gr1

due to my downpipe starting to blow,im going to fit a de catted downpie as a replacement.Do i need to have a remap done or will it be ok to run without a remap...

also,should i wrap the new downpipe or leave as is?

car is MY 95 STI 2 always run on v-power/optimax usually with octane booster and is pretty standard(e.g. no great performance mods)

thanks in advance for any imput

cheers
Graham

badgerface123

im running a de-cat downpipe without a remap no probs can still remember the day i fitted and the drive home
but it is safer to remap with mods like this and possible get even more power/torque with the remap+exhaust

gr1

cheers for reply

dont really want to go to expense of remapping unless its going to do long term damage..i'm happy(ish) with the power its already got.

what about the wrapping of DP.

anyone got any thoughts

cheers

R4LLY

iTrader: (1)

Once a decat is fitted a remap is strongly recommended.
The boost levels will automatically increase due to the amount of air flow increasing, this will automatically cause the car to run lean at times, which in turn will melt a piston..

So don't leave it to chance, get it safe and more power while your at it. There are lot's of Impreza's with decat's and other mods driving around without remaps however it's not a question of "if" but "when".

The standard ECU is not capable of changing the parameters that it has been set to from the factory so any modification which can alter fuelling/boost etc.. will cause problems.

This is one of the reasons that so many Impreza's blow up and why the Impreza has the reputation of having "chocolate" pistons, as sometimes people tend not to understand what sort of damage a "simple" mod like a decat can do without a remap.

gr1

great post R4LLY

given me a lot to think about--will need to sus out the cost of a remap or might put a sports catted DP on it,,i take it you wouldnt need a remap for that
anyone give a ball park figure for a remap

wasnt wanting to splash out too much as i've a lot on just now

cheers

powerwrx

iTrader: (11)

www.jollygreenmonster.co.uk

have a look here mate, different maps and prices are on his site plus simon (jgm) is an excellent mapper.

you will require a remap still even with fitting a sports cat

nerocircus

iTrader: (1)

I questioned this not long ago and was advised by Alyn from AS Performance that the classics should be fine with a decat d/p and no remap. Being somewhat more knowledgeable than me on teh subject , this was enough to put my own mind at rest.
This is the route I've gone down, but deffo will eventually be gettin it remapped to make the most of it, but wanna try and do any other supporting stuff first.

dogpole

on a classic you do not need a remap to run with a decat downpipe.

there are the obvious gains to be had by a remap, but nothing bad can happen if you don't.

Before ecutek was invented, we all ran full decats no problem.

jaytc2003

iTrader: (1)

all though boost levels will increase, it is usually only a spike and not a maintained increase. The car will run leaner but dont forget it is already running very very rich. There is a set boost limit in the ecu in which gives fuel cut and it is this limit that is deemed safe (Subaru would have spent millions on R & D) The ecu is capable of changing parameters although later ecus are far superior (as you would expect from technology advances), the early ecus are quick at retarding ignition etc but slow to move it back (usually requires an ecu reset)



based on what? This is scoobynet scaremongering at its best. thats like saying you put a decat on brand new car. Many years later when it hits 200,000 miles it blows up. Is that down to the decat or just general use?

again another myth. The cars tend to blow up generally through them being mistreated or driven to hard too soon. Obviously there is the exception (as per any other marque), but as I mentioned previously millions upon millions are spent on R & D so they arent going to use "chocolate" for one of the most stressed parts in an engine!!


I do agree about having a remap though to get the best out of the mod, however a remap generally puts a car closer to the edge (especially with aftermarket ecu with no knock control) so are you more likely then to blow up?

Mr Footlong

iTrader: (7)

I knew 2 people over the years that decatted their STI2's and also fitted induction kits (1 GGR kit and 1 Blitz SUS iirc). Within 2 years of doing this they had both destroyed their engines. Full rebuilds required . My STI2 was similarly modded (Full 3" H&S decat, Nur Spec R and a Blitz SUS) but she had an Apexi AFC fitted from the start and had been dialled in by Power Engineering, I simply applied a touch more fuel via the Apexi to the car during cold periods of course. I ran problem-free for 2.5 years but the next owner blew that engine up about 6 months after buying her . That isn't a good record imo and as a result I remapped Fluffy (current beast) after I changed anything that would affect the fuelling or breathing at all. 1 Pat Herborn remap and 2 Bob Rawle : remaps later in the space of 5 months lol.

