Nissan 200SX Club - South Africa

Howzit guys…

I have been pushing numbers with regards to my Turbo , Unfortunately for me I am not 100% sure what compressor wheel I have but I don know its from a Garret GT series turbo.
So I have take three Turbo’s and also calculated my Piping size.

The Three Turbo’s are:

GT2560R – 0.42 A/R
GT2854R – 0.80 A/R
GT2860RS – 0.60 A/R

Now here is my Math and conversions, Maybe there might be a fault in it somewhere.

Displacement: 1809cc = 110 Cid
Max RPM: 7200Rpm
Efficiency: 85% (Not sure about this maybe someone has more info on the CA18)

Anyway after the math I get the engine will flow 194.7 CFM

Now I worked out the pressure ratio

0.5 bar (8 PSI) = PR 1.54
0.8 bar (12PSI) = PR 1.81

Air Flow at respected Pressure ratios.

Airflow = 1.54 * 194.7
= 300CFM
And
= 352 at 0.8 bar

Now I need to convert to LB/Min, I took an average air temp of 44 Degrees C. (I know this is High)
Anyway after the math

21 LB/Min for 0.5 Bar
24 LB/Min for 0.8 Bar.

Know down to the turbo’s and the efficiency’s:

0.5 BAR
------------------------------
GT2560R - 75%
GT2854R - 66%
GT2860RS - 75%

0.8 BAR
------------------------------
GT2560R - 77%
GT2854R - 68%
GT2860RS - 77%

Know I have always suspected that my piping size might be incorrect on my hotside, as I was using a 50mm Exhaust Pipe.
So we did the Math to make sure I was not exceeding the 450 F/S. Using the ID

ID = 48.26 mm
Anyway after the Math it works out to. 380 F/S
PR = 154

Now after all this math and stuff what the problem, While in my pursuit to prove that the CA18DET can make the number on low boost it seems I might not have taken into calculation that I will be pushing my turbo out of it efficiency ranges, Now this is just a basic calculation using 85 VE but I have added allot of toys that will change the VE of the motor for better making the situation even worse. I will need to move the turbo higher up in the flow map to do this I need to increase the pressure ratio hence increase the boost. But this is a compound effect and my diameter of hot side piping is taking the air velocity way to close to 450 F/s, I need to change this pipe and make a few other modification before I can change over too 0.8 bar boost but once done the is a possibility I will running cooler boost temperatures and making the turbo more efficient

I'll have a look at your calcs this evening after work. You may want to get an accurate VE % for your motor as it's possible to have a motor that operates at more than 100% with the right bits and pieces. At least then your calcs with be a lot more accurate as oppossed to guessing at 85%?

Anyway I'll report back later with my findings

On second thought rather go with a guesstimate for VE, the actual equations look to much like hard work

http://www.installuniversity.com/instal ... 012000.htm

The rest of your calcs seem spot on.

This link should help you choosing the correct pipe sizes or at least put you on the right track - http://www.tercelreference.com/tercel_i ... heory.html