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I have found measurements for the inlet & outlet diameters of the stock Revup cats, but I need to verify the inlet/outle diameters of the HR or VHR stock cats, and have come up short on my searches. Does anyone know these measurements?
Even if they would bolt up, doubt there are any performance gains unless the cats themselves are different. For example, the Accord/TL cats, cell count is 700 in the catalytic honeycomb, its 500 on the TL-S version. Most aftermarket high flow cats are 200.
Odd the bolt pattern would be different though, Seems like something that wouldn't need to be changed often, if ever.
The purpose of my question is to determine if it would be possible to use the HR oem headers with the Rev up cats, and if there would be a significant loss of flow by doing so. I do not want to do high flow cats or test pipes, due to the increase in sound. However I dont want to eliminate any gains from the headers by choking it off with a more restrictive cat. My thought is that I can purchase the proper flange, cut off the HR flange on the header, and weld on the Revup flange. This would cost about $20. As opposed to buying new HR cats, which are quite expensive even when used.
I realize that the cats are by far the more restrictive component in the system, but I am not a fan of how loud the VQ becomes when the cats are removed, and of a constant CEL.
Perhaps all this will not be worth the effort, but I purchased the HR headers for next to nothing, so Ive got nothing to lose by trying. There must have been some performance gain from the new header design, otherwise Im not sure Nissan would have spent the money to redesign it for the HR.
Feel free to scrutinize/ridicule. 😁
Last edited by Bridgetown; Jul 6, 2020 at 03:45 PM.
I highly doubt they would be anymore restrictive than any other G35/37 converter.
FWIW, my car wasn't appreciably louder with Art Pipes and no CEL. But its not an inexpensive option.
I agree, the Art pipes sound the best. If I had the money I would purchase the Art pipes, or possibly the Ark performance hfc. I just cant justify that amount of money for a bent piece of tubing and a few welds. Also the weak Canadian doesnt help get me any closer 🙄
The purpose of my question is to determine if it would be possible to use the HR oem headers with the Rev up cats, and if there would be a significant loss of flow by doing so. I do not want to do high flow cats or test pipes, due to the increase in sound. However I dont want to eliminate any gains from the headers by choking it off with a more restrictive cat. My thought is that I can purchase the proper flange, cut off the HR flange on the header, and weld on the Revup flange. This would cost about $20. As opposed to buying new HR cats, which are quite expensive even when used.
I realize that the cats are by far the more restrictive component in the system, but I am not a fan of how loud the VQ becomes when the cats are removed, and of a constant CEL.
Perhaps all this will not be worth the effort, but I purchased the HR headers for next to nothing, so Ive got nothing to lose by trying. There must have been some performance gain from the new header design, otherwise Im not sure Nissan would have spent the money to redesign it for the HR.
Feel free to scrutinize/ridicule. 😁
I feel like we've established that the Revup/DE headers have a different flange vs the HR. Did you buy used OEM HR headers?
Everything you discuss seems to be doable. I believe Z1 makes header flanges that might be in line with what you need. The only issue I see is that its a pain to just remove/install Cats on these cars. I've heard headers are an absolute pain. Not to mention, you'll be fabricating and welding (aka installing/removing the exhaust multiple times). If you have the time and patience, go for it. From what I've seen/read online, aftermarket headers only seem to help with higher rpm's. However, I'm not sure how HR headers would fair on DE.
For me, I'd upgrade to hi-flow cats. The cats seem to be the biggest choke point of the exhaust from what I've read, and unless I was racing and needed to squeeze every HP out the car, I think stock headers are fine for a street driven car. Bear in mind, that's my opinion. At the end of the day, its your car, so build it as you wish!!! Life is too short to not do what you like doing.
From what I've seen, typically if the OEM's make a significant change to anything its for a good reason. Maybe they felt that the HR needed equal length exhaust runners to support the higher 7k rev ceiling and/or keep up with the dual intakes
