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Discussion Starter #1
Had a cat back powerflow fitted to my 2.0 16v last weekend, have done approx 250 miles since then but it's not performaing as i expect it to.

2 of the 3 silencers have been removed so there's just the rear box, i thought this would have reduced back pressure but the car seems to act like back pressure has been increased, low down the car revs freer and has more power, especially from 2k revs but struggles above 6k. This doesn't make sense to me as i thought the reverse would happen, any thoughts?
(It also rattles like mad above 6k but not sure yet if this is the exhaust or the car, or a heat shield etc.)

I've read on here that the ECU can 'learn' new settings when the engine spec changes, but don't know any spcifics about this.
Is it possible the the ECU has reprogrammed itself to run with the previous blown exhaust and is not performing correctly with the new exhaust.
Does anyone know how the ECU reprograms itself?

Cheers in advance :)
 
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Discussion Starter #2
I think if you disconnect the battery for a number of hours the ECU will reset to its standard original settings. Then it will learn the new setup.
 

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Yes, this made an improvement when I replaced the exhaust on my Boxer.
The ECU re-learns the new reading and re-maps it.
 
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Discussion Starter #4
The ECU will not be able to adjust to suit the exhaust at its best as these boxes of tricks have a very small window of adjustment designed in them.

The midrange has improved because of the reduced exhaust backpressure however it might just be that it is subjective that the car isn't performing worse at high revs because of the fact that it is now pulling further down.

The only way you will improve things is by fitting a BMC (or similar) panel filter and get a chip fitted and calibrated on a rolling road by a reputable company.

The rattle you are experiencing is most brobably the new exhaust system rubbing against somewhere. If this only occurs when the engine is warm it is most likely to be one of the hanger brackets (these slide into the rubber mounts). You must bear in mind that exhaust systems can extend up to 50mm in length when hot; I would check that the mounts on the rear muffler are not rubbing against the chassis as this is usually the most recurring problem. You might find that your new muffler has two sets of hanger brackets to suit pre and post '95 cars as Alfa changed the design of the rear exhaust mount and chassis bracket. You therefore might want to consider angle grinding off the redundant brackets and shorteting the remaining pair by 10mm. Do round the edges off when you're fininshed or else you will split the rubber mounts when it's time to fit the muffler back in place.

Hope this helps,

T.
 
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Discussion Starter #5
when i had my powerflow exhaust fitted it knocked on the rear suspension beam when hot and when starting it did the same thing. just take it back they will heat it up and give that extra bit of clearance :) a
 
M

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Discussion Starter #6
Ta for your responses, disconnected the battery terminals for 5 hours today and will see how it drives tomorrow.
Taz, a chip is a little way down my list of things to fit but will get one eventually. In the meantime i'll look at getting a filter to help things.
I don't think it's subjective, the car definately stops pulling as hard above 6k, but i did wonder about that myself, the noise alone has changed how the car feels.
Difficult to know if the rattling only happens when it's warm as i won't rev the engine hard when it's cold, will get the powerflow agent to have a look at it though.
 
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Discussion Starter #7
Fitting an air filter will just make it worse won't it? Need to sort the engine management out first...
 

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BTW 30 mins is enough to reset your ECU, I beleive.

Have you considered that the problem at very high revs may be fuel starvation now you have a more efficient breating system? I presume that you have a replacement aftermarket panel filter.

Rattling from a 155 exaust! Never :D :D

chris
 
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Discussion Starter #9
To check for rattles,

Get the engine warmed up by going for a drive down a dual carriage way for 10 to 15min driving it fairly hard (water temp to reach 90deg C). Stop somewhere sensible and have a look at the exhaust and its mounting points; the rubbing of the exhaust against chassis points will be obvious. To help matters you could get a friend to rev the engine while you're having a look.

It does take a while to get used to the new driving characteristics however I would not worry about fuel starvation unless you have a particularly old fuel filter, say more than 2 years old (lines do not generally get clogged up that easily however you may want to purchase a fuel system cleaner additive to give you peace of mind - I recommend Wynn's products). If you have been running nasty fuel e.g. Tesco's etc you may have poor fuel atomisation in the injectors due to a build up of "gunk"; the system flush may help although if it is bad you may have to get them ultrasonically cleaned by a professional (ASNU representative). The fuel pump is good up to 170hp so I would not worry about this as the exhaust may just give you 5 to 8 extra hp when optimised on the rolling road.

An air filter may be a good idea and don't worry about the chip; this is really to finish things off and bring all of your engine mods to work in the most efficient manner.

