How much timing?

xtoy84

New member
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?


Josh
 

klue

New member
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.
 

xtoy84

New member
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?
 

RedCelicaTRD

Moderator
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.
 

xtoy84

New member
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!
 

$200GT-4

New member
xtoy84":2d86gc81 said:
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.
 

tissimo

New member
xtoy84":13ad70wh said:
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.
 

Hic

Member
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.
 

Simba

New member
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.
 

johndgt4

New member
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.

John
 

sleeper

New member
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.
 

$200GT-4

New member
15-16? Weak, I'd be thinking closer to 20 with 11.5:1AFR. I realize the 3S may or may not like more/less timing than the 4A-GZE I tuned, but I had it tuned to 25 degrees at 14-15psi and it absolutely loved it. I initially set it to 20 degrees advance under boost and every time I advanced the timing it gave a very noticeable seat of the pants difference. When I tore the engine down to come back to the states, there was NO indication of detonation. 15 to me is just atrocious, unless we're talking turbo'ing 11:1 CR Honduhs.
 

sleeper

New member
$200GT-4":18o01lxf said:
15-16? Weak, I'd be thinking closer to 20 with 11.5:1AFR. I realize the 3S may or may not like more/less timing than the 4A-GZE I tuned, but I had it tuned to 25 degrees at 14-15psi and it absolutely loved it. I initially set it to 20 degrees advance under boost and every time I advanced the timing it gave a very noticeable seat of the pants difference. When I tore the engine down to come back to the states, there was NO indication of detonation. 15 to me is just atrocious, unless we're talking turbo'ing 11:1 CR Honduhs.


hehe.. unless you have tested it on a 3sgte engine you should not recomend anything!

that engine will not be safe on 20 degree timing.. it does not like that.. trust me..
 

pinoyGT4

New member
so what really is the safest, but will still give you ample power, timing for the 3sgte?

can anyone indicate if there are specific timing for the different 3s generations and turbo that is equipped? stock turbo only.. :D

for example me, im running a 2nd gen 3s with a CT26... JDM GT4.. :D

what should be the appropriate timing for me? :D
 

Mafix

New member
in your case. none. take classes. learn. asking on the internet is not going to get you anywhere. rent a dyno and learn.
 

pinoyGT4

New member
Mafix":du405avg said:
in your case. none. take classes. learn. asking on the internet is not going to get you anywhere. rent a dyno and learn.

ohh... i thought i could learn a bit here.. and dyno here is too expensive, so i wanted to learn a few things before hitting the rollers..

and i dont think this is just "internet" coz the site is all about celicas and mostly GT4s.. :)
 
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