RRH

From experience of Bug and Blob, it is decatting the downpipe that seems to cause the spikes- I'm guessing that maybe the boost overshoots as it builds up quite a lot quicker?

A certain 'mapper' induced such massive spikes when he ecutek'd my last MY03 wagon that I had to damp the spikes with a Dawes as 'he didn't have time to come back and sort it (after two failed attempts).

Funny, as Richard Bulmer sorted it first time, stopped it running like an overfuelling sack of sh it, and made it fly.

It was spiking slightly when I replaced the downpipe (was ok with just centres and backbox) before it was mapped.

hades

Some people don't find significant boost spike issues with the TD04 engined cars, as far as I can tell. The car which had the really dangerous boost spike issues if you changed the downpipe was the 2002 STi (and onwards I expect). It is possible to overcome the boost spikes without a remap. No-where near as nice a solution but changing the boost control restrictor or properly fitting a Dawes device or similar could get round the engine damage due to boost spiking issue.

I ran my 02WRX with full exhaust change (sports cat admittedly) for a short time before it was re-mapped, and didn't get any boost spiking issues on the rollers on it's pre-re-mapping run. However, the car was definitely significantly better after the re-map, so I'd always say its worth doing.

hades

P S That's not to say that you can't have boost spike issues with a TD04 car that's decatted and not remapped - if you're not sure, it's always safest to check it out with delta dash or whatever to confirm everything is OK.

R22helipilot

I ran my 03 WRX for a month with a full de-cat (2300 miles) before I had it mapped and had no problems at all. This included the turbo pipe which I fitted myself along with the rest off the system. It runs much better with the new ECU though, get it mapped, well worth the money.

mickywrx

iTrader: (29)

Me AFAIK. MY94 WRX. Revolution downpipe and Magnex from downpipe back was already fitted when I bought it. Had no problems altho it seems like I'll need new coil packs and an up-pipe soon.

Stiver3

My car is running a full decat and i have had no such problems with it (Jdm Sti) I also managed a 40bhp gain on the rollers with the exhaust, and a very slight boost increase. So no need for a remap for me.

scoobimax

Sorry Chap - I haven't a clue about the part numbers. De-cat centre section will either be just a pipe or if a bulge in it , may be a resonator. Don't know what the difference in size between resonator or cat is.

Magnex web site might help.

Max

scoobimax

I know you're on about a MY04 wagon but unfortunately I am one of those who doesn't fully know how their car works, which is why I asked the question about my own situation. I asumed similar problems would be there.

Sideways, the way forward

defo advise a re-map when de-cat in place, it changes the air flow totally and the ecu needs to be made aware of this to conpensate fuel wise. Once you get it mapped, essentially you have paid for the mapping software and if you were wanting to map again after that it would cost little or nothing (if done by the same mapper).

mattdoyle

Thought this one would run and run.

The issue for me is this, I may/may not be keeping the car(going thru a divorce!!!)
If I remap its £750+vat(uppipe fitted prior to map), then if I sell(all 1st time buyers go for 'unmodded cars) I will need to put the old exhaust(and uppipe) and get it remapped(£????).

Guess I will wait until after the financial settlement to see if I can still afford a house, car(and remap). Until then I will run it unmapped, it is slighty overfuelling(soot on backbox), but is immediately saleable.
If there is an issue then there is always my warranty(what decat!!!!!)

scoobfan

I would'nt take it that it's overfueling because you have soot, your car will overfuel on cold start, that's when you get build up.

The only way to be sure it's definately overfueling is by metering.

Rob

mattdoyle

Come on gents, expected a bit more pro's/cons than so far

Turbotits

iTrader: (2)

When i decatted my motor (02sti) it was almost undrivable.The boost spike was so servere it was getting fuel cut so i had no choice to remap and what a difference its made.From my experience i wouldnt de-dat again without a remap.

dj219957

Just had a look at my rolling road graph and my 95 classic with full decat had only a small spike. It rose to 13psi and then dropped off to 12.7 where it should be.
Appears the later cars suffer bigger spikes than this and would agree that spiking has the potential to cause problems - especially if it big enough to hit fuel cut.

andypugh2000

I am in the middle of an experiment ATM,

Full decat, VF28 turbo, IK, Boost controller (1.2 bar)

No remap, no knocklink, std 380cc injectors, std uk 98 map

312 bhp

94k on the clock

Answers on a postcard

dj219957

5...4...3....2...1......





















BANG!

andypugh2000

Well if it was going to go bang surely it would have done by now, been running this spec for 30k now and no problems, kinda throws the rulebook out of the window eh

Oh and when PE put it on their rollers they were so impressed with the torque curve and power they asked who my tuner was

dj219957

Fair play bud. No secrets then. Just loads of boost and a decat eh?

catmeat

When i had a decat on my 01 bugeye i was told it would not need a remap as the ecu was self learning? i dont have the car anymore but had no probs with it.

scooby_matt

Works everytime, too much worrying goes on too often

dj219957

i wouldnt go that far! ive lost an engine and its not nice!

Roojai

Is the VF28 similar to the TD04 in spool up then?

hades

No, the TD04 spools earlier than the VF28 (or VF22/23/29/34/35 etc), I'd say perhaps 300 revs sooner. What that means in terms of running with a standad 98uk map, I'm not sure.

The flip side of the VF28 spooling later, is it's very rare to see 300bhp at PE with a TD04, even with headers, uprated intercoooler etc - I've only ever heard of one non hybrid TD04 car that made 312bhp there, running a very aggressive map etc.

fallwood

Bugeye my01 full magnex decat including uppipe, superchip (flame on) , k&n panel filter,greddy profec b spec II ECB, standard pump/injectors/map, 310bhp, fueling is spot on and has been running like this for nearly a year.

pauld37

Me too, MY01 bugeye full decat, no problems

fallwood

Just a recap, strangely enough I was booked in for a dyno run this morning to see if everything was still running ok (have it checked every year) so here's what was said. Running 19psi under WOT fueling was showing 8.5 -8.7 which apparently is well within the limits (7.5 being borderline/dangerous), showed 303 bhp but intake temps were higher than my last run (in winter) which would account for the higher bhp figures I got on my last run (310bhp). Had an indepth discussion about the dangers of not having a remap and was told "if the fuelings ok then you should have no problems at all, people only tend to get problems when they start to get silly with the boost without having the fuelling checked, if you leave it as it is now it should run fine.". So there you have it 303 bhp without a remap and according to my tuning guy completely safe.

New_scooby_04

iTrader: (4)

Funny enough, I was talking a couple of VERY well respected mappers recently about re-mapping a MY99 (not a new-age car where the response may have been very different). I mentioned that it would be good financially if I could put the decat on then run it for a while whilst putting the money aside for the remap, and asked if this was safe. Their responses was pretty much the same: MY99s on SUL should run a Decat without issue, but there are one or two cars where a decat takes them outside of tolerances and -therefore- it's wise to fit a knocklink to keep an eye on things.

That's what I'll be doing then...better safe than sorry!

NS04

scooby_matt

Just what I was wanting to know

scoobimax

me too!