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Old 02-16-2011, 05:33 PM   #6
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Join Date: Nov 2004
Location: PERRIN Performance

EFR7670 vs. GTX3076R

As I had shown before the GTX turbos spool the same as the GT turbos. So its not a question if GTX is going to spool faster than the EFR, it's a question of how much power will the GTX3076R w/.82 make. As I had show the GTX3076 made about 20WHP over the GT3076 and you can see here that it's still not quite enough to overcome the EFR7670 HP. Looking at the purple line showing 1.5 bar of boost, you can see a bump in power at 4000, but that is where the EFR was running a bit more boost than it was supposed to. Besides that you can see they make about the same power until redline. Why is that??

Below are the 1.7bar runs and it shows about the same thing. The GTX and EFR make very similar power until 6000 RPM where the EFR starts to pull away. The blue line in the below graphs shows also that the area under the curve on the EFR most likely outweighs the 250 RPM slower spooling. That and the fact on the street the EFR is more responsive between shifts but more on that later.

Now if you compare the EFR7670 compressor map to the GTX3076R compressor map you will see how the GTX is more efficient higher up on the pressure scale, but not by much. In the grand scheme of things a few points in efficiency here or there doesn't really matter. This could be why the GTX3076 and the EFR7670 both made similar power at this boost level. At this level both are starting to run out of air and become less efficient. During the EFR7670 tuning I ended up getting some engine noise that I felt needed some timing removed. No I never hear knock but I pulled .5 to 1 degree at 6000 as it just wasn't perfectly happy. Again trying to keep thing consistent I was not experiencing this on the GTX tests. I had a target for engine noise on these runs and it was being exceeded. This is a one of the logs, and you can see how I use the individual cylinder noise as a guide to what is going on.

This is one of the runs that you can see I got some spiking in engine noise. It crossed the threshold for knock (that I set) and it pulled timing. But anyway in keeping things consistent, and while this didn't loose power or cause audible knock, I lowered timing to keep things consistent between the GTX and EFR tests.

Some might come to the conclusion that this turbo is less efficient than the GTX which is why I got knock. Well yes and no. The compressor wheel is less efficient, but my Methanol injection masks a lot of that. But as the engine becomes more and more efficient, the combustion chamber also does. A more efficient combustion chamber typically has faster, more controlled flame burn rates. This in turn means you need less ignition timing to get the same peak cylinder pressure. Is this what was happening because of the freer flowing nature of the turbine housing and wheel?

And finally here is the 1.9 bar results still show great Wheel HP and 480WHP is nothing to complain about that is for sure. Keep in mind that If I remove my TGV's, maybe wrap the header, there is more power to be had for sure. Is there 500WHP to be had here?? I say yes on an engine with heads and cams, and with a higher redline.

Why is the turbo not making more power than the GTX3076r? Here is the compressor map for the EFR using my engine data plotted on it. You can see that at 7000 we are off the compressor map. This also is true for the GTX3076r and GT3582R. But still this is making great power and for sure there is more on tap with the use of race fuel, higher boost, heads, cams....

EFR7670 vs. GTX3582R

So now lets compare the GTX3582R to this turbo. First up is the GTX3582R w/.63 housing. In this case the EFR blows it out of the water. It spools the same but it makes about 20more WHP everywhere. This is because the EFR has a much freer flowing exhaust housing/turbine wheel. According to Garrett's site this combo only has 22.5lbs/min of turbine flow capability. The EFR flows 24.5 lbs/min. That change in 2 lbs-min is 20WHP! So in this case the GTX3582R w/.63 housing is no longer a match for the EFR7670 with .83 housing. You can see below the blue line makes a lot more power everywhere.

I didn't put up the GTX3582R w/.63 and 1.9 bar as it shows the same thing. The EFR makes more power. But below you can see when we compare this to the GTX3582R with .82 housing, things start to change....

Now you can see this comparison look like the EFR7670 vs the GTX3076R, but this is the GTX3582R w/.82 vs the EFR7670 w/.83. If you think this is the more comparable turbo to the EFR7670, you would be correct. In this case, the EFR spools much faster and makes pretty much the same HP. At this 1.7 bar level, its obvious what turbo is best for you. Looking at the plot above, you can see at 1.9Bar of boost, the EFR efficiency starts to fall off at redline. Don't jump to conclusions that this is bad because GT3076 customers are constantly running WAY off the map. Here is a GT3076 compressor map plotted at different boost levels. Now don't forget I ran the GT3076 at all these levels and it made plenty of power.

Here is the GTX3076R with the same boost plotted and you can see how this matches pretty close to the EFR7670 where it just starts to run off the map at 1.9Bar and redline. Again we were running this off the map and it was still making lots of HP, so its not bad to run it off the map necessarily.

One more comparison is the GTX3582R w/,82 AR. You can see that the GTX compressor map is much more efficient at these boost and RPM levels compared to the EFR7670. But really the GTX3582 compares closer to the EFR8374 but we are not testing that turbo here, but soon! But this graph is more for comparison purposes and may explain why the GTX3582R made a tiny bit more power.

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Last edited by PERRINJeff; 10-24-2013 at 12:51 PM.
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