I have a question, currently have an HX40 with 18cm^2 housing which from what I read is about 1.00AR. its a twin scroll t3 housing and currently at 19-20psi.

I found a great deal on a Bullseye BEP .70ar housing that bolts right up to this turbo.

My question is, would a .70ar nondivided t3 housing choke up at the 500whp range? I am looking for sooner spool and more power per psi. I know the .70ar will spool very quick but not sure at what point it would choke and raise EGT's. Some DSM guys are making above 600whp with hx40/.70ar at 30+psi, but not sure if that would apply to a 3.5L. Also, I only rev to 6200rpm, stock heads with built short block.

Any advice would be greatly appreciated, please no 'dreamer thread' comments *caugh*alberto lol jk.

 

I would try and go bigger if you can. The back pressure with a .70 T3 will be up there, even at 400hp.

I will be using a T4 .81 BB on my car this year, and that is larger than anything you can get in a T3 (including the 1.06).

 

I would think it is going to choke it down. Going down that far is a huge bottleneck in performance.

Also, just throw all other cars out the window when you are talking performance. Like you said, it's a different car. comparing a 2.2 liter to a 3.5 liter isn't even close to the same with turbos.

 

In my case, bigger is not an option, I get full boost close to 5,000rpm, and I shift at 6200rpm. The 18cm housing is pretty big. I didnt mention but if it makes any difference, I have a rear mount turbo setup.

 

Yeah I try to not compare but its just hard to believe a 2.#L can make almost 700hp on a turbo, but then choke up on a 3.5L reving 1000rpm less.

 

it's due to CFM of exhaust moving out of that engine. Only so much air can fit down through that small t3 flange.

 

If your compressor is pushing 60lb/min to the intake manifold, all that has to go back out. The only way out is through the turbine housing.

 

Correct, but if thats the case, then a car flowing near 700hp worth of air is supposed to choke with that .70AR housing. no? So no matter what displacement it is, there is still that 700hp worth of CFM exiting out that turbine. I am going off pure logic, I have no basis to how it works technically so if im wrong please correct me so I can understand it.

 

Somewhat on topic. I have asked before but still wondering, you guys think a 2" diameter charge pipe would cause a bottle neck at these boost levels? I run 2" from the turbo to the IC, then 3" from IC to the engine.

The reason I ask is because today, running without methanol and lower timing (about 15degree's) and noticed that at near 6,000RPM my system was pulling back timing due to possible knock or slight detection. My theory is that at this boost level and rpm this turbo is either running out of efficiency, or the 2" charge pipe is becoming a bottle neck causing the turbo to produce more heat.

However, with 2" piping CMyTailsBlink was able to produce 558rwhp on pump, and 623rwhp on q16. With a GT-67 Ball Bearing an a .58 AR housing. So I dont know what to think at this point lol.

 

i believe it has to do with the turbo efficiency islands since we have a larger engine the engine makes power at a lower boost pressure compared to a smaller engine. if you look at turbo maps most of them get there highest airflow from a high boost pressure to maintain good efficiency. while we an get that airflow from a lower boost pressure it puts it at such a low efficiency level that it heats up the air so much that the extra flow isnt showing results. this is all just conclusion i have draw based on what ive seen researching turbos i could be completely off.
as a sidenote a perfect example would be the new efr turbos since i already had one of the compressor maps saved. if you look at the 9180 its max airflow rate is 95 lbs/min but you have to run about 36 psi boost to get 60% efficiency for that, lower boost has lower efficiency.

 

500cfm is the upper limiting flow for 2" piping, so yes your IC piping may be becoming an issue. 2.5" should be good for about 900cfm, and 3" can handle 1300cfm without increased resistance (drag).

You also have to stop comparing other engines to the VQ

Your small turbine may be the reason for knock as well. As the exhaust back pressure goes up, your IAT's will go up as well.

 

I am going to look into upgrading the piping, till then I will lower the boost to high teens or mid teens.

I dont know man, this turbine housing is pretty big, 18cm^2, I dont think this is comparable to other turbines such as garrett or anything. They are designed for diesel applications and all their measurements and specs are different than the norm. I am confident that my knock is not due to exhaust restriction.