individual differneces between equal engines; what is that ?

[trond]

I never seemed to get the expected performance from my SC. I run MS2 with wideband lambda and I believe the are no issues with fuel mapping. About 12.6 AFR at WOT.

Ignition is dual EDIS and VR sensor also run by the MS ECU.

I now have dual ignition and a dual EDIS ignition, but no significant difference from when it was single spark EDIS, it is still a a dog

Performance is just not comparable to a friends stock 3.0 SC. His car is stock. Both of us have the same exhaust with SSIs and Dansk Sport muffler. My car is not at all rev happy like his. Every time I am in his car I wonder how can it be this is just a 3 liter with the rev happy pulling like a locomotive character, while in my car I always think how disappointing it feels. Engine note from exhaust is different too, with his the basso profundo from his car and mine sounding a bit strangled and tinny. And I have the 70 mm dansk sport

Both of run stock cams and same engine code (1980 US cars). His engine seems to be completely stock, based on invoices from previous owner

I have decided now I will get to the bottom of this;

As I can see it must be either my ignition is letting me down or cam timing. I set my cams at 1.55 mm, don’t know about his. He runs stock distributor and CDI, I have EDIS

Is it possible that my ignition is letting me down ? I have decided to do another cam timing and see if retarding the cams slightly to 1.1 mm might make the difference. If not I am lost


Any advice ?

[pampadori]

Got a picture of your ignition map?

[manbridge 74]

This is almost always due to compression especially if timing advance is the same. Be it static due to volumes or dynamic due to cam timing, it has a direct effect on engine output and even sound on the same spec cars.

[jpnovak]

Does your actual timing match the ECU map? Meaning a timing light shows the same as your ECU is telling the engine? Make sure it matches all the way up through RPM range. Sometimes crank sensor latency can retard timing when you do not want it to. Latency can be adjusted in the timing configuration page along with crank angle offsets.

[GH85Carrera]

Does the SC have the same throttle setup on the cable as a Carrera? It is common for the throttle to be mid adjusted. That means the throttle does not open all the way when you floor it. Look to see if the butterfly goes to wide open with the throttle floored. One of my friends had a throttle that only opened to about 80%. He thought I performed magic when we adjusted the linkage to go to true WOT.

[mepstein]

Have you done a leakdown on your engine?

[Hi_Fi_Guy]

Before running any test check for the obvious stuff like a loose spark plug wire, pinched or loose vacuum hose, bound linkage, etc. If you are convinced all the superficial components are OK then use this rule of thumb when diagnosing an engine:

• First test for compression. Compression test & leak down. Ensure the valves are properly adjusted.
• Second test timing. Ignition timing, spark plugs, wires, etc. Plus cam timing if you even suspect it is not correct.
• Last check the fuel system (carbs or FI) including linkage, and any areas that can be adjusted, wear, or fail. Be sure to test the fuel pump and if suspect test the fuel pressure/volume.

Diagnose in this order to ensure you eliminate possible problems than could be masked or falsely diagnosed as other systems. I can not count the number of owners I have met who spend weeks or months chasing "carburetor problems" only to discover their valves were not properly adjusted or their timing was off or something else amiss that they and everyone else were 100% positive was a fuel issue when it was not.

If you fix/replace components try to make changes to one system at a time if you can. Then drive the car and note any positive or negative changes before moving on to the next issue. You want to create a baseline and ensure each system is correct before moving to the next. In this way, when and if you do isolate your issue to a Fuel Injection issue you can tackle it with confidence that you will be able to find and fix the real problem.

One last thought, sometimes it may be only one issue effecting an engine and other times it may be a few little things that add up to poor running. If you go through the diagnostic process you can start to rule out certain things and this will make it much easier to find the true fault or faults.

[T77911S]

i can tell you that timing (at idle) can effect exhaust note.
I have played around with timing a lot on my 77s and even my 930. I could really tell a difference at idle in exhaust note when I would retard the timing.
the tone got deeper with more retard. (factory setting VS unplugging the vac retard).


