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Lexus Mod Problem   2003-12-24 15:00:00 <trembath@...>
Hey Guys,

I have recently fitted 550cc injectors plus a Lexus air flow meter to my
7MGTE. Before fitting them I checked my standard mixture with an air/fuel
ratio meter and it was fairly constant at 14.7:1

Since doing the Lexus mod the upper mixture stays pretty much the same, the
idle mixture on startup is about 16.5 then goes back to 14.7 after a while.
When throttling off during deceleration the mixture leans out severely and
goes off the scale (>20:1).

I have checked heaps of things, changed my AFM sensor, throttle body (had
bored mine out to 65mm, have reverted to a standard 60mm one now), adjusted
the TPS position as per TSRM but this has not fixed the problem.

Thought it may be either:

1. Faulty TPS (when I had it off it seems to spring back very slowly and as it
appears to be pushed up by the throttle body and returns by it’s own spring I
wondered if it can’t close as quickly as the throttle body)
2. The modified Lexus AFM screw is not long enough (It’s roughly the same
length now as on Reg Riemers article, and it’s wound all the way in)
3. The computer needs more time to learn the new setup.
4. There’s a leak somewhere after the throttle body which draws in un-metered
air after the throttle body is closed and the plenum vacuum increases.

I don’t want to cause any damage to the engine by this ‘leaning out’, is this
possible on deceleration?

Anyone got any ideas?

Cheers
Rob
New Plymouth


Reply

Re: Lexus Mod Problem   2003-12-24 15:16:00 <Hunt M>
Unfortunatly I don't know what could exactly be causing that but all I can
say is WOW THAT IS LEAN!!!

But yes do check for vac leaks.
Is there an adjuster screw on the lexus afm?

Hunt

----- Original Message -----
From: trembath@world-net.co.nz
To: Supra Club of NZ Mailing List
Sent: 24 December, 2003 2:59 PM
Subject: [sconz] Lexus Mod Problem


Hey Guys,

I have recently fitted 550cc injectors plus a Lexus air flow meter to my
7MGTE. Before fitting them I checked my standard mixture with an air/fuel
ratio meter and it was fairly constant at 14.7:1

Since doing the Lexus mod the upper mixture stays pretty much the same, the
idle mixture on startup is about 16.5 then goes back to 14.7 after a while.
When throttling off during deceleration the mixture leans out severely and
goes off the scale (>20:1).

I have checked heaps of things, changed my AFM sensor, throttle body (had
bored mine out to 65mm, have reverted to a standard 60mm one now), adjusted
the TPS position as per TSRM but this has not fixed the problem.

Thought it may be either:

1. Faulty TPS (when I had it off it seems to spring back very slowly and as
it
appears to be pushed up by the throttle body and returns by it's own spring
I
wondered if it can't close as quickly as the throttle body)
2. The modified Lexus AFM screw is not long enough (It's roughly the same
length now as on Reg Riemers article, and it's wound all the way in)
3. The computer needs more time to learn the new setup.
4. There's a leak somewhere after the throttle body which draws in
un-metered
air after the throttle body is closed and the plenum vacuum increases.

I don't want to cause any damage to the engine by this 'leaning out', is
this
possible on deceleration?

Anyone got any ideas?

Cheers
Rob
New Plymouth



---
Supra Club of New Zealand
http://www.supras.org.nz/

(html version)
Reply

Re: Lexus Mod Problem   2003-12-24 15:45:00 <Jonathan Walker>
When I back off the throttle in my car the af guage whacks round to rich then drops off the scale.....does it really matter how lean it's running when you're decelerating or does it?
Regards,
Jonathan

ps - Hunt, just because there are adjuster screws doesnt mean they should be played with...FACTORY SET!! That's why they usually have a metal cap on them you have to break to get to the screw.
----- Original Message -----
From: Hunt M
To: Supra Club of NZ Mailing List
Sent: Wednesday, December 24, 2003 3:19 PM
Subject: [sconz] Re: Lexus Mod Problem


Unfortunatly I don't know what could exactly be causing that but all I can say is WOW THAT IS LEAN!!!

But yes do check for vac leaks.
Is there an adjuster screw on the lexus afm?

