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Why having boost early is important ?
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2jzmkiv



Joined: 22 May 2015
Posts: 82

PostPosted: Thu Dec 31, 2015 4:56 pm    Post subject: Why having boost early is important ? Reply with quote

Why do people care about turbochargers making boost early as possible say you have X turbocharger and Y turbocharger both have same turbine/compressor size but the difference is X has undivided turbine housing cast compressor wheel and journal bearings Y has divided turbine housing billet compressor wheel and ball bearings both are used on the same engine at same pressure 14 psi. Imagine X hits full boost at 4000 rpm Y hits at 2000 rpm would you still not make the same amount of horsepower at for example 5500 rpm ? only advantage being Y will be more responsive and it wont have lag as much as X has between gear changes also i am guessing Y would have more torque down low and that would improve street drive ability but i feel like there is something I am still missing
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riceracing



Joined: 27 Apr 2013
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PostPosted: Thu Dec 31, 2015 5:34 pm    Post subject: Reply with quote

This is just my experience:

It makes no difference at all, and in circuit type work actually having a turbo that spools too early is very bad as it comes on at apex or soon after and lights up the tires so you are always on the traction control or in a POS ECU you are using boost by gear limits etc etc.

So picking the right turbo is key (or turbine housing).

The whole 'boost early' crap is mostly by forum dwellers or people who post up turbo compressor maps all the time ' sprouting theory ' all while not understanding basic maths let alone applications I find. The other camp is people with nothing cars who want 'full boost' right after the starter motor disengages so they can compare c o c k length to their mates about how early their turbo spools LOL.

You are right its a gayer than aids internet phenomenon in most cases.
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baldur



Joined: 12 Oct 2007
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PostPosted: Thu Dec 31, 2015 5:51 pm    Post subject: Reply with quote

It's a compromise and you have to consider the application when making the compromise. Quick response makes the car easier to drive as you don't need to apply throttle in advance before power is wanted.
A wide power band allows more compromises in gear ratios, you can get away with a lower number of speeds in the gearbox and shift times don't punish you as badly in the tight corners as you don't need to shift gears as often.
Even in drag racing, a quick responding setup can be an advantage at higher power levels, if you've got good throttle response you can pedal the car if it gets out of shape and not have to abort the run.
But generally, more is not always better. You need a balanced setup to get a well performing car.
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2jzmkiv



Joined: 22 May 2015
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PostPosted: Fri Jan 01, 2016 2:16 am    Post subject: Reply with quote

well in case of drag racing i have aem infinity 8 and like aem there are many other ecu's out there that provides flat foot shifting which I am pretty sure many of you here know what that does since you do not pull your foot off the gas pedal i believe it does not matter if its a 60mm or 82mm you are on throttle you are on boost that is it am i wrong ?
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baldur



Joined: 12 Oct 2007
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Location: Reykjavik, Iceland

PostPosted: Fri Jan 01, 2016 3:16 am    Post subject: Reply with quote

2jzmkiv wrote:
well in case of drag racing i have aem infinity 8 and like aem there are many other ecu's out there that provides flat foot shifting which I am pretty sure many of you here know what that does since you do not pull your foot off the gas pedal i believe it does not matter if its a 60mm or 82mm you are on throttle you are on boost that is it am i wrong ?


Engine speed also needs to stay inside the power band. A mistake rookie drag racers often make with a manual transmission on small tyre cars (street cars) is shifting out of first or second gear while the wheels are spinning. Doing this will most often drop the engine speed out of the power band and boost pressure is lost. It takes some training to learn to detect when the car is ready to shift, relying on the rev counter or shift light is not enough.
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keithmac



Joined: 14 Nov 2010
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PostPosted: Fri Jan 01, 2016 4:43 am    Post subject: Reply with quote

For street use I actually preferred my car with smaller turbos and earlier spool up BUT, for 1/4 mile running as long as the turbos are fully spun up by 4000rpm the car is significantly quicker on larger "laggy" turbos.

I run a home made flat shift system and it knocked at least 1/2 a second off my 1/4 mile times and made runs more consistent.

