ECU worry
 

Hi. I could do with some advice regarding my ECU. I'll start with my spec:

1998 Impreza Turbo Terzo with PPP (ECU, RamAir panel filter, suspension and back box) - spec when purchased in 2004.
TSL decat downpipe and cente section - added later around 2008.

Last year, my brother diagnosed a potential bottom end failure about to happen, so I took it off the road to prevent further damage and have not driven it since. After weighing up my options, I managed to get hold of a low mileage bottom end from a WRX300 and my brother and I are currently building up a new engine. After reading many threads on here regarding ECU remapping, I'm now wondering if the bottom end fault is a result of adding the decat, as I didn't remap after adding it (mainly due to cost of a new ECU). Splitpin on here mentioned that there was a potential for overboost with PPP and decat systems. Is there any chance that the two are related?

Also worth mentioning I think is the fact that I work 6 miles from home with a short journey down the motorway to get there. I don't think that the short journeys did it any good, potentially not giving the engine time to sufficiently warm up, although I did my best not to use boost during these journeys, keeping the revs under 3000.

I would appreciate any and all advice. Thanks.

Steve

Not sure if oil may be a contributing factor to the above. I've been using Mobil 1 0W 40 since I got the car in 2004. Anyone?

Steve

I would say that the 0/40 oil is too thin for an Impreza engine - you're better off with a 10/40, 10/50 or 15/50 IMO

It would be worth fitting an aftermarket ecu to run your replacement engine, and getting it custom mapped to your engine/mods. - Typically when decatting a standardish car, you'll find that the motor will tolerate slightly less ignition timing during turbo spoolup - If you were getting a bit of detonation, this may well have been a contributing factor to your previous engine's demise.

If you're planning to stick with the standard PPP ecu, it would be well advised to check with wideband lambda and det cans.

Thanks for replying fiestaboy. I'll be honest and say I'm not very well versed in engines in general. In the past 5 years of Scooby ownership, the car has felt fine whenever I've driven it. It pulled well and drove smoothly. What are the tell-tale symptons of detonation and it's effects? Is it one of those "you'll know it when it happens" things?

Thanks.

Steve

Unless detonation is really severe, you won't hear it whilst driving the car. If you can hear it, it won't be long before your motor 'grenades' itself into pieces ;)

You need a set of det. cans, bolted to the block. - There are electrontic varieties which consist of a knocksensor + control box and headphones, or more basic DIY constructions using ear defenders, fuel hose and a length of copper pipe.

Typically, you can see the signs of light detonation as 'sandblasting' to the sparkplug tips and/or corners of the piston crown.

If you see a car detting on the dyno, you will notice a short, sharp puff of black smoke from the tailpipe, as the event occurs.

The combustion pressure can be increased several times by the uncontrolled explosive burn of a detonation event, as the piston is nearly stationary around TDC - This 'shock' obviously transfers pressure through the piston, conrod and bigend bearing, and can lead to premature failiure of the bearing or piston

Many thanks for your advice. I will be looking into checking for knock when we've rebuilt the engine. I think that for peace of mind at the very least I should look into a remap, possibly a Simtek ECU, and ditch the PPP. £1000 seems like a lot of money, but I guess that a smoother and overall more reliable engine with less chance of exploding is worth the outlay in the long run. ;) Is 270-280 bhp a good estimate with my spec?

Steve

Plus, I'm adding a grounding kit, RCM Cool Panel and intercooler lift kit. Negligible improvements by themselves, but may add up to an overall improvement. Anyone?

Steve