I'm planning to put in my BC 272/272 in 2 wks. Just curious on what changes did u have to do or pay particular attention to when reflashing your car?

Mods: TBE 3", K&N Drop in, Walbro 255s. AND will be BC 272/272

My understanding is that since the duration is longer than std => more air
more air => pay attention to a/f as u may need to richen up some areas?
what about ign?

Thank you very much

 

Standard practice.....Adjust AFRs and Timing. Usually you won't be able to push as much timing.

 

I prefer to lower timing about 2* across the board to start, adjust the AFR's for the cams and then start increasing the timing until knock starts to occur. BC's idle pretty smooth so the only adjustments will probably need to do is increase your idle RPM a bit.

 

thank you both were u able to advance any timing after the cams?

 

I would rescale your MAF, along with the other statements.

 

Why? There is absolutely no reason to rescale his MAF with a drop in filter.

 

It all depends on the car really. Some cars can advance timing more, some can get back to where they were before the cams, some may even be less in certain areas. Just tune the car until IT tells you it is maxed out.

The MAF shouldn't need any adjusting with just a drop-in.

 

You can probably leave the timing the same up until 4500-5000 and the longer duration starts increasing cylinder pressure at higher rpm. Even with that I have seen VIII's that take more timing after cams than they did before.

 

Most tuners add a lil advance at in the low rpm, low load corner. Its usually at "5" on stock ROMs and people raise it anywhere from 7-14 with cams. It helps them idle better.

 

14? wow, never had to go that far,lol. I usually can get 272-280's to idle better with 2* more advance and slightly higher idle. If you use a Zeitronix wideband, you can use their narrowband simulated output and replace the front O2 signal which allows you to alter the target AFR from 14.7:1 to any other AFR target. MAking it a bit richer usually helps with big cams, like revolvers.

 

1. Start with a conservative boost, MIVEC and timing. Stock boost/MIVEC and around 1-2 degrees after 230 load cell. That is what I used on mine. My car was pig rich.... ~10.2.
2. Tune you AFR for your setup. I would do around 11.3 on 93 OCT.
3. Start to put some boost until the desired pressure. Adjust AFR.
4. Tune your timing accordingly. Adjust AFR.
5. Tune your MIVEC. Adjust AFR and timing if needed.
6. Once the baseline is safe, do some more pulls for fine tune all the parameters. At this point, I did some logs and TTP helped me to fine tune the rest.
7. Adjust target idle for around 900-1000. I used 8 on my timing at idle on my GSC S1s and not everybody can tell that my car has cams installed.

Expect a few pulls to get it right. A good tuner may have some baseline roms that will cut the iterations.... making it quicker.

I am not a professionals tuner but these are just my 0.02! Use it at your own risk! LOL