Ignition coils do not like heat. So why on earth would Mazda package the ignition coils directly
on top of the engine? The second generation RX-7 had the coils located on the fender. So why did the
FD move them to the engine? Two reasons come to mind 1) the shorter run for the ignition wires may improve
their performance and 2) packaging and ease of assembly at the factory. There simply isn’t much room to
put the coils anywhere else in the FD engine bay. Regarding 1) I looked at the information quoted by
M&W Ignitions (a site found on the web. Legit? You decide. I found
their info believable) From the M&W catalogue page 3: "They (the coils) should be mounted in a part of the
engine bay that receives fresh air flow." Again, note the location of the stock FD coils, buried under the
UIM sitting directly on top of the engine block. I’m thinkin' that’s not a very good location for ignition
coils. READ: It's hot in there! Additionally from page 3 of the M&W catalogue: "It is recommended that coil
wires should not exceed 1 meter (~3’) in length." The stock FD wires are about 12-18" in length. The 2G Turbo
II RX-7 wires are about 24-28" in length. I did a trial run, with a set of 2G wires, to the location I wished
to relocate the coils and they were more than long enough. So the wires for relocating the FD coils are
well below the recommended maximum length. Regarding the coils themselves why not use an aftermarket
performance coil? Stock FD coils have been proven reliable to well beyond 450rwhp. With suitably sized
ignition wires, relocating the coils will increase reliability by keeping the coils cooler, would not result
in any reduction in performance, and will free up space under the UIM to run the fuel lines. So what did I do? A great one-time forum group buy for a machined aluminum ignition coil relocation
bracket was the solution. I’ve always liked the idea but lacked the motivation to fabricate my own bracket.
And then the group buy comes up and I’m sold. The relocation bracket fits perfectly on the driver’s side
fender next to the brake booster and relocates the igniter just below it. The coil wiring harness is just
long enough…just. I did have to snip one wire-tie to extend the harness length by about 1 inch. That’s all.
The stock FD ignition wires were obviously going to be too short now that the coils have been moved. I had considered using a
set of 2G ignition wires but after trial fitment determined they were actually way too long! Ok I’ll make my
own. I bought some 2G RX-7 Magnecor Competition KV85 8.5mm wires off eBay for a song. I then contacted
Magnecor and ordered replacement electrical connectors and rubber boots. I also
invested in an ignition wire crimping tool from Accel. With all the
necessary parts and tools I made myself a set of custom cut-to-length ignition wires for my relocated
coils. Using the crimping tool was easy and straightforward and in fact I believe my work to be of higher
quality than the factory assembled wires! I also had installed new 10 heat range NGK racing spark plugs
in both leading and trailing locations. They are less pricey, at about $7.00 each, than the Denso 10.5 plugs, which
run about $35.00 each the last time I checked, but have they have a thicker insulator which causes some issues
with screwing them into the housings. PFS was kind enough to machine a custom
socket for me to fit these spark plugs.
Moving the coils may cause some anguish however. A drawback of relocating the coils to the fender
was there is no way to maintain the OE cruise control configuration. I didn’t have cruise control on
my R1 model but I had mounted the HKS TwinPower
to the
firewall where the coil packs are now mounted (See HERE
for the original mounting),
the fuel pressure sensor (see HERE
for the original location) was in the way, and my
*awesome* custom mini-washer fluid reservoir setup.
I did relocate the HKS TwinPower to a location ahead of the front wheel well on a new custom made
mounting bracket but I have yet to find a good location for my mini-washer fluid reservoir. The new
location for the TwinPower is actually better since it is in a cooler location and still within reach
of the HKS wiring harness adapter. The fuel pressure sensor I remounted on a new “damped’ bracket
(vibration is bad juju) to just below the brake booster and used AN fittings and a braided SS -4 line,
instead of rubber hose and an array of bulky brass barbed fittings, to plumb pressurized fuel from the
fuel distribution block on the engine to the sensor…about 3 inches away! The braided SS line was looped
to allow for engine movement.
For more specifcs on the reconstruction of Princess go to the following pages:
Rebuild and porting of the 13B short-block to include port matching the intake side.
Custom baffled deep well aluminum oil pan.
Installation of dedicated 2 stroke oil feed system.
Replacement of all the fuel system lines with SS braided hose and AN fittings – tank to engine.
Installation of a dual fuel pump arrangement with fuel tank baffle box cover.
Replacement of all turbo hoses with SS braided hose and AN fittings.
Porting and polishing of the throttle body and removal of the double throttle control assembly.
Turbo “improvements” to fix lower grade hardware and potential trouble areas.
Installation of 3 Bar MAP sensor and tuning for higher boost applications.
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This page last updated March 19, 2009