I went a few weeks ago to get tuned at Church's automotive...
I had my MY02 with greddy turbo kit, 60m exhaust, stock cat.

My car kept detonating when the car went into vtec. My tuner stated that the car is experiencing exhaust restriction problems, possibly melted cat. Due to my problem, he had to set vtec to 7.5k and asked me to shift at 6k, until i fix my exhaust problems.

My re-tune apt is today so last night i decided to install my berk test pipe and look at my stock cat. It did not look melted what so ever...

What else could cause a exhaust restriction or cause my car to detonate when vtec is engaged?

thanks in advance.

 

Is it a new kit? The kit usally runs best with a HFC and a 70mm dual exhaust. Or a reg cat and like a 70mm single. Was it hot out? But that guy has tuned a bunch of greddy s2000's so it sounds like he is asking for a better exhaust system caue yours ain't work'in. I have a invidia V3 for sale if your intresed, Joey Ball and I had really good success with this mated to the HFC and the greddy system. I just got the inline pro 3". It's in great shape, PM me if intrested. Good luck with the tune

 

does the greddy kit come with colder heat range plugs? are your plugs gapped correctly. it sounds weird to me that the exhaust would make the greddy kit untuneable. what i think happens is with a higher restriction exhaust, you make less power esp up top, and you run slightly less timing.

in any event, i would look to the plugs first.

 

I've never heard of a car detonating because of the exhaust...

 

You should be using a heat range 8 plug from NGK gapped around .030-.034.
What are you using?

 

I once had a turbo b16 that would never spool past 7 psi. I checked everything but could not figure it out, until I decided to replace the resonated piping I had for a 3'' exhuast. The thing spooled past 20psi when I got it out of the muffler shop. I never experienced any detonation from the excessive back pressure that even kept the turbo from spooling. I could be wrong but combustion probably occurs at a lower temperature since there is excess exhaust gas in the chamber due to higher back pressure, making it more difficult for knock to occur.

 

I replaced the plugs with a 1 step colder heat range, i would not mind changing out the plugs once more prior to my tune... i just need to find a set. I forget the product # for the NGK plugs, i will pull them out on my lunch and check the gap...

i have a tanabe SMH exhaust that starts out as a 60 to a dual 50... Sean church saidt it would be fine for my application.

 

BKR8EIX NGK's are your friend. They also come pre gapped at .030.

I still have that other tune if you want to try it.

 

^^ those are the same plugs i got in there right now.
I checked the gapping, and they were all like .028 to .029... i have regapped them to .031

The base of the plug was black and the tip was white.. what does that mean?

 

get at least a 70mm exhaust. 60mm splitting to 50mm is restrictive for a turbo s2k.