Technical 1.9 JTD, weird engine noises >2200rpm

[Yiiiiieeeeehaw]

Hi,
I there's something strange going on with my MK2 1.9 JTD: It makes a weird ticking ('frrrrrrr') noise during acceleration starting at around 2200rpm that gets louder the more the accelerator is depressed. Also the gas mileage goes down significantly (22 to 17km/l), instantly, as soon as one goes above 60mph in the highest gear.

I've replaced the injector seals, so that's unlikely to be the problem.

Does anyone have an idea what that might be? Lower turbo hose should be a whooosh, not a frrrrr noise but the rpm range in which this appears is somewhat related to the boost pressure.

Edit: The ticking starts there:

 

[Yiiiiieeeeehaw]

It's starting at about 1650mbar of pressure in the intake rather than rpm dependant.

Turbo hose, maybe?

 

[Yiiiiieeeeehaw]

I've made some progress here: It starts as soon as the overboost solenoid opens, and is a pft-pft-pft about 40% of the time which coincides with 40% opening of the solenoid. When removing the plug from the valve, the noise is gone. It should fail open and run the turbo with maximum boost in that case, so all other components should be OK.

I did replace the hoses on the thing but the pft-pft-pft is still there. Is it possible to bench-test the solenoid itself?

 

[Yiiiiieeeeehaw]

I found the problem.

Some cheapskate welded an oval rear silencer (1.2 gasoline) onto the center pipe, instead of the breadbox-type for the 1.9 JTD and 1.8 HGT. The back pressure off it is so high that the engine consumes 0.5-1L more per 100km and the wastegate slams shut during overboost (pft-pft noise), without the rear silencer it's a rather light clatter. The problem here was the pressure differential at the wastegate, the pressure from the exhaust was higher than the one from the engine.

 

[flisko]

1.8 hgt and 1.9 jtd got same exhaust?

 

[Ziggy122]

Wow... talk about weird fault and finding something odd

Wouldnt have though a 1.2 8v would cause that much off an issue....

i understand the narrow pipe = higher pressure to keep the same flow

Ziggy

 

[flisko]

Wow... talk about weird fault and finding something odd

Wouldnt have though a 1.2 8v would cause that much off an issue....

i understand the narrow pipe = higher pressure to keep the same flow

Ziggy

he got 1.9jtd

 

[Yiiiiieeeeehaw]

1.8 hgt and 1.9 jtd got same exhaust?

According to MTS, yes. According to Fiat and IMASAF, no. However, the pipe diameter is 50mm on both.

The one I had installed might also be a 1.3 Multijet back box, which is 50mm as well but in the design of the 1.2. Either way, no good.

 

[flisko]

According to MTS, yes. According to Fiat and IMASAF, no. However, the pipe diameter is 50mm on both.

The one I had installed might also be a 1.3 Multijet back box, which is 50mm as well but in the design of the 1.2. Either way, no good.

is just rear box same or whole exhaust?

 

[Yiiiiieeeeehaw]

The chassis.