General Turbo Chat

[demon1300]

The old rule I feel still applies. Makes the desired power with as little boost as possible. I think this is extra important, especially with a stock engine!

@HI PSI what were your thoughts on the 42 as a street turbo? Feel lazy? Yours is manual also yeah?

Edited 20/04/17 10:51 PM by demon1300

[MattyP]

9 hours ago, Puffwagon said:

 

 

I'm not sure I'd like to deal with every hose, gasket and fitting popping off and generally sh*tting itself under the amount of boost the bw would have to make to match the garrett. I suppose it's not insurmountable.

 

Lol would it make you feel better if I said the absolute air pressure at my house is 14.65psi @HI PSI

 

 

Are you you sure your calculations are correct, that seems like an insane amount of flow through the boogie to make the same power? 

 

Personally the the combination of manual and such, I'd be spending my money on the Borgie for all round streetability, while it may not make the same peak power, power and torque under the curve, earlier on would be key. 

 

Nothing wrong with a gtx42 at all,

 

jeez we are lucky with all the turbo choices we have 

[Puffwagon]

I didn't plot the barra on either compressor map so it is entirely possible that the initial pressure ratios were incorrectly assumed to be necessary.

 

Pressure ratio is defined as absolute inlet pressure divided by absolute outlet pressure. 

 

The math is simple; gauge pressure plus atmospheric pressure divided by atmospheric pressure.

 

Atmospheric pressure at my house is 14.65 psi according to my barometer. It actually varies a bit 

 

To calculate the boost needed to run a pressure ratio of 4 in the bw you calculate it like this; 4 multiplied by 14.65 then subtract 14.65 from that number. It's 43.95.

 

When we talk about comp wheel size we commonly refer to the inducer.

 

The bw compressor has a 67.7mm inducer vs the 76mm in the gtx. That is a significant difference.

 

The gtx flows approx 110lbs/m at 109,000 rpm vs the bw needing approx 116,000 rpm to make 95lbs.

 

I'll post up a link shortly that will help. 

[Puffwagon]

This will convert your barometer reading to atmospheric pressure.

 

This is the a 4 litre plotted over the 9180 comp map with the bw matchbot. It can be adjusted based on the variables in the calculator. I've tried to keep it as close to 800 hp as possible.

 

In this example a touch less boost is needed to get the 800hp but it is still up there.

 

While a turbo or comp map calculator is close it will vary from real world testing cos reasons.

[HI PSI]

Could you please explain the turbo expansion ratio, where the figures were derived and the effect that this has?

[Puffwagon]

If you scroll to the bottom of the page there are instructions on how to set up the calculator.

 

In short you pick a turbine wheel size and a/r from the right hand side of the turbine map then adjust the turbine expansion ratio figures until all of the plot points are on that same line.

 

Edit: The effect on turbine a/r can be found here.

 

I chose the 1.45 rear housing in my example.

 

This is the 1.05.

 

This is the 0.83 and 0.91.

 

Note in my first example that I had a typo in the afr at 7k rpm. It should be 12:1 not 2:1.

 

Ninja edit: Play with the values and see what changes.

Edited 21/04/17 02:17 AM by Puffwagon

[HI PSI]

3 hours ago, demon1300 said:

The old rule I feel still applies. Makes the desired power with as little boost as possible. I think this is extra important, especially with a stock engine!

@HI PSI what were your thoughts on the 42 as a street turbo? Feel lazy? Yours is manual also yeah?

 

Personally, I love the turbo. I started making positive "BOOST" at 2200rpm when doing 3rd gear power pulls. And when I say "pull", I mean this baby pulls like a freight train. With a  basic road tune, running on 98 with 20 psi, it was frying my 285 Nitto Invo's during the runs.. 

 

Overall, this is a great turbo. It is more than capable of fulfilling my needs and it is very nice to drive on the street. Having a 1.01 rear housing certainly helps the cause. But, I will be testing a 1.28 in the near future.

[MattyP]

Flick that calculator over to e85 and wow things change

[Ralph Wiggum]

Flick it over to Diesel and sh*t gets weird 

Edited 21/04/17 02:48 AM by Ralph Wiggum

[Puffwagon]

I haven't tried flicking it yet. Brb giving it a flicking 

 

Edit: Flicked over to e85 without the crazy boost number at 4k rpm. That looks much better.

Edited 21/04/17 03:10 AM by Puffwagon