ayousef

Here's the story:

Assume you got Twin Turbos with an a/r smaller than you anticipated, and infact smaller than what you require for your set-up. Assuming that swapping out the turbos for different ones is not an option, how can you compensate for this?

In this case the turbo will be the biggest restriction on the engine thus power/boost will ramp up real quick and tend to die out at the top where backpressure increases.

This follows the concept that more back-pressure = more low-end torque, and less backpressure = more top-end power in a N/A car, just like the size of a camshaft or headers.

Will this hold true and be good enough to compensate, at least a little for a small a/r?

1- High-flow heads
2- bigger camshaft
3- dumping the cats in the bin

Will those three things do a reasonable effect in compensating for shifting the dyno curve a little to the right? Increasing high-end power at the cost of lower low-end torque?

onfire

iTrader: (17)

Why not buy a a set of turbines with the correct AR? High flow heads will make it worse. Dropping cats helps reduce overall back pressure so it will help slightly. A cam could slightly help "crutch" it. Best fix is to fix it correctly to keep the back pressure off the head gaskets.

Zombie

iTrader: (2)

Ideas 1 and 2 won't help, but idea 3 will reduce the after turbo back pressure. Small turbines and housings will cause higher back pressure before the turbo though and there really is no way around that except changing the turbo units.

ayousef

Thats exactly why I posted the thread, because I cant, they are not available, and I clearly mentioned that assuming thats not an option, how come everyone jumped to that solution, I know the best solution is to do that but again.

Your responses contradict, how can a camshaft not help? It will help, and anything you do to reduce backpressure will help, how? Imagine you have a stock LS7 with stock heads, cats, cam, you're pushing 18PSI of boost through the system, all of that air has to squeeze through the small turbine to spin the turbos to compress more air.

Scenario 2: more efficient engine, bigger camshaft, no cats, high-flow heads You now need to run less boost to develop the same power, say 15PSI, so whats happening is the wastegates are now dumping a larger amount of air out the system, and LESS air goes through the turbine to spool up the turbo given the lower boost requirement, thus reducing pressure on the baby housing, at least thats how I understand it (please correct me if im wrong)

Zombie

iTrader: (2)

You are looking at this from the wrong perspective, you have a mass flow issue on the exhaust side, not the intake side. The bigger cam and higher flowing heads will not help much if at all. You can't put more in and see a much of a gain if you can't get what you already have out. You are being limited by your exhaust flow capacity of your turbines/housings.

If your compressors are capable of supplying 1300 hp of air but the exhaust side will only flow 800 hp worth of exhaust, you'll never be able to realize the 1300 HP of your system.

here is an Idea, but I don't know what the results would be as I've never seen it done. Since you have more than enough exhaust energy to spool the turbos it should in theory be possible to add more wastegates to bypass the un needed exhaust thus lowering the back pressure. You should also do everything you can to reduce any back pressure in the exhaust after the turbos, this will lower the back pressure before the turbos and allow for more power.

smokinHawk

iTrader: (48)

another option is to get bigger wastegates and run a low boost setting.

DrTurbo

iTrader: (3)

Simple way of looking at this. Turbine map has to = compressor map ratio before the full HP potential of the comp wheel can be produced. That is it.....if the requirements are not met, then you will always have a handicapped system.

VINCE

iTrader: (1)

First off did you opt for the upgraded TTi X turbos? If so, if you plan on keeping the T56 setup you will make more than enough power to destroy the drivetrain.

Second off, you never stated a rwhp goal. The standard turbos on the TTi X kit will destroy a built T56 drivetrain at full tilt. I have a 408ci TTi X setup and I have made well over 900rwhp b4 my last clutch let go. The power was not falling off at 17.5psi. It was going up as I increased my boost.

Third, ECS is building a setup like yours as we speak using a TTi X setup and they plan to make big power as well. You might want to watch that thread as it unfolds.

Fourth, Forced Inductions dot com has the upgraded turbos you seek in their FI62 line up... BUT once again you already have enough turbo to destroy a T56 drivetrain. If you have a TH400 or powerglide then I would opt for the FI62 turbos from Forced Inductions dot com.

onfire

iTrader: (17)

We jumped on changing to the correct AR as that is the best way to fix it...but if you're stuck, you're stuck.

