Thread: idle bypass valve

Phil, all of the above is based on my knowledge of working with fuel injection systems and knowledge gained from industry and my own reasearch over 20 odd years.

[quote=PhilipA;1068164]Well , my bootleg photocopy of the 1987-1992 Paper Workshop manual says the following at test 17? of the injection test procedure[QUOTE]

TPS- Check throttle potentiometer
Throttle closed 0.085-0.545 volts with smooth swing between closed and open.
Open throttle 4.2-4.9 volts.

My understanding is that the TPS does not set the position in the base map on idle, the MAF does this, along with input scaling from the temp sensors. The TPS is like an accelerator pump in that it richens the mixture dependent on the speed of voltage increase (as stated above in the Workshop manual).

The MAF monitors the airsflow consumed by the engine.
The TPS is not an accelerator pump. Its a rheostat. It gives out a constant variable signal on its position to tell the ECU what degree of opening it is so it can then inject the correct amount of fuel. This input to the ECU tells it how long the injector pulse should be based on this position. It has nothing to do with the 'speed of voltage increase'. It doesnt even mention anywhere about speed of rise, so I'm not sure where you get this from.
On a rising voltage meaning an opening throttle, it increases the open time, then holds it at that setting until it changes either up or down. On a reducing voltage, it shortens the injector pulse reducing fuelling and holds it at that setting until it changes, again either up or down.

If it were so critical how would the ECU allow overrun cut off on TPS's set to the upper end of the scale? as they would never see 0.33-0.35Volts. ie how would the ECU know that the throttle was closed ie LIFT UM FOOT.

You stated yourself that the throttle closed voltage was 0.085 - 0.545, doesnt 0.33-0.35 fall in this range?????
Not sure what you mean by "set to the upper end of the scale"??? You mean 4.9v ???? Again, "CLOSED VOLTAGE" is 0.085 - 0.545V. Anything inside this puts the ECU into overrun.
The open throttle refers to Wide Open Throttle, not just "open somewhere between closed and full.

If you rotate the TPS , particularly quickly then of course it will richen or lean the mixture as that is what they do.

Yes, because the TPS is telling the ECU the throttle position has opened further requiring more fuel. How much is totally dependent on where the throttle is in its 90 deg of full available rotation. But as to the speed of how quickly it opens, its make absolutely no difference to it.

The Rover V8 site ://www.britishv8.org/Articles/Rover-14CUX-EFI.htm also just repeats the Manual info plus a bit. BTW, just because British tuners do it does not mean it is correct. If you look at the above site's next para on O2 sensors it is wrong, as the sensors are fed 12v, and do not work opposite to other narrow band sensors .

This is basically because there are more Rover performance houses in the UK than anywhere else in the world. These are not just on LandRovers, in fact LR performance is in the minority scale compared to MG, Triumph, TVR and other vehicles powered by the Rover V8.
Most sites wholly refer to TVR and MG vehicles with only a very few references to LR, however, the process is the same with minor changes to tuning values.

FYI, British V8 are not a performance house, they are a "knowledge borrower/reposter" who take and directly copy I might add, known and speculative info from other sources and post it up on a website.
I have found numerous errors on there website as they have really no professional experience not to mention there is nothing on there that isnt already widely known. On top of this, he wants to charge you $20 a year to tell you this??
And just on the subject of British V8, they are in the US, not the UK, hence the reason they know nothing......

RPi Engineering specify 0.33-0.35 but I do not know where they got the info from.

They get their info from performance figures based on the performance chips they worked in conjunction with Mark Adams on. G33 have slightly lower rating which reflects

Now I recall I set mine at 0.33-0.35 using the Rpi info on the old manifold but it did not seem to make any difference.

I would appreciate it if you could quote the wording in your manual as I am intrigued that it would change.

The wording in my Factory manuals (that are not bootlegs ) is no different to yours Phil, however I have 20 years experience in the engine game including both diesel and petrol fuel injection, road and performance. Its knowledge from my profession, not just from tinkering.

Have a look at this page from G33. Fuel injection
I would suggest you have a look at this page as it will explain exactly how the 14CUX operates. They give you far more info than even RPI do.
British V8.org are not a professional outfit. They really are nothing more than a backyard enthusiasts newsletter.
Hope this helps to explain everything.

Cheers

Andrew

Originally Posted by spook

thanks andrew but im not sure what the opening size is with the butter fly when closed, it seems to be closed none of my feeler guage sizes fit though so i just need the size of the opening when closed thanks luke.. and can you adjust with the to screws in side on the butter fly cheers.

Like I said, the top and bottom of the butterfly must be within 0.5mm.
Have attached a diagram for you
You cant measure it with feeler gauges, you need a depth vernier.

