SePaTc

a few thoughts:

1) your right, its an I4, i think your expectations were too high.
2) auto tranny I4 cars are dogs. thats why you think its dying. how r u even getting up above 3000, the ecu decides your shift points for you. you won't get a realistic feel for the tc's powerband until you drive a 5 speed.
3) the DBW does suck on the tc. def needs to be improved. pretty sure they build a delay into the system and the throttle plate doesn't actually open fully at WOT, more like 85%
4) So you have an IS300, so i guess you're pretty familiar with the Toyota DBW system....since your car has the exact same system. And hence why many IS300 tuners choose to swap out for a cable throttle body, especially when boosting.
5) your right, many people can't take criticism of the tc, and they will attack you for speaking the truth. though as i've stated, i think your logic is a bit flawed.
6) at partial throttle the timing is not as aggressive as at full throttle. and below 3000, the timing is more conseravtive than above 3000.

2azfe makes no power from like 1000-2250, starts to build at that point. by 3000-3500 you can get a nice pull if you stomp on it. tq peaks around 4000, give or take a few hundred, but still makes power up until about 6000 provided you've removed some intake and exhaust flow restrictions.

Token

With modern OBDII I doubt its a physical problem such as a missfire or faulty injector.

SePaTc you pretty much got it.

1) yeah, its an I4, been a while since I've driving an I4 a lot, good point.
2) The car is not a dog!! Its just the throttle has its moments of feeling totally un-natural (read here, its not ALL THE TIME, but sometimes). With the heat Toyota has had lately with its DBW tuning, I don't see how the logic is flawed. If CAMRY OWNERS can feel that something is wrong with the DBW to the point that it generates a TSB from Toyota, then its VERY possible something IS WRONG with their tuning (dbw) as of late.
3) Like I was saying.
4) Many tuners decide to swap out? The few running non lexus OE throttle bodies did so to accommodate larger charge piping (3+"), and they welcomed the loss of dbw. But also MANY swapped to a larger (ls400) lexus DBW throttle bodies to keep DBW. But also MANY other peeps both boosted and NA have altered the OE throttle body to defeat DBW because yes, it sucks. MANY keep it because they want to retain cruise control, one going as far as swapping in a SupraTT DBW throttle body. Many of the Aristo swap peeps keep the Aristo DBW throttle body. Define many.

5) I knew better, but I wanted to start fingering out what was going on, whatever criticism it brings my way from hurt egos, I learn to sift through it. I will be the first to tell someone all the dislikes and flaws I think are in the IS 300, but I remember back in the day how I'd get defensive, real quick.
6) This fact may explain what I'm feeling, thanks for putting that out there.

Her tune is weird. This whole thing stemmed from her complaining how the car damn near burns out when she takes off from a stop trying to drive normally. Its very peppy down low IMO. So I started to play with it more an more after this thread and my opinion went from timing, to dbw, and I messed up by not thinking of the auto tranny at all. 90% of the time its f'ing fast, but I can mess with it and get the condition where it feels like the DBW motor clutch isn't doing what my right foot is asking it to do.

I like this car, and happy she got it (she is coming from a Matrix, we both like Toyota a lot). But in the right conditions I can get the throttle to be un-natural, much worse than the tune on my IS.

Thanks for the informative post SePaTc, props for having a level head.

Token

Here is a potential expensive way to get around the DBW lag but retain cruise control (not having to clock things around, DTCs get thrown and throttle clutches burning up).
http://www.jdm-option.com/eng/parts/06_12/direct.html

IMO I bet it intercepts the Petal Position Sensor (PPS), amplifies it to the ECU causing the ECU to send a more aggressive signal to the DBW clutch, reducing delay and giving it more pep.

Steventc07

It IS the auto. I had one (yes I regreted so much), then traded it in on a manual. OMFG what a difference. Its like not even the same car. In the auto i would be like wtf go already and it would shift sooooooo slow and easy. In the manual it pulls on a whole new level. And when u want to....wheelspin

Stardust

You guys are brutal! LOL. I used to drive manual, but I wanted something for the daily bumper to bumper traffic in LA, and I want to be able to drive in heels.

Don't listen to my b/f, he is a dork! hahahaha.

SePaTc

with my 5 speed that i've been driving for 3 years, starting out in 1st, i can either launch smoothly, or bunnyhop slowly...i find it very difficult to start out smoothly slowly--which i attribute to a combination of the dbw and the pedal feel.

WTF is a "DBW motor clutch"? please fill me in on this. i will totally agree that the throttle response does not correlate very well to the input from your right foot. It responds AFTER you input. And its almost too touchy. you can actually press the pedal down a few millimeters and get NO response. Then as soon as you cross that point, the rpms just shoot up. its been a very annoying 3 years.....

