Thread: Td5 wastegate

Originally Posted by OffTrack

I think the reason why higher exhaust temps help the Turbo perform better is to do with gas velocity. Gases become denser as they become cooler, so the pressure and velocity of the exhaust gases drops.

Ideally you want to keep the gases hot, without being excessive, so the energy in the exhaust gas is used to spin the turbo, rather than heating up the exhaust manifold and engine bay. This is the primary reason ceramic coating is used on performance manifolds - the coating on the inside of the runners helps stop heat leaching from the exhaust gas into the manifold. The fact that it reduces the tendency of the manifold to warp is a secondary benefit. If you were really keen you could also ceramic coat the exhaust side of the turbo.

I'd probably go for a Nanocom over a boost gauge TBH. Boost level is a "fun to watch" parameter but once the wastegate is set there isn't much point keeping an eye on it.

I finally got around to tweaking the wastegate last night. I haven't had a chance to really test that I have set it properly, but on a short backstreet blast the boost peaked at 1.255bar/18psi. It's certainly made the D2 feel a bit more zippy.

And after rereading the PLX Devices page the DM-6 gauge doesn't have pc logging. You have to fork out an extra $100+ for the OBDII gauges to get that feature.

Indeed it is.
Higher temperatures give the gas pulses far more strength (and velocity) compared to the average manifold pressure. This extra energy drives the turbine better with a lower measured drive pressure.

EGT gauges are only really needed on an EFI diesel during tuning and to check if anything goes wrong. Unlike a mechanical diesel which can't tell if air density is down at altitude and gives it full fuel anyway.
A well tuned EFI diesel protects itself through A/F ratios to keep EGT's within safe limits.

I know this is an old topic and I've read it with interest, but where do people stand on bypassing the wastegate control valve on a D2a, Ive read in some places that this is a good idea, and will give increased performance, but if I understand the operation of the wastegate valve I can only see that this will reduce boost pressure and performance