Mbe check over and latest emissions test

Mbe check over and latest emissions test

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Incognegro

1,560 posts

132 months

Sunday 25th June 2017
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ClassicChimaera said:
Incognegro said:
I have no idea what those difference mean/equate to in use of the car but just thought I'd chip in with... my cerbera is going into Dom on Saturday for a knock MBE and some other tricks. I'll be using a Bluetooth OBDII reader as you suggest Matt which will be running realtime info on my android screen and the torque pro app (which I've been testing on my Range Rover and the info you get is great and easily customisable)

The best bit is the data logging feature so I'll let you know true 0-60s wink
Please come back and tell us how you get on.
I've seen all this today, sweets for blokes smile
Thought I'd do as you asked Classic... My standard RR update never went ahead as shortly after dropping off to Dom all those months ago my engine was in a sorry state! I quickly decided to authorise him for his 4.5 Super Sports rebuild with MBE and all the trimmings. 6 months later I could be picking up next week.




Classic Chim

Original Poster:

12,424 posts

148 months

Sunday 25th June 2017
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I've been keeping abreast of what's been going on so I am aware smile
I had this awesome feeling in my gut which consisted of trepidation fear of the unknown and huge hope and anticipation of better days ahead when going Mbe. biggrin
Only today after over a week not using my Chim I fired her up and that usual confidence inspiring engine fires into life and breeds even more confidence every single time, I must have started it 2000 times since install yet I still find I'm enjoying it.
I'm very much looking forward to seeing the results over the coming months.
Congratulations and if you've run it in bring it to Shakespear Raceway (Stratford) on the weekend 22/23 July as I'm sure we'd all love to see it and you'll be in illustrious company with some very fast Chims etc there. smile
Thanks for getting back to us thumbup
Looks sooo awesome, I bet your busting at the seams Al hehe



ChimpOnGas

9,637 posts

178 months

Monday 26th June 2017
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Sardonicus said:
ClassicChimaera said:
I often wonder how it ticks over from stone cold without a stepper, I think I'm starting to understand smile
Decent AFR and lots of advance Alun wink nowt to do with running MAP smile
In my humble opinion the less interference from the idle air control valve the better Alun, its just a managed vacuum leak and all vacuum leaks are bad for engine behavior. By all accounts Dom's MBE installations do away the idle air control valve entirely, so I suspect he's using 'scatter spark' to manage idle speed. I did speak with a guy a few weeks ago with a Griff that had a Powers MBE installation and he was complaining of low idle speed on warm-up and having to keep the engine alive with his foot during this period, but I'm sure this could be corrected easily.

My Canems system uses the Bosch rotary idle air control valve which is much better than a stepper motor, but it's still bleeding air into the engine so it's still a managed vacuum leak, I strongly believe 'Less Is More' with idle valves.

I spent a lot of time setting up my idle speed and quality with the idle valve completely removed from the equation and just using ignition timing and throttle butterfly position. I've ended up with 28 degrees of advance at idle on LPG, my base idle screw is screwed all the way home because as far as I'm concerned it's just another managed vacuum leak, any additional idle speed I then needed beyond what I was getting from the 28 degrees of timing was achieved by adjusting the throttle butterfly rest position.

I also fitted a PCV valve in the pipe that links the plenum to atmosphere at the throttle body, this open to atmosphere circuit is just another vacuum leak and a pretty bad one at that. With all the above complete, then and only then did I bring my idle air control valve back into the equation, the thinking being if I can achieve the perfect idle using just ignition timing and throttle butterfly position then the idle valve has a lot less to do which is a good thing because as I've already said an idle air control valve is just a managed vacuum leak. I was always taught all vacuum leaks (managed or un-managed) are bad news for engine behaviour, the ideal scenario being 100% of the air entering the engine should pass the throttle butterfly because this is the device you use to regulate engine speed using your foot.

The results of the above work can be clearly seen when observing the duty cycle of my idle air control valve, better still throttle response is greatly improved especially as you pull away from a junction or I'm maneuvering the car at slow speed (reverse parking ect). This is because the additional timing has created a big increase in torque at low engine speeds and my foot now controls the air going into the engine rather than any over enthusiastic behavior from the idle valve, there's also no air being drawn down that open to atmosphere hose on the passive engine breathing system designed by Land Rover.

My idle air control valve is still in place and I wouldn't be without it, it adds 500-1000rpm on warm up and is configured to run closed loop whereby it helps to maintain my 1050rpm target idle speed and bridges gear changes beautifully with a set decay rate, these features and the anti-stall function it provides are why I've kept my idle valve but during normal driving and idle it really doesn't get involved at all and the car behaves immeasurable better for it.

Finally I run a richer 13.6:1 AFR at idle which works perfectly with 28 degrees of timing to deliver a super smooth 1050rpm idle, although I should also point out LPG helps here too because being a gas it mixes with air (another gas) much better at low air speeds (idle) than petrol, its slower burn rate also gives a longer duration of combustion pressure on the crown of the piston all of which helps to give a lovey smooth idle and better off throttle torque.

I can certainly see why Powers Performance do things the way they do, if you think about it regulating engine speed by bleeding air into the engine is far from ideal for a number of reasons and if you're trying to control that air using an old school stepper motor controlled by a very old tech and slow responding 14CUX you're really asking for trouble. Things get even worse as the 14CUX is running narrow band lambda feedback so it lets a bunch of air in to control the idle then realises it's made itself lean. It responds by chucking in a big dollop of fuel and you get a rich misfire, it then pulls fuel and it goes lean again and you end up po-going up the road 'The Shunt'.

