Pros and Cons for having Downpipe on 2020 Supra

[psimzia]

Hello everyone,
I am from NJ, I am thinking of installing Downpipe on my MKV5, and install better air filter and tubing for better air flow and performance. I have no plans on Tuning my Supra yet for 2 yrs. in. My questions are :-
- is it going to increase HP without Tune?
- am I looking for any issues down the road by installing Downpipe ( need your suggestions pros & cons) ?
- am I going to get Ckeck Engine Light ?
- What grade Gas should be used every fill up (93, 97, or 98)

Thank you.

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[cutsman]

Things will vary depending on if you are going catted or catless, but for the most part:

1. Yes, it will likely increase HP a bit, but it will not be a day/night difference. A tune is what will make the most noticeable difference
2. Depends on your state's emissions laws. With a downpipe, the exhaust gets louder and smellier. This may be a pro or con.
3. With catless, it is very likely you will, but again, the tune could also allow for those codes to be bypassed persay. With catted, you have a good chance you wont, but again, I dont think any vendor guarantees you wont get a CEL.
4. A large majority of tunes are applying to 93 octane, but I always heard go with the highest available octane fuel that you are tuned for.

 

[psimzia]

Things will vary depending on if you are going catted or catless, but for the most part:

1. Yes, it will likely increase HP a bit, but it will not be a day/night difference. A tune is what will make the most noticeable difference
2. Depends on your state's emissions laws. With a downpipe, the exhaust gets louder and smellier. This may be a pro or con.
3. With catless, it is very likely you will, but again, the tune could also allow for those codes to be bypassed persay. With catted, you have a good chance you wont, but again, I dont think any vendor guarantees you wont get a CEL.
4. A large majority of tunes are applying to 93 octane, but I always heard go with the highest available octane fuel that you are tuned for.

Thank you very much. What is the difference btw Catless and Catted ? And what is CEL means

 

[Reppunkamui]

Thank you very much. What is the difference btw Catless and Catted ? And what is CEL means

Stock downpipe contains a catalytic converter. This effectively reduces toxic pollutants in exhaust gas. Generally required by law.

Catless downpipe removes this catalytic converter, so illegal for street use.
Catted downpipe replaces the catalytic converter, but typically with higher flow one which may not be as effective as stock.

CEL is Check Engine Light- It can come on when the sensors in the downpipe still detect high toxic pollutants in exhaust gas.

 

[Amfchang]

Catless Downpipe provides more power and sound. Since the cats are gone with this choice, there is less weight and flow restriction. Some might feel there is a slight rasp to catless compared to catted as well.

with our cars, I noticed catted doesn’t make a huge difference in sound and smell. It does cost more due to having a high flow GESI Cat in the Downpipe.

when you have a tuning module like BM3, there are options like cold start removal. I noticed that with catless exhausts, you can do it because cold starts are meant to heat cycle cats in your car. So you wouldn’t have to go through the loud high rpm starts and you can keep a lower volume when starting in the morning or night.

I went with Catless because I didn’t want to pay 1k for a catted downpipe. There’s no point to be “barely legal” and almost as “fast” as the cheaper option. Of course, where I’m from, we don’t have emissions testing as well but if you are going to modify you’re vehicle, it’s better to not stick in between going all out or not. You’ll be in that situation whether you’ll have too much or too little regret with going one way or the other. Also, if smell is a big issue, I’ve heard you can still smell it with catted Downpipe as well. Even if it’s less, I wouldn’t want to pay more for all these “halfway” benefits.
I went with Armytrix Catless Downpipe and they had a Cat simulator which provided no check engine light with the tune. Even Catted Downpipes can cause check engine lights as well. If you do Downpipe, you should just go with a tune or don’t do both because you can revert it back to stock when taking it in for service and your warranty will void regardless if something happens with just the Downpipe installed and it can be linked to it. I was in the same exact situation as you. I noticed slight power gains with just the Downpipe and ran it for a couple weeks without a flash but when I went with bm3, it was a tremendous difference. It’s really fun to adjust burbles, what rpm to let it pop and etc.

Anyways, I would suggest Downpipe + tune or nothing at all until warranty goes cause all of these things can end up happening and interconnecting with each other, leading you to do the choices i gave at the end. For example, you get a Downpipe, even with a spacer or simulator, check engine light can show later on and then you’ll end up getting tune. I’m a warranty freak but honestly, what’s really likely to break in this car later on isn’t even covered with extended warranty right now. I have both.

 

[Axix23]

As far as emissions inspections, if the Inspector places a mirror under the car in which they do, can they even see the catalytic converter this car?

 

[kurumi]

As far as emissions inspections, if the Inspector places a mirror under the car in which they do, can they even see the catalytic converter this car?

