Exige S with Tubular backfiring issue

[woteva]

Tried searching but couldn't find anything.

Recently fitted a Tubular exhaust manifold, decat chamber and silencer to a 2006 Exige S.

It's backfiring badly now and we are getting pinged for noise at trackdays (even though it passes the static easily). Definitely the backfiring that is tripping the noise sensors.

Any suggestions on what can be done about this? Is there anyone out there able to fiddle with the stock ECU? Or any piggyback options worth looking at? I can't be the first to come across this problem, as I would imagine it's the same for everyone who fits a system with less backpressure than stock system.

Thanks

[woteva]

Just for further clarification, the backfiring is on gear changing, ie snap the throttle shut and bang. And yes, it's the standard Toyota 2ZZGE engine.

[The Bandit]

What size silencer have you got? Are you sure it's backfiring, i.e is there a loss of power, stutter/hesitation? If not it sounds like it's just popping on a full bore upshift which will be more pronounced if you have a small (6") silencer.

[gregpe]

Hi
I think overrun fuel cut will create that noise not sure on oem ecu you wont be able to disable it .. i think stand alone is an option .

[woteva]

It's a 7inch, and yes it's popping on upshift.

Yes, aftermarket ECU will fix I guess, but I was thinking I suppose there must be other people who run this setup, and I'm surprised if aftermarket is my only option? Surely I can't be the only stock ECU/Toyota/2bular/Trackday guy around?

[Viperzs]

It's going to be the decat doing it as mine has started doing it a lot more after decat.

[woteva]

I was hoping it doesn't mean reverting to fitting the cat again, but maybe you are right. The version of manifold that jim made for me doesn't allow the fitment of the standard cat, so I'm a bit stuffed really.

[The Bandit]

Give it some more miles to coke up a bit and see if it still does it.
If not I'm sure Jim will modify the manifold to allow sports cat to be fitted.

[Equus]

Air leak?

[321freeflow]

Approx. 90% of my customers ask if they will still have the poppin an the bangin after changing the exhaust.

Unburnt fuel igniting in the pipework/silencer? - Yes, that's JUST what I want

These cars are seriously over-fuelled from factory. Why? Ask Lotus. The Elise SC (with the MP45 SC) destroys its factory catalyser faster than the other models - over-fuelled/over-heated - Why? Ask Lotus. I know because Lotus don't carry any catalysers in stock, so the dealers are always asking for replacements. When I re-pack a silencer from the SC'd cars, the internals are coated black and reeking of fuel.

I don't know anyone - ANYONE - who can successfully re-work/re-tune that fkn Lotus T4 ECU. Crappy re-flashes "sometimes" work - but sometimes they don't.

Removing the catalyser from the exhaust WILL cause issues - but there's plenty people out there running that set-up. Use a de-cat/silenced de-cat pipe (SDCP) you can fit the little extensions to the 2nd Lambda to "fool" the ECU.

These work "sometimes" - most times they don't. Different extensions are required for the different motors. In other words there is no easy/quick fix. If you run your car on the road in standard form, you won't have many issues. If you fit performance parts and track/race your car, you need to understand the implications and be prepared to spend £'s and tolerate the hassles. I have mates with the Nissan GTR who have different maps at the push of a button! Nissan boasted the ECU was un-crackable - took the aftermarket 12 hours. The numbers for the Lotus aftermarket don't add up for that level of investment.

The later T6 ECU's are a definite improvement over the T4's - I guess even Lotus got fed up with all the hassles.

For John's problem: he's coming at this from the wrong angle. Pops an bangs - as I've said, they're integral with the Lotus install. The REAL problem - the circuit noise limits - and they're becoming ever-more stringent. We're a very noise-averse society now. Electric cars will solve that of course - I'll be retired by then and happily so.

I have advised him to put in some time on a dyno, check out the AFR's, the ignition components etc etc. There's dynos and there's dynos - told him which one to use.