Sorry, I thought that was an instruction

Ipgo,

Cool project I'll read this thread with interest as it progresses.

I think a "blow-off" valve is also known as a 'dump valve' in English (blow off means FART). But I thought the smart turbo already incorporated one? when I do a full throttle acceleration in my smart (also 599cc model) sometimes I can hear this cool sound or something similar. I have to have the windows open to really enjoy it though

Good luck with the project!!

Chris

I don't think a Smart has one for standard (I've never seen a Smart engineroom), it is only sold as aftermarket kit. The sound happens only when you deccelerate (shift gear) not when you accelerate.

Ipgo.

I thought the noise also happened as you changed up, between each gear so that the turbo keeps spinning as the engine revs drop to engage the next forward gear (6 gears in a smart). Usually heard clearly on WRC style Subaru Imprezas as they blast away...

I would look in my smart engine room, but its all so unbelievably crammed in there I couldn't find anything...

(a roadster but engine bay looks the same)

Imagine that sound coming from a 2cv as it burns away - or decellerates, definitely one for youtube when you're finished!

Chris

The chromed pipes don't look original, I thought these where allways from plastic?
Normally a dumpvalve comes with these pipes in a kit so take a good look in your engine bay maybe yours have been modified!!!!



I can't wait either for boosting my 2cv........

Sounds you can hear the turbo to stall because the air speed is slow than the speed of the turbine drive with and it gives turbulence inside the turbo, and it's actually not so good for the turbo if it is run with many revolutions, it is also one of the reasons why there fitted a dump valve on a gasoline car.

Diesel cars have never, since they have no throttle and when no vacuum to open it with, and that the air will not be stopped by a throttle.

But many older and newer small cars with turbo did not dump valve on the small newer because it usually is not so necessary and because they can make the car cheaper

But on a pumped 602ccm engine is used, it is necessary

Not quite so simple as that.

There's two types of blow-off (or bypass) valve. There's recirculating - which release the excess pressire into the intake ducting between air filter and turbo - and atmospheric - which release the pressure out to the atmosphere.

The former is actually the better method, for one main reason - your fuel injection knows how much air is "in the system" - you're not dumping measured air out to atmosphere, so you don't over-fuel.

The only major "benefit" of an atmospheric valve is the noise.

I very much doubt you'll find any half-modern turbocharged car engine without any bypass valve at all - rapid throttle closure from boost will cause the compressor to stall, leading to slow recovery of boost if the driver is back on the throttle quickly - after a gearchange.

Well in my case (Megasquirt ecu) this isn't right. The air is only measured after the throttleplate (butterfly)?. The ecu hasn't any airmass measuring device, it only meausures the air pressure in the inlet manifold. So it doesn't matter the pressured air escapes in free air.

Depends on how the metering's done, of course. On my Saab, the airflow meter is in front of the turbo.

Been a while since I've mucked about with MegaSquirt - the ECU's sat here, probably heading for the Mehari. Is the MAP sensor really the only measurement?

in that case, no, it wouldn't matter if you use atmospheric blow-off rather than a recirculating bypass. It'll just sound like a boy-racer's Saxo...

yep, its the only thing it runs on,
actualy it runs on a copy from Megasquirt called KDFI but it uses the same software (wich is free to download)

Here are all sensors wich are needed (at least)

tps: throttle positioning sensor
ait: air inlet temperature
ct: coolant temperature (in our case 2cv the hot air wich comes from the engine)
map sensor wich measures the pressure in the inlet manifold (with no turbo only vacuum).


I use also a wideband lambda sensor,

See here a little film from my (daily) car running on LPG, yes this is the one the turbo is going in!!!!
http://www.youtube.com/watch?v=_oEY5LSovEI