Twin Scroll Vs Single

[Rolls]

Take into account the GT3076R pumps more air for the same rpm - ie needs ~104000rpm to push 25lb/min at 1.5bar of boost whereas a GT3071R needs ~112000rpm (9% more rpm required than something with 7% more inertia!?!) it stands to reason that in terms of transitional throttle a GT3076R might not be as bad as you'd expect.

It isn't that I'm scared of the 76 being bad, I just want it to be as good as possible, ultimately I'd love to see 280kw with the turbo on full song from 3-3.5k all the way to 7.5k, currently I can't find anything that does that. All the 76 graphs I see vary from 3700-4500 depending on tune and dyno settings. GT28 seems to come on about 3.5k but dives over by 7.5k and doesn't make 280kw unless you run E85 and really really lean on it.

Can anyone think of any turbo/gate/manifold combination that will achieve this?

The reason I want this combo is I want 4k of revs between when the turbo is on full boost and when torque starts to drop off. The only other way to achieve it is to build a motor that will spin to 8k+ everyday, then the gtx76 with external gate will give the same power band, just from 4k upwards. That or build a 30.

Edited June 30, 2011 by Rolls

[black bnr32]

have you thought about a boost controller that has an rpm input? you could increase boost in the upper rpm range to keep power from decreasing.

[Harey]

its a good idea but I think the major problem is a turbo that is super responsive down low and still be able to have boost increased at top rpm. Most turbos that satisfy the response criteria mentioned above are normally maxxed out up top and no boost controller can increase boost if the turbo is maxxed out.

[Rolls]

have you thought about a boost controller that has an rpm input? you could increase boost in the upper rpm range to keep power from decreasing.

If I could safely increase boost in the upper rpm I would also increase it in the midrange.

[DR 32R]

How does everyone think a twin scroll GT3071R would go on an rb25det with the appropriate power, would it come on much sooner than it already does? and if so what about peak power, would it be basically the same?

Would external gate vs internal make much difference? I'm trying to figure out what the ultimate combo for response and around 280kw would be.

You seem obviously in pursuit of the ultimate "response" combo. Is such early and I assume non progressive "response" really be that great to drive in 2 wheel drive? Aren't you just getting early "tail out" via traction loss. A common condition for me in my "responsive" via 4L F6 Ford. On topic I'm trying twin scroll, split manifold, twin gates, with VVT with stall converter to deal with lag in my gt35 based set up ATESSA in my gts4.

Edited July 1, 2011 by WHITE gtt

[black bnr32]

variable valve timing and/or NOS and/or meth?

[Rolls]

You seem obviously in pursuit of the ultimate "response" combo. Is such early and I assume non progressive "response" really be that great to drive in 2 wheel drive? Aren't you just getting early "tail out" via traction loss. A common condition for me in my "responsive" via 4L F6 Ford. On topic I'm trying twin scroll, split manifold, twin gates, with VVT with stall converter to deal with lag in my gt35 based set up ATESSA in my gts4.

For me yes it is great, it is the same reason people buy v8s for that low down massive torque, you are right it probably won't make it faster and might actually make it slower but that is what I want, the fattest biggest torque curve I can attain, but I also want it to hold the torque to redline. It is a street car and I love the brutal smack I get at 3k with my current highflow, however it starts to fall over by 6k, if I could get similar response with it holding to 7.5k, it would feel amazing.

So lithium you never answered, how much difference do you think there would be between the GT3071 and GT3076 in terms of boost, if all things are the same, GTX or GT, twin scroll or normal, how much spool am I going to gain from the GT3071, 100rpm, 500rpm?

I do realise all your points about the 76 making far more power on less boost, holding to higher revs etc, but I still would like to know, as if it is 500rpm, then even if I only make 280kw and having to lean on it very hard eg 20psi+ it is still worth it to me.

Edited July 2, 2011 by Rolls

[Harey]

You seem obviously in pursuit of the ultimate "response" combo. Is such early and I assume non progressive "response" really be that great to drive in 2 wheel drive? Aren't you just getting early "tail out" via traction loss. A common condition for me in my "responsive" via 4L F6 Ford. On topic I'm trying twin scroll, split manifold, twin gates, with VVT with stall converter to deal with lag in my gt35 based set up ATESSA in my gts4.

The key word here is non-progressive. Yes, I would agree that having a lot of low down torque and then it falling away would not be a great result. I believe Rolls is saying great response but progressive torque. The ultimate in my my mind would be flat torque from 3,000rpm to 7500rpm and a peak of 280rwkw on 98.

