How much timing?

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How much timing?

Postby xtoy84 » Fri Nov 21, 2008 3:36 am

How much ignition timing for 1 bar of boost is recomended?

I have an 88 st165 with an st205 engine and using an AEM EMS.
I tried the using the preloaded ignition map and broke two pistions quick!!
I thought the maped looked like it had to much timing?


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Postby klue » Fri Nov 21, 2008 4:10 am

The aem basemap is tuned to get you to the dyno. Its about 10-13 degrees into the danger zone. There are many reports of people doing the same thing. sorry you had to learn the hardway.
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Postby Corey » Fri Nov 21, 2008 8:13 am

Stock timing is 10, should start there?
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Postby Mafix » Fri Nov 21, 2008 1:50 pm

total advance...on a base map just retard the timing out in boost until you get to a dyno
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Postby xtoy84 » Fri Nov 21, 2008 4:59 pm

Sounds good Ill probably just run 10 degrees of timing until i get to a dyno. So how much advance can a 3sgte take before knock with a good 12-1 AFR?
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Postby Mafix » Fri Nov 21, 2008 5:24 pm

12-1 is too lean IMO
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Postby RedCelicaTRD » Fri Nov 21, 2008 6:08 pm

On pump fuel you would want a ratio closer to 11.5:1 (maybe even a little richer). Each engine is different so noone will be able to give you an exact answer.
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Postby xtoy84 » Fri Nov 21, 2008 7:40 pm

That seems a little rich but I guess its better to be safe. I've heard you get best torque at around 12.2 but wont know for sure until its on a dyno!
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Postby Mafix » Fri Nov 21, 2008 8:14 pm

most 3sgte engines seem to run best at 11-11.5 in boost.
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Postby $200GT-4 » Mon Nov 24, 2008 7:49 am

xtoy84 wrote:That seems a little rich but I guess its better to be safe. I've heard you get best torque at around 12.2 but wont know for sure until its on a dyno!


Yeah, but then the weather changes, you get bad gas, or maybe the stars don't quite line up and instead of the 12.2 you tuned for you're running 13:1 and kaboom. 11.5 gives you more leeway. Much richer than that and you're just trying to cover up excessive compression, boost, or ignition advance.
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Postby tissimo » Mon Nov 24, 2008 3:36 pm

xtoy84 wrote:That seems a little rich but I guess its better to be safe. I've heard you get best torque at around 12.2 but wont know for sure until its on a dyno!

most of the time 13-13.5 a/f will give you the best power/torque. The reason turbo cars run rich is cause the extra fuel cools down the combustion and makes it safer.
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Postby Hic » Tue Nov 25, 2008 10:06 am

this is simply not true and if you sit in a car on the dyno, you can prove it to yourself in 3 minutes.

the best power will come around 12.4-12.3. i tuned more than 200 cars till now and every one of thec fell into this margin.

13-13.5----it is too lean...you can see rise of torque and power instantly when adding JUST fuel, not to mention timing.
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Postby Simba » Tue Nov 25, 2008 4:41 pm

Depends on the engine, fuel system, power levels, intercooler efficiency, etc, etc-- e.g. if you go get a Ford Racing supercharger for a mustang, the stock ecu flash will have you around 13:1. Paxton blower on a Viper, around 12.5:1. Both make huge power for the amount of boost, and are completely safe on pump gas. However, both run on relatively large displacement engines with relatively little boost and timing.

On a small displacement, high boost engine, you want a richer AFR. I have holed pistons running ~12-12.5:1 on a 3S on a road course in hot weather, on 100 octane race fuel. That AFR may be reasonably safe for a street driven car that only sees full boost for prolonged periods once in a blue moon, but it's not worth another 10-20 hp to risk melting your engine, in my book.

11-11.5:1 is much safer, you can run more timing and the tune is more forgiving to atmospheric and fuel variations, of which there are a LOT in pump gas.

As for timing, it again depends on all the other metrics of the engine and power goals. If you're running a stock stroke 3S at ~15 psi, I would probably start with 10-11 degrees of base, 30-35 degrees under light load/boost, and pull it back to ~15-20 degrees over 5 psi or so.

Those are very rough numbers, of course, and you'll have to dyno tune your timing based on knock and other factors, and leave a few degree margin of safety for temperature and fuel variations.

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Postby johndgt4 » Wed Mar 25, 2009 11:39 am

This debate is just plain silly....

If you have fitted an EMS and don't know how to tune it yourself you do this:-

1) Drive very carefully with hardly any boost to your RR.
2) Get someone to MAP it who knows what they are doing.

End of!

Sorry Josh that is the ONLY way to do it unless you are fully conversant with mapping.

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Postby sleeper » Wed Mar 25, 2009 11:05 pm

on a stock 3sgte i usualy end up at about 11.6-11.7 AFR and about 15-16 ign adv ( this is on 99 RON pump fuel ( about 93.5 on your fuel rating.) on 15-16 psi boost

But if you are not experinced with tuning engines and know what you are looking\lisstening for i`d just sett it to about 13-14 degree.
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