If you are going to decat and are going to keep your scoob for a while then I would say bite the bullet, bet a few other things to her at the same time and make a remap worthwhile . Have you considered a sport cat? I am running one (modified to 3" exit) and as well as sailing through my MOT's I am running a good dollop of power .

gr1

great replys people...and some very interesting reading...really given me something to think about.
would love to get the map done,but not got the cash for this at the mo..but i do need to get the DP renewed quickly as its already blowing so big decision to make quickly

thanks to all

cheers

scoobynewbie72

iTrader: (1)

Best bet is get the decat fitted and pop along to a rolling road and see what the car is fueling like etc.
hth
Brett

R4LLY

iTrader: (1)

Car's off the boat do not run extremely rich, Apexi's base map is probably what you are thinking of, as the base map on an Apexi runs extremely rich (10 AFR's) before mapping.

Are you sure the Early Classic STI Ecu's really as advanced as that?. They are initially mapped at 100ron in Japan, if they could adapt as you say, then we could run them on 95 ron and the ecu would retard the ignition making them completely safe, however this isn't the case, the car's stay extremely over advanced for 95ron fuel and piston's melt.

With regards to extensive boost levels;

The boost cut is set as an extreme safety feature, and I do stress it is only built in as a last resort to stop the turbo overboosting extremely, i.e 1.7/8 bar....
On the STI's the boost cut limit was set to 1.5 bar, the ECU would only cut the boost at 1.5 bar +. This means that unless your car would attain that level of boost the ECU would not cut in. There is no way you could argue that 1.5 bar on a standard fuelling/turbo setup and unmapped ECU would be safe.
The boost cut was devised as a safety mechanism and a warning device. Warning as your car should never even get close to boost cut, so when it cut's in, it is a warning to get it checked out.
The Safety aspect is; as it would carry on boosting until it blew up without the boost cut.

The R&D was based upon the parameters that STI set. As soon as you fit a decat pipe that R&D goes out the window as they did not and would not account for any modifications.




A new car is not a Classic STI. New modern ECU's can recalibrate for different fuels, different levels of ignition timing, different inlet temps etc...
E.G M car's have such advanced ECU's that running a decat or something similar which will change the fuelling parameters, will have no effect as it will automatically compensate and run rich where it needs to. Which is one of the reasons M engines hardly blow up at all.

Now back to the point,

First let's look at what a decat downpipe does and is designed to do.
It is a free flowing cat free pipe designed to increase the flow of turbo gases and thus increase performance. Now when the flow of gases is increased this results in higher boost levels naturally.
The stock ECU is mapped by STI to run at a certain boost level, and inject a certain amount of fuel at a certain boost level.
Unfortunately the Classic ECU cannot readjust the amount and increase the amount of fuel injected when boost levels are increased.
Even if the Boost cut threshold is 1.5 bar and the car with decat is consistently hitting 1.3 bar (Not hitting Boost-cut) it will be running leaner than it was mapped for, and you would never realise without going on a RR.

Now what you are suggesting is that STI have left enough headroom in their map to compensate for this. However this is not ALWAYS the case. It is also something you cannot estimate without use of an AFR guage or RR.

Which is why there is a case of so many Classic STI's blowing up. Many people take the chance of running without a remap and face the consequences after.


Pistons melt due to Detonation by over advanced ignition timing (Mapped for wrong fuel) or running too lean (Unmapped car)

Bearings/Headgaskets/Rods will go for other reasons such as abuse etc...

One point I would like to make is that "Millions" were spent for the R&D of the STI in the guise that it came in. STI did not spend Millions accounting for people who wished to modify their car or get more power out of it.

The pistons are not "chocolate" from stock, it's just when unfortunate individuals do not research the car's and treat it like any other modern performance car, (eg put any fuel in it or modify the car without any reasearch) that the pistons melt.


[/QUOTE]

Although the aftermarket options do not have knock control the ability of today's mappers is at it's best. The ability of the Apexi in monitoring Knock is often much more effective than Knock Control, as the threshold is catered exactly for your setup.

Many mappers out there map the car to a safer level than the factory and this is shown through their results and many success stories, not just from this forum but outside as well.

What the map does is get the best out of the mods by recalibrating the car to it's new setup, so where STI has spent "millions", you only need to spend a few hundred £ to get an extremely well developed custom map for your car.