CarbonXe

iTrader: (1)

Lol, that's when I get my first kick of power, and if the tires don't break loose (I'm on the wear bars..) then they'll break loose at 3800 when I get my second spike of power. Don't know why, but ever since I got my Intake, I've had the strangest power curve.



It's like that . Very official btw.

Token

DBW is not a stepper motor, it uses a clutch to move the throttle plate until it gets to where the TPS wants it to be in relation to the PPS, DBW dictates the aggression/style in which this goes down. Plus there is Toyota's DBW that has "learning" that is in the IS 300, and in the new Camrys with the TSB, but I don't know if its in the tC, but its likely.

Shaka_Z

hmmm... if only the dbw was driven by a stepper... we wouldnt have this problem. I have no issues with electronically actuated systems in general, but the way this is implemented is just so over-complicated.

why the hell does a throttle body need a clutch when a stepper will do the job so much more consistently???

mengsta

And Septc, i know waht you mean about not being able to launch slowly. I drive so many others, starting off smooth n slow is a bit harder. If you go to 1.5rpm starting off too soon, it like stops for awhile den goes. you gotta like stay under 1.5rpm until yur fully off the clutch. As in where my old suby (friend let me borrow it) was so much easier to drive. And it does sck how if u press a lil bit, and it does nothing, den wen u give it just a tab but more it revs too much, u gotta be really precise.

Token

I'm thinking because with a clutch it can be a lot smoother and linear, a stepper motor would be jerky and if a glitch were present could put you from idle to WOT in a millisecond.

To modify the throttle body (if internally its very similar to the IS 300s) to delete DBW it requires some clocking and re-locating where the cable is connected to the butterfly valve shaft (the DBW is a weird mix of real throttle control of 0-50%, and then the rest is via the DBW clutch), but also disconnecting power to the DBW motor so that its not putting its 2cents into the equation. You loose cruise control, and you have a CEL (possibly would put you in limp mode).

As mentioned before the 50%-50% relationship. The delay you guys are describing at idle/off the line may be more to do with a spring in the throttle cable system. On the IS boards there are threads to either use vacuum tubing to fully compress the spring, or remove it completely.

Steventc07

I am not saying the auto is bad. I still loved that car. But I personally would rather have a manual and was just saying the performance is much better with the manual. And you can get more out of the engine reliably b/c you dont have to worry about burning up the auto tranny.

SePaTc

okay, i was pretty sure before, but now i'm almost positive that you are either a bit confused or just have no clue what your talking about.

THERE IS NOT THROTTLE CABLE ON THE TC!!!

And i'm fairly certain there is no "clutch" in the throttle body either.

Its electronically controlled. The TPS determines the angle of the pedal, relays that signal to the ecu, which relays to the throttle body, telling the plate how much to open. I'm not sure how the plate is actuated, but i've never heard anything about a clutch system being used in the tc's throttle body.

I'm really doubting this info. Did u just get this from the IS300 forums and assume that the tc uses the exact same dbw system simply because they are both toyota-made??? eventhough the 2jzge is a TOTALLY different motor than the 2azfe.

i mean, is there anyone else that can confirm this, cuz otherwise i think you're wrong.

yeah, the dbw system sucks in the tc.... dont' think it has anything to do with a throttle body clutch and certainly nothing to do with any cables....since neither the clutch nor throttle system has any.

Token

Quoted from you
If this is not the case, so be it. My older (IS) DBW system does have a throttle cable present, its a weird mix of cable control and in the later opening range DBW.

If yours is purely electronically controlled via a foot pedal sensor to then operate the throttle butterfly valve, there is still a TPS in the throttle body assembly itself to tell the ECU were in reality the throttle position is.

This system is even MORE intrusive.

I have the girl's car today to re-due the trunk, I'll go out and look.

I never claimed to know the internals of the tC DBW physically, and should have disputed your "exactly the same" comment.

I do, how ever, know what I'm talking about with the IS-300. Read the words carefully, your making statements that are out of context.

Token

Holly f'ing shiznicks, no cable at all.

I wondered why the IS 300 wasn't like this from the get-go. Baby steps I guess.

Well looks like you guys can't easily mod to become DBW-free.

Your throttle reaction time, throttle position and feel is all up to the program/algorithm. Thought it wasn't all in my head. It could be the auto tranny milking it in certain conditions, but that would generate a lot of heat, and then these trannys will have a short life span.

CuRiOuSfIsH

I guess the bottom line is, that is the way the tC is.......... kind of have to accept it. IMO, DBW w/ a delay on an auto is..... ok, but having owned a manual tC, it's rather weird.
No, auto tC is not a swift car (dont let the torque deceive you), and it's not much quicker than other cars w/ smaller 4 cylinder motors.

Mid_Life_tC-risis

CarbonXe how'd you get your rev limiter up to 7K!

