Modding a car that has been previously tuned

Paulito · Nov 3, 2009, 09:38 PM

So I been buying some parts and just want to know if Im safe.

My car was tuned on stock boost, with a full TBE and high flow cat, and a drop in k and n filter and it was tuned to max out with no knock. (STU spec)

What I did/will do:

I took out the highflow cat (and swapped from a perrin exhaust to a hks) and replaced it with a testpipe and have not really noticed a difference in afr's (around 11.5-11.7 according to my aem wideband)... Dont know about knock as i haven't logged the car yet... is it something to be concerned about?

I'm about to put on a Perrin intake and want to know if it will be safe... will it cause knock? supposedly it doesn't mess with afr's but it does raise the boost.

i later plan on getting a licp, uicp, boost controller(@22-23 psi) and a front mount. at that point i will be getting tuned though

I just want to make sure im not going to cause any damage.

Thanks in advance

jmtx86 · Nov 3, 2009, 10:10 PM

Just keep an eye of your a/f after you install the intake, it will most likely mess with your A/F.

Paulito · Nov 4, 2009, 05:55 AM

what about knock though? supposedly according to perrin there is no change in afr

**MR Turco** · Nov 4, 2009, 06:08 AM

swaping intakes without at least taking some logs is not something i would advise. I always tell people to do all the mods they can before a tune, obviously, but to take it easy until the tune. No drag racing or road racing. If you have the ability i would always say take some logs and see where the car is at.

Also, before a tune, you should always do a boost leak test and compression test.

Paulito · Nov 4, 2009, 11:15 AM

thanks for the advice. when i log though, what should i pay particular attention to?

**MR Turco** · Nov 4, 2009, 11:27 AM

Knock sum and AFRs.

Paulito · Nov 4, 2009, 01:18 PM

Thanks, im going to check it out asap.

Right now my afr's are around 11.5-11.7 at wot and stock boost (18psi). last time i logged it i had little to no knock.

what would be safe specs for 93 octane and stock boost as far as afr and knock? I know 0 knock is ideal but just incase and does it matter where i get it in the power band. im going to do more research just to educate myself some more.

YogSaahoth · Nov 4, 2009, 07:52 PM

i was in the same boat a while back. from a tune with tbe w/ hfc, cone filter, fuel pump @ 23psi, i changed to testpipe, maf pipe, ported ex mani, ss o2 housing, 3" fmic and full piping. untuned we logged 7 counts knock. i had driven it like that for a month...you should be ok just dont drive like a maniac haha..good luck