SNAIL

Harley · Posted: Tue Nov 11, 2008 12:55 pm Post subject: Strange loss of power...

Megasquirt EFI 602cc 2cv, 123 ignition, Accel super coil.

I had my car on the dyno yesterday, 25hp first run, then after tuning 27.5hp at the wheels, timing was retarded 2 degrees (light comes on after the hole). It was running very smooth and much more responsive. I took it for a test drive and had no power at WOT...
Tuning guy thought i was mad, we put it back on the dyno and sure enough 19HP... Played around with it for 2+ hours with no improvement, timing set back to original, old fuel map used etc. 27.5hp run and 19hp run had very similar AFR right across the rev range, so i don't believe it is fuel supply problem... now without fan it gains 4hp before it only gained 1-2hp

Next morning i torqued the head bolts (no adjustment required) and set the tappets (maybe a bit open but definitely not tight)
Replaced 123 ignition with original points (no difference)
Spark plugs look perfect, gap is good.
Compression test good, 138psi & 146psi...

On the highway engine is running a lot hotter, oil +20c (100-110 normally 80), Cylinder head 50f+ (400f normally 300-350).

Possibilities,
MAP never gets above 90kpa, should it go to 100kpa at WOT??? or does that depend on altitude...
Fuel filter blocked???
My oil pressure gauge is not working???

Before the dyno detuning i could sit on 110km/h comfortably, i did 126km/h on a flat stretch one cool morning Very Happy

Now lucky to do 100km/h and not over heat Crying or Very sad

Harley
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Check out my Dinosaur www.youtube.com/watch?v=RPF_uU61als
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Olli · Posted: Tue Nov 11, 2008 12:57 pm Post subject:

Tuning well done, you didnt lose more than 1/3 of power Wink

Sorry..
Hope you find hidden horses!

-Olli
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Harley · Posted: Tue Nov 11, 2008 1:07 pm Post subject:

Etienne · Hoodrider Joined: 25 May 2007 Posts: 2829

I cant' help you but it remind me a problem I got few years ago.

My 2cv lost his power as your did. For few weeks I couldn't drive more than 90 or 100 km/h. I was ready to change the engine, when suddenly it started to work again fine 120 km/h... Then I drove 50 000 km more with that engine with no problem...
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Jasu · Dropped Joined: 30 Sep 2007 Posts: 211 Location: Finland

Some what came in to my mind..:

-fuel pressure (fuel pump)
-lambda -sensor
-engine breather

These can make power loss, we had great battle with fuel pressure with my friends H-D Sportster...
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4x4 SuperFinn · Snailer Joined: 18 Jul 2008 Posts: 47 Location: UK

Probably an obvious one but did you refuel the car at all during the tests. You could have got some bad fuel.

I've had it before ( a few years ago) that a 2CV would not attain normal road speed but after running the tank down and fulling from anther petrol station all was well again...

Harley · Posted: Wed Nov 12, 2008 8:02 am Post subject:

i agree all things seem to be pointing at fuel....
I bet (hope) the fuel filter is blocked!

I am not currently using a Lambda sensor, so that rules that out.
I am using the new Ecas reed valve breather, i will test it again...
I did refuel after the dyno loss, no change. I then made a 1hr trip on a country road keeping revs and speed down to stop it from overheating.

I am now 800kms away from my 2cv, but I got to drive my DS Cool

BEST DYNO RESULTS EVER ! Twisted Evil

Harley
_________________
Check out my Dinosaur www.youtube.com/watch?v=RPF_uU61als
Spot my 2cv Surprised

www.youtube.com/watch?v=Zoq68CPLq4M

JuanNavarro · Posted: Wed Nov 12, 2008 12:32 pm Post subject:

Unplug the exc from alternator, maybe is a electric (regulator) problem, and do some short distance test looking for power gain (trying not to starve the accumulator).