Hunt

----- Original Message -----
From: trembath@world-net.co.nz
To: Supra Club of NZ Mailing List
Sent: 24 December, 2003 2:59 PM
Subject: [sconz] Lexus Mod Problem


Hey Guys,

I have recently fitted 550cc injectors plus a Lexus air flow meter to my
7MGTE. Before fitting them I checked my standard mixture with an air/fuel
ratio meter and it was fairly constant at 14.7:1

Since doing the Lexus mod the upper mixture stays pretty much the same, the
idle mixture on startup is about 16.5 then goes back to 14.7 after a while.
When throttling off during deceleration the mixture leans out severely and
goes off the scale (>20:1).

I have checked heaps of things, changed my AFM sensor, throttle body (had
bored mine out to 65mm, have reverted to a standard 60mm one now), adjusted
the TPS position as per TSRM but this has not fixed the problem.

Thought it may be either:

1. Faulty TPS (when I had it off it seems to spring back very slowly and as it
appears to be pushed up by the throttle body and returns by it's own spring I
wondered if it can't close as quickly as the throttle body)
2. The modified Lexus AFM screw is not long enough (It's roughly the same
length now as on Reg Riemers article, and it's wound all the way in)
3. The computer needs more time to learn the new setup.
4. There's a leak somewhere after the throttle body which draws in un-metered
air after the throttle body is closed and the plenum vacuum increases.

I don't want to cause any damage to the engine by this 'leaning out', is this
possible on deceleration?

Anyone got any ideas?

Cheers
Rob
New Plymouth



---
Supra Club of New Zealand
http://www.supras.org.nz/
---
Supra Club of New Zealand
http://www.supras.org.nz/

(html version)
Reply

Re: Lexus Mod Problem   2003-12-24 15:48:00 <Stuart>
On Wednesday 24 December 2003 14:59, you wrote:
> Hey Guys,
>
> I have recently fitted 550cc injectors plus a Lexus air flow meter to my
> 7MGTE. Before fitting them I checked my standard mixture with an air/fuel
> ratio meter and it was fairly constant at 14.7:1
>
> Since doing the Lexus mod the upper mixture stays pretty much the same, the
> idle mixture on startup is about 16.5 then goes back to 14.7 after a while.
> When throttling off during deceleration the mixture leans out severely and
> goes off the scale (>20:1).

it's called overrun cutoff, and the ECU should have been doing that anyway -
it stops adding fuel under engine braking, as there is no point in doing it -
all modern cars do this.

Idle mixture will vary a bit, as there is a different size idle bypass - if
you really consider this a problem then fit a different idle adjustment screw
in the lexus AFM. this hsould make little difference on power though.

Sounds like it's working perfectly, really.

Why do you think there is a problem?

Regards,
Stuart W.

Reply

Re: Lexus Mod Problem   2003-12-24 15:51:00 <Hunt M>
Factory set is fine if you want to keep it factory.....but from what I know
the 7M didn't come out with 550 cc injectors or the Lexus AFM, not exactly
keeping it factory.....

Hunt

----- Original Message -----
From: Jonathan Walker
To: Supra Club of NZ Mailing List
Sent: 24 December, 2003 3:48 PM
Subject: [sconz] Re: Lexus Mod Problem


When I back off the throttle in my car the af guage whacks round to rich
then drops off the scale.....does it really matter how lean it's running
when you're decelerating or does it?
Regards,
Jonathan

ps - Hunt, just because there are adjuster screws doesnt mean they should be
played with...FACTORY SET!! That's why they usually have a metal cap on them
you have to break to get to the screw.
----- Original Message -----
From: Hunt M
To: Supra Club of NZ Mailing List
Sent: Wednesday, December 24, 2003 3:19 PM
Subject: [sconz] Re: Lexus Mod Problem


Unfortunatly I don't know what could exactly be causing that but all I can
say is WOW THAT IS LEAN!!!

But yes do check for vac leaks.
Is there an adjuster screw on the lexus afm?

