between 3.5 and 4.5 K I am around 15 up to 23 psi

on fifth gear @3K I am doing about 15 psi and @ 3500 I am full boost 23 PSI

on race I do 30psi and drop down to 26 psi

You dont need engine managment for the surge. you just want to see how the car feels.

I dont understand how he is able to boost so much on that small turbo. "Not small but you know what i mean" Anyway i would think that 30psi is way out of its efficiancy range. But who knows? I might be looking at getting the GT40 instead of the GT35R so Thomas if you are interested i might have a Brand New GT35R for sale.

Chris

Looking at the compressor map, 30 psi looks like it is no problem at all and is still pretty efficient. The map shows PRs over 40 psi.

Eric

So now im all confused. When i was ordering my kit they told me no more the 28psi on the 3071. Now they are telling me no more then 35psi on the 35R. The 35R has a higher effienceny range of 79% compared to the 3071 77%? Am i just not understanding becouse you guys totalling lost me now. I still would like to learn how to plot on the graphs like that! HELP PLEASE!!

Chris

Chris you are always lost . your turbo should hit 35 psi no issues and I would take it up to 40PSI. on my turbo the 3071 anything above 33~35 psi I will be just cooking chicken .

The efficiency that you quoted of 79% and 77% is the max efficiency of the compressor at a certain boost (PR) and airflow. That doesn't necessarily mean that the Evo (2.0L engine) will be in that range.

That is why you need to plot point on the compressor map to see if the turbo is right for your engine.

The only way to find out for sure, it to have the turbo and log your PR and airflow for a pull from lowe RPMs to high RPMs....like a third gear pull from 2000-7500 RPM.

But, obivously if you don't have the turbo, you can estimate, as I believe alltrix99 has shown us on the maps. Here is how you do that:

Take the equation for airflow through an engine, which is
airflow=(Cid*RPM*volumetric efficiency*.5)/1728
-Cid for a 2.0L engine is 122
-RPM= plug in different RPM numbers...start with the RPM where you think full boost will be and use a few more numbers past there...ie 4000, 5000, 6000, 7000, etc
-Volumetric efficiency= again, this will vary depending on cams, intake manifold, turbine housing, etc. In general, 1.0 is good for lower RPMs, tapering down to .85 or so for higher RPMs towards redline. If you're not sure, just use .85 or so for all of the calculations

The number you get from the above calculations will be airflow, but in CFM. We need to convert this volumetric airflow into a mass airflow (lb/min). However, temperature plays a role in this conversion, but if you do not know the exact intake temps in your intake manifold, you have to estimate again. At standard temperature and pressure (STP), you can multiply CFM*.0756 to get lb/min. (If you are heatsoaking your intercooler or running the turbo way past it's efficiency this will raise the temperature and lower the conversion to lb/min.) But, just use .0756 as an estimate.

[Note: Can you see how many variables and estimations are already going into this? That's why it is dependent on every car, it's VE, the temperature, and so on...]

Back to the discussion...
Now you should have a lb/min number. That is how much your engine can flow at 0 boost. But, to plot the airflow on the compressor map, we need to know the boost, too.

To get the PR, use the following equation:
(boost+14.7)/14.7 = PR
So, if you wanted the PR of 15psi, it would be (15+14.7)/14.7=2.02 PR

Finally, take this PR and multiply it by the lb/min number that you came up with above. Plot these two numbers on the graph and do it all over again for a different RPM and/or PR.

For example, maybe you picked 7500 RPM at a PR of 2.02 for 15psi. Maybe you got 30lb/min. Just go to the map and plot the point where 2.02 (on the left) intersects with 30lb/min (on the bottom).

Hopefully, I explained well enough. This is how alltrix99 plotted his points. But, as you can see, there are a lot of variables. That is why I wanted a log from EVOVII SWE. If you have the data, you can plot the real data on the compressor map and find out exactly what is happening.

Eric

Very good write up. I understood it all and i have been trying to figure this out for awhile now. Anyway Saturday i will have all these variables recorded by the AEM so i should have all that data to a T. I should be able to see exactly how things are going from there right? And then make my decision about maybe changing to a different turbo from the GT35R.

Thanx Agian!
Chris

Yes, with the AEM, you don't have to do anything I mentioned here. Just log boost and mass airflow(grams/second, lb/min, or whatever).

Change the boost to PR and plot the points or graph them using Excel or whatever right on the map. This will show you exactly where your car is operating on the compressor map. You can see how close to surge you are, what efficiency range you are running in, etc.

Eric

I didn’t drive the car much after changing the housing last weekend so tonight I decided to take it for a spin to really try to find out if the change made any difference. After this test drive I can still say that I can’t feel or notice any difference what so ever in spool up or lag between gears.

However I found one difference that really puzzled me, my EGT values has never exceeded 800-900 degrees Celsius at WOT in high rpms and high gears. Tonight I suddenly noticed that my red warning lamp at 1000 degrees started flashing after a WOT in 3rd up to red line at 7k then shifted to 4th and got almost up to 7k when I noticed the red lamp. Doesn’t that sound a bit strange after changing to a larger a/r housing and lowering the boost slightly from about 24-25psi down to about 21-22??? I really don’t get this at all, I would have guessed that those two actions would have lower the EGT readings slightly if anything? I haven’t changed anything else at all, no changes in ignition or fuel settings and no other HW changes beside the housing and the spring in the waste gate.

So any ideas or thoughts about this???

Were you logging that run? Can you log knock?

A higher EGT just means that timing was getting pulled due to knock (if fuel settings are the same). Was it hotter this day than before? Were your intake temps hotter, etc.

I do agree that it sounds like you didn't get the .82 housing, though.

Eric

Yes, log your knock and timing/timing retard settings right away. They will tell the story.

Well, as far as I know I have a static mapping for fuel and ignition in the Motec, which means that timing could never be pulled except if engine or intake temperatures would get too high but it doesn’t use the knock sensor at all. It was actually colder now than before so intake temp at least shouldn’t be higher. I’ll borrow a wide band lambda some time next week to check if it might be running lean for some reason.

And regarding the .63/.82 issue I was once again on the phone with ATP last night and they had the housings side by side and everything indicates that I have the .82 now apart from the fact that it doesn’t seam to make any noticeable difference in boost character.

Another thing that I was thinking about was that I turned that cam shaft position cylinder 180 degrees to its correct position, this could, I guess, change both fuel and ignition but I had driven the car some after that but before we changed the housing and never noticed that the EGT went up more than it did before. I’ll get the ignition map by mail from the guy who did the tuning and the I’ll check the timing on the car to se if it’s still the same.

I'm not too sure about the EVO, but what did you change? The cam angle sensor? Is this on the intake cam on the EVO?

If this is what you are talking about that will definitely have an effect on your ignition timing. What were the reasons for the change and have you tried the new housing without changing the position of the sensor?

I cant believe the Motec does not monitor knock. This does not sound right to me. If it doesnt i can see that being a huge downfall from its competitors.

Chris

I believe the Autronic doesn't monitor knock either.