Why set IAM to 1.00 when tunning

[Turdinator]

There may well be a good reason for this. Why do tuners set the initial IAM to 1.00? Why not leave it at 0.70 and adjust the timing tables accordingly? From the reading I have done, on petrol (gas) power is limited by knock. I have also noticed that knock is very temperature related. In winter, on Shiv's OFT tune, my IAM almost never drops below 1.00. In summer in heavy traffic it will drop but usually comes back up again once the heat soak is reduced. So how do I know that in ideal cool temps I couldn't be running more timing advance and making more power?

TL;DR Why don't we set the tunes to IAM of 0.70 with adjusted ignition tables so in ideal conditions the ECU will add some advance?

[steve99]

Suspect probably multiple reasons

one of them probably saves time on dyno, after each flash you dont want to have to run car for a while to set iam back to 1 to check your timing is not going to knock like crazy once iam get to 1 from the initial 0.7.

Its probably not the best for smothness and the engine to be constantly knocking then reducing timing by use of iam to correct timing. This would hapen if you tuned for iam as 0.7

my understanding is the ecu is always trying to set iam back to target of 1, its trying all the time if it detects knock it will stop incrementing iam or reduce it depending on severity and instances of knock detections.

IAM is the ecu s method of coarse correction due to lower octane fuel than specified or optimum being used

most peple with tuned cars dont like to see or hear knock so they need iam at 1 so tune running max advance. with little or no knock on your prefered fuel

most tuners will assume or require that your going to run premium fuel. or a specific type of fuel.

for say our G rom its same for australia south africa and europe. The South Afrcian guys only have 95rom fuel , but use same stock rom setting as oz and europe on 98. So by setting iam initial at 0.7 in stock rom they avoiding large knock corrections for people aways on 95 fuels

tuners they probably want to see and tune for max advance and then give the ecu the maxium ability to pull timing if necessary.

if they tuned at 0.7 then 30% of ecu headrom to reduce timing is not their

you dont want the extra variable of iam moving arround while your trying to tune.

if you have high intake air temp related knock you would be better reducing or eliminating that knock with the IAT temperature compensation tables rarther than base timing or letting your iam drop. then you only dropping advance at high temps and on cooler days your getting your full advance and power or when your not stuck in traffic and iat is cooler.

[Kodename47]

The IAM is really more there for fuel variation than anything else. Why set it to 1, a few l possible reasons:
- Can be tested straight away
- Customers don't think their car is "down on power"
- Is it good to have the engine constantly knocking that the IAM is always below 1?
- How much performance is actually left no the table?

I'm not one of those that minds the IAM wandering a little However I'm not a great believer in allowing the engine to knock just to eek out a bit extra a fraction of the time. I'd rather leave a safety margin. However, it's your car, so why not try it?