Soulquarian

I have a ZPI Stage 1.5 that's currently downtuned. I'm at 4 PSI and making about 224whp.

For a few weeks, I've been experiencing some serious throttle response issues. Whenever I shift, there seems to be a half second delay between gas and acceleration. Makes driving VERY jerky. I had a ZPI stage 0 previously, and I didn't have this problem. I have a few theories:

1) I need colder spark plugs
2) My Greddy Emanage Ultimate and Stock ECU are not playing nice
3) I need a lighter flywheel

I really think it's something eletrical, but I'm not sure. Throttle delays in shifting happen in a variety of RPM's.

paul_dezod

Sounds tuning related. Not enough fuel during accel

SePaTc

imo its probably just the toyota built in throttle delay with the dbw system.

although, i just used some CNC air intake and throttle body cleaner this weekend, and i did notice crisper throttle response. you may have gotten some junk in your throttle body during install or w/e...

can't hurt to try it for a can for 4 bucks.... also got MAF cleaner too.

engifineer

Most of the stock "delay" is due to high rotating mass (aka heavy flywheel), which is why people who go lighter find that the delay pretty much disappears.

But, what you are talking about is something different, especially since it went from fine to terrible like that. I would say tuning as well.

Cleaning the MAF isnt a terrible thing to try either, especially since it is a cheap, quick item to do.

Mightygnu

I have to agree with Paul and the tuning issue.

It wouldn't hurt for a lighter flywheel though Marlon.

Mr_Meaty

Do you have a wideband?
Do your AFRS go full lean when you put down the pedle, and then pick back up after you start to get going?

SePaTc

Again, I'm not going to argue semantics over what percentage of responsibility the stock flywheel has in delaying throttle response, versus the drive by wire system.

all i KNOW, is that there IS a noticeable DBW delay in throttle response. I noticed it right away...as have many other people on this forum. There is a TSB for "DBW throttle delay" for Toyota Camrys. And there are many other dbw cars on the market that experience similar delays.

While using a lighter aftermarket flywheel should speed up revs, the weight of the flywheel has no detrimental affect on delaying engine response. Your talking about a 160lb/ft engine struggling to rotate a [what?] 16lb flywheel???

We're not talking about the revs rising slowly once you get throttle response. The dbw delay comes from the lack of there being a direct mechanical link between your foot and the throttle body.

in cable controlled throttles, your foot presses the pedal and the throttle opens almost at the exact same moment. In dbw, your foot presses the pedal, a sensor reads that input, and relays the signal to the ecu, which relays to the throttle body which then opens the throttle accordingly.

Your theory that a heavier flywheel causes the delay because it takes a moment for the flywheel to overcome inertia is bogus. Even at idle, the flywheel is rotating!!! its not like its having to start from a complete standstill. Its already in motion, and since u seem to know something about physics, you should know that it would take very minimal input to get the flywheel moving from 750 rpms to 1500rpms....especially for a torquey motor

the "dead spot" in the pedal (ie. you can depress the throttle quite a few mm's before getting any response) also plays a part.

i'm not denying that replacing the stock flywheel can improve throttle response, i'm just saying without a doubt, that it is not the cause. As far as I'm aware, toyota actually builds in a throttle delay into their dbw systems for emissions purposes or something like that.

Dbw delay is real. Its not just on scion tcs. if you don't know that, you are totally out of touch with the automotive world.

engifineer

wow... the weight of a flywheel has a HUGE impact on how quickly revs change. That has been common knowledge for just about everyone working on or modifying a car for as long as people have been working on and modifying cars. So nothing about what I said is bogus.

Delay is purposely introduced into DBW systems for drive ability mainly. A potentiometer based throttle system (or any control input for that matter) can be very hard to modulate smoothly. This is true from industrial control systems to what we are talking about here. You introduce a buffering of the signal so a human being has a better time of controlling it smoothly. This, however, does not have to be over done to the point that you notice it. A cable system is moving a butterfly, which is responding at exactly the rate you are moving the pedal. A solenoid based system can respond much, much faster than the human input, meaning you have to make the transition smoother. So, I am not saying there is NO delay whatsoever in the system. The capability of the electronic system to respond is absolutely not the issue. The electronic system (pedal sensor, ecu and actuator) can respond about 1000000 times faster than the human brain can recognize. The issue when designing an electronic control system with direct human input is SLOWING the system down so that it plays well with humans.

