Turbocalc Spreadsheet

June 13, 2007, 01:39:12 PM

I was fooling around with Ray Hall's TurboCalc program and noticed the graphs were poorly done. Some of the points were 5-10% off. The TurboCalc applet corrected that but has incorrect charge air temps.

So, I made my own speadsheet. Green cells are for user inputs.
http://www.griffshp.com/belchja/forums/turbocalc2.xls

Anyone have the IHI turbo map handy?

Turbocalc Spreadsheet

Reply #1 – June 14, 2007, 01:01:40 AM

wow!
way over my head, that would have to be explained to me.

I notice you got a v8 plugged into the numbers with one turbo, ill play around with it see what the sheet does.

Turbocalc Spreadsheet

Reply #2 – June 14, 2007, 01:15:52 PM

Well, here are some basic instructions -

1. Enter the bore, stroke and # of cylinders, this will calculate the displacement of the engine.
2. Select 5 point to buttstuffyze your engine at. One point should be around when boost initially occurs (an educated guess) and one should be at peak horsepower (peak turbo flow). The other three should be somewhat evenly space intervals.

Ideally, one would have a data log of mass flow versus rpm for a WOT run to get a more accurate turbo map reading. Since most people don't have that option, the next closest way is to guesstimate the VE and calculate mass flow from that. The TurboCalc software has a mass flow to hp relationship which can be used to find VE if you have reasonable idea about your horspower/torque curve. Is the relationship accurate? I have no clue...I have yet to find a data log of intake mass flow correlated to a dyno run. I think the figure of 10.864 lb/min per hp may be a bit optimistic.

3. Once you have your engine specs dialed in, set your atmospheric and turbo inputs. Most of the inputs are fairly self explanatory.
Finding the compressor efficiency is an iterative manual process. Enter all the other inputs and then go to the turbo you want to use. Find each point and enter the efficiency for that point back in the input deck. If the initial guess wasn't in the ballpark, you may have to go back and forth more than once.

The %Power Gain/Pressure Ratio is sort of an aggregate efficiency. Just because you add 14.7 psi of boost doesn't mean you'll add 100% more power. Compressor/Intercooler efficiency, and intake pumping losses all conspire to rob you of power.

Clear as mud?

Keep in mind that this spreadsheet is just to get you into the ballpark for turbocharger selection. Adding a turbo manifold and the intake plumbing changes the VE of the engine, so the best you can do is just get close. Only when you have the turbo installed can you data log and see how you're doing on the "map".

Turbocalc Spreadsheet

Reply #3 – June 14, 2007, 10:05:06 PM

No Excel..got 123
Also no Turbo