cam for a turbo motor?

[Madd Maxx]

I'm not sure how familiar you are with turbos, but the T76 has a fairly high A/R ratio. It's 0.96. That's the ratio of the area of the turbo housing to the radius from the center of the impeller. Turbos that have a ratio close to 1.0 are intended for high RPM use. They will spool up slowly due to the slower gas flow through the larger housing. This may be what you're experiencing, assuming it's the cam. Your cam has plenty of duration.

[r.barn]

I'm not sure how familiar you are with turbos, but the T76 has a fairly high A/R ratio. It's 0.96. That's the ratio of the area of the turbo housing to the radius from the center of the impeller. Turbos that have a ratio close to 1.0 are intended for high RPM use. They will spool up slowly due to the slower gas flow through the larger housing. This may be what you're experiencing, assuming it's the cam. Your cam has plenty of duration.

Yeah, but he's running a 408ci 6.0L motor.
A T-76 should spool up nice even with large A/R with all those cubes

1.0 A/R is intended for high rpm on small inline 6 motors (ie Supras)

[Madd Maxx]

It's an N/A cam, with bigger intake duration vs. exhaust. Turbo cams are the opposite or a single pattern with like a 117 LSA.

This is not necessarily an accurate statement. Having a shorter exhaust duration is a trick that turbo users have been using for many years. Pushing the gasses out in a shorter time increases the gas velocity, which helps the turbo spool up faster. With the advent of variable vane technology, however, it is no longer needed. But that's just currently for the diesels. Gas engine variable vanes are just being developed because of recent breakthroughs in high-temperature materials.

226 is a bit short duration for a 6.0L too. The longer stroke needs more
valve open time to fill bigger cubes.

This is also not an accurate statement. With a longer-stroke engine, the piston moves faster down the bore on the intake stroke, which causes a greater pressure differential between the cylinder and the intake manifold. This increased pressure difference causes the intake charge to flow faster, which increases the filling rate for the larger cylinder size. It is true, however, that larger engines can absorb longer duration camshafts, but it's primarily due to the increased torque of a larger engine.

[Madd Maxx]

1.0 A/R is intended for high rpm on small inline 6 motors (ie Supras)

If the turbo is sized appropriately for the engine, the ratio holds true. It's not intended for any specific application, it's intended for all applications - the key parameter being the turbo's size. For lower RPM use, the A/R ratio should be in the 0.6 to 0.7 range.

[ff_jeff]

:wtf:

[Show&Go]

OK MAXX because you are ROCKING SOME SUPER technical answers here. And you seem to be on a roll. I haft to ask since I am working toward a turbo. I am only plannin to prob spin up to 6200 RPMs on a 5.3 What size turbo would work best for what I am thinking. Also I was planning a 220-224 Cam with 581/581 on a 115. So by your posts to improve the gas pressure I should get a 224-220 instead? Would this still be a good NA cam till I get the Turbo system. (talking a good 6 months from the next cam swap till the turbo kit) And going back to the post in general by what everyone is said shouldnt how far Drop em runs his motor into higher RPMs play a factor in what cam he needs to run?

[rutroe]

All theories aside...my 212/216 works pretty darned good on my 5.3 with the T76 turbo...all the way up to around 6000 rpms. Good info though...

[GasGuzzler]

what exactly is your issue?

Good point. We need a little more information on your problem and why you're not happy to help decide what to change.

[Justin_Inc]

If the turbo is sized appropriately for the engine, the ratio holds true. It's not intended for any specific application, it's intended for all applications - the key parameter being the turbo's size. For lower RPM use, the A/R ratio should be in the 0.6 to 0.7 range.

A turbine A/R of .6-7 would choke that engine off pretty bad in the high RPM's especially on high boost levels. There is a point where you will start to hurt **** from excessive back pressure. Sure it'll spool on demand, but thats not always a good thing. Plus slow spool times can be caused by a number of things, not just the A/R of the turbine.

to the OP, what is it you specifically dont like about this setup?

[Madd Maxx]

A turbine A/R of .6-7 would choke that engine off pretty bad in the high RPM's especially on high boost levels.

I'm not sure I follow your point, since the sentence you quoted started off with "For lower RPM use . . ."

A diesel would be a good example of an engine that would use a turbine housing with an A/R of 0.6-0.7.