adding fuel w/ hf cats

[no_rulz25]

I will be running 91 cai tune w/ the high flows and Zoomers cat-back, how much fuel should I add?

[fordomatic69]

The posts I read say 3-5%.... try both and compare.

[jackiert]

What? Are we supposed to add fuel when using high-flow cats? Can DiabloSport clarify this please.

[COLD_ZERO]

What? Are we supposed to add fuel when using high-flow cats? Can DiabloSport clarify this please.

Do a search on the site here. You will find that DiabloSport really recommends getting a CRM with a mod like that, but there are posts that say you could add 5 across the board. Especially if you throw heads into the mix next.

[jackiert]

Ok. I did a search and only found a recommendation from Mike to add 5% WOT fuel across the band if using aftermarket headers AND hi-flow cats. I'd still like to know from DiabloSport if adding fuel is needed for hi-flow cats only (no headers). Diablo?

[mikel]

Nah, should not be necessary, BUT, you only know if you have a wideband for sure...

Thanks

[jackiert]

Ok, thanks.

[johan]

Only exhaust mod that really needs more fuel are long tube headers, anything after that does not require fuel added.

[jackiert]

Thank you for clarifying that. Shorties are my next mod and that answered the question for me, thanks.

[no_rulz25]

Only exhaust mod that really needs more fuel are long tube headers, anything after that does not require fuel added.

Thanx guys!!

[Mike_Levy]

Thank you for clarifying that. Shorties are my next mod and that answered the question for me, thanks.

Mind if I ask why? Shorties are a waste. They don't make much more power then stock manis, all of which is on the top end, and you still gotta go through the trouble installing them. If you're gonna bother doing headers, go long tubes or don't bother.

[jackiert]

Thank you for clarifying that. Shorties are my next mod and that answered the question for me, thanks.

Mind if I ask why? Shorties are a waste. They don't make much more power then stock manis, all of which is on the top end, and you still gotta go through the trouble installing them. If you're gonna bother doing headers, go long tubes or don't bother.

That's not true. There are a couple of good reasons I choose to go with Shorts. They do provide significant gains over the stock 5.7s and they don't hang down as low as longs and I like my car to be as low to the ground, without scraping anything, as I can get it. So, after much research and thought, I chose to go shorts, hi-flows, and the cat-back. I've had the last two for sometime, but it's time to get the Gibson Shorties now.

Of course, if you've got some dynograph proof that shorties are a waste of money (for a 5.7), please post them up.

[Mike_Levy]

I've been building motors for a long time and shorties are never worth doing unless there are no long tubes available. Any gains are solely at high rpms, like 4000 and above, and they're minimal. Torque at low and mid rpms will be reduced. The shorter tubes don't allow the velocity to remain high the way long tubes do, which hurts torque production. Thats why you see them on race cars and cars that spend most of their time on the top end of the tach. In that case flow is more important then velocity. Long tubes make power at lower rpms, and scavenge much better, which makes them better for street cars.

Its your car, so you're gonna do what you want. I'm just giving you the scientific info behind headers and why LTs are superior.

[ICEChargerRT]

I have a 2006 Charger with a 5.7 Hemi and have Gibson Shorty Headers, JBA Hi-Flows and Zoomers Cat Back. When I first installed my Headers, I noticed an immediate improvement in low and mid-range torque, not so much in the high range. Granted I didn't have it dyno'ed but thats what I noticed with just the headers. After adding the other two parts, watch out. In California only Shorty headers are legal so that might be an issue for many. By the way this setup Gibson shorties, JBA hi-flows, Zoomers Catback rocks, lots of power, good looks, and sounds really awesome.

[jackiert]

I have a 2006 Charger with a 5.7 Hemi and have Gibson Shorty Headers, JBA Hi-Flows and Zoomers Cat Back. When I first installed my Headers, I noticed an immediate improvement in low and mid-range torque, not so much in the high range. Granted I didn't have it dyno'ed but thats what I noticed with just the headers. After adding the other two parts, watch out. In California only Shorty headers are legal so that might be an issue for many. By the way this setup Gibson shorties, JBA hi-flows, Zoomers Catback rocks, lots of power, good looks, and sounds really awesome.

Thank you for that! I plan on doing the same. I've got JBA hi-flows and a Corsa Cat-Back. All I need now are the Gibson shorties! Your comments on the power you noticed after putting the shorties on is right in-line with just about everyone I've spoken to over the last year that has done the same. Thanks, again.