Questions on Proper FMIC Piping Size

[Driftless240]

So once I am set to get my Ka-T put together I am going to be getting custom piping done for the FMIC and am just looking want to find out what you guys think the proper size piping would be, for my application...

When all is said and done, I will have a fully rebuilt S13 Ka24De-T with a Garrett T3/T04E .50/.63 Trim and am looking for 350whp. I am looking for the most responsive set-up that I can...

With the little luck on searching, I am concidering 2.75" Piping?

I read that smaller diameter piping would result in Pressure Drop [2.5"] & Larger piping will result in turbo lag [3.0"+], and I do not want that; thats for sure! So I figure, middle of each would be best?

[Correct me if I am wrong on this, please]

I have also read of people doing different size piping on either side of the FMIC Core; 2.5" Turbo Side. 3" intake Side, reasoning behind it?

Some people will probably be like dude just... dah dah dah, but proper air flow is one of the keys to an engines success/potential; so I would like to make the best of what i have. Thanks.

[GTR PrYdE]

Most ebay kits are around 2" on the hot side, and 2.75-3" on the cold side. This seems to be very adequate for your goals, or goals past 400whp, as the compressor outlet is only 2" on most t3/t4's recommended for out cars. My fmic and piping is like I mentioned, and will be paired with a 57 trim t3/t4.

[Jookmasta]

i run 2.5" all around and i suggest that for your power goals. 2.75" could work also but couplers may work out cheaper since 2.5" is more popular? there was a thread about this a while back with more technical explanations but i think it may not have been archived? anyways, definitely don't go bigger than 2.75".

[WDRacing]

You will see/feel very little difference between 2.5" piping and 3" piping. The volume between the throttle body and turbo outlet will determine the extra lag you will get. So proper routing, clean and smooth transitions with no sharp bends is more of a concern then the size.

As far as proper size goes, you can use the smallest restriction in the equation and assume that is the biggest you'll need to go. In your case it will be the throttle body. Measure the throttle body and use that size, or close to it for the cold pipe. By cold pipe I mean from the FMIC to the throttle body.

If you want the best response then you need to change the hot side of the turbo you chose to a .48 AR. It will still support close to 400 very efficiently and have almost no lag. I have driven similar 240's at the same boost level, one being the .63 the other being the .48, the .48 was a lot funner to drive.

WD

[Driftless240]

Sorry for the lag on response, going through some hard times right now.

WD [or others], can you suggest a turbo of that size? If possible, I would like to stick with Garrett, but if you have any other suggestions, I am open minded. Thank you.

[480sx]

t3/t4 50 trim .63 ar is all you need. Such a sweet street/pump gas turbo. Im loving mine

However like WD mentioned i guess you could go with a .48 housing. I think the .63 housing has great response though. Your call really

[Logan76]

Air is lazy, so as Brian said there is no need to make your piping any larger than your smallest point, to have a smooth consistant flow is better than alot of up's and down's in piping diameter. The only thing I hate is that most IC cores are 3" in/out so then you have to blow cash on reducing couplers, maybe Im just too poor lol.

[WDRacing]

Sorry for the lag on response, going through some hard times right now.

WD [or others], can you suggest a turbo of that size? If possible, I would like to stick with Garrett, but if you have any other suggestions, I am open minded. Thank you.

For the best response go the the T3/TO4E in 50 trim with a .48 AR exhaust housing. That turbo is good to 400whp while still being efficient

It's the one I'd use if I were going with a 20psi or under setup.

WD

[480sx]

Man i cant really see needing the extra response of the .48 ar. The .63 starts to build boost at 2500 and by 3 it near full boost. I cant give you any exacts yet because i havnt driven it enough, but i can say i would definitely not want a smaller exhaust housing. That might be a personal preference thing really..

WD - The cars you drove with the two exhaust housings on them, were they of comparable size to a 50 trim?

[Ballboygordon]

Honestly man, you should take a look at dyno charts of people who have used the .48 a/r and people who have used the .63 a/r. I was having the same dilemma a while back and after lots of time and research I came up with a few conclusions:1. My goal is max 450whp.2. I want full boost slightly after 3000rpm3. I want my power to last until redline.

Once I figured these things out, I realized that the .63 a/r will perform great. It can produce up to 450whp max and power lasts until redline. The .48 a/r should last to redline as far as power, however the power max is more around 400whp and I've even read in other places that it's actually closer to 375 or so depending on the mods you have. The .48 a/r gets full spool somewhere in the 2700 range or so, and it makes torque quicker which makes the car faster, but I am also trying to make my car pass a TX emissions test which might be difficult if boost comes in too early. All in all, I would say to think about your goals as far as max power and power band and look up examples of what people have come up with using those turbos.

Also, as far as an intercooler, I have had an intercooler with 3" inlet and outlet and it had great response. It was one of those cheap ebay ones too the large FMIC kit. Most important thing is to just match an intercooler that fits your power goals.
Modified by Ballboygordon at 8:37 AM 3/4/2008

[WDRacing]

WD - The cars you drove with the two exhaust housings on them, were they of comparable size to a 50 trim?

They were both 50 trim, one was mine with the .63AR and one was AZHitmans with the .48AR. His car was basically in boost all the time...lol. Mine wasn't laggy in my mind, since I've driven drag only setups many times that don't see boost till 4800ish. But it was laggier then the .48AR. His car is making at or around 400 to the wheels. That's crazy power in an S chassis.

The .63 is better for slightly more power, but if your goals are right around 400, the a .48 is the way to go IMHO.

Bruce

I can give you some tips on passing emissions testing if you need. I've had my S14 pass with no cat and stricter standards then TX has by running alcohol and retarding the timing a touch.

Also, if you keep the throttle under 20% you can avoid the load required to make boost.

WD

[480sx]

I like the ablility to stay out of boost, so much better for a daily driver IMO. Your fuel econ goes to sht in boost, and fuels not cheap anymore. Honestly it takes concious effort to stay out of boost with the .63, i could only imagine the battle you would have vs a .48.

I know out where you are you guys are paying through the roof for premium, i stayed in Ca two years ago. Right now in Va were at 3.25 for 93. Its only gona get worse too.. Thats gotta play a factor in your desicion.

Oh and i was playing with my .63 50 trim a bit more today, man im seeing boost at under 2g's WoT. By 2500 im hitting 8-9. I think my BD manifold with its small runners really helps spool up.

[Driftless240]

GUYS!!! I just wanted to thanks for all the post, staying on toic with GREAT detailed explanations on why you suggest what you did.

I like the sounds of a .48, quick responsive fast spooling turbo that fits the cryteria that I am looking for; and if it can truely hold to Redline, that would be perfect!!! I would also imagine the .48 being a little cheaper then the .63 too, which for me is a ++. I am going to be doing alot more looking in to the .48... I still like the idea of a .63 and have seen quite a few of them on sale for a good price lately, some as low as $450.00 for a Garrett. I am going to keep my options open for now, don't want to hop into anything before I am sure it is truely what I want! And seeign that most my time is spent in and on my car.... we want to make sure we get it right the first time!

Thanks again, and feel free to keep the conversations a rolling!