If you want to get the ECU to re-learn parameters you should have a look at the workshop manual to see how it can be re-set, alternatively ask a friendly dealer for advice.

Taz.
 
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Discussion Starter #10
slow pick up from low rpm when you've removed 2/3 silencers could be because you've also reduced torque by removing all the back pressure. You _may_ get the power back higher up the rev range where the engine can breath more easily.

BHP turns heads, torque turns wheels ;)

Still, a freer flowing air filter would sound like a good plan - should remove any restrictions in the intake & allow the car to develop a a little more power to overcome the low end losses... a chip will defo sort it as it can be mapped to take all of this into account.

A
 
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Discussion Starter #11
fade2grey said:
BHP turns heads, torque turns wheels ;)
A
Funny, I've seen this used in defence of diesels...you turning to the dark side Alex?? ;)

wrinx
 
M

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Discussion Starter #12
Resetting the ECU has solved the problem :)
The car now revs freely round to 7k as it did before, but seems to breathe better through the whole rev range which is exactly what i was expecting from the new exhaust. So i'm happy.
Wasn't expecting any major changes so was suprised the car behaved as it did. If anything i'd say that before the ECU reset the car performed as if the timing was advanced by couple of degrees, lots of power at low revs but struggling at higher revs. And a slightly high idle speed.

Still got a slight rattle going from 6-7k but nowhere near as bad as before, will follow your advice to figure it out Taz.

Fade, i agree about the BHP turning heads thing, although the noise from pipes where two silencers should be also turns heads ;) I was expecting to get what you described but ended up getting more power low down and less higher up.

I had the exhaust fitted now without any other mods as the last exhaust needed replacing for the MOT, so it's in preparation for more engine mods at a later stage. Will definately be getting a new air filter and chip, but trying to work out whether to go for more serious mods as well or just put the money towards a Scooby. Modding the engine is a slippery (and expensive) slope... :D
Handy to know the fuel pump is ok up to 170bhp, i'm hoping that if i just add a filter/chip nothing else will need uprating.

But before all that... i'm gonna play with the handling :)
 
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Discussion Starter #13
MT - top stuf, it's always something simple aint it! :)

Wrinx... no way, densils may be the way to go eventually but I'll live with 2.7 liters of twin turbo petrol for the mo ;) - speaking of which, anyone wanna buy the Uber Audi in the emmigration sale? :)

A
 

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I'm glad you have sorted it MT. I am always skeptical with custom exhausts as they should be made using a flow bench to get the optimum pressures etc. I once lost over 50 bhp from a 155 due to a custom exhaust!!! Now I'm on Supersprint and Remus and relatively happy.

If it sounds loud now, just wait till you get the filter. If you wanna know what a K&N sounds like, just take the top off your air box and go for a short run up the road. They sound a lot louder when the engine is under load as opposed to standing still.
 
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Discussion Starter #15
Simple suits me fine Fade :D
Blimey Henry, that 50bhp loss sounds extreme! What was the mistake that caused that?
Looks like i took a bigger risk than i realised, and have got away with it *crosses fingers*.
Have had K&Ns before so know what you mean about the noise, had a P4 with a straightthrough pipe instead of the rear box, and could hear the K&N induction noise above that! Will prolly just be going for a panel filter but maybe a BMC Cda thingie if i do mod the engine properly.
 

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Hello ppl, im gonna be getting a powerflow fitted to my 2.0 TS soon too, was just wondering how much it cost ya, i got a quote for £330 from cat back? Also when you disconnected your battery to reset the ECU, do you have to...(or is it a wise idea to).... disable the alarm and immobiliser from in the glove box to stop to stop any problems? ....cause they are a bit temperamental the alfa alarms aint they :) :D
 
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Discussion Starter #17
I feel i paid well over the odds for mine, £400, but i made the mistake of telling em i needed it had just failed the MOT and i needed it for the retest :rolleyes:
Marlon paid £300 for his and got a de-cat pipe too, maybe i shoulda gone to Scotland.
 

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I think I'l make my own de-CAT pipe as I have loads of left-over stuff from the last 4 exhaust changes! None of the dealers around here will touch a de-CAT pipe...
 

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OK, I'm thinking of doing a bit of work on my car in this area, so could I have advice about the following?

1) I want to clean out my K&N panel filter, but I've lost the destructions, does anyone know offhand how to go about doing this?
2)While I'm doing that, thought I might as well let the ECU reset - disconnecting the battery: just positive terminal? Pos then neg? Neg then pos?

Cheers me dears.
 
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