Intake Pipe Sizing

LiquidX · Jun 2, 2010

Honestly, which is better.

I know people will say 4" over 3" just due to size.

I have a HX40 which has a 4" inlet but my IC piping is all 2.5". Will using a 4" pipe yeild better airflow results over the 3" piping? The pipe in question is the Dejon Powerhouse 4" and 3" intake pipe.

The turbo can suck in a lot of air, but ultimatly the restriction would be the IC piping so let me know if it's worth it getting 4" over 3".

Thanks

2slow4utsi · Jun 2, 2010

I'm actually wondering the same exact thing as I have the same turbo.

pboglio · Jun 2, 2010

If your intake is 2.5", it would difficult to transition to 4" compressor inlet without losing horsepower. Switch to a 4" intake pipe and you should be fine. As an example, I switched from a 4" intake pipe back to a 3" and picked up ~16 h.p. and almost 2 lb/min on my 16g. The transition was so turbulent that it was hurting topend power and airflow. Smooth flow is critical, not just pipe size.

LiquidX · Jun 2, 2010

The filter is 4", the compressor inlet is 4". Will 3" or 4" (diameter through whole pipe) be better or won't there be any real issue between the two?

I only stated the intercooler pipe size because that would become the first restriction.

1995gsx20g · Jun 2, 2010

I wouldn't think of your ic piping as a restriction on the same level as an intake restriction due to the ic pipes being pressurized.
im pretty sure the dynamics between changes(such as restrictions) is much different between air under vacuum and pressure.

LiquidX · Jun 2, 2010

So does anyone else have an idea if 3" would be sufficient or should I just get a 4" pipe?

Jimmer307 · Jun 2, 2010

You are asking which would be better for a turbo with a 4" inlet, a 3" pipe or 4" pipe. The obvious answer is a 4" pipe. If everything is a smooth transition in the intake tract than you will have NO restrictions, but the compressor housing itself. That is exactly what pboglio is saying.

I mean sure a 3" will do, but IMO a 4" would be a lot better.

habitatguy187 · Jun 2, 2010

You want to try and match your intake pipe to the compressor inlet, with the least bends/curves in the intake pipe as possible. And get a BIG airfilter - http://www.dsmtuners.com/forums/bolt-tech/153744-air-filter-pressure-drop-results.html

LiquidX · Jun 2, 2010

Thanks for the info.

I guess I'll go with the 4" Dejon intake then when the time comes. I already planned on using a large filter and I'll be making an air box and the ducting into the box from the front bumper.

I'll have to price around at having a custom pipe made as well.

dsmtbopwr · Jun 14, 2010

LiQUiDx said:
Thanks for the info.

I guess I'll go with the 4" Dejon intake then when the time comes. I already planned on using a large filter and I'll be making an air box and the ducting into the box from the front bumper.

I'll have to price around at having a custom pipe made as well.

I'm curious on how the dejon 4" intake fits with these holsets. Have you put it on yet? If so how does it fit? Any pics?

I just ordered the same intake since force performance was out of stock for another week.

Get us a update if you can!

gixrman · Jun 14, 2010

Think about a vacuum cleaner becuase that all a turbo is, your sucking in hugh amounts of air and forcing it somewhere else. Turn on your vac. with no hose, no restriction, now with a hose the same size as the inlet, pretty much the same, now put a smaller hose on there and you can hear the vacuum work harder to suck in that air. Now for shits and gigals strape on a velocity stack and go get a flow meter....
Eohippus :: Home

LiquidX · Jun 14, 2010

dsmtbopwr said:
I'm curious on how the dejon 4" intake fits with these holsets. Have you put it on yet? If so how does it fit? Any pics?

I just ordered the same intake since force performance was out of stock for another week.

Get us a update if you can!

How about you give us an update as I don't even have the intake ordered, let alone have my car back yet

Gixrman
The point was already taken a while ago. I had a chance for a 3" pipe for a quarter of the price of the 4" pipe and that was the reason for asking. I didn't want to bring the cost into the thread because then people would most likely start saying to go with the cheap one.

Hubbard 0 · Jun 14, 2010

dsmtbopwr said:
I'm curious on how the dejon 4" intake fits with these holsets. Have you put it on yet? If so how does it fit? Any pics?

I just ordered the same intake since force performance was out of stock for another week.

Get us a update if you can!

FP is out of stock on their intakes again?

I ordered mine probably a month or two ago and had to wait a couple weeks while they made the recirculated intake for me.

andy4g63 · Jun 14, 2010

LiQUiDx said:
How about you give us an update as I don't even have the intake ordered, let alone have my car back yet

QUOTE]

Dejon 4" intake pipe, fits very well on thais turbo...
I had it with FP mani and Dejon intake and after that with ERL mani + custom CAI added to the Dejon 4" intake pipe.. Fits perfect... For some pics and ideas look here:http://www.dsmtuners.com/forums/bol...reduce-ait-log-info-inside-cai-installed.html

Also I don't think your 2.5" intercooler pipe will be restriction in any way... Because inlet diameter right at the end of comp. housing is not greater than ID of 2.5"piping...

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Intake Pipe Sizing

LiquidX

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pboglio

LiquidX

1995gsx20g

LiquidX

Jimmer307

habitatguy187

LiquidX

dsmtbopwr

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LiquidX

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