Finding HP in a 2nd Gen RX7

[Fallout]

Hi there,

the 2nd Gen ITS RX7 i bought shows around 160 rwhp.
I think, within the allowed ITS modifications 170 should be possible at least, even if on our track we have very stringent sound restrictions, and the exhaust is for sure limiting a little.
The engine runs very smooth and doesnt smoke and has been recently rebuild by the previous owner. So even though i havent checked the compression yet, i dont suspect too much of an issue there (to be confirmed).

Existing mods are:
- K&N Air Filter
- RB Header and custom exhaust system
- Maybe some of the pollution stuff has been removed

What are the top things that are usually being modified on a second Gen?
Like is the BAC normally being removed?
What about these secondary throttle body flaps?
Any other tips?

Thanks
Matt

[mbuskuhl]

S4 or S5 rotors? Which intake? I did back to back dynos with S4 and S5 intake manifolds on an ITS motor and got 13rwhp IIRC. ECU? There are better exhaust solutions than RB. What type of dyno? Torque? BAC and throttle plates can be removed but don't expect any wild gains from doing it.

[Eagle7]

Can the throttle plates be removed? I assumed that was not legal.

There is HP to be found in the exhaust. ISC used to sell an exhaust that they spent a lot of time optimizing on the dyno. But I think it is NLA.

Are you running the stock ECU? Have you checked your AFRs? I've heard around 13.2-13.5 for max HP.

[edit] Are the 5-6 port sleeves removed? VDI wired open?

[Fallout]

It is a 91, so S5 Rotors, S5 Intake.
I mean, i heard about good the S4 performs with an S5 intake, one should think that an S5 does the same. Or is this, where the difference might lie...

It is the Stock ECU. Dont know how much you would get out of a modified ECU. I always thought with these minimal modifications probably not a whole lot...

I played around with the exhaust a little, but other cars with a similar exhaust setup make way more power.
Attached is the Dyno Sheet. Red line is loud exhaust, Blue line is muffled.
Torque and AFR are in the sheet as well.

What is the VDI? And i will check the port sleeves ...

[mbuskuhl]

Can the throttle plates be removed? I assumed that was not legal.

ISC used to sell an exhaust that they spent a lot of time optimizing on the dyno. But I think it is NLA.



I assumed it was not legal as well, until I got a chance a few years ago to look over a multi winning ITS RX-7 that I know has been through impound many, many times. You'd know the car. I am told it falls under emissions removal.

ISC is NLA, but I have a complete one I am selling, as soon as I get around to taking pictures and messing with it.



What is the VDI?

Variable Dynamic Intake, it's a plastic cylinder in the upper intake manifold that opens and closes changing the path of the airflow depending normal or high RPM operation. It's similar to the 5th and 6th port sleeves/rods/actuators. Both of these units get wired or fastened into a fixed open position.

Was the motor built for racing or is it a street car motor with a few miles?

[Fallout]

All i know is that the motor has been freshly rebuilt by the previous owner.

So i know what the removal of the throttle plates does.
It takes an obstacle out of the airstream.

What would the removal of the BAC achieve? Same principle?

To the VDI: why would i want that open all the time? Wont i loose torque at the low rpm doing that?
I still have to read about the port sleeves, not sure what that was.

[Eagle7]

I don't know what benefit you'd get from removing the BAC. Mine is installed and very useful for warming up the car.

Removing the 5/6 port sleeves and wiring the VDI open allows maximum airflow. You do lose low end torque with them wide open, but there's not enough torque down there to make it interesting for track use anyway. You really need to keep it at full song.

The problem with controlling the port sleeves and the VDI is that you have to keep the air pump, since they are controlled with air pressure, not vacuum.

[Fallout]

Thanks to everyone for the great input.
I confirmed with a fellow racer that all these mentioned mods are somewhat standard and considered legal, at least in the area where i race.
And while i was doublechecking what of the mentioned mods has been done to my car by the previous owner, i discovered one half closed 6 port sleeve that was not wired open. I think, that this has the potential for several hp improvement alone.

Matt