Thanks for positive reviews fellas!

Couple things on combinations with mufflers etc...

1. We optimized the resonance for the stock muffler, so best power happens with it, Akra and others have a different internal volume and change when the waves come back to the head. This can be accommodated for with a slight tune tweak. It's minor but it's there...
2. We are soon to release our 2.5" side pipes with cat or no cat option. We are testing it thoroughly and ensuring we have enough in stock before we announce. This system works in conjunction with a GT3 center muffler either OEM or one of ours (we recommend the quiet for the GT4 unless you really like loud!).
3. Last we have a skunk works project that hopefully I'll be able to reveal at smokies, getting some prototypes made as we speak and if we can pull a rabbit out of our hat will get them on our car before we head out. If we're right about it, will allow power to climb all the way to 8000rpm....

We're making a batch of GT4 headers now (finishing up the orders to ship this week) and will have some in stock for anyone else that's been on the fence...

Jamie

 

 

Will the side pipes and catalysts work with the stock GT4 muffler? Thank you.

 

No CEL? I want headers but do not want software. Can I run these without software and still not get a CEL?

 

I posted on this previously but I have used my car on the street, highway, track and the Smokies all with or without software and no CEL.

 

The long awaited Arrow rods are finally shipped and we even have special Dundon exclusive Cometic MLS head gaskets for both the 4.5L GT4 and the 4.1L GT3...

So we've got a way to do it, but it involves cutting your stock GT4 muffler. Would require Cut and clamp... Not ideal but does allow you to have Cats and Race headers...


No CEL when installed per our instructions and retightened. If they're not installed correctly or if there is an air leak you can get a CEL. Once installed correctly, no CEL and no tune necessary.

AlanC. is OG GT4, had it since the beginning and had our headers shortly after that!

 

Wow 4.5L, what sort of power would you expect ?

 

Yup! Ran the headers w/o tune and stock exhaust for a few weeks, no cel, more hp verified on pre/post dynod. Added the DMS tune later while on the dyno and saw additional hp increase, still no cel.

 

 

I know Alan C has lots of time on his headers with no CEL, but 200 cell CATS are only going to emulate 800 cell cats for so long. If you track your car, the time they function will be less. "Function" means the length of time they have enough umph to do the same number and rate of chemical reactions as the OEMs. Maybe individual cars are different or maybe some of us have different software loads on our ECUs. The way to really tell what is going on is to get an OBDII dongle and look at the O2 sensor voltages before and after headers. Voltages with Fabspeed sport headers are very different compared to OEMs. Right now, even though they are different, I do not have a CEL, but I got one in December and had to put the OEMs back on to pass inspection in January. While I had the headers off I washed them out with lots of dawn and water. Numerous YouTube videos says washing/cleaning does nothing (did it anyway), but something seems to have changed for the better since CEL has not come back.

Also, while I had them off I got a Cerakote ceramic coating done. If you do not have headers yet, and may be tracking your car, I suggest to think about getting a coating to help hold some of the heat in. The OEM headers have substantial heat shielding which these after market headers do not have. I suppose it is possible the coating has caused the CATS to stay hotter which has improved their performance, which in turn is keeping the CEL off. Indeed, if that is the case, washing the cats was a waste of time

 

Dang it this thread is gonna make me spend $$$ money. I have Cobb tune so no cel concerns for me. Will be curious to see power gains with the upcoming catted version vs catless ...

 

Here's a great video from a relative of a guy I work with explaining the power losses in a NASCAR engine. Similar concepts apply to our engines...of the 567 hp lost, about 10% of those losses are categorized as pumping losses (pumping air/fuel in and exhaust out). About 80% of the 10% total pumping loss is due to exhaust. Adding headers reduces pumping losses, thereby putting more power to the crank (as does opening valves). A lot of folks add the GT3 throttle body which provides more air. I suspect this may *increase* intake pumping losses, although that would be a relatively small value (i.e., takes more power to pump more air in, although you've got things like boundary layer aerodynamics coming into play so who knows).

By far the biggest single loss is 185 HP of heat transferred to water and oil.

Geek out on this stuff!

 

Our estimates with cams and custom plenum get it north of 470whp... Will see once it's built...

Cheers

All the headers discussed above are Race headers with no CEL, so cat fouling, life etc... doesn't apply. Glad you were able to clean up your cats. It's likely the heat that is helping, but also if you track the car the heat being held in the cats will also likely kill them...

321SS doesn't hold onto heat the same as 304SS does so coating (especially with removing the largest heat generator, the cats) is helpful but not necessary...



The way we're doing the cats there is no change from our race header dyno's. Since the cats are farther back they're isolated a bit from the power production parts of the system...

Jamie

 

 

Since you anticipate the same power level with both race and catted header, do the differences simply boil down to: the race will be louder and more apt to be held at the consistently higher temps/revs seen on a track, whereas the catted version would be somewhat quieter and able to pass smog?