1jz 1/4 throttle same as full throttle? [Archive]

naten

21-11-2007, 12:55 AM

hey guys,

Just a quick question for anyone who might know, is it normal for 1/4 throttle to yeild the same acceleration/boost as full throttle? I havent checked the numbers on ye old gtech but it feels almost identical. Its so close that i took a mate for a drive and he couldnt notice the difference either.....

Am i being paranoid or is something askew?

Car is a MA61 with a 1jz, everything stock except fmic and 3" zorst from the dumps back. Car runs pretty good other wise just a slight hesitaion before full boost (approx 3-4k).

Nath

Vios-GT_07

21-11-2007, 02:03 AM

:P

my 4A-G does exactly the same thing.. i drive with barely 10% throttle most of the time.. and going from 1/4 to full throttle is only induction noise and the engine works slightly harder.. and i got that hesistation just before 3000 rpms, though i've narrowed it down to either the fuel pump being worn, the muffler being an S-flow with a valve to make it straight through under load, and the distributor needing a service.

oldcorollas

21-11-2007, 02:13 AM

at lower rpm, the amoutn of air going into engine is less... so you might be able to hit full boost at half throttle...

what does boost gauge tell you when you are at 1/4 or full throttle?

at higher revs, is it the same? ie, 6000 or 7000rpm?

naten

21-11-2007, 05:09 PM

vios: Thats practically the same sumptons i have tho there are a few difference in the cars (4a vs 1j) i dont think the zorst would cause it tho. I guess maybe the fuel pump could

oldcorollas: There is literally no viewable difference in a 0-100 run at a 1/4 throttle and a 0-100 run at full throttle. Boost is the same (peak and when it comes on) and speed feels the same. It also pulls the same through to 7k. The hesitation feels almost the same but it isnt as pronounced with 1/4 throttle.

which is confusing me.

Things im thinking it could be. TPS or maybe fuel pump?

I would of thought the fuel pump would cause a lack of performance though rather then something like this.

Thats odd can any else see my reply as the first post and dated some time in 2002?

oldcorollas

21-11-2007, 05:32 PM

if it is fuel pump then it will do catastrophic things at higher rpm.

perhaps the pump cannot maintain the pressure required for the boost level, but if it runs out of flow, you will go lean, and it will either ping or cut when you run it to 7K.

first thing you need to do is get it on a dyno, or borrow a wideband oxygen sensor to check the AFR's. if the AFR's are ok, then it is not fuel.
if on the dyno it is making the same power at 1/4 throttle and full throttle, then either the throttle is too big, or you have a massive restriction in the system.
if the power is what you would expect, then it is just the throttle being too big for the rev range you are using ;)
basically, chuck it on the dyno and see if there is actually anything wrong before chasing things.

vios, that is normal to use small throttle.
full throttle is meant to be "too much" at max rpm WOT... so you usually need to use very little, and at say, 3000rpm, you need much less air than at 8000rpm

naten

21-11-2007, 06:49 PM

hmmm will wander down in the next few days and see if i can get her dynoed

Yea that makes me think the fuel pump is ok. Agreed best way to know is a dyno test and suss things out from there.

I checked over the TPS as per these specs:
http://mkiv.supras.org.nz/articles/engine_2_41.htm

And it was all within spec with the exception of the idle switch. I had to wind the idle screw completely out for it to register 0v at idle. Now the problem is the throttle isnt cracked open at all so the idle is only around 500 and stalls when coming to a stop.

Would you suggest i adjust the tps slighting so idle is at 0v ? Ive been told the tps is very fiddly and not to mess with it. I did take it off but i didnt adjust it, i removed it via the housing that it sits on.

If i dont adjust the tps i can just wind the idle screw back out but it means the tps wont drop to 0v and indicate idle to the ECU.

chris davey

22-11-2007, 01:49 PM

silly question but, have you checked how much 1/4 throttle is actually opening the TB? Ie, it could actually be more than that.

