When is Boost Controller Needed?
 

Hey guys,
I have a 93 FD that only has 43k miles on it currently. I have done these following mods so far: greddy FMIC, Greddy Air Intake, KOYO Radiator, Individua Exhuast, and the removal of the AST Tank. My question is should I considered purchasing a boost controller once I put on a downpipe for the car? I've noticed my boost having a spike up to 12psi at times, not consistently.

A boost controller is needed when you want to RAISE the boost level. It will not lower the boost.

A boost controller is usually needed on the FD with any significant modifications to the intake side....i.e. the IC and the open intake. If you're spiking now it's probably in the morning or evening when ambient is lower and the air is denser. IMO, you should get a BC, either manual or electronic. Search in the 3rd Gen. section for more info.

Should I shouldn't concern to much about that boost spike should I? And if getting the downpipe would more than likley make the spike jump higher correct? Thanks guys for your thoughts

From the 3rd Generation FAQ sticky.........
Boost Creep - A steady increase in maximum boost, usually at higher rpm. Creep is caused by the exhaust flowing more than the wastegate and turbo can control. The (only) solution is to either restrict overall flow or enlarge the wastegate opening. Installation of a cat-less midpipe often cause boost creep.

Boost Spike - A sudden surge in boost, usually appearing between 4500 and 5000 rpm. This is dangerous on stock ECU systems, which sometimes do not detect and compensate for this extra boost before detonation occurs. Boost spikes often begin to occur after installing a modification that increases flow, and can be resolved in most cases by installing a better boost controller.

The downpipe is on the exhaust side, I doubt it will have any great effect on the spike issue. And as long as you keep a main cat, you shouldn't have any problem with creep either.

Thanks guys! Pettit downpipe will be my next purchase :nod: She about to sound peeerrrrttyyyy

Pettit should be a good choice. Don't recall off-hand, but I prefer ones with the bracket on the down-stream end for fastening to the support bracket oo the transmission housing. Not all of the aftermarket DP's have it. I'd get a new gasket too. They're alittle pricey, but worth the piece of mind IMO for a good seal. Remember high-temp antiseize on the studs.
IIRC, Pettit also offers heat-coating. I'd get it. Either that or header-wrap will reduce underhood radiant heat considerably.

If you are getting a boost controller get an Electronic rather than manual. And they are cheap second hand and work pretty well. I bought a HKS EVC for $100 a few years back.

Your boost is most likely spiking because of all of the air you're freeing up with the intake and exhaust. Honestly I am new to rx7's but very familiar with DSM's, stuff like this usually happens if you perform the above mentioned mods (or very similar mods) but don't port out the stock internal wastegate flapper hole on the turbo, or if you have kinked vacuum lines going to the wastegate.

Check your wastegate vacuum lines for kinks, or punctures.
Do a boost leak test, also make sure your wastegate actuator isn't sticking.

If the above fail, its more than likely time to start porting your wastegate hole. If the wastegate flys open when you hit peak boost, you may be flowing so much air/exhaust that it cannot dispel through the stock wastegate flapper hole fast enough to normalize the boost pressure, therefore it spikes.

Overwhelming the wastegate...too small of a wastegate causes creep, not spike. And the BC won"t help that. On the FD keeping a main cat is usually enough restriction to avoid it. A BC won't do anything for creep...just spike. Sounds like the op"s issue is spike based on those mods. No porting needed.

I got it mixed up then, my mistake.