Everything I ever needed to know about Volvo turbos

Really useful video. If only I had seen this earlier!



Basically explaining how the wastegate works on a volvo turbo charger and how the boost control system works. Yeah, I know a bit dull.

Water cooled turbo, now water cooled

I don't think I am going to win any prizes for my headline writing, but.

I've added water cooling to the turbo. My turbo bike buddies always talk about how they don't bother with water cooling. But in their installs the turbo sits right at the front in serious airflow. In my case the turbo is hidden from this airflow in the engine bay.

When I did the rebuild some of the oil was rather nasty. Sort of black and gloopy. I assume this is from heat damage. So adding a few water cooling pipes seems to make good sense. I had a few small leaks, but I think that I have now addressed them.

Pretty much time for an oil and filter change and then a test-drive.

Look at my fancy crankshaft (ooh eer)

Not sure whether I mentioned it, but the engine developed a water leak into the oil.

I ignored this for a while hoping it would go away, but once the oil-overflow bottle was actually full of "mayonaisse" I realised that it was time to act.

Turns out the top of the barrels had a nick on them. I did actually know about this when I put the engine together, but my local engine folk didn't have the tooling to sort it (aluminium with steel liners is to difficult for them) so I had hoped it would be fine (and it was for 200miles). Anyway, I found a new place (Paynes in Eynsham) who sorted out the barrels (quick service, very professional too and didn't treat me like an idiot, which is polite).

Here is a photo of the rather interesting crank and con-rods on my existing engine. There have been trimmed down a bit, with the counterweights seriously attacked, and the rods look like they have been shot peened or sintered or something (these are not the normal castings that I have on the other engines). Note also the residual anti-freeze from the water leak (oops).

I also discovered that I had forgotten to install a cam chain guide, so it was good to get the engine opened up.

When rebuilding the engine I reset the cams aiming for stock on inlet and 5deg advanced on the exhaust. This is supposed to give best power on turbo suzuki's, although I need to measure it more precisely to get it right.

Turbo porting, fast and furious

So, I had a problem with my turbo overboosting. Basically this means that even with the wastegate wide open the boost still builds so it is out of control.

This is not a good thing, because too much boost can result in engine damage.

I had temporarily addressed this by installing a exhaust dB killer (a device that reduces the noise a bit by constricting the exhaust at the outlet). This results in slightly higher pressure in the exhaust and it is the pressure difference between the two different sides of the exhaust turbine that provides the drive to the turbo.

Anyway, that was a short-term solution and did work, but it isn't ideal. The whole point of turbos is to get lots of boost and lots of boost when you want it. Decreasing the efficiency of the turbo would (in theory anyway) make boost come in later and generally make things more laggy.

So, I hit the internet and discovered that I needed to make the wastegate more efficient. This is done not by changing the wastegate, but buy making it easier for the gases to whip through the hole. As expected the casting was crude, so my die-grinder, a carbide bit and 20minutes was all that was needed to open up the flow paths so as to allow the gas flow to more easily get through the wastegate (when it is open).

Here are a couple of photos, post port (none before, sorry).

I opened the flow path, removed the sharp corners, and also increased the diameter of the wastegate hole (by maybe 1 or 2 mm).

It will be interesting to see whether this sorts out the problem.