Related to the Bowling & Grippo Fuel Injection system.
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Michael
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24v Ignition advance map

Post by Michael »

Hi:

Soliciting opinions on the advance curve I should be using for a 24v. I used the 'general guidelines' in the Megasquirt documentation to create the map.
Can runs OK (fuel mixture is good using TunerStudio AutoTune feature), but I think the acceleration could be better with more aggressive spark advance...
Is 26 degrees at max load appropriate?
AlfaV624_MegasquirtIgnitionAdvanceCurve.JPG
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Re: 24v Ignition advance map

Post by fedezyl »

What compression ratio do you have? I can give you the spark table for my 33 16v, it's based on the original motronic one and the full throttle part on a dyno. I think the bore is similar and it's a 4 valve per cylinder head.
My compression ratio is about 10,5 to 1 and cams have 240º duration at 1mm lift
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Re: 24v Ignition advance map

Post by Michael »

My engine is pretty stock - between 10.5:1 to 10.7:1 compression.
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Re: 24v Ignition advance map

Post by Duk »

You really need to be able to get the car onto a brake type dyno. That way you can hold the engine at each of the rev and load points and tune the ignition timing to acieve the best torque output/tractive effort for each of those points without detonation/knocking.

The advent of well priced wide band air/fuel ratio meters has been a huge plus for the DIY car enthusiast. Ones that data log various sensor information are even better again. Self (fuel) tuning computers are better again. But getting the best ignition timing is still big challenge. I'd like to see some sort of torque reaction gauge like a load cell attached to an engine (that's all a brake dyno uses, a load cell that gets pushed or pulled by the dyno's brake) and have the cells signal conditioned to suit a 0-5 volt data logger like the Innovate LM1/2, plot that signal on a 3D map against engine speed and load in the same way the ignition timing is mapped, drive the be-jebus out of the car in the real world and see what sort of data you have. Then make some educated changes and see if your results improved (load cell out put increased) or not. Use microphones attached to the engine block to listen for detonation when driving and correct before it becomes a problem.
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Re: 24v Ignition advance map

Post by WhizzMan »

After reading this, I suddenly realized that you could put a compression type sensor in one of the engine mounts. You'll need to calibrate it and fiddle to get it to be sensitive and in working range, but the general idea should work.
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Re: 24v Ignition advance map

Post by fedezyl »

Mike, here's the stock spark advance on a stock 33 1.7 16v, boxer engine from the motronic 4.1 ECU.

I used this spark advance with only one or two degrees more advance in the mid range but otherwise worked great.
The only thing different on my spark advance was the advance at full throttle, I have 4 or 5 degrees more depending the cell in the map, but I got that dialed in the dyno for best power.

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Re: 24v Ignition advance map

Post by Murray »

Michael, I'll start with the usual disclaimers :roll: This table may not be suitable for others to use or even consider, so procede with caution.I've been running this advance table on my 86 GTV6 2.5 for 3 years.Engine is approx 10:1 due to shaved heads.I run S cams and standard Bosch distributor modified to work with Megasquirt .Distributor advance is completely disabled as MS calls the shots.I fire my plugs off a Jacobs high output coil and my plugs NGK B6's have the gap set at about .035 I run regular fuel and have lots of track miles with lots of high RPM runs as well as daily use during the summer.I've never had an issue with detonation and the car pulls like a train :twisted: When I started creating my tune I was very cautious and had max advance @ 28 deg.After a lot of research I started bumping up my values until I was happy.Needless to say your engine is a different beast and my results probably won't apply to you but if nothing else I've found that the little Hemi likes lots of advance.
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Re: 24v Ignition advance map

Post by fedezyl »

The multivalve combustion chambers usually call for less advance than the hemi chambers, the advance needed on the 24v is for sure much less than the one needed in the 12v
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Re: 24v Ignition advance map

Post by Michael »

Thanks everyone for the feedback - I'm going to take my car to a Dyno ... Saturday to set the spark advance map - and also compare Gotech (which I removed) with Megasquirt...
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Re: 24v Ignition advance map

Post by kevin »

Michael, difficult to give you info advance curve as I am at high altitude but from I hear you should be at least 28 degrees on max load from 4000 rpm upwards .
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Re: 24v Ignition advance map

Post by fedezyl »

sounds about right, I have 26 and 24 depending on the revs, actually 26 at about 7600 rpms wich is peak hp for the boxer 16v I have
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