91dirtydiesel
Dunce
Is 3" striaght pipe large enough for a turbo engine? How much space is in a 3" pipe compared to 5"? My 3" feells like its holding me back, like its just all back pressure ? I've got 5" on the way so hopefully that frees it up
exhaust flow
- Thread starter 91dirtydiesel
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Ididriver
Full Access Member
i think 5 is a bit over kill.
4 should do just fine.
4 should do just fine.
Silver Burner
Burnin' Oil&Rubber
I doubt a 3" is too small on a 7.3 IDI turbo... You're probably still only making 200HP or so. Seems like the 3" downpipe is where any restriction would be.
Ididriver
Full Access Member
3in downpipe is about as big of a downpipe you can fit in these trucks.
91dirtydiesel
Dunce
ok thats mainly what i wanted to know, if it was making more exhaust the the full 3 inch could handle. I already ordered the 5" from mbrp so it will have to do
Black dawg
Registered User
going from 3" straight pipe to 4" on my truck was very noticeable.
flareside_thun
Reviving The General Tao
I wonder is 3 inch off the manifolds on an NA motor would be overkill?
93cc7.3
needs turbo power
i wonder also if running up pipes on a custom turbo app bigger than 2.5 would have a negative return if wrapped
Compu Doc
Full Access Member
I am running 3" off the manifolds on an NA but remember to use a muffler and not straight pipe it. The best muffler to use would be a straight through muffler.
flareside_thun
Reviving The General Tao
Well that messes up my plans...guess I'll just go 2 1/2 merged into 3 then stepped up to 4 and then into 5.
429idi
Full Access Member
Just based on area of the pipe.......
for 3"~ 7.07in^2
for 5"~ 19.63in^2
for 4"~ 12.57in^2
The 5" would flow almost 3 times what the 3" would.
for 3"~ 7.07in^2
for 5"~ 19.63in^2
for 4"~ 12.57in^2
The 5" would flow almost 3 times what the 3" would.
Brianedwardss
Registered User
4" is as big as any IDI will ever need. Heck powerstroke guys know that anything under 500 hp only needs a 4". But, there is a noticeable difference between 3" & 4" systems, especially while under load and/or going up a long hill.
The only thing a 5" system gives you over a 4" when making less than 500 hp is a much deeper tone. Still, if you've got the funds, there's no drawbacks of a 5", just be sure to post some pics!
The only thing a 5" system gives you over a 4" when making less than 500 hp is a much deeper tone. Still, if you've got the funds, there's no drawbacks of a 5", just be sure to post some pics!
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Brianedwardss
Registered User
And you can see that a 4" flows almost Double that of a 3".
The difference between 3 & 4" is a greater percentage than 4 & 5".
icanfixall
Official GMM hand model
If the original poster is running a turbo then a 4 inch straight pipe without a muffler is as big as you need. A 5 inch off the end of the down pipe will be a tuff fit. My 4 inch just fits but its close to the E4OD trans. Then the over the axle is another close fit.
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