Decat & Remap ??

[BilboTVR]

Mornin Guys ,

Managed to fully decat at the weekend with the ACT parts. Ran it through the MOT emissions tester for giggles to see just how bad it was . Obviously it failed miserably on all fronts as expected (which is half the fun I suppose),but it's got me wondering if there's a simple fix to get it running slightly better / efficiently as the differences were dramatic.

Is there a chip out there I can just slot in that would help or something similar ? Ie not having to fully remap / change everything about , just a bit of a make do for now type thing. If not then i guess I'll just have to live with all the new grunts and gurgles

Everything else on the car is standard as far as i know (R reg 500).

Thanks in advance Guys.

Dave.

[Sardonicus]

Print up the results 1st so we can have a looksie it should have only failed on CO & Lambda and not by miles

[BilboTVR]

Stupidly I didn't take the "after" results with me . I'll pop back and do it again this week so you can all have a ponder/ laugh.

[blitzracing]

If you have simply removed the cats, but not changed the tune resistor- the ECU should already be doing its best to keep the emmissions as low as it can automatically. If the Lambda probes are working as should be and the engine is running well you wont be able to improve things. The whole closed loop thing is set to burn the fuel with minimum polutants, with or without catalysts. If you switch to the non catalyst tune by changing the resistor under the dash, you can alter the mixture up to about 2400 rpm with the adjustment on the side of the AFM, so you could try this if you want just to experiment at idle. The Non cat fuel map is unlikely to be mapped for a TVR- more likely the origional Range Rover map, so not really suitible for best power on a permanent basis. The Mark Adams chips will work in both modes for the given engine spec, and Ive run both, and the only difference is a fraction less shunting on the non cat map.

[Alun450]

Blitzracing,I've just gone de cat, original Tvr Y and fitted non cat resistor. Everything appears to be working very well, I've not tried fine tuning the lower rev range yet. Thanks to your information, can you elaborate!! I've barely driven it yet, but before de cat it often seemed to slightly over fuel, cold and hot, not much but it's there. I had a 20 minute hoon yesterday, and the car felt great, faster and still behaves perfect. Temp gauge was lower for alot longer than before, engines spinning and roaring lovely. It's just that low speed/ rev range that's a bit gassy!!!
Do I need ecu reader etc!
Your posts are so clear, bloody great.

[blitzracing]

The basic " factory" setting of mixture can be done by measuring a DC voltage across a couple of pins on the AFM connector, and simply winding the adjustment screw on the side of the AFM until its correct. Alternatively simply let the car idle when warm, and turn the screw clockwise (weaker mixture) until the engine starts to falter as it becomes too lean, then wind it back until you have a smooth idle and leave it at that. If you wind it the otherway, the engine should start to choke as it overfuels. Apparently the direction of the AFM screw is not always the same for rich / lean so you may have to screw it anticlockwise to get it leaner- but you can tell one way or the other by the exhaust smell as it overfuels if you are going the wrong way.

The DC voltages on the AFM wires are:

Red/black. Ground

Blue/red CO trim value. This is factory set 1.8 volts for catalyst engines, although I believe this setting is ignored with Lambda correction. Non cat cars are in the range of 1-1.5 volts.


As for the non cat map in the TVR chip- its never been proved one way or the other if this has been modified from the stock Range Rover map. If it is a Range Rover map its quite likely to run lean at full throttle, as the map is scaled for 160-200 BHP at 5400 rpm, much less airflow or RPM than the TVR, but it would be nice to have some confirmation of a rolling road test to be sure. If you are handy with a test meter you could just measure the lambda outputs at full load and make sure they dont drop below 1.2 volts as this would indicate a lean condition. (These will still give relevent voltages even when the non cat map is selected).

RoverGauge and ECU mate are no use for full power lambda tests as the Lambdas are ignored in both non cat mode or open loop above 3400 rpm, so the ECU does not show a correction value from its OBD port. You just need a test meter to read the physical voltages.

I need to have a look at a TVR chip with RoverGauge, as it shows the load values for the maps, so I could compare cat against non cat and see what the differences are in basic fuelling.

