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420A Test Pipe Q&A

I read through the only 4 useful threads before purchasing my test pipe. The information on them seems a little limited, which is surprising since it's a common modification among the 420a cars. So I wanted to make a thread posting some information from my experience with a test pipe, and also give others an place to ask questions about them. Let's get started :)

What is the best brand test pipe?
The only real brand name I saw while shopping was Megan Racing. I saw a few other names that were clearly translated from a different language and likely garbage.

Does a test pipe make your car louder? Yes. Not much louder, but enough for YOU to notice if you started your car before and after installation. And if you have aftermarket cams, it makes the chopping sound a bit more noticeable.

Are test pipes direct fit, or is modification required? If you buy one specifically fit for your car, it will be a direct fit. The exhaust flanges on the test pipe will be the same as the ones on your catalytic convertor. Worst case scenario the one you buy doesn't come with bolts so you'll have to find some exhaust bolts. The only reason you'll need to do any fabrication/modification is if you make one yourself or you buy a cheap one that doesn't fit well.

How much does a test pipe cost? I've seen them as cheap as $25 free shipping. But for the Megan Racing one I purchased, I paid a grand total of $72 (which is still cheap!).

How hard is it to install a test pipe? Installation is fairly easy. It's much easier if you have a lift, but it can be done on jackstands. I did mine on jackstands in 30 minutes. There's 4 bolts holding it to the hanger (2 on either side) and 4 bolts connecting it to the rest of the exhaust piping (2 on each flange).

Why should I buy a more expensive test pipe vs a cheap one? 3 reasons: fitment, material, and warranty. Most of the cheaper Ebay ones do not come with the hanger attachments, which could cause excessive exhaust vibration and even damage your gaskets. They also do not have any sort of warranty, while the MR I purchased came with a 120 day manufacturer warranty.

Is a test pipe lighter than the catalytic convertor? Yes. On the weight scale, my stock catalytic convertor weighed in at 13lbs, while the MR test pipe weighed in at 5lbs.

How much horsepower does a test pipe add? This question can really only be answered with educated guesses and rough estimations. I highly doubt anyone has dyno'd their 2GNT DSM before and after a test pipe install. I'd say a solid guess is 2hp at the top end. Honda's can grab 3-5hp, but the 420a is not as responsive to modifications as Honda engines. Don't get turned away because of this though. When doing an all motor build, every horsepower accounts for something.

Will my car feel faster after installing a test pipe? Likely not. Unless you are extremely sensitive. I noticed no difference at all after installing mine. But that's not to say that there wasn't a difference, it's just a very small one.

Will a test pipe add more power to a turbo 420a than an N/A 420a? Yes. Removing the catalytic convertor from turbocharged vehicles will almost always add more hp than doing so on naturally aspirated engine. Especially if tuned. It allows the exhaust gasses to be pushed out much faster.

Is it illegal to install a test pipe? Yes. It is illegal in most states to tamper with your emissions system in any way, especially deleting components of it. But some states have a rule that cars older than 25 years are not subject to emissions testing. And Alabama (where I live) doesn't do emissions testing or inspections to any vehicles. Just be sure you do your research on your local laws.

There's not a place to install the ground strap on my test pipe. What should I do? If your test pipe has the hangers, place the end of the ground strap between the hanger plate on the test pipe and the hanger itself, then tighten the 2 bolts up. If your test pipe does not have the hanger plates (it should!), then consider having a small metal plate welded to the test pipe where the strap can reach it and tap it to the proper bolt specs. Do not remove your ground strap.

Where is the best place to purchase a test pipe? I purchased my MR test pipe from Ebay. You will always hear me preaching about staying away from Ebay products, but Megan Racing is not an Ebay product. It is a Megan Racing product that happens to be sold on Ebay. Even if you're going to cheap out on one Ebay still seems like the best place to purchase it.

Will my exhaust smell bad after installing a test pipe? It will definitely smell stronger. But not necessarily bad. It's really an opinionated question. If you've been around cars your whole life like I have you'll never even notice it. But if you're super sensitive or never smelled a car without a cat, you'll notice it and might possibly think it smells bad.

Will installing a test pipe make my car shoot flames? No, unless it is already capable of doing so and the only thing holding you back is the catalytic convertor. We could make a separate thread to discuss this. But simply swapping the components on a stock car will bring you nowhere near doing such a thing.

Do I need to buy new gaskets and hardware when purchasing a test pipe? The answer to this question varies based on which test pipe you buy. The MR that I purchased came with both new gaskets and 4 new bolts. If the one you purchase does not come with these, then the answer is yes. Just be sure you research your product before purchasing and also ask the seller questions if you still have any. If your product does not come with hardware, you'll only need to order 2 exhaust bolts/nuts. The stock catalytic convertor has studs on one side and bolts on the other. If you don't break them, you could reuse the 2 bolts & nuts.
Last edited:

Mech Addict

Supporting Member
Jun 9, 2019
Jackson, Wyoming
Nice post. I bought a $29 ebay “performance cat” for me 90gsx. Haven’t installed it yet. My car is engine-unmodded, so not expecting any earthshattering gains, but. Hoping for a little oomph, maybe quicker spool??? (Though basic principles would say not, flow is already low in the low rpm range). I figured for that little money and little risk, why not. I think in Wyoming you get a prize for more emissions, or maybe a tax credit...
Honestly I did debate the pollution thing, but the miles I drive is so low even I can’t see much of an issue, and I’m an environmental engineer.
I plan to swap it in when I swap out my tranny, and I’ll look to add to this thread afterwards.
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