just had my headers ported and wrapped and the work was done by my local subaru garage and the conversation popped up about de-catting and the mechanic said re-mapping after doing this was not neccesary but i have heard different, so wondering what some thought on this subject.
if i were to do it and not map after what could be the outcome.
thanks all

 

What precise model/year of Scoob do you have mate ?

 

sorry about that, its a 53 sti ppp uk

 

I would play it safe and get it re-mapped.. oh and the remap liberates soo much more power so no excuse

 

that was the origanal plan
i did the headers and uppipe, colder grade plugs, airfilter now just waiting for the downpipe 3", and then off for the map but wanted to now if i could do the d/p and wait for a bit before the map or if needed straight away...cant wait really!!!!

 

pre re map on my 2006 jdm had the exhust changed for full system de catted and i never even drove the car over 3 rpm on my way home just would not chance it. car stayed in my garage until re map..

 

I own an 02 WRX and fitted a panel filter, decat downpipe and decat center section. I run on standard unleaded drive as it's supposed to be driven and in the two years since done not a problem.

You will get all the old wives tales about decats and remaps on here - they ain't true

 

But ya aint got the best out of your mods have you.

get it mapped and feel the difference.

 

thats pretty much what the SUBARU mechanic said and had done to his wrx classic and with no problems in 18 months, he said it will not damage your car as the ecu will make allowences for extra fuelling especially the ppp.

 

unless it's a jap import of course

 

his is a UK but I can't knock what you say ref JDM

 

true

 

Essential... probably not, necessary... absolutely.

 

so then are we coming to a agreement that if: its not mapped after it will be ok but to unlock the full potential mapping post decat is the way forward(and forward slightly quicker lol.).

 

There's always this kind of question when modding... a fuel pump for example, is it essential to upgrade? A lot of people say not, the majority buy to be on the safe side. With a remap you are making sure you car will be running ok after modifying, whilst also getting the most out of it.

You pays your money, you take your chances.

 

it would be better re mapped but doubt it will do any harm if you dont.


I would strongly recommend a remap though its unlocked alot of power in my car!

 

6 years and 65k later with a full decat (no remap) and my old P1 is still going strong.

 

You dont need to decat the car as the car already has a sports cat fitted which flows as good as a decat anyway (plus keeps your emissions in check ) there are lots of posts on here about this on a ppp car and replies from prodrive who tested the cat saying that there is no improvement in performance by decatting the car (removing the sports cat).

Tony

 

 

As Tony says the PPP sports cat is pretty free flowing and there will be little to gain from replacing it with a de-cat item

Shaun

 

To risky without monitoring IMO. Good chance you will get overboost , boost spikes and possibly run lean. Plus pointless unless mapping to get the most out of it IMO.

 

not neccessary, however to take advantage of the benefits then a remap would be best but as said not neccessary.

 

It seems the debate on this is similar to the one on smoking.

Most smokers know someone or had a granny that smoked 40 tabs a day and lived until they were 90 but the fact is it is still risky.

Same with this. In theory, you could get away with it for a long time but at the same time you are risking boost spikes etc. If you don't have it done and something goes wrong you'll kick yourself. If you get it done (better performance and fuel economy) and nothing happens you'll never know if you'd have got away with it or not.

Up to you. Persoanlly i stayed off boost until i had it mapped. Got bigger/better intercooler hoses and de-resonated centre, centre cat pipe and a back box and she's making 273bhp and the same torque.

5t.

EDIT JGM (below) makes a good point. Mine's an 03 WRX and i was told boost spikes are an issue with no cat.

 

a lot of people here posting with regard to the classic shape...

you often find the newage sti will boost spike once decatted. the sports cat is more restrictive than no cat especually with regard to spool and boost spikes.

you would be wise to get it checked with detcans and gain much more from the car with a remap, not just more power but more response and drivability.

Simon

 

what in the name of jesus is a BOOST SPIKE and how bad are they, because they dont sound great. As regarding the ppp cat i still thought no cat was better than any sort of cat be it normal or a sports one.?

 

I once fitted a decatted up-pipe to my old bugeye WRX. One cold night on the motorway I found my boost had now raised from the mapped 1.2 bar to about 1.3/1.4 and it was spiking. Thats obviously bad as I didnt know if there was enough fuel in there for a start, but driving with a spike is not good anyhow.
My temporary solution was a Dawes device to bring it back to 1.2, but then I sold the car on before I could map it

 

Basically with a turbo car you need a bit of back pressure in the exhaust system to help control the turbo and stop it over boosting. The pressure coming back in the exhaust acts as a brake on the turbo.

With an NA engine you want the exhaust gas out of there as fast as possible but turbo cars sometimes need a bit of a restriction. A good example is the Supra MKIV which needs restrictor rings fitting the the exhaust if it is decatted to re-create the back pressure you've just taken away.

The ECU should be able to control everything in a scoob and dtop this kind of thing happening - however, without a remap the ECU is unaware of the decat and what you can get - driving hard is a short period of overboost before the ECU can correct it it. The sports cat provides that back pressure and keeps it a bit safer so you are mixing up your NA and turbo cars thinking a decat works best.

As discovered above a decat without mapping raises the boost pressure. This overboost or 'boost spike' isn't a good thing for your turbo and therfore your engine.

What a decat does do is allow the mapper to fiddle with the fueling a little easier without worrying about destroying the cat. Mine is running a bit richer at the to end as it needs extra fuel to keep the up/down pipe cats intact.

Does that make sense? It is very much laymans terms so not totally accurate but should give you an idea.

I had mine mapped by one of the best guys in the country and he said boost spikes were a very real problem. He did say 9 times out of 10 you will be ok but personally, i didn't want to be that one and risk several grand of engine work for the £500 mapping fee.

5t.

 

Have ran several Classics and Bugeyes de-catted without any issues what so ever, i then had my bugeye mapped 12 months after it was de-catted and yes it was better but not in the same league as when i fitted the full Scoobysport exhaust to it when it was 6 months old.

The car was transformed when the complete exhaust was changed and ran fine with no boost spikes at all.

Ecutek just enhanced things a little further.

 

I'm having the same dilemma, got a full decat going on my classic but no funds for a remap yet, I wont feel safe putting the foot down ,at track days and quarter miles of coarse.

 

fivetide and zippy, very helpfull thanks. at the mo i have the full prodrive system and was thinking of taking off the prodrive cat and replacing that with a 3" decat but keeping the rest of the system intact, i was going to opt for either a scoobysport one or a H+S decat both are roughly same cost, but saying that im told the prodrive backbox can be restrictive?.