TiAL

if they say it was an overspeed, look at the back of the compressor wheel, it will look like a bad paint job - orange peel

CarsandWomen

iTrader: (19)

how/whys that? seems like an odd thing to look for when thinkin it was overspun

great421

iTrader: (1)

Chris -

Thank you for your words of clarity and wisdom.

I do understand that airflow (??? unit = lbs per min ???) is a better way of addressing how much a turbo can 'push' but the industry seems to speak in secondary terms (i.e. - psi) when talking to customers.

Having said that, after I changed intake manifolds (about 2 months ago) from my original / 100% stock unit to an agressively ported stock / GM LT1 intake; with ALL other factors remaining equal, my boost gauge (which takes its reading from the manifold) went DOWN from 11 PSI to 5 PSI.

The car felt stronger overall, but it didn't have that same 4,000 RPM power spike (or, as my brother described it - the 4K ON / OFF switch), so I turned the dial UP on my manual boost controller a touch (to 9.5 PSI) and lowered my Meth controller's 100% spray threshold. That did the trick, and got the "OMG turbo spike" back, but it may have forced my little 60-1 to exceed it's design specifications.

Anyway, you said:

This begs the questions: "What is the correct A/R?" and "Can two 60 mm turbos have different A/Rs?"

Maybe better stated:

How do I calculate the correct size and A/R for my application so I don't:

a) Overspool a turbo that is either too small in size or A/R and then excessively heat the incoming air and prematurely kill the turbo?
- or -
b) Pick a size and / or A/R that is too large and never fully build boost / sufficient airflow?


OK, from what I've gathered, in a turbo's callout (in this case, a TC76), the 76 relates back to it's radius (R = 76 mm), therefore, the larger the number the bigger (and heavier) the rotating parts, while the A/R ratio relates to the cross-sectional Area of the inlet side vs. the Radius.

Therefore, a large A/R ratio with a large R means a large turbo and a big pipe, however, a small A/R ratio with a large R means a large turbo and a small pipe.

So, if I understand correctly, then a larger turbo (ex. - 67 mm or 76 mm) with the same A/R as my current 60-1 turbo will spool slightly slower, but given the increase in cross-sectional area from 60 MM to 67 MM (12%) or even 76 mm (27%) - the engine will see more overall airflow at every RPM and there will also be less heat build-up; so a win-win, correct?

My (dead) 60-1 turbo has an A/R of 0.6 (cast into it's housing), so, do I need a 67mm or 76 mm with an A/R of 0.60 as well, or have I missed something?

Thanks in advance for the input!

kbracing96

iTrader: (25)

For your setup, I'd recommend a Master Power T70 with a .68 a/r on the hot side. If you check out my sig, you'll see thats the same turbo I had on my truck when I ran those times.

I've ran quite a few of these turbo's in similar setups and they always work well. Yes MP turbos are made in Brazil. MP is a large manufacturer of mostly OEM diesel turbos down there. There High Performance line that they sell here is only a small part of there business. I've been dealing with them for over 2 years now and haven't had any problems with them. It will bolt right on to your setup, the only difference is the MP T70 has a 2 1/2" out let on the compressor, where you STS turbo is only a 2" But that's an easy fix with a step coupler.

TiAL

just the affect that multiple hundred thousand RPM's has on the cast aluminum

xfactor_pitbulls

iTrader: (16)

A 60mm turbo doesnt belong on anything with 350ci. Do you have your hot (supply) pipes to the turbo wrapped, coated, etc? If you can keep the heat to the rear of the car a 70 would suit you much better. And it will still spool fine, again, provided you are holding heat to the rear.