Twin turbo guys any regrets?

[graf101]

I am probably wrong, but the cO2 seems to help alleviate the issue.

[ttshovel]

Originally Posted by graf101

I am probably wrong, but the cO2 seems to help alleviate the issue.

That's what I was referring to. Using dome pressure to pin it shut. That way it doesnt crack open at all while building boost

[dreksnot]

Ok, sure. With big turbos and cruise RPMs, you ain't gonna get the instant torque hit as the top mount SC has when nailing the go pedal. But, you also ain't going to get this kind of high (select-able) boost either. This was a cruise speed 3rd gear throttle smash. Took 4.5sec to get to peak boost (20.9psi).

My smaller turbos were quite quick when spooling on a stock cube LS3. Very fast to torque up. It's all about how the turbos are matched to the motor, and can be quite fast to spool if set up correctly (like my old LS3 setup). With the bigger turbos and more cubes, it does take a bit longer unless I start the throttle smash at >3,500rpms.

[stevieturbo]

Originally Posted by blake-b

To expand upon Stevie's request. Here are two logs. The first is a twin turbo log where the purple Kpa line is boost. This was a 427 with twin EFR7670s (57/58mm turbos). It seemed to never be out of boost and felt very OEM like and was as close to no lag as you could get. Although not as fast as a PD blower, it went to 200kpa (~14.5#) in less than 1/10th of a second.

The second graph is from my ZR1 with a positive displacement blower. Again, the purple line is kpa.

In the sections above the kpa, the green line is throttle. You can see with the turbos the boost lags a little behind but the PD blower throttle and kpa rise in unison. That's no lag at it's finest.

427 with those is bound to be fun. A lot would say they're too small, but it is amazing what the OEM do these days with what seem like ridiculously small turbos. The aftermarket never really seems to follow that path though.

Although it's hard to tell on the graph, top one only looks to show a WOT hit around 5k ?
How is the 427 going WOT at say 3500rpm too ?

The blower graph much lower say 3700rpm ?

Sometimes boost traces alone cannot do a setup justice either though. Even a lot of graphs I've seen of small twins....the boost trace makes them look lazy, but no doubt they're making a lot of torque, even if spool doesnt seem super fast.

[blake-b]

Originally Posted by stevieturbo

427 with those is bound to be fun. A lot would say they're too small, but it is amazing what the OEM do these days with what seem like ridiculously small turbos. The aftermarket never really seems to follow that path though.

Although it's hard to tell on the graph, top one only looks to show a WOT hit around 5k ?
How is the 427 going WOT at say 3500rpm too ?

The blower graph much lower say 3700rpm ?

Sometimes boost traces alone cannot do a setup justice either though. Even a lot of graphs I've seen of small twins....the boost trace makes them look lazy, but no doubt they're making a lot of torque, even if spool doesnt seem super fast.

Here is a graph of WOT around 3500 with EFR7670s. The blower was around 3700.

I remember on yellowbullet where guys said I would only make 800whp with them and I made something like 1063whp.

Dreksnot has the same turbos (AGP 65/65) I later went to. They didn't feel laggy but they weren't anything like the smaller ones.

[stevieturbo]

Sometimes it makes me want to try smaller turbos, I've 364's on my 383. But deep down I know I want bigger turbos lol

It's just how much bigger and at what price.

[HOJO]

Just curious, you guys running bigger cubes, where are you mounting your turbos and what are you doing for exhaust manifolds? Are factory LS3 manifolds sufficient on say a 416 or 427 build, referring to a decent street build. You guys have some wicked machines that’s for sure.

[dreksnot]

Originally Posted by HOJO

Just curious, you guys running bigger cubes, where are you mounting your turbos and what are you doing for exhaust manifolds? Are factory LS3 manifolds sufficient on say a 416 or 427 build, referring to a decent street build. You guys have some wicked machines that’s for sure.

Mid-mount with my twins using Huron's headers. The factory LS3 are strong enough to hold up and will probably be capable of 1,000whp or more. So, I'm saying if <1,000whp LS3 is fine, >1,000whp look for more flow.

[graf101]

A bit off topic, but wanted to ask, as some of you guys have already upgraded the motors from the stock motor.

What can I get for my complete ls3 longblock? I have a new Thompson Dart 427 waiting to go in, so I am ready to sell the stock ls3. Any idea on a range I should be looking at?

[stevieturbo]

Originally Posted by dreksnot

Mid-mount with my twins using Huron's headers. The factory LS3 are strong enough to hold up and will probably be capable of 1,000whp or more. So, I'm saying if <1,000whp LS3 is fine, >1,000whp look for more flow.

It's a topic that has been brought up many times. And the most convincing reference I've seen people say, although it relates to truck manifolds which are essentially the same. That many years ago the Ohio Boys made 2000hp on truck manifolds.

Is it likely the most efficient way to do it ? Probably not. But I do not see the factory manifolds being any real limitation, even fairly well beyond 1k.
And when they're so easy....it's a no brainer to keep using them.

[mrimpala02]

I think the another reason to move to aftermarket manifold is when you get into a 6-bolt head the stock manifolds need some massaging. It's possible to modify, but many choose this as an excuse to upgrade.

[ttshovel]

Originally Posted by graf101

A bit off topic, but wanted to ask, as some of you guys have already upgraded the motors from the stock motor.

What can I get for my complete ls3 longblock? I have a new Thompson Dart 427 waiting to go in, so I am ready to sell the stock ls3. Any idea on a range I should be looking at?

I sold mine for 5k with a cam and ported heads. Pan to intake. I had 9k miles on it though