COS help?

[yzriders182]

I'm just finishing a twin turbo silverado build and am now doing my research on tuning this thing. I'm looking at using a COS system ether 3 or 5. I have read the tutorial about COS3 and it seems like it will meet my needs. Any benefits to running COS5?

When I start tuning this (hasn't been started since mods) should I start with the MAF on on the stock tune then go to a COS and start the SD tuning or just go COS right away and with or without the MAF. I don't plan on running one once the tuning is done.

Mods: 60# injectors, cam, 2bar map sensor, and twin turbos.

Any starting help is appreciated as I'm new to EFIlive

[ScarabEpic22]

First off, what year Silverado?

If its a boosted truck, flash a COS in to start and STAY OUT OF BOOST until you get the Main VE table dialed in. How much boost? You're going to run out of MAF unless you're using a LS3/7 blade style in a larger tube.

[yzriders182]

Its a 2003.

It is boosted i plan on running 8-10psi. Maybe down the road bump it up to 12psi but that wouldn't be for a while. I know im probaly going to run out of MAF so I do want to go speed density right away.

How do I compensate for the larger injectors? Do I need to make changes to the injector tables before i start it for the first time or do I start it, log then make the changes?

Thanks

[ScarabEpic22]

Well that makes it easy, COS3 is your only option. COS5 is only for 512kb PCMs, you have a 1MB PCM.

With the new MAF sensors, you can scale them so you actually WONT run out of MAF, even at 12psi. The days of being forced to go SD are over.

You need to get ALL of the injector data from the manufacture so you can accurately update the IFR, small pulse adder, voltage offset, etc tables. Without the correct injector data, you WILL chase your tail forever.

[yzriders182]

Ok is there a write up or tutorial on how to do that on here somewhere? (update the IFR, small ulse adder, voltage offset, and etc tables)

Any reason I shouldn't go SD and stick with a MAF?

Here are the injectors I put in it.
http://www.bmotorsports.com/shop/pro...roducts_id/448

[yzriders182]

Any reason I would not want to go SD and keep the MAF?

Where can I get that information form the manufacture? call them or online some where?
These are the injectors I have. http://www.bmotorsports.com/shop/pro...roducts_id/448

Any links or tutorials that spell out how to make injector adjustments?

Thanks for all the help.

[joecar]

To scale injectors:
- first, measure rail pressure (taking into account FPR reference);
- calculate unscaled IFR for measured rail pressure, and populate IFR table;
- pick a factor (say 0.75 or 0.50) and multiply IFR, VE, MAF by this factor;
- look at all tables that reference airmass, and shift the table such that the airmass axis is scaled by the same factor;
- and so on.

[johnv]

Just go Mafless and get a 2 bar MAP sensor, you will need to calibrate the 2 bar sensor, and change you injector tables to suit the bigger injectors before attempting to start the engine.

[yzriders182]

I have a gm 2 bar map sensor so I need to adjust it to 190 right?

Sorry for the newb questions but were do I get the .75 or .50 from?

I need to pull my tutorials and books back out and go over some things before I ask to many more questions lol.

[yzriders182]

Ok I have all the proper injector data, cos3 installed and bugs worked out.

Im now trying to tune it and starting at idle. My wideband 02 is reading that at idle it is running lean (jumping between 15-17 afr) would I use table B3647 to make this adjustment? shouldn't it adjust automatically if it is set to 14.68?

Thanks for the help. Here is a pic of my B3647 table.