A buddy of mine just put a 402 in his car. The car doesn't want to start whether cold or hot without your help on the gas pedal to keep it running.

He'd had a heads & cam car with the 90/90 set-up prior. With the old motor combo the car ran just great.

The new 402 is running the same 90/90 set-up but with a bigger cam. Any idea as to what tables need help in his tune?

 

With a new cam your going to have to redo the ve table, maf tables, ect....
Basically a whole new tune, I might be pretty close but not close enough. Installing a differant cam changes how much air goes into the engine there for you need to redo the ve. I would start with the ve and see if the maf needs to be tweeked.

This is my understanding but keep in mind Im just a begginer at tuning.

Just my 0.02 Good luck

 

Thanks. Anyone else with ideas of where to start?

 

No other thoughts out there.......

 

I have some links you can read, what tunning suite are you using!

 

VE, IFR, IAC,MAF and maybe some timing..

 

IFR what is that?

 

sometimes with the 90/90 set up you need to adjust the Injector Flow Rate because of the different amount of air intake that the larger cam in causing...

 

do you just change it for the idel area or more?

 

A lot of times with the 90/90 you will need to get into the IFR to help in the idle and startup, but remember when you adjust the IFR this will also affect the WOT A/F so the PE will also have to adjusted..

 

...Ok I know you didn't just tell him to change his IFR for changing his intake....



Oh yeah, you did.... If you are a pro tuner and hack up people's cars doing this, you should be ashamed. If you are a novice and someone has told you this, take some time to read the VE tutorials. This poster has the tools in to tune his car RIGHT, not hack it up, and we should not encourage him to do such. The injector table represents physical injector constants. No need to cheat a table that you already have good data for.


The car needs to have the VE tuned and then the MAF re-installed and tuned (if he isn't staying SD). A good place to start on the VE to get it up and running so that you can start it's tuning is to multiply the 400 RPM column (assuming starting with a stock VE table) by 0.65 (65%), the 800 column by 0.70-0.75 and the 1200 RPM column by 0.85-0.9.

If it's still all over the place swinging take a bit more out. Spark tables need attention too.

 

Thanks for the thoughts thus far. The VE table has been tweaked in the 400/800/1200 areas by 50%/65%/80%. Spark has been added as well. The tune was working great on a stock bottom end with a big cam & heads plus the 90/90 setup. The problem has occurred since going to the 402 stroker and larger cam.

 

It's not a problem, it's just not tuned. If you have already made these changes, start VE tuning with your wideband witht he MAF disconnected and failed out.

 

im assuming idle air tables will have to be tweaked as well cause a 402 will want more air than the 346 which will affect start up and idle conditions.. may want to check your iac counts