Category Archives: Misc.

Misc.

Running out of breath

Falling on it’s face…  dying up top.   Words to describe how some turbocharger is inadequate in the view of the person commenting on the turbochargers performance.

turbo_comp_map_compareShown above are sections of the compressor maps from three popular turbo compressors in use on the Audi B5 S4.  This section is the top right corner of the map.  What I am trying to illustrate is the difference between a turbocharger that dies up top, runs out of breath, and falls on its face, compared to a turbocharger that does not.

See the difference?  Notice how the one turbocharger compressor does not have a drop in volumetric flow rate at the maximum speedline PR even as the flow rate continues to increase?  (PR is the vertical axis and flow rate is the horizontal axis.)  No?  You don’t see that? Neither do I, in fact all the compressor wheels show that with increasing flow rate the pressure ratio declines, and by a certain flow rate that PR drops quickly, as the turbo ‘falls on its face’.

So what’s behind this phrase that gets thrown around?  It’s a description for a result that any compressor wheel eventually reaches, a point where in order to try and increase flow rate through the compressor requires a drop in the PR.  Where you will find the phrase being used is in a comparison that pits a large compressor wheel against a smaller wheel, one where it should be quite apparent the larger wheel should be capable of flowing a greater volume of air, beyond what the smaller wheel is capable of, up to the point where the larger wheel also falls on its face, dies up top, and runs out of breath, just like the smaller wheel does.

If you have not figured out which map belongs to what turbocharger, the top is for the K04, middle the K03, and bottom the RS6.

Misc., Testing

PTP Turbo Blanket

My first foray into the market of turbocharger blankets was with the PTP Turbo Blanket intended for use on my Audi S4’s BorgWarner K03 turbochargers.

PTP Turbo Blanket

I figured that the turbine housing of the K03 was probably not significantly different than that other turbochargers I might soon consider using, BorgWarner K04’s, FrankenTurbo F21’s, SRM RS4 Hybrid, ProjectB5 RS4-X, etc, since all used the K04 hotside so that if I were to upgrade I might be able to reuse the PTP Turbo Blanket

After measuring the circumference around the turbine housing of the K03’s and a set of K04’s I found that they only differed by approximately 0.75″ which I believe is sufficiently close to not matter to how the turbocharger blanket performs.

Unfortunately the turbocharger blanket model I selected was not a good fit with the K03’s on the S4, more specifically in the area where the exhaust manifold attaches to the turbine housing.  After monkeying around with trying to get the blanket to fit I decided that major surgery, such as cutting the blanket to get it to fit, was out of the question and I would  return the model I had selected to PTP Turbo Blanket and investigate other models that they carry.

I also inquired with PTP Turbo about a custom blanket, which is something they offer, but they advised me that to produce a blanket for a single vehicle the cost would probably be unreasonable.

At this point I decided to expand my search to other product suppliers to see if another might carry something better suited to the BorgWarner K03’s.

 

Engine, Misc.

6th engine pull

Getting ahead of the game, I’ve got plans to put some different turbochargers in the car but at the moment haven’t established exactly what they’ll look like.  The motor is coming out so I can work on a few accessories and swap exhaust manifolds then hopefully within a couple of weeks will have a different set of turbochargers to evaluate.

audi b5 s4 engine pull
6th time the motor has come out of my S4

A lesson learned from this time around, figure out how you are going to plug the braided stainless slave cylinder line BEFORE you install the product.  I wanted to leave the metal slave cylinder in place since I had put some RTV around the housing to keep dust from getting into the bell housing around the slave cylinder.  This meant disconnecting the AN fitting that goes to the metal slave cylinder.  With the stock unit I had a small tube that would slide over the end to plug it when disconnected, not so with this AN fitting.  After disconnecting the fitting and not having any luck holding the line up to keep the fluid in, or being able to find a suitable plug, I let the end of the line drain into a waste container.  Next time around I’ll have a proper plug to put on the end of the line.