C4AUSVETTE

Hey Guys,

I have an 1986 4+3 Corvette and I would like to upgrade to FX3 suspension.

I live in Australia and have a RHD conversion and due to import regulations, combined with modifications already completed selling and buying a FX3 is not really an option.

Has anyone done this or know whats involved, I am guessing there is the loom, shocks and actuators, switch and module. Possibly a BCM.

Does anyone know what part the BCM plays is that only to display the codes or does it feed information to the module (i.e. speed).

If it is just codes is it required, can i install it and not have the codes display?

Would a later model BCM function in a 86 correctly?

Does the module interact with any other part of the car (ECM or ABS, etc)

Thanks

mike100

I would venture a guess and say that the BCM isn't very involved with FX3. The fx3 has the most basic diagnostic and its own pin to ground on the aldl for trouble codes. Even the tech1 scanners can't get serial data from the fx3 controller- it goes solely to the flashing light in the instrument panel. I believe it is an add-on option outside of the BCM. it is simple and autonomous.

you should double check the schematics to the newer cars to know for sure, but I kind of think it would be possible to feed it a VSS to the appropriate pins on the fx3 controller to get it to work. You'll just need the harness from a donor car, or at least the connector ends and make your own.

FX3 is neat if you have one that works and doesn't need massive repairs, but I could also learn to live with a good conventional damper.

cv67

This is going to be an expensive project if youre ready for it.

When they are working right they are a nice novelty not sure Id like to own another FX3 car though.

Adjustable coil overs

Keep us posted on the project, first one like this Ive seen.

Churchkey

I agree & suggest a good set of shocks or a coil over conversion.

After owning a C4 with base suspension & now one with FX3 I would not consider buying another C4 without FX3 a deal breaker.

ddahlgren

My next Corvette(a C4 but older) will have coilovers, will be a must with rising rate springs I think it would move the ride quality 2 decades into the future. Personally I think the biggest problem with C4 ride quality is the composite spring. On a smooth road they are a joy anywhere else an experience might be the best way to describe them. Even a steel leaf spring is rising rate.

cv67

Well said.
Ok for the base consumer no good for the enthusiast

c4zf6nut

Hi there,

There are lots of good stuff in this thread. I don't want to go on a tangent but here is some thought.....

Later cars have softer springs, if it is ride comfort you are looking for, I would try that.

Second, I have an FX3, even Touring model on my 89 is not comfortable at all. I believe my springs are Z52 in 89, if FX3 option was ordered.

Believe it or not, I am going to try removing brand new Bilsteins (at $200 a piece), and install $10-15 Monroe Sensatracs. I think I should get softer springs first!

C4ZF6nut

c4cruiser

Spring rates are determined by the suspension option a car has. Look at this chart to see what the spring rates are for a given year and the various suspension packages. Also note that the 88 and later cars have a higher spring rate than the 85-87 cars.

Z52 was only available in 87 and 88, not 89.

FX3 was offered as an option where the base springs were still used. Z51 cars had stiffer springs and HD shocks. Note that in 89 and 90, the RPO R9G cars got FX3 shocks.

FX3 was included with Z07. It's entirely possible that the shock valving (and resulting stiffness) for the FX3 shocks that came with Z07 was different than it was for the FX3 shocks that could ordered with base suspension cars.

Changing to later springs may help provide a softer ride, but shocks for the later years would be typically valved for the lower spring rate. So if you order shocks for your 89, you may not get the ride you want if you go with something like a 93 or 94 spring later on.

The shock stiffness of the FX3 shock changes as vehicle speed changes, even within each of the three settings. These shock setting will overlap. For example, the FX3 shock on the Tour setting is actually stiffer at 70 MPH than the Performance setting at 25 MPH.

Monroe used to make decent shocks years ago. I have not heard very many good things about them in the last 5-7 years. And one thing to think about is that shocks that are too soft can adversely affect handling. Corvettes, being designed as sports cars, are not expected to ride like a Caddy or Lincoln.

For the OP. while you plan sounds like a challenge, I would bet that the cost of doing a retrofit will be very high for what you get. Something to consider is the mounting of the FX3 shocks in the existing mount points. The towers in the front are narrower than the 88 and later cars. Also, the rear top shock mounts in the later cars don't use a rod. There is a cutout in the bottom of the frame rail where the top shock mounting bracket attaches to the frame. The actuator hides in the frame rail.

It's possible that the FX3 shock is a different length compared to the early shock. YOu may want to contact Bilstein to verify the shock dimensions to make sure they will fit in the early car so you don't wind up having to change to later suspension components.

c4zf6nut

It does not change the fact that 89 FX3 is a Z52 spring rate (88). If you were not too lazy, you could verify that.-) Clearly, they could not know what spring rates were going to be used into the future, but they knew what the codes meant.

In this case, one could order Z51 and FX3 together, but they would be getting Z52 springs, even if option codes showed Z51.

Now, suspension design changed for 89, and you are absolutely right about the differences in shocks, which would make this a no go.

My understanding is that the Z07 option appeared as a way to offer Z51 stiff springs for track/competition cars (91-) with FX3. The rear springs are quite stiffer as opposed to 89 FX3, but the fronts are slightly weaker. It seems to be Z07 option will ride much worse on a typical road. Rear spring rate affects ride quality.

I am intrigued by Monroe's technology in Sensatrac since it is fairly soft to begin with, and tightens up when it senses higher frequency oscillations due to speed, much like FX3, but in a mechanical fashion. The parent company Tenneco is now OEM to many European manufacturers like Mercedes, and Monroe brand reputation is pretty good in Europe. They are considered equal of Delphi and other brands if not better.

The later C4 cars, are really Cadillacs in terms of spring rates. 1996 Z51 has softer springs than 89 base model. Therefore, all this talk about Cadillac vs Corvette is rubbish. Clearly, Corvette engineers decided to soften the ride as time went by,. Furthermore, they went to a staggered design with narrower tires in the front.

As a result, 89 cars are autocross champs, but I don't race an would have preferred a better ride in the later car, like a 1996.

To get back the original poster, his 86 has fairly soft front springs (like a 1996) and rears are about the same as FX3. he could benefit from a soft shock like Monroe Sensatrac.


C4ZF6nut

kenv

I have the Z51 option on my `87, & I pulled the Bilsteins & put in Monroe`s from AutoZone. Both my wife & I enjoy the ride now (your mileage may vary )

oldalaskaman

luvin my monroe sensatrac's, sorry, didnt mean to go off topic. good info on this thread, respectfully, bob