Hi guys, I 'am in a crunch with having enough time to work on the car and was trying to make a car show in the middle of march. Do you guys think I coud run and drive my ERL 427 with my old set up t4 flange 76. What scares me is little turbo with alot of cubes and back pressure. Any knowlegable info is appreciated. But try to keep it simple. lol I'm not planning on running it hard like this just want the damn thing back on the road...

 

run a big or big gates and you shouldn't have to worry about back pressure I would think..

 

A T4 turbo on anything over 350ish cubes is asking for trouble. X275 guys are running 88mm T6's on raged edge on 350-370CID engines. If you run a T4 on 427CID engine you will have major BP issues.

 

Maybe you can pull big T4 Turbo on 408ci maybe but on 427ci like Chaunce mentioned big problems.

 

I say put it on and drive it to the show if it's that important. Keep your foot out of it and it will be fine

 

This.

Go to the show, then fix it right by adding another turbo.

 

That 76mm will get blown on that T4 flange. Step up to a T6. I don't trust T4 turbos on anything over 370ci's.

 

That's troubleshooting at its finest!

 

T4 will work just fine driving to a car show.

 

Thanks for the advice. I don't plan on doing anything other than running and breaking in and low rpm driving. Just a question but why wouldn't a waste gate open to atmosphere control back pressure?

 

I'm pretty sure stock48's Nova is running a Stock 6 liter with a T4 Billet S476r and is making ~1100 hp. He's not the only one. If the turbine can flow 1100 HP, its not going to get choked on a 427 that is making less than that.

 

I have 2 buddies running the same T4 GTS76 turbo rated at 1200hp.

first guy has it on a built 378 and he can control boost down low (3psi) and power comes on great with it pulling hard to 7500rpm+. He made 960rwhp.

second guy has it on a built 427 and he can't control boost under 10psi and it comes on violently and then peaks at a lower RPM. It made around 1000rwhp but not the smoothest dyno graph.

The 427 car is a bit undriveable... or at least the owner thinks so as the power comes on instantly.... in a 2800lbs car . I've driven the other car 2800lbs also and the power comes on great.... very driveable. 3rd gear freeway pulls are pretty damn fun and it puts the power down.

twins or T6 with that many cubes

 

I don't get why people don't do this more often. I have seen this work very well in some fast vehicles.. like the banks drag truck, small fast spooling and big gates to control back pressure and boost.. seems like a win win.. comes in sooner and stays controlled all the way up..

 

Because it will choke in the upper RPM range. A diesel doesn't rev to 9,000RPM like gas engines can.

 

ok so use more gates wouldn't cure that? I guess that's the quandary. spend more money on gates or turbo..

 

More gates can control boost down low but the TURBINE will choke on that many cubes, gates nor a huge A/R will help.

 

well thank you for the insight.. I just don't understand how or why it would choke it if you are diverting the excess volume around the turbine to atmosphere, at that point limiting boost as well.. I guess I just cant wrap my head around it yet.
I get that the turbine/housing would become a wall so to speak but if the gates or gate flow enough it would be like open exhaust does it not?. Does that not make sense?

 

I honestly can't believe the sheer amount of people that don't understand that cubic inches don't play nearly as much of a role on turbine capacity as they think. The only real difference cubic inches makes is efficiency in the compressor map.

Its sad how many people here will argue that a 700 HP 427 will choke on a turbine that a 1100 HP 4.8 will not.

 

something worth noting in this debate. its about volume, doesn't matter as much the size as it does the volume created both in and out to make a given power.. rpm plays a much bigger role

 

If this isn't true then how come a 2JZ 3.0L can make 1100RWHP on a 7675 and a LS1 5.7L can't? Because that make cubes get it out of its efficiency zone.