H 4" inlet housing vs ordinary 3" inlet housing

Blazer406

Mechanical Engineer
Joined
May 2, 2002
With the possibility of 4" MAF pipes with MAF meter.... it seems I ought to ask..... if the 4" inlet style compressor housing helps.... and if so.... how much?

Obviously... if you put a 3" MAF pipe on a 4" inlet compressor housing... your gains will be compromised.

With the 10 sec capable and quicker 3 bolt turbos.... it seems this would be something worth looking into.....

I am about (I hope) to get my car back on the road... with a TE45A turbo... with the 3" inlet version compressor housing..... with a 3 in TH DP.

The 4" stuff looks mighty unrestrictive compared to the 3" stuff.
 
I was wondering the same thing. But some of the newer turbo's compressor cover are 4"-2.5".
 
Over the years, I have run many different MAF pipe vs compressor cover combinations. Everything from a stock turbo with 3" maf pipe, to my current PT6776RHP with 4" all the way and a stock MAF. Here is the break down. My grey '86 had a stock turbo, then a TE63-1 with Garrett 3" inlet, 2.5" discharge old school cover, then a LT70-1 with 4" inlet 3" discharge, then a PT74 Q-trim with old style H cover and the last upgrade was to build it to GT-Q specs but with same old style H cover 4" inlet, 3" discharge. My white Limited had a TE-45 with TO4E cover 3" inlet, 2" discharge. My current '87 T came with a TA-49, then a TE-60R, then a PT6776S and finally, PT6776RHP. Eight different MAF pipes and I always ran a stock MAF sensor, except for when I was running a FAST system on my old Grey car.


On my old White Limited, I was running a TE-45 with the E compressor cover. (3" inlet, 2" discharge) I ran a 3" MAF pipe for a little bit, until I bit the bullet and bought a chrome 4" MAF pipe from Modern Muscle car and ran the stock MAF. Even with the reducer hoses at the turbo and at the MAF, it helps with spool up and made more power. At the time, not very many people were running 4" maf pipes with stock MAF sensors. That was the setup that I had on that car when it ran an 11.07 @ 120 on 28psi. That car was very simple. It had a stock 75K mile bottom end, ported and polished M&A Stage III aluminum heads with matching intake, Hemco upper plenum, modified stock 62mm t-body, Direct Scan, Scanmaster, fuel system, FM IC, Art Carr 16930 9" non l/u converter, typical suspension parts, 3" exhaust all the way back and C-16 back in '98.

Fast forwarding now.
Recently, while running the 6776S turbo, I had to run the 3" MAF pipe and stock MAF with just a K&N cone attached to it. I could tell just by listening and feel, that the turbo was struggling because of having to suck through such a small setup. So I upgraded to Marks' (Buickgn) 4" MAF pipe and 4" Big Mouth cold air kit. The turbo was allowed to breath a lot easier and the car ran a whole lot smoother and quicker. Just this yesterday, I installed my new turbo and IC and let me tell you, this car is a monster now.
I would recommend to all who are running a turbo that has a 4" inlet, to upgrade their MAF pipe to at least a 3.5" if not a 4" setup, as you will see a gain in spool up and throttle response.
More to come.

Patrick
 
you gotta do something about that tiny MAF......

:)

I agree Bob....

Some old threads resort to the "old school" argument... that Joe Blow ran xx time on a stock mass air meter......so why would you want to run anything else?

I hate that argument. :mad:

From and engineering standpoint, I feel this statement is rediculous..... and has no engineering reason whatsoever.:mad:

These engines are air pumps. Anything you can do to help air coming in or going out IS going to affect the max power you can make.

You ever tried to pump a swimming pool out through a drinking straw?:confused:
 
Fast forwarding now.
Recently, while running the 6776S turbo, I had to run the 3" MAF pipe and stock MAF with just a K&N cone attached to it. I could tell just by listening and feel, that the turbo was struggling because of having to suck through such a small setup. So I upgraded to Marks' (Buickgn) 4" MAF pipe and 4" Big Mouth cold air kit. The turbo was allowed to breath a lot easier and the car ran a whole lot smoother and quicker. Just this yesterday, I installed my new turbo and IC and let me tell you, this car is a monster now.
I would recommend to all who are running a turbo that has a 4" inlet, to upgrade their MAF pipe to at least a 3.5" if not a 4" setup, as you will see a gain in spool up and throttle response.
More to come.

Patrick

At what psi did you feel/hear the turbo having sucking issue?
 
It was typically around 6-10 range when coming up on boost. Not like it was surging or anything, just noticed it slightly. It might have had something to do with the standard actuator I was running as well. I'm sure if I would have installed my 9" converter it would have dramatically helped and I probably would have never noticed. The journal bearing 67 needs a good stall converter.

Yeah, I know about the MAF situation, I'm just not ready to get the 3.5" MAF and T-lator yet. Besides, I know I can reach my goals with a stock MAF. I will say this tho, whenever my stocker finally dies, I will be upgrading. I just gotta be easy on her now with this combo.

