Advice: Colder Plugs for FI application?
- Thread starter 88JeepXJ
- Start date
wolfpackjeeper
NAXJA Forum User
- Location
- 500' and 500KCAS, RAF lakenheath
cross reference the NGK number, I have been running 2 stages colder on those in my stroker. Same as the Champions, just knock a few numbers off the center digit and it goes colder.
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
NGK recommended me to run these in my stroker: ZFR6F-11
wolfpackjeeper
NAXJA Forum User
- Location
- 500' and 500KCAS, RAF lakenheath
that number sounds familiar, I am pretty sure that is what i am running as well. Great plugs
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
NGK recommends ZFR5N for 99-01, the FR5-1 for 91-98, and FR5 87-90. All are heat rating 5. The ZFR6F-11 are heat range 6. So, one step colder.
Some additional info:
ZFR5N: 19 mm reach, resistor, extended projected tip, gasket seat, ISO length, v-power, heat range 5, .035" gap
FR5-1: 19mm reach, resistor, extended projected tip, extended metal shell, v-power, heat range 5, .040" gap
FR5: 19mm reach, resistor, projected tip, gasket seat, v-power, heat range 5, .040" gap
ZFR6F-11: 19 mm reach, resistor, extended projected tip, gasket seat, ISO length, v-power, heat range 6, .044" gap
Some additional info:
ZFR5N: 19 mm reach, resistor, extended projected tip, gasket seat, ISO length, v-power, heat range 5, .035" gap
FR5-1: 19mm reach, resistor, extended projected tip, extended metal shell, v-power, heat range 5, .040" gap
FR5: 19mm reach, resistor, projected tip, gasket seat, v-power, heat range 5, .040" gap
ZFR6F-11: 19 mm reach, resistor, extended projected tip, gasket seat, ISO length, v-power, heat range 6, .044" gap
Its a heat range 5 and a 16mm reach.
Awesome information thank you. So I'll get the ZFR6F-11 but I'll probably have to close the gap to at least .035, maybe even .030 due to FI.
wolfpackjeeper
NAXJA Forum User
- Location
- 500' and 500KCAS, RAF lakenheath
Why would you close it? I figured you would want it bigger, and upgrade the coil to help combat detonation from a late or weak spark.
At least with NGK you get heat ranges. This works for Cherokee owners. I'm using the ZFR5N's in my 90, no problems even with the projected design.
However, asking for a plug hotter or colder at the parts counter is problem - first, the plug has to actually exist - plug makers don't tool up for non-existent applications, or make a plug that simply doesn't sell. Profit comes first. Second, the plug has to actually sell at that store to bother keeping it in stock.
Find the "hub" store that stocks parts to ship to others in it's district, and a counterman there who knows what you are asking for. Shop at a quiet time, because the last thing you want is to come in with a parts counter jammed with broke down homies trying to get to work tomorrow and who have no clue what they are doing.
If you pick the plug number from a list - which means it could exist - shop online for it at the hub store - which lets you see the possibly accurate shelf quantity, and then simply order them online for store pickup, it's all good.
At least with the Cherokee, it's rare for someone to build a 3/4 race motor and complain their plugs constantly foul on poker runs. Those guys are the bane of Saturday mornings in this town, their mechanical knowledge and patience are about equal. And the special application Harley plugs usually not in stock.
Work the system, it works for you. Just please don't come it expecting the world on our shelves, it's all about turns per quarter and profit, and thousands of new part numbers added every year.
However, asking for a plug hotter or colder at the parts counter is problem - first, the plug has to actually exist - plug makers don't tool up for non-existent applications, or make a plug that simply doesn't sell. Profit comes first. Second, the plug has to actually sell at that store to bother keeping it in stock.
Find the "hub" store that stocks parts to ship to others in it's district, and a counterman there who knows what you are asking for. Shop at a quiet time, because the last thing you want is to come in with a parts counter jammed with broke down homies trying to get to work tomorrow and who have no clue what they are doing.
If you pick the plug number from a list - which means it could exist - shop online for it at the hub store - which lets you see the possibly accurate shelf quantity, and then simply order them online for store pickup, it's all good.
At least with the Cherokee, it's rare for someone to build a 3/4 race motor and complain their plugs constantly foul on poker runs. Those guys are the bane of Saturday mornings in this town, their mechanical knowledge and patience are about equal. And the special application Harley plugs usually not in stock.
Work the system, it works for you. Just please don't come it expecting the world on our shelves, it's all about turns per quarter and profit, and thousands of new part numbers added every year.
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
With more compression you usually close the gap. However, if you have an upgraded coil you can run a larger gap. I read that to find the ideal gap for a particular setup you open the gap up just before it starts to misfire. Not sure about that though.
Hellbent
NAXJA Forum User
- Location
- san diego, california
the ngk plug numbering system works BACKWARDS in relation to most other plugs-a lower number is a "hotter" plug(just making sure, many people don't realize this). http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp
don't accidentally kill your motor with a hot plug in a turbo!
don't accidentally kill your motor with a hot plug in a turbo!
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
Another thing the heat ranges don't transfer between makes. I.e. heat range 9 on an NGK isn't the same as 9 on a Champion.
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
I was going back over some parts in my garage and in the past I was running the BKR6E-11 in one of the strokers. I remembered your post about the Miata plugs so I went and checked the info on the two plugs. It turns out that I misread the info and the plus is actually a 19mm reach, not 16 like I said. The miata plug has the same heat range as the stock Jeep plug though and it lacks the extended tip that is used in 91-01, but I don't know what difference that makes. Two images shows what I am talking about with the extended projected tip:
BKR6E-11:
and ZFR6F-11:
From what I was able to find the idea behind the extended projected tip is that it just pushes the spark further into the combustion chamber.
Boostwerks.com
NAXJA Forum User
- Location
- Colorado
Correct. The rule applies to both NA and FI. The increasing the gap has the same affect as advancing the timing.
The only other factor is, the larger the gap the shorter the plug's life.
From what I was able to find the idea behind the extended projected tip is that it just pushes the spark further into the combustion chamber.
==========================================
In the old days a rich carb needed a hot plug to keep from loading at idle and slow speeds. But this same plug may over heat at speed and fire the mix early. This same engine MAY load a colder plug at idle.
With a projected tip. A hotter tip will burn clean but with the tip deeper in the chamber the tip makes more/better contact with the intake mix. Keeping it from over heating. The projected tip plug acted like a plug of many heat steps or extender heat range plug.
A few people reported gaining a few HP when switching to a projected plug. This could be to improved flame travel with the tip deep in the chamber.
But with a MUCH better mix with FI and any head made in the last 20 years or so has reworked plug placement to point no HP is gained and often a projected tip is no long needed for cooling.
My beloved 4.0 head IS from the stone age.
==========================================
In the old days a rich carb needed a hot plug to keep from loading at idle and slow speeds. But this same plug may over heat at speed and fire the mix early. This same engine MAY load a colder plug at idle.
With a projected tip. A hotter tip will burn clean but with the tip deeper in the chamber the tip makes more/better contact with the intake mix. Keeping it from over heating. The projected tip plug acted like a plug of many heat steps or extender heat range plug.
A few people reported gaining a few HP when switching to a projected plug. This could be to improved flame travel with the tip deep in the chamber.
But with a MUCH better mix with FI and any head made in the last 20 years or so has reworked plug placement to point no HP is gained and often a projected tip is no long needed for cooling.
My beloved 4.0 head IS from the stone age.
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