Twin Turbo Build

[illSHOyou]

I am planing a twin turbo build for the SHO. I am still in the early planing stages but I think I have decided on a twin turbo route. I would like to do a low boost stock engine around 5-6 psi. Two 66 Series VATN Aerocharger turbo's are my choice.

I like these turbo's because the engines oil system remains separate from the turbo chargers. My plan of attack is to leave the engine to its great design self, and the turbo's to do their own thing.They do not require a engine oil line ran to the turbo, and can be mounted very low in the engine bay.

BOV are not going to be necessary and the turbos are extremely compact.

My build could experience boost very early:
RPM Boost
1,000 1psi
1,500 2psi
2,000 4psi
2,500 5-6 psi
2,500-7,100 5-6 psi

I want about 275-300 ft lbs across the whole curve and 400hp near redline. To achieve that I will also install a NOS system with a small 50hp shot activated on a window switch around 5,500 rpm to achieve 400hp, And perhaps a large 75-100 hp go baby go option.

This is the plan. Not sure the tranmission is going to like nearly 200 ft lbs at almost idle, but we can find out...

What u guys think?

 

[firebat45]

Tranny should be fine, it doesn't care whether it's at 500rpm or 5000rpm when it comes to torque capacity.

Personally I think you should just forget the NOS and up the boost to the power levels you want, 400 shouldn't need more than 10psi max. Go with a nice EBC if you want to get fancy with boost levels. But, your project your call, just my opinion.

Turbos seem like a decent fit to the engine and your power levels, assuming I found the right compressor maps. How are BOVs not required? No wastegates needed with variable turbos but BOVs are still required, are they not?

 

[somedude_001]

how do you figure you don't need a BOV or recirc valve? are you moving the throttle body before the turbos?

 

[illSHOyou]

how do you figure you don't need a BOV or recirc valve? are you moving the throttle body before the turbos?

Your right I still need a BOV, I just don't need a waste gate with these turbo's.

 

[somedude_001]

Your right I still need a BOV, I just don't need a waste gate with these turbo's.

oh they have internal wastegates?

 

[illSHOyou]

oh they have internal wastegates?

Variable Vane, Acts like a small and big turbo, plus is a wastegate all in one.

 

[MerkXRTurbo]

My build could experience boost very early:
RPM Boost
1,000 1psi
1,500 2psi
2,000 4psi
2,500 5-6 psi
2,500-7,100 5-6 psi

You seem to be a bit confused on how a turbocharger responds. There is boost threshold, and turbo lag, which are two totally different things but often confused. Boost threshold is how long it takes to create positive pressure after hammer down. Turbo lag is how long it takes to get to maximum boost after positive pressure has been created.

The SHO idles at what, 700ish RPM? Even with VATN it is not reasonable to expect a 300rpm boost threshold. With those Aerochargers (in 1st gear - every gear is different) it's reasonable to expect to be through your boost threshold by 2000RPM, and have next to no lag after that! On a well built turbo car it's not uncommon to mash the throttle and have the boost gauge needle stall out at 0 for a fraction of a second (that's your threshold), and then to have it immediately launch up to maximum boost (aka, no lag to speak of)!

Remember that the quicker you spool a turbocharger, the more you have to worry about compressor surge. Surge is when the turbocharger is producing so much more air than the engine can inhale, that it backs up in the pipe and wants to come back out the opposite direction. This can be deadly for a turbocharger and an engine! This is why compressor mapping is important. Fortunately, I believe that Aerocharger makes their compressor maps readily available... many companies do not!

 

[illSHOyou]

You seem to be a bit confused on how a turbocharger responds. There is boost threshold, and turbo lag, which are two totally different things but often confused. Boost threshold is how long it takes to create positive pressure after hammer down. Turbo lag is how long it takes to get to maximum boost after positive pressure has been created.

The SHO idles at what, 700ish RPM? Even with VATN it is not reasonable to expect a 300rpm boost threshold. With those Aerochargers (in 1st gear - every gear is different) it's reasonable to expect to be through your boost threshold by 2000RPM, and have next to no lag after that! On a well built turbo car it's not uncommon to mash the throttle and have the boost gauge needle stall out at 0 for a fraction of a second (that's your threshold), and then to have it immediately launch up to maximum boost (aka, no lag to speak of)!

Remember that the quicker you spool a turbocharger, the more you have to worry about compressor surge. Surge is when the turbocharger is producing so much more air than the engine can inhale, that it backs up in the pipe and wants to come back out the opposite direction. This can be deadly for a turbocharger and an engine! This is why compressor mapping is important. Fortunately, I believe that Aerocharger makes their compressor maps readily available... many companies do not!

Here is the turbo map:


I was thinking compressor ratio 1.3, but after the cooler that may be more like 4 psi into the engine so I might need to move the compressor ratio 1.4 to account for cooler loss. It should give plenty of room to grow and a excellent efficiency. This setup has already been proven on a 3.2L NSX, so we should be good.

Here is some technology of the turbo, some cutaways and a boost chart:

 

[MerkXRTurbo]

We'll just have to wait and see how nonexistent boost threshold is.

Lag, however, will be nonexistent. There is no way it will take 1500RPM to go from 1psi to 6psi. After the turbo gets moving and pushing positive pressure, maximum boost should literally be milliseconds away!