How to throttle?
Thread Starter
Registered User
Joined: Feb 2003
Posts: 30
From: Buffalo NY :(
Car Info: 2003 Subaru Impreza WRX
How to throttle?
Ill start by saying that Im sorry if the answer to my question is posted all over these forums... I just could not find it with the searches I did.
My question is, what percentage of wide open throttle will generate the most acceleration? I notice that when Im just casually driving, Ill often take off hard and then lose power as soon as boost starts to spool up (around 2500 rpms). In an opposit scenario, when Im trying to get the maximum acceleration possible, I tend to pretty much depress the throttle close to 100%, which does NOT seem to produce the optimum results. I usually find that somewhere between 50-75% wot is best for acceleration, depending on the rpms.
I know this question is vague, but what Im really looking to find out is if there are any better ways to throttle without just jamming the long skinny peddle to the carpet
Thanks!
My question is, what percentage of wide open throttle will generate the most acceleration? I notice that when Im just casually driving, Ill often take off hard and then lose power as soon as boost starts to spool up (around 2500 rpms). In an opposit scenario, when Im trying to get the maximum acceleration possible, I tend to pretty much depress the throttle close to 100%, which does NOT seem to produce the optimum results. I usually find that somewhere between 50-75% wot is best for acceleration, depending on the rpms.
I know this question is vague, but what Im really looking to find out is if there are any better ways to throttle without just jamming the long skinny peddle to the carpet
Thanks!
Thread Starter
Registered User
Joined: Feb 2003
Posts: 30
From: Buffalo NY :(
Car Info: 2003 Subaru Impreza WRX
How can I lose power when boost hits? I have no idea, but if I keep the throttle depressed at the same level, the acceleration does not increase (volicity keeps increasing, hence acceleration is remaining the same).
As for WOT, I was under the assumption that the computer runs a preprogrammed open loop for WOT, which might mean that you do not get the optimum acceleration.
This is part of the reason that people who use an air/fuel controler such as the Apexi S-AFC set their low throttle setting to like 25% and their high setting no higher than 80%. Above that and it makes no difference. The ECU takes over and no longer makes adjustments based on MAP or MAF sensor readings.
As for WOT, I was under the assumption that the computer runs a preprogrammed open loop for WOT, which might mean that you do not get the optimum acceleration.
This is part of the reason that people who use an air/fuel controler such as the Apexi S-AFC set their low throttle setting to like 25% and their high setting no higher than 80%. Above that and it makes no difference. The ECU takes over and no longer makes adjustments based on MAP or MAF sensor readings.
Registered User
Joined: Nov 2002
Posts: 181
From: OC, CA
Car Info: 02 WRX
phucvtec,
I've seen similar situation in my 02 WRX. My short answer is keep the rpm above 3k for best acceleration, and dont bother trying to find the ideal throttle position at differnt rpm I tend to shift at between 3.5-4k normally. (it's a tiny 2.0L motor after all)
FWIW... when you WOT at lower rpm especially in lower gear (1st or 2nd) I think the turbo is having a hard time trying to build the boost while the engine rpm is building up. i.e. it's not spooling fast enough to keep up with increasing rpm. you'll definitely have better response if you're already cruising at above 3000rpm, then WOT since the turbo is sufficiently spinning at higher rpm. Even then, I prefer 'squeezing' the throttle than stomping.
Also, there's some truth in "partial throttle is better than WOT at lower rpm". I remember reading about how throttle-by-wire effectively pulls back to adjust when you WOT at lower rpm.
btw, have you done the grounding mod? I highly recommend it for better throttle response! and it's cheap to do!
I've seen similar situation in my 02 WRX. My short answer is keep the rpm above 3k for best acceleration, and dont bother trying to find the ideal throttle position at differnt rpm
I tend to shift at between 3.5-4k normally. (it's a tiny 2.0L motor after all)FWIW... when you WOT at lower rpm especially in lower gear (1st or 2nd) I think the turbo is having a hard time trying to build the boost while the engine rpm is building up. i.e. it's not spooling fast enough to keep up with increasing rpm. you'll definitely have better response if you're already cruising at above 3000rpm, then WOT since the turbo is sufficiently spinning at higher rpm. Even then, I prefer 'squeezing' the throttle than stomping.