If I had a 14CUX Chimaera I'd be very tempted to delete the stepper motor all together, I'd also switch from ported vacuum on the vac advance to a full vacuum source for an extra 8 degrees of timing at idle, I'd then screw my base idle screw all the way home and fit the PCV valve as described above. Finally I'd adjust my idle to 1100rpm just by virtue of throttle butterfly position and I bet the car would drive beautifully with zero shunting, and all this for no cost at all.

Forget all this ECU chip nonsense, delete the very restrictive cats, set the car up properly eliminating all vacuum leaks (managed & un-managed) and add some timing at idle, this is how to make these cars drive nicely wink

Classic Chim

Original Poster:

12,424 posts

148 months

Monday 26th June 2017
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Without an idle control valve and as Jason sets up the tickover at 800-900 revs I suppose it's likely on a cold morning idle will drop slightly.
Mine also displays this trait but it will still run on about 700 revs cold if I ask it, as I have my way of running up the engine I've always found by the time I'm ready to go and that's often only a couple of minutes at best it will idle fine even in very cold climbs so no problem. I don't like artificially raised revs and if it is raised I havn't got it warm enough to drive in my view anyway so it make no odds to me at all. The fact there's never tonnes of fuel getting chucked in makes me a lot happier about all starting conditions. If your friend has this problem then return it to Power! Even stone cold the extra advance should pull the engine through its rev cycle and mine lives outside and I've started it many times with -5 degrees conditions and it will never stall?
My idle dropped even with engine warm and that was put down to a badly adjusted idle screw. Very odd! Simple adjustment and slight change of some parameters later (5 mins work) and it's been excellent since.
I'm sorry but my car is not faster de catted Dave,,,,, not one mph faster!
Feels it but the times don't lie on a race strip. I don't like this fact so it's either my engines lost its edge or de cat doesn't work on mine,,, here's a telling fact,,, I mentioned de catting to Dom and he scoffed and just said you'll go back to Catt,, I hate the bloke,, he's always right wink
Maybe my induction is a bigger restriction and starving my engine power more than any exhaust will,,, feck knows but overall my cars no faster with a lovely de Catt Y at the top end.
I need a dyno session to be sure but it feels just as fast as ever on the road so it's an odd one.

I also have a suspicion Jason's mapping is conservative at those higher revs,,, engine life and reliability etc rather than pure power. Not a bad thing for about 95% of us.
It's always important to remember the pressure I applied, all along I said sod Bhp, give me torque and I have a very healthy torque curve for a boggo 4.6 engine. Beat Daz and Jacko off the line,,, once each I might add, got stuffed every other time by the 5.0 cars. thumbup



QBee

20,905 posts

143 months

Monday 26th June 2017
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I get your point about lpg idling, Dave - my old 2.9 T6 Volvo is on lpg, and runs like a bag of nails idling on petrol - as soon as the lpg cuts in at 50 degrees C it is as smooth as silk.

I am on Emerald on the TVR, and Jools adjusted the fuel maps to get the cold idle nice and sweet. It's now lovely and smooth.

I used to long for the old manual choke knob I had in my 1967 Mini.......but it doesn't suit married life, as my Mrs would only go and hang her handbag on it furious

Classic Chim

Original Poster:

12,424 posts

148 months

Monday 26th June 2017
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Good old choke knob
Does yours have an idle valve Anthony, seem to remember seeing a Bosch one scratchchin


QBee

20,905 posts

143 months

Monday 26th June 2017
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Classic Chim said:
Good old choke knob
Does yours have an idle valve Anthony, seem to remember seeing a Bosch one scratchchin
Not that I recall seeing - there's nothing in the elbow close to the plenum apart from the good old dump valve.
Where would it be located if not there?

I do have a variable bleed controller on the inside left position, close to the front of the exhaust manifold. It is managed by the ECU, and it controls the release pressure of the wastegate, as i understand it, thus allowing three maps to be stored at different boost pressures.
Frankly, I am amazed there isn't a button, a spout and a cup holder in front of the passenger with three settings - Espresso, Ristretto and Cappuccino. coffee

angus337

620 posts

208 months

Tuesday 27th June 2017
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I've had an idling problem for a while which after a lot of messing about I've temporarily fixed by disconnecting the stepper.

1st problem was that my stepper was wired incorrectly at the ecu. So the homing position was fully open instead of fully closed and it operated in reverse. the iac step curve was reversed to compensate, but I didn't think it worked correctly as it didn't get a consistent homing position. However After rewiring and redoing the iac curve, I only got a small improvement.

2nd issue was a small vacuum leak on the hose from the fuel pressure regulator. Replaced the hose and thought I'd finally solved the problem. Got a perfect idle from cold to fully warmed up. However, after an hours drive the revs started dropping to zero as I changed down at junctions. It appears that the stepper was closing as per the iac curve, but was sticking occasionally when requested to open, so over time it gradually drifted closed. Fixing the vacuum leak actually made the idle worse. Cleaned the stepper housing and Replaced the stepper motor but still had the same problem.

Eventually gave up and disconnected the dam thing! Now seems almost perfect, apart from having to give it a bit of throttle on cold start-up.

The other thing I've changed recently which really helped both the idle and low speed throttle response was to change from 4 squirts per engine cycle to 2 squirts. Unless the car is really cold, it will now start on the key with out any throttle, although a bit of gas does help to prevent it hunting. Not sure on the science behind this, but assuming 2 squirts reduces the sensitivity to injector dead time.

I'd still like to improve the cold start-up so I'll have a look at the idle advance next. Currently idles at about 14 so may be some scope in increase this.

Eventually I'll look at replacing the stepper with a bosch valve, but not sure what's involved, the mega squirt settings seem simple enough so just need to figure out how to wire it up.





Edited by angus337 on Tuesday 27th June 01:20