If the stock airbox is installed on the car, you can't see the downpipe from the top of the hood. From the bottom of the car, you can see a bit of the downpipe and see the cat. The thing with that is that the OEM cat does look like some of the catted and catless downpipes on the market.

So as long as the inspector doesn't know much about the car and it does pass OBD2 readiness codes, you should be ok. Of course, YMMV.

 

[Axix23]

If the stock airbox is installed on the car, you can't see the downpipe from the top of the hood. From the bottom of the car, you can see a bit of the downpipe and see the cat. The thing with that is that the OEM cat does look like some of the catted and catless downpipes on the market.

So as long as the inspector doesn't know much about the car and it does pass OBD2 readiness codes, you should be ok. Of course, YMMV.

Gotcha. I know the cats on these don’t like your typical large ones like your normal cars.

 

[psimzia]

Stock downpipe contains a catalytic converter. This effectively reduces toxic pollutants in exhaust gas. Generally required by law.

Catless downpipe removes this catalytic converter, so illegal for street use.
Catted downpipe replaces the catalytic converter, but typically with higher flow one which may not be as effective as stock.

CEL is Check Engine Light- It can come on when the sensors in the downpipe still detect high toxic pollutants in exhaust gas.

Thank you soo much. Makes soo much sense.

 

[psimzia]

Catless Downpipe provides more power and sound. Since the cats are gone with this choice, there is less weight and flow restriction. Some might feel there is a slight rasp to catless compared to catted as well.

with our cars, I noticed catted doesn’t make a huge difference in sound and smell. It does cost more due to having a high flow GESI Cat in the Downpipe.

when you have a tuning module like BM3, there are options like cold start removal. I noticed that with catless exhausts, you can do it because cold starts are meant to heat cycle cats in your car. So you wouldn’t have to go through the loud high rpm starts and you can keep a lower volume when starting in the morning or night.

I went with Catless because I didn’t want to pay 1k for a catted downpipe. There’s no point to be “barely legal” and almost as “fast” as the cheaper option. Of course, where I’m from, we don’t have emissions testing as well but if you are going to modify you’re vehicle, it’s better to not stick in between going all out or not. You’ll be in that situation whether you’ll have too much or too little regret with going one way or the other. Also, if smell is a big issue, I’ve heard you can still smell it with catted Downpipe as well. Even if it’s less, I wouldn’t want to pay more for all these “halfway” benefits.
I went with Armytrix Catless Downpipe and they had a Cat simulator which provided no check engine light with the tune. Even Catted Downpipes can cause check engine lights as well. If you do Downpipe, you should just go with a tune or don’t do both because you can revert it back to stock when taking it in for service and your warranty will void regardless if something happens with just the Downpipe installed and it can be linked to it. I was in the same exact situation as you. I noticed slight power gains with just the Downpipe and ran it for a couple weeks without a flash but when I went with bm3, it was a tremendous difference. It’s really fun to adjust burbles, what rpm to let it pop and etc.

Anyways, I would suggest Downpipe + tune or nothing at all until warranty goes cause all of these things can end up happening and interconnecting with each other, leading you to do the choices i gave at the end. For example, you get a Downpipe, even with a spacer or simulator, check engine light can show later on and then you’ll end up getting tune. I’m a warranty freak but honestly, what’s really likely to break in this car later on isn’t even covered with extended warranty right now. I have both.

Thank you soo much. Seems like I would go for Catless with Tune. So, when it’s time for state inspection anything I need to do to pass inspection ?

 

[phm14]

Thank you soo much. Seems like I would go for Catless with Tune. So, when it’s time for state inspection anything I need to do to pass inspection ?

Yes, leave your DP alone.

 

[Tsar]

As far as emissions inspections, if the Inspector places a mirror under the car in which they do, can they even see the catalytic converter this car?

He's from Jersey, all they do during an inspection is plug your car in. If it passes you move forward to the new station where they test your gas cap - if you pass both stations, you get a new sticker. If CEL is on, you automatically fail, no matter what it's for. No one has ever stuck a mirror under my car or done anything else besides what I just described.

 

[Axix23]

That’s awesome bc in Ga they stick a mirror and looking under the car. It’s annoying as hell.

 

[wolf_kyle]

So I live in California, i know its illegal to run a catless downpipe. Ive been on edge wether to get a catless or a highflow downpipe, and of course after downpipe i want to get a tune and thatll void warranty, I just want to get opinions and suggestions.

 

[kona61]

So I live in California, i know its illegal to run a catless downpipe. Ive been on edge wether to get a catless or a highflow downpipe, and of course after downpipe i want to get a tune and thatll void warranty, I just want to get opinions and suggestions.

I’m going catless and going to use an extender to help reduce how often I get a CEL. Frankly, I’d say it’s worth it with or without a tune for the sound and the savings from going without a cat.

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