I would look into timing, if you are nit getting the advance you need or even too much, you will loose response.
you should dyno tune the timing

[trond]

thanks for the good advice all. Much appreciated. Most of the advice I believe I think I have covered but I will make a point of running through all. Somewhere I must have made a wrong assumption or just a dumb mistake. Reason I asked if EDIS could be letting me down is that it is just about the only item that has remained more or less contant, with two rebuilds, several valve adjustments, new pistons and cam replacements testing different setups. I only checked with ignition strobe around idle to adjust trigger offset and will test that first. I verified full throttle. I tried +/-5 degrees and more but that was not it. Compression check next but engine character was similar before I changed pistons and cylinders from stock 9.3CR to 98mm/10.3CR. And then I will rewire power supply to ignition modules and coilpacks. Will report back when weather gets a bit more forgiving

[trond]

I will post a few MS settings. If anything looks strange please advice ? MS2 w/dual EDIS. VR sensor hooked up to EDIS modules

[trond]

ign advance is conservative. With current table it purrs. I have tried up to 10 more degrees at WOT rows and believe now it is slightly down on power possibly

[trond]

AFR table

[pampadori]

You twin plugged? The ign timing at wot seems quite conservative. 18 degree advance at wot up top is not enough.

[trond]

yes twin plugged. I am aware it is lowish but I rarely visit the WOT rows and was trying to lower to see if how it affected engine behaviour. The answer is not a lot, some loss of power obviously but not night and day. Not enough to explain my engines 'unwillingness'

[jpnovak]

I am concerned about your statement:

"MS2 w/dual EDIS. VR sensor hooked up to EDIS modules"

How is your twin plug connected? I just want to verify that the VR sensor does not go to both units.

I have always wired VR sensor to only one controller unit.

Should be...

VR sensor to ONE module.
EDIS PIP signal PIN 1 to MS Pin24 (ignition input)
SAW output signal from MS Pin 36 to EDIS Pin3 is split and sent to BOTH EDIS units.

And yes, your timing is VERY conservative. I can understand why you say the engine feels sluggish and lazy. Normally I would be in the 26-28 deg range at WOT and then upper 30s at light throttle and 40s in off-throttle overrun.

[trond]

wired like this. I was imprecise. And yes about 'slow' ignition but I tried with more advance and it does not fix the problem, only makes engine run with a harder note to it. More power but somehow I thought engine sounded slightly unhappy and backed off until it started purring. If you understand. It appears I need to look elsewhere, it is not the timing map (I tried everything there); how big a difference measured by seat of pants does it make to time cams later ?

[pampadori]

To give you an idea of how much power you might be leaving on the table, i gained about 50whp in some spots by increasing my initial tune's timing 10-15 degrees once I got it on a dyno. I ended up with 203whp on 92 octane (single plug)

[wreckah]

hi trond, it looks OK to me...trigger offset is 0 in my case, but we are probably using different crank pulleys. (mine is goingsuperfast)

i'm at 27° max ign timing (conservatively tuned on dyno) with single plug. (microsquirt EDIS)
I remember the operator saying that he did not find more power up top with more agressive timing.

the ignition curve seems to be quite similar to mine, minus ca. 10° overall.

IIRC my cams were also set at 1.5X

I also have SSI's, but stock steel 1974 banana. The car feels very torquey, very streetable, but not a high rpm powerhouse. My car is also somewhat lighter with fibreglass bumpers. Haven't driven other SC's to compare...

i guess it's never 'fast enough'

[wreckah]

FYI: also fully rebuilt here, EFI with microsquirt and EDIS.

dyno number says 187hp, and i think it is at the crank too...so comparatively very low numbers...no clue what other SC's would have done on that dyno.

i can only compare to my daily 1988 E30 325i with 170hp, and the porsche feels MUCH faster...

[trond]

seems we are in the same area of the ballpark then, dual spark accounts for some 8-10 degrees less so not far different. Not enough to explain my perceived poor performance which is also manifest in the way it behaves at lower loadings (included with more advance). Some of it but not the main bulk of it. Somehow it reminds me of the old DUcati I had. I thought it was fine until I swapped one of the two ignition modules after some misfire issure and it felt like it picked up another 10 hp and went from something average to rev happy maniac. I never noticed misfire and never noticed anything amiss using degreeing wheel with strobe. But something must have been off. Ignition is important

about measurements; mine measured 172 rwhp prior to upgrading to 3.2 and dual spark, which is good. It still felt sluggish with a lack of 'willingness'. I'd never have known and would have been happy if I had not had access to my friends stock SC. May not be a lot faster but engine character is way better, to the point where I have contemplated taking his engine out and measure everything