If you use the data logger functionality, you may notice a quick boost change that can throw off the ignition timing. Example: at WOT boost goes from 7psi to 5psi and back up to 6psi in about a second or less. You'll probably see a corresponding spike in ignition timing values, which can lead to detonation. Chances are the boost isn't changing that rapidly. Unfortunately we can't change the sampling time of the MAP sensor.

We can, however, add a small fuel filter in-line with the vacuum hose that leads to the interceptor. This will help even out the pressure curve and thereby result in better performance. A Fram G3606 fuel filter has a 5/16" nipple, but according to Scott should fit over the blue silicone hose.

The filter has a directional arrow on the body. Air flows slightly easier in that direction. I do not know if it makes any difference which way the arrow points (towards the interceptor or away). Nor do I know if it's better to have the filter closer to the intake manifold or interceptor.

My rough guess is it's better to have the arrow pointing towards the intake manifold and splice the filter in closer to the interceptor. If anyone can chime in with a better placement opinion--and the rationale behind it--please let me know.

 

A 0.03" restrictor will do the same thing.
Most of us are already using one to smooth the boost response of a boost controller or E-Manage.

 

What is a restrictor and where would you suggest sourcing one in that size?

 

Its a little brass pellet with a hole drilled through it - in this case, a 3/100" of an inch hole.
You could probably go up to a .05" or .07" with no problem.

Most machine shops or industrial supply places would have one in the right diameter (it should be slightly bigger than the inside diameter of the vacuum hose it will be inserted into).
Places like Summit and Jegs have them too.

You could probably make your own by taking a brass hose coupler and crushing the middle of it in a vise.

 

Thanks. So if both the boost controller and interceptor are tapped into the same vacuum line, it would make sense to put the restrictor in front of the Y-connector so it smooths out both units?

 

My experience installing and testing a restrictor pill in the Interceptor source hose (a map sensor based ECU) has been a generally lazy feel in throttle/engine response. Personally, I prefer a filter because a filter seems to "soften" the spikes without a drastic change in signal volume/speed. Scott

 

I would say Yes, I would also suggest using wire ties on all vaccum connections.

 

Then you are using a restrictor that is too small.
The filter is doing the same thing - just match the flow restriction and you will be good.

 

Thanks for the input Jeff, I personally prefer the filter route. Scott

 

What is an interceptor in this context?

 

The engine management system some of us are currently running. Read the rest of the threads for more info.

 

The 1987/88 TIIs use a restrictor pill in the MAP sensor hose to the manifold.

 

A plug and play E.C.U. developed for the turbocharged RX-8's.

 

Correct, and the FD uses a filter, they both work.

 

Jut pay $2 for the Fram. You can afford a turbo, you should be able to afford this.

 

Minor update: I installed the FRAM and the car still works. Throttle response is a little slower but that's to be expected. We'll see how well it evens out the fluctuations later.

 

Any updates on this? My datalogging also shows an erratic boost reading.

 

No update. Dyno scheduled for this weekend.