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Need some help / info . I have a 2017 q50 red sport , I have the ams ldp and just ordered a cbe from fast intentions. My question is will I have any problems with the dp 3 " going to the 2.5 " cbe . Should I sell my ams ldp to get the 2.5 downpipes from fast Intentions or just stay with the ams 3"
 

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Keep the AMS LDPs. They will bolt up just fine to the FI CBE.
 

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I think the 3" is slightly deeper IMO.
 

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Is there a smooth reducer (transition) at the beginning of the CBE to go from 3" to 2 1/2"? If not, may want to at least think about putting something like that to avoid an abrupt size change at the flange - Longer the better.

Otherwise, would seem that would be too abrupt/sudden of a change in size that could cause internal turbulence of the exhaust flow.

IMO, this is not a wise idea especially considering the compressor (turbo)...Would it wreck it, probably not, but it won't like it, lol.
 

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Discussion Starter #6
Is there a smooth reducer (transition) at the beginning of the CBE to go from 3" to 2 1/2"? If not, may want to at least think about putting something like that to avoid an abrupt size change at the flange - Longer the better.

Otherwise, would seem that would be too abrupt/sudden of a change in size that could cause internal turbulence of the exhaust flow.

IMO, this is not a wise idea especially considering the compressor (turbo)...Would it wreck it, probably not, but it won't like it, lol.
The ams dp come with this plate that converts from a 3" to a 2.5"
 

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Is there a smooth reducer (transition) at the beginning of the CBE to go from 3" to 2 1/2"? If not, may want to at least think about putting something like that to avoid an abrupt size change at the flange - Longer the better.

Otherwise, would seem that would be too abrupt/sudden of a change in size that could cause internal turbulence of the exhaust flow.

IMO, this is not a wise idea especially considering the compressor (turbo)...Would it wreck it, probably not, but it won't like it, lol.
AMS provides a spacer plate that enables it to be bolted up with even a stock CBE. It's not ideal but it works. I sold my AMS LDPs and got the FI for mine when I bought the FI CBE. Necessary? Maybe. Maybe not. You decide.
 

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My question is will I have any problems with the dp 3 " going to the 2.5 " cbe . Should I sell my ams ldp to get the 2.5 downpipes from fast Intentions or just stay with the ams 3"
I would give Kevin @[email protected] INC. a call about the transition. I have the FI 3" Catted DPs and the FI Resonated CBE on my '17 Q60 Red Sport, and my car put up great #'s on the dyno - 437 WHP & 502 WrTQ, so I never had a concern about this subject, nor did FI bring it up when they installed the DPs at their shop (I already had the FI CBE installed).
 
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The ams dp come with this plate that converts from a 3" to a 2.5"
That's the issue, it's a plate, not a true reducer. Basically puts a small wall, if you will, to 'stop' the gasses at that area. Naturally, they will eventually flow out but it's an undesirable disruption at the minimum. Of course it "works", just not close to ideal.

Quick visual on difference between 3" and 2.5" circles, for reference [actual size will vary as tube is OD and not sure on wall thickness either uses, but this diagram is close enough]

95839
 

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I don't like the idea of having an orifice plate as a reducer. I would think going from 3" to 2.5" would create back pressure and affect scavenging of the exhaust gases. That's a 30% reduction in cross-sectional area.
 

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This is cringe worthy:

95845
 

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I don't like the idea of having an orifice plate as a reducer. I would think going from 3" to 2.5" would create back pressure and affect scavenging of the exhaust gases. That's a 30% reduction in cross-sectional area.
I'm also thinking of the turbine wheel on the turbo; that has to has some sort of detrimental effect in the long run. On the lines of possibly harmful backpressure 'waves' against the wheel that it doesn't want or need. The energy transfers somewhere and who knows maybe even cause vibrations, or pressures further down the line...what's connected to the turbine? Yes, the compressor wheel...In between we have our centersection; shaft and bearings, etc...Seals and so on. Maybe taking it a bit extreme here, just saying, why invite potential trouble.

I can't believe this is the shop's solution, err band-aid, to be honest.

Now, in theory, if this orifice (reducer) plate were quite thick, there could at least be a chamfer, or fillet around its circumference or something. That would help. Of course, in the real world it may be silly and quite a piece vs just using a true concentric reducer.
 

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Discussion Starter #13
I'm also thinking of the turbine wheel on the turbo; that has to has some sort of detrimental effect in the long run. On the lines of possibly harmful backpressure 'waves' against the wheel that it doesn't want or need. The energy transfers somewhere and who knows maybe even cause vibrations, or pressures further down the line...what's connected to the turbine? Yes, the compressor wheel...In between we have our centersection; shaft and bearings, etc...Seals and so on. Maybe taking it a bit extreme here, just saying, why invite potential trouble.

I can't believe this is the shop's solution, err band-aid, to be honest.

Now, in theory, if this orifice (reducer) plate were quite thick, there could at least be a chamfer, or fillet around its circumference or something. That would help. Of course, in the real world it may be silly and quite a piece vs just using a true concentric reducer.
Makes total since but why would AMS make a 3" in if there's only like 1 2 cbe that make 3 " . So pretty much everyone say i shouldn't go with the 3" and go with the 2.5"
 

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Makes total since but why would AMS make a 3" in if there's only like 1 2 cbe that make 3 " . So pretty much everyone say i shouldn't go with the 3" and go with the 2.5"
You might check this out:

 

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😂😂 what i don't want, reason I'm waiting for my cbe but the whole corona got backorder . How is it with the dp ? To loud in the morning and how about when your driving ?
It's a bit loud on cold start for 25-30 seconds. Afterwards, it's very nice sounding. On the highway you can't hear it over the tires. I like it.
 

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I have the AMS LDPs and FI CBE with 10" exhaust. I bought the AMS because of the no CEL, fit quality, and their black Friday deal was $330 I believe. Initially I wasnt going to do a CBE because I liked the OEM tips on the RS400 and just would have went with some Frankenstein y-pipe/mide-pipe setup.

Anyways after research FI CBE seemed best option and I went with that. After that I found out they make 2 5" LDPs and probably would have went with that option because I too am not a fan of the 3" to 2.5" downstep.

With that said its not that bad and my car still got a nice a little boost out of it and sounds great.
 

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Discussion Starter #18
I have the AMS LDPs and FI CBE with 10" exhaust. I bought the AMS because of the no CEL, fit quality, and their black Friday deal was $330 I believe. Initially I wasnt going to do a CBE because I liked the OEM tips on the RS400 and just would have went with some Frankenstein y-pipe/mide-pipe setup.

Anyways after research FI CBE seemed best option and I went with that. After that I found out they make 2 5" LDPs and probably would have went with that option because I too am not a fan of the 3" to 2.5" downstep.

With that said its not that bad and my car still got a nice a little boost out of it and sounds great.
Oh snap , how is it with the 10 " . Did you get res or non res on the x pipe ?
 

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Oh snap , how is it with the 10 " . Did you get res or non res on the x pipe ?
10" is loud but not obnoxious and quiets down once warmed up. It sounds really good when you step on it and during downshifts in sport mode. A good amount of this noise could be attributed to my AMS LDPs as well. I went non-res because I only drive short distances and wouldnt be too bothered with drone. There really isnt any drone driving around town and is only noticable on the highway at 78+ mph when you are on the gas trying to keep it at speed at about 2k rpm.
 
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