Hunt

----- Original Message -----
From: trembath@world-net.co.nz
To: Supra Club of NZ Mailing List
Sent: 24 December, 2003 2:59 PM
Subject: [sconz] Lexus Mod Problem


Hey Guys,

I have recently fitted 550cc injectors plus a Lexus air flow meter to my
7MGTE. Before fitting them I checked my standard mixture with an air/fuel
ratio meter and it was fairly constant at 14.7:1

Since doing the Lexus mod the upper mixture stays pretty much the same,
the
idle mixture on startup is about 16.5 then goes back to 14.7 after a
while.
When throttling off during deceleration the mixture leans out severely and
goes off the scale (>20:1).

I have checked heaps of things, changed my AFM sensor, throttle body (had
bored mine out to 65mm, have reverted to a standard 60mm one now),
adjusted
the TPS position as per TSRM but this has not fixed the problem.

Thought it may be either:

1. Faulty TPS (when I had it off it seems to spring back very slowly and
as it
appears to be pushed up by the throttle body and returns by it's own
spring I
wondered if it can't close as quickly as the throttle body)
2. The modified Lexus AFM screw is not long enough (It's roughly the same
length now as on Reg Riemers article, and it's wound all the way in)
3. The computer needs more time to learn the new setup.
4. There's a leak somewhere after the throttle body which draws in
un-metered
air after the throttle body is closed and the plenum vacuum increases.

I don't want to cause any damage to the engine by this 'leaning out', is
this
possible on deceleration?

Anyone got any ideas?

Cheers
Rob
New Plymouth



---
Supra Club of New Zealand
http://www.supras.org.nz/
---
Supra Club of New Zealand
http://www.supras.org.nz/
---
Supra Club of New Zealand
http://www.supras.org.nz/

(html version)
Reply

Re: Lexus Mod Problem   2003-12-24 16:37:00 <trembath@...>
I was concerned that the lean running on deceleration may damage the engine,
I'm sure with the standard injectors/AFM it didn't go lean like that on
deceleration.

Quoting Stuart <stuartw@kcbbs.gen.nz>:

> On Wednesday 24 December 2003 14:59, you wrote:
> > Hey Guys,
> >
> > I have recently fitted 550cc injectors plus a Lexus air flow meter to my
> > 7MGTE. Before fitting them I checked my standard mixture with an air/fuel
> > ratio meter and it was fairly constant at 14.7:1
> >
> > Since doing the Lexus mod the upper mixture stays pretty much the same,
> the
> > idle mixture on startup is about 16.5 then goes back to 14.7 after a
> while.
> > When throttling off during deceleration the mixture leans out severely and
> > goes off the scale (>20:1).
>
> it's called overrun cutoff, and the ECU should have been doing that anyway -
>
> it stops adding fuel under engine braking, as there is no point in doing it -
>
> all modern cars do this.
>
> Idle mixture will vary a bit, as there is a different size idle bypass - if
> you really consider this a problem then fit a different idle adjustment screw
>
> in the lexus AFM. this hsould make little difference on power though.
>
> Sounds like it's working perfectly, really.
>
> Why do you think there is a problem?
>
> Regards,
> Stuart W.
>
>
> ---
> Supra Club of New Zealand
> http://www.supras.org.nz/
>



Reply

Re: Lexus Mod Problem   2003-12-24 16:41:00 <John Rosser>
other than raising the boost cut point about 5psi or so, what other reasons
is there for doing this upgrade?
other than getting a larger flow through the afm, i don't see the point of
spending almost a grand to get a few extra psi. the factory 440cc injectors
can flow enough fine for 15psi, which is as far as you can push the ct-26
anyway.

so whats the point?

john

----- Original Message -----
From: <trembath@world-net.co.nz>
To: "Supra Club of NZ Mailing List" <sconz@supras.org.nz>
Sent: Wednesday, December 24, 2003 4:36 PM
Subject: [sconz] Re: Lexus Mod Problem


