7 port ignition mapping issue.
Turbo Mini Forums

This is something that Vizard talks about. What looks good on a dry flow bench, is way off the mark on a wet flow bench, and what looks good on a wet flow bench, looks way off the mark on a dry flow bench, but the best wet flow nets an improvement over the best dry flow on the dyno. He also talks about putting material into the ports in certain areas rather than taking it out. Big is not always better.

Edited by Sprocket on 2nd Sep, 2012.

But even then, 3thou should not be worth 20ft/lb.

Class C 3rd Place Avon 2011 14.18 @101mph

that 3 thou has changed the characteristics of an incorrectly timed cam quite a bit. It might be closer to what the cam should be timed at but loosing some of the duration as a downside

Edited by Sprocket on 2nd Sep, 2012.

To be fair, that 3thou change brought it back to more or less where it was with twin webers, 1.3 Rockers, 10-6-1CR and cam at 108. Its still down by about 2bhp almost everywhere. Same rollers, but different day.

Class C 3rd Place Avon 2011 14.18 @101mph

Going back to the ignition advance for a minute. Understanding why you need any advance other than firing the spark at TDC in the first place, should help you understand that 47 degrees, or even 37 degrees at full load is a bit much.

Ignition advance before TDC is required to allow the cylinder charge to burn and generate it's peak cylinder pressure at or near 14degrees after top dead center. This 14 degrees is a fairly common value, and has a lot to do with the geometry of the engine (stroke and rod length) It is basically the point at which the piston starts to travel down the cylinder, after the dwell period around TDC.

The cylinder charge takes a short time to start to burn and generate this cylinder pressure, so initiating the burn (spark) shortly before the piston has even reached TDC allows the cylinder pressure to peak at or around 14 degrees ATDC. Too early with the spark (34 degrees and higher) and the peak cylinder pressure occurs too soon with the piston at or before top dead center, loosing power and torque at best, detonating at worst. Initiate the spark to late (34 degrees or less) and peak cylinder pressures occu, chasing the piston travelling down the cylinder, loosing power and torque.

The dyno should be used to find that sweet spot, and for all the A series engines I've had on the dyno, that occurs at around 28 to 34 degrees (16v and five port) What was evident was a reduction in power when going beyond the optimum advance, by as little as 2 degrees, without detonation. Removing those extra 2 degrees saw the power return, and removing another 2 again saw a drop in power.

If your engine really does need 47 degrees advance, there is something fundamentally wrong, whether it is a very low compression ratio, incorrectly timed cams, poor cylinder seal, charge contamination, really really high fuel octain, or just poor quality burning fuel. It could be any number of things Since unleaded burns really well, it usually requires less advance, with perhaps the higher octane unleaded requiring 1 or 2 degrees more than the lower octanes.


I really do hope you can find the answer, bUt i also think you should allow the engine to rev more to reap the benefit of that cam. I took my 1400 to 7000rpm with standard rods and bolts with no center strap, but that was the absolute max on the MD274 cam I had in there. Bottom line here is poor burn = more advance. Efficient burn = less advance.

Now I'm not saying that this or that engine doesn't need that much advance, what I am saying is that a well built A series using a veriety of different types of head, in the main need much less than 47 degrees

One other thing to consider is that I have not seen too many 1380's break the 100bhp mark with the MD286 cam, so your power figures don't look too too bad, IMHO. A well built and set up 1380 with the MD286 should see 110hp at least i'd have thought.

I totally agreed colin there is no way 47 is correct. Ive even got to 52 degrees and didnt pick up any pinging.

Like you say the power isnt all that bad at 98bhp at the wheels and 119bhp at flywheel so the setup isnt massively underperforming.

Its acually very simlar to the SC 7 Port in terms of power and torque with a smiliar duration camshaft.

Ill get to the bottom of this, just need a day of work to have a more detailed look.

