Is a 3" air intake tube too small?

[jhenegh]

I'm hunting my lost 2-3 mpg that I instantly lost when I installed my intercooler and air filter setup. No, I'm not just hotrodding around now My first thought is that my air filter or tube going to the turbo is too small. I have a 6637 filter with a 3" section of pipe connecting into an 093 turbo. My first thought is is that 3" diameter too small?? The turbo inlet itself is 2.75". I just welded a fitting and installed the the restriction gauge from the stock airbox on the pipe tonight and it stayed in the green zone on the 5 mile test drive at highway speeds

Thanks for any ideas!

 

[riotwarrior]

Try 4" or larger see wth changes

 

[Clb]

I may be off line outta line here,,, the filter does not get any airflow tucked in there in a corner, look at top fuel or any performance induction.
What innercooler?
How smooth are the transitions?
Any extra long runs?
Same fuel?
Any other changes?

 

[F350camper]

I dont think its your new IC setup. Has to be some sort of timing coincidence. You could try just bypassing it for a tank to see. But I think something else is going on.

 

[jaluhn83]

Concur, I do not see a reasonable way simply installing an intercooler would cause that much change.

3" intake should probably be sufficient. I'd personally try for 3.5, but again unlikely to make much difference. Looks like a fairly straight smooth flow as well, aside from the turbo inlet. Air filter is still going to get sufficient flow there to work fine - look at how much open area there is around it. Ideally it would be nice to have it more open, but there's practically issues. Also ideal would be to add a baffle or ducting to make sure it's getting cooler air rather than sucking in hot air from the radiator, but also not a major concern.

If you actually have that big of a mileage difference (that is, it's not a one time fluke caused by over/underfilling the tank, different driving, etc) then it's likely something else significant is going on. Timing seems most likely.

To put it in perspective, I see ~3 mpg difference between running empty and pulling a large 10k trailer.... the small amount of restriction in the intercooler piping isn't going to make near that much difference.

 

[jhenegh]

I have swung from 8.5-14.5 mpg with about 2500 miles on this setup Ranging from towing 15k+ to running empty. The week before the intercooler install and heads got rebuilt I got 16.7mpg and I repeated a lot of that drive this week and got 14.1. I ordered a 4" flex tube to maybe try and I'm going to check my timing again. I thought it was set a 9* before and after but I'll check it and adjust.

Winter fuel is just around the corner, if not already here, so I may not make much true headway for awhile

 

[snicklas]

I agree also. I went out and measured, and the piping on my 6.0 is 3"OD...... Plus, I would think the CAC would affect the EGT more than MPG.....

 

[jhenegh]

Is that your intercooler piping or pre turbo? My IC pipes are 2.25", and the pre turbo is 3".

 

[blackhole]

How thick (stiff) is the hose to the filter? Had an Isuzu with a high profile so to reduce height had to put the oil bath filter on the bulkhead in a lower position. Connected it with what I thought was bull-goose wire reinforced hose-not. Ran fine 'til extra juice was needed and everything went to ****-collapsed.

 

[jhenegh]

Its all 4 ply silicone boots or steel exhaust pipe. Silicone boots are mostly filled with the exhaust pipe they're joining together. I'm pretty sure there is no restriction like that

 

[snicklas]

Is that your intercooler piping or pre turbo? My IC pipes are 2.25", and the pre turbo is 3".

That is all post turbo. The pre-turbo is all hard plastic. I will measure it tonight.....

EDIT: I measured it earlier. The OD of the intake between the filter and the cold "in" on the turbo is 4", as mentioned it is the OD, so I would say it is between 3.5 and 3.75 ID... since the truck is put together and my Daily Driver, is why I have given just the OD's..........