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oh and this is for a RB20 just want to work out the final numbers. im building the engine for drift so want good mid range response and as much top end as i can. new red line is 8500. 4k and below i dont care about. if i will make more power with an 8.2:1 with 25psi that would be better, im just not sure how that all works

Boost is not your friend, airflow is.

If you are serious about building such a motor start googling and learn how to read compressor maps.

You will see that the most you would want to run is from around 18-22psi absolute max.

I wouldn't go below 8.5:1 personally.

See the Y axis PR value of 2

That is 15psi.

2.5PR is 22psi. As you can see this is nearing the top edge of the compressor map. The center island within the map is where the turbo is most efficient.

Do engine airflow calcs and plot RPM's on the graph.

At high rpm its best not to have the engine airflow heading out of the map (to the right obviously) as you will enter the choke zone. The choke zone is where the turbo is very bad at pushing air. Not efficient. This is what people mean by keep pushing boost in to it until it doesn't make any more power.

At low rpm you don't want it to be boosting to the left of the map as this is the surge zone.

Its a little complicated to workout the airflow, but not impossible.

You need to take into consideration air temp, intercooler efficiency, volumetric efficiency etc.

22psi will run in to choke at higher rpm's.

I'm trying to explain it in lamens. :P

Imagine plotting on the graph, as rpms increase at a certian boost level the engine consumes more air, i.e the plots will slowly move to the right.

Running a constant 22psi right near the edge of the map, the turbo is able to flow less air than a PR of ~2.3 or 19psi.

So theoretically you will be better off running 19psi at high rpm as it will get you the most out of the turbo.

I'm not 100% on all the comp maps etc but I do have a rough idea. There's still a few things I don't understand 100%.

i was just wondering if anyone knows what psi range a Trust TD06-20G is rated at.

currently have same turbo on my Rb20 and i have had it running slightly over 1.5bar with out a problem. (engine has been built to cope with this though) i would suggest that if your serious about building a drifter and if you have ever tried to drift then you would know that anything over 18psi is just asking for trouble really.

Aim to build the car so that you can hold around 14-16psi and the rev range will depend on how hard you want to push it and how often you hit the limiter.

If you want any info or looking for something then send me a PM as we might be able to help each other out???

Cheers B

The engine very well may be still within the compressor map at 1.5bar on the rb20.

Slap the same turbo on a rb25 and it may be stepping out side of the map at only 1bar.

You really need to do engine airflow calcs then work out what what the X-axis values on that damn compressor map are in.

hhmmmm ive never had a problem. running over 20psi

i never said you would have a problem running over 20psi did i. I said why would you want to run that ofr drifting :confused:

If you have to be running that sort of boost then you have to be extremly high up in the rev range for drifting which to me just doesn't seem the best option!!!

I could be wrong but if you look and talk to most experince drifters that do it for al iving they will tell you the same thing. You will find that not many of them would be running over 14psi.

But thats just my 2cents and happy drifting at 20psi :crazy:

nah buddy, no crankiness. It was bed time when I wrote that last post so it was short and sweet so to speak. :P

When I have some time, out of my own curiosity I will do the rb20det's airflow calcs and plot them on the compressor map. I still think the TD06 is one of the best matches to the rb20det, with the right exhaust housing that is. :)

The boost you run is irrelivent anyway. Its the power you make that matters.

Slap that same turbo on a RB25DET and you will find to make the same power you will need around ~6psi less.

Thee's also the reliability issue of running such high boost all the time, not so much the engine but the poor old bush style turbo that requires rebuilds every 40,000km's, and thats with a fairly normal life, not 25psi. :P

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