Wastegate Dumptube Effects on Power

[boosted k20]

so i was tuning a LS/VTEC the other day:

LS/VTEC
B16 head
forged 9:1 CR
eagle rods
ram horn header
2.5" charge pipe
like a 1.5" piping coming out from compressor to intercooler
full 3" exhaust
supposedly a SC61 turbo (looked kinda small to be a precision SC61)

well while tuning this car i had quite a few problems, mainly with boost leaks. first the car was only making like 220 whp on 9 psi. figured out it was a boost leak from the BOV. put a new one in and the car made 275whp. found another boost leak on the TB. fixed that and car made 285whp on 9 psi. turned up the boost to 12 psi and the car made 311whp. turned it up to 15 psi and it was still making the same HP. everytime the boost was increased the fuel and ignition curves were tuned. turned it up to 19 psi and it still was not increasing HP. it never passed 311whp.

im leaning towards more boost leaks. the car had like 2-3 home depot couplers that expanded under boost. plus i dont think the turbo is a true precision SC61. turbo maxing out???

[Sohc_mshue]

Even if the turbo was a little smaller than a sc61 i doubt it would run out of efficiency at only 12psi.

[boosted hybrid]

You have issues elsewhere besides the turbo. If you dont have a dumptube on the car that goes under the oil pan, that could be the one of the issues at hand.

[boosted k20]

hey Jeff, yea the kid does not have a dump tube on his 38mm tial wastegate. he's run n a full race/ neukin style manifold with the wastegate dumping w/o a dump tube.

should i tell the kid to fab up a dumptube that goes under the oil pan?

[turbotegb18c]

You have issues elsewhere besides the turbo. If you dont have a dumptube on the car that goes under the oil pan, that could be the one of the issues at hand.

Hey jeff, can u elaborate on this? I've never heard of this before and have never had problems with no dump tube. Thanks, Paul

[mrx]

Hey jeff, can u elaborate on this? I've never heard of this before and have never had problems with no dump tube. Thanks, Paul

I'am interested in this too...

[boosted k20]

yes yes, i think we would all like to know

[bigwig]

Wastegates expell hot exhaust. Hot exhaust directed right infront of the compressor=increased IATs. Increased IATs=loss of power. Thats the whole story.

[boosted hybrid]

No, egr is the story. If you are discharging hot exhaust gas into the compressor that is one thing, if the discharge is pointed in the complete opposite direction and power loss is severe that is another.

Exhaust gas recirculation kills power. EGR is for emissions purposes on OEM applications. N0x is greatly reduced using EGR, and thus lowers formation for emissions purposes. This also reduces power potential from an engine.

In a forced induction application, the compressor inlet generally sits within the area near the dumptube discharge. With no dumptube, the wastegate exhaust gas discharge is expelled into the area in the engine bay. Even if the discharge is not pointed in the direction of the compressor inlet (i.e wastage discharge pointed downwards on EL manifolds, wastegate discharge pointed towards radiator on log manifolds, etc), the available oxygen content in the engine bay is severly reduced. When you compromise the available oxygen being injested into the engine through the compressor inlet (the only available air source), you lose power. Less oxygen available in the combustion process, less cylinder pressure developed and less torque and power produced.

There has been many customers that come for tuning that have a dumptube, but does not go underneath the oil pan. While on the dyno, the discharge reflects off of the floor of the shop and gets injested into the engine. By simply adding a flexible extension on the dumptube to bring the exhaust gas underneath the car, i have seen gains of anywhere from 10-50whp. I have had multiple customers cars that dont have a dumptube at all, and by adding a dumptube underneath the oil pan have picked up between 20-90whp worth of power.

Here are some examples that i have collected from past tuning sessions:



*This was on an LS engine that had no dumptube. It was using a log manifold, with a tial 38mm gate. The discharge was spraying downwards in the engine bay, with the compressor inlet facing the passenger side. By simply fabricating a dumptube that went underneath the oil pan the gains seen in the dynochart were realized. Solid lines being same psi and tune with just the dumptube added.



*This was on a FR equipped built b16a engine. The FR kits do not come with dumptubes (nor do any other kits out there). The compressor outlet on the 44mm gate was pointed towards the radiator, compressor inlet on drivers side. By rotating the dumptube up towards the ceiling, and adding a 5" extension 90whp worth of power at the same psi level and tune were realized. NO OTHER CHANGES WERE MADE! EGR is very significant.



*This car had a dumptube with a traditional log manifold. It pointed downward and stopped half way down the radiator. By simply adding a 90 extension to the dumptube and pointing the discharge under the oil pan, the gains showed were realized.

I have many more graphs that prove this theory correct. By adding a dumptube that goes under the oil pan, or adding an extension to an existing one power output is dramatically increased. It not only makes more power, but the engines ability to knock is greatly reduced. Its a simple, overlooked item that will make a dramatical power difference.

[Johnmay19]

Great explanation, and something that most don't think about.

[boosted k20]

Jeff you are a genious. that makes a whole word of sense. good stuff! i will post up the results when i redyno this car to see if it changes anything

[Sohc_mshue]

Jeff do you think the power losses from having a dumptube dumped straight down to the floor without a 90* bend would be as noticable if the car was not on the dyno? If the dumptube is long enough that it goes all the way down to the radiator support wouldn't air rushing under the car suck a lot of the exhaust gas from the dumptube out of the engine bay?

[jongearparts]

boosted k20, how did your AF look @ 15 / 19 boost levels.

[boosted k20]

all a/f were from 11.2-11.8

[boosted k20]

Jeff do you think the power losses from having a dumptube dumped straight down to the floor without a 90* bend would be as noticable if the car was not on the dyno? If the dumptube is long enough that it goes all the way down to the radiator support wouldn't air rushing under the car suck a lot of the exhaust gas from the dumptube out of the engine bay?

i was think n the same thing. the air should carry the exhaust gases away from the turbo