Shot gun going off in my exhaust after de-catted full system S5
 

Well fitted a de-cat front pipe and knight sports mid- cat back system but is made my car a bit of flop doesn't boost as much and also makes the most epic shot gun sound a few seconds after it comes off boost that you have ever heard.

Anyone able to shed some light.

Running a panspeed ecu
boost controller
dual alternator pulley
full system
fuel pressure reg and fuel pump
still on standard intercooler at the min.:(

High exaust temps + Unburned fuel + No restrictions + Fresh oxygen at end of tailpipe = FIREBALLZ!!!!

Seriously, search.

Yeah execpt the explosion is happening half way down the exhaust??

So what about the power down scenario??:dunno:

afterburn is prevented normally by

1) fuel cut on decel, a function of the TPS

2) the catalytic converter

3) the anti-afterburn valve in the ACV, which requires a functional airpump and proper plumbing for it.

Of which all have been eliminated but surely that wouldn't loose me power and make such an explosion in the exhaust that the whole car shudders??

You eliminated the TPS?:scratch:

Have you got an exhaust leak? Its pretty obvious that what you are experiencing is afterburn; a common "problem" on all modified rx7's. Typically the boom comes after you let off the gas, especially after boost; that's how it has been on every one I've owned.

Not the Tps but the fuel cut the ACV and the cats are gone.

No the exhaust is fully sealed up. I could understand if the afterburn was flames out the back end but its the fact the whole car shakes and the explosion is halfway down the pipe thats got me baffled!!

Not had much experience with rotary modification.

Does teh drop in backpressure alter the port timing or ignition timing in anyway?

Running Extremley rich with No backpressure because you Took the stock exhaust off.
If you get Unburnt Gas In the exhaust and Boost,,you can shoot flames..OR Backfire..(some back fires can be Pretty Loud!)
I was Fumblin around with my car,Bad wiring etc,and I Stomped the pedal and it let out the LOUDEST backfire I had ever heard in my 48 years!.The lady that rents the garage came running out of her house and Thought the car had Blown up!.

It's a rotary...........

Isnt that the truth lol

lol i remember my uncles 89 dodge ram.... heheh the ecu was all mesed up and would randomly backfire and sound like a 12GA going off. on our way to get a new ecu 1:30min away... there was a dog sleeping on the snow bank.... WAS being the word that day... that dog jumped up and sort of rolled down the snow bank funniest hing i ever seen. back on track now... ya if you have a SM hole u might be letting just the wright amount of air in the exaust system to allow it to burn the fuel, check your map and see its getting to much fuel?
in regards to your low power... once you remove the back pressure ur going to run into the prob of boost spikes so you might need to re-tune your car for the extra spooling. i could be wrong tho im just getting into the standalone world my self.
but i know the stock sytem would get boost spikes and would hit fuel cut and cause some odd stuff

Cool I'll have a look at the tuning to see if I can tweak much to make it more stable then.

Thanks for everyones replys nice to get on a site where people are helpful.:lol:

try putting in the stock ECU. who knows what that panspeed is tuned for.

I've got the list of what its tuned for so i'm pretty happy to run it.

did you check too see if there were empty shells in the muffler?

They looked like .50 cal!!:lol:

What part of fuel cut during deceleration do you not understand? See post #4 above.

Hinit: It ain't a happening on your car, evidently.

you neglected to read ( australia only) unless panspeed is australian.

please god tell me you not runing the stock turbo.

The AUSTRALIA version is the same as the USA version. The OTHER version uses a distributor and other odds and ends not used on the USA and AUS versions.



ALL fuel injected Mazda RX-7 cut the fuel injectors when you let off the pedal all the way. Fuel to just one rotor is cut if the pedal (TPS) is let off just a bit. It's a TPS related function. As in set the TPS right and have another go.

With a wideband or narrow band meter you can see this. Or just put a meter to one or both primarys and look at the voltage as you let off the pedal. It'll rise up to alt output voltage when you let off all the way and not start injecting fuel again til around 1300 rpm. I forget the exact figure.

So if your driving along and let off the pedal, the fuel injectors stop pulsing.........and there's no fuel to go BANG in the exhaust pipe.

On the other hand it could be another thing. Got me. Anti Afterburn valves inside the ACV are meant to prevent any chance of this happening

Well mines a uk version.
The TPS sounds a better option to look into if what you say is true regarding fuel cut on decel.
As the acv has been removed the antiburn valves in the air pump setup aren't gonna do anything.


I have re-set the iginition timing to stock after finding my timing light and finding the markings on the crank which was out by probably 30degrees on both leading and trailing rotors but even with that now set I'm still getting the same fault with the massive explosion which must only happen due to some amount of unburned fuel in the exhaust.

Why would running the stock turbo be an issue?