DDK - Die Deutschen Klassiker

took the car down to Bob Watson's yesterday just to see how much power it was making and also for any corrective tuning by the maestro himself.

Please see below a homemade copy of the final printout , done with greaseproof paper tracing on the kitchen table !

Can anyone here explain why the torque curve wobbles like Dolly Parton , the books on engine theory all seem to draw smooth idealised curves !

Cheers

mine is identical following a similar pattern...

I'l post up a photo of my trace later

Ha, I thought mine was bad...

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To be honest, with a graph like yours I`d be on the phone to Bob asking his opinion.

My graph above was done last year and I`ve spent considerable time (and money) trying to rectify problems that may have a bearing on the dip in the torque curve.

I had my carburetors rebuilt, I had a crack in one of the manifolds welded up and both of them skimmed. I had one distributor rebuilt many times all to no avail, then I had another distributor rebuit andrecurved. I tried pertronix, then went back to points, oh and put some new plugs in.

I`m planning to go down to Bobs and see if any of this has had an effect, the car certainly seems to drive better.

So in short your problems maybe with how your distributor is working/advancing. Is there any scarring inside the dizzy cap caused by shaft wobble. Do the weights move easily or are they catching?

Or maybe your engine is sucking in air where it shouldn`t be, you don`t say whether your car has carbs or is injected... If you are on carbs, are the shafts loose and letting air in? Spray the shaft ends with brake cleaner whilst the engine is running... does it get sucked in ? Cracks in the manifolds can happen if the manifolds have been tightened down too much but you`ll have to whip them off and scrutise them closely. When you`ve got them off, lay the mating surfaces on a piece of plate glass to check they`re nor warped... same with the carbs.

One other thing I can think about is how clean is your fuel supply ? Reving the tits off an engine sucks any silty rubbish you might have lurking in your fuel tank straight into you fuel system and a filter can only do so much.

If you`re injected, then maybe someone else can help.

Regards, Mike.

Mike, mine has fully rebuilt MFI, pump & throttles, fully rebuilt dizzy, new Ignition system incl CDI box etc etc

My car has been on the rollers a few times now

Each time the torque curve has the same characteristic ..... which is at the exact point where my car starts coming on cam

I'd love to see any other 'S' cars plots & see if they have the same, as so far my 2.4S, oldtimers 2.4S & your S do.

At the moment, mine is pulling really well ( bizarrely even better since my CLM incident )

good thread guys ,i have somewhat similar curve (from Bobs as well) that i will add here later. Like you i was a bit puzzled by what was going on although the engine seemspretty healthy (3ltr/mfi/DC 80).Perhaps we can prevailon bob to give us some clarification.
Mike

Mmm, there`s a common denominator emerging here.

Mike.

My torque curve was pretty linear on my 2.4E with carbs at bobs. I don't have a pic of the chart on me though to post.

My power delivery is very linear with no 'coming on cam' effect.

Is it just you guys with S cams?

James

From what I understand, the way that the combustion occurs within the combustion chamber is not uniform across the rev range. The flame format being affected by assorts of selects like pressure front and back pressure that have distinct frequency components, and hence appear at specific rev ranges.
When programming the map on a megasquirt, the tuning table I use is the VE table, standing for volumetric efficiency. This is designed to make micro adjustments to ensuring the fuelling takes into account these non-uniformities in the combustion profile.
In fact, when starting out mapping, a good start map can be calculate from looking at the torque curve and specifically the vertices on the curve and entering then into a clever bit of code.
As your cars have fundamentally the same size and shape combustion chamber, the wobbly torque curves are similar. In fact it would be interesting to see a torque curve from a twin spark for comparison. This will influence the flame front the most, and hence the volumetric efficiency.
This is very theoretical stuff that I have picked up reading the Megasquirt forums. I am no expert, and I could be way off base, and I am happy to be told a more correct version of the truth but I think it seems to fit.
Tim

Hello chaps.

Great stuff.

I'd like to see an E cam curve and a Solex cam curve if anyone has one?

Its the cam IMHO more than anything: the E cam is undoubtedly the easiest and best to drive, subjectively, with what feels like a broad flat torque plateau.

Kind regards
David

Hi folks,

Here's an E cam curve, from a 2.4 E cammed engine on Webers that you may remember, David...........



and also the curve from our 3.2 MFI engined hillclimb car on RSR cams



Cheers!

JW

I`m not covinced it`s the cam, here`s the trace for my car two and a half months before the trace I posted above.



Not perfect but not bad. What happened between the two ?? That`s what I spent so much time trying to fathom. After all the factory torque curve is lovely and smooth.

Mike.

Here's my 2.4S (recently done on Bob's rolling road).
Same 'wobbly' curve.
Car runs lovely, no complaints from me.
Appears to be a consistent anomaly for these cars.
I'm not lying awake worrying about it.

Looking back through old threads, this is John Ms trace from his 2.2.E Looks very similar to Oldtimers trace at the top of the page, which makes me wonder what`s going on. Why are all these torque traces so similar and so wobbly when the factory manual always shows a smooth torque delivery despite the engine type.



Mike.

Ferry Man wrote:Here's my 2.4S (recently done on Bob's rolling road).
Same 'wobbly' curve.
Car runs lovely, no complaints from me.
Appears to be a consistent anomaly for these cars.
I'm not lying awake worrying about it.

I'm with Paul here .... my car is pulling well at the moment & you know how pinikity I get over how my car runs.

The Porsche documented curves will be very simplified I'm sure, and from a dyno, not wobbly rollers

One of you needs to get your engine on Neil Bainbridge's engine dyno and find out for sure.