Engine Flow Chart (and compressor maps)

[JoeWagon]

Yesterday when I was reading this writeup on engine flow charts and compressor maps, I was wondering if anyone can find an engine flow chart of a 4G63. You'll know what I mean when you go there. Link is at the bottom.

this is for a VG30DETT


and what I'm looking for is the overlay as done here:


Thanks for the help, here is the rest of the site. http://cherrypicker.tripod.com/turbo...0dett/id7.html

[kjewer1]

I dont care much for the way he goes abou this. For a couple reasons. One is that I hate CFM. It says nothing for fuel requirements, HP, etc, as it stands. You have to know (or use standard) pressure and temp to get mass. Two, when you overlay the airflow through the motor, it looks nothing like those charts do. The left line is pressure ratio, or boost. So as you plot airflow on that chart once you hit peak boost the line will turn to the right and stay flat across until the end of the gear. It doesnt go up in a striaght line like that. Not a very good visual representation of what actually happens IMO. Also, how much air you move through the motor at a given rpm depends on boost pressure as well, so you need to have that first. You can get away without it in CFM since CFM is a volume measurement and not a mass measurement, but that brings me back to the first reason I dislike those charts

Check out www.stealth316.com, tech section, compressor flow maps. Same motor, much more useful plots. Awesome info there too for those ready to get into this stuff.

In my personal humble opinion, all this math doesnt really mean a whole lot in the real world. Its only good for illustrating the general theories by which these things work. We use turbos that are WAY too big according to all of the math. I think the turbo I am going to next is spec'ed for a 6 liter motor, lol. Its much better to look at what turbo setups actually work well, and if you need to make adjustments use the theories and rules of thumb learned by going through the math and charts.

[JoeWagon]

Muchos Gracias,

too bad it all doesn't work out according to theory... and it would have been neat to run the most efficient turbo by number down the track to impress people when there are T66' or whatever flowing all the air right out of the wastegate at half boost.

Anyway, so is 'compressor surge' on a map the same as when the wastegate opens?

[kjewer1]

Not really. True compressor surge, as in to the left of the surge line, only happens at WOT or close enough to it to be building too much boost at too low airflow. Most of what people call compressor surge is just the BOV fluttering. I believe it was FP that called it "internet surge," LMAO. If you have ever heard a car with no BOV let off, that is more like the rear surge. In that case the effect is similar, though the means to the end are quite different.

The problem with running the "most efficient turbo" is there are two ways to look at it. For maximum compressor efficiency one would run a wheel much larger than you would actually need. For the best time relative to turbo size, you would run an undersized turbo. Like Leon R. running 11.8 on a 14b.

[kjewer1]

You know what I could do though... I could output a log in dSMlink to Ecel and graph flow vs rpm vs boost, from runs at various boost settings. From that we could come up with a true measured (not calculated) airflow "map" of the 4g63, and the corresponding VE curve... Interesting. Could do the same for the 2.3 liter and compare.

[JoeWagon]

If it's not too hard to upload, it would definately be something interesting to look at.