Turbo Tuning

Don Fiveolio · May 31, 2006

Alright, before I get started, let me say that I searched a lot of threads to try and find more information about the questions that is about to be asked. And although there is a lot of details about how much boost somone is generating, the main answer that I have been searching has failed to present its self. Basically, my questions is:
How in the heck do you tune a turbocharger. When it comes to superchargers, I understand that you can generate more boost by changing out the pulley and dailing in the fuel pressure. But a turbo is run on exhaust gases.
There is a cat on here that built a twin turbo LX Monster that was featured in a Stang mag and a few other places. When he built it and posted up the numbers here, he mentioned that he had not turned it up all the way. So what gives? Please enlighten me.

Feel free to get technical

Thanks :SNSign:

bluevenom867 · May 31, 2006

Blow off valves,wastegates,ect.

you control turbos by bleeding off the differant gases,and to some extent the cases and impellers/trims,how ever thous would be more for if you were trying to "up grade" a turbo IMO.

Don Fiveolio · May 31, 2006

So, you're saying that post install tunes deal mainly with the wastegate, being that you can set it to open and release pressure once it hits a certain boost level?

So if you are in top gear and have hit max boost level that the system is tuned for, does that mean that the wastegate stays open during the duration of WOT?

Thanks

bluevenom867 · May 31, 2006

don herberto said:
So, you're saying that post install tunes deal mainly with the wastegate, being that you can set it to open and release pressure once it hits a certain boost level?

So if you are in top gear and have hit max boost level that the system is tuned for, does that mean that the wastegate stays open during the duration of WOT?

Thanks

Im not exactly sure as I dont have alot of experiance with turbos,but I would assume it would stay open just enough to keep the desired boost level.

88_GT_5_oh · May 31, 2006

its with the wastegate, wastegates control the amount of exhaust that reaches the turbine housing, all a wastegate is is a valve witha spring, the spring has tension onit and once enough presure is made in the exhaust side it opens up the wastegate and bleeds off excess gases, you can up the boost with a boost controller or put a higher rated spring in the wastegate. different turbuine houses will make the boost come in lower or higher. witha bigger housing you could make it so the boost doesn't come in till say 4000 rpm , or with a smaller housing you can make full boost at like 2000 rpm

thats my half assed discription

89Notch · Jun 1, 2006

Are you talking about tuning the turbo or tuning the engine? I don't really know what tuning a turbo is but his explanation is pretty good about how to adjust the boost with the wastegate. I am assuming he is referring to tuning the engine by adjusting timing and fuel pressure. That is pretty much the same as a s/c... more fuel and less timing with boost and trying to find the ideal mix for more power and safe use

Flavadave4 · Jun 1, 2006

don herberto said:
Alright, before I get started, let me say that I searched a lot of threads to try and find more information about the questions that is about to be asked. And although there is a lot of details about how much boost somone is generating, the main answer that I have been searching has failed to present its self. Basically, my questions is:
How in the heck do you tune a turbocharger. When it comes to superchargers, I understand that you can generate more boost by changing out the pulley and dailing in the fuel pressure. But a turbo is run on exhaust gases.
There is a cat on here that built a twin turbo LX Monster that was featured in a Stang mag and a few other places. When he built it and posted up the numbers here, he mentioned that he had not turned it up all the way. So what gives? Please enlighten me.

Feel free to get technicalThanks :SNSign:

You first need to understand how a turbo works.....It runs on the exhaust gas and force of air exiting the motor, however i does not recirculate the air through your motor. The exhaust merely turns a turbine on a shaft which turns a conpressor that is forcing outside air into the system.....exhaust takes its normal exit out the exhaust.

You tune a turbo with fuel and timing

Don Fiveolio · Jun 1, 2006

Thanks everyone for your contributions thus far.

89Notch said:
Are you talking about tuning the turbo or tuning the engine? I don't really know what tuning a turbo is but his explanation is pretty good about how to adjust the boost with the wastegate. I am assuming he is referring to tuning the engine by adjusting timing and fuel pressure. That is pretty much the same as a s/c... more fuel and less timing with boost and trying to find the ideal mix for more power and safe use

You pose a good point here. I guess the more thorough question here would be in regard to tuning the engine with the turbo. Low compression pistons with retarded timing seems to be the formuila that works best. Or is it low compression pistons with "standard" timing and nominal compression (9.0:1) pistons with retarded timing?

Thanks :SNSign:

bluevenom867 · Jun 1, 2006

don herberto said:
Thanks everyone for your contributions thus far.

You pose a good point here. I guess the more thorough question here would be in regard to tuning the engine with the turbo. Low compression pistons with retarded timing seems to be the formuila that works best. Or is it low compression pistons with "standard" timing and nominal compression (9.0:1) pistons with retarded timing?

Thanks :SNSign:

Everyone says the lower compressino is best,but really more compression should make it spool faster and make more power.As long as it can handle it,more compression will always win.

There was thread back were I was talking about a blower on our previous 12:1 compression 408 with a fogger on top,that would have been insane,but if it could have handled in it would have probably made like 1300hp on 15psi (my theory is use the blower to simply cram in more nitrous,haha).

millhouse · Jun 1, 2006

bluevenom867 said:
Everyone says the lower compressino is best,but really more compression should make it spool faster and make more power.As long as it can handle it,more compression will always win.

There was thread back were I was talking about a blower on our previous 12:1 compression 408 with a fogger on top,that would have been insane,but if it could have handled in it would have probably made like 1300hp on 15psi (my theory is use the blower to simply cram in more nitrous,haha).

And once you throw pump fuel into the equation....lowering the compression allways seems to win out.

bluevenom867 · Jun 1, 2006

millhouse said:
And once you throw pump fuel into the equation....lowering the compression allways seems to win out.

I was actualy assuming more of an unlimited octane senario.....but yea,your right for pump keep the compression low

Brantley · Jun 1, 2006

9.0:1 compression is a pretty decent compromise for power and street use with pump gas. Yes, more compression is better, but it makes tuning it more difficult and less forgiving to errors.

A wastegate doesn't know anything about WOT. All the WG knows is whether or not boost pressure is greater than or less than the spring pressure in the WG. If the pressure is higher than the spring pressure, the WG will open and continue to stay open until manifold pressure is less than or equal to the WG spring pressure. WG then closes, and the process repeats. I guess you think of it as a mechanical pulse width modulated valve.. it is referenced off the manifold. The wastegate bypasses air around the turbine wheel, thus controlling the speed of the turbo.

A blow off valve does exactly that. It releases pressure in the intake tract to the atmosphere when the throttle blade closes. This prevents air from reverting back into the compressor wheel in the turbo, preventing turbo damage and slightly improving spool up times when you get back on the throttle.

A bypass valve is very similar to a blow off valve, except that it recircuates the air back into the intake tract.. usually used in a mass air type management system where the air has already been metered by the MAF.

Don Fiveolio · Jun 2, 2006

Thanks everybody for all of the extra information. This is great since my brain has been frying on this matter for the longest time. There is another thread that's posted in 5.0Tech where a guy is showing pics of the entire build all the way to the turbo install so now there's more to go off of. Thanks again eveyone for your insight in this

I always thought Supercharging was cool, but the jet like sound of a turbo is so much more satisfying when flying by somone on the track.

:SNSign:

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