Stroker Ignition

**Billman** · 16 June 2011, 16:24

hmmmm...... I set it like this by listening to the knock sensor via the headphones Marc Swanson suggested. I thought i was listening to light knock thats why I pulled it back a bit.

Did you checked your engine with a scope to confirm that what you read on VEMS is your actual value?
You are using other cams as well, I think reclocked RS2 ones?

Do you have a knock listening tool like this so you can record a run of your car. I would like to hear another stroker except mine.

http://www.efiexpress.com/catalog/ar...?articles_id=4

**quattro84** · 16 June 2011, 17:48

I can't see why and how you are going to compare two numbers and make any conclusions.
For instance: Do you have similar fuel delivery specs? Injectors with equal placing/pressure difference/spray angle/timing etc. Airflow can be roughly predicted by speed-density method, So do you both reach the same targer AFR?
What about temperatures? backpressure? spark output? ... To be short: you need much more data before a compare. Currently developing an engine giving over 400kW of power in 5 different operating modes.. there are more ways to reach your (power) goals

I agree about checking the '0-point' timing-wise before even starting to compare and making any judgements... Total engine VE difference is undoubtably contributing to the difference in performance, but not solitary responsible.
There are loads of different factors coming into consideration giving or robbing output performance.

Define safety.. for instance running 10% turbocharger overspeed over supplier specs? For some it is because they have different goals and ideas about durability and mean time between service. (or failure)

Part of my job is to compare a dosin exactly 'equal' engines, 3d measured before build, build to spec and operating within same margins... conditioning both combustion & environment air temp/humidity/dew point/... and same goes for fuel.. Realtime measurements of indicated pressure and heat release and still i see considerable differences due to sensor spread, faulty grounding, deterioriation of (injection) equipment, ... My advice is to be careful.

**S2central.net** · 16 June 2011, 17:50

^^^ you have a cool job ^^^

**Billman** · 16 June 2011, 17:55

i am comparing them just for that. I am not going to change the values just to have the same as the other since I can hear my engine and only. If i could hear a knock sensor recording then I can compare if that what I am hearing as light knock is normal combustion noise ect.

for the rest it is understandable that very similar engines have due to tolerance or x other factors other output or need different timing but we can agree that i.e. Audi uses the same timing map for all RS2 car (+- the advance or retard due to corrections).

I would be interesting to know if the Motronic degrees JP states are absolut "ideal" timing advance without corrections.

Maybe PRJ has something to contribute here if he has mapped any strokers.

**quattro84** · 16 June 2011, 19:01

I reckon you can pull much more timing when running lower boost (compared to 'high' boost) before reaching knock limit.. doesn't say it is making max power when running max timing. It's all about to effectively use combustion pressure vs. crank angle (search for MFB50 or Mass Fraction Burn 50%, flame travel propagation).
Reducing timing at higher boost/power output levels while altering injected fuel mass can give some rather nasty effects on turbo'd cars (wasted heat turning into turbine energy) which can lead into points of no return...
Guessing by the fumes exited from JP's exhaust in the dyno vid he is running quite some extra fuel (perhaps for the cooling aspects) and therefore has an low A/F ratio at full load.

**Billman** · 16 June 2011, 20:42

He mentioned that flames came before the car was leaned out. He said that it was rich at this point.

Can the impeller size change the advance needed? I am think that if at 1 bar my turbo flows better that the 3076 maybe that alters the timing required (assuming same engines).

**S2central.net** · 16 June 2011, 20:53

Why not just wind up as much advance as it will consume before onset of knock at target boost on target AFR ? You can do this on a load bearing dyno to establish MBT for as many load points as you feel important... then back it off as much as you like for safety margin.

Start with something conservative of course... There are so many variables in play that its pretty impossible to compare such numbers between two engines.

**Billman** · 16 June 2011, 21:59

This is what I did apart from the dyno part. I must look to find a dyno I can use.

I was just wanted to see what others used.

I would like to hear other tuned engines to see is there is a major difference in the sound of the engine at full boost.

Knock is clearly audible with the sensor headphones but minor knock is not so easy to hear.