Also, there's some truth in "partial throttle is better than WOT at lower rpm". I remember reading about how throttle-by-wire effectively pulls back to adjust when you WOT at lower rpm.
btw, have you done the grounding mod? I highly recommend it for better throttle response! and it's cheap to do!
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in theory on an n/a engine, this could be true. cause in a n/a engine, flow and momentum of the air are the most important. at certain rpm's the flow would be better w/ a lighter throttle position. This only works in cars w/ no intake manifold butterfly's that open at WOT.
In a turbo car, it's just the opposite. The object is to ram as much air as possible into the combustion chamber as possible. therefore WOT on your car is best.
In a turbo car, it's just the opposite. The object is to ram as much air as possible into the combustion chamber as possible. therefore WOT on your car is best.
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Originally posted by MOG_22
WOT 100% is always best for accleration
WOT 100% is always best for accleration
phucvtec, if your car is stock I would do a tune-up. If not then tuning may be in order.
Registered User
Joined: Nov 2002
Posts: 181
From: OC, CA
Car Info: 02 WRX
Originally posted by HTM WRX
in theory on an n/a engine, this could be true. cause in a n/a engine, flow and momentum of the air are the most important. at certain rpm's the flow would be better w/ a lighter throttle position. This only works in cars w/ no intake manifold butterfly's that open at WOT.
in theory on an n/a engine, this could be true. cause in a n/a engine, flow and momentum of the air are the most important. at certain rpm's the flow would be better w/ a lighter throttle position. This only works in cars w/ no intake manifold butterfly's that open at WOT.
you actually sound like you have some experience, unlike me... i just read about it
I actually read about the throttle-by-wire in an article about Audi S4 and RS4 which are both turbo charged. Would you say that what you mentioned could be applied to turbo cars as well?
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WOT is not the best solution for fast acceleration on either N/A or turbo cars. Reason being, before boost WRX is essentially a N/A car. During low RPM, the engin cannot draw the air fast enough to match the amount of fuel coming in, resulting in a rich burn. Therefore the engine has less power, thats why the slower acceleration. Now drag car normally use different type of fuel or with addition of NOS. They can pedel to the metal because their fuel or additon of NOS already have O2 in it as part of its chemical makeup. Thats why it burn hotter and faster. We don't have this or want this, since it can destroy our car. ECU was mentioned, however its unlikly for it to cause your problem. Technically speaking ECU to MAP/TP/etc sensors is a CLOSE-LOOP circuit, by defintion. It knows the amount of air via the TP sensor and amount of fuel into the engine via the O2 sensor. Unless your O2 senors are bad (which is unlike) ECU will not cut air/fuel. It only limits top speed and not how fast the car can accerate, after all its the selling point of WRX. Another sinerio is that at WOT, you might because outside of the fuel map, meaning there is no definition for the amount of fuel needed at WOT and current speed, you might want to consider this possiblity, if you have a OBD-II reader you should be able verifiy this.
Now my question to you, do you know when the turbo is acutally boosting? Because it is possible that you are expecting an accerlation gain at certain RPM (ie 3000+, because everyone said so) while it is realy boosting at some other value. My advise is WOT is not the way to go, find where your operate the best and set that to be your norm. Don't over think the problem, because your fine, just enjoy your car.
Haven77
Now my question to you, do you know when the turbo is acutally boosting? Because it is possible that you are expecting an accerlation gain at certain RPM (ie 3000+, because everyone said so) while it is realy boosting at some other value. My advise is WOT is not the way to go, find where your operate the best and set that to be your norm. Don't over think the problem, because your fine, just enjoy your car
. Haven77
Last edited by haven77; Oct 29, 2003 at 02:48 AM.
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What mods do you have? If you're running an MBC its quite dangerouse to push the car at heavy part throttle as the ECU doesn't always switch to open loop causing a lean condition which is very dangerous.
