# how do you make boost kick in sooner?



## docterelliott (Sep 29, 2007)

speaking for turbos at least...how would you make the boost kick in at a lower rpm? smaller turbo? program it to? still learning about turbos.


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## akid420 (Apr 23, 2009)

search Google "removing/reducing boost lag"


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## docterelliott (Sep 29, 2007)

k all people talk about in regards to turbo lag when you google it is theorys of ways to make the turbo spool up like if it were a sc using other sources like electric motors and injecting fuel directly into the turbo. not what i was talking about. let me put it this way...my buddys mk5 spools up almost immediatly it seems. why and how is what i want to know. i know he doesnt do any of those concepts people talk about trying to invent to get rid of turbo lag.


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## 2.0TRabbit (Oct 29, 2004)

*turbo*

His turbo spools up quick due to small size.


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## GinsterMan98 (May 19, 2008)

Bingo, you could try and put a smaller housing on the exhaust side, that would make it spool sooner.


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## toy_vw (Feb 11, 2006)




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## CDJetta (May 11, 2004)

Tubular manifold, twin scroll turbo, equal length runners, then get a mid sized hot side. Should spool pretty early and still make power up in the top end unlike stock turbos. Or just pump a 50-100 shot of nitrous through the motor to spool a really really big hotside turbo.


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## dub_slug (May 12, 2008)

Twin scroll turbine housing and this: 
http://www.spracingonline.com/projects/


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## TBT-Syncro (Apr 28, 2001)

CDJetta said:


> Tubular manifold,


 spool later than a log manifold.


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## docterelliott (Sep 29, 2007)

thanks! good info. by "equal length runner" your referring to the downpipe right? cause i know tubular manifolds are sometimes referred to as equal length runners. didnt know if you accidentally wrote that twice or not. also what size roughly would be a "mid size" hot side? im assuming thats the side of a twin scroll turbo that recieves the exhaust gas right? know a good place to find turbos like this?


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## VDUBIN (Jun 28, 2001)

docterelliott said:


> thanks! good info. by "equal length runner" your referring to the downpipe right? cause i know tubular manifolds are sometimes referred to as equal length runners. didnt know if you accidentally wrote that twice or not. also what size roughly would be a "mid size" hot side? im assuming thats the side of a twin scroll turbo that recieves the exhaust gas right? know a good place to find turbos like this?


equal length runner is referring to the exhaust manifold having the same length runners from the flange to the turbo to equalize the exaust pulses at the turbo. 

the "hot side" is the side that the exhaust goes through and the size is determined by the motor and mods done to it.

a twin scroll housing is a turbo housing that has 2 seperate paths for the exhaust to reach the exhaust turbine and thereby reduce the potential for back pressure. these are also called divided exhaust housings.

here's a good pic of a twin scroll turbo...









and the article it came from...  modified mag

the prob with the item that dub_slug posted is that you need a merged or log manifold. if you have a truly divided manifold then you will stall your motor as half the motor cannot breathe.


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## EL DRIFTO (Jul 11, 2004)

dub_slug said:


> Twin scroll turbine housing and this:
> http://www.spracingonline.com/projects/


i've been thinking if a 12v will spool up a GT4094 1.19AR by 3800 that a 16v would do the same with it & a log manifold, ever since i saw this opcorn:


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## dub_slug (May 12, 2008)

EL DRIFTO said:


> i've been thinking if a 12v will spool up a GT4094 1.19AR by 3800 that a 16v would do the same with it & a log manifold, ever since i saw this opcorn:




I've been wanting to try one of these out very badly! It's about the same price as upgrading from journal to dual ball bearing


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## Raddoboy (Sep 18, 2002)

More displacement, smaller hotside, LOG manifold( tube mani actually adds lag due to lack of thermal efficiency, more hp tho because it can actually flow more), ballbearing turbo, nitrous. Pick one or more and youll see full boost quicker.


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## WeeZFan69 (Aug 3, 2003)

electronic boost controller will help you spool faster... well maybe a little faster and quite a bit harder. There is a biggg difference between 7psi on just my WG spring, and when I set my electronic to 7 psi. WG spring makes for very slow spool up


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## vergessen wir es (May 12, 2010)

X2 WeeZFan69 say.

When a waste-gate only has a spring it will open progressively so you start bleeding exhaust before final boost is reached. That slows spool somewhat. A WG with an EBC cannot open before the 'spring' setpoint is reached so all exhaust is available to the turbo.


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## clarksongli (Nov 4, 2003)

Variable Veins Systems.

My personal favorite is the VGT system from Holset.

Not your typical Variable system, but the design of it is much more robust to hot EGTs....


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## Flipdriver80 (Jul 17, 2004)

TBT-Syncro said:


> spool later than a log manifold.


not quite... do some research my friend. depends on the turbo. tubular manifold flows more air more efficiently which will give you less lag. log manifold tend to build more back pressure BEFORE the turbo. tubular manifolds flow more which will increase turbo boost at a lower rpm.