> I was concerned that the lean running on deceleration may damage the
engine,
> I'm sure with the standard injectors/AFM it didn't go lean like that on
> deceleration.
>
> Quoting Stuart <stuartw@kcbbs.gen.nz>:
>
> > On Wednesday 24 December 2003 14:59, you wrote:
> > > Hey Guys,
> > >
> > > I have recently fitted 550cc injectors plus a Lexus air flow meter to
my
> > > 7MGTE. Before fitting them I checked my standard mixture with an
air/fuel
> > > ratio meter and it was fairly constant at 14.7:1
> > >
> > > Since doing the Lexus mod the upper mixture stays pretty much the
same,
> > the
> > > idle mixture on startup is about 16.5 then goes back to 14.7 after a
> > while.
> > > When throttling off during deceleration the mixture leans out severely
and
> > > goes off the scale (>20:1).
> >
> > it's called overrun cutoff, and the ECU should have been doing that
anyway -
> >
> > it stops adding fuel under engine braking, as there is no point in doing
it -
> >
> > all modern cars do this.
> >
> > Idle mixture will vary a bit, as there is a different size idle bypass -
if
> > you really consider this a problem then fit a different idle adjustment
screw
> >
> > in the lexus AFM. this hsould make little difference on power though.
> >
> > Sounds like it's working perfectly, really.
> >
> > Why do you think there is a problem?
> >
> > Regards,
> > Stuart W.
> >
> >
> > ---
> > Supra Club of New Zealand
> > http://www.supras.org.nz/
> >
>
>
>
>
> ---
> Supra Club of New Zealand
> http://www.supras.org.nz/
>


---
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Reply

Re: Lexus Mod Problem   2003-12-24 16:52:00 <Stuart>
On Wednesday 24 December 2003 16:36, you wrote:
> I was concerned that the lean running on deceleration may damage the
> engine, I'm sure with the standard injectors/AFM it didn't go lean like
> that on deceleration.

In which case there was something wrong with the standard setup - really, it
definately should do this.

Regards,
Stuart.

Reply

Re: Lexus Mod Problem   2003-12-24 16:55:00 <Andy S>
> > I was concerned that the lean running on
> deceleration may damage the
> > engine, I'm sure with the standard injectors/AFM
> it didn't go lean like
> > that on deceleration.

Leaning mixture on deceleration in conjunction with
the dashpot prevents the car from backfiring.

Cheers
Andy S

=====
Visit my website http://andy.supras.org.nz

Home of the 5MGE-->7MGTE conversion!

__________________________________
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New Yahoo! Photos - easier uploading and sharing.
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Reply

Re: Lexus Mod Problem   2003-12-24 16:55:00 <Stuart>
On Wednesday 24 December 2003 16:41, you wrote:
> other than raising the boost cut point about 5psi or so, what other reasons
> is there for doing this upgrade?
> other than getting a larger flow through the afm, i don't see the point of
> spending almost a grand to get a few extra psi. the factory 440cc injectors
> can flow enough fine for 15psi, which is as far as you can push the ct-26
> anyway.
>
> so whats the point?

very few people can get to 15PSI with stock setup, fuel cut is closer to
14ish, and lower for some people.
the 440 to 550 change gives you the ability to run *25%* more boost, or around
17.5 PSI.
Granted a stock CT26 is NOT going to like that - you are dead on with it's
limits, but throw a T03 wheel at it and it should be able to operate close to
this without being TOO bad (then again, certainly not optimal, but on a
budget...).

so, it's not a bad mid-budget option, especially for someone considering a
bigger turbo later on.

Regards,
Stuart W.

Reply

Re: Lexus Mod Problem   2003-12-24 16:57:00 <John Rosser>
what if there is another way of getting round the boost cut? would it still
be viable then? and no, i don't mean a fuel cut defender, i know what
everyone thinks of those, and i agree, they suck.

john

----- Original Message -----
From: "Stuart" <stuartw@kcbbs.gen.nz>
To: "Supra Club of NZ Mailing List" <sconz@supras.org.nz>
Sent: Wednesday, December 24, 2003 4:56 PM
Subject: [sconz] Re: Lexus Mod Problem