The screws inside are for the butterfly mount, not the adjustment. Dont unscrew these at all as they are a splayed screw to stop them coming loose. Unscrew these and you wont get them to re tighten again!

If your not confident, safest way is to not attempt it yourself. There should be plenty of people on this site who know how to do it and may be in your area. I'm in WA so probably a little too far away...
Ask and you stand a very good chance of receiving!

Cheers

Andrew.

Lovemyrangie, as a result of your passionate arguments in defence of the TPS, I went down and checked mine seeing I had not done it for several years and 80KK.

Mine was at the very lowest end at 0.22 volts, and with great difficulty I set it to 0.335 volts ( as mine is a Thor with a Heath Robinson adaptor), and yes it does seem to make some difference to idle quality, although the difference seems to be less at voltages over 0.335, than from 0.22 to 0.335.
It may perhaps reduce my only driveability problem of stall after hot start, but its hard to say as mine is so modified, although it has always done it to a degree , even before any mods, so it may be a problem with my individual ECU.

I still have some trouble with your insistance about the TPS role in the engine control which was probably due to my poor explanation. The point re the "accelerator pump" is that the TPS is a leading indicator of fuel demand as the MAF and o2 sensors are lagging indicators. This causes the fuel air to be richer on throttle positive movement than it would be only with MAF and or O2 sensor control, hence it is "like" an accelerator pump.

Without a TPS it is likely the engine would backfire from leanness with quick throttle application as the injection band width would not keep up with air mass.

The point re overrrun is that if the TPS was "crucial" to be at 0.335 and it was say at 0.5 then the ECU would not know of closed throttle . ie the ECU is tolerant of a wide band of TPS voltages. Maybe 0.335 is OPTIMUM but the engine runs perfectly well within the Workshop Manual parameters. You seem to concede this.

I have read the G33 page , but AFAIR there is NO reference to TPS in it. It added nothing , and for a "tinkerer" , I think I have a pretty good understanding, I have grafted a 14CUX onto a Thor, and added O2 sensors by working it out myself without "professional help" as no professionals I spoke to knew anything about it.



Regards Philip A

Phillip, I am not in defense of anything. I have quite a bit of experience in working with different injection systems over 20 years and have solved the problems of a number of members here who now swear by them, not to mention those who have made alterations through their own research as I have also done.

But it does seem by your last post that you are slowly coming around!

I'm not conceding the TPS doesnt run at voltages set contrary to .33-.35V. In my own and others experience, settings under or over this result in hunting, load stalling, hot starting problems, driveability and overall economy issues where O2 sensors are not used.
The TPS is tolerant to the range of the closed throttle voltage range, I dont dispute that at all and I cant see where I have, but it is only in respect to those ECU's employing O2 sensors.

As yours is quite different in configuration, I do not expect it to solve your issues but it may provide you with a base to start from, but for those who have issues, these methods and settings are tried and true around the world.

Anyway, Spook hope you can glean something from this and find the happy medium.

Regards

Andrew.

But it does seem by your last post that you are slowly coming around!

Funny , I was thinking the same thing.

Please remember that I was/am trying to help Spook by simplifying/minimising what to do to get his car to idle. There is a quote that "Everything in life is a simplification" .


Regards Philip A

Originally Posted by PhilipA

Funny , I was thinking the same thing.

Please remember that I was/am trying to help Spook by simplifying/minimising what to do to get his car to idle. There is a quote that "Everything in life is a simplification" .


Regards Philip A

thanks fellas for all the help, it seems to be idleing a lot better,but still a little slow, but has not stalled so happy with that, just a quick question i been doing a little reading up on the idleing with the range rover,and read about the SPEED TRANSDUCER apparently that can play up with the idleling , so does anybody no about this and how to test i no where it is but what and how to check this thanks luke..

and read about the SPEED TRANSDUCER apparently that can play up with the idleling , so does anybody no about this and how to test i no where it is but what and how to check this thanks luke.. 18th September 2009 10:28 AM

Spook are you trying to start another 50 postings.
In simple terms if your speedo works your speed transducer is working.

The speed transducer controls idle up while moving and also injector cutoff on override over 1500RPM with car moving.

To roughly see what it does just put your transmission in neutral as you are just moving, then stop. You will see the idle is up at around 1000RPM while you are moving and drops down when you stop. AFAIK this is to stop stalling when you stop. Nearly all injected cars I have driven have this.

Also look at your tach if you have an auto when overriding ie foot not on accelerator at all. If you have an auto you will see the revs jump as they pass through 1500RPM as the injectors restart. you can get slightly better economy by changing back to 3 on an auto while descending hills over 60 KMh or in 4 over 80 Kmh.
Regards Philip A

SPOOK
I would pay more attention to ...

Set up the butterfly with verniers
Then reset the TPS
Then adjust base idle bypass

... As Phillip said ... if your speedo works perfectly ...