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## TBT-Syncro (Apr 28, 2001)

Flipdriver80 said:


> not quite... do some research my friend. depends on the turbo. tubular manifold flows more air more efficiently which will give you less lag. log manifold tend to build more back pressure BEFORE the turbo. tubular manifolds flow more which will increase turbo boost at a lower rpm.


i think you should do some research. 

tubular or long runner manifolds will typically flow more air, but shorter log manifolds will spool sooner due to their shorter runners and less thermal pumping loss (almost all of the energy that drives a turbo is heat, and not from volume  ).

also dont forget that pressure differential is what creates efficiency, so when you have more pressure on the hot side, then your system becomes even more efficient.


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## Raddoboy (Sep 18, 2002)

TBT-Syncro said:


> i think you should do some research.
> 
> tubular or long runner manifolds will typically flow more air, but shorter log manifolds will spool sooner due to their shorter runners and less thermal pumping loss (almost all of the energy that drives a turbo is heat, and not from volume  ).
> 
> also dont forget that pressure differential is what creates efficiency, so when you have more pressure on the hot side, then your system becomes even more efficient.


yup.


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## WeeZFan69 (Aug 3, 2003)

TBT-Syncro said:


> i think you should do some research.
> 
> tubular or long runner manifolds will typically flow more air, but shorter log manifolds will spool sooner due to their shorter runners and less thermal pumping loss (almost all of the energy that drives a turbo is heat, and not from volume  ).
> 
> also dont forget that pressure differential is what creates efficiency, so when you have more pressure on the hot side, then your system becomes even more efficient.


But by on the pressure side you mean before the turbo? Cause pressure after the turbo on the exhaust is only going to make you loss power correct?


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## TBT-Syncro (Apr 28, 2001)

WeeZFan69 said:


> But by on the pressure side you mean before the turbo? Cause pressure after the turbo on the exhaust is only going to make you loss power correct?


correct.

as it is lowering pressure differential.

in fact, boost control used to be done simply by running smaller exhaust systems that would choke the system. although it is possible to control your wastegate by running your signal line to your exhaust system and using gas pressure to control boost pressure.


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## Flipdriver80 (Jul 17, 2004)

TBT-Syncro said:


> i think you should do some research.
> 
> tubular or long runner manifolds will typically flow more air, but shorter log manifolds will spool sooner due to their shorter runners and less thermal pumping loss (almost all of the energy that drives a turbo is heat, and not from volume  ).
> 
> also dont forget that pressure differential is what creates efficiency, so when you have more pressure on the hot side, then your system becomes even more efficient.


turbo's use backpressure to build boost yes. BUT if the volume of your cast manifold has less volume than your tubular manifold you will build backpressure quicker, but you won't be flowing as much air through your manifold, which in turn creates an unnecessary bottle-neck in the turbo spooling process. you want that manifold to be as free flowing as possible. a larger turbo requires it. a small turbo will have no problem spinning with a cast manifold because it simply does not need the type of volume a larger turbo does.


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## Flipdriver80 (Jul 17, 2004)

WeeZFan69 said:


> But by on the pressure side you mean before the turbo? Cause pressure after the turbo on the exhaust is only going to make you loss power correct?


yes, which is why having a 4" exhaust out the hood of a race car which is turbo charged has little effect on its power. all the back pressure is before the turbo. so you can run whatever size you want for exhaust as long as it doesn't stifle the exhaust.


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## B4S (Apr 16, 2003)

Flipdriver80 said:


> turbo's use backpressure to build boost yes. BUT if the volume of your cast manifold has less volume than your tubular manifold you will build backpressure quicker, but you won't be flowing as much air through your manifold, which in turn creates an unnecessary bottle-neck in the turbo spooling process. you want that manifold to be as free flowing as possible. a larger turbo requires it. a small turbo will have no problem spinning with a cast manifold because it simply does not need the type of volume a larger turbo does.


Dude, it's the energy from the heat of the exhaust gases...not the volume. Ya gotta read .


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## B4S (Apr 16, 2003)

In regards to the quick spool of the MkV, not only is it due to small-sized turbos, ME9 has a wonderful thing called "lean spool" maps. No clue how it works, but anyone familiar with the system can manipulate it to help larger turbos spool up quicker.


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## Raddoboy (Sep 18, 2002)

Turbochargers work off HEAT expansion. As far as back pressures and exhaust size. It matters. Yes there is back pressure from the head to the turbo, which affects engine breathing. Theres also back pressure being created due to the restriction of the exhaust piping. With this restriction the exhaust wheel has to fight against the pressure built in the system. Sooo bigger exhaust the better.

And the lean spool maps Im guessing are just that. It leans out the AFRs to create HEAT. More heat, quicker spool. Kind of why a log mani will spool a turbo quicker than a tube mani. Less distance for the driving air to cool down. Thermal efficiency.