Sometimes it is the simplest things :P

thepeter

22-11-2007, 01:58 PM

agreed with chris davey - check the throttle cable tension, it's not too tight/loose?

naten

22-11-2007, 05:29 PM

checked the cable and how it opens etc and its normal

so flat in the car is full on the TB quater is a quater etc etc

Getting the TPS to go to 0v at idle fixed my idle rpm variations (would hunt 200 rpm) but its idling a little low. Ive backed the idle screws all the way out so the TB is 100% closed, would it matter if i crack the throttle a bit to keep a decent rpm?

What im assuming is that its ok to do this as long as the IDL pin on the TPS is still at 0v at throttle shut.

Im meant to be getting the car dynoed tommorrow morning so ill have a better idea whats doing then (as long as i dont whimp out, $95 a run seems a bit steep)

wilbo666

22-11-2007, 05:41 PM

The procedure for setting up the TPS has a few steps if I recall,

The first step is to adjust the throttle stop if I recall,

Then adjust the TPS.

When adjusting the TPS it isn't about getting the output to 0V as such, it is a range.

Also you need to set it up so that the IDL contacts are closed at idle, and then break at the specified clearance...

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/FI/FI_101.gif

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=101

Cheers
Wilbo

naten

22-11-2007, 07:54 PM

ok im playing around with it now. +rep for ur help :)

Its within specs listed.

The only thing i cannot figure out is where to set the idle stop screw to start with. As in how much it should be opened to before adjusting and taking measurements etc

any ideas?

naten

22-11-2007, 07:56 PM

unless thats whats written on the page and i cant read it

Kyosho

22-11-2007, 08:13 PM

naten: As has been said, it is often quite sensible to not fully require 100% throttle to feel like you're at full noise

In alot of cars, 80% of your power is made with 25 - 30% of the throttle, the last 20% isn't exactly noticeable in seat of your pants.

The last part is, are you sure you're using 25% throttle? I'd be thinking you're using alot more.
I used to beleive I was only using 10-15% throttle when accelerating normally, when I did a datalog from my ECU, I'm actually using 25% throttle, but it feels MINIMAL!
I'm betting your "25%" is really alot more then 25% and more like 50%

Also, at around 50%-60% throttle, my car "feels" the same, as at 100% throttle, but if I watch the boost guage, I'm actually held back by a psi or two, and flattening it fully yields full boost, and there IS more power, but not HUGELY noticeable. (But it's there... ;) )

naten

22-11-2007, 08:48 PM

positive about throttle position have been playing with it for ages now.

hit a brike wall.

I havent adjusted the tps yet as im unsure where the throttle stop screw should be to start the hole process.

Where im at: the car now idles awesome when first started once its fully warm and i have hit some boost idle is around 500rpm and it will stall most times coming to a stop.

I can up the idle screw to make the idle higher but it then mean that the TPS will have to be adjusted back to give me the 0v at idle thing.

sound right?

naten

22-11-2007, 08:56 PM

for future refernce dont use blue thread locker on idle screws

its not easy to move

got the shits with it.

I left the idle screw where it was and adjusted the tps so that the idle clicks off at 0.75mm gap

Going for a spin now with the gtech

naten

22-11-2007, 10:24 PM

ma61+1jz+gtech+rain= not good :)

ok idle is pretty much ok now its still a little low (600rpm) but atleast its not cutting out.

Nothing really changed hesitation is still there though it does seem the slightest bit better on the throttle (as in full does more then 1/4). The problem is still there though and is quite pronounced.

Dyno should reveal some more info tomz

Wildsupra

22-11-2007, 10:28 PM

ok havent read the whole thread so excuse me if this has already been mentioned, have you got the traction control butterfly in the throttle body? if so is it stuck at 1/4 oping by any chance? cos if it is then no matter wot you do with the foot throttle you wont get any more flow than whatever the traction butterfly is open at.

Norbie

22-11-2007, 11:31 PM

Agree with the above. This doesn't sound like a tuning problem, the only way this could really happen is if there's some big restriction somewhere in the inlet system which makes the last 75% of throttle opening redundant. It could be the trac butterfly or something else, like a blocked intercooler perhaps? Actually even a blocked exhaust (eg collapsed cat) might cause similar issues.

naten

22-11-2007, 11:48 PM

Im pretty sure i dont but i may be wrong. There is only one butterfly and that has the TPS on one side and the throttle cable/linkage on the other.

It looks like this one:
http://wwwrsphysse.anu.edu.au/~amh110/all_gifs/Turbo%20page%20gifs/FrankC_1JZ-GTE.jpg

Its been the same through 2 different intercoolers so i dont believe they were both blocked. They were both cleaned too.

The cat i can check myself just by pulling it out and having a look yea? Was a cheapy at the time so it is possible i guess.

I still have this hunch that the hesitation is fuel pressure related.

Ill hopefully know more tommorrow, ill keep yas posted.

Oh btw thanks for the help guys :)

Wildsupra

23-11-2007, 08:40 AM

well according to that pic there is no traction control butterfly so that counts that out.
Block cat would normally equal very low power, it seems your still describing good power?
Check it to be sure, also check that you are actually getting full throttle with the pedal.
Is this a sudden new prob or has it always been like this?

I also doubt its fuel related as if 1/4 to full throttle makes no difference your engine would prolly blow if it was fuel leaning out that much.

Matty

Wildsupra

23-11-2007, 08:42 AM

one other question how much boost does it make at 1/4 throttle? and how much at full throttle? does it vary between the 2? If not i'd say ya wastegate might be leaking/stuck open.....or ya factory BOV is jammed open causing the pressure to vent back into air filter intake.
Once again excuse me if this has been mentioned still havent had time to read whole thread.

naten

23-11-2007, 10:33 AM

Im really glad i chose to go this morning....

Dyno chart here:
http://img210.imageshack.us/img210/8755/dsc01045tk5.th.jpg (http://img210.imageshack.us/my.php?image=dsc01045tk5.jpg)

Anyone guess whats wrong here? Its so piss lean its not funny. Basically once it starts making boost it leans out and keeps heading leaner. Starts around 14:1 he stopped when it was heading towards 17.5:1

Its very scary that the car would of been like that for the last 100,000k and ive done heaps of thrashing etc in that time too :(

I bought a walbro on the spot and will put it in this arvo or tommorrow.

I believe this will be the cause of my hesitation and 1/4 -> full throttle feeling.

Just angry at myself i didnt get the car dynoed earlier!

wilbo666

23-11-2007, 11:23 AM

Edit: I'm silly :)

But on that note choosing a full scale value of 270kw when it made 75 is silly :P

Cheers
Wilbo

Enigma-Penguin

23-11-2007, 11:27 AM

It looks fine to me wilbo , 30 kw to about 75kw with the afr starting at just under fifteen and climbing...

well not fine, but you get what I mean ...

wilbo666

23-11-2007, 11:34 AM

It looks fine to me wilbo , 30 kw to about 75kw with the afr starting at just under fifteen and climbing...

well not fine, but you get what I mean ...

Oh I'm just an idiot ;) I read it the other way around ;)

Cheers
Wilbo

CrUZida

23-11-2007, 12:27 PM

The only thing i cannot figure out is where to set the idle stop screw to start with. As in how much it should be opened to before adjusting and taking measurements etc
Are you talking about the screw that determines how far the throttle plate is open when your foot is off the pedal?

If so, the throttle plate is supposed to be 100% closed at that time.
With the throttle plate closed, and the TPS in IDL, the ECU will regulate the idle RPM with the ISCV.
You'll probably have to readjust the TPS after closing the throttle plate though, otherwise you'll experience bad idle and stalling again.

Set IDL to open when the throttle is just cracked a mm or so. Ignore all the other things to do with the TPS. IDL is the only important one. (assuming you've verified that the TPS is working correctly)

naten

23-11-2007, 02:07 PM

Cruzida:

Yea thats exactly what i was talking about thanks :)

I get how to do the rest of the adjusting i just didnt know where to put the throttle to start with. Im going to just take the idle screw out or should i leave it slightly in so the throttle closes on that? wont damage the throttle by letting it snap shut like this?

Yea the TPS is within spec for everything else.

Thanks man +rep 4 u

rob

23-11-2007, 02:18 PM

CrUZida

23-11-2007, 06:22 PM

Im going to just take the idle screw out or should i leave it slightly in so the throttle closes on that? wont damage the throttle by letting it snap shut like this?
Leave the screw in, you'll need it if the TPS or ISCV stuffs up and you need a temp fix to stop the stalling.

The dashpot will stop the throttle from snapping shut.

naten

23-11-2007, 06:41 PM

hahahaha good on ya rob as if i even mentioned you.

As if i was scared, actually i was. Crazy hungarian man driving my car at speed through the nasho :)

I feel like such a noob, i guess the only way to learn is experience.

Excellent info thanks cruzida will fix it up now!

23-11-2007, 06:47 PM

just a thought...

Is the vac line on the fuel pressure regulator ok?

Had a 4agte do very similar things with the AFR when the FPR vac line fell off.

whatthe?

23-11-2007, 06:59 PM

I'd be checking your fuel filter and voltage at the fuel pump as well. It's common to find a voltage drop of up to 3v in that run of wire in a MA61. A new pump wont help you if that's the case

Wildsupra

23-11-2007, 07:21 PM

Man you must get some awesome economy outta that car :)

naten

23-11-2007, 07:34 PM

JP: had already checked it couple of days ago when doing tps :) thanks for the suggestion tho

about average i believe 10-13 lp100kms under 10s if just on the express way

but i suppose that is under my daily drivers numbers

should rang some bells hey :(

oldcorollas

23-11-2007, 08:33 PM

dumb question time...

are you absolutely sure that the fuel pressure reg is getting manifold pressure, and has no cracks or leaks? and is not on the bleed valve line for the wastegate?

that could be the reason that you have such crap AFR...

naten

23-11-2007, 08:47 PM

yea i did a triple check just then, its plumbed off the plenum after the TB nothing else on that line. No leaks or cracks i can see or test (breath pressure)

unless the FPR itself is shagged.

I thought it was because im running the stock ma61 pump. It *might* be wiring if the voltage drop is bad enough. I knew either way the stock pump should be replaced so im not going to be pissed if its not that.

CrUZida

23-11-2007, 08:53 PM

Unless the stock pump is uber fucked it should be more than sufficient to deal with up to 5psi of boost. ie cruise and low loads should be fine.

I definitely wouldn't want to run any more boost than that.
Especially when you consider the price of a Walbro vs the price of another 1jz.

However, if the line is kinked or blocked, or the filter is blocked, then thats an entirely different story.

Put new pump in, test.
If still back, test pressure in fuel rails.
If up to shit, replace reg.

whatthe?

23-11-2007, 08:58 PM

The wiring was bad enough in both of my MA61s to cause issues. Takes 2 mins with a meter to check. You can get to the fuel pump plug on the tank by taking out 3 screws

naten

23-11-2007, 09:59 PM

The fact that the pump and wiring is now 24 years old and done 350,000kms prob doesnt help either.

I cant remember how mos wired up my fuel pump but i think its through the normal fuse box in the engnie bay. Am i best to run a new relay off the battery and use that as the switch or just replacing that wire from the fuse box to the pump is enough?

I have a new fuel filter to put in at the same time. The fuel filter wouldnt be causing the restriction would it? its just a normal metal straight throught jobbie for EFI cars. Cant see it being an issue but you never know.

Either way new pump is going in so i may as well redo the wiring at the same time.

Fixed up the TPS too so all should be good on that side of things now.

Ill keep yas posted!

whatthe?

23-11-2007, 10:01 PM

If Mos did the wiring it'll be via the circuit opening relay in the drivers side kick panel. It's the wiring from there to the pump which runs up the drivers side of the car that often gets dodgy. A nice heavy gauge wire from relay to pump will fix the issue if you notice voltage drop at the pump plug.