Same with launch control.

Even in an AWD car I still span the tyres in 1st off a launch, as has been said you have to get a feel for when the car is ready to shift not just because the shift light is blinking at you Wink.
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E30IS



Joined: 26 Jun 2008
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PostPosted: Fri Jan 01, 2016 5:08 am    Post subject: Reply with quote

pretty simple really, it depends on the application. some people want lots of torque at low rpm, for example OEMS are all doing this so the torque is linear-ish and relavely predictable. Where as at drags all that matters is the average power in the rpm band actually used during the run which can be pretty narrow.

its worth remember that not all people do the same kind of racing or even race at all so prioritys differ
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rvengineering



Joined: 28 Feb 2010
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PostPosted: Fri Jan 01, 2016 6:26 am    Post subject: Reply with quote

Well yes it?s always a compromise on turbo size but if I could have it all with great low en power and able to carry max power to the redline managing that power is more like a luxury problem with the correct ECU and other hardware to get things under control.

Today the main goal with the last generation GTX ? GTW or EFR - SX-E is to get more on everything like operating range and efficiency so the only thing left is to find the turbo you need for the thing you want to do with it.
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stevieturbo



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PostPosted: Fri Jan 01, 2016 11:39 am    Post subject: Re: Why having boost early is important ? Reply with quote

2jzmkiv wrote:
Why do people care about turbochargers making boost early as possible say you have X turbocharger and Y turbocharger both have same turbine/compressor size but the difference is X has undivided turbine housing cast compressor wheel and journal bearings Y has divided turbine housing billet compressor wheel and ball bearings both are used on the same engine at same pressure 14 psi. Imagine X hits full boost at 4000 rpm Y hits at 2000 rpm would you still not make the same amount of horsepower at for example 5500 rpm ? only advantage being Y will be more responsive and it wont have lag as much as X has between gear changes also i am guessing Y would have more torque down low and that would improve street drive ability but i feel like there is something I am still missing


That has to be the most random question ever.

Go drive some turbo cars, and then all answers will be blatantly obvious.

If the answers arent obvious, take up a different interest, like tree hugging or something.
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riceracing



Joined: 27 Apr 2013
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PostPosted: Fri Jan 01, 2016 1:12 pm    Post subject: Re: Why having boost early is important ? Reply with quote

stevieturbo wrote:
2jzmkiv wrote:
Why do people care about turbochargers making boost early as possible say you have X turbocharger and Y turbocharger both have same turbine/compressor size but the difference is X has undivided turbine housing cast compressor wheel and journal bearings Y has divided turbine housing billet compressor wheel and ball bearings both are used on the same engine at same pressure 14 psi. Imagine X hits full boost at 4000 rpm Y hits at 2000 rpm would you still not make the same amount of horsepower at for example 5500 rpm ? only advantage being Y will be more responsive and it wont have lag as much as X has between gear changes also i am guessing Y would have more torque down low and that would improve street drive ability but i feel like there is something I am still missing


That has to be the most random question ever.

Go drive some turbo cars, and then all answers will be blatantly obvious.

If the answers arent obvious, take up a different interest, like tree hugging or something.


Laughing You will see he has lots of 'random' questions, its pretty obvious he is just starting out with this Laughing thus my replies to him, though I am trying to be 'nice'.......... everyone has to start somewhere.

I agree with stevie Wink I think people here are not used too or cant pick up on this as most would not be typing detailed replies to him. I gave up after the 'fuel cooling on over run' thread personally.
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2jzmkiv



Joined: 22 May 2015
Posts: 82

PostPosted: Fri Jan 01, 2016 2:10 pm    Post subject: Reply with quote

I think it is important to state that I am only 20 years old and yes i do drive a stock supra which I am collecting parts now for it and looking forward to build it also I think I am doing good because most people my age are pulling handbrakes in fwd cars, drunk driving, ricing out their cars etc.. and I am only trying to improve my knowledge on cars so please go easy on me everyone I am probably the youngest person on this forum Smile
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2jzmkiv



Joined: 22 May 2015
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PostPosted: Fri Jan 01, 2016 2:34 pm    Post subject: Re: Why having boost early is important ? Reply with quote

stevieturbo wrote:

Go drive some turbo cars, and then all answers will be blatantly obvious.