> On Wednesday 24 December 2003 16:41, you wrote:
> > other than raising the boost cut point about 5psi or so, what other
reasons
> > is there for doing this upgrade?
> > other than getting a larger flow through the afm, i don't see the point
of
> > spending almost a grand to get a few extra psi. the factory 440cc
injectors
> > can flow enough fine for 15psi, which is as far as you can push the
ct-26
> > anyway.
> >
> > so whats the point?
>
> very few people can get to 15PSI with stock setup, fuel cut is closer to
> 14ish, and lower for some people.
> the 440 to 550 change gives you the ability to run *25%* more boost, or
around
> 17.5 PSI.
> Granted a stock CT26 is NOT going to like that - you are dead on with it's
> limits, but throw a T03 wheel at it and it should be able to operate close
to
> this without being TOO bad (then again, certainly not optimal, but on a
> budget...).
>
> so, it's not a bad mid-budget option, especially for someone considering a
> bigger turbo later on.
>
> Regards,
> Stuart W.
>
>
> ---
> Supra Club of New Zealand
> http://www.supras.org.nz/
>


---
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Reply

Re: Lexus Mod Problem   2003-12-24 17:08:00 <Stuart>
On Wednesday 24 December 2003 16:56, you wrote:
> what if there is another way of getting round the boost cut? would it still
> be viable then? and no, i don't mean a fuel cut defender, i know what
> everyone thinks of those, and i agree, they suck.

Yes, there are a couple of other options, but very few that are as simple and
reliable as this, especially for a more simple user.

Of course, a simple 25% pulse length stretcher with suitable injector
drivers/receivers modded in would do the same thing (so long as it was
accurate enough), but they just don't easily exist. Add a frequency modifier
on the AFM and no physical mods would be needed - but considering the time
involved a set of 550's and a lexus AFM is probably much cheaper in the end.

Regards,
Stuart W.

Reply

Re: Lexus Mod Problem   2003-12-24 17:38:00 <trembath@...>
Thanks for all of your replies, has put my mind at ease...

One thing I didn't mention as I thought it wasn't relative to the issue I
raised, but I have fitted a larger T04 turbo also.

Thanks again for the help
Rob Trembath
New Plymouth

Quoting Stuart <stuartw@kcbbs.gen.nz>:

> On Wednesday 24 December 2003 16:36, you wrote:
> > I was concerned that the lean running on deceleration may damage the
> > engine, I'm sure with the standard injectors/AFM it didn't go lean like
> > that on deceleration.
>
> In which case there was something wrong with the standard setup - really, it
>
> definately should do this.
>
> Regards,
> Stuart.
>
>
> ---
> Supra Club of New Zealand
> http://www.supras.org.nz/
>



Reply

Re: Lexus Mod Problem   2003-12-24 18:06:00 <Cully Paterson>
<insert random Lexus AFM info that doesn't directly apply but is
interesting anyway>

I've discovered a little bit of info about the Lexus mod and possible
reasoning for the lumpy idle it causes, see:
http://www.7mpower.com/glenn_groseclos.shtml

"Also the Karman AFM was beginning to get quite finicky about working at
low RPM. With so little Air flow down low, the AFM didn't even register
above 3 Hz until 3000 RPM"

</insert>

It would appear that the low-flow accuracy of the AFM is pretty bad!
Explains why I can sometimes manage to get my car bunny-hopping at
70kph...

Cheers
Cully



Reply

Re: Lexus Mod Problem   2003-12-24 22:15:00 <Rob M>
So at what level does the Lexus AFM become the constraint assumming you
increase injectors beyond 550cc?
Rob
----- Original Message -----
From: "Stuart" <stuartw@kcbbs.gen.nz>
To: "Supra Club of NZ Mailing List" <sconz@supras.org.nz>
Sent: Wednesday, December 24, 2003 5:09 PM
Subject: [sconz] Re: Lexus Mod Problem


> On Wednesday 24 December 2003 16:56, you wrote:
> > what if there is another way of getting round the boost cut? would it
still
> > be viable then? and no, i don't mean a fuel cut defender, i know what
> > everyone thinks of those, and i agree, they suck.
>
> Yes, there are a couple of other options, but very few that are as simple
and
> reliable as this, especially for a more simple user.
>
> Of course, a simple 25% pulse length stretcher with suitable injector
> drivers/receivers modded in would do the same thing (so long as it was
> accurate enough), but they just don't easily exist. Add a frequency
modifier
> on the AFM and no physical mods would be needed - but considering the time
> involved a set of 550's and a lexus AFM is probably much cheaper in the
end.
>
> Regards,
> Stuart W.
>
>
> ---
> Supra Club of New Zealand
> http://www.supras.org.nz/

Reply

Re: Lexus Mod Problem   2003-12-24 22:58:00 <Stuart>
On Wednesday 24 December 2003 22:15, you wrote:
> So at what level does the Lexus AFM become the constraint assumming you
> increase injectors beyond 550cc?

