Official silicone coupler sizing thread.

90 GSX · Sep 10, 2006

EDIT: For anybody that searches for coupler sizing....

The 2g mas is a 3.75" coupler. A 3.5" fits but it's a very tight fit. The 4" is too large. The circumference of the 2g mas is 11.8", do the calculation yourself if you want, but 3.75" is the correct size.

The 16g inlet is 2.25" without the black rubber spacer, and 2.5 with the spacer. Either one will work.

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The third commandment... thou shalt not post information on this forum when you have never done it yourself and obviously don't know what you are talking about.

:beatentodeath:

Fin

RotaryRyan · Sep 10, 2006

The 2g MAS takes a 4 inch coupler. You may have been able to squeeze a 3.5 inch, but why else would FP sell a 4 inch coupler with their intake?

http://linux.forcedperformance.net/merchant2/merchant.mv?Screen=PROD&Store_Code=FP&Product_Code=FPAIP&Category_Code=DSM-Intake

I have had 3 different couplers on my 2g MAS, all were 4 inch except when I ordered an intake from Dejon, they sent a 3.75 inch coupler which was a little tight on the 2g MAS. I don't see how you fit a 3.5 inch on there.

DSMcamaro · Sep 10, 2006

the 3" GM mas requires 3.2" couplers.
http://www.slowboyracing.com/more.php?id=1721&

RotaryRyan · Sep 10, 2006

DSMcamaro said:
the 3" GM mas requires 3.2" couplers.
http://www.slowboyracing.com/more.php?id=1721&

I don't think he was saying anything about a GM MAF. Just the stock DSM 2g MAS.

chicagoavenger · Sep 10, 2006

so is it 3.5 or 4"? :confused:

DSMcamaro · Sep 10, 2006

RotaryRyan said:
I don't think he was saying anything about a GM MAF. Just the stock DSM 2g MAS.

Please note the thread title and the fact that he also talks about a 16G turbo. and the 3" GM mas is another common couple size that people get wrong by trying to fit a 3" on it.

MyBeatGSX · Sep 10, 2006

I love this thread, the overall idea is brilliant. Let me quote you (with a modification) to show my support of your efforts...

The FIRST commandment... thou shalt not post information on this forum when you have never done it yourself and obviously don't know what you are talking about.

chicagoavenger · Oct 22, 2006

90 GSX said:
After seeing people say that the outlet on the 2g mas is 4" and that the 16g inlet is 2.75 I'd like to correct the problem so that people don't buy expensive silicone couplers to put their new intake system and have them be the wrong size (ie me).

The first commandment, a 2g mas needs a 3.5" coupler, I repeat 3.5", not 4", not 3.75", 3.5" no more no less.

The second commandment, a 16g inlet needs a 2.5" coupler, not a 2.75", not a 3", not a 2.25", not a 2.2945, a 2.5" coupler. An evo3 will be a tight fit but 2.37" will still be to big.

The third commandment... thou shalt not post information on this forum when you have never done it yourself and obviously don't know what you are talking about.

Just wanted to say thanks. I bought a 3.5" coupler and it fits nice and snug. A 4" may work but the 3.5" is perfect and I'm glad I got the 3.5" and not the 4" :thumb:

GVR4592 · Oct 22, 2006

How did you get a 3.5" coupler on the 2g mas? I just installed the FP intake on a 2g and used a 4" coupler, it fits perfectly. The inlet of the 16g's is 2.25", I have one sitting on my shelf and a 2.25" coupler fits it perfectly, if you put a 2.5" on there it would be way too loose.

I'm changing your first commandment: Thou shalt not post measurements when you can't read a tape measure.

GVR4592 · Oct 22, 2006

Here's the compressor inlet of a busted big 16g, notice how 2.5" is way to big for the inlet?

