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My5ABaby
08-09-2011, 09:39 PM
Are S4 and S5 FCDs interchangeable?
Boosted FC
08-10-2011, 01:18 PM
Are S4 and S5 FCDs interchangeable?

I don't think they are.
Ender
08-11-2011, 09:54 PM
seconded. you might find a store that sells one for each and see if they're the same or not (part number, or send support a question....). Racing Beat might sell them.
My5ABaby
08-12-2011, 07:59 AM
Racing Beat lists them differently but HKS (albeit eBay) lists them together. I found an S4 one to use so I'll be fine, but maybe good to know for future reference.
RETed
08-12-2011, 09:36 AM
Most of them are interchangable unless explicitly stated.
(This info is probably outdated, since I haven't messed with FCD's in years.)
The older Racing Beat ones (metal case) could be used on any model?
The only one that I know that doesn't work is the Trust / GReddy one - this unit is specifically listed as a Kouki FC turbo only application.
Trust me, I tried - I slapped one on my old set-up on my 1987 Turbo II, and it didn't prevent the overboost fuel-cut with the stock ECU. :P


-Ted
My5ABaby
08-12-2011, 12:16 PM
Most of them are interchangable unless explicitly stated.
(This info is probably outdated, since I haven't messed with FCD's in years.)
The older Racing Beat ones (metal case) could be used on any model?
The only one that I know that doesn't work is the Trust / GReddy one - this unit is specifically listed as a Kouki FC turbo only application.
Trust me, I tried - I slapped one on my old set-up on my 1987 Turbo II, and it didn't prevent the overboost fuel-cut with the stock ECU. :P


-Ted
Good info.

That's really weird considering how they work. I would think that if one worked, they all would. Perhaps the voltage is slightly different, e.g. 3.6 S4 and 3.7 S5 and the Greddy one activates at 3.65v or something. :dunno:
RETed
08-12-2011, 12:51 PM
It's probably due to the design of the FCD itself...

The older Racing Beat units were just resistors inline of the signal.
This basically shifted the overboost fuel-cut point to a higher boost level.
I think I was able to hit it *with* the older Racing Beat FCD at around 18 - 19psi.

Most of the new ones are voltage-clamp design, which just keeps the signal at a predetermined maximum *if* the input voltage exceeds that level.
Since the overboost fuel-cut boost level is different between the FC turbo series, this is why you see specific applications explicitly stated.


-Ted