Whipple with factory exhaust vs headers

[Deleted member 9163]

In discussions with my service advisor about adding headers when I do my supercharger.
Combustion 101 tells me that getting more air in and out quicker makes more power, so I asked him to install LT headers also.
His response is you don't need them as the factory active exhaust is just as efficient and headers would require additional tuning which they can't do.
Doesn't sound right to me. Does anyone have any real data to confirm or rebuke?

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[robvas]

You don't need them.

You could argue that you could damage the stock cats with the blower, though.

You will gain some power with them. Likely 30-40hp depending on what you're making. 600hp car won't gain as much from them as an 800hp car. Most of the 'fast' Whipple S650's have longtubes on them.

 

[Q6543]

1st real mod I did was headers… I do NOT trust on boosted cars.

your dealer sounds like they just do not want to do them.

a local mustang shop to me has installed a few whipple kits… on a car with stock exhaust it dyno’d 727 rwhp (that car had a CF driveshaft)

the one they just did had kooks headers… it dyno’d 778 in worse air…. So the headers were worth roughly 50rwhp.

 

[allenquanobi]

there's numerous discussions about this on mustang6g. I'm gonna combine this discussion about headers with catalytic converters because you cannot really talk about one without the other. Headers you can replace, but most offerings don't allow you to keep the stock cats. You can remove them or go with Green Kooks cats (will discuss this below).

The general consensus is:
If you run boost, keep it civil/tame. No back to back pulls, no 1/2 full WOT, road racing is iffy. If you do, the key is keeping temperatures down and allowing the car to cool down as well as not increasing or decreasing the temperatures drastically too quickly. The whipple tune has COT protection which kicks in around 4 seconds, so it is a safer tune. If you keep it tame and only do spirited driving/daily driving with it, the cats should last a long time (some users report 30k+ miles). Some users sticking with stock everything even make good power (high 600s to high 800s). Again, this is up to the user; you can care about longevity, but you can't care about chasing the highest power number.

Here is where we get to the argument for catless. If you are a person who does a lot of track time/drag strip runs/road racing/full WOT on the highway for a long time/lives in an emissions free state/country: you should go catless. One of the mustang6g's most prolific posters/knowledge ppl (engineermike) has done numerous tests and he concluded that the main weakness of the catalytic converter is thermal shock and they generally are not built for super high temperatures for sustained periods. He ended up retrofitting the GT500 cats onto his stock GT (a lot of work/custom work that may require an exhaust shop depending on your skills). The cons with going catless are the smell and the noise. No cat means no filtering on exhaust gases, so you will get some smell in the cabin. No cat also means no filtering on noise, so your neighbors will hate you (whether you care about this is subjective). And if you do live in emissions testing state, it is a PITA to get stock headers and cats put back on after LTH or aftermarket cats. You also have to play it safe-ish if driving on the street. In the US, it is illegal to drive without catalytic converters. So unless you have a position on every cop in the city or are friends with all of them where they won't arrest you, your time without cats is limited. Pros are you don't have to worry about the cats blowing up at all, you can make more power (debate here as well as some people have tested with cats and made more power than without, engineermike included), it's loud (for people who love loud noise).

Then there is the discussion of aftermarket high flow cats, which is extremely debatable on longevity/strength compared to OEM. many users have kooks headers with cats and have had them fail, while others say it's fine. Again, this can depend on your driving style; however, it's hard to say whether they fail because of that or because they just aren't built up to OEM standards (have to remember that OEM manufacturers go through months if not years of testing in the most arduous conditions possible). There is an argument to be made that the OEM cats are still the strongest compared to any aftermarket brand. The two aftermarket brands that people stand by are GESI and HJS. Let's start with GESI. They are used in Kooks GREEN headers; however, even though they use the gen2 cats (which is good!) these still seem to fail because they use the lower tier version of gen2 cats that support around 750-850 hp (depending on application this may be fine). The strongest gen2 cats support 1200+ hp (supposedly, it's hard to find any real data or anecdotal evidence even because they're pretty new). You can get these cats, but you'd have to find an exhaust shop that is willing to cut out the old cats and weld them on. OR you can use the mak performance pipes (https://www.makperformance.com/2015-2023-Mustang-GT-MAK-Performance-Pipes_p_299.html) that ships with them on. Moving on to HJS, these are accepted as better quality than GESI since they're used in racing applications and in European brands like Audi/Porsche cars which have 700+ hp. These are tougher to use on a GT because they only have pipes for the GT500 or the GT350. You can get the catalytic converters separately, but you have to get them welded on custom. And that's it for aftermarket high flow cats really; everything else ranges from cheap to not strong to straight up trash. This also goes with saying that these two options are expensive.

As with any discussion about forced induction: it's a lengthy debate and a lot of research is needed. Unfortunately, the amount of credible/technical research is way too little for the decisions consumers need to make. Anecdotal evidence is out there; however, what works for one car may not work for your car. Way too many variables come into play (location DA, temperature, customer specific builds, laws). It's hard to make a for sure decision that everyone will be ok with. Hope this helps! I myself am facing a lot of these decisions, but luckily since there is time with the Whipple kit being delayed for where I am, i can do a lot more research about it by asking shops and reading online. About what your service advisor said: he does have an argument that OEM is more efficient than aftermarket. From what i've seen about the aftermarket offerings with cats, you don't need a custom tune stock. I'm not 100% sure how it works for Whipple (i see on their calibration request you can put if you have LTH or exhaust related mods).

 

[allenquanobi]

1st real mod I did was headers… I do NOT trust on boosted cars.

your dealer sounds like they just do not want to do them.

Dealers I've talked to would not install long tube headers since emissions laws in the country have made punishments on installing anything regarding cats very difficult (anecdotal, but have known this to be the case even in states that don't do emissions testing). This can vary from dealer to dealer I assume, but I'd say the safest way to get LTH installed would just be by yourself or finding a mechanic shop to do it for you. If one does get it installed at the dealer, one should get it in writing that it is not illegal and will still be warrantied. Even then, cost of install at the dealership is probably higher than at mechanic shops.

 

[allenquanobi]

You don't need them.

You could argue that you could damage the stock cats with the blower, though.

You will gain some power with them. Likely 30-40hp depending on what you're making. 600hp car won't gain as much from them as an 800hp car. Most of the 'fast' Whipple S650's have longtubes on them.

exactly what I have seen. Unless you're chasing the peak performance, you generally don't need them.

 

[Q6543]

I keep seeing posts online that multiple 24s have had cat failures but never verified information to follow up on.

 

[allenquanobi]

I keep seeing posts online that multiple 24s have had cat failures but never verified information to follow up on.

online is way too anecdotal/subjective to trust. Someone will post about it on any forum, and the immediate assumption is that it applies to every single car. Being that the crowd for sports cars are people who want every ounce of power possible, people will see these posts and assume that LTH is the only way. What I'm gonna go with is that Whipple has done enough testing and tuning to keep a car safe for the street. I say that last part because I know most people who install them are not using them for the street/normal use. They are using it for purposes that Whipple probably did not expect would be the norm. The thing with the 24s is in the past, that was never Whipple's issue because their tunes would usually be replaced by aftermarket tuners where they don't have to share the blame of responsibility. Now though, Whipple is 100% on the hook for any kind of cat failures, which is why I'm assuming that they are taking a very long time to get a CARB certified tune out.

 

[Zig]

His response is you don't need them as the factory active exhaust is just as efficient and headers would require additional tuning which they can't do.

Uh the car is gonna be tuned with the whipple installation.

 

[robvas]

Uh the car is gonna be tuned with the whipple installation.

There's only 1 whipple tune for the 2024's though, right? Or does the Stage 2 kit have a non-CARB tune?

 

[robvas]

What I'm gonna go with is that Whipple has done enough testing and tuning to keep a car safe for the street. I say that last part because I know most people who install them are not using them for the street/normal use. They are using it for purposes that Whipple probably did not expect would be the norm. The thing with the 24s is in the past, that was never Whipple's issue because their tunes would usually be replaced by aftermarket tuners where they don't have to share the blame of responsibility. Now though, Whipple is 100% on the hook for any kind of cat failures, which is why I'm assuming that they are taking a very long time to get a CARB certified tune out.

The previous Roush supercharged (Ford Racing kit) and Whipple kits (again, Ford Racing or Shelby of America installed/warrantied) have cat failures.

What changed for 2024? Are the cats any different?

 

[Zig]

There's only 1 whipple tune for the 2024's though, right? Or does the Stage 2 kit have a non-CARB tune?

Point was they said they couldn’t do lth because they can’t tune the car but will be installing the whipple?

 

[allenquanobi]

The previous Roush supercharged (Ford Racing kit) and Whipple kits (again, Ford Racing or Shelby of America installed/warrantied) have cat failures.

What changed for 2024? Are the cats any different?

nothing has changed. Cats will fail or not. Depends entirely on how you drive and how aggressive you drive. If you want it to last long, then just drive it normally and not like a racer. Or you can take the cats off, but there’s cons to that

You mention the above, but I think you are assuming that all of them fail. It’s always the case that the people who experience something wrong with a product will complain or post the most and loudest. I’d say the majority of boosted cars run fine on stock. If the majority of them failed, these products would not be profitable/still being offered

 

[Deleted member 17846]

You do not need LTH.

I have done it both ways. My Whipple F150 ran the stock cats and I beat on it every day all day with no issues. My Mustang had LTH with aftermarket cats that were garbage. Went cat-less and no problem after.
On the 24 I will keep the stock headers/cats, mainly cause I will make the power I want and keep the car sounding like it does now.

I would say the failure rate of stock cats is low. If I go by with I have seen and experienced aftermarket cats for LTH's fail more than stock cats.

I also would not agree that how you drive will determine your cats life.

The whipple tune is a very safe tune as it leaves a lot on the table when you get custom tune. It is safe for the street and track just as the car was stock.

If you want to make the most power you can then you can add the LTH. You should have them tuned but you can get by without. You will most likely have a CEL unless you can figure out a way to fix it. I wouldn't do it but there are lots that do.

 

[allenquanobi]

You do not need LTH.

I have done it both ways. My Whipple F150 ran the stock cats and I beat on it every day all day with no issues. My Mustang had LTH with aftermarket cats that were garbage. Went cat-less and no problem after.
On the 24 I will keep the stock headers/cats, mainly cause I will make the power I want and keep the car sounding like it does now.

I would say the failure rate of stock cats is low. If I go by with I have seen and experienced aftermarket cats for LTH's fail more than stock cats.

I also would not agree that how you drive will determine your cats life.

The whipple tune is a very safe tune as it leaves a lot on the table when you get custom tune. It is safe for the street and track just as the car was stock.

If you want to make the most power you can then you can add the LTH. You should have them tuned but you can get by without. You will most likely have a CEL unless you can figure out a way to fix it. I wouldn't do it but there are lots that do.

Until someone cracks the ECU, whipple tune will be what everyone is on

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