92awddsm · Oct 22, 2006

90 GSX said:
After seeing people say that the outlet on the 2g mas is 4" and that the 16g inlet is 2.75 I'd like to correct the problem so that people don't buy expensive silicone couplers to put their new intake system and have them be the wrong size (ie me).

Just for future reference, you could have figured this out before wasting $ on couplers. Measure the circumference of the outlet and then divide that # by 3.14 (pi) and it will give you the diameter of the coupler needed. This also applies to the inlet, whether it is square, oval, or rectangular shaped.

2bclutch · Oct 23, 2006

GVR4592 is 100% correct. A 16G inlet requires a 2".. trust me.

92awddsm · Oct 23, 2006

2bclutch said:
GVR4592 is 100% correct. A 16G inlet requires a 2".. trust me.

Its 2.25".

90 GSX · Nov 19, 2006

I'm telling people what I did to make it work, plain and simple. I made this post to clarify the BS in other posts that led me astray, and you have come back to reinforce the same BS numbers that I just said did not work. And if you know anything about science, you would know that you should expect the unexpected. Taking a measurement is not enough to get a definitive answer. You have to take into account the lip on the turbo inlet, the rubber ring, variations in coupler sizes etc. etc. You can trust your ever so accurate tape measure, I'll trust my experience.

You may be right that a 2.25" coupler would fit on a 16g but a 2.5" coupler fits better, especially with the rubber ring around the inlet. If you don't believe me try it yourself. I'd like to see you get a 2.25" coupler around an evo3, silicon multi ply couplers don't stretch very easily. Lastly, I don't care what FP sells with their kits, or whether they say it's 4" or not. If it fits on the 2g mas, it is NOT a 4" coupler and there's nothing you could say or do to convince me otherwise because I've seen it, felt it, smelled it, etc. and I know that the 2g mas doesn't use a 4" coupler. In fact, it is significantly oversized. Why don't you bust out that tape measure of yours and measure that coupler. I'm willing to bet that never even measured it, you probably just got it from FP and read that it was 4". FP is not omniscient and I won't treat them as such. Everybody on this forum posts up that the 2g mas needs a 4" coupler, but how come chicagoavenger used a 3.5" and it fit perfectly? I'd be willing to bet that half of those people have never seen a 2g mas hooked up to an intake pipe other than when they were browsing the FP website or they were just quoting BS they read in another post... By the way FP has awesome products, but apparently their numbers are a little off.

Knowing that C=piD is not the problem. I probably would have measured it first but 2 things prevented me from doing that: 1) I was out of town when i ordered the couplers and 2) 80 bazillion board members said that the inlet is 2.75" and the 2g mas is 4". But you are right on one thing, it was my bad for not confirming the sizes myself, I'll give you that, but I still believe that simply measuring may not be enough to get the perfect coupler in many cases.

Lastly, I'd be hypocritical to say that you should trust my numbers over any other board member, but I've already had 2 people confirm those sizes so you can make the decision for yourself. Maybe try both... whatever pumps your rump.

GVR4592 · Nov 19, 2006

My picture doesn't seem to be working but it was pretty obvious there is no way a 2.5" coupler would fit and seal properly on the 16g inlet. It measures 2.25", what's going to fill in the .5" gap? The FP 4" intake and 2g mas take a 4" coupler, I installed one the day before you started this thread and I used a 4" coupler from the local diesel supply shop, not from FP. I'm not quoting any BS, I installed these parts, and I know what couplers I bought. I measured the couplers, and they weren't 3.5" or 2.5", they were 2.25" and 4".

I don't have the FP intake with me to take more pictures but I do have the 16g and a 2.25"-2.5" reducer. I'll take pics of the coupler showing the 2.25" measurement of the reducer and how it fits perfectly on the 16g. I'll take a picture of the 2.5" side of the coupler and show that there is a large gap. I should have the pics up shortly.

GVR4592 · Nov 19, 2006

The pictures aren't that great but you can clearly see the measurements.

Here's the inlet of the 16g