31 replies to this topic

[Pigeonto]

maximum advance i can put without pinging at high load is about 20 degrees, and when i put low grade petrol, then i cannot even think about fully opening throttle below 3000 rpm...............................
Sounds quite normal to me.You're all fully mappable so cant you just reduce the advance at high load until the pinking goes? I'm at 10.8:1 With megajolt and I drop the advance to 18 deg at high load from 1500 up to 3000 at which point it can go up a bit while still under high load . As long as you can cruise at no load(high vaccuum) with 33 deg and no pinking then its ok

[diogoteix]

Thanks for the reference point.
It seems then my advance is somewhat too high at low rpm / high load, and also too low at low load. I will try to adjust it and also make the adjustments for high air intake temperatures a bit more agressive, since it's another important facyor for pinging.
I'll post my before/after map as soon as i get old of a decent PC (i'm on ipad sorry for the spelling!)

maximum advance i can put without pinging at high load is about 20 degrees, and when i put low grade petrol, then i cannot even think about fully opening throttle below 3000 rpm...............................
Sounds quite normal to me.You're all fully mappable so cant you just reduce the advance at high load until the pinking goes? I'm at 10.8:1 With megajolt and I drop the advance to 18 deg at high load from 1500 up to 3000 at which point it can go up a bit while still under high load . As long as you can cruise at no load(high vaccuum) with 33 deg and no pinking then its ok

[diogoteix]

Not cheap indeed but nothing compared to trashing a nice head! And we are speaking of one of a kind gasket meaning they have to cut the various layers on demand, insert the various rings etc.. A bit more work than sending an order to a chinese wholeseller!

But it seems that I may have my way out of this issue without this investment, even better!
Thanks anyway for the company reference and prices.

Sounds like your problems are not CR based, but to answer your earlier question of where did I get my Cometic head gasket from and at what cost...

Ebay USA, this item (0.075"), US$126 + delivery (ouch!)
http://cgi.ebay.com/...=item35af7375ca

Not cheap but the only option I had - my head is already heavily worked and taking any more material out of the chambers could have trashed it

[diogoteix]

Here is my current ignition map

The problem seems to be somewhat more complicated from my first reaction to your comment since my ignition seems already quite conservative when compared to the figures you give!

As said before there can be various factors entering the equation:
- My "reference point" on the pickup sensor might be shifted by something like 5 degrees meaning that when you see 20° in the map below you should read 25°; from the history of the engine instalation / setup I would give a 75% probability
- temperature are quite high in Lisbon these days and I have some trouble cooling the engine; as a result the temperature of the air entering the manifold is quite high: about 35°C on highway during the day but between 45°C and 55°C in the trafic! The ECU can adjust the advance acordingly but I was only taking 1° advance at 50° C, and -4° at 60°C and 7° at 70°C; I think these were the default values coming from the ECU and I will shift them to something like 2° at 40°C, 4° at 50°C and 6° at 60°C. Above that I think I should get hold of a fire extinguisher!
- I will also try to get fresh air entering the engine by ducting the intake close to "the exit"; right now I just have a throttle body with a cone and a sock type filter, so at the back of the engine bay. In a previous setup air intake was a bit more "organized" and cooler: see picture
- lastly I promise never putting low quality fuel in my mini again. It was the first and last time due to the fact the petrol station was out of premium!

maximum advance i can put without pinging at high load is about 20 degrees, and when i put low grade petrol, then i cannot even think about fully opening throttle below 3000 rpm...............................
Sounds quite normal to me.You're all fully mappable so cant you just reduce the advance at high load until the pinking goes? I'm at 10.8:1 With megajolt and I drop the advance to 18 deg at high load from 1500 up to 3000 at which point it can go up a bit while still under high load . As long as you can cruise at no load(high vaccuum) with 33 deg and no pinking then its ok

[cooperrodeo]

With a compression ratio of 10:1 my Gunson compression tester (of unknown accuracy) reads 15-16 bar. One thing forgotten by those who wish to convert a compression reading into compression ratio is the fact that compressed gas suddenly gets very hot and gives a higher reading than otherwise expected.

[diogoteix]

With a compression ratio of 10:1 my Gunson compression tester (of unknown accuracy) reads 15-16 bar. One thing forgotten by those who wish to convert a compression reading into compression ratio is the fact that compressed gas suddenly gets very hot and gives a higher reading than otherwise expected.

Yes I was totaly wrong in thinking you could just read the CR of an engine with a compression tester. (see wikipedia for complete explanation and calcs)
That was the 1st interesting thing I learned with this topic;
The 2nd is the fact that with a wilder cam you can and should increase CR because all things equal the engine pressure will drop due to more overlap in valve openings. And what makes an engine knock is the pressure and temp of the gases, not CR.

Your readings are a good exemple: your CR is lower than mine (10:1 versus about 11:1), but your compression is higher (15-16 versus 12-12.5). I suppose you have a milder cam (mine is a SW 5-7) and/or no high lift rocker (1.5 in my case). Am I right?

