Modified URS6 running rich

[S4Marc]

Pressure test done, another friendly UK member kindly lent me the bungs last week

One imagines the car has been mapped on the side of caution rather than all out knife edge power

[prj]

Yea I would borrow someone's stock pressure regulator and try it, your 1 bar high which is a lot. Be careful at wot. Drive with the wastgate N75 disconnected to keep boost down for safety and stay off wot. Get it on a rolling road and check fueling at wot, then reconnect N75 and test again.

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Be careful at WOT because of too high fuel pressure? Care to elaborate exactly what it's gonna do apart from being down on power?
Then somehow someone deduced that 0.82V on a narrowband lambda sensor is somehow 0.82 lambda and then multiplied that by 14.7? Really?

This thread just makes me want to smash my hand through my forehead.
I know you want the best, but this thread is going to go nowhere at this rate.

1. Pressure test the car. If you don't have closed o2 control at part throttle it means load is too high (MAF signal too high) and there is no regulation, you will never ever pass emissions that way. 4 pages of yadda yadda and still no pressure test done. Sorry if this sounds super harsh, but IMO if you are too helpless to go to a plumbing store, buy a couple plastic pipe bungs then buy a tyre nipple at a tyre shop, cut a hole and put the nipple in it, blank the pcv then pressure test the car with 0.5 bar through the maf accordion hose - maybe fixing cars isn't for you?
2. Fuel pressure - if there is regulation at idle, even with 5 bar fuel pressure, then that means fuel is not that badly out, besides going from 4 bar to 5 bar only adds 10% of fuel. Most likely the car has a massive boost/vacuum leak, so there is little vacuum pull on the regulator, and the car also has a 044 fitted, and with those the fuel pressure is always 0.7-1 bar higher than normal on hot idle with the stock FPR, you just map around it.
3. The AFR on the dyno is way too rich, about 1 point of AFR rich across the range.

[diesel des]

Yea I would borrow someone's stock pressure regulator and try it, your 1 bar high which is a lot. Be careful at wot. Drive with the wastgate N75 disconnected to keep boost down for safety and stay off wot. Get it on a rolling road and check fueling at wot, then reconnect N75 and test again.

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[twoqu]

All we can say is that it looks as though the fuel pressure is too high and its the fpr job to regulate the pressure. It's certaintly consistant with your issue - overfueling, but whether its THE issue or not we cannot tell. It's got to worth a stab as its a relatively easy replacement.
Can't remember that far back for the 3bar Vmap but as the whole point of the Vmap was being adjustable I think it does have a stock 2.5 bar setting. On this subject I seem to recall a Vmap version having some sort of external adjustability via the throttle pedal although I don't think that would effect fueling anyway. However it might gives us the stock option if you wish to go down that route purely for the MOT.
Might be worth taking a bit more time examining that catch can pipework as per your other thread incase somehow that is effecting the engine breathing. You will need to either explain the routing or add some pics so that people more knowledable can work out if its functioning correctly.
PM incoming.

[S4Marc]

Would this be a suitable FPR?

https://www.fuelpumpsonline.co.uk/ma...ar-18369-p.asp

and this as a rail adaptor
https://www.aetmotorsportshop.co.uk/...6t-fpr-adapter

[S4Marc]

A 3bar VMAP sensor has been fitted according to the history aswell as

Siemens #60 (60lb at 3bar injectors) from 034


I think in the short term I'd like to pursue remedying the car as it is then if time passes I agree that making the car work in standard form is a very sensible idea and great platform to work back from

Will hopefully order a new FPR but not the standard one as I've read they've reduced the return hole size which would exasperate my issue

I will run the car off boost initially just to test if the C0 comes back, then fit a wideband

Do you feel reducing the fuel pressure by an additional 1bar, to the current 4.2 barg under vacuum, would result in a stoich idle and no load rev?

[S4Marc]

Little update

Idle fuel pressure no vacuum is 5.2 barg
idle fuel pressure vacuum is 4.2 barg (manually pulled a vacuum to 25inhg)

The FPR is stamped 4.0 bar

Just to clarify there is no confusion between gauge and absolute readings?

[twoqu]

Ok thats useful to know. Certaintly 034 had their own chips for the 3071 for example.
Depending on the map sensor used, there is a possibility that you could convert the ecu back to stock temporarily (for the MOT). The ecu would need to be fitted with a Vmap which allowed the map sensor to be configured in 3 different settings, 2.5bar, 3bar and 4bar. That is if MRC used it rather than an alternative. You would need to be brave enough to open the ecu up to check. If it has a Vmap then you would need to place the jumper back to the 2.5 bar settings (making note of where it was presently positioned!) and then we could burn some stock chips, fit stock injectors, verify fuel pressure is correct and then it has a much better chance of passing the emissions assuming it is not what you fear, a MAF issue. Even if it is, this would be a low cost verification if the same fault existed.
I know it seems a retrospective step to take but the logic is if it cannot pass as stock, then its not going to pass as modified. If the issue is on the car it will show up.
That still doesen't stop you testing the things you can. The engine needs to be leak free and the fuel pressure needs to be correct and ideally no fault codes.
If the goal is to get it through the emissions then hopefully you see what I mean. Obviously whatever the fault is will need to be rectified subsequently. Unless anybody knows definitively that a maf can go that badly out of calibration to produce those errors.