You cann't - lexus AFM suits only 550cc injectors, the injectors and the AFM
need to be larger by the same amount, so 550cc is the only usable size (well,
maybe 540 or 560 would be ok.. just a bit leaner or richer)

Regards,
Stuart W.

Reply

Re: Lexus Mod Problem   2003-12-27 22:29:00 <trembath@...>
It would seem that it is normal for turbo engines to lean out on engine
breaking, from what I have read this is usually to around 16-17:1 air/fuel
ratio.

My 7MGTE on start up is around 18:1, settles down to a 14.7:1 idle and stays
around that till full throttle, on engine breaking it leans out to around 20:1

From what I also read on the net, 14.7:1 (stoichiometric) is fine for idle/mid
range but slightly richer around 12.5:1 is recommended for full throttle (WOT)
to aid in cooling the engine.

Is this 20:1 A/F ratio acceptable on engine breaking?

Is my richest figure of 14.7:1 ok, particularly at a boost of say 15psi?

If it’s not ok, what can be done with a stock (auto) computer to richen up the
A/F ratio?

Cheers
Rob Trembath
New Plymouth

> On Wednesday 24 December 2003 16:36, you wrote:
> > I was concerned that the lean running on deceleration may damage the
> > engine, I'm sure with the standard injectors/AFM it didn't go lean like
> > that on deceleration.
>
> In which case there was something wrong with the standard setup - really, it
>
> definately should do this.
>
> Regards,
> Stuart.



Reply

Re: Lexus Mod Problem   2003-12-27 23:44:00 <Stuart>
On Saturday 27 December 2003 22:29, you wrote:
> It would seem that it is normal for turbo engines to lean out on engine
> breaking, from what I have read this is usually to around 16-17:1 air/fuel
> ratio.

it is normal for all engines to lean out to basically infinity:1 ratio - since
they stop putting ANY fuel in during engine braking (as there would be
absolutly no point putting any in) - this is just an example of the fact that
oxy sensors don't actually give accurate measurements.

> My 7MGTE on start up is around 18:1, settles down to a 14.7:1 idle and
> stays around that till full throttle, on engine breaking it leans out to
> around 20:1

sounds fair enough, allowing for the massive inaccuracy of oxy sensors.

> From what I also read on the net, 14.7:1 (stoichiometric) is fine for
> idle/mid range but slightly richer around 12.5:1 is recommended for full
> throttle (WOT) to aid in cooling the engine.

yes, but not to cool the engine - it helps produce a bit more power (for a
number of quite subtle reasons that would take a reasonably large book to
learn), and it stops 'detonation', which is bad for the life of your engine

> Is this 20:1 A/F ratio acceptable on engine breaking?

any ratio is acceptable on engine braking, but the leaner the better - trust
me, the ECU is not putting ANY fuel in once it goes into it's proper engine
braking mode - if it is, there is a fault. Note however that is does take a
little while for the 'remains' of fuel sitting around the intake system to
all filter through the engine.

> Is my richest figure of 14.7:1 ok, particularly at a boost of say 15psi?

Does sound a bit lean - how are you managing to run 15PSI without fuel cut?

> If it’s not ok, what can be done with a stock (auto) computer to richen up
> the A/F ratio?

Simply, nothing can be done (assuming this is a 7M-GTE). if it is running too
lean then there is a reason (ie: a fault) - my gut feeling is that you are
running a fuel cut defender to get a bit of extra boost - in which case you
are getting exactly what you (sorry to say) deserve - if not, then there is a
nother problem, maybe an air leak (probably pre-turbo), maybe a dodgy AFM, or
a stuck injector (is the car running smoothly?) - could be many things.

