelco sparkplug for the 5.2/5.9 Magnums is the FR3LS
Here is a webpage on how to decode ACDelco sparkplug numbers:
http://www.acdelco.com/parts/sp_ident.htm
--------------------------
Motorcraft
The standard copper Motorcraft sparkplug for the Magnum V8 is a AGSP32C. A
longer projected nose plugs is the AGSP32CF4.

Motorcraft also offers a double platinum tipped AGSP32PP.
-------------------------

In the Splitfire Catalog it specifies that a 5.9 Magnum V-8 uses different
plugs for different years:

A '95 360 uses plug "SF392D" with a .035 gap
A '99 360 uses plug "SF522D" with a .040 gap
------------
Torque Master, P/N VFN8BR ($12.50 per plug)
--------------

Unusual Czech-designed surface gap sparkplugs from the Brisk company:

http://www.brisk.cz/uk/default.htm

The DOR17LGS is the plug model recommended by Brisk for the 5.2V8 in the Jeep
Grand Cherokee.
-------------------------------------------------

Switching to larger hex (old style) sparkplugs from the 'peanut' plugs used on
the 1992+ Magnum engines:

If the heat shields around Magnum engine sparkplug holes are removed by gently
squeezing them with channel lock pliers, Champion 'N' series sparkplugs with
the 5/8 hex nut flats can be fitted to 3.9V6/5.2V8/5.9V8 Magnum engines, but a

special sparkplug socket must be ground down on a grinder to a small enough
diameter to fully tighten the sparkplug - otherwise an unmodified sparkplug
socket will hit the hole designed to retain the now removed heat shield. A
cheap stamped metal 'lawn mower' sparkplugs socket works well for this. Some
prefer to use N series Champion sparkplugs because a wide variety of heat
ranges are available, and many old time drag racers have built up a body of
knowledge about these plugs.
-------------------------------------------------

The Dodge Stealth 3.0L V6 DOHC Turbo "trick" to find a colder heat range
sparkplug for your Ram pickup when dealing with non-knowledgeable parts
counter attendants.

If you want a colder heat range sparkplug, because you aggressively drive your
truck and keep the throttle more wide open than most, you can find a colder
range sparkplug by asking for one for a 1995 Dodge Stealth 3.0L V6 Double
Overhead Cam Turbocharged engine. Sparkplugs recommended by any sparkplug
manufacturer for this application are 1-2 heat ranges cooler than the factory
Ram sparkplugs, but these 'Stealth' plugs are the same physical size.

I picked up a Haynes Manual for 1984-1999 Jeep Cherokees and found
that 1990 Inline 6 cylinder 4.0 liter engines used a Champion RC9YC sparkplug.
This is three Champion heat ranges cooler than the '12' heat range sparkplugs
used in the Rams. This kinda adds to the evidence that a '9' heat range
sparkplug may be the 'optimum' performance plug for the Magnum engines. Both
the the pre-1990 4.0 I6 and the {less emissions} strict 8.0L Ram V10 use '9'
heat range sparkplugs.

I think the '12' heat range Champion plugs used in the Rams are there for
emissions purposes. A higher heat range sparkplug burns off carbon deposits
quicker during a 'cold' start and generates slightly less emissions during an
EPA test because there is slightly less sparkplug misfire during this cold
warm-up period.

Warning: colder heat range sparkplugs foul easily, quit sparking, create more
pollution, and give lower mpg when the engine is not driven at wider throttle
openings frequently to burn away carbon deposits. This can also cause hard
cold starting and a miss at idle. Prolonged running of an engine with fouled
sparkplugs can overheat and ruin a catalytic converter that is getting
unburned gasoline & air dumped into it.

Spark Gaps:
A typical spark gap of the past was about 0.025 to 0.035 inches. Larger spark
gaps help idle quality, decrease total burning time like an ignition advance,
and may improve miles per gallon slightly.
However, larger spark gaps are harder to get to spark. On most engines too
large a spark gap usually shows up as problems at rpms over 3500 rpm, where
there may be a miss and vibration, or alternately a
miss-ping-miss-ping-miss-ping. At high rpms the vibration you might expect to
feel from a miss can be masked by the short times between firings.
How can a miss cause a ping? Usually a cylinder's fill after a stroke is
about 80% fresh mixture and 20% left over exhaust gas. When a miss occurs the
next stroke results in a cylinder fill that is about 100% fresh air and fuel.
Sometimes this extra fill results in such a faster and forcefull burning that
a ping occurs.
When is doubt, use a sparkgap of 0.030. Then slowly increase the gap
until problems are detected. The more powerful you make your engine with mods,
the less sparkgap you should set, because high cylinder pressures at high rpms
need less spark gap. If your engine is pinging it is usually worth while to
set the gap at 0.030 inches and see if that changes anything. the small gap
decreases the chance of missfire and also acts like a slight ignition retard.
For the Magnums, recommended spark gaps have ranged from 0.035 on
1994-1996 Magnums with Champion RC12YC to 0.040 on the RC12LC4 to 0.065 inches
on the Bosch Platinum Super+4 pn 4418.

Ignition wires:

Magnecor ignition wires are of very good quality:

http://www.magnecor.com/magnecor1/Index.htm

In addition to the regular style Magnecor, the "CN125" wires are very good at
surpressing radio noise for Ham, scanner or CB. The FAQ section at Magnecor is
'no bull' and worth a read. These wires retail around $110 but
can be found for less.

Magnecor admits in their write-ups that NGK ignition wires are of good
quality:

http://www.ngksparkplugs.com/techinfo/wire_sets/

MSD makes wires whose internal construction is perhaps a slight step down due
to their falling into the
"Low DC resistance impresses Uninformed Customers"
advertising wars.

In ignition wires, it is the 'impedance,' not solely the ohms of resistance,
that determines voltage drop and current.

MSD#32189 is the 94-97 Ram 5.2/5.9L V8 Wire set. MSD 8.5 mm wires on a 1998
5.2/5.9 L are part number 32979, and cost at Summit is about $80 with postage.

Champion has a line of 'Truck Wires' they came out with last year that look
pretty good and have a heat resistant ceramic boot at the plug end. For the
5.2/5.9 Dodge Magnum, the Champion TruckWire part number is CHA69417 and is
available thru Napa stores.

Interested in a slight advance retard of your ignition timing?
Search the website below for a modification for the crank trigger of
3.9/5.2/5.9 Magnum engines:

http://www.krcperformance.com

Advancing the timing may require a switch from 87 octane to 89 octane
gasoline. Retarding the timing might be just the 'little bit' needed to get
rid of pinging.

There is a write up of changing sparkplugs with pictures on a Magnum V8 at:
http://www.k-huhn.com/dodgeram/sparkplugs/
 
#7 ·
coachholland said:
I run the platinum 3923's. They're simply the P3923 plugs. There was definitely a slight performance gain over stock.

As for going to any auto store, if you tell them you want the colder heat range plugs, they'll just give you a blank stare and not know what you're talking about. The 5224's are what is listed at all of them. I don't know who originally thought of the 3923's, but thank you to whoever it was. :)
Pyssed,

What SuperCharger are you running? What ignition upgrades do you have? I have a Paxton Novi 2000 and am running regular 3923s and Accel 8.8mm wires. My only ignition upgrade is the MSD BTM that came with the Paxton kit. Do you think Platinum 3923s would make a difference for my set up?

Thanks

Mark
 
#9 ·
NGK plugs - well worth the additional cost over the cheap Autolites. I've had 3923s and they worked well, the NGKs worked better
 
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