Why do engines loose compression slowly?
07-23-10, 02:48 PM
#26
07-23-10, 10:46 PM
#30
"Can used housings potentially cause the loss of compression with such things as unnoticeable warpage? Is it just overly cautious or a determining variable?
Howard, did you use new housings in that 23k engine?"
most of what i personally run (including the 4 year build) and build is used as far as housings which now retail for over $700 each.
the good news is that good used housings are greatly underloved as far as being able to deliver most of the hp at significantly lower cost.
they need to be straight. they need to have not shrunk as to width, they need to have decent frictional surface.
you can help your housings maintain their shape by running 10 or colder plugs. hot plugs retain heat around the spark plug boss and eventually various things happen... all lethal
the plug boss distends and eventually cracks
the plug boss heat warps the apex seal in the longitudinal center
the retained heat from 9 or hotter plug eventually shrinkes the width of the housing at the plug area and below. a 2 thou shrinkage and the housing is toast. i just had to junk two nice looking housings because they were way past this.... all because of heat.
manage the heat, don't loose compression.
off to the woods for a couple of days.
howard
Howard, did you use new housings in that 23k engine?"
most of what i personally run (including the 4 year build) and build is used as far as housings which now retail for over $700 each.
the good news is that good used housings are greatly underloved as far as being able to deliver most of the hp at significantly lower cost.
they need to be straight. they need to have not shrunk as to width, they need to have decent frictional surface.
you can help your housings maintain their shape by running 10 or colder plugs. hot plugs retain heat around the spark plug boss and eventually various things happen... all lethal
the plug boss distends and eventually cracks
the plug boss heat warps the apex seal in the longitudinal center
the retained heat from 9 or hotter plug eventually shrinkes the width of the housing at the plug area and below. a 2 thou shrinkage and the housing is toast. i just had to junk two nice looking housings because they were way past this.... all because of heat.
manage the heat, don't loose compression.
off to the woods for a couple of days.
howard
Also, the "longitudinal warping" of the apex seal going over the plug boss is not the issue. It's the fact that the apex seal (more evident in the two piece variety) "seesaws" as it crosses over the swollen spark plug boss due to the uneven pressure being applied by the springs on the different parts of the apex seal. This causes the apex seal to become weak and fail.
-J
07-24-10, 12:17 PM
#33
Race plugs are at best a necessary evil. Some of them require a special socket and/or do not have the same length as the factory plugs. Many of them are expensive ($30+ per plug) and need to be ordered. They foul out more easily. You have to gap them. Some of them are non-resistor, which HKS warns against for those using a Twin Power. A lot of them hurt fuel economy and idle. There are so many drawbacks and the marginal benefit compared to running 4 of the factory platinum BUR9EQP plugs is just not there for most applications--even single turbo applications. You're not going to blow your car up just because you didn't use 10 heat range plugs. I haven't seen any controlled testing to show that 10 heat range plugs by themselves are going to reduce wear and cracking at the spark plug hole compared to the OEM 9 heat range plugs.
I stopped using 10+ heat range plugs and never looked back, even on a single turbo application. I recently picked up a set of BUR9EQP plugs from Advance Auto for $6.50 each and I couldn't be happier with them. Racing plugs are best for racing applications. Howard does a lot of racing so I can see why he prefers them, and they do have some advantages, but for 90% of the FD's out there isn't two heat ranges colder good enough? You get most of the benefit with none of the drawbacks.
Also, the "longitudinal warping" of the apex seal going over the plug boss is not the issue. It's the fact that the apex seal (more evident in the two piece variety) "seesaws" as it crosses over the swollen spark plug boss due to the uneven pressure being applied by the springs on the different parts of the apex seal. This causes the apex seal to become weak and fail.
07-24-10, 01:16 PM
#34
Agreed. When HC posts something, like anyone else here with a brain I pay attention. But since my car is primarily street driven, mildly modded (~280-300 whp), sees only an occasional autocross and no track days...I filter it a bit for what is right for me.
07-24-10, 01:45 PM
#35
Racecar - Formula 2000
Disclaimer: I am not a spark plug expert.
However, here are a few of my opinions on what "heat range" means and how it might affect the rotor housing surrounding it:
A hotter (vs colder) plug is one that has electrode and center-electrode insulator designs such that the electrode and its insulator run hotter, so as to burn off possible contaminants that would cause fouling. Also remember that fouling is forming a conductive layer on the center electrode insulator that shorts out the spark. The plug body does not necessarily run hotter, and as a matter of fact, may even run a bit cooler with a hotter electrode tip, since less heat may be transferred from the electrode and its insulator to the plug body.
So, the factors, IMO, that would cause the plug body and the rotor housing around the plug body to run hotter and possibly deform are higher combustion temperatures due to leaner mixtures, less fuel cooling, more HP produced, mild detonation, etc.
IMO, therefore, if, in fact, a "cooler" plug helps prevent this spark-plug hole deformation, it is most likely due to preventing detonation, not a heat-transfer issue. So, if tuning, etc., is correct and detonation does not occur, the plugs are cold enough, and using colder plugs than required will just lead to fouling problems, etc.
However, here are a few of my opinions on what "heat range" means and how it might affect the rotor housing surrounding it:
A hotter (vs colder) plug is one that has electrode and center-electrode insulator designs such that the electrode and its insulator run hotter, so as to burn off possible contaminants that would cause fouling. Also remember that fouling is forming a conductive layer on the center electrode insulator that shorts out the spark. The plug body does not necessarily run hotter, and as a matter of fact, may even run a bit cooler with a hotter electrode tip, since less heat may be transferred from the electrode and its insulator to the plug body.
