Over fuelling

[daveb500]

(I've copied this question from my other thread because it was getting a bit lost with all the other questions.)

I've done an engine rebuild and it is currently over fuelling quite a bit (all plugs are sooty and there is black smoke under acceleration).

Just to confuse things, the rebuild included a few new shiny bits :
- ACT triple plenum
- Bosch AFM
- Bosch Fuel reg (supplied as part of the kit to increase pressure slightly).
- Stealth cam
- Tornado Chip
- New injectors. They are Ford Yellow top and are supposed to be a direct replacement for the Lucus items but with a better splay pattern.

(The plenum, AFM, fuel reg and chip came as a package so should all work together ok).

So, first off, I want to get the fuelling checked. I assume the easiest way is to get a CO reading but what should it be on a Griff 500 with no cats?

then, assuming it is not good, I'm thinking of checking in the following order :
1. check the AFM set-up/operation and the base idle/throttle pot set-up.
2. check for air leaks.
3. not sure where to go after that. Possibly put the Lucus injectors back in? I'm slightly suspicious of the new ones as they don't seem be a very common replacement on TVR's (more on Range Rovers).
4. poss put the old pressure reg back in ?

Any other thoughts or advice? I plan to get an rr session but want to get it basically right first.

Edited by daveb500 on Tuesday 15th June 10:46

[griffdude]

IMHO because you have changed so many components in 1 go it'll be a bit tricky to establish a baseline to work from. I'd just make sure that no leaks & everythings mechanically tip-top, then get to a RR ASAP.

[steve-V8s]

Not at all surprised the fuelling is not right if you have made all those changes and are still effectively running on a standard map. With that level of modification you will either need to get the car and someone that can re map the ECU for you to a rolling road or go one mod further and fit a more modern ECU (assuming you still have the Lucas unit). You will still need to get it on a RR and have someone map it for you but the end cost may be less and the result may be better. Also you will be better able to accommodate any additional changes. You could also take off the AFM and sell it to help with the cost as a proper ECU will use the throttle pot, whilst doing that you may as well ditch the distributor and fit coil packs as well.

If you want to sort it without a re-map then I would say put back the standard pressure regulator, injectors and AFM and see where you are.

If you want to measure the fuelling get a wide band lambda sensor in the exhaust and connect it to a control unit and display. The theoretical ideal AFR is around 14.7:1 however this is not ideal for all engines and certainly not under load or acceleration when running it that lean will have the pistons holed in no time, running it too rich will potentially wash the oil off the bores and not make best power.

[daveb500]

steve-V8s said:

Not at all surprised the fuelling is not right if you have made all those changes and are still effectively running on a standard map. With that level of modification you will either need to get the car and someone that can re map the ECU for you to a rolling road or go one mod further and fit a more modern ECU (assuming you still have the Lucas unit). You will still need to get it on a RR and have someone map it for you but the end cost may be less and the result may be better. Also you will be better able to accommodate any additional changes. You could also take off the AFM and sell it to help with the cost as a proper ECU will use the throttle pot, whilst doing that you may as well ditch the distributor and fit coil packs as well.

If you want to sort it without a re-map then I would say put back the standard pressure regulator, injectors and AFM and see where you are.

If you want to measure the fuelling get a wide band lambda sensor in the exhaust and connect it to a control unit and display. The theoretical ideal AFR is around 14.7:1 however this is not ideal for all engines and certainly not under load or acceleration when running it that lean will have the pistons holed in no time, running it too rich will potentially wash the oil off the bores and not make best power.

It has been remapped based on me telling ACT / Mark Adams what has changed. As I say, the majority of the changes came as a "kit" anyway. but obviously, this will only give a rough starting point.

I think my top 3 checks are the sensible ones. Make sure the adjustable things are right, make sure there are no air leaks and then, if necessary, put the standard injectors back in. The injectors are the biggest unknown really and Mark couldn't allow for these. And I can put them back in later if I have a rolling road session.

Edited by daveb500 on Tuesday 15th June 13:04

[lotusandy]

I would:-

Get it on a rolling road and ask them to give you a plot of the Air/Fuel ratio vs RPM at both full & part throttle, it is essential you do this before anything else to quantify just how much of a problem you have (if any!) and under what conditions it occurs.

Next easiest thing to consider is to adjust the fueling by adjusting the fuel pressure, but of course this will apply across the entire rev range..

Andy

[daveb500]

Quinny said:

To be honest Dave, you'll be pissing in the wind trying to get that lot sorted without a RR..

Just to many variables, to be able to nail it down to just one thing..

Yeh, I agree with you really, but I don't want to put it on a RR until I understand what is going on with the oil consumption. It's a bit of a catch 22 at the moment. I'm booked in for a RR session at the Growl so I'll have a fiddle for the next few weeks and then see where I'm at. At minimum, I can make sure there are no air leaks and I've done the throttle pot and AFM settings correctly.

[daveb500]

Quinny said:

I think the RR at the Growl is just a power run.... It'll probably be able to tell you you're running rich etc, but won't be able to do much about it...

Bit of a waste of money in my view...

To get it right you need to, be able to make the adjustments, run it again, adjust, run etc etc..

Personally I wouldn't be the slightest bit concerned about the oil consumption, until I knew the fueling was right...


If the oil consumption is high, you can always keep sticking oil in, but if the fueling is all over the place, it could lead to other problrms..

Just my 2p's worth

Actually, I do believe that makes some sense

[steve-V8s]

Don’t think I would be happy with a power run without some confidence that the fuel is somewhere right over the entire map. It could potentially be rich low down and become melted piston lean at the top end.

[blitzracing]

You have a bit of a problem here, the ECU can trim the mixture by around +/- 20 % to start with. This happens at idle, and then from this point upwards the ECU will try and keep it near the correct with much smaller corrections from the lambda feedback. The issue here is you have no idea how much the ECU has already trimmed the mixture to start with, so you dont know what your mixture starting point is, as ideally you want the minimum correction. Tail pipe tests only show if the ECU is managing to keep it somewhere near correct (or otherwise), but it could be running at 20% correction already. This information (the long term fuel trim) is available from the 14CUX via a serial port, but its so proprietry, very few can read it. This applies up to 3400 rpm, when the ECU then goes open loop, so readings above this are uncorrected. If you ran a non catalyst fuel map, you would have no extra correction taking place (other than basic CO trim) so you could then say how far out the base map is as the tail pipe shows rich or lean. If you are running a Tornado I THINK both cat and non cat map are set for the same engine set up, (but please check with Mark A) so this could give some viable data to find out how far out the mapping is, but to be honest I think you are on a loosing streak with both Mark A and some rollers at the same time.