Cam timing vs Fuel/spark map - Which to fix first?

[Danbob]

Hello,

Background
I’m about to start tuning my MS3x equipped car for the first time. (MR2 3SGTE Gen 3)
I’ve just finished building the engine and car is currently being run in on the OEM ECU until I finish my link harness
I have adjustable cam gears running HKS 264 cams.
I intend to tune the bulk of the fuel and ignition maps myself using wideband lambda and visit a dyno a few times to fine tune.

Request
My question is, in general is it best to:

1. Optimise the Cam timing on a dyno and fix that first, then go out and tune the fuel/spark?

2. Or optimise fuel/spark first at any given cam timing, then optimise the cams afterwards?

3. Or does this have to be an iterative process, Fuel/Spark then cam then back to fuel/spark again?

Basically it would be good to know if the cam timing can be set independently of the fuel/spark maps (assuming map is good enough to be safe)?
Does the optimum cam timing (for your chosen engine characteristic) rely only on the physical characteristics of your engine? Or is it dictated by the spark/fuel and boost maps? Or both?


Seems difficult to find solid factual information on this.

Thanks
Dan

[EspeNS]

I guess you already have timed the cams to lift at TDC or max lift at X degrees at crank, and just have to fine tune them?
Don't know about MAF, but in SD and AlphaN tuning of the cams will alter the engines VE, and hence the VE and ignition maps.
I see no use in optimising fuel and ignition before cams.
But a good base ignition table and some hours tuning with VEAL while driving before optimising cams, fuel and ignition in a dyno I think is a good idea.
Also measure real deadtime and cc for injectors before dyno.

[Danbob]

Hi, yeah I dialed in the cams to the HKS recommended centerlines. However at these settings the car would not idle on the stock ECU (Speed density), so I moved the exhaust cam back to the OEM centerline which has allowed it to run and idle well for the running in miles.

OK, that makes sense to me, adjusting the cam timing will change the VE, which alters required fuelling, so set the cams firs


For simplicity does anybody see anything wrong with taking the car to the dyno on the stock ECU (Which is happy fuelling up to around 16PSI boost), and setting the cams to their optimum setting for high RPM at the dyno first before even starting to tune the megasquirt?

[Danbob]

Bump

Any more opinions on this?

It's there a defined order/method for tuning that is generally the correct way to do it?

Thanks
Dan

[suberimakuri]

I reckon set cams to HKS recommendation and drive round on MS. Then dyno once you got it pretty good. You can set a real conservative timing map until dyno.
Perhaps after your run in ks.
This way you get your ve table close and any small bugs worked out... Warm up enrichment, Accel, boost control.

[Danbob]

Hi, yeah that sounds sensible, I have the hks cam card settings marked on my cam gears now so I can easily swap them back to that once the mega squirt is plugged in and get it idling on the ms3 with the cam's like that, then get the maps set up basically right and swing back he came at the dyno for the final tune