Well if I could I would not be here asking these questions would I Very Happy ? I have only driven a stock jdm toyota supra jdm evo 7 jdm evo 8 and jdm subaru impreza wrx sti type ra-r out of all the subaru type ra-r sti felt really different
in terms of boost and response rest including my supra was quite like each other so I cannot say I have driven enough turbocharged cars so that answers would be blatantly obvious to me.
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rvengineering



Joined: 28 Feb 2010
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Location: Holland

PostPosted: Sat Jan 02, 2016 3:44 am    Post subject: Reply with quote

In general there are no stupid questions, some know more than others and if you want to know more just ask and hope you get what you where looking for to find. I have been training a load of people and in some cases open questions gave way to very good conversation where @ some point you have to start thinking about things that all looks to obvious to most of us but are they? In the world of making progress you have to keep an open mind and be willing to ask and debate hoping not to get a stupid answer.
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stevieturbo



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PostPosted: Sat Jan 02, 2016 5:30 am    Post subject: Re: Why having boost early is important ? Reply with quote

2jzmkiv wrote:
stevieturbo wrote:

Go drive some turbo cars, and then all answers will be blatantly obvious.


Well if I could I would not be here asking these questions would I Very Happy ? I have only driven a stock jdm toyota supra jdm evo 7 jdm evo 8 and jdm subaru impreza wrx sti type ra-r out of all the subaru type ra-r sti felt really different
in terms of boost and response rest including my supra was quite like each other so I cannot say I have driven enough turbocharged cars so that answers would be blatantly obvious to me.


it's quite simple and it will apply to almost any turbo car you've driven at some point.

If you've put your foot down and power/torque has been lacking, then that is the very reason you'd want faster spool. Typically this will be at lower rpm's and the main reason the Supra had a sequential turbo setup with one small and one bigger turbo to try and give a wider range.

Of course that then needs balanced by what is achievable at the other extreme of the engines operating range in terms of power potential.

And no, all of the cars you describe would not have had the same characteristics because they are so vastly different.
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2jzmkiv



Joined: 22 May 2015
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PostPosted: Sat Jan 02, 2016 9:03 am    Post subject: Re: Why having boost early is important ? Reply with quote

stevieturbo wrote:


it's quite simple and it will apply to almost any turbo car you've driven at some point.

If you've put your foot down and power/torque has been lacking, then that is the very reason you'd want faster spool. Typically this will be at lower rpm's and the main reason the Supra had a sequential turbo setup with one small and one bigger turbo to try and give a wider range.

Of course that then needs balanced by what is achievable at the other extreme of the engines operating range in terms of power potential.

And no, all of the cars you describe would not have had the same characteristics because they are so vastly different.


Few more questions if you do not mind

''If you've put your foot down and power/torque has been lacking, then that is the very reason you'd want faster spool'' does that not depend WHEN you put your foot down ? i remember jeremy clarkson on top gear raced with a rental car in the lancer evolution and rental car won because they both raced in their final gears lancer could not reach its power band but his point was ridiculous because cars have gears and we are allowed to shift up and down so if i put my foot down and power and torque is lacking i do not think that i got the wrong turbocharger and spend another $$$$ i simply downshift.

The most noticeable difference was after i converted sequential system to true twin this is done by deleting the exhaust gas circulation valve then i would put my foot down and the boost gauge would not move above 0 until 3500 rpm from sequential to true twin conversion yes there was a huge difference but ttc supra compared with the stock lancer evolution there is not much of a difference this is because supra did not have one small and one bigger turbo in its sequential setup i do know most common sequential setups did have one larger one smaller turbochargers but jdm supras have twin ct20a turbochargers which are exactly the same the difference is turbo no:1 has wastegate turbo no:2 is Free floating turbo no:2 is only capable of flowing 0.5 bar boost pressure so when converted to ttc spool difference between a stock lancer evo and the supra is around 500rpms my point is it is not enough to completely grasp the idea hence i felt the need to start this thread.
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stevieturbo



Joined: 29 Aug 2006
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PostPosted: Sat Jan 02, 2016 9:10 am    Post subject: Re: Why having boost early is important ? Reply with quote

2jzmkiv wrote:


''If you've put your foot down and power/torque has been lacking, then that is the very reason you'd want faster spool'' does that not depend WHEN you put your foot down ?


