I have both the HKS and Fujitsubo, for the AW11 SC
(and an HKS for a NA), and the Fujitsubo appears to be much better made than the HKS for the SC.
Yes, the Fujitsubo does appear to be entirely made of stainless steel.
The only bad part about that is that it will pretty much turn a dark shade after a lot of use.
This just happens with heated stainless steel I'm afraid.
At least this is what I have seen of other pictures of them.
I ordered the SC HKS before I knew about the SC Fujitsubo, but was not that impressed with it once I saw it.
Their inlet pipe
(hole diameter), at the inlet flange, is almost no bigger than stock.
However, the pipe diameter then increases to the size they state on their website and elsewhere.
This does no good what so ever, because it can't miraculously overcome the limited flow through the smaller hole at the flange opening.
That is really stupid!
Additionally, HKS uses a twin canister muffler assembly, for their SC model, which is connected by a small pipe whose diameter is also smaller than the pipe that leads away from the inlet flange.
I think the only real purpose their exhaust may serve is to maintain lower end torque, while perhaps making the exhaust sound better.
Although, I tried it on the car for a little bit and was not that impressed with it.
On the other hand, their model for the NA AW11 sounds quite nice and does make a small improvement to output and is made relatively well.
Now, more good news for the Fujitsubo: their inlet flange
- hole diameter is about 2 1/4", much bigger than stock and bigger than the HKS
(about the same size, or slightly bigger than the small u-shaped part of the HKS pipe, which leads from their inlet flange to their first canister).
The Fujitsubo flange also appears to be thicker/stronger as well.
I know that the HKS ones will bend rather easily if the stock o-ring gaskets are used.
Unfortunately, both HKS and Fujitsubo supply flat gaskets for their exhausts, as neither uses an indented fitment for the oem circular gaskets, like the stock mufflers do.
I have managed to use the stock gaskets on my HKS NA
'87 AW11, but the HKS flange will bend a little.
I am thinking of having the inlet flange on the Fujitsubo modified to accept the o-ring gaskets, as they seal much better.
The HKS seals a bit poorly with their supplied gasket.
The Fujitsubo also has a one piece muffler core, so no small interconnecting pipe, like on the HKS, and comes with both exhaust hangars attached to it
(the HKS also has both of these attached, but their fitting points are not as good as stock and one end just barely fits all the way through one of the rubber insulators).
Another great point for the Fujitsubo is that it actually includes the small attachment, on the canister, which bolts to the catalytic inlet receiver flange, just like stock.
Neither the NA or SC HKS units have this
(very nice touch).
And finally, the exhaust tips on the Fujitsubo also appear to be stainless steel, but are more directly connected to the exhaust outlet pipes, than the HKS ones are, and I think they will start to turn dark as well.
I have not installed mine yet, as I am rebuilding the engine first, but I have seen pictures of them after use, and I think that is the case.
Despite the darkening issue, I think the Fujitsubo is much better built and the stainless steel will surely make it last much longer and is worth the extra cost.
I believe Fujitsubo also states hp gains on their website, which of course HKS will never do and you can listen to a Fujitsubo exhaust for a SW20.
Unfortunately, they did not have a sound clip for the AW11, the last time I checked.
The SW20 sounded rather nice.
I am very anxious to install mine.
).