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-   -   Question about downpipe (https://www.rx7club.com/new-member-rx-7-technical-256/question-about-downpipe-1133787/)

DeltaTech 02-19-19 09:17 PM

Question about downpipe
 
Hey everyone, so I recently purchased a very low mileage 93 touring. The only thing that was done by the original owner was the downpipe, which is from pettit racing. Should I consider doing anything else since that is there, or I be fine? I plan on doing the reliability mods as I go, but I wasnt sure if there was anything that I would need sooner than later with having the downpipe. I'm not looking for a track monster or anything, just something I can enjoy on nice days.

cr-rex 02-19-19 09:23 PM

Nope.... you're fine where you're at. Do the reliability mods like you planned and enjoy yourself. It wouldn't hurt to get a power fc or something and get it tuned. It will run better than stock.

DeltaTech 02-19-19 09:43 PM

Thanks, I was going invest in a pfc at some point. From every other car I've owned, stock tunes always seem to leave room for or need improvement.

cr-rex 02-19-19 11:00 PM

Absolutely... if nothing else, the power fc allows the setting of the fans to come on at whatever temp you want which allows for the car to run cooler overall. The fc thermoswitch mod does this as well but it only brings it down to whatever temp the switch is set for.

BLUE TII 02-20-19 01:06 AM


cr-rex
Nope.... you're fine where you're at. Do the reliability mods like you planned and enjoy yourself. It wouldn't hurt to get a power fc or something and get it tuned. It will run better than stock.



I would only consider installing a Power FC (or better plug and play ECU) once you have decided to run over 10psi (or let turbos creep over 10pis with other mods) and/or you want to upgrade the injector sizing.

The advantage of the stock ECU is that it has its variable boost cut (10psi in high rpm) to avoid overboosting, it has working knock control as well as other OEM safety features to perserve the engine.

No aftermarket ECU has implemented knock control as
far as I know.

Sgtblue 02-20-19 03:53 AM

I agree that you don't need to do anything because of the downpipe. The car came with a pre-cat. In addition to baking everything under the hood, it could collapse and damage the engine...so that was the first 'reliability mod".
If you're not having terrible issues with hesitation at transition (at full operating temp), not wanting to remove emissions or increase boost I wouldn't be in a hurry for a PFC. Just get that aftermarket temp gauge, a boost gauge and be sure to warm the car up fully before going into boost...and enjoy.

BLUE TII 02-20-19 09:00 PM

I bought my FD with only downpipe, cat back and dual hallman pro RX boost controlers (wastegate, pre-control) to perfectly manage 10psi boost and the turbo transition smoothly and I loved it.

Went back to stock to race in stock class and hated it.

Went back to how I bought it and added a small stock mount IC, the metal Y-pipe and it was prime (~250rwhp).

You can run 10psi (without any creep) and the stock ECU if you retain the stock airbox and the stock cat as a restrictions.
If you run that and have properly executed cooling modifications, silicone vacuum hose job, regular maintenance; I feel that is about as reliable as a twin sequential FD can be.

Now I ruined it with more mods and worry every time I start the damn thing.:scared:

KYPREO 02-20-19 10:21 PM


Originally Posted by BLUE TII (Post 12331428)
No aftermarket ECU has implemented knock control as far as I know.


Of the consumer level ECUs, Haltech Elite 1500 and above and Adaptronic Modular both have knock control. I'm sure all the top-level motorsport grade ECUs like would also have it. Motec definitely has it.

That said, I'm of the understanding that closed loop knock control is of limited value on rotaries due to its insensitivity to knock and the fact the engines aren't as responsive to increased timing, limiting the potential gains knock control might otherwise bring. Knock sensing is f course good to have for tuning and logging purposes.

BLUE TII 02-21-19 09:05 PM

Those aftermarket ECUs have the ability to set up a closed loop knock control, but no one does it since they don't have a laboratory and experience to set the values/mapping.

Its like saying they have real motorsports anti-lag.
Yeah, the software is there; you just need the anti-lag combustion chamber, fuel injector, plumbing, turbo speed sensor, and knowledge to set it up.

And yes, as you say motorsports vanti-lag is way easier to implement than OEM quality knock control.


That said, I'm of the understanding that closed loop knock control is of limited value on rotaries due to its insensitivity to knock and the fact the engines aren't as responsive to increased timing, limiting the potential gains knock control might otherwise bring. Knock sensing is f course good to have for tuning and logging purposes.
If you compare the number of stock ECU FDs that have blown apex seals from owners putting 87 octane in accidentally I bet it is much lower than the number of FD owners that have blown apex seals running aftermarket ECUs with no closed loop knock control.

I am sure part of that is 250rwhp (limits of stock ECU fueling) of boom does a lot less damage after a knock or two and then ECU preventative actions versus 400rwhp worth of boom and knock knock knock (knocking on heaven's door) till engine is gone.

I am not sure if the stock ECU only pulls timing with knock or if it also adds fuel and lowers boost or even cuts spark- I will see what I can find.


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