Failure to proceed.... 147 TS

[baldrick]

The Wikipedia stuff was interesting. I wasn't aware that the 147 2.0 TS engine had variable inlet tracts as well as variable inlet cam timing. In isolation having the inlet cam retard in the upper rev ranges seems curious but actually what the quote from Fiat in the Wiki article was saying that as revs rise from idle the cam changes progressively until at peak torque revs, wide open throttle the cam is fully advanced and the inlets are switched to the longer runners. As the engine heads to peak power the engine progresses to the shorter runners. As the TS has quite a soft feeling rev limiter I suspect that the cam retarding after peak power rpm but before the redline is part of the engine control strategy.

With a fly-by-wire throttle informing the ECU which co-ordinates the ignition timing, fuel injection, inlet cam timing and inlet tract length to suit no wonder the TS is such a sweet motor. I get to drive quite a brand new few hire cars in the 1.8 - 2.0 litre range and its surprising how unrefined and flat through the midrange their motors feel compared to my '03 147.

With your TS going doughy in hot weather, I would guess its a more likely a function of the ecu reacting to the knock sensor. Are you using standard unleaded? The combination of hot engine temps, a lean burn engine for fuel economy and emissions reasons and under spec fuel would be enough to cause your problems. Can't see how the ASR system would cause the issue, especially as the its integrated into the ABS system rather than a stand alone system.

Which rubber did you replace with the "rose joint"? And why?

[johnl]

The Wikipedia stuff was interesting. I wasn't aware that the 147 2.0 TS engine had variable inlet tracts as well as variable inlet cam timing.

You can see the variable length intake activating mechanism on the side of the manifold.

In isolation having the inlet cam retard in the upper rev ranges seems curious but actually what the quote from Fiat in the Wiki article was saying that as revs rise from idle the cam changes progressively until at peak torque revs, wide open throttle the cam is fully advanced.....

It's my understanding that the  variator is either activated or it's not, with no in between. I've been wrong before...

.....and the inlets are switched to the longer runners. As the engine heads to peak power the engine progresses to the shorter runners. 

Sorry if the following is obvious. Longer inlet tract works better at lower rpm, shorter at higher rpm. It's to do with the length of time it takes for pressure waves to pass up and down the tract, which always happens at the speed of sound (i.e. the speed of the pressure waves is more or less fixed, though it does vary a bit with temperature). At lower rpm the constant speed pressure waves need a longer distance to travel (in a longer time) in order for a positive pressure pulse to arrive at the inlet valves as the valves open, and at higher rpm a shorter tract length is needed for the positive wave to arrive at the inlet valves as they open. If we were to run just short runners then at lower rpm there would be negative pressure waves arriving at the opening inlet valves (which would hinder cylinder filling), and if we were to just use long runners then this unwanted situation would exist at higher rpm. Using variable length runners is an attempt to have the best of both worlds.

It's very similar to what happens with 'tuned length' primary exhaust pipe tubes (it would be good to have variable length primary pipes in the exhaust, just very hard to engineer...). Of course with the inlet side we want positive pressure waves to arrive as the valves open, and with the exhaust side we want negative pressure waves to arrive.

As the TS has quite a soft feeling rev limiter I suspect that the cam retarding after peak power rpm but before the redline is part of the engine control strategy.

I think I agree. I suspect that switching back to the 'long' induction runners at 5000rpm (or so) acts to discourage the use of particularly high rpm, maybe to decrease the chance of something going 'bang' (?). I certainly don't find any need to use more than a bit more than 5000rpm with this engine, I haven't found any extra power after that...

With your TS going doughy in hot weather, I would guess its a more likely a function of the ecu reacting to the knock sensor. Are you using standard unleaded? The combination of hot engine temps, a lean burn engine for fuel economy and emissions reasons and under spec fuel would be enough to cause your problems. Can't see how the ASR system would cause the issue, especially as the its integrated into the ABS system rather than a stand alone system.

It's crossed my mind that it could be a knock detection issue in hotter weather. I use 95 octane fuel, only. I have tried 98, but the engine seems a bit 'flat' when using it, and doesn't come back 'on song' until most of the 98 has been replaced with 95.

It's also crossed my mind that perhaps there might be a problem with the sensor that measures intake air temperature, i.e. the one incorporated into the air flow meter? If it were to be telling the ECU that the intake air was significantly hotter than it actually is, then perhaps the ECU might 'play it safe' in some ways? I think I'm probably clutching at straws...

Lean burn engine? I'd be very surprised if the A/F ratio were ever significantly lean with this engine. I've been wrong before...

The ASR may be another straw. I can't see why it should have the affect it subjectively seems to be having, yet when I turn ASR off the engine feels much happier, 'fizzier' and more powerful all of the time, instead of only some of the time when the ASR is left on. With ASR off it even sounds better (all the time).

Which rubber did you replace with the "rose joint"? And why?

The engine stay / steady / brace (whatever we call it) at the top of the engine on the right hand side. It has a 'U' shaped fitting at one end, which attaches to a rubber bush that is captive to the engine, and at the other end of the stay there is a soft rubber bush that attaches to a bracket that is bolted to the chassis.

The bush that is captive to the chassis was torn, so that when the stay was removed the inner part of the bush fell out, leaving half the rubber (as a ring) still in position on the engine and half the rubber still attached to the inner crush tube, in my hand. I cut a very short length of thick walled steel tube and forced this into the rubber still remaining on the engine. I then forced the inner crush tube and its' still attched rubber into the ID of the thick walled tube (a fair bit of force, and some rubber grease to get it squeezed in there). This resulted in a bush that is effectively substantially stiffer than it would have been when new.

So, the engine was no longer free to rock back and forth so much as it had been, and this made the drivetrain feel quite a bit more 'connected' to the chassis.  When you get on the throttle the power feels to pass to the wheels more sharply, the car feels more responsive to the throttle.

I thought that I'd like more of that, so decided to delete the soft bush at the other end of the stay, and replace it with a compliance free spherical rod end. This was easy to do; cut off the bushing by cutting the stay tube, then thread the inside of the tube to suit the thread on the (male) rod end. The eye of the rod end is mounted using shims as needed on the chassis mounting bolt.

The result is even more 'direct' connection between engine and chassis, and an even better feeling of 'sharpness' in the power delivery. As a bonus, the more solid connection between engine and chassis causes more sound to be transferred directly into the chassis. I like this because prior to this I found the engine sound rather subdued, but now it sounds rather 'sporting', without the car being embarrasingly boy racer loud from the outside.

I can hear induction noises, I can hear some cam whine, and what I think is probably the gearbox. It's not very loud, but loud enough, and the sounds are nice sounds. If someone tried this and didn't like it, then it could be reversed for the cost of a replacement engine stay...

Regards,
John.