Will I need a tune?

dogwhistle · 10-06-2014

I plan on doing another tune in the spring time at DB, but I will be receiving a new 63mm halfshaft 1g bored throttle body, and porting but manifold inlet and runners to match the ported head and new TB. I am curious if I will need a retune in the mean time though. I assume that since the MAF has already been corrected at the range of frequencies it can broadcast within the clamp, it should be able to calculate the proper AFR based on the tables for target AFR and it will be metered air since the flow would change as a whole so it won't go unmeasured thus being accurate and calculated. Or am I missing anything obvious or just hopeful and too confident in the MAF system? Thanks!

**goodhart** · 10-06-2014

You should be able to get by.

dogwhistle · 10-08-2014

10-4. I will be logging for sure and post what happens.

dogwhistle · 10-15-2014

After much forethought and some conversations, I concluded that the results would be fairly close but not ideal. The reason being that the MAF measures air velocity as it passes through, yet with a larger amount of air allowed through being compressed, it will reduce the velocity of the air and will not read the correct amount. On top of that, with more air allowed to go through, under boost, it will be compressed and further skew the results. Thus, the manifold machining and the throttle body install will require a tune to properly boost again. I will have it hopefully on the dyno by the end of November and let everybody know how much the difference is. Right now I cannot lower boost due to wastegate size but it will be 28psi as usual but going from stock to the new TB I expect anywhere from 5-25hp as a hopeful guess. I don't want more power ironically but I would like to be at a better efficiency and idle will be wonderful after Shane is done with it I'm sure!

**asshanson** · 10-16-2014

Where is your air flow metering? Are you using a GM MAF near the TB, or a stock style one in the intake pipe?

I don't think an immediate retune is necessary, though you may benefit from a tune. One of the main attractions of a MAF system over Speed Density is that it compensates very well for airflow differences.

**goodhart** · 10-16-2014

It really isnt a huge flow difference, thats why i said you should be able to get by. If you are concerned, just watch your afr

evotuner · 10-16-2014

Or wait to install it?

dogwhistle · 10-17-2014

GM 3"; It is about a foot or so from the entrance of the TB with a smooth aftermarket aluminum elbow. I guess this is the first time changing airflow after having a tune done. I dropped of the tb and intake with Aaron (Aaron's precision machine, my builder/machinist) and will see how far he went with it and bolt it all up and see. I will be sure to log and take notes. Thanks for the input guys!

dogwhistle · 10-29-2014

Holy shnikies! Best mod I've made in a long time. Solved tons of issues and makes the car easier, faster, and more fun to drive altogether. AFR's look great and actually may have helped the car perform safer and more efficiently.