[BilboTVR]

Cheers Blitz , Aluns right... nice and concise info.

I'll try sticking in one of the green "non cat" resistors and see what happens . If it makes it worse due to the "non cat map" being untuned / wrongly tuned as you think it could be ,I suppose all I have to do is switch it back and take it from there. Hoping that the Lambdas didn't take a bash during the change.

I'll still get myself down to the machine though just for curiosity's sake.

Thanks again,

Dave.

[swanny71]

Is there any real need to mess about with the resistors when de-catting? I did it on my old Griff without changing a resistor with no ill effects and I'm about to do it on the Chim and don't intend to this time - unless I really have to.
Cheers

[Sardonicus]

swanny71 said:

Is there any real need to mess about with the resistors when de-catting? I did it on my old Griff without changing a resistor with no ill effects and I'm about to do it on the Chim and don't intend to this time - unless I really have to.
Cheers

Your right Mark/Blitz will tell you than the Lambda scaling is quite forgiving (closed loop) making changes like this and they tend to run slightly rich on full throttle (open loop) so you have no worries of the car leaning out due to cat removal for example you have a slight buffer well on the smaller engine cars cant comment on the 5.0 but this is all running the Cat-Map obviously

Edited by Sardonicus on Tuesday 21st May 13:09

[blitzracing]

Just a thought about the cat / non cat map or specific engines- there is something called the "adjustment factor" applied to the maps, that is directly attributed to engine displacement. I think this is constant across all the maps, so all maps may be simply be re-scaled with one adjustment, but I need to have a closer look.......

[swanny71]

Sardonicus said:

our right Mark/Blitz will tell you than the Lambda scaling is quite forgiving (closed loop) making changes like this and they tend to run slightly rich on full throttle (open loop) so you have no worries of the car leaning out due to cat removal for example you have a slight buffer well on the smaller engine cars cant comment on the 5.0 but this is all running the Cat-Map obviously

Edited by Sardonicus on Tuesday 21st May 13:09

Thanks Simon (& Blitz)
I'm actually fitting the ACT manifolds and de-cat pipes (with the option to bolt in 200 cell cats) and was a little concerned about running lean. If you remember mine was the Taraka Chim at the Surrey Rolling Road day when it ran slightly lean at the top end.

[Sardonicus]

swanny71 said:

Thanks Simon (& Blitz)
I'm actually fitting the ACT manifolds and de-cat pipes (with the option to bolt in 200 cell cats) and was a little concerned about running lean. If you remember mine was the Taraka Chim at the Surrey Rolling Road day when it ran slightly lean at the top end.

Hi Swanny remember it well nice HP and a nice torque curve only one way you will find out I am afraid don't be too surprised if it makes the fueling worse though

[BilboTVR]

Ok , Here we go Sardonicus results before and after as promised :

Before :
Revs :2,600
Co2 :0.06
HC :55
Lambda :1.004

After:
Revs :2,600
Co2 :0.9
Hc :805
Lambda :1.075

I guess that means the Lambdas are working at least.(although I sadly did not test them with a meter - Sorry) We also thought we were possibly hearing a slight missfire (not that that is going to help any of you not there to hear it with your own ears!

Dave.

[Alun450]

Fantastic you mean I can tune my idle like I did in my old motor bike days,by ear, your full of joyful surprises Blitz.
Now I have a re fresh Powers engine, and Dom went to his secrets box and changed the chip, def not Landie, rev counter reads wrong, revs freely to limiter 6250, if you ever wanted to use my car for tests, with the knowledge your sharing with us I'd gladly bring her to you.

It's time I bought a meter. Seems all logical to me. I'm sure on full chat in 5th 140mph+ my cars lean, if you raise the throttle a little at those speeds it accelerates!

I'm going to have to do same speed test now I've got clear airways, think the exhaust was stopping me.
Late car with all cats and suffocating.

So the green wired resistor may also run lean at the top end, what can I do about that again please, sorry I'm thick, once it's in there it's there for life though!!!

Cricky the car I started with 18 months ago is along way from the raging bull she sounds and goes like now.

[Alun450]

Go back to original resistor, is that the only way to adjust top end fuelling!