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- Aug 25, 2007
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T9S1i asks this question in the Turbo system tech forum:
Danny you don't necessarily have to use a 4" intake pipe just because your compressor inlet is 4". Take a look around on the other forums like evolutionm.net and srtforums. You'll find pics that look like this one on evom:
AMS 3076R Kit Evo IX Dyno Results. - evolutionm.net
This guy JohnEB took some great pictures of his AMS turbo kit. The pic you want - scroll about 1/3 of the way down the page, it's the picture just below the one that says "Cosworth Power to Pass". It shows the intake pipe and turbo assembled. This is a GT3076 (4" inlet) and you can clearly see that the intake pipe is a bunch smaller, probably 3", and it connects to the compressor inlet with a 3" to 4" silicone reducer hose.
There is a reason why this is ok. Turbos like the GT3076 and the Borg Warner S256 have a 4" inlet because the outer part of the inlet is taken up by the anti-surge ports. The actual compressor inlet is only about 3" in diameter, or even less. The anti-surge ports don't have to have air blasting at them from the intake pipe. In fact, when the anti-surge ports are doing their thing, they are actually letting air OUT of the compressor (flowing backwards). Here is a good diagram with words to explain what this is for:
TurboByGarrett.com - Turbo Tech103
Scroll again about 1/3 of the way down the page to Fig 2. Their words actually don't explain it very well but the diagram is good. The explanation is that surge happens when the airflow over the inducer blades becomes disrupted and turbulent. This is aerodynamic "stall" just like when your airplane stalls because you are going too slow. When that happens in an airplane you get a lot of buffeting. The buffeting in the compressor inducer is called "surge". If you can speed up the airflow through the inducer you can prevent buffeting. The compressor WANTs to pull more air in, it just can't because it's got nowhere to put it when your engine is sleeping at 3000 rpm or whatever (whenever your running conditions put you to the left of the surgeline on the compressor map). But with the anti-surge ports there it's got someplace to put it, it just blows some air back out through the ports. Or something like that. Maybe an aerodynamicist specializing in leading edge slat design would have a slightly different take on this, hey?
So there you have it. By the way, the reason you aren't likely to find fancy setups like this on DSMs is because the big-name tuners don't make these high-buck kits for our old cars.
But you'll find this stuff on the late model cars like evos and SRT-4's.
Gary
Danny you don't necessarily have to use a 4" intake pipe just because your compressor inlet is 4". Take a look around on the other forums like evolutionm.net and srtforums. You'll find pics that look like this one on evom:
AMS 3076R Kit Evo IX Dyno Results. - evolutionm.net
This guy JohnEB took some great pictures of his AMS turbo kit. The pic you want - scroll about 1/3 of the way down the page, it's the picture just below the one that says "Cosworth Power to Pass". It shows the intake pipe and turbo assembled. This is a GT3076 (4" inlet) and you can clearly see that the intake pipe is a bunch smaller, probably 3", and it connects to the compressor inlet with a 3" to 4" silicone reducer hose.
There is a reason why this is ok. Turbos like the GT3076 and the Borg Warner S256 have a 4" inlet because the outer part of the inlet is taken up by the anti-surge ports. The actual compressor inlet is only about 3" in diameter, or even less. The anti-surge ports don't have to have air blasting at them from the intake pipe. In fact, when the anti-surge ports are doing their thing, they are actually letting air OUT of the compressor (flowing backwards). Here is a good diagram with words to explain what this is for:
TurboByGarrett.com - Turbo Tech103
Scroll again about 1/3 of the way down the page to Fig 2. Their words actually don't explain it very well but the diagram is good. The explanation is that surge happens when the airflow over the inducer blades becomes disrupted and turbulent. This is aerodynamic "stall" just like when your airplane stalls because you are going too slow. When that happens in an airplane you get a lot of buffeting. The buffeting in the compressor inducer is called "surge". If you can speed up the airflow through the inducer you can prevent buffeting. The compressor WANTs to pull more air in, it just can't because it's got nowhere to put it when your engine is sleeping at 3000 rpm or whatever (whenever your running conditions put you to the left of the surgeline on the compressor map). But with the anti-surge ports there it's got someplace to put it, it just blows some air back out through the ports. Or something like that. Maybe an aerodynamicist specializing in leading edge slat design would have a slightly different take on this, hey?
So there you have it. By the way, the reason you aren't likely to find fancy setups like this on DSMs is because the big-name tuners don't make these high-buck kits for our old cars.
But you'll find this stuff on the late model cars like evos and SRT-4's. Gary
since the 3" performs about the same.
I bet they don't even have a picture. What really turned me off was when I asked, can't remember his name, but the guy I got on the phone, about clearance between the O2 housing/wastegate to the oil filter he said "Oh they don't even come close". I know that's not right and I tried to explain to him my car is a 1990 with the sideways air-cooled oil filter that comes very close to the O2 housing, but he didn't get it. I know the exhaust manifold has to be designed from the ground up with that clearance in mind, because the manifold determines the position of the turbo. I decided if I go this route I will probably buy the manifold from Shearer Fab and I will talk to Ron Shearer on the phone about it and ask him to make the O2 housing as well - everything to fit the 1990 DSM. I know he will do it right - but there you go it's a custom job. I've asked AMS for custom work before and they said, "Sorry, we don't have time". A local shop here (Speedware) told me AMS is very busy with "manufacturing" these days. Yeah. Manufacturing stuff for EVOS. 