Class C 3rd Place Avon 2011 14.18 @101mph

By reducing the tappet clearance you do reduce lift on overlap , effectively shorten cam duration a bit , increase acceleration of the seat. So it could reduce overscavenging (resulting in a lean mix that needs a bit more time to burn ???). (did the timing (best torgue) change when you increased tappet clearance).

it 52 degree is rather a lot so the effective trapping efficiency must be quite bad otherwise it would at least pink a bit (most engines would probably have detonated i guess).

Could it not just be the weird plugs ??? that is the factor that has remained constant. was the advance the same with the webers ?

maybe a stupid idea but have you considered sticking a normal distibutor just for testing if you need the same amounts of advance??

Edited by Sir Yun on 2nd Sep, 2012.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

I was running a non vacum Aldon Yellow dizzy with the webers, im sure the max advance was 34degrees. I didnt pay that much attension, just swinged the dizzy until peak was found.

Igntion wasnt changed after the tappet clearence adjustment. It was the end of the day and I ran out of time. Maybe a there a few degrees to come back out?

Ive still got to spend another day on the rollers to sort the rest of the map.

Class C 3rd Place Avon 2011 14.18 @101mph

What's your coil and ignition driver setup?

Any chance that the plugs are firing later than the ECU suggests?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

yeah, have you checked the timing with a light at high rpm to check its not going Awolas speed increases.

ok so 34 degree with a weber.. sounds a lot more sensible. so either the spark is off or the fueling

It could be that increasing the tappet clearance reduced the reversal. With a injector this might be worse than a weber if you inject at a time of charge reversal.

as said that port is big and probably quite slow and i'd say very prone to reversal.

if the exhaust system is mismatched as well it could be a case of a lot of variables leading to this result.

all conjecture off course .

could you stick in the aldon at 32-34 degrees max and just let the ecu do fueling to see if it cures it.

can you fiddle with the injector timing ?

oh.. did you check the injectors ?

oh nr 2 what kind of plugs are in there now R or normal ? and what leads ? what is the resistance of the leads.



well i hope you figure it out

Edited by Sir Yun on 2nd Sep, 2012.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

No have havnt check timing with strobe at high revs. I wish I had before I remove the head. I was sure I'd mark TDC wrong, so didn't really try different timing light test.

It must be out only at higher revs, because it idles fine at 20degress. It wouldnt be anygood a 5 degrees if the whole thing was out by 15.

The coil, leads and loom are all suppied from MED, as a kit, put together by Mike Barrett Engines,

I have not changed any setting from the base map ie. Coil on time etc.

Class C 3rd Place Avon 2011 14.18 @101mph

Edited by alaskanow0 on 2nd Sep, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph

Sorry, what's. reversal?

Class C 3rd Place Avon 2011 14.18 @101mph

Edited by robert on 3rd Sep, 2012.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I never checked the timing a high revs with the gun. I think I need to put the head back on give it a try.

I think am also going to see what happens when I put 1.3 rockers back on.

Class C 3rd Place Avon 2011 14.18 @101mph

Ok ive measured the total amount of valve movement before the topcap hits the stem seal and guide. Its .476thou, which is above the 0.436 lift giving by the SW10 with 1.5 Rockers. But this does seem that the guide is sat too high.
The valve is polished by the guide right upto the point that is runs out of movement, which suggests it is lifting to that point.

I guess I need to measure cam lift and actual valve lift with the head and rockers in situ.

Is there any change the SW10 as more lift than 0.436.

Next job, speak to Nick Swift.

Edited by alaskanow0 on 3rd Sep, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph

Surely you should have well over 500 thou of full travel. If you were using a 310 cam, like me, it would all bind up

I seriously doubt it!

Spoke to Nick, Cam timing should be between 106-108, Hes says it doesnt make a difference. The valve lift is correct at about 0.436 with 1.5's.

He give me some figures to measure valve lift at TDC, to confirm cam timing.

