Jump to content
The mkiv Supra Owners Club

Stock vvti running VERY rich


samdale

Recommended Posts

As per my recent Dyno run here: http://www.mkivsupra.net/vbb/showthread.php?341410-Standard-VVTI-TT6

 

You can see my car is running rather rich.

My biggest clue so far has been the torque app looking at fuel pressures.

 

I'm not sure where the stock sensor(s) are but there are 2 that give a reading within the app. I will try and do some pulls and get some data logged tomorrow.

 

The one reading i am interested in shows the idle fuel pressure at around 80psi but I've read on here that it should be closer to 35-40psi? On WOT this rises to around 500! What should it be?

 

So a few questions.

 

Assuming the pressure is accurate, what would cause this? Blocked return? Faulty fpr? Can the stock pump even make this kind of pressure?

 

Assuming the reading is not accurate and is maybe kpa but showing as psi, is there any way to "tap in" to accurately measure pressure? I can get hold of an accurate gauge say 1/8" npt if there is somewhere to attach it?

 

Any easy way to check if afr is ok after I've checked things rather than paying a garage each time?

Link to comment
Share on other sites

Someone must know something about fuelling?

 

If the numbers are to be believed, this is a screenshot of torque when revving the car from idle to around 5k

 

image

 

 

Visual check of MAF looks ok, sparkplugs are denso iridium IK20 and look like this

 

image

 

A good amount of carbon so definitely over fuelling for some reason???

 

Anyone know of any tests for stock fpr and if it can be adjusted or easily replaced??

Link to comment
Share on other sites

The supra's don't have a fuel pressure sensor fitted, There must be something wrong your Torque app.

I have a vvti supra and the torque app and I do not get fuel pressure because there is no sensor.

 

The base fuel pressure is about 3 bar / 43 psi, base pressure is when the pump is running and there is no vac/pressure hose connected to the regulator.

The vac/pressure line is there to keep the fuel pressure constant to the manifold pressure, so if you have 1 bar of boost the fuel pressure will rise to approx 4 bar and the same happens when the manifold is in vacuum ie -1 bar vac the fuel pressure will be 2 bar.

 

So the max pressure that should be seen on a std bpu supra would be about 4.5 bar.

 

As you have the torque app I would use this to check the long term fuel trims (I will not explain about fuel trims there is plenty on info on the net) if the fuel trim is in the negative it means that the ecu is pulling fuel to keep it running at the right AFR, if this is the case it could be the fuel pressure is higher than normal or the O2 sensor is faulty along with other reasons.

 

apparently there is not one long term fuel trim used on a global scale, but several. Not sure how to read them all. Maybe one of the toyota ecu guru's could answer?

 

The fuel pressure regulator in the stock supra can not be adjusted and it is easily replaced ( which I doubt there is anything wrong with it ) and you can check the fuel pressure, one way would be to remove the outlet connection on the fuel filter and place in a Tee fitting for a pressure gauge, and before you ask I don't what size threads etc to use.

 

The O2 sensor keeps the fueling at the correct AFR for normal running but is ignored when running in the higher boost area but is used to set the short term fuel trim which in turn adjusts the long term fuel trim if needed, and as far as I know the long term fuel trim is used when in higher boost area.

It would not hurt putting in a new 02 sensor as this may help the fueling at higher boost levels if the sensor is out of spec.

 

In your screenshot of the fuel pressure gauge what are the numbers along the bottom line supposed to mean? ( 1 to 9 )

 

 

Also looking at the spark plug is not meaningful as far as I aware, not unless the engine was switched off at the time it was running rich and not allowed to idle etc.

 

If you get this sorted please post up the answer to the problem as it might help others with the same/similar problems.

 

 

 

hope this helps.

 

Regards Chris.

Edited by chrispot (see edit history)
Link to comment
Share on other sites

Stock cars run usually rich at wide open throttle.

 

In a MAF meter car, having a boost leak will cause the AFR to go very rich, so I would check that first. Put a PVC plastic port on the top IC hose coming from the turbo with a tire valve with the inside thing in the valve removed and put some pressure in the system, you should hear hissing if there's a leak some where.

 

http://www.benzworld.org/forums/r170-slk-class/1545447-diy-boost-leak-tester.html

Link to comment
Share on other sites

Thanks gents, will certainly have a look at testing for leaks.

 

I believe the 1-9 in torque is just time. I.e. is shows a rolling 10second graph.

 

I know what you mean about posting answers though, too many threads turn up in a search just to lead to a dead end!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. You might also be interested in our Guidelines, Privacy Policy and Terms of Use.