Turbo outlets: SPD vs AMS

[cwylie]

Anything you think you lost with downpipes is in your head. This isnt a n/a engine where scavenging is important post turbo.

The most efficient turbo exhaust is none. Bigger is always better, post turbo.

You are 100% correct. But when you restriction point is the exhaust housing then putting bigger parts behind that does nothing to help. Its like trying to blow through a straw into a 3 inch exhaust pipe then changing it to a 4 inch exhaust pipe and still using the same straw. You can only fit so much flow through the exhaust housing. I can tell you that putting the stock adapters and downpipes back on 100% increased the low end response. I might have picked up a hair on the top end but its not worth what I lost in responsiveness. They did sound bad ass though.

 

[xrocket21]

You are 100% correct. But when you restriction point is the exhaust housing then putting bigger parts behind that does nothing to help. Its like trying to blow through a straw into a 3 inch exhaust pipe then changing it to a 4 inch exhaust pipe and still using the same straw. You can only fit so much flow through the exhaust housing. I can tell you that putting the stock adapters and downpipes back on 100% increased the low end response. I might have picked up a hair on the top end but its not worth what I lost in responsiveness. They did sound bad ass though.

this literally disagrees with how turbo engines work, but I'm not here to convince you.

edit: you are also looking it it like a static gas and ignoring the fact that it is an expanding gas.

 

[cwylie]

Please explain to me how im wrong. Also how is a gas expanding as it cools? You must know some special physics I dont. Go try to fill up a water bucket from you hose. Now go get a bigger bucket and see if it fills any faster.

 

[xrocket21]

Please explain to me how im wrong. Also how is a gas expanding as it cools? You must know some special physics I dont. Go try to fill up a water bucket from you hose. Now go get a bigger bucket and see if it fills any faster.

I can't even

 

[cwylie]

Youre obviously smarter than me so help me out here.

For the record I have a forged bottom end motor truck running on stock 2018 turbos. I know exactly where the restriction/limit is. I have also owned a 800whp MKIV Supra back in 2002 when that was still at the top of the HP mark for those cars as 1100whp/1200wtq Z06 as well as several other turbos cars so Im very familiar with how turbo motors work.

 

[xrocket21]

Youre obviously smarter than me so help me out here.

For the record I have a forged bottom end motor truck running on stock 2018 turbos. I know exactly where the restriction/limit is. I have also owned a 800whp MKIV Supra back in 2002 when that was still at the top of the HP mark for those cars as 1100whp/1200wtq Z06 as well as several other turbos cars so Im very familiar with how turbo motors work.

I know all about your truck, its amazing, i ****** love it.

I said, "i cant even" because one of the basic principles of a turbo charger is not just the exhaust flow through the turbine, but the expansion of the exhaust gasses that help it spin. its like the difference between air flowing through an engine vs air flowing though an engine and exploding/expanding.

You may have owned all those turbo cars, but that doesn't automatically give you the knowledge of how they work, and making statements like disagreeing that the exhaust gasses aren't expanding show you don't know what you are talking about.

You claim that going back to a small downpipe/adapter gained you back low end simply true on the basis of how a turbocharger works. it isn't possible. It isn't your truck or a car or my opinion or whatever, its the actual theory of turbochargers.

On an N/A engine, no headers/too big headers can gain you top end at the expense of low end torque sue to exhaust scavenging. This is NOT true on a turbo vehicle post turbocharger.

The best exhaust post turbo is NOTHING. After the combustion then exhaust cycles, the gasses are expanding as they pass through the turbine. it is the flow+expansion that drive the turbine. After the turbo you longer have no need for the gasses and the sooner they are out of your way, the better. it isnt as simple as your blowing through a straw analogy because at this point, the gas starts to cool and contract. It is a very one dimensional way of looking at it that way. All that exhaust gas pre turbine is pressurized, and as soon as it exits to atmospheric pressure it can expand and cool.

I dont know, it is tough to explain the whole thing without starting at the beginning, but basically you gotta believe me that the best exhaust post turbo is nothing, and the less restriction you have, the better, and it isnt as simple as looking at it as one tube where the smallest point is your point of restriction, like a weak link in a chain. Along the exhaust path there are different densities, pressures, temperatures, etc that are going on.

 

[cwylie]

When going for all out HP with giant turbos are 100% correct. No exhaust is the best. When you are looking at power under the curve and driveability the exhaust 100% makes a difference. These engines with their small turbos controlled by electronic wastegates are very different than an all out race motor. I have seen a dyno graph of a truck with stock exhaust and adapters vs aftermarket adapters and downpipes and it 100% lost power under the curve. This was with the stock tune. With an aftermarket tune that might have changed but Im not sure. Matt from gearhead is tuning my truck. He has tuned tons of raptor and told me there are gains in cattless downpipe but no gains from adapters. I 100% trust what he said as he has probably done more custom raptor tunes than anyone out there.

 

[xrocket21]

small turbo, big turbo, stock turbo, snowmobile turbo, go kart turbo, etc. It doesnt matter. It is how turbos work.

Different trucks, different days, different dynos, numbers can change.

Smaller exhaust post turbo will never outperform larger exhaust, anywhere along the curve, it simply doesn't work that way.

 

[cwylie]

small turbo, big turbo, stock turbo, snowmobile turbo, go kart turbo, etc. It doesnt matter. It is how turbos work.

Different trucks, different days, different dynos, numbers can change.

Smaller exhaust post turbo will never outperform larger exhaust, anywhere along the curve, it simply doesn't work that way.

Same truck same dyno. I have yet to see a dyno graph that wasn't from the mfg showing any gains. Have you?

 

[cwylie]

Even Cobb will tell you their downpipes didn't make any power.