Turbo BS Thread

Wow. I bet that was a brief rush!

 

With my 2tr I had a gtx 2860r gen 2 and it would be fully spooled at 2K.

 

Replaced the CAT, made a few other improvements while remaking the exhaust and truck is as good as it ever was!

 

That's great news! Let's see an acceleration video.

 

I found this video on Youtube yesterday about calculating for an appropriate sized turbo. Do you guys calculate similarly when selecting turbo size, or is there more to it than mentioned here? Using the formulas he provides (with similar estimates for BSFC, Volumetric Efficiency, Intake Manifold Temp, and air pressure adjustments), my results come out similar to his - 33 lb/min for air flow and 2.25 for pressure ratio. I also emailed Boost Labs for the compressor maps for the 6057 and 5757, and they sent the maps for the corresponding Garrett compressor wheels (which they use in these turbos):





If the calculations are correct, it seems like the 5757 is a better fit, but somehow that is not what I expected. Or am I completely misunderstanding something?

 

2.25 ratio is going to be about 18psi on a boost gauge. 33#/min is ballpark 300-350hp depending on tuning. I was pushing 36#/min on my Jetta 1.8t at 30psi if that helps any.

I never could calculate what an engine should flow but figured out how to read a compressor map. That 5757 has a wider range of efficiency island vs the 6057. Looks to spool up later but still a solid 14psi on the surge line before RPMs get high whereas my Holset surge line is nearly straight.

Here’s mine overlayed with 1.8t displacement by someone smarter than me that has done many spot on maps. The blue one is what my wheels measure as. Hope this may help.


Official map.

 

Well it happened in 1st gear so I would say "brief" is a perfect explanation, and by brief if you mean "it was so fast you couldn't even tell it happened since the tires just blew loose" then you would be correct!
I would have preferred to feel it after I had he fuel system to support it, and in a higher gear, I surely had the short block for it!
If you want the horses to run you gotta feed em' son!

 

Nice that dude put some serious production into that video.
The 5757 is a better fit for under 400whp. It's going to be more fun on street.
That 6057 is going to hit about 500 rpm later

 

This is the part I’m a little confused about. In the calculation he subtracted air pressure (14.7, which is what I’m likely at in Hawaii) and my total came out to 14.2 (his was like 19.8); but maybe it doesn’t represent the same thing. Is the 14.2/18psi what I mathematically what I’d need to make a certain horsepower goal with the data entered into calculation? And while the turbo can support that, and the exhaust can probably produce enough gas to provide that, if my engine cannot handle 14.2/18psi, then I would use the wastegate to regulate the psi (meaning I also won’t make my goal hp.) Is that correct?

Or, am I misunderstanding how the 14.2/18psi is calculated/measured? Is vacuum considered in that measure? I remember hearing about “low boost” systems (5-8psi) which so far I have thought to mean reading 5-8psi on a boost gauge, but now I’m not sure.

Anyhow thanks for the help - now leaning a bit more to the 5757.

 

The 6057 will come on boost sooner and possibly peter out on you as well as blow slightly hotter air. The 5757 leaves room for more later. The variable 14.7 should be replaced with whatever atmospheric pressure you are at where you’ll be calculating. Denver will not be the same as New Orleans.

My understanding is this:
2.25•14.7=33.075
33.075-14.7=18.375

Or you can look for your preferred pressure by:
18+14.7=32.7
32.7/14.7=2.22

EDIT: boost pressure is only a measurement of inefficient air flow. Your block may move more than you head or vice versa. Could be intake or plumbing to intake. If your engine can move more air than what a map shows at a certain PSI it still uses it. Also, you could hit a wall at XXpsi and not move any more volume than at a lower pressure. Then the choke point becomes a regulator, or restrictor, so to speak. Staying with 10-16psi is a good starting point and likely enough to make you content. I’d love just 8-10 on my 4x4 3rz but if I ever come across a 2wd 2rz Ima have to buy it for big fun.

 

Thanks for this - I like your formulas also, way simpler. It seems like with the wider island the 5757 is the way to go.

 

I pulled the block from my Jetta with the forged rods and pistons. Stripped the mounts and flywheel yesterday and this morning pulled the rods to give a quick hone on the cylinders. Then I was going to put it back together with new stuff when I encountered #3. The vertical scarring eventually honed out but the horizontal marring was a lot deeper than expected. It took a good deal of dingleberry hone work to get to this and at what cost would longevity suffer. So I went to ‘plan B’ and will use the Audi block if it’s not screwed up as well.

Any idea what or why this happened? Cyl 1 had some beginnings of this, too.

Before


After. This one refuses to not post upside down.

 

Started mocking up the downpipe today. It’s gonna be a tight fit near the AC lines for sure. Very happy with it so far though

 

Time to bore turn that 1.8 to a 2.0

 

Is that where the edge of a piston ring was, perhaps? On second look, it seems the scratches go almost the whole length of the bore.

The other grooves going around the circumference, look like rusting oil rings.

 

I like what I am seeing. For your short experience, those welds are something to be proud of.

Observation on the oil feed fitting. I recommend when you can, to use a 90°, like the one you have for the coolant. That hose would very likely hit the hood, if you don't.

 

Thanks Mark, I appreciate the kind words!

I am really thrilled with how it’s coming along. The pie cuts only tried to pull away from me once so things went surprisingly smooth.

Ahh yes good eye, that is actually the fitting for the coolant outlet but I have it in the wrong place. There’s another 90 somewhere around here for the oil feed, just need to track it down.

 

Exactly what I was thinking until I priced another set of pistons at $6-700.

It could very well be. All 4 bores had a ring on them and the engine was left open since the end of Sept 2021. I did pour some gear oil on the pistons and smeared it around the exposed areas above them. Coolant ports do have visible rust.

 

Any chance something else has the right diameter pistons that you might could track down at a pull a part? Ain't no shame in Frankenstein

 

Not that I’ve came across in all my researching. But I never specifically looked for that.