**quattro84** · 16 June 2011, 22:26

Impeller size does make a difference. If you are running in a different (read: higher) efficiency island it could be that the charge air temperature is lower. Though, your IC/piping/IM/TB diameter will differ so influence in temperature and speed will be different. What about the porting itself, creating a different tumble & swirl pattern makes that the combustion behaviour of the air/fuel mixture (yes it's Volumetric Efficiency again) could be completely different, hence my comment about comparing timing

I can't tell which swirl effects directly benefits power-wise, but i do know that emissions change drastically, so that must be related to in-cilinder temperature difference -> change in efficiency -> perhaps non-optimal ignition timing if aiming for max torque.

**prj** · 16 June 2011, 22:31

My limited experience with strokers shows that CR and the way the engine is built is much more important than it being a stroker or not.
Generally, I did not see much difference. Similar timing profile, just advance until it knocks, then go a bit back.

Also, 1 bar is baby boost

The cool thing about mass-flow ECU's is that you can map cylinder charge vs RPM as opposed to MAP vs RPM. A lot easier and generally the same timing map works for lots of cars with fairly minor adjustments.

This is as long as the cars are similar. If the motor has been altered a lot then you obviously ending up with something else....

JP · 17 June 2011, 01:20

The timing figures on my motor are what Mihnea put on there based on what he considered safe as a low boost baseline map. He's under the impression the engine wants to be leaner still with more advance but wished not to do so until he had a set of det cans on the engine. (AFR's currently being around 11.9:1 under load). This was mainly because both my knock sensor locations have been machined into the block to approximately simulate the original locations on the AAN block, therefore he does not wish to solely rely on the stock ECU to detect knock.

For further reference EGT's where between 720-740celsius measured at the exhaust port of cyl no.5 by the time he got into the 30's. Every time he advanced a bit more and leaned a bit more out the EGT's dropped and power went up. However once a smooth curve was achieved I asked him to hold it there so I could continue putting some more miles on the motor and clutch.

At the moment I'm in the process of machining up a new billet MAF housing with a larger cross sectional surface area. I will also plumb the boost controller back in after which we will actually go for a proper map rather than a temporary one after which we will most likely find a completely different ignition curve.

Personally I think it is a pointless exercise as every engine is different in compression ratio, build quality, VE, cam timing, turbo spec, injector spray pattern etc...... So there is never going to be a hard and fast rule of what the end ignition value should be. Something like that comes from experience and the only true way the optimum can be determined is on a load run on a dyno or the quarter mile. Where you keep advancing until the power starts going down again or the times start becoming slower. Assuming no knock is detected obviously.

**Billman** · 17 June 2011, 06:38

Originally posted by RWD19T

The timing figures on my motor are what Mihnea put on there based on what he considered safe as a low boost baseline map. He's under the impression the engine wants to be leaner still with more advance but wished not to do so until he had a set of det cans on the engine. (AFR's currently being around 11.9:1 under load). This was mainly because both my knock sensor locations have been machined into the block to approximately simulate the original locations on the AAN block, therefore he does not wish to solely rely on the stock ECU to detect knock.

For further reference EGT's where between 720-740celsius measured at the exhaust port of cyl no.5 by the time he got into the 30's. Every time he advanced a bit more and leaned a bit more out the EGT's dropped and power went up. However once a smooth curve was achieved I asked him to hold it there so I could continue putting some more miles on the motor and clutch.

At the moment I'm in the process of machining up a new billet MAF housing with a larger cross sectional surface area. I will also plumb the boost controller back in after which we will actually go for a proper map rather than a temporary one after which we will most likely find a completely different ignition curve.

Personally I think it is a pointless exercise as every engine is different in compression ratio, build quality, VE, cam timing, turbo spec, injector spray pattern etc...... So there is never going to be a hard and fast rule of what the end ignition value should be. Something like that comes from experience and the only true way the optimum can be determined is on a load run on a dyno or the quarter mile. Where you keep advancing until the power starts going down again or the times start becoming slower. Assuming no knock is detected obviously.

I would really love see what you can squeeze out of this turbo with your engine JP.

JP · 17 June 2011, 08:08

Personally I don't think it will be any more than 530 as I feel it was on the limits last time, just a nicer power curve leading upto it with maybe less boost. Then again I may be wrong but I got my doubts that it can flow much more then what it did before at the top end.

**andy10v** · 17 June 2011, 18:20

Originally posted by RWD19T

At the moment I'm in the process of machining up a new billet MAF housing with a larger cross sectional surface area.

For motronic? I thought Mihnea did not like that?

Stroker Ignition

Stroker Ignition

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