An after market ECU, or more realisticaly a dodgy mod to a standard ECU, is
about the only normal way to change this - or the lexus/550cc mod, but that
still required everything else to be working.

Regards,
Stuart.

Reply

Re: Lexus Mod Problem   2003-12-28 02:15:00 <trembath@...>
See my answers below

>> Is my richest figure of 14.7:1 ok, particularly at a boost of say 15psi?
>
>Does sound a bit lean - how are you managing to run 15PSI without fuel cut?
>
Answer: I am using the Lexus/550cc injector mod on a 7MGTE, this raises the
fuel cut. The standard setup also gave a maximum 14.7:1 A/F ratio.
>
>> If it’s not ok, what can be done with a stock (auto) computer to richen up
>> the A/F ratio?
>
>Simply, nothing can be done (assuming this is a 7M-GTE). if it is running too
>lean then there is a reason (ie: a fault) - my gut feeling is that you are
>running a fuel cut defender to get a bit of extra boost - in which case you
>are getting exactly what you (sorry to say) deserve - if not, then there is a
>nother problem, maybe an air leak (probably pre-turbo), maybe a dodgy AFM, or
>a stuck injector (is the car running smoothly?) - could be many things.
>
Answer: Am not running a fuel cut, read enough to realise this is dodgy. Car
is running smoothly, the Lexus AFM I obtained had no sensor, so I fitted the
standard one and the computer immediately gave a code 31 fault, have since
tried a loaned sensor which worked fine, purchased another from Jason which
also worked fine and duplicated the results from the loaned sensor. Given that
the A/F maximum ratio was the same before the Lexus mod and I have changed the
AFM, the AFM sensor, replaced all of the piping etc before the turbo, replaced
the throttle body, replaced the injectors, what else could it be? The ECU, the
TPS (when I had this off it seemed a little slow to return back on its own
spring), the ISC valve, the oxygen sensor itself?
>
>An after market ECU, or more realisticaly a dodgy mod to a standard ECU, is
>about the only normal way to change this - or the lexus/550cc mod, but that
>still required everything else to be working.
>
>Regards,
>Stuart

Regards
Rob

Reply

Re: Lexus Mod Problem   2003-12-28 07:21:00 <Rob M>
Stuart,
aside from LexusAFM & 550 injectors wht other mods have you done? Have you
had the car on a dyno before & after the change & if so what were the
results?

Rob M.
----- Original Message -----
From: <trembath@world-net.co.nz>
To: "Supra Club of NZ Mailing List" <sconz@supras.org.nz>
Sent: Sunday, December 28, 2003 2:15 AM
Subject: [sconz] Re: Lexus Mod Problem


> See my answers below
>
> >> Is my richest figure of 14.7:1 ok, particularly at a boost of say
15psi?
> >
> >Does sound a bit lean - how are you managing to run 15PSI without fuel
cut?
> >
> Answer: I am using the Lexus/550cc injector mod on a 7MGTE, this raises
the
> fuel cut. The standard setup also gave a maximum 14.7:1 A/F ratio.
> >
> >> If it's not ok, what can be done with a stock (auto) computer to richen
up
> >> the A/F ratio?
> >
> >Simply, nothing can be done (assuming this is a 7M-GTE). if it is running
too
> >lean then there is a reason (ie: a fault) - my gut feeling is that you
are
> >running a fuel cut defender to get a bit of extra boost - in which case
you
> >are getting exactly what you (sorry to say) deserve - if not, then there
is a
> >nother problem, maybe an air leak (probably pre-turbo), maybe a dodgy
AFM, or
> >a stuck injector (is the car running smoothly?) - could be many things.
> >
> Answer: Am not running a fuel cut, read enough to realise this is dodgy.
Car
> is running smoothly, the Lexus AFM I obtained had no sensor, so I fitted
the
> standard one and the computer immediately gave a code 31 fault, have since
> tried a loaned sensor which worked fine, purchased another from Jason
which
> also worked fine and duplicated the results from the loaned sensor. Given
that
> the A/F maximum ratio was the same before the Lexus mod and I have changed
the
> AFM, the AFM sensor, replaced all of the piping etc before the turbo,
replaced
> the throttle body, replaced the injectors, what else could it be? The ECU,
the
> TPS (when I had this off it seemed a little slow to return back on its own
> spring), the ISC valve, the oxygen sensor itself?
> >
> >An after market ECU, or more realisticaly a dodgy mod to a standard ECU,
is
> >about the only normal way to change this - or the lexus/550cc mod, but
that
> >still required everything else to be working.
> >
> >Regards,
> >Stuart
>
> Regards
> Rob
>
>
> ---
> Supra Club of New Zealand
> http://www.supras.org.nz/
>

Reply

Re: Lexus Mod Problem   2003-12-28 11:17:00 <Stuart>
> Answer: I am using the Lexus/550cc injector mod on a 7MGTE, this raises the
> fuel cut. The standard setup also gave a maximum 14.7:1 A/F ratio.

Ahh, in this case I would say that there is probably no problem - an actualy
14.7 would probably be a bit low. but is that figure from a oxy sensor? if so
it is only very approximate anyway, so I would not be overly concerned.

> Answer: Am not running a fuel cut, read enough to realise this is dodgy.
> Car is running smoothly, the Lexus AFM I obtained had no sensor, so I
> fitted the standard one and the computer immediately gave a code 31 fault,
> have since tried a loaned sensor which worked fine, purchased another from
> Jason which also worked fine and duplicated the results from the loaned
> sensor. Given that the A/F maximum ratio was the same before the Lexus mod
> and I have changed the AFM, the AFM sensor, replaced all of the piping etc
> before the turbo, replaced the throttle body, replaced the injectors, what
> else could it be? The ECU, the TPS (when I had this off it seemed a little
> slow to return back on its own spring), the ISC valve, the oxygen sensor
> itself?

In this case I suspect there is no problem - I would be interested in how you
have arived at the 14.7 figure though.

How about your plug colours - do these indicate that you are running rich or
lean?

Regards,
Stuart.

Reply

Re: Lexus Mod Problem   2003-12-28 16:38:00 <trembath@...>
Stuart,

I am using a kitset Jaycar KC5300 Fuel Mixture meter (has an LED scale and a
digital A/F ratio display)which has been setup for petrol using the supplied
instructions i.e an 1.8 kohm resister and a 1V power souce. This is connected
to the oxy sensor, admittedly this meter has not been calibrated against a
reliable source, but given that the ECU seems to keep the mixture at around
14.7:1 thru the lower and mid range I thought this would also show a rich
mixture at WOT.

Rob

Quoting Stuart <stuartw@kcbbs.gen.nz>:

> > Answer: I am using the Lexus/550cc injector mod on a 7MGTE, this raises
> the
> > fuel cut. The standard setup also gave a maximum 14.7:1 A/F ratio.
>
> Ahh, in this case I would say that there is probably no problem - an actualy
>
> 14.7 would probably be a bit low. but is that figure from a oxy sensor? if so
>
> it is only very approximate anyway, so I would not be overly concerned.
>
> > Answer: Am not running a fuel cut, read enough to realise this is dodgy.
> > Car is running smoothly, the Lexus AFM I obtained had no sensor, so I
> > fitted the standard one and the computer immediately gave a code 31 fault,
> > have since tried a loaned sensor which worked fine, purchased another from
> > Jason which also worked fine and duplicated the results from the loaned
> > sensor. Given that the A/F maximum ratio was the same before the Lexus mod
> > and I have changed the AFM, the AFM sensor, replaced all of the piping etc
> > before the turbo, replaced the throttle body, replaced the injectors, what
> > else could it be? The ECU, the TPS (when I had this off it seemed a little
> > slow to return back on its own spring), the ISC valve, the oxygen sensor
> > itself?
>
> In this case I suspect there is no problem - I would be interested in how you
>
> have arived at the 14.7 figure though.
>
> How about your plug colours - do these indicate that you are running rich or
>
> lean?
>
> Regards,
> Stuart.
>
>
> ---
> Supra Club of New Zealand
> http://www.supras.org.nz/
>



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