When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I want to know what would be a good piping size for my 1998 gs400. I want to do a catback , was looking at the one from dna and it says it has 2.75 piping. idc about sound really I just want the best performance . I’ve heard people say even with Borla Exaust they lost a little power and they are the brand I’ve heard about the most at far as the 1998 Gs400 Goes. But if losing power is something that I’ll just have to deal with because I want an exaust then oh well, just let me know though so I know what I’m getting myself in to
so bottom line my question is what is “too big” as I do not want to loose low end or mid end power.And If I do get an exaust that loses power and I also get my car tuned (Apexi Maybe) , will that lost power be regained via tune? I’m a noob I’m sorry.
Couldn’t find anything on the forum about this and I’ve been looking around for about a week. Also I don’t know much about exaust in general so explaining it in terms a 8 year old would understand would be nice, .
Please no “I thinks”. im looking for cold hard facts only, nothing less. Preferably but not exclusive to people who’ve actually owned this car and mod but anything thats facts would help. Thanks
Last edited by Frontage; Jul 14, 2022 at 06:14 PM.
I have a 2000 GS400. Removed single in/single out center resonator and installed a 2.25" X pipe to replace it. Went 2.25" pipe from back side of cat flanges to x pipe, same size pipe back to 12" long glass packs in place of factory resonators, and 71235 Flowmaster Flow F/X rear mufflers with 4" double wall angle cut tips. Looks just like factory, does not drone at highway speeds, and has an excellent tone at WOT that turns heads. No complaints at all after 2 years of daily use.
IMHO anything over that pipe diameter would be excessive and might cause fitment issues around the rear subframe.
Performance gain was NOTABLE right away.
I have used the X pipe mod on my SC430 as well, with noticeable results.
Can get you part numbers on the resonators and X pipe if you want...easy to find on FleaBay or Amazon.
I don't think going to a 2.5" pipe would net you any more performance. The system is only going to be as efficient as its smallest diameter upstream. The 2.25 pipe is almost exactly the same diameter is the catalyst outlets, so that's what I ran with. Local exhaust shop did an awesome job of bending the pipe and installing everything for about $350, and it uses all of the factory hangers!
The mufflers I used have the correct offset to center the rear mufflers in the space, and also puts the tips right in the rear valance cutouts. I didn't have to trim anything.
I will post some pics tonight, driving the SC today and enjoying the 110+ weather here in Tucson...
Too large and you lose low end power and torque as well
@captainva what diameter/specs would be considered just Right for the GS400 ? I was going to order the parts @drc10 sent but if I can get a second voice with other options that would be cool too
2.25" is probably the sweet spot for a GS400 with a for a stock engine and is personally what I would use if it were my vehicle. 2.5" would probably be ok too but that's getting into the too large of diameter IMO. Even 2.25" is too large for a stock GS300
Gs400 exaust mods question