Volumes of tube manis dont mean jack until you have heat built up. Usually in the higher revs and after load has been established for a period of time. After this point then higher flow design of the manifold becomes apparent.


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## magner (Jul 26, 2009)

do turbos spool quicker on twin scroll tubular manifolds compared to the log type


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## leebro61 (Nov 7, 2001)

Everyone saying that turbochargers run off of "heat" recognize that these are primarily low reaction, impulse turbines, right?


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## Raddoboy (Sep 18, 2002)

magner said:


> do turbos spool quicker on twin scroll tubular manifolds compared to the log type



Well if a twin scroll setup is done right ie on a 4 cyl 2 cylinders are feeding each section of the housing, the pulses into the turbo are smooth and even. Then maybe lol. Turbo wont have "idle" time in between uneven pulses where the wheel can slow. Also depends of turbo size, runner length and dia, etc.



leebro61 said:


> Everyone saying that turbochargers run off of "heat" recognize that these are primarily low reaction, impulse turbines, right?


Nope. Just regular old turbines to me that are driven by heat expansion lol. And shop air for fun sometimes.....


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## leebro61 (Nov 7, 2001)

If these turbines are driven by "heat" then how does a smaller exhaust housing, which does not change the "heat" entering the turbine cause the turbocharger to spool faster? I keep putting heat in parentheses since I'm assuming most people equate heat and temperature, and this isn't the whole story.


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## Raddoboy (Sep 18, 2002)

leebro61 said:


> If these turbines are driven by "heat" then how does a smaller exhaust housing, which does not change the "heat" entering the turbine cause the turbocharger to spool faster? I keep putting heat in parentheses since I'm assuming most people equate heat and temperature, and this isn't the whole story.



What heats up faster? Your bathroom our your entire house?


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## leebro61 (Nov 7, 2001)

That might be the worst analogy of all time :laugh:

The temperature entering the housing is ~set by what happens in the cylinder, the smaller housing only acts to accelerate the gas that is directed onto the turbine wheel. I doubt you will, but for somebody else that reads this and is curious, you could look up Euler's turbomachinery equation. It relates shaft torque to the fluid tangential velocities at rotor inlet and outlet.


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## Raddoboy (Sep 18, 2002)

leebro61 said:


> That might be the worst analogy of all time :laugh:
> 
> The temperature entering the housing is ~set by what happens in the cylinder, the smaller housing only acts to accelerate the gas that is directed onto the turbine wheel. I doubt you will, but for somebody else that reads this and is curious, you could look up Euler's turbomachinery equation. It relates shaft torque to the fluid tangential velocities at rotor inlet and outlet.


Worst analogy? And your rant helps explain things? Why wouldnt I look that up? Am I stupid? Even though Eulers equation is horribly theoretical, its true. BUT little variables like no sources of irreversibilities(compressor surge and choke effect of exhaust) and the fact that heat transfer properties arent even part of the equation, dont make it even relative to turbocharger systems. Say what you think, I see the results everyday at work.


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## leebro61 (Nov 7, 2001)

Yes, it was a terrible analogy. An insulated, small room heats up faster than an insulated large room because it has less mass, so for a given amount of heat input it will require less time to reach a specific temperature increase. That's a closed system where the static fluid is heated by a source. Please help me understand how that applies to nozzle flow where for a first order approximation, the mass flowing through system is the ~same for different nozzle sizes and there is no heat addition.

About Euler's equation being theoretical, it's just a momentum equation... just like F=ma, it's application isn't limited by it's derivation... and it's applicable to ~anything that rotates. You see this everyday at work? Do you mind if I ask what you do?


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## Raddoboy (Sep 18, 2002)

Thats exactly what I said. :screwy: Most of the points I was making before you piped up was about manifold design, then you go off about crap thats not really relivent to turbo systems in general. Were not talking windmills here. When thermal properties arent part of the equation it makes it null in this case. HEAT EXPANSION is the driving force of the wheel. Not airflow. How many times does this have to be pounded into peoples heads? 

As for the "therotical" comment I made, its just that. Numbers on a piece of paper and not real world. When true day to day conditions arent equated then it makes the outcome untrue. Oh and for what I do for a living? We build turbo systems.


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## leebro61 (Nov 7, 2001)

Great, so you build turbo systems (who doesn't build turbo systems these days?). This doesn't imply that you understand the physics of how they work. On the other hand, some of us are actually gas turbine engineers who build turbo systems in their spare time...

edit - I apologize to the OP, this is going off course and I'll leave it alone. :sly:


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## Raddoboy (Sep 18, 2002)

That explains alot. Are you really comparing a gas turbine to a turbocharger? Thats like comparing a diesel to gas engine because they both use pistons. I stand my ground because we design, test and build our products to function. When you have as many hours as we do in turbocharging R&D, we'll be on the same page. The cars we've built speak for themselves. Not trying to be a dick, am just over misinformation. To the OP as well, sorry your thread has turned into a **** show.


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