That being said a walbro is a no-brainer regardless of wiring condition

naten

23-11-2007, 10:06 PM

Yea the wiring side of its a piece of piss just wasnt sure bout what bits to replace.

Thanks man! Ill probably replace it anyways just to be sure.

naten

24-11-2007, 08:26 PM

Pump has been installed with much success!

The hesitation is gone and it pulls alot harder (i think rob will agree with that). I cant believe how much punchier it is now :)

The pump is seeing 12v so i didnt have to worry about rewiring it.

Clutch has started to slip on hard launches now so it looks like ill be up for a new one soon :)

Ill have to get it back on the dyno soon too.

Idle is still shitty though, i set the tps with the throttle 100% closed and it doesnt idle when coming to a stop. Im thinking ill just crack the throttle a bit and set the tps off that position.

Thanks everyone for your help and advice.

CrUZida

25-11-2007, 04:47 PM

I'd reset the ecu after resetting the TPS/throttle to be 100% closed.
May take a bit for the ecu to realise how much air is required from the ISCV.

Failing that the dashpot isn't working properly.

naten

25-11-2007, 04:57 PM

hmmmmm

i have reset the ecu twice since then. I just redid it as i said above and the normal nice idle is back but thats with the throttle cracked and the tps set off that.

The dashpot is the little black thingy that sits right next to the tps? It doesnt have any wires or anything else coming into it. By the looks of it, it just cushions the throttle closing but i might be wrong?

Kyosho

25-11-2007, 04:59 PM

Is your ISCV working?
Have you adjusted the ISCV bypass screw if it has one?

naten

25-11-2007, 05:09 PM

as far as i can tell its working.

I can hear it click when i turn the motor off, all the resistance values are ok when i tested it. ITs getting power etc etc. I also cleaned it at the same time when i had it off.

AFAIK there is no adjustment on them

CrUZida

25-11-2007, 06:02 PM

The dashpot is the little black thingy that sits right next to the tps? It doesnt have any wires or anything else coming into it. By the looks of it, it just cushions the throttle closing but i might be wrong?
Yeah. thats the one, and thats what it does.

naten

26-11-2007, 12:12 AM

EldarO

26-11-2007, 05:03 AM

i had to wind mine in a tad to drop my idle down.

since then (11 months)

ive had no issues, car idles at 700rpm, higher on cold start.

wilbo666

26-11-2007, 06:15 PM

hmmmmm

i cant see how it would be faulty there isnt much to them. It does have a little adjuster nut on it. Maybe its not shutting 100%

Seems odd they would have like 3 different places for idle screws to go and your not meant to use any of them.......

Can anyone with a 1jz confirm that i should of removed all my idle screws?

Don't remove them...:)

Have a search for 2JZ throttle body settings, I recall reading in the past the dimensions that the stops should be set too :)

Cheers
Wilbo

naten

28-11-2007, 08:10 PM

hmmm ive done some searching on here and google and i cant seem to find them

doesnt matter its cracked open slightly and idling good so im not to fuzzed if its 0.1mm off

thanks guys!

amichie

05-12-2007, 10:03 AM

I have found that if your static ignition timing is too far advanced then 1/4 throttle will be good but full throttle will cause the knock retard to cut in making it feel as though its bogged down or strangled.

This doesn't explain your air fuel ratio issues but its worth looking at the static timing.

CrUZida

06-12-2007, 03:10 PM

Can't change static timing on a 1JZ

naten

08-12-2007, 12:03 AM

ill check timing but im pretty sure all is running as it should at the moment.

My disco meter (jaycar a/f) now heads rich instead of lean and the flat spot/hesitation is now gone. This is thanks to a new fuel pump.

Im going over the car and repairing all the major rust so the cars is off the road atm but once its done im going to get it dynoed again just to make sure all is well.

I couldnt find any setting for the throttle body screws so if someone knows where they are hiding please let me know!