So, the factors, IMO, that would cause the plug body and the rotor housing around the plug body to run hotter and possibly deform are higher combustion temperatures due to leaner mixtures, less fuel cooling, more HP produced, mild detonation, etc.
IMO, therefore, if, in fact, a "cooler" plug helps prevent this spark-plug hole deformation, it is most likely due to preventing detonation, not a heat-transfer issue. So, if tuning, etc., is correct and detonation does not occur, the plugs are cold enough, and using colder plugs than required will just lead to fouling problems, etc.
07-24-10, 08:40 PM
#36
I think the better solution for preventing warping in that area would be to groove the housing coolant passages in the area of the spark plug holes for better heat transfer, and be religious about staying out of boost until the engine is at full operating temp.
07-25-10, 12:39 AM
#37
That's a stretch, don't you think? The factory plugs are 7 heat range in the leading, and figure that much of your rotor housing's life has been exposed to that stock heat range. Isn't 9 cold enough? Only Rx-7 owners feel the need to run 3 and 4 steps colder than stock... and many turbo 4 cylinder piston engines will run EGT's close to what a rotary will do (1500F or more preturbo).
Race plugs are at best a necessary evil. Some of them require a special socket and/or do not have the same length as the factory plugs. Many of them are expensive ($30+ per plug) and need to be ordered. They foul out more easily. You have to gap them. Some of them are non-resistor, which HKS warns against for those using a Twin Power. A lot of them hurt fuel economy and idle. There are so many drawbacks and the marginal benefit compared to running 4 of the factory platinum BUR9EQP plugs is just not there for most applications--even single turbo applications. You're not going to blow your car up just because you didn't use 10 heat range plugs. I haven't seen any controlled testing to show that 10 heat range plugs by themselves are going to reduce wear and cracking at the spark plug hole compared to the OEM 9 heat range plugs.
I stopped using 10+ heat range plugs and never looked back, even on a single turbo application. I recently picked up a set of BUR9EQP plugs from Advance Auto for $6.50 each and I couldn't be happier with them. Racing plugs are best for racing applications. Howard does a lot of racing so I can see why he prefers them, and they do have some advantages, but for 90% of the FD's out there isn't two heat ranges colder good enough? You get most of the benefit with none of the drawbacks.
Only solution is to buy new housings... parts wear out, especially when you modify a car.
Race plugs are at best a necessary evil. Some of them require a special socket and/or do not have the same length as the factory plugs. Many of them are expensive ($30+ per plug) and need to be ordered. They foul out more easily. You have to gap them. Some of them are non-resistor, which HKS warns against for those using a Twin Power. A lot of them hurt fuel economy and idle. There are so many drawbacks and the marginal benefit compared to running 4 of the factory platinum BUR9EQP plugs is just not there for most applications--even single turbo applications. You're not going to blow your car up just because you didn't use 10 heat range plugs. I haven't seen any controlled testing to show that 10 heat range plugs by themselves are going to reduce wear and cracking at the spark plug hole compared to the OEM 9 heat range plugs.
I stopped using 10+ heat range plugs and never looked back, even on a single turbo application. I recently picked up a set of BUR9EQP plugs from Advance Auto for $6.50 each and I couldn't be happier with them. Racing plugs are best for racing applications. Howard does a lot of racing so I can see why he prefers them, and they do have some advantages, but for 90% of the FD's out there isn't two heat ranges colder good enough? You get most of the benefit with none of the drawbacks.
Only solution is to buy new housings... parts wear out, especially when you modify a car.
Disclaimer: I am not a spark plug expert.
However, here are a few of my opinions on what "heat range" means and how it might affect the rotor housing surrounding it:
A hotter (vs colder) plug is one that has electrode and center-electrode insulator designs such that the electrode and its insulator run hotter, so as to burn off possible contaminants that would cause fouling. Also remember that fouling is forming a conductive layer on the center electrode insulator that shorts out the spark. The plug body does not necessarily run hotter, and as a matter of fact, may even run a bit cooler with a hotter electrode tip, since less heat may be transferred from the electrode and its insulator to the plug body.
So, the factors, IMO, that would cause the plug body and the rotor housing around the plug body to run hotter and possibly deform are higher combustion temperatures due to leaner mixtures, less fuel cooling, more HP produced, mild detonation, etc.
IMO, therefore, if, in fact, a "cooler" plug helps prevent this spark-plug hole deformation, it is most likely due to preventing detonation, not a heat-transfer issue. So, if tuning, etc., is correct and detonation does not occur, the plugs are cold enough, and using colder plugs than required will just lead to fouling problems, etc.
However, here are a few of my opinions on what "heat range" means and how it might affect the rotor housing surrounding it:
A hotter (vs colder) plug is one that has electrode and center-electrode insulator designs such that the electrode and its insulator run hotter, so as to burn off possible contaminants that would cause fouling. Also remember that fouling is forming a conductive layer on the center electrode insulator that shorts out the spark. The plug body does not necessarily run hotter, and as a matter of fact, may even run a bit cooler with a hotter electrode tip, since less heat may be transferred from the electrode and its insulator to the plug body.
So, the factors, IMO, that would cause the plug body and the rotor housing around the plug body to run hotter and possibly deform are higher combustion temperatures due to leaner mixtures, less fuel cooling, more HP produced, mild detonation, etc.
IMO, therefore, if, in fact, a "cooler" plug helps prevent this spark-plug hole deformation, it is most likely due to preventing detonation, not a heat-transfer issue. So, if tuning, etc., is correct and detonation does not occur, the plugs are cold enough, and using colder plugs than required will just lead to fouling problems, etc.
-J
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