[S4Marc]

Looks like there is no exemptions for us! Bloody computers!
So you need to be in the 0.3 CO, min Lambda 0.97, max lambda 1.03 range to pass. So going on the lambda value posted earlier you have an afr of @12.2 on what should be a cruise rather than a full throttle, when it should be nearer 14.7 or leaner. Not sure whether a Maf can cause that amount of overfueling.
Certainly its worth persuing the fuel pressure issue as I don't think the deka's (if thats what you have) would need more than 4 bar if they are the 630cc injectors. Have you actually pressure tested it yet to eliminate any air leaks?
What do you know about the modifications. Who mapped it or is it a generic chips set from somewhere? What are the injectors, can you make out any part numbers?
Is the car known to the forum so we can read up on its history?
I think its possible to get it MOted but not necessarily in its present form as essentially it only needs to pas on the day under those conditions

The Injectors are Siemens (will update later once I've checked paperwork)

The engine was built by white cottage quattros

The fuel pump is a Bosch high output 044

Most of the parts are from 034

The car was mapped by Mihnea at MRC

The Dyno printout was a little time later at Surrey rolling road

[S4Marc]

Appreciate everybody's help so far, going to do alot of tinkering tonight after work

[S4Marc]

Did their tester show lambda while you had the different co readings.

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I forgot to look at the lambda value at idle

The 0.82v lambda was noted on fast idle

[diesel des]

I took her for a long drive to clean out the pipes before Saturdays MOT, oil temp was about 80'c

At natural idle the CO dropped to 0.78% (a pass is 0.3-0.5)

On the fast idle test (2.5-3krpm) it failed miserably at 7.2% CO

Mine is a 1996 car

Did their tester show lambda while you had the different co readings.

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[twoqu]

Looks like there is no exemptions for us! Bloody computers!
So you need to be in the 0.3 CO, min Lambda 0.97, max lambda 1.03 range to pass. So going on the lambda value posted earlier you have an afr of @12.2 on what should be a cruise rather than a full throttle, when it should be nearer 14.7 or leaner. Not sure whether a Maf can cause that amount of overfueling.
Certainly its worth persuing the fuel pressure issue as I don't think the deka's (if thats what you have) would need more than 4 bar if they are the 630cc injectors. Have you actually pressure tested it yet to eliminate any air leaks?
What do you know about the modifications. Who mapped it or is it a generic chips set from somewhere? What are the injectors, can you make out any part numbers?
Is the car known to the forum so we can read up on its history?
I think its possible to get it MOted but not necessarily in its present form as essentially it only needs to pass on the day under those conditions

[S4Marc]

On a stock AAN the fuel pressure should be 4.0-4.2 bar at idle. As Des has said it should drop by 0.5 bar when vac connected. However as the car is not stock we don't know whether this increase in base fuel pressure is intentional or a bad fpr! There were 5 bar fpr available but they were expensive so the alternative was to modify a stock one by crushing it a bit to increase the fuel pressure to what was required.
It does seem to be nearly 1 bar out of whack from that guage so it might be worth double checking if you have access to another more accurate one as a check.
Don't forget the fpr sets the base fuel pressure througout the range so swapping it out will effect fueling under all the operating conditions not just idle. It would be less rich with a 4 bar fpr than a 5 bar fpr but not at the proportional difference between the two.
Also the lambda is not closed loop on these so after some threshold above idle it goes open loop.

Will re check the fuel pressure later with a more accurate gauge scale and eventually if the cause fit a wideband to make sure remedying the idle doesn't lean her out at WOT

[S4Marc]

There used to be two different catagories for emissions where one was a lot more generous! The cut off was Aug 95 I sem to recall. It's possible that its changed. However if your vehicle is earlier than Aug 95 then it should be tested under the less stringent version.
Not sure if you leave it at the MOT centre or arrive with it 1 min before having spent the previous 1/2 an hour blasting it around to get the oil temp up. The letter is better as I doubt they can get the oil temp up from cold to do the test from cold.
Is it actually failing the idle test (high CO) or is it when they hold it at half engine speed?

I took her for a long drive to clean out the pipes before Saturdays MOT, oil temp was about 80'c

At natural idle the CO dropped to 0.78% (a pass is 0.3-0.5)

On the fast idle test (2.5-3krpm) it failed miserably at 7.2% CO

Mine is a 1996 car