Reading this thread reminded me of all the "throttle delay" complaints from several years ago. Some said you have to live with it, totally due to dbw, but some said it wasn't an issue after modding their cars, and I'm a believer in the latter. I have an auto tC and remember the first couple months of driving it - before bolt-ons - and had similar issues with the throttle. Launch it way too hard = wheel hop, just a little too hard = maintain grip but get thrown back into the seat, too soft on the throttle = lurch away awkardly. It's been a while since doing my bolt-ons and not sure exactly which one helped the most, possibly a combination, but my throttle now is VERY predictable. I'm sure part of it is developing a feel for the throttle but I can say I have had no more awkward launches and the power delivery throughout the band - except for the dreaded auto downshift lag - has been very smooth since doing breathing mods.

Token/Stardust here are 2 mods that I believe will help with your throttle response:

(1). Straight-through muffler: The stock muffler is a baffled/chambered design with a valve that opens up under pressure around 3K rpm, for the purpose of high rpm mufffling:

click & scroll down for pics stock muffler

It's possible the obviously restrictive design of the chambers & baffles + spring-loaded valve actuation on the stocker may cause enough transient variations in exhaust backpressure to affect combustion enough to appear to be poor throttle response. Also replacing with a straight-through also shows a dyno-proven 5-6whp (for stick, auto slightly less) gain over stock:

https://www.scionlife.com/forums/viewtopic.php?t=80070

(2). Cold air intake: Again, not sure whether this mod or the straight-through helped more, but the ECU reads intake air flow with a MAF sensor, and it doesn't matter how much the intake can actually flow, it's how much of that flow is actually sensed by the MAF. I don't think the stock airbox is particularly restrictive, just that some intakes do a better job of producing more stable & higher MAF readings, possibly by reducing turbulence at the MAF, which again may be an issue manifesting itself as poor stock throttle response. The Injen CAI - which I have & recommend - dyno'ed the best in this shootout:

https://www.scionlife.com/forums/viewtopic.php?t=92108

I would also recommend one more mod - lowering springs (or coilovers). So much of a car's response is feel and stiffer springs helped out a lot in that department. The tC's suspension is biased heavily to ride comfort and not performance. The soft stock springs make the car squat on hard launches & dive on hard braking. With stiffer springs improved cornering is a given, but they also took out most of the squat & dive as well, making power delivery & braking feel WAY smoother. If you're worried about scraping fenders go with TRD, the drop is only 1.25" and have nearly identical spring rates to my Tein H-tech's.

Hey the auto will never rev as hard or fast as a stick - especially stick with lightweight flywheel, and the downshift lag sucks, which I get around by downshifting manually at times, but the auto has been a great DD for me (60 mile r/t for work). I believe you will enjoy your auto tC more with these mods, they're relatively cheap and easy, I would estimate you'd pay under $500 total for CAI, springs (vice coilovers), and either DIY or exhaust shop for good muffler (vice aftermarket axleback).

If others have similar experiences post up with your mods, I can only say what worked for me.

Token

Simply awesome response Mid_Life_tC-risis.

I dropped the car on Eibach Sportline springs (which is why I had the car today to try to find a rattle from possibly not putting one of the trunk moldings back on properly) and I really like the sportieness its added to the car, which is not bad stock IMO, but now the body roll is reduced a lot, now the damn rebound needs to be put in check. Also I was surprised how close to stock the alignment was able to get to after the week of letting the springs settle. The only thing out of spec is the rear tires being at -1 degree camber.

I'm in the search for better struts now (she doesn't want to do anything more with the suspension, but sooner than later the OE shocks will give out). I love Koni, but maybe Tokico HPs are good enough. Time will tell.

Stardust, a rear sway would be nice also lol.

Again, thanks for the post up. Good stuff. I'm looking forward to a SoCal meet to to able to talk about this stuff face to face, and see other rides. If anyone wants to see an 5speed IS 300 w/ 6 point roll cage running on a megasquirt standalone I can bring that heap out also.

SePaTc

pix/vidz dyno/time slip plz?

Token

No time slips, not a fan of the 1/4.

No dyno, still street tuning the MS. Lots to learn for me, this is a first for me. I was an electricians mate in the Navy my first four years, so finguring out the wiring, values and such to get it to work plug and play wasn't too too hard, but this tuning thing though simple to understand in write ups is new waters for me. When done I do plan on doing an OE ECU pull at the closest dyno to me (harmanmotive) and then a MS run back to back.

Right now the engine is pretty much stock, the MS will be of benifit for a raised red line while autox'ing, and I do plan on doing the bolt on Aristo swap soon.

Here are some pics of the heap.





Now with padding


Light weight battery now in trunk


Getting ready for teh tuning. Built a junction box for all the wideband wiring and for the calibration button w/ LED, plus extending the gauge wires and gave it a plug.

And what she looks like from the outside, nice and stock'ish.



Dang, a lot of picks.