Need some help: VTEC not engaging

**black8thgen** · 11-12-2012 09:27 AM

Hey all..

So i installed my J's racing 70RS Ti single exhaust last night. I previously had a skunk2 dual exhaust 70mm on.

As soon as i installed it i took it out for a run. After letting the car warm up to appropriate 3 bar or whatever i tried hitting vtec and it wouldnt engage. It just bounces off like a rev limiter at 6k RPM and cuts the accel.

My theory is that the silencer that came with the exhaust was originally wrongly sized and for a 60mm js exhaust (the hole is TINY and smaller than the pics I looked up online for the 70mm silencer). Maybe there is too much backpressure from the silencer and the ecu is trying to protect the engine and not letting vtec engage?

I can't get the silencer out myself as its stuck in there - planning to go to an exhaust shop tomorrow but i was just wondering if anyone else has ever had this issue?

After looking up some online posts i did find someone with a similar problem (the resolution was they ordered the wrong sized silencer).

My oil levels are fine, car is warm (so its not those common problems).

So final questions:
1. has anyone had similar issues?
2. any recommendations? (I'm planning on resetting ECU as it could just be an AFR issue from going from a dual exhaust to single - this i kinda doubt though...)
3. If it is the excessive backpressure from the silencer, will this damage my engine by driving around with it on?

Thanks all!

**DakDak** · 11-12-2012 09:45 AM

The 02 sensors all good?
Back pressure shouldnt cause stop your VTEC from engagement. The J's exhaust with silence will still be less restricitve than a stock exhaust.
Give the ecu a reset. I reckon because the exhaust flows better, the sensors think your leaning out not letting you hit VTEC as a precaution.

**black8thgen** · 11-12-2012 10:19 AM

Yeah 02 sensor is just on the cat yeah? We didnt touch or knock the cat out of whack to displace the sensor i dont think. I'll give it a quick check later anyway in case.

EDIT: Also, if it was an 02 sensor issue - it would throw a CEL correct?

Hmm yeah i was thinking that too.... well its not as if i was coming from a stock exhaust. I had a skunk2 70mm which should sort of flow similarly to the Js?

**curtis265** · 11-12-2012 10:41 AM

reset the ecu and tell us how you go

also check your vtec fluid while you've got the hood open

**black8thgen** · 11-12-2012 11:04 AM

I will reset the ecu tonight after work and give an update.

and yeah i have checked oil level its all good

**pure_na** · 11-12-2012 01:07 PM

I have a pos exhaust that i put on my car to clear epa once. it is clogged up with crap, stock exhaust. it won't hit vtec because of the shit that's in it = too much backpressure or some crap. pretty sure that is your problem.

try something for me, floor it and try to hit vtec, see what revs it cuts at, then *slowly* try to hit vtec, see what revs it cuts at. should rev slightly further if you do it slowly. then again, mine is clogged differently to yours, not with a silencer, so this may not prove anything if it cuts at the same rpm each time.

so it turns out memory did not serve me correctly. the car should still hit vtec with the silencer. mine was correct silencer though so yeh

so yeh, get the silencer out is my advice. as for damaging your car, i've spoken to a few people about it as i had to put the clogged-up stock exhaust on for a couple of days when i was clearing epa. they reckon it won't damage the car at all, i am also of the opinion that it won't damage the car at all as it reved freely so long as i didn't try and hit vtec. but it's pointless as the car is worthless without the top third of it's rev range :P.

**lolmclol** · 11-12-2012 01:11 PM

inb4 flux capacitor check.

**butterfingers** · 11-12-2012 01:12 PM

actually blocked exhausts and cats force exhaust gasses past piston rings, taking the oil with it.

**black8thgen** · 11-12-2012 01:24 PM

Originally Posted by pure_na

I have a pos exhaust that i put on my car to clear epa once. it is clogged up with crap, stock exhaust. it won't hit vtec because of the shit that's in it = too much backpressure or some crap. pretty sure that is your problem.

try something for me, floor it and try to hit vtec, see what revs it cuts at, then *slowly* try to hit vtec, see what revs it cuts at. should rev slightly further if you do it slowly. then again, mine is clogged differently to yours, not with a silencer, so this may not prove anything if it cuts at the same rpm each time.

i run a 70rs ti. if memory serves me correct, it will NOT hit vtec with the silencer installed.

so yeh, get the silencer out is my advice. as for damaging your car, i've spoken to a few people about it as i had to put the clogged-up stock exhaust on for a couple of days when i was clearing epa. they reckon it won't damage the car at all, i am also of the opinion that it won't damage the car at all as it reved freely so long as i didn't try and hit vtec. but it's pointless as the car is worthless without the top third of it's rev range :P.

Hmm.. i read up on s2ki to see if anyone else ran a 70rs with the silencer they said there was no issue with preventing vtec engaging.

I did try to rev up to it slowly but it seems it cuts off at the same revs (6k rpm just before vtec).

Anyway thanks for the advice. I will be trying to take out the silencer once the exhaust is nice and hot hopefully the metal would have expanded enough to be able to yank it out this time.

And yeah I am still kinda of the cynical opinion that it MAY damage the car so I'm going to try get that bastard of a silencer out ASAP.

This makes me wonder however - why would a tuning company such as Js racing even offer a silencer for retail if it DOES damage the engine when installed? I'm sure there is a reason behind it.....

EDIT: there has also been suggestions that using a slide hammer works pretty well? This is probably going to be my last resort lol