Ok this thread was prompted by T-Rex-8's comment i have quoted below


Id like to see posted here the compressor maps for the various Turbos in the available turbo kits out there so we can have a discussion on which T is really the best suited for the 8 . Also Id like to see T_Rex post up what he thinks is the correctly sized Turbo.

Lets compare. I don't have time right now to collect them myself from the various threads as im due in the living room for a butt whooping at GO FISH

 

Where is that pic of the three turbo's Jeff made?

I can never find it when I want it.

This seems kinda stupid unless we all ahve an equal Mass Airflow we are going for.

So to start off - I say the RX8 range should be - 7 lb/min to 55 lb/min would be our operating range... seem fair?

 

so which kit that vendors are providing has the oversized turbo's that t-rex is talking about?

 

Ok - so who wants to do the math?

7 lb/min at 1500 RPM = what Pressure Ratio?

50 lb/min at 9000 RPM = what Pressure Ratio?

Assume a VE% of 1.

 

i thought you were the math guy?

05rex lets deal with the message and not the messenger please.

 

good read which is on topic

http://www.rbracing-rsr.com/turbotech.html

edit: another helpful link

http://www.automotivearticles.com/Turbo_Selection.shtml

 

Aww come on I am sitting on a cot right now...

I might do it after dinner if no one else is gonna..... lazy!

 

I doubt there is a turbo that can do it . The 3071 does not even come close to staying in its efficiency range when pushed
Would like to see maps for the Esmeril and Mazsport turbos to compare ....

 

50 is North of the 3071R's range; I am just saying that was an absolute maximum for our treet driven RX8's.

 

PR Compressor = (boost - PD + ambient)/ambient
Ideal Temp Out =[(Tin + 460) * PR^.283]-460
Actual Temp Out = [(Tout Ideal – Tin) / Efficiency] – Tin
Density Ratio = PR * [(Tin + 460)/(Tout+460)]
Engine Displacement +[(#Cyl)*(Stroke)*(Bore)^2]/1.27
VFR100% = [(Disp)(RPM)]/ 3456 or 1728 rotary
VFRactual = (VFR100%)(VE)
MFR - NA = [(2.703)(PAmbient)(VFR)]/[TAmbient + 460]
MFR - FI = (MFR-NA)(DR)

 

Everything you're asking for has already been answered....

The best turbo for the RX8 would have a custom turbine housing and we already know which turbo has that.

Huh? There's two sides to a turbo and you're forgetting the other side.

 

For the 50 lb/min goal.
VFR100% = [(Disp - 80ci)(9000)]/1728 rotary = 417 CFM
MFR - NA = [(2.703)(14.7PSI)(VFR - 417)]/[TAmbient-80 F] + 460] = 30.6 lb min
MFR - FI = (30.6 lb min) * Density Ratio of 1.68 = 51.4 lb/min

PR Compressor = (Boost (Say 16 lbs) - (Pressure Drop-2 PSI) + ambient)/ambient = 1.95
Ideal Temp Out =[(Tin of 80F + 460) * PR^.283]-460 = 192 F
Actual Temp Out = [(Tout Ideal - Tin) / Efficiency (Assume 70F)] + Tin = 240F
Intercooler Efficiency of 70% = 168 F
Density Ratio = PR * [(Tin + 460)/(Tout+460)] = 1.68

 

So mark a 1.95 PR and 51 lb/min of air on the chart.

Now someone else do the 10 lb/min one.

Actually the PR would have to be higher since the VE isn't one.... but whatever. We could just round them to PR of 2 and 50 lb/min... this whole argument can get crazy otherwise.

 

you have missed the point entirely. if you can add a map or other info please post. if you can factually debate for or against a particular turbo please post. if you cant dont.

 

yes exactly kane.

 

Ahh **** it.


For the 7 lb/min goal.
VFR100% = [(Disp - 80ci)(1500)]/1728 rotary = 69.4 CFM
MFR - NA = [(2.703)(14.7PSI)(VFR of 69.4)]/[TAmbient-80 F] + 460] =5.1 lb min
MFR - FI = (5.1 lb min) * Density Ratio of 1.34 = 6.8 lb/min

PR Compressor = (Boost (Say 7 lbs) - (Pressure Drop-1 PSI) + ambient)/ambient = 1.41
Ideal Temp Out =[(Tin of 80F + 460) * PR^.283]-460 = 135 F
Actual Temp Out = [(Tout Ideal - Tin) / Efficiency (Assume 70%)] + Tin = 158F
Intercooler Efficiency of 70% = 110 F
Density Ratio = PR * [(Tin + 460)/(Tout+460)] = 1.34

 

So we want a turbo that will boost to 7 PSI at 1500 RPM's and Hold 16 PSI at Redline Efficiently.

So

7 lb/min @ 1500 = PR of 1.5
50 lb/min @ 9000 = PR of 2

Now go find this magical turbo that will be efficient in this range......

Or more realistically - go find the one that is the best fit.

 

I have no idea what you did there but it looks impressive

 

 

And what have we learned about our huge oversized penile compensating turbo's?

 

well until we get a couple more maps nothing except that i got you to do the math by leaving and getting my *** kicked at candy land by a 4 year old. totally worth it.

im goin to watch BSG now so if there is more to do.....

 

Even the big boys won't look too bad... assuming you can spool 'em which we can do better than pistons... it will just shift right some.

 

I remember seeing some maps in one of the esmeril threads - now how many pages is that now ????

 

dont you have software that does that?

beers

 

well first i think 55lb/min is a bit of a stretch for the typical street car. Thats around 490 at the flywheel
I think 40-45lb/min is a bit more realistic. 44lb/min is closer to 400 at the fly
^^this assumes AFRs of 11.2-11.5

that puts the 3071R at an almost perfect match. I dont think you'll find a turbo that will spool like everyone wants and still play nice at 55lb/min.

i couldnt find the Esmeril compressor chart, if it was ever posted - i think it's gone now.