He agrees 47degrees is to far out to be the cylinder head underperforming, it must be sensor postion, TDC marked wrong or wrong figure on ECU.

Edited by alaskanow0 on 3rd Sep, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph

If 3 thou on rocker clearances can make such a dramatic difference as you have seen (being such a small adjustment difference), surely 2 degrees on cam timing must change it, Im quite surprised Nick said that tbh

I seriously doubt it!

I told him I had timed it all 106 degrees, he said ' that fine between 106-108 makes no difference to torque and power'.

Class C 3rd Place Avon 2011 14.18 @101mph

I wouldnt doubt what he says

I seriously doubt it!

hey if Mr swift says that i would believe him as well.. but if 3 thou makes 10 bhp..

As you have the head off it's easy to check it reversion was happening in a bad way. just take out the intake valves and see if the port looks exhausty


http://maxracesoftware.com/pipemax36xp2.htm.

anything weird looking about the burn patterns on the head and piston? (pics?)

I would first try to gain all this info while the head is still off before you put it back together.


I would suggest re starting from the beginning ( even though it sucks eggs, but i have fought with an engine for months.. never got it quite right before some guy ''fixed'' it and blamed me for everything that went wrong. I should have re started from square one i would have saved me shitloads of headache).

trouble is that AFR and timing are interactive (so changing one thing at at time might for a change not be such a good idea) and sensors can ‘lie’ to you ,so it is best to keep the number of unknown variables to a minimum. For instance a wildly overfueled engine will not burn at all and just read normal of even lean because of the unburned charge containing oxygen ( which the sensor will read and tell you that all is a-okey)

I'll just try an list what I would try (i'm shure you know most, if not all of this so no offence meant). I have learned from my day job that when you have no #$^% clue why a patient is dying.. start over. regardless of what you think you know.. it does tend to work sometimes. oh you can have fleas and lice..

make a list of everything you measured.

1) establish TDC beyond any doubt. Mark clearly with bright white paint in the and use a pointy indicator
2) re-time the cam ( i know it is annoying but I have triple checked a cam only to find later after running it for a while, that it was still not what is was when i put it in.. chains can and will stretch sometimes to the extent that the timing is way out.)

3) Test the injectors. they can and are sometime DOA , have weird spray patterns etc etc. If not you know that they are good and thus one variable less to worry about..

4) Setup that head as normal. reset tappet clearances (when setting up rolled rockers don't wedge in from the front. put in gauge tighten till you can still shuffle side to side with quite a bit of resistance).
Any bind ( coil/guide/whatever) you already checked.

5) Do a compression test.
Check ECU:
TPS/MAP working ? ( probably TPS with the ITB’s)
No enrichment anything setup.. triple check every bit of software setup.
Temp sensor OK ?
Lambda working properly (no chance of it having been poisoned by RTV silicone or something stupid like that)
Is the crank sensor properly gapped and the fixture bombproof ( judging from the rest of your very nice engine bay it should be ok) . Toothed wheel not reversed ( if 2 missing theeth)
No broken plugs (been there)
Plug leads intact and the right kind. (Measure resistance. it should be around 12 K Ohm isch).
It is probably best to borrow/lend/ steal an oscilloscope to check the output from all the sensors.

http://www.ngksparkplugs.ca/tech-info-oxygen-sensors.cfm.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

I once saw a similar issue with a Mopar V8. It had excessive amount of advance while the engine ran spotless and if set to typical advace it would not ran at all. Turns out the two dizzy wires were connected incorrectly, once they were connected correctly, advance set by ear and checked with a timing light it showed typical advance values.

Can´t really say whether this is the culprit here but possibly worth checking ?

Ok, I might be onto something. Nick said to check Exhaust lift at TDC on Pot 4. It's 40thou down.
Looks like engine out then, and investigate.

I checked the cam timing 3 times, when I rebuild it though.

Looks like this could be the cause of all the problems?

Edited by alaskanow0 on 4th Sep, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph