**

 

I ended up getting a Garrett T4 Divided housing 1.15 A/R and got it whacked on a 6262 PTE turbo I had that was hardly used but it had a .63 A/R 5 bolt junk on it.

This should give it new life. I hope the 62mm turbine wheel likes the 1.15 A/R. The GT35R is 62mm 4 ml diff maybe 35hp up top.

Should get quicker spool with 62mm turbine but it won't have the top end there. Should make 700hp with my supporting mods.

 

35R is a very responsive turbo. I've never actually every heard of one being called laggy. I agree, I wouldn't go smaller than the 1.0. I've used the smaller .82 on rotary engines for cars that needed the response for autocross, but top end was seriously choked. That being said, I plan to go with a 35R in the near future.

 

The reason I started the thread was I read a phew opinions on the T4 divided and 1.0 to 1.06 was best so jumping to 1.15 I thought might be risky but obviously not. On a 4 cylinder twin scroll is way faster spool the exhaust gas pulses are evenly distributed between the cylinders on a TS housing. The 4 cylinders aren't always letting exhaust out at once this is where the signal scroll chokes and why you have a smoother power band on the ts.

Now regarding turbine size the 6266 has 35hp top end on the 6262 its the same compressor the GT35 being almost the same as the 6262 is a nice turbo for spool and top end your going to start lagging going to the 6466 to 6766.

 

i have a twin scroll HTA gt3582 with a t4 divided 1.06ar hot side mated with a fullrace t4 divided twin scroll manifold and i can tell you for a fact that this spools faster than my old open scroll t3 gt3076r setup with the t3 open scroll .63 ar hotside.

 

4 millimeters on the turbine side (62mm vs. 66mm) will equate to significantly more than a 35hp gain up top. This is especially true as boost pressure increases as well as RPM. With the right combination of parts and a full max effort, that difference in turbine side has the potential to net closer to 75-100hp difference. Back pressure is the enemy of big power numbers.

 

Depending what your own personal goals are for me the 6262 is one of the best all round turbos for street / strip.

 

That's great. I'm sure it is and I'm not questioning that at all. I was simply pointing out that a 6266 has the ability to produce considerably more than 35 additional horsepower over a 6262 on top, especially if backpressure is high with the 6262.

 

The 6262 doesnt hold a candle to the 6266. The 3786 is the Garrett/FP answer to that and while I havent had one in on the dyno yet (might have to buy one for myself) I know its going to work better than the 3586 even.

Aaron

 

I am also wondering which turbine housing to choose. I am building a 2.2 long rod mainly for drag racing. Any suggestions and/or tests? Anyone?

 

we'll be doing a 1.32 kit before too long. I personally dont think it is too large based on what we have seen with the 42Rs and the 1.15 so far.

 

Seems like the 1.15 A/R is the sweet spot on the GT42R from a response angle on a 2.0L to 2.4L. They show little difference in lag on the dyno, but locals using the 1.32 A/R say it adds a lot of lag driving around. Several FWD guys use it because it actually creates a bit of "traction control" effect with the added lag. It picks up some top end over the 1.15 though.

1.01 to 1.15 on the GT42R is all gravy on response and power though...

There is a balance point here. As A/R goes up, turbine efficiency usually drops. You have to have exhaust velocity and temperature to keep efficiency high but keep pressure low enough to avoid reversion. As efficency drops, you start to increase the required exhaust pressure required to drive the compressor in order to make up for the energy lost to the decrease in thermal efficiency and exhaust velocity.

 

I was figuring doing a 6466 in a 1.32 a/r. Since the 6466 in the low to mid 40 psi range basically offers the same power output as the 6766 but with better spool, it should also spool up better than a 6766 with the same turbine housing. Getting a larger hotside should reduce backpressure and help gain some serious top end pull for a high revving build.

 

Any users of a 1.32 a/r turbine housing care to share their experience?

 

On a 42R, which isnt exactly the same thing we are dealing with here I know, we went from a 1.15 on the 2.0L to the 1.28 and picked up 200rpm worth of spool and made 70whp more. Based on what I have seen from T4 single stuff and the twin I think the 1.32 will continue to gain, here is why.

Little Joe was running a 0.68 T4 on his P-trim based 3586, made 727whp. We swapped to the 0.81 and lost no spool but made more power out the top. Since the Garrett math for sizing is the equivalent T4 single x 1.2 we'd be at 0.972 TS or let's say the 1.00 A/r.

In testing we saw a 1.15 TS (6466) match Joe's car pretty much identically though when it was the 0.68 as far as spool. Garrett math is 60% of the TS for equivalent single sizing to get the effect, 1.15 x 60% is 0.69...makes sense.

A 1.32 would or should spool like a 0.792 single which we already know didnt spool slower than the 0.68 with the efficient compressor wheel and turbine. Jeff's car runs a 1.44 right now and hasnt seemingly lost to the 1.28 while maintaining 48psi of backpressure at 53psi of boost.

I'll grab the dyno sheets to show what I am talking about in a bit.

Aaron