That said, I have also fealt what you're talking about. Its mostly if you go WOT at lower RPMs and very suddenly. When you do this, you feel pretty much the most lag the car can ever have as the engine is barely in spool-up range and the turbo is close to stopped. This also puts a lot of load on the engine and causes the ECU to run rich open loop fueling even while the engine isn't under boost. This deffinately makes it feel sluggish. When you roll into the throttle, you're staying in closed loop (more effecient) longer and giving the engine and turbo a bit more time to spin up before you request full power. That generally makes for a smoother, stronger feeling transition.
Just be careful if you have an MBC!
-- Ed
That said, I have also fealt what you're talking about. Its mostly if you go WOT at lower RPMs and very suddenly. When you do this, you feel pretty much the most lag the car can ever have as the engine is barely in spool-up range and the turbo is close to stopped. This also puts a lot of load on the engine and causes the ECU to run rich open loop fueling even while the engine isn't under boost. This deffinately makes it feel sluggish. When you roll into the throttle, you're staying in closed loop (more effecient) longer and giving the engine and turbo a bit more time to spin up before you request full power. That generally makes for a smoother, stronger feeling transition.
Just be careful if you have an MBC!
-- Ed
Last edited by MethodBuilt; Oct 29, 2003 at 03:13 AM.
Thread Starter
Registered User
Joined: Feb 2003
Posts: 30
From: Buffalo NY :(
Car Info: 2003 Subaru Impreza WRX
Ladies and gentlemen, thank you very much for all of your suggestions!
To answer a few questions: I have a manual transmission. My vehicle is a 2003 w/ about 15K miles. A recently installed boost gauge suggests that boost climps and peaks at about 3200 rmps at ~15psi. My only mods are a Vishnu single dump turbo back, and a GFB BOV (for vanity). I am NOT running a MBC or EBC. I am scared "blank"less of altering my boost for fear of damaging the engine (and making monthly payments on a car I do not drive). Im currently waiting for my ECU to return from Cobb w/ a stage 2 reflash.
This all said, I think that all of your explanations are excellent. The one that probably most applies to my situation is the one where I attempt to accelerate in a certain gear (say 3rd) from a engine speed that is NOT generating peak boost yet, like 2500 rmps. I know the right thing to do is to simply down shift, but I just thought it strange that whenever I hammer the throttle, the car seems to simply bog down and do nothing for about 1-2 seconds. Now, the rich run situation best explains this problem IMO. Makes perfect sence. Im sure this is a situation where slowly depressing the throttle makes most sence.
Anyway, my problem is not a problem, rather a curiosity. I try to learn the most about the vehicle that I drive, not just because of my curiosity, but because I think its my responsiblilty My vehicle runs fine. I have absolutely no problem eating randon civics that tool around my neigherbood. AWD is simply unbeatable
Thanks people
To answer a few questions: I have a manual transmission. My vehicle is a 2003 w/ about 15K miles. A recently installed boost gauge suggests that boost climps and peaks at about 3200 rmps at ~15psi. My only mods are a Vishnu single dump turbo back, and a GFB BOV (for vanity). I am NOT running a MBC or EBC. I am scared "blank"less of altering my boost for fear of damaging the engine (and making monthly payments on a car I do not drive). Im currently waiting for my ECU to return from Cobb w/ a stage 2 reflash.
This all said, I think that all of your explanations are excellent. The one that probably most applies to my situation is the one where I attempt to accelerate in a certain gear (say 3rd) from a engine speed that is NOT generating peak boost yet, like 2500 rmps. I know the right thing to do is to simply down shift, but I just thought it strange that whenever I hammer the throttle, the car seems to simply bog down and do nothing for about 1-2 seconds. Now, the rich run situation best explains this problem IMO. Makes perfect sence. Im sure this is a situation where slowly depressing the throttle makes most sence.
Anyway, my problem is not a problem, rather a curiosity. I try to learn the most about the vehicle that I drive, not just because of my curiosity, but because I think its my responsiblilty
My vehicle runs fine. I have absolutely no problem eating randon civics that tool around my neigherbood. AWD is simply unbeatable Thanks people