G'day folks

Would it be feasable to make an Evo V twin turbo, would there be any gains in power?

Cheers

Initial Drift

 

dont twin turbo it. It would be sort of pointless...Too much work and money for not enough gains. I wouldn't recommend doing it, even though its possible.

 

Don't bother to twin turbo it... Usually people who drive twin turbo cars end up getting one big turbo to make it faster.

 

Feasible? Yes. You could even have a supercharger and a turbocharger if you wanted.

Gains in power? You can get 700bhp out of a single turbo, so unless you want more than that, then no.

There are 3 types of twin-turbo - Sequential, Parallel and Staged. All have different properties.

 

RAFLMAO

 

There is a lot of point for a twin turbo system:

1. reduced lag and better driveability

2. More power than with a single turbo!! You just have to use the right ones. For example in the Skyline world the strongest ones use twin 2835s I believe, stronger than a T88, but obviously more expensive.

If you have the money and the knowledge, DO IT!! There's only positive aspects if they fit. Cause there isn't a lot of space...

 

Sorry Initial Drift, didn't finish off last night. Below are the 3 setups:

Sequential - small turbo comes on at low revs fllowed by a bigger one at high revs.

Advantages - wide spread of torque, less lag and lower boost threshold.

Disadvantages - swapping over can cause dips in the mid-range but there are ways round it. The FC RX-7 does it nicely as does the Lancia Delta S4 (but with a supercharger and a turbo).


Parallel - 2 equally sized turbos come on together, like in Ferrari F40 and stock Skyline GTR. You can flow more air and get more power and you get slightly less lag than with one bigger turbo with the same flow capacity. As an example a GTR with a single T88 can make 900+bhp, with 2 T88s it can make 1400+bhp. A HKS skyline with 2 GT3540 prototype turbos can make 1600+bhp. Unconfirmed rumours of 2000+bhp even. But what the hell do you want that much power for?

Staged - 2 equally sized turbos (usually), one comes on at low revs and is accompanied by the second at high revs. This gives the high flow ability of the parallel setup but with a lower boost threshold, i.e. more torque low down.


So the choice is up to you. What I'd advise getting (and whether) depends on the application and how much money you have. If lag and low boost threshold aren't major problems and you don't want more than 600-700bhp, then don't bother.

 

Cheers for the info it helped alot.

I'm running a Trust TD06 which is sitting on a custom manifold, could ya run 2 TD06's on a parallel system?

Cheers

 

That's a difficult one. I've never seen it done before but I'll be the first to say that, when it comes to tuning, there's nothing that can't be done. Providing space can be found for the 2nd turbo and its intake and ducting, then in theory it's possible. Whether anyone will do it, I don't know.

However, I have no idea what rpm they will kick in at but probably not until very high, I'm guessing. Where does the rev-limiter kick in? Will your powerband be very wide? Don't know.

In order to select a turbocharger, you must know how much air it must flow to reach your goal. Here's an example using a 5.7 (350ci) chevy engine (remember the airflow will be split between 2 turbos in your case):

You first need to figure the cubic feet per minute of air flowing through the engine at maximum rpm. The formula to do this for a 4 stroke engine is:

(CID × RPM) ÷3456 = CFM

For a 2 stroke you divide by 1728 rather than 3456. Lets assume that you are turbocharging a 350 cubic inch engine. That will redline at 6000 rpm.

(350 × 6000) ÷ 3456 = 607.6 CFM

The engine will flow 607.6 CFM of air assuming a 100% volumetric efficiency. Most street engines will have an 80-90% VE, so the CFM will need to be adjusted. Lets assume our 350 has an 85% VE.

607.6 × 0.85 = 516.5 CFM

Our 350 will actually flow 516.5 CFM with an 85% VE.

