Definition of "lag" and "spool up"

[S2central.net]

In my job, terminology is important... I think it is in yours too Vasilis... But I agree we dont need hundreds of words to describe things like this.

[jogi730]

This topic is actually of great interest to me. As some of you know, I am having some real issues trying to resolve matters with my last tuner. I told him that I was not happy with my T61 which spooled at 3500 and was really on the case at 4000. He told me a special hybrid GT35R would spool at 2500 and be away like a train by 2800.
Now he has changed his statement to positive boost occuring at 2500 which is a very different scenario.
My first experience of 'lag' was when I had the T61 fitted.
I would personally say it is the time that you put your foot down to acceleration of any real note kicking in. Please keep definitions coming.
Cheers
CHris

[Puglife]

Both are based around time, and both have essentially the same goal.
The differences are negligible.

Lag is under sudden acceleration or full throttle and dependant on gearing.
Spool can be dependant on a variable throttle position and gearing.

[newsh]

Lag is usually a negative term, its the time you have to wait between flooring it and getting the power, a standard S2 has very little lag because the small turbo can spin (or spool) up very quickly. However, if you floor it at 1000 RPM there will still be a lag before the power comes in. So the lag is the delay time between action and reaction.
To spool in my view means to spin so you can say "start to spool" for "starting to spin" ie the turbine is rotating and starting to compress the charge, and you can say "fully spooled" or "spooled up" meaning the turbo is spinning at optimum speed to give good power.

I'm not sure how we ended up with the term "spool" see below.

spool
noun [C]
a tube-shaped object with top and bottom edges that stick out and around which a length of thread, wire, film, etc. is wrapped in order to store it:
a spool of cotton/film

(from Cambridge Advanced Learner's Dictionary)

[A80Avant]

Paul, as you say, it may be important to YOU or REPO, but not to me.In my job terminology of medicine is indeed important, but not to you most of the times if you are the patient. See my point?

so for an expert of their field i agree, it is important to be precise.It is not important in full terms for me to know, otherwise i wouldnt need the expert then,would i?

[jogi730]

I coompletely disagree!
THere is nothing that irritates me more than a doctor pussying about and not telling me exactly what is wrong with me.
Likewise with a car, especially in my situation, I want to know why when I put my foot down nothing happens. Without forums and discussions like this, SOME so called experts can offer you total buls**t and charge you a lot of money.
And yes, this is exactly what happened to me.
Chris

[Acidburn]

So the lag is the delay time between action and reaction.

love this quote

[AUDIS2avant]

I usually think that lag is how many rpm the turbo needs to get ON boost(how slow it is) and spool up is how quick it retrives boost after gearchange etc

[Zoig]

Jamo, I agree with you on this one

[A80Avant]

jogi, first of all you misunderstood what i wrote.

I have no problem and doctors should explain to patients what the problem is, but believe me if i go into terminology,you will end up asking me: So am i going to be ok or what?

what that in mind i can still explain to you in a more simple language what is what, and so give you the info you need.

Likewise, what is the point if i know or not what lag or spool excactly is? All i need to know is when the turbo will give me full boost.The rest are for the expert to sort out. Now depending on how the expert deals with the whole thing, will make me choose him or disregard him. Simple.

By the way, there is no such thing as a doctor pussying you around. If there is you should sue him. Bottom line you will have to know what is wrong with you.(offtopic but for the sake of comparison)

This thread would have been much simpler if repo had simply written down his expert opinion rather than asking to see what people know. What is the point in doing that?

[jogi730]

My point was that if someone could explain it, it would be easier for everyone. However, this is where the problem lies as there seems to be no outright definition so everyone has their own take on things. Now with that in mind, much can be distorted. And this is what I am trying to prove. It sounds like it is easier to sue a doctor that a mechanic
Chris

[A80Avant]

much easier!!
least that can happen from a mechanic's mistake is a blown engine... and look what has happened to quatronics so far... excactly! nothing!

[repo]

I am not sure if I am in position to make ultimate definitions to terms.

Vas' comment reflects the problem. "Who cares, as long as I am right".

What I wanted to show to people with this thread is, the lack of uniformity here causes a lot of misunderstandings.

Clarkson Evo video is perfect example. That is no lag, but boost treshold or operating range. Even there is something to clarify. Boost treshold in any case is not the same as operating range.

Usually turbo engines meet positive intake pressure on practically any revs. Still, engines have proper range, of which within You need to stay during sporty driving.

Makes also pretty clear to everyone, boost treshold is not same as spool up. No one would say a 500hp I5 is spooled up on 2000rpm, even though there usually is like 0,05-0,2bar boost, as the engine kicks in at 3500-4500, depending on setup.

Lag is the delay from vacuum to full boost while ON OPERATING REV RANGE. Lag takes place in three typical situations:

1: flooring the pedal on high revs, but from mild load, i.e. mild vacuum
2: changing the gear on high load
3: releasing and depressing the throttle while on high revs

Spool up in the other hand is subjective, and even for me, after decade of daily experience with this stuff, hard to decribe. Basically I would like to say spoolup is rev point where torque curve climbs up in slope of more than 1 to 1.

This treshold is easy to notice inside the car. AnLe said million yers ago: spool up takes place when acceleration starts to accelerate.

This is where it gets tricky (again). The point a turbo gets full boost is not spool up, if You look at the whole setup. Surprizingly often the engine does not start to push properly, even despotes of the full boost, until You hit the operating range of the engine itself.

So if we talk about spool up as only it turbo point of view, yes, turbo is spooled up, when max boost is achieved, but when the whole setup is spooled up, is different story.

Personally I do not feel the term spool up to concern turbo only, but the whole setup.

As a matter of fact I find it funny, people think like Clarkson. Imagine 5th gear making the same test against ANY 300hp naturally aspirated 2l motor. Rental Fiat would brutalize the competition even better, as the high tuned motor did not reach it's operating range. Still here we are, talking about the lag the mitsu has.

And Vasilis may make fun of me and the thread, but pls keep in mind, english is not my first, not even my second language, so this is quite hard for me.

[repo]

But I agree we dont need hundreds of words to describe things like this.

That is why we have these terms. Still, inventor of the terms forgot to use those hundreds of words to decribe ehat (s)he ment.

[A80Avant]

Im not making fun of anyone,or any thread. Pity you look at it this way,but that is something that has to do with you,not me.
Also can you please tell me where in my previous comments you are basing this at :Vas' comment reflects the problem. "Who cares, as long as I am right". ???

What i said is that whoever cares about spool and lag(and those usually are people who want to have a strong daily driver,not a drag racer), really wants to know at what rpm full boost is achieved on each gear.Most imporant information though really is 3d gear,bacause if you tell me that the X turbo will do that on 4d gear on 4000rpm, then it tells me that on the higher gears it will be better,and that will give me an idea etc etc...

What suprises though is that if you as an expert are having trouble giving those definitions, then how are you in a good position to guide someone properly in getting the turbo that will actually suit their purposes?

Good descriptions by the way,i do admit