Harley · Posted: Thu Nov 13, 2008 6:35 am Post subject:

It takes an expert to tune a 2cv and gain power. But it takes a genius to loss 8hp! Evil or Very Mad

Harley
_________________
Check out my Dinosaur www.youtube.com/watch?v=RPF_uU61als
Spot my 2cv Surprised

www.youtube.com/watch?v=Zoq68CPLq4M

Joolz · Posted: Thu Nov 13, 2008 8:11 pm Post subject:

Hi,
this is probably no help but a couple of ideas just in case, it sounds like the timing is out but you tried refitting the points and I guess you set them with a strobe gun(timing light)? so the timing must be right unless your flywheel's moved, and that's unlikely.
Only real ideas are maybe a blocked exhaust, or maybe a bearing has picked up and it's loosing the power and making the heat. Does the engine feel right if you turn it over with the starting handle? I've no experience of any of this, it's just random guessing.
Hope you fix it soon so you can tell us what it was.
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More is always more

Harley · Posted: Wed Jan 28, 2009 8:55 am Post subject:

The Saga continues..

The problem: no real top end power, overheating at WOT. engine feels great around town below 4500rpm...

What i have done/checked;
* converted back to Carby, using 5psi pressure reg running off the efi fuel system
* replaced Coil, leads & plugs
* reverted back to points ignition, tried two different 123 ignitions
* replaced rear exhaust system; swan neck, rear silencer, tail pipe
* checked fuel pressure
* adjusted tappets
* engine feels fine to turn over by hand

So, it is not fuel delivery as efi and carby act the same...
It is not my ignition unit and timing was set to standard an all three systems with the same results...How else could the timing change???

Perhaps the exhaust crossbox is restricted... Has anyone cut out the baffles of the cross box with decent results?

I will try disconnecting the altinator as well...

Harley
_________________
Check out my Dinosaur www.youtube.com/watch?v=RPF_uU61als
Spot my 2cv Surprised

www.youtube.com/watch?v=Zoq68CPLq4M

backfire · Posted: Wed Jan 28, 2009 12:07 pm Post subject:

maybe front brakes are stuck, that will give you enough heat and powerloss.

If nothing else works, I personnaly would take apart the engine and do a complete checkup.
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2CV, with Visa turbo charged

Bart · Posted: Wed Jan 28, 2009 12:25 pm Post subject:

Brakes are a good point.

I have emptied crossboxes and it aids a bit on power, but unless you crossbox is blocked up it wouldn't solve the problem.

Just a thought: does the fuel pump deliver enough fuel at higher revs? as that is about the only thing you haven't checked (or at least mentioned here)
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dyanut · Posted: Wed Jan 28, 2009 4:34 pm Post subject:

Harley,
have you checked the lift of each valve?
One of the race engines I used to build came back from a weekend's racing with similar symptoms to what you describe.
The driver was known to avoid using 4th gear (except as a last resort) and also taking very little notice of the rev counter and although the car had qualified on the front row of the grid, by the end of the second race it was well down on power.
It transpired that a camshaft lobe for one of the exhaust valves had worn _very_ quickly, with the same driver's habit of revving the nuts off an engine from stone cold probably connected.
(I'm not suggesting that you might have abused your engine, btw.
But nothing else was wrong with that race engine, compression was excellent, timing spot on, carb OK which made it a bit of a puzzle until I turned the engine over using the handle whilst keeping an eye on the movement of the rockers. Sad

)

Ken

Harley · Posted: Wed Jan 28, 2009 6:21 pm Post subject:

@Backfire, brakes are ok, drums on front. I think teardown may be the only option. But i do have a set of visa pistons i would like to try!

@Bart, I just tried an old crossbox no difference Crying or Very sad

i have a WB contoller giving me AFR13.6 at wot, so a little confusing that it would overheat running a little rich like that. correct i have not tried a different fuel pump, i'll give it a go.

@dyanut, thanks for the tip, i will check tomorrow.

Harley
_________________
Check out my Dinosaur www.youtube.com/watch?v=RPF_uU61als
Spot my 2cv Surprised

www.youtube.com/watch?v=Zoq68CPLq4M