Not even sure that's a serious question ?

Seriously, think about that even for a millisecond.


Rolling Eyes Rolling Eyes Rolling Eyes Rolling Eyes :roll:

Well if you're happy to change gear to negate any effects of lack of power in certain areas, then you're original question is null and void.

Some people want a wider power band though without the never ending need to change gear to make progress.
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2jzmkiv



Joined: 22 May 2015
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PostPosted: Sat Jan 02, 2016 9:41 am    Post subject: Re: Why having boost early is important ? Reply with quote

stevieturbo wrote:
2jzmkiv wrote:


''If you've put your foot down and power/torque has been lacking, then that is the very reason you'd want faster spool'' does that not depend WHEN you put your foot down ?


Not even sure that's a serious question ?

Seriously, think about that even for a millisecond.


Rolling Eyes Rolling Eyes Rolling Eyes Rolling Eyes :roll:

Well if you're happy to change gear to negate any effects of lack of power in certain areas, then you're original question is null and void.

Some people want a wider power band though without the never ending need to change gear to make progress.


I thought about it for 600000 milliseconds but i still do not get it if your target is peak hp then you cannot put your foot down at 2000rpm and say ''oh i am not making 1000hp at 2000rpms maybe i need a different turbocharger'' you simply downshift into your powerband where you achieve that power or maybe the whole reason behind people wanting earlier spool is so that they can push more boost at the same rpm if your engine redlines at 8500rpm and you are making 900 hp at 5500 rpm with 2 bar boost pressure if your turbo spools earlier maybe you can reach 2.5 bar at the same rpm and make 970hp
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stevieturbo



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PostPosted: Sat Jan 02, 2016 9:54 am    Post subject: Reply with quote

Who said their target was only peak HP ? or anything to do with peak hp

You asked why people care about making boost earlier.

The answer is obvious, the question and answer have nothing whatsoever to do with peak hp.

You're either mixing things up or asking and trying to answer very different questions.
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Pantera EFI



Joined: 12 Feb 2005
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PostPosted: Sat Jan 02, 2016 10:40 am    Post subject: Turbo Match using Deltp-P IMAP/EMAP Reply with quote

FIRST, ALL questions are stupid for the one asking, WE are NOT Dumb here as that definition determines the ABILITY to even ask a question.

A better definition about "spool" speed would be "How fast can my engine reach FULL SONG ?".
This is determined by Turbo Match (sure), Valve Timing, many other engine specifications such as port diameter and length.
The Drake Turbo Offy was created to run 120" of boost AND was fitted with equal intake/exhaust valve size, even the intake ports were close to the exhaust ports in diameter.

My method is to record Delta-P range (IMAP/EMAP) for use as a spool speed measurement tool.
I have had turbos "spool" so fast that it could even "back off" the compressor retaining nut.
I would like to see your reports on IMAP/EMAP ?

My method to get the best turbo match is to first "model" the engine in EAP-PRO (Performance Trends).
I would be happy to do this for your needs, for free.

Lance
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2jzmkiv



Joined: 22 May 2015
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PostPosted: Sat Jan 02, 2016 11:33 am    Post subject: Reply with quote

stevieturbo wrote:
Who said their target was only peak HP ? or anything to do with peak hp

You asked why people care about making boost earlier.

The answer is obvious, the question and answer have nothing whatsoever to do with peak hp.

You're either mixing things up or asking and trying to answer very different questions.


Ok that makes sense now it appears i was really mixing things up because i was thinking as if their target is ONLY peak hp never thought other way around to be honest i have to thank each and everyone of you for being patient and answering all my questions really appreciate it you have my thanks !
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