mudgudgeon
Resident galah
Yeah, factory installed restriction right there! I think it was done for emissions or noise reduction? Makes no sense though.
its definitely tight for 3" pipe, but I've done it a couple of times now
2.5" vs 3" exhaust... any benefit to the bigger size? (1 Viewer)
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Yeah, factory installed restriction right there! I think it was done for emissions or noise reduction? Makes no sense though.
its definitely tight for 3" pipe, but I've done it a couple of times now
3" pipe is not going to fit without lift. Biggest pipe the exhaust shop could fit was 2 1/4 no lift.
mudgudgeon
Resident galah
Find another exhaust shop.
TuffMudder
Still working on my FJ55!
Ok, I'm fairly ignorant when it comes to exhausts, but something about this confuses me. I have 1hdt and I believe it has a 2 1/2 inch intake. If that's correct, how does a 3" exhaust help behind a 2 1/2" choke point?
Well this is an over simplification but you are completely disregarding combustion.
In a diesel the complete combustion is:
4 C12H23 + 71 O2 --> 48 CO2 + 46 H20
Where you have 4 very dense tightly packed molecules and 71 compressed oxygen molecules being broken apart giving off energy and combining to create 94 much less dense molecules that take up more space. You also have a turbo on most diesels that you want to relieve the backpressure in the exhaust so that the turbo can spin more freely.
In a diesel the complete combustion is:
4 C12H23 + 71 O2 --> 48 CO2 + 46 H20
Where you have 4 very dense tightly packed molecules and 71 compressed oxygen molecules being broken apart giving off energy and combining to create 94 much less dense molecules that take up more space. You also have a turbo on most diesels that you want to relieve the backpressure in the exhaust so that the turbo can spin more freely.
TuffMudder
Still working on my FJ55!
Thanks for the explanation! I'm getting a custom air box and adding an Intercooler to try to lower egt’s. Looks like I might need to consider a three inch exhaust as well
mudgudgeon
Resident galah
On both my diesel landcruisers, I have used a 4"dump pipe, then 3" exhaust.
My thoughts being that a 4" dump acts as an expansion chamber, eliminates back pressure completely so the turbo spools freely. Even if it is an effect that works for only a few seconds, it can still make a difference in driveability.
The exhaust cools, and condenses as it travels through the system, so for me 3" seemed more than adequate. Most people tell me the 4"dump is over kill, but anecdotally, it seems to work well.
One of the things with an exhaust system that regularly gets left hanging, is eliminating as many bends as possible. Toyota sure left a bunch of low hanging ripe fruit here.
Check out my pics in my 105 project thread for an exhaust systems that could be almost identical in a diesel 80 series, largely the same for a petrol 80.
Tightest bends in the system are in the 4"dump at 75°. The rest are generally no more than 45°.
Good free unrestricted gas flow, and quiet!
My thoughts being that a 4" dump acts as an expansion chamber, eliminates back pressure completely so the turbo spools freely. Even if it is an effect that works for only a few seconds, it can still make a difference in driveability.
The exhaust cools, and condenses as it travels through the system, so for me 3" seemed more than adequate. Most people tell me the 4"dump is over kill, but anecdotally, it seems to work well.
One of the things with an exhaust system that regularly gets left hanging, is eliminating as many bends as possible. Toyota sure left a bunch of low hanging ripe fruit here.
Check out my pics in my 105 project thread for an exhaust systems that could be almost identical in a diesel 80 series, largely the same for a petrol 80.
Tightest bends in the system are in the 4"dump at 75°. The rest are generally no more than 45°.
Good free unrestricted gas flow, and quiet!
jfz80
Cruisin’
I would not bother for the 3" but i would run it over the frame rail again. Every time.
It will fit but that was one of the shortest lived mods on my truck. You'd have had to been around a bit to understand the weight of saying i "upgraded" to the EMS setup lol. It was on a SC'd rig and did perk it up but went back for a resonator on the second day and was still not enough. Long distance from muffler plus 3" provides a bit of trumpeting effect. Apparently the next owner thought the same thing
Madisonr34 3" fits fine, its just a pain to wrestle esp with crush bends.
It will fit but that was one of the shortest lived mods on my truck. You'd have had to been around a bit to understand the weight of saying i "upgraded" to the EMS setup lol. It was on a SC'd rig and did perk it up but went back for a resonator on the second day and was still not enough. Long distance from muffler plus 3" provides a bit of trumpeting effect. Apparently the next owner thought the same thing
Madisonr34 3" fits fine, its just a pain to wrestle esp with crush bends.
Thanks for this... I thought I had a crushed exhaust pipe, but something told me to check Ih8hmud to verify
