Tomorrow we will have the last opportunity to test things on the pulling track and as it look for now we will have a good clay track with a load of traction and finding a good balance in tyre pressure and weight distribution. Getting the front of the to far into the air will make the sled dig into the ground a lot more.
On the last test we done we get up in boost pressure and this lowered the EGT a bit.
For tomorrow we changed to a smaller turbine house hoping to get the boost pressure just under 5Bar or 72PSI. Question is will this lower the EGT and move up the AFR or will we get more EGR as a result of more exhaust pressure?
I’m hoping to burn the diesel a bit faster as more intake pressure will get more air volume in the cylinder hoping to get more temperature on the end compression stroke evaporation the diesel a lot faster so with a bit of luck we can ad some more fuel extending the fuel injection.
We also looked into the turbo damage we had so often on the Holset HX60 turbochargers.
We took some damaged HX60 and HX80 and find out they all had damage on the trust bearing indicating there is a lot of stress on them indicating there is a pressure balance problem between the turbine and compressor side.
The smallest model HX80 running with a 27cm2 TH stood out as it was able to bent the trust bearing in to a cone shape indicating there is a lot of tress coming from the turbine site.
The HX60 was a different story as in most cases the run after we hit the surge line of the compressor we where blowing up the turbocharger so our focus also went to the trust bearing suspecting it to flex a lot while hitting the surge line so the compressor wheel could hit the compressor cover throwing it off balance or bending the shaft.
As an engineer the thing to do is start comparing parts form different turbo manufactures to find out why we so far do not having any problem with BorgWarner turbochargers.
The HX80 is the same in size as the S500 from BW. Comparing the trust bearing the BW one is 50% thicker that the one from the HX80 so it will not bent that easy.
The trust bearing from a HX60 has about the same size as the ones from the S400 BW and the material is about the same on the 360 degree trust bearing we use and the original 270 degree BW trust bearing is a bit harder material.
What I did is apply 150Kg force in the trust bearing and took a micrometer to measure how far it will bent and the results where HX60 trust bearing bents 0.23mm and both BW S400 trust bearing bent 0.13mm.