Calenton
03-06-2013, 09:03 AM
So I've been trying to make a few graphs to represent the flow rate of the SR20 so that I can use them to compare turbochargers. This will allow the user to see which turbo will give them the most power and at what RPM. This is just to make it easier on the new guys and maybe some vets to select the turbo that will help them reach their HP goal and spool time.
The image attached has an excel graph, which plots flow rates in LB/MIN against Pressure Ratio (Boost), superimposed and stretched to fit the compressor map I got off of the Garrett website for the GT2871R series turbocharger which plots the same units.
For those of you that are running GT2871's I'd like to know how accurate my math is on the excel sheet. The colored points reflect Lb/MIN values of the engine and at the designated RPM (pink square is 3000 rpm, light blue X is 4000 rpm brown circle is 5000 rpm and so on from left to right on the graph). As the RPM's increase the amount of flow in the engine increases from left to right. From bottom to top we see the amount of boost you are running in terms of Pressure Ratio so 1 PR is 1 PSI of boost, 1.25 PR is 4 PSI of boost and so on as designated by the chart on the far right.
SO as we know the more LB/MIN you can produce, the more HP is made which is good. With this in mind lets calculate one of the points. Say at 6500 RPM and 2.25 PR (18 PSI) the turbo will be at one of its most efficient points and it will produce around 30 LB/MIN which if you convert to CFM is around 434 (use 1 lb/min = 14.47 cfm). Then if you use this to calculate horsepower we’ll get around 300 HP for that point. Of course the numbers will deviate a little for everyone but they seem to be within 5% of each other.
Lets do another for good measure. Say at 3500 RPM and 2 PR (15 PSI) where most people daily drive at, it will produce around 14 LB/MIN which if you convert to CFM is around 202. Then if you use this to calculate horsepower we’ll get around 140 HP for that point. It is also easy to see that this is a point close to the edge of the compressor map, denoting that at around this RPM the turbo begins to spool 15 PSI of boost pressure.
So the closer to the edge you are shows where you will begin to build X amount of boost at X RPM’s.
If your interested in seeing other turbo comparisons just PM me and I’ll whip one up for you.
NOTES:
All calculations and comparisons can be done yourself by just following what Turbonetics has to say (Compressor Maps | www.TurboneticsInc.com - Boosting Since 1978 | turbochargers, intercoolers, wastegates, blow-off valves, controls, boosting systems, turbo kits, forced induction parts & accessories (http://www.turboneticsinc.com/content/compressor-maps)).
Any points that fall out of the supplied compressor map represent compressor surge points or areas where you cannot build the designated amount of boost pressure at that RPM range.
The image attached has an excel graph, which plots flow rates in LB/MIN against Pressure Ratio (Boost), superimposed and stretched to fit the compressor map I got off of the Garrett website for the GT2871R series turbocharger which plots the same units.
For those of you that are running GT2871's I'd like to know how accurate my math is on the excel sheet. The colored points reflect Lb/MIN values of the engine and at the designated RPM (pink square is 3000 rpm, light blue X is 4000 rpm brown circle is 5000 rpm and so on from left to right on the graph). As the RPM's increase the amount of flow in the engine increases from left to right. From bottom to top we see the amount of boost you are running in terms of Pressure Ratio so 1 PR is 1 PSI of boost, 1.25 PR is 4 PSI of boost and so on as designated by the chart on the far right.
SO as we know the more LB/MIN you can produce, the more HP is made which is good. With this in mind lets calculate one of the points. Say at 6500 RPM and 2.25 PR (18 PSI) the turbo will be at one of its most efficient points and it will produce around 30 LB/MIN which if you convert to CFM is around 434 (use 1 lb/min = 14.47 cfm). Then if you use this to calculate horsepower we’ll get around 300 HP for that point. Of course the numbers will deviate a little for everyone but they seem to be within 5% of each other.
Lets do another for good measure. Say at 3500 RPM and 2 PR (15 PSI) where most people daily drive at, it will produce around 14 LB/MIN which if you convert to CFM is around 202. Then if you use this to calculate horsepower we’ll get around 140 HP for that point. It is also easy to see that this is a point close to the edge of the compressor map, denoting that at around this RPM the turbo begins to spool 15 PSI of boost pressure.
So the closer to the edge you are shows where you will begin to build X amount of boost at X RPM’s.
If your interested in seeing other turbo comparisons just PM me and I’ll whip one up for you.
NOTES:
All calculations and comparisons can be done yourself by just following what Turbonetics has to say (Compressor Maps | www.TurboneticsInc.com - Boosting Since 1978 | turbochargers, intercoolers, wastegates, blow-off valves, controls, boosting systems, turbo kits, forced induction parts & accessories (http://www.turboneticsinc.com/content/compressor-maps)).
Any points that fall out of the supplied compressor map represent compressor surge points or areas where you cannot build the designated amount of boost pressure at that RPM range.