Patrick
 
So I upgraded to Marks' (Buickgn) 4" MAF pipe and 4" Big Mouth cold air kit. The turbo was allowed to breath a lot easier and the car ran a whole lot smoother and quicker. Just this yesterday, I installed my new turbo and IC and let me tell you, this car is a monster now.

So with this setup you are still running a stock MAF with 4" pipe and cold air?
 
Absolutely.

This is the setup last week with the 6776S turbo.

DSC00882.jpg
 
Most flow for a Stock M.A.F. Sensor and still filter air.

I hope you gutted that stock maf i.e. both screens, file out the small lip that holds the screens and remove the focuser. If not do so, I was running one that way for years with a TT 93 street chip and no problems what so ever, idle, cruise, full guns, etc. it metered fine but I did have a plastic tube about 4" long on the filter side of the sensor to help straighten the air. Car went 10.15 @ 131 on 21/22 lbs. of boost with a 2/3 flaring trans at the time, Thats why the mph was down for ET.:biggrin:
Burnout below:eek: :D
 
What about taking this one step further.....

Move the MAF to the up pipe... and 4" solid pipe (No MAF Meter) with a 4" filter on the suction side of the turbo.

I assume the chip will need recalibrating for the MAF move.....


I would think ... with positive pressure in the up pipe... that the MAF would be considerably less restriction to the overall scheme.... as compared to the same MAF in the suction side of the turbo....
 
What about taking this one step further.....

Move the MAF to the up pipe... and 4" solid pipe (No MAF Meter) with a 4" filter on the suction side of the turbo.

I assume the chip will need recalibrating for the MAF move.....


I would think ... with positive pressure in the up pipe... that the MAF would be considerably less restriction to the overall scheme.... as compared to the same MAF in the suction side of the turbo....

That's basically what I've been running for a few years, using a 3" LT1 MAF in my frontmount intercooler uppipe in the vertical section by the radiator so the top of the maf is about even with the top of the radiator. I had the 3" maf already and it didn't need any reducer hoses to go into the 3" pipe, but if I were running an extender I would definitely go LS1 or bigger. I just used 4" wirewound ducting to an elbow through the core support behind the headlight, to a cone filter hanging down in front. That way I didn't have to worry about IAC clearance issues. Probably not quite as good flow as a pipe but I figured the 4" would more than make up for it (1.78x cross-section gain, maybe 5% loss from the rough walls compared to smooth, for a net of "only" 73% less restriction) :). Didn't see any difference in the chip tuning but I gained about 1.5-2 psi boost and just noticeable quicker spoolup on a Limit ptrim GT67 plain bearing turbo just from moving the maf and changing the inlet hose from 3" to 4".
 
This is the setup last week with the 6776S turbo.

Just wondering? Why would you have a 4'' after the 3'' MAF? Aren't you loosing air velocity? I have a 4'' tube intake with a 4'' to 3'' cone reducer that speeds up the air then stays the same size 3'' all the way to the turbo. I ran a 6.39 @ 109 with that set up.


Blazer406 I was gonna do the MAF in the up pipe but think about this. If you take a straw and blow into it, it takes more force and psi to blow air then to suck air threw. Just a thought. :)
 
Answer: To get me by for now. Eventually, I will be going with a T-Pro setup and will eliminate the MAF all together.

This has been a very good thread, and what ijames just posted only verifies my same findings from the past when I went from a 3" MAF pipe to a 4" MAF pipe and using the stock MAF sensor. The other thing you have to remember is, I now have a Ported Shroud compressor cover on this new to me PT6776RHP turbo. Some of the airflow is reversed back onto itself to help eliminate surging, and I could only foresee some issues if I would have kept the 3" MAF pipe on the car.

Patrick
 
Answer: To get me by for now. Eventually, I will be going with a T-Pro setup and will eliminate the MAF all together.

This has been a very good thread, and what ijames just posted only verifies my same findings from the past when I went from a 3" MAF pipe to a 4" MAF pipe and using the stock MAF sensor. The other thing you have to remember is, I now have a Ported Shroud compressor cover on this new to me PT6776RHP turbo. Some of the airflow is reversed back onto itself to help eliminate surging, and I could only foresee some issues if I would have kept the 3" MAF pipe on the car.

Patrick

Gotcha Patrick ;)
 
.......Didn't see any difference in the chip tuning but I gained about 1.5-2 psi boost and just noticeable quicker spoolup on a Limit ptrim GT67 plain bearing turbo just from moving the maf and changing the inlet hose from 3" to 4".

Awesome....

Gives me something to try to setup for when my car gets through.....

Get the blow through setup working and a decent tune....with respective changes to suction side piping......record that tune so you can duplicate it at the track....

Then put the regular setup back on.... tune it.... at some point at the track.... swap out... and see... same track... same day.... make sure it is the same boost.....

Cool.

Now... gotta get mine going....
 
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