Also - rule of 10, take the lb/min of air and multiply by 10 - give you a VERY rough estimate of CRANK Horsepower - so 38-44 lb, min of air would be roughly...

Almost 400 at the wheels. YAY!!!!

Crank... U mean?

Maybe I shoulda said, "Very almost 400.....". Speedsource uses 33 h.p. as their driveline loss calculation. I use 40 on a stock flywheel and the rest depends on the 'wheel itself.

Figures I've seen for rotaries are closer to 7.5-8.5. Pistons being 9.5-11.5.

Do you notice a marked difference between the Greddy oil pan and the OEM? I realize it has extra capacity, but I've yet to see anyone claim any real benefit from it aside from the extra tap for a oil drain from the turbo...

Too much math for a rule of thumb..... HE HE HE

You can do it the right way - just takes a bit longer.

See what happens when I folloow your lead, Kane. Now I gotta delete my previous post.

I've seen some of your work. as if the math difference between *10 and *8.5 is going to be THAT much of a challenge for you:eyetwitch

But 1-1.5hp/lb makes a HELL of a difference when talking about ~40-50lbs of air.

Only on RX8 Club can I get called out for being too general on a rule of thumb........

it seems like there is a whole lot more to this map than just that.

hmm, wonder if there is a wikipedia on this

Kane can fill in the blanks if I got it wrong.

I know whats in the second picture.... :)

Can't do much damage with that now can we? Maybe it should be the rule of wrist?:lol:

Why aren't you working, Young Will?

Nope, not really. The graph shows the efficiency of the compressor at the specified Pressure and volume. That's all. If the pressure and/or volume you want to run is not on the graph the turbo won't do it. Or won't do it efficiently enough to be represented.

What Chet is looking for is how that information translates into real world use on the Renesis. That's the connection he is seeking.

Haha. I am...I'm just about to call you ;)

Are you going to do that for the man? Or should I? Or should Kane?

Awesome movie/Quote!

If I did it would only ruin his engine! I am not ashamed to say I don't know everything. I am also not ashamed to say there are guys on this forum far more experienced at boosting than I am.

My net isn't fast enough for a real fight.........

Real world; bigger eff islands are good; breathing to 40+ lb min of air is right on the money for top end power - if you can boost and get efficient air from 10-40; life is great... but that is hard to do.

I thought Jeff has a "how to read a flow map thread???"

Reading/using a compressor map is fairly simple.

Your Y-axis is your pressure ratio or PSI, it's generally expressed in BAR. 1 BAR being atmospheric. 2 BAR = ~14.7PSI of boost. To convert PSI to PR in BAR add and divide: PSI + 14.7/14.7.


Your X-axis is the volume of flow from the compressor. Generally expressed in pounds per minute. To comvert from CFM to lbs per minute divide: CMF/.076.

If your motor consumes ~26.5lbs/min at redline - like the Renesis - and you want to find a compressor that will run at 1BAR(~14.7PSI) of boost you would need to find one that will flow ~53lbs/min @ a PR = 2 at redline. Just follow left and right on the graph to see where these figures would land on any specific compressor map. What is plotted within the graph is the efficiency of the specific compressor. Each line represents a specific % efficiency. The greater the efficiency the less heat will be added to the charge as the air is compressed.

There you go - good explanation - I would do the math the long way; but that is just me.

thank you very much mac. now to go look at the map and try to figure it out :lol2: