Im trying to get some more info on what a turbo or twin turbo system, if you have twin turbo with 6lbs boost, it is not going to be 12lbs boost since you have twin turbo somebody was trying to tell me that but I did not think so, am I right?

How do you give the engine the fuel that it neads when the boost is up because it can have that in your chip because it would be to rich if you dont have the boost up?

I know it would be better to take some timeing out when the boost is up too how would you do that?

How much power can the stock 730 computer handel? because I see most guys with turbos go with after market computers but Im not looking for 1000hp, much less then that maybe 500-600hp.

What is the smallest turbo that you can use on a V8 twin turbo system? was looking at the T3/T4 turbos.

How much boost can you run with out the intercooler, I know it will be different from turbo to turbo I know that the bigger turbos do not heat the air as much as the little ones but you will have more turbo lag, but how small can the turbo be with out intercooler?

Thanks for any info.
Jay

 

On a twin turbo system, the boost does not douple, just the airflow. Boost is a measure of air restriction in the intake manifold. Two turbos pushing 50 cfm each at 20 psi, means that there is 20 psi of boost but 100 cfm of flow.

Most EFI based fuel injection systems, whether factory or aftermarket, used in forced induction applications utilize a Manifold Air Pressure (MAP) sensor. This sensor tells the ECm what the manifold vacuum or pressure is, and the ECM uses this to help determine fuel enrichment as needed. Most factory ECM's will not recognize any significant manifold pressure, and you also need either a 2 or 3 bar MAP sensor. MAF systems can be made to work with low boost forced induction systems, but they are not preferred.

The MAP sensor is also used by the ECM to handle ignition retard under boost.

Determining the appropriate compressor for you application depends on how much boost you want to run and how much power you want to make. Knowing those two factors can help you identify which compressor will fit your needs. Wihout intercooling, I'd recommend keeping the boost below 10psi or so, but that's just a generality. A single 60 would br good up to around 600-650 crank hp. It takes approximately 10 lbs of air/minute to make 100hp.

 

Thank you for that info Monty.
Just as I thought about the boost but I did not know about the air flow, does it make difference when you go from 50cfm to 100cfm in power?

I guess that you cant use the 730 computer even if it is a MAP computer since it does not have 2 or 3 bar MAP, I have seen some boxs that sends more volts to your fuel pump when the boost goes up do you have to have that too?

Guess Im thinking about 8-10 to make 500-600HP, and you are right to make that you just nead one but I just like the twin turbo look, I was thinking about getting some turbos that are on the Buick GN with internal wastgate, you think that would do it?

Again thanks for that info Monty

Jay

PS was just thinking about a TV ad, there was this guy under his car talking to his new born girl that was under it too, it looked like it could be you and your little girl if the car was a corvette....lol

 

The flow, expressed in lbs/min determines the hp level the turbo(s) will support. As I mentioned in the previous post, it takes approximately 10 lbs of air/minute to make 100 hp. So going from 50lb/min to 100lb/min means you go from 500hp potential to 1000hp potential, as a generalization.

I'm not an expert on using the factory ECM's, but I know alot of guys are using the Typhoon/Cyclone ECM's because they are designed to be used with forced induction. Maybe someone with more knowledge about the factory ECM's knows if you can reprogram the 730's for forced induction. I'd guess you can since there are plenty of guys running centrifugal superchargers with factory ECM's, although alot of them use FMU's - which is not ideal in my opinion.

The fuel pump controllers you are referring to are commonly used. Most aftermarket fuel pump companies like Aeromotive, Weldon, Magnaflow, etc offer and recommend these. MSD also makes one. Using these help extend the life of the fuel pump because the fuel pump isn't running full speed all the time, the controller regulates the voltage/fuel pump speed based upon engine rpm, etc. I use two Aeromotive 1000hp pumps, each controlled by it's own fuel pump controller.

Even though I have a custom TT engine, the fact is that a large single turbo is almost always more efficient than two smaller turbos.

It's a popular internet myth/misconception that small twin's spool up quicker than a large single, but people forget that you're only routing half of the exhaust energy through each turbo on a TT system. Another fact that doesn't support the TT spool advantage myth is that a larger T76 turbo will start producing boost at around 36000 shaft rpm, or even a T88 at 33000 shaft rpm whereas a smaller 60-1 won't start to produce boost until 46000 shaft rpm for example.

Generally, a larger compressor will also have a wider efficiency range with the T76 being usable from around 25-85 lbs/min, while a 60-1 is good for 15-55 lbs/min, but you do have two on a TT setup.

In either case, with a large V8 engine, and the appropriate converter/gear ratio, spooling up an appropriate sized turbo is not a problem.

On a V engine, twins do make more sense though because there is generally a shorter distance between the exhaust valves and the turbines, whereas with a single you either have to run one exhaust bank over to the other side, or run each exhaust bank longer and merge then together. The shorter the distance between the exhaust valves and the turbine, the less heat gets wasted into the atmosphere rather than driving the turbine. Heat accounts for about 70-80% of the energy that drives the turbo, not the velocity of the exhaust gasses coming out of the exhaust port.

Often times, two smaller turbos are actually easier to package over a larger single. Not only is the turbo itself physically smaller, but the plumbing doesn't have to be as large either.

But "twin turbos" does sound more exotic or trick over saying you have a single, so that might count for something to some people.

Either way will work just as well as the other, and if everything is properly sized and attention is paid to efficiency, both will have very similar spool and rpm range performance.

All of this is a generality, that is why I qualified my previous statement by comparing specific commonly used turbo's in TT applications versus commonly used turbos in a single turbo application. Anyone that can read a compressor map can see this.

The turbine is what determines as what engine rpm the compressor is most effective and efficient. Since the compressor is not directly connected to the crankshaft like a supercharger, the turbine is what determines the engine rpm vs boost and spool characteristics. You can take the same compressor and it will act completely different in terms of it's effective engine rpm range and spool characteristics based upon what turbine it's attached to. That's why a .63 turbine equipped turbo will spool up much quicker at a lower engine than a 1.05 turbine equipped turbo. Unfortunately, that same .63 equipped turbo will become inefficient at a lower engine rpm than the larger turbine equipped turbo.

As for getting longevity out of the turbo, that's based upon properly applying a turbo for the specific application, and ensuring adequate clean oil to the turbo, as well as common sense. Using too small of a turbo for a specific application will result in overspeeding the turbo, resulting is catastrophic damage. too large of a turbo and the compressor could experience destructive surging. Lubricating the turbo with contaminated or insufficent oil flow will also hurt the turbo. You also want to take care in not spooling the turbo uop before the engine oil reaches normal operating temperature, and you also want to cool the turbo down with low load oil flow for a brief period of time after usage to prevent coking. Properly applied to the application, a turbo is desingned for the heat range it will experience. Turbo's durability and reliability is proven to be superior to other forms of supercharging if basic rules of care are follwed.

As for the cost of a large single turbo versus that of a pair of smaller turbos, the price difference is less than you'd think. Price the cost of a T76 vs. a pair of 60's and the larger turbo is nearly as much as the total cost of the two smaller one's, the same is true for the larger wastegate required for a 72+ turbo vs the wastegates required for a pair of smaller turbos. Price it out and the difference isn't significant considering the overall cost of a turbo system, the difference is just being a few hundred dollars.


The GN turbo's will work well and will fit your stated needs pretty well.

I think you're referring to a Valvoline commercial, my wife says the same thing!

 

Hey MrJay, if your really thinking of a Twin Turbo power adder as a solution, then you should check out Maximum Boost Its by Corky Bell, has a lot of info on Turbos and how to build then including all the info you need with aftermarket EFI's and stock ones. I hope this helps :yesnod:

 

Thanks Monty that clears a lot, I did not read your other post right about the air x HP.
Ok I see why you would want to run a fuel pump controller, I guess when you have 1200hp you nead 2 fuel pumps but if I do this I dont think I will nead 2 maybe the next project if this goes well...lol
Guess I was one of them that thought the small TT would have less lag, but now I see that it is not so but you are right it is much harder to plum if you have to go from one side to a nother, I was thinking about doing something like Grape Ape has one his Camaro he has two over the valve covers or something like that then you dont have to plum that much just one to the old exhaust and one to a intercooler and then to the TB or just to the TB like he did but then later get a intercooler.
Yes you are right it is more fun to say that you have TT and it looks so much better too.
I have been trying to read some turbo maps but it looks like you have to really study them to be good a reading them..then there is so many other things, I can see why a turbo with a smaller compressor will peak out sooner then a big one but will that not all so make the turbo come in later because it is bigger or is it just that you wont get that much at low rpm since the wheel is so big?
I was reading something that was saying that a bigger turbo wont head the air as much since it does not compress it as much under low boost I guess it would be better to get a bigger one if you are not going to put a intercooler in it until later then you can turn up the boost to.
I see there is a lot of do and dont when you have them if you want them to last.
Good to hear that you think the GN turbos will do ok for what I want to do do you know kind they are T3 or T4?

Light84vette I think I will have to order that book today.


Everybody thanks
Jay

 

You could go to www.Turbochargers.com They got cheap T3/T4 Turbos, I think they got a 300HP rated Turbo for about $400, could be a little bit more. I think that would help you get to the 600HP level. Also ARe you going to mount the turbos above? Or below like the callaways? :confused:

 

I was thinking about putting them on top so I dont have to have a oil pump like they had to have, I was going to see if I could not make it look something like what Grape Ape Racing has.
I have a guy that is really good making header and I was going to get him to do them for me.

Grape Ape home page
http://www.grapeaperacing.com/GrapeA...aro/turbos.cfm

Jay

 

T3