Found another turbo, curious about these things.

T-76 a/r .96/.72.
What the heck are those numbers? it ALMOST sounds too darn big... evem though i know little the T-76 sounds bigger than a T-3 lol.

 

T76 is the compressor size, which is fine for most small blocks. The AR is the turbine size, the smaller the # the smaller the turbine. Why you've got 2 A/R #'s I don't know

 

so what would be a reasonable price for a rebuilt turbo like that? $1000? $500?

 

Donno, but I did see a newish one (supposely a few hundered miles before the guy descided that he didn't like how it spooled on his GN) for $700 on the turbotraider a couple of months ago

 

a rebuild is easy and can be done at home.

or if you really want to send it out, usually $250 plus shipping

 

T76 is worth about $1250.00 new. 76 simply means that the compressor wheel is 76mm they normalLy a P or Q trim on the exhaust side and it is a big shaft turbo (more money).The a/r is size of the exhaust housing. The bigger it is you need more exhaust for spool up.96 is a common size housing which will work fine with a SBC. I have never seen a housing with two different a/r. maybe he has two different a/r exhaust housings. When my TA was a single turbo it had a 60-1 turbo with .96 a/r housing with p trim exhaust wheel. now I have two Hi fi 60-1 turbos with .59 a/r exhaust housing. On my GN the stock factory size a/r was .63 three bolt exhaust housing, but I run a .81a/r exhaust housing 4 bolt with 70mm compressor wheel. the car has a little more lag compared to the .63 stock setup but with a higher stall coverter and good heads I was able to over come that and have great top end due to the reduced back pressure. When I switched from a .63 a/r to .81a/r my GN went .3 sec 3mile/hr faster.

Good luck

Prasad

 

If it has a .96 your gonna need some serious exhaust pressure to spin that sucker up without a healthy stall. If you have a choice go with the .72. It'll spool quicker and make it more drivable with a lower stall.

 

IIRC, Guido is running a .96 AR on his PT88 on his Single. I think though that he is running a TH400, on his Big SBC. I would be interested in knowing what stall he is going to run (Guido??).

BW

 

Regardless of the stall Guido has an advantage! More cylinder volume(large bore SBC) which equates to more exhaust gases to spool the turbo. He could theoretically get away with a smaller stall converter than an evenly modded 350.........

 

SO technically its better to have two smaller turbos than one big one? faster boost and more of it? I always thought 1 big turbo was the way to go for max HP... and twins were good for the street. is this true?

 

With the PT88 that guido runs....the reccomended stall is in the 4500range. I believe he is running a 8" 5000rpm converter from coan.

Twins are more forgiving for making huge power at streetable RPM levels yes.....at least IMO

 

Yes

No

Maybe…

Yes - The inertia of the compressor/turbine assembly is proportionate to the ^4 of the radius, so a turbo with a slightly smaller major diameter will spool more easily, as will 2 substantially smaller turbos compared to a large single.

No - OTOH, how well a turbo spools is also highly dependant on the plumbing. Optimum for a small t3 on one bank is probably something along the lines of an exhaust manifold with as low a volume as possible that retains as much heat as possible and then a down pipe in the 3” range. Smaller downpipes will work and make similar power but the turbo will be slower to spool. I haven’t seen anyone running bigger then a 2.5” down pipe with twins on an f-body, it’s just very difficult to fit.

Maybe - it really comes down to the packaging and parts selection, you can’t say that one will spool better then the other without taking that + other things like cam selection into account. Smaller twins will be more likely to spool quickly. OTOH, how quickly do you really want them to spool? In a perfect world you’d be able to put down all the power you manage to make at any instant, but in the real world, you’re talking about a good size V8 that’s going to have a tendency of making an abundance of low end without the turbo… a little bit of sluggishness in the spooling will help make the car driveable.

 

More Cly volume than what? I dont see a motor size here except for what you put. dont get me wrong, we are on the same page, this is all about relativity. too big a turbo only means that we are building to small a motor Heck get two of them & build a MUCH larger motor & call it done.

a 5K stall converter on a large SBC is a lot of air, gotta love that!

BW

 

I assumed in his sig it was a 355. The voulume of cylinder A(355) v/s the volume of cylinder B(406). Being that there will be more gases from the larger engine it would be easier to spool a larger turbo compared to the 355. That's all I meant.........