I have been thinking about ignition coils ever since the thread discussing the low priced 6 coil 'kit'. I got to thinking about the coils and the front / back differences. I know that the coils are marked FF and RR and I know that Acura gives them separate part numbers. I hadn't really paid much attention to the coils beyond that.
I had presumed that the difference was due to the 3 pin (OBDII) connector orientation; but, then I recalled (and the parts diagram seems to confirm) that the connectors on the front coils are located on the lower edge of the coil and on the rear coils are on the upper edge of the coils (when they are installed in the engine). If the connectors were always on the top (or bottom) of both the front and rear coils that would make the front and rear coils different because of the connector location. The fact that the connector location changes front to back suggests that at least the top half of the front and rear coils appear to be identical. Look at the photo of the 6 coils that Kaz posted:
http://www.nsxprime.com/forum/showthread.php/184080-Coil-Pack-bad-should-I-replace-all-of-them
If you mentally rotated one of the RR coils 180 deg so that the RR is upside down, it sure seems like the RR coil is identical to the FF coil.
So, what am I missing? Did Honda do something weird like changing the assignment of the 3 pins in the connector for the front and back coils? My car is in secure storage so I can't get at it to check the location of the misfire detection connection on the front and back connectors to determine if it is different.
The reason I got off on this track is that it is the rear coils that typically suffer from the corrosion / contamination failure problem. The front coils are readily available, probably because they share a common part number with some of the TLs ('96-'98) and RLs (96-04). On the TLs and RLs, Honda uses the same coil on the front and back cylinders. It is only the NSX that has the unique part number for the rears and because of that, the rear coils are typically only available from Acura. Lots of non Honda vendors list the front coils as available. Given the production numbers for the RL and TL, there is probably a good chance that spares for the front will be readily available for a long time. Unfortunately, NSX history suggests that it will not be the front coil that you are likely to need.
If the NSX rear coils are just front coils with RR stamped on the top, then I am going to go and think about something else more important like food or beer because parts availability is not likely to be an issue. If there is a physical / fit difference between the front and rear, then I might go purchase a rear coil to have as a spare or at least think about how I could repurpose a front coil to fit on the back. So, does anybody know whether there is a material difference between the front and rear coils and what that difference is?
As another little head scratcher, Acura lists different part numbers for the front and rear coils on the pre OBDII cars; but, the price of the coils for the front and rear is the same. On the later OBDII coils, the fronts list for about $20 more than the rears.
I had presumed that the difference was due to the 3 pin (OBDII) connector orientation; but, then I recalled (and the parts diagram seems to confirm) that the connectors on the front coils are located on the lower edge of the coil and on the rear coils are on the upper edge of the coils (when they are installed in the engine). If the connectors were always on the top (or bottom) of both the front and rear coils that would make the front and rear coils different because of the connector location. The fact that the connector location changes front to back suggests that at least the top half of the front and rear coils appear to be identical. Look at the photo of the 6 coils that Kaz posted:
http://www.nsxprime.com/forum/showthread.php/184080-Coil-Pack-bad-should-I-replace-all-of-them
If you mentally rotated one of the RR coils 180 deg so that the RR is upside down, it sure seems like the RR coil is identical to the FF coil.
So, what am I missing? Did Honda do something weird like changing the assignment of the 3 pins in the connector for the front and back coils? My car is in secure storage so I can't get at it to check the location of the misfire detection connection on the front and back connectors to determine if it is different.
The reason I got off on this track is that it is the rear coils that typically suffer from the corrosion / contamination failure problem. The front coils are readily available, probably because they share a common part number with some of the TLs ('96-'98) and RLs (96-04). On the TLs and RLs, Honda uses the same coil on the front and back cylinders. It is only the NSX that has the unique part number for the rears and because of that, the rear coils are typically only available from Acura. Lots of non Honda vendors list the front coils as available. Given the production numbers for the RL and TL, there is probably a good chance that spares for the front will be readily available for a long time. Unfortunately, NSX history suggests that it will not be the front coil that you are likely to need.
If the NSX rear coils are just front coils with RR stamped on the top, then I am going to go and think about something else more important like food or beer because parts availability is not likely to be an issue. If there is a physical / fit difference between the front and rear, then I might go purchase a rear coil to have as a spare or at least think about how I could repurpose a front coil to fit on the back. So, does anybody know whether there is a material difference between the front and rear coils and what that difference is?
As another little head scratcher, Acura lists different part numbers for the front and rear coils on the pre OBDII cars; but, the price of the coils for the front and rear is the same. On the later OBDII coils, the fronts list for about $20 more than the rears.
