Full exhaust (Headers & Catback) with no tune

[G37Sam]

What are your thoughts on running a full exhaust setup without touching the tune? Would it be unsafe/hurt the engine's reliability (from running too lean?)

I'm not open to fiddling with my ECU just yet here in Dubai.

[Steve M]

People did it before HPTuners and the Arrow PCM were around, and their cars ran just fine. The headers will lean it out some, but the stock tune commands so much fuel that you won't even come close to running too lean. The biggest issue you might have is throwing codes, especially related to the cats.

[lochnessmonster]

Unfortunately, I don't know enough about the Viper to weigh in too much, having only owned the car for a couple of months. But I will say this, I wouldn't dream of doing it on my STi without a tune. You tune for every single modification you make to that car (intake/exhaust), or you wind up with a destroyed engine. Of course, the two are night and day in so many ways, but my Subie has taught me that a professional tune with the modification gets the most out of the mod anyway. When you go spending a bunch of cash on a mod, and then don't get the engine tuned for the mod, you are leaving a bunch of hp/tq on the table, in addition to the very real possibility that the air/fuel mixture under certain conditions will result in engine damage. I have personally done a massive amount of modifications to my STi, and just had my tuner, Airboy, in Calgary, send revised maps to me via e-mail as attachments. I go out, data log the new mod under very light driving conditions, and then send him the results so he can make the necessary changes. Slowly but surely we work our way up to WOT 4th gear pulls. I have an Innovate AFR gage that I installed in the car to do this, and monitor the tune. I'm sure Steve M is correct, in that you aren't risking any damage, but if you want piece of mind, you might consider installing an AFR gage so you can rest easy. I don't know if "long distance tuning" is possible with the Viper, but it has worked out awesome for me and the Subie.

[Bruce]

Since there's no change to the way air and fuel gets into the engine, the change to the exhaust side (headers and cats) should not harm the engine as even though back pressure will reduce, the air fuel ratio wouldn't change much and the stock tune is rich enough to more than compensate for that. A different story if you were to change the intake or port the heads, etc. Loading a HPT tune can be done anywhere in the world as it is done w/ a laptop and tunes can be downloaded via email, so what's the issue of being in Dubai?

[Jack B]

Exactly, there will be no issues, dozens of cars changed the exhaust prior to hpt and had no issues



Since there's no change to the way air and fuel gets into the engine, the change to the exhaust side (headers and cats) should not harm the engine as even though back pressure will reduce, the air fuel ratio wouldn't change much and the stock tune is rich enough to more than compensate for that. A different story if you were to change the intake or port the heads, etc. Loading a HPT tune can be done anywhere in the world as it is done w/ a laptop and tunes can be downloaded via email, so what's the issue of being in Dubai?

[G37Sam]

@Steve: I plan on running non foulers, should solve the CEL issues

@lochnessmonster: On a forced induction motor, I wouldn't dare changing a bolt without a retune. My previous G37 had an RB motor in it and it spent more time on the dyno than on the road haha. The Viper however runs low compression from the factory and a hell of a rich tune. Might put her on a dyno anyways just to see if she's running too lean.

@Bruce & Jack B: the reduced back pressure on the exhaust should help get more air into the engine I believe which ultimately causes a slight lean out. Not open to e-tunes just yet and the whole idle re-learn at the dealer.

[Dman]

The catback is certainly no issue regardless. The headers and hiflow cats did cause a CEL on my, after clearing the codes, it did reset after a track day of driving. I'd say the car runs much crisper and smooth with the tune no doubt. Not to put words in his mouth at all, but I can say after talking with Lou Belanger for 40 mins on the topic, and he's certainly one of the best experts we have IMO, running his exhaust without a tune won't hurt the engine. CELs can happen "rarely"' like mine from long bouts of super soft driving, or in my cars case, we believe from being shipped, it idled for a very long time, but it's clear able with a cheap scanner and then driving the car. Although personally I recommend a tune based on how it made my car feel, regardless of power gains, the car feels totally different/better.

[lochnessmonster]

All good info. Definitely, the FI aspect of the Subie makes it worlds apart from the Viper. No engine damage, cool.

Now, onto the other issues, what kind of gains have people reported with the addition of headers and a catback without a tune? And, what kind of gains have they reported with a tune?

I know on the Subie, a good tune alone, without any modifications, is going to give some pretty good gains. By the sounds of it, if the Viper runs rich with the stock tune, (i.e. 9-10's AFR at WOT), there is power there to be gained.

Lastly, if he were to put on the headers and catback without a tune, what CEL's might he encounter? Is this only likely if he does a cat delete? And, does this result in a "limp mode" until the CEL is cleared, so he better have a scanner handy to clear the codes or the fun is over for a while?

[mjorgensen]

All good info. Definitely, the FI aspect of the Subie makes it worlds apart from the Viper. No engine damage, cool.

Now, onto the other issues, what kind of gains have people reported with the addition of headers and a catback without a tune? And, what kind of gains have they reported with a tune?

I know on the Subie, a good tune alone, without any modifications, is going to give some pretty good gains. By the sounds of it, if the Viper runs rich with the stock tune, (i.e. 9-10's AFR at WOT), there is power there to be gained.

Lastly, if he were to put on the headers and catback without a tune, what CEL's might he encounter? Is this only likely if he does a cat delete? And, does this result in a "limp mode" until the CEL is cleared, so he better have a scanner handy to clear the codes or the fun is over for a while?

CEL's are very rare with Belanger's and HF cats on the GenV stock PCM, if you run cat-less then you will have a CEL. We installed and sold more than 40 sets of Belanger's for the GenV before there was a tuning solution and they all ran better than stock with no chance of a lean condition on the stock tune.

[lochnessmonster]

Sounds good. Thanx Mark.

[Dman]

All good info. Definitely, the FI aspect of the Subie makes it worlds apart from the Viper. No engine damage, cool.

Now, onto the other issues, what kind of gains have people reported with the addition of headers and a catback without a tune? And, what kind of gains have they reported with a tune?

I know on the Subie, a good tune alone, without any modifications, is going to give some pretty good gains. By the sounds of it, if the Viper runs rich with the stock tune, (i.e. 9-10's AFR at WOT), there is power there to be gained.

Lastly, if he were to put on the headers and catback without a tune, what CEL's might he encounter? Is this only likely if he does a cat delete? And, does this result in a "limp mode" until the CEL is cleared, so he better have a scanner handy to clear the codes or the fun is over for a while?

Up to 50+ for HP increase, another 5-25 with a tune, cars are a little different, but exhaust and tune generally about 60 at the wheels + or -

If you get a CEL, which is rare, I believe it's what I got, a bank efficiency code, which is both clearable with a scanner and can clear itself. No limp mode or drama. Just the light.

[lochnessmonster]

The gains from headers and catback alone are amazing on this car. I'm used to 25-30. Sweet.