If you read around and/or talk to many people that have replaced the stock flywheel with a lighter one, the common first response is "the delay went away!!" . So real life again supports what has been stated.

It does not matter if a flywheel is already moving. It takes the same energy and time to move it from 0 rpm to 700 rpm as it does 700 rpm to 1400 rpm. Flywheels have zero effect at static speed. The effect is on the CHANGE in rpm, regardless of whether it has already begun moving or not.

But either way, swapping to a lighter flywheel will make a nice difference in how fast the engine revs up (and keep in mind, it will also make it slow down faster as well). This portion of "delay" IS real and IS noticeable. So whatever delay is actually built into the system is summed with what you percieve as the engine revs increase. Making a large change in that part (via a lighter flywheel) makes a large perceived difference in the "delay"

Its funny sepa, that most times I have ever made input in the same thread as you (unless, of course if I am totally backing your statements) you attempt to come back and make out as if I know nothing about any of it, hence your last statement. Why not just discuss and actually back what you know or back your points, rather than simply trying to attack what I know by calling it "bogus" Obviously in the case of my flywheel explanation above, you were incorrect since you did not understand when and how rotational mass effects the system, so you can stop with trying to discredit. We can disagree, and that is fine, but disagree with valid arguments only, dont just try to discredit anything I say because you dont like my answers.

sleepermod

what is the problem when this happens? I would get this occasionally that is until I had readjusted the crack pressure for the EBC. Is this tune related or I need to install a bigger fuel pump to compensate for the bigger injectors?

You had this issue before Mr Meaty? Appreciate your input on this

SePaTc

Sure. :D

I don't care if you're Henry Ford. The TC's engine has an electrical/DBW throttle delay.

engifineer

Wow... you cant take enough time to read either... or you would have read that part of my reply. As usual sepa, you hear what you want to, close out the rest so you can pretend you know all the answers. And perfect rewording there to describe yourself... shut those ears when you dont understand the concepts or the arguments and keep spouting off the same answers. Bury your foot a bit deeper into your mouth ??

Another sore reminder of why so many avoid the forums more and more... too many kids who would argue with a tree.. even if the tree werent really arguing back

Mr_Meaty

i have the issue now...when I press on the gas, my AFR goes full lean and I get no response, ontill it finally get's enough fuel in there to rais the RPMs to get to a different part of the fuel map that dumps more fuule to bring my AFRs back in check and I get going. This is only when cruizing...when I'm in boost, it's instant cause my RPMs are hihging and I'm in a different part of my fuel map, so yeah, mine is ALL tune based.
I know this because I have like 4 different maps, and each one makes my car reacti differently at that point...one is really bad in lag, and when I log it's AFR at taht point, it's the leanest. Too rich give a similar effect, so you need it to be really steady.

Tuning is an art as much as it is a science.

sleepermod

Yes, I had that issue which you have correctly illustrated You're right, we do need to really pay more attention to the fuel map cell when it does its transition to the next. This is especially experienced when going WOT from a constant cruise speed. Yes, tuning is an art and it helps if you are familiar with how the engine behaves and pre-empting the fuel values for the acceleration enrichment.

Thanks Mr Meaty always right on the $$

SePaTc

your BS is so eloquent......


stop projecting hypocrite. i never said using a lighter flywheel won't improve throttle response and acceleration. you just can't get over that fact to see the real issue at hand can you???

Mr_Meaty

:D

nebster

ooooo did you use a thesaurus for that one?

Soulquarian

I don't have a wideband gauge, but looks like that's what I need to invest in. As far as I remember, I get that throttle lag whether I'm in boosting at WOT or not. I'll make sure to pay attention on my way home from work today.

rhythmnsmoke

+1. I was about to say possible dumping fuel at the moment of shifting though. But yeah, a tunning related issue.

Shaka_Z

you know... wouldn't it be nice if we could simply dial in a desired AFR number, which the computer would take and maintain in near-real time based on the sensor data and known engine characteristics? no more cells (i was never good at matrix math)

SePaTc

basically thats what our ecu does..... theres no need to be able to dial it in (on a stock engine anyway, which is why makers don't) because the only value the AFRS should be at is ideal, or as close as possible. Its not like you would want to lean it out under certain conditions.

Our ecu monitors air intake flow and exhaust gas emissions, as well as intake air temp, throttle position, and other inputs to properly modulate AFRS