1. Buy a LPE turbo cam that they use in the 427 package...it's designed for your problem.

2. If you can drop the cubes, that will help also.

3. If you could post the actual comprerssor max flow, turbine size (T3?) and the turbine AR it would help.

ayousef

First of all, thanks for the response bro.

Well i asked for the largest turbine housing they provide on the T3/T4 that comes with the C6 Z06 kit, with an a/r of .81 (I think its custom as well), they said they could not go bigger.

I was initially planning on running this at 6PSI, but Im now getting a Forged 427 Warhawk built, and ill want to max out the turbos. My transmission is the 08 T6060, should be a little stronger than the T56, and im also getting a Spec Dual. Ill swap out the driveshaft, axles, diff, and transmission in the near future. I am not worried about breaking the tranny ill be very careful during shifts, I dont think the tranny would break in-gear though.

My target was 1000rwhp on race gas, and 900rwhp with 93 octane fuel. I am still wondering whats the best CR for the engine, but seems im settling for an 8.5 CR Wiseco pistons and a little milling of the World product heads which should put me at an estimated 8.85:1 CR which sounds good.

Lets not comment about me breaking things with that much power/boost with 93 octane, because im programming the boost controller by vehicle speed to NOT produce that power until like say 170+ MPH, and that would be a very rare occasion for me to go up to that speed etc...

What are your thoughts?

ayousef

1- I was thinking of getting a custom turbo cam grind that should be designed specifically to shift the power curve a little to the right. I have full confidence in my engine builder, so that wont be an issue

2- no option of dropping the cubes now though, you're the second person that suggested that dropping the cubes a little could allow me to make more power with this set-up, can anyone explain why?

3- the only information I have about the turbos is that they are Custom T3/T4 Turbonetics, a/r .81

ninetres

iTrader: (35)

Less cubes = less air moving out of the cylinder = less back pressure

VINCE

iTrader: (1)

Vindication has pretty much the same setup as you. He made over 900rwhp at 14.5psi. He has the same turbos as you. I think you will reach your goal. Just remember it is hot in Dubai!!!

onfire

iTrader: (17)

1. Your engine builder better have mucho turbo experience or you'll be disappointed.

2. Look at a GT35R compressor chart and calculate the airflow vs rpm of a 346ci eengine and a 427ci engine. Now plot both curves on the chart and it will show a better PR for 346ci at higher boost levels and lower temp charges.

Still, lower boost and cubes makes for great torque...keep the rpm under 6500 and it will fly.

3. If they are T3 at 0.81 I would quit worrying. I ran T25's and T3's both on 427 ci. T25's hit the wall at 9.9sc at 141mph...nothing but heat after that.

T3's at 0.81 ran 9.3 at 146mph with more room to go....you don't have a problem unless you want to go wayyy over 20psi.

ninetres

iTrader: (35)

I was reading this thread and the above post just cracks me up. That is just nuts.

VINCE

iTrader: (1)

A TTi X car just ran 151mph this past week.. He still has a lot left in it..

http://forums.corvetteforum.com/show....php?t=2096931

qqwqeqwrqwqtq

They have some turbo experience

ayousef

whats so funny ;

Well thing is, I had a Supercharged C6 Z06 that hit a wall a few months ago, the track was well prepped until 20 meters before the finish line where it was full of dust and actually shined like glass, I wont say the rest (Totalled). That as the worst feeling ever, so this time im playing it right, ill only give the vehicle enough boost that the tires can plant at every individual speed/gear

ayousef

Bro I checked it out and I Have absolutely no idea what the upgraded turbos are, I spoke to George and Nick a few times and I made sure I wanted the biggest turbos they offer and they said the T3/T4 with the .81 if I am not mistaken. You're signature says you got the same, any idea if this is the upgraded turbos you're mentioning?

thx bro!!

onfire

iTrader: (17)

https://ls1tech.com/forums/forced-induction/967186-who-would-you-have-tune-your-car.html