Thanks for your info.

Diogo

[cooperrodeo]

My cam is a Newman Phase 2 which is perfect for what I want as a road car. Torque peaks at 4300rpm. I must check the calibration of my Gunson tester.

[makka]

if you are actually worried about the CR of your engine, why dont you pull the head off and measure it up properly instead of guessing with a pressure guage?

its not a hard job and will only cost you a head gasket

[Pigeonto]

cor blimey, that looks more suited to a racing car!! If your pickup isnt way out and telling lies it shouldnt pink with that little advance. Best wait for more comments from others with more than my little experience but maybe back to plan A and check the cr properly

[bmcecosse]

The compression tester gauge tells us that the Compression Ratio is NOT high..... You MUST use top grade fuel with a decent compression ratio. I suggest you fit a dizzy and get on with running the car - not messing about with a system that could be +/- 5 degrees?? I'm surprised at the low levels of advance you mention - a decent A series will want something in the range of 30/34 degrees advance to run well.

[diogoteix]

The compression tester gauge tells us that the Compression Ratio is NOT high..... You MUST use top grade fuel with a decent compression ratio. I suggest you fit a dizzy and get on with running the car - not messing about with a system that could be +/- 5 degrees?? I'm surprised at the low levels of advance you mention - a decent A series will want something in the range of 30/34 degrees advance to run well.

Regarding the advance the only big issue I have is that the alignment of the "missing tooth" of the crank sensor wheel may not be correct. When the engine was put back into the car, we add the surprise to see there was no missing tooth on the crank wheel sensor (from med-engineering). With engine in place, it was "taken care of" which was not easy due to lack of place. We had then to figure out how much misaligned with TDC the missing tooth was. About 5° but again with the engine in place it's quite difficult to tell precisely. My ECU has a crank alignment parameter. It is right now at 355°, but I may have seen the crank sensor to be aligned at -5° TDC when in fact it was + 5° TDC. If I change this parameter in the ECU then I have to add 10° to all ignition map figures, and you get the 30-34° max advance of the A-series...

[diogoteix]

The compression tester gauge tells us that the Compression Ratio is NOT high..... You MUST use top grade fuel with a decent compression ratio. I suggest you fit a dizzy and get on with running the car - not messing about with a system that could be +/- 5 degrees?? I'm surprised at the low levels of advance you mention - a decent A series will want something in the range of 30/34 degrees advance to run well.

I was not expecting such a big Impact of lower grade fuel and high intake temperatures. As for the fuel it's the first and last time I fill my tank without double-checking if the station has high grade fuel. For intake temperature I'll work on a way to bring fresh air to the engine...

Thanks for all your answers and advices!

[bmcecosse]

I was in Portugal 2 weeks ago and only saw one Mini - in Praia da Rocha........ yours??

[diogoteix]

If you ecu has a setting to allow for misalignment of the trigger wheel, why are you allowing for it as well ? The ecu will sort it out by itself surely, I know the megajolt can.

Sort it out by itself, what do you mean? Some kind of inteligent detection of TBC? I dont think my ECU offers something like that. We had to look closely at the position of the missing tooth while engine was put at TBC and guess how many degrees it was misaligned. With a relatively small trigger wheel, the precision is limited, 1 cm = about 10 degrees... And we may have wrongly guessed the direction putting -5 instead of +5° correction...

As a result my map seems way too retarded when in fact it is even somewhat too advanced in some places...

[diogoteix]

Sort it out by itself, what do you mean? Some kind of inteligent detection of TBC? I dont think my ECU offers something like that. We had to look closely at the position of the missing tooth while engine was put at TBC and guess how many degrees it was misaligned. With a relatively small trigger wheel, the precision is limited, 1 cm = about 10 degrees... And we may have wrongly guessed the direction putting -5 instead of +5° correction...

As a result my map seems way too retarded when in fact it is even somewhat too advanced in some places...

If you mess up your trigger wheel/vr sensor alignment you can offset the timing, in the software upto +/- 5 degree's.

Ok, that's the same for Emerald ECU, except that you enter the exact position of the sensor from 0 to 359º relative to TDC.
Today I will adjust everything and see if with a resonable correction for intake air temperature / water temp, all my problems of pinging get solved: I'm thinking of -2º advance at 40ºC, -4º at 50ºC and -6º at 60ºC, the maximum AIT I've read in my logs until now. I will also remove 2º advance at 90ºC water temp and -4º at 100ºC. So with a massively overheating engine (water at 100ºC and air intake at 60ºC) this would end up removing 10º advance. The car will be a cow but in a safe zone regarding pinging. That's the beauty of an ECU compared to a dizzy, quite useful when the summer comes in October (we will hit 31ºC today in Lisbon) and your stuck in trafic.



Cheers
Diogo