Waste Gates

[Flash89]

hey guys i was just wondering i have seend a twin high mount manifold with only one pipe for the waste gate. i was just wondering what is the difference in performance with having one wastegate for two turbos to having two wastegates??

[teazn_r33]

i guessing that it elimnates having to control two of them like if one fails

one big 50mm+ would be do the job better than two smaller one

would be harder to controll if you had two of them than say one

[STATUS]

the supra circuit kit from BLITZ has one turbo and twin 47mm gates

[Flash89]

what about the response, does it change with 1 or 2

[mad082]

i can't see how it would alter anything except how much air it can flow. i am assuming you are talking about external gates?

i don't think it could alter response from off boost to on boost since they would both be shut anyway as soon as the boost drops below what they are set at. so when you lift off on gear changes they would both close.

[Beer Baron]

technically 2 smaller gates should be a little more responsive as they are operating smaller, lighter valves but in reality the only reason you'd run twin gates is if there wasn't a suitably sized/priced one for you to run one big one.

[saltbager]

Two wastegate looks bad ass though lol!

[Flash89]

yeah i do mean external. yeah i do reckon 2 wastegates look cool. hehe

[DjeMz]

stupid noob question, but what are the advantages of having an external gate?

[R34GTFOUR]

stupid noob question, but what are the advantages of having an external gate?

generally external gates offer greater flow and thus you get better boost control.

Internal gates can either be overwhelmed and be forced open at high boost levels which would result in a lower boost reading then desired or

when at high revs and high boost they may not be able to flow enough (ie too small) and this would create boost creep and you would have undesired overboost.

Thats why generally over 500hp, you dont really see many internal gates

[R34GTFOUR]

the tt supras jza80s run a single wastegate for both turbos, and with a simple exhasut made up it often makes them overboost cause the wastegate can't keep up with the two turbos. With an aftermarket system, it wouldnt make any difference with twin or single set up, as long as the size was right to handle the flow of the motor and turbo

Edited August 2, 2007 by R34GTFOUR

[AndrewD]

technically 2 smaller gates should be a little more responsive as they are operating smaller, lighter valves but in reality the only reason you'd run twin gates is if there wasn't a suitably sized/priced one for you to run one big one.

Id have to dissagree to everything there except for the cost.

The original poster was considering a twin turbo setup with either one of two wastegates. Aside from the fact you have two wastegates and associated piping thats going to cost you more and theres increased manufacturing complexity, i would say the advantages of running two over one would be:

- You now dont have both manifolds connected! And hence cross flow and increased turbulence is reduced allowing improve flow (as it was intended in the original manifold design) to the turbines

- Response is not neccessarily improved because of the smaller, lighter valves (i.e. less intertia beer baron) but because of the improve flow

- Control is no different as with a normal setup assuming your running a pressure referenced linear diaphram actuator as was the case with the original skyline gtr

Asides from cost, technically two wastegates would be better for a twin turbo setup.

[Flash89]

yeah i am planning on having a 500hp+ on a RB26. so will there be much difference if i was to use 2 wastegates to 1

[Beer Baron]

Id have to dissagree to everything there except for the cost.

The original poster was considering a twin turbo setup with either one of two wastegates. Aside from the fact you have two wastegates and associated piping thats going to cost you more and theres increased manufacturing complexity, i would say the advantages of running two over one would be:

- You now dont have both manifolds connected! And hence cross flow and increased turbulence is reduced allowing improve flow (as it was intended in the original manifold design) to the turbines

- Response is not neccessarily improved because of the smaller, lighter valves (i.e. less intertia beer baron) but because of the improve flow

- Control is no different as with a normal setup assuming your running a pressure referenced linear diaphram actuator as was the case with the original skyline gtr

Asides from cost, technically two wastegates would be better for a twin turbo setup.

that's fine, except that most (all?) twin wastegate manifolds for skyline 6s I have seen run a balance pipe to connect the two manifolds.

with response, I was talking about the response of the wastegates, not boost response or engine response, and two 40mm gates should be more responsive to changes in pressure that say a single 60mm, but again it would not really be enough to be noticeable.

but sure, twin gates is nice, and if you are running twin big turbos then it's the best option for sure. but for a single turbo I would always just run one big, single gate.

[discopotato03]

I think running twin parallel turbos on an I6 and having a "balance tube" between the two manifolds is a stupid thing to do . One of the greatest advantages of having parallel twins is keeping the 123 456 exhaust events seperated . You keep the exhaust "putts" further (engine cycle wise) apart in seperate manifolds so that each cylinder blows down through each turbine housing and the pressure falls in each much faster before the next exhaust event . To be isolated eack turbo or manifold has to have its own wastegate and not share the exhaust pressure rise from the adjacent manifold .

If you cross connect the exhaust manifolds its the same as having a single turbo single scroll turbine housing . This system falls down because since every cylinder is venting into one passage (housing) there never is a low pressure period so you lose a significant amount of exhaust energy merely fighting a path from one end of each manifold leg to the turbine housing . Reversion is another significant negative .

My 2c spent .

[WHITER33GTS-T]

I have twin turbos on my RB25 and am only using 1 x 48mm wastegate. 1 was easier for me as i didnt have much room to fit a second but when i get some more time it will be redesigned so i can run 2

[2rismo]

IMHO there is no one answer to the question of 'what is better, one gate or two?' as each circumstance and engine combo is different.

[180bfj20det]

I think running twin parallel turbos on an I6 and having a "balance tube" between the two manifolds is a stupid thing to do . One of the greatest advantages of having parallel twins is keeping the 123 456 exhaust events seperated . You keep the exhaust "putts" further (engine cycle wise) apart in seperate manifolds so that each cylinder blows down through each turbine housing and the pressure falls in each much faster before the next exhaust event . To be isolated eack turbo or manifold has to have its own wastegate and not share the exhaust pressure rise from the adjacent manifold .

If you cross connect the exhaust manifolds its the same as having a single turbo single scroll turbine housing . This system falls down because since every cylinder is venting into one passage (housing) there never is a low pressure period so you lose a significant amount of exhaust energy merely fighting a path from one end of each manifold leg to the turbine housing . Reversion is another significant negative .

My 2c spent .

Exactly. I am for this very reason designing several prototype manifolds which will use a single twin scroll turbo and not less than two gates. Same reasoning as discos, completely seperating certain exhaust events (in my case 1-4 and 3-4).

Balance tubes or not having a splitter/divider seperating scrolls all the way up to the gate piston negates in almost everyway having a twin scroll system or in the case of a gtr, seperating 123 and 456.

Peace

[discopotato03]

I think that was a typo , (1-4 , 2-3) .

There are some 4cyl twin scroll manifolds with a single wastegate but to have any hope of it working the division has to go all the way to the face of the wastegate valve , even this is not perfect because the divider must not touch the valve or it may not seal shut . If it was me with twins I reckon it'd be hard to resist the temptation to stay with integral wastegates because your getting twice the valve area . Also having the front and rear three cylinders isolated means that turbine inlet pressure will be lower and controlling the gates becomes easier because of it .

Whats a pair of 2530 IW turbos good for on a well set up engine , 600 odd Hp ? Maybe 450-500 if grafted onto an RB25DET ?

Cheers A .

[180bfj20det]

I think that was a typo , (1-4 , 2-3)

Sure was.... As you state above, its 1+4 and 2-3.

Agree with you on the rest.