ok, ive got 4.6L have stock exhaust, with the vortech v3 strim s/c. my tuner says if i put some headers on my car that he will need to re-tune it, or it should be re-tuned,he says. Is that true ?

 

Should be retuned. With American Racing headers I think you can go without a tune, but you'll want it for power anyways.

With LTs you'll run a lower boost, but with the same power at that lower boost. (Boost is a measurement of pressure, so a free-er flowing exhaust makes the pressure less). So for that reason you'll need a tune.

 

I was told by Tim Barth that as long as the CEL doesn't come on, there is no reason for a re-tune unless you just want to see your new numbers.

 

With a blower, I would get a tune. N/A, it would be nice but not absolutely needed.

 

I would get a new tune...your car will top end pretty hard with the long tubes. Sucks to have to drop another 300-400 on a new tune just for adding long tubes. If you could add fuel to your tune through your handheld than bump it against a wideband and go from there.

 

The only reason to even bother is if the headers you're using are going to move the front O2 sensor. It doesn't matter if it makes it closer to the head or further from it, you'll need to have the O2 sensor delay updated for best performance if it gets moved. From what I know of EEC-V tuning, it doesn't really matter except in regular driving. In open loop (WOT) the ECU figures fuel and timing based on load (MAF signal) and AFAIK it disregards the O2's. O2's are used during cruise and idle though and you may see drivability issues if you don't have the appropriate tune update done.

FWIW, S197's are pretty touchy about changes. The exhaust side is still less important but you might as well. It's a change they don't even need to put it on the dyno for. He can use a fuggin' tape measure and a calculator.

 

But he's running boost so with LTs the boost will drop and therefore change all of the other mapping...

So i still say tune it and be safe.

 

LT's do not drop boost in my experience. Only cams, heads, intake and intercooling. Get thee to a tuner-eee

 

I've heard that you'll drop boost when running LT's from serveral people. Maybe that wasn't true though....

 

Boost is a measure of intake manifold restriction. Nothing else.

Apart from the 10 or so degrees of possible overlap from aftermarket cams which could help scavenging and reduce boost by an undetectable amount there is nothing on the exhaust side that represents an intake path restriction and no way for longtubes to make it any different.

The intake manifold, cylinder heads, boost cooling system and camshaft profile have everything to do with how much boost you make. Exhaust has nothing to do with it.

You were taking dolts seriously. Snicker.

 

Well I appreciate that insight.

 

No matter if it changes boost pressure or not I would get a re-tune. Longtubes will lean out the a/f and that is something I would be concerned about on a blower car. If you just had bolt ons and were adding longtubes I would agree and say it's not necessary but anything that changes the a/f ratio on a blower car I would want to have re-tuned. I would think your tuner should give you a cheaper price to have it re-tuned so for peace of mine I say get it done!

 

Ok, I shall have it retuned. thanks