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[philhoward]

Afternoon, all!  Been a while since I've been on here, but in the meantime I've managed to get my Ex-Plod X30XE installation into my Reliant Scimitar almost finished and has been road legal since August (just some niggles to sort out).

I know there's a lot of folklore around regarding ex-Police cars and whether or not they really were standard but after a quick run on the rollers (just after I'd got it on the road - wanted to check the fuel pump was up to scratch, honest ) I have a question regarding what looks to be rich running.  At WOT (as befits a dyno run), the mixture just gets richer and richer - worryingly so.

Second plot shows torque and AFR - I think the hiccup is a sticky ram valve..

Exhausts are a pair of Calibra 3-1 manifolds to 2" downpipes and into twin 1.75" systems (no cats) - first box being an offset silencer, 2nd box on each side straight through.; air filtration is by an eBay cheap K&N cone copy if they have any bearing on matters (although if a restriction, I'd expect the torque/bhp to tail off rather than be a gradual richening?





Comments welcome..

[zirk]

Are you running with the iPlods ECU?, if so, how have you set up (if any) Lambda sensors without the Cats?

[philhoward]

Stock Motronic ECU that came with the engine (so also ex-Plod).  Lambda sensors (only 1 per bank - short nose manifold engine from a pre-FL; about 1995 vintage, I think) fitted in the downpipes although I didn't think they were active at WOT?

[Marks DTM Calib]

Nope Lambda control is not functional at WOT.

Can you get the lid off the ECU see we can see what chip is fitted?

[philhoward]

Nope Lambda control is not functional at WOT.

Can you get the lid off the ECU see we can see what chip is fitted?

Not immediately but should be able to when I get home at the weekend.

Has anyone ever had a dyno plot on a "stock" engine with the AFR plotted?  Had no luck googling away..

[philhoward]

Aside from the lack of cats, I currently don't have a speedo signal going to the ECU - but I was under the impression that only affected the overrun shut-off of fuel?

[P6UL K]

Mines ex-plod, not sure if my RR print outs will be of any use...?

[philhoward]

Looks like yours is running even richer than mine???

[P6UL K]

Is it? I know one of the coilpacks is playing up so that could be the cause?

[jtypecav]

Try a 2.5 cavalier ecu on it. I had a similar issue (no, exact) until I swapped it out. The cavvy one learnt the 3.0 just fine. She's always been about 235-255 across any dyno it's seen. Thats with custom manifolds, 4bar reg and a few other tweaks mind. Could be the routing to the filter though - as I'd made two inlets and the first (I call it the twin toilet roll) used to put the EML on, the second (guttering) size inlet it was all good.

[philhoward]

P6ULK - assuming I'm looking at your plots correctly, yours is hovering about 10.5:1 which is seriously rich.  A quick google last night gave rough figures (very engine dependant) that peak power on a N/A engine is in the 12.5/13:1 region

jtypecav - does it plug straight onto the existing loom?  C25XE or X25XE (Calibra, I assume) ECU - I guess a pre-immobiliser one?  What else did you do to yours to get those horses???  I know of a guy who's also done the X30XE into a Scimitar who did a little bit of polishing and porting, opened out the throttle body a couple of mm, some very long primary exhausts (27" or so) and a CANEMS ECU and hit 265bhp on an otherwise stock engine.

I'm using all of the original trunking before the filter although it might be a little bit shrouded (in a void in the bodywork) it is still the original drainpipe system - to keep it as standard as possible!

[philhoward]

jypecav - I assume you're the same guy now lurking on Brisky??

[Kevin Wood]

Yep, I'd expect power to be best around 12.5:1 so the OP's plot doesn't look too bad to me, given that an OEM map will always err on the side of caution.

It's heading a little richer above 6000 RPM but remember that the power has peaked by then, so it's probably just holding the same fuelling and the VE is reducing.

Given that, as said, it will be running open-loop, that's about as good as I'd expect. If you want to optimise it further, fit a programmable aftermarket ECU like a Megasquirt, Emerald, etc. No point messing about swapping factory ECUs IMHO.

.. and 10.5:1 is stinky rich. It'll be down on power a bit if it's running that rich.

It does also call into question how the AFR measurement was made, of course. Just because there's a number there it doesn't mean it's accurate. Best course of action is to tweak the map for best power, which is where a mappable ECU comes into its' own.

[philhoward]

As I was there at the time (and have known the guys at North London Dyno for a while) I know they use a stock wideband sensor (LSU1 IIRC) up the exhaust pipe for AFR measurement.  From other runs on the same day (until their sensor died later on in the day - they do get through a few apparently), the AFR figures are likely to be correct.

It was only a power run rather than a full session and as I mentioned earlier, I wanted it purely to see if the fuel pump (not an Omega one for other reasons) was up to the task at full bore - to which the answer is yes.

I could have Megasquirted (or similar) the engine, but wanted the all-season manners of the original setup as much as possible which was the idea behind doing the conversion in the first place.

I've noticed that my torque drops off a bit steeper than P6ULK's - but I'm guessing comparing an early 3.0 with (I assume) a 3.2 isn't exactly comparing like for like - either that or I am suffering with an increasing restriction at the top end (which could well be exhausts).  Not been able to find a plot from a standard 3.0 yet although they don't seem to have the tail-off over 5000rpm that mine does..