Presure Ratio

The pressure ratio is simply the pressure going in, compared to the pressure out of the turbocharger. The pressure going in is usually atmospheric pressure, but may be slightly lower if the intake system before the turbo is restrictive, the inlet pressure could be higher than atmospheric if there is more than 1 turbocharger in series. In that case the inlet pressure will be the outlet pressure of the turbo before it. If we want 10 psi of boost with atmospheric pressure as the inlet pressure, the formula would look like this:

(10 + 14.7) ÷ 14.7 = 1.68:1 pressure ratio

Temperature Rise

A compressor will raise the temperature of air as it compresses it. As temperature increases, the volume of air also increases. There is an ideal temperature rise which is a temperature rise equivalent to the amount of work that it takes to compress the air. The formula to figure the ideal outlet temperature is:

T2 = T1 (P2 ÷ P1)0.283

Where:
T2 = Outlet Temperature °R
T1 = Inlet Temperature °R
°R = °F + 460
P1 = Inlet Pressure Absolute
P2 = Outlet Pressure Absolute

Lets assume that the inlet temperature is 75° F and we're going to want 10 psi of boost pressure. To figure T1 in °R, you will do this:

T1 = 75 + 460 = 535°R

The P1 inlet pressure will be atmospheric in our case and the P2 outlet pressure will be 10 psi above atmospheric. Atmospheric pressure is 14.7 psi, so the inlet pressure will be 14.7 psi. To figure the outlet pressure add the boost pressure to the inlet pressure.

P2 = 14.7 + 10 = 24.7 psi

For our example, we now have everything we need to figure out the ideal outlet temperature. We must plug this info into the formula to figure out T2:

T1 = 75
P1 = 14.7
P2 = 24.7

The formula will now look like this:

T2 = 535 (24.7 ÷ 14.7)0.283 = 620 °R

You then need to subtract 460 to get °F, so simply do this:

620 - 460 = 160 °F Ideal Outlet Temperature

This is a temperature rise of 85 from 75 °F .

Adiabatic Efficiency

The above formula assumes a 100% adiabatic efficiency (AE), no loss or gain of heat. The actual temperature rise will certainly be higher than that. How much higher will depend on the adiabatic efficiency of the compressor, usually 60-75%. To figure the actual outlet temperature, you need this formula:

Ideal Outlet Temperature Rise ÷ AE = Actual Outlet Temperature Rise

Lets assume the compressor we are looking at has a 70% adiabatic efficiency at the pressure ratio and flow range we're dealing with. The outlet temperature will then be 30% higher than ideal. So at 70% using our example, we'd need to do this:

85 ÷ 0.7 = 121 °F Actual Outlet Temperature Rise

Now we must add the temperature rise to the inlet temperature:

75 + 121 = 196 °F Actual Outlet Temperature

Density Ratio

As air is compressed it becomes more dense. Therefore, to compare the inlet to outlet air flow, you must know the density ratio. To figure out this ratio, use this formula:

(Inlet °R ÷ Outlet °R) × (Outlet Pressure ÷ Inlet Pressure) = Density Ratio

We have everything we need to figure this out. For our 350ci example the formula will look like this:

(535 ÷ 656) × (24.7 ÷ 14.7) = 1.37 Density Ratio

Compressor Inlet Airflow

Using all the above information, you can figure out what the actual inlet flow in in CFM. Do do this, use this formula:

Outlet CFM × Density Ratio = Actual Inlet CFM

Using the same 350ci blck in our examples, it would look like this:

516.5 CFM × 1.37 = 707.6 CFM Inlet Air Flow

That is about a 37% increase in the mass of air going into the engine and the potential for 37% more power. When comparing to a compressor flow map that is in Pounds per Minute (lbs/min), multiply CFM by 0.069 to convert CFM to lbs/min for atmospheric pressure.

707.6 CFM × 0.069 = 48.8 lbs/min

Now you can use these formula's along with flow maps to select a compressor(s) to match your engine. You should play with a few adiabatic efficiency numbers and pressure ratios to get good results. For twin turbos, remember that each turbo will only flow 1/2 the total airflow.

 

Once again cheers for the info, more than enough.

I've seen that GT's sporting twin turbo's either have one common wastegate say a HKS 60mm and I've seen others with two, which is better?

Cheers

Initial Drift

 

if you run the turbos parallely you only need one, for the other applications you need to to have them run on different boost levels. I would say having sequintial turbos is the best thing for ultimate performance, i.e. good lap times.

 

Is it any good to install a pressure guage?

 

no , no gauge needed lol

 

jeepers this is old