I have just changed this year from a big laggy turbo to nice super responsive turbo. I love it, I am able to quickly access torque through tight corners and feed the power in progressively when exiting the corner. The only negative is that over 100km/h driving has lost the pull feeling. For a fast street car it is ideal. But it would be great to have this progressive response and then keep pulling all the way to redline.

Regarding the GT35 on the 4L ford engine what rpm does it kick out? I have had a 3.8L engine with a GT35 and it was very taily when the turbo would hit. Is it not just a matter of housing choice? With the 1.06 housing it would hit hard, where as I tried a 0.63 housing and it came in much earlier but was more progressive so traction was not a problem. But the 0.63 fell over massively up top. I think its just a matter of matching the turbo to the engine and getting 'progressive' power delivery.

[discopotato03]

I think some of you people ask for the impossible at times . I highly doubt that a turbo exists that will make significant boost at 3000 revs and still do it at 7500 revs .

The problem is that automotive turbochargers use rotary non constant displacement compressors and their pumping abilities are not linear .

The car manufacturers go to some pretty extreme lengths at times to attempt to have a wide flat torque band but its not endless .

Some of the methods used are about making the engine have good cylinder trapping abilities which generally means some kind of variable valve (cam) timing and sometimes lift as well . In a perfect world we'd have actuators of some kind to give virtually infinite valve timing flexibility .

Take it to the grave , in the world of engineering RB engines are not exactly high tech things and the best of them can only move one cam without lift alterations and whilest ITBs are available they only bolt to RB26's .

None of them have twin scroll or VATN turbochargers and from a competition perspective parallel twin turbos are as good as it gets .

Gearing also has a lot to do with how a car performs and Skylines in some areas could be better . You find if you want to thrash a car everywhere close ratio gears work better but keeping a car on the boil , particularly an at times traction limited one isn't always the fastest way to go .

As per having a 4000 rev flat line full boost maximum torque band , thats just not going to happen .

All engines have a sweet point where volumetric efficiency will be highest and it falls off either side of that point .

This is actually an interesting discussion topic because I think people should worry more about torque than horsepower chiefly because at revs torque can go south with killadorks still climbing .

Its torque that gives you the forced induction shove in the back and when it drops off you pull another gear , ideally you want the rev drop to land the engine at a point where it will pull strongly and accellerate you across the middle of its best average torque range .

Some cars are geared to take advantage of the torque they make in every gear , did someone say RS Evos ?

They may run out of revs at only 230 but they can pull 3rd 4th 5th like it was 2nd 3rd and 4th .

Skylines are geared to be sort of sporty road cars and that big 4th 5th gap is easily felt . How fast is a Skyline geared to go at the redline with a 4.1 diff and a 0.76 5th gear ? If it could get there how long would it take ?

The RS Lancer would not be the gun thing to cruise to Melbourne in and let me tell you close gearing is an awkward PITA round town but thats what it takes to have unholy thrust in every gear .

Its this sort of thing that has the potential to make a car a missile and not need 400 Kws to do it . Getting strong accelleration with production gearing all the way through is a big ask and it needs a LOT of torque to achieve it . Manufacturers put tall gearing in road cars because it makes for relaxed cruising and better fuel consumption . They also set the enines up to make good part throttle torque because thats also needed to pull tallish widish spaced gear ratios .

Its another one of those areas that you can't really have both ways and so the manufacturers build what the market wants which is smooth quiet and economical .

With gearing the zoomers need shortish diff ratios and close tall gearbox ratios which is not difficult in an indirect transmission . Direct boxes like most RWDs have should probably go with a direct 5th because thats strongest and set the diff ratio accordingly . This is something like what the R31 Skylines used when raced here and the trans was actually a Hollinger if memory serves me correctly . It had a splined countershaft so the individual ratios could be changed with the gears fitted casett style . I think Nissans 240RSs were also set up with tallish , for rally , 3.9 diffs too .

A .

[Rolls]

I think some of you people ask for the impossible at times . I highly doubt that a turbo exists that will make significant boost at 3000 revs and still do it at 7500 revs .

Yeah I think 3000rpm is unrealistic, but if you could get something around 3.5k - 7.5k I don't think that is impossible, at least I'd like to know what combination will get as close as possible, whether that is the gt3071 or 76 I'm not sure which would make a better street car.

Edited July 3, 2011 by Rolls

[juggernaut1]

I went from a 3071 to a 3076 52 trim with the same .78 rear twin scroll housing. The 3071 just seemed like it was working a lot harder. The "baby" 3076 feels like its doing the job alot easier pulls earlier too (but there were some exhaust changes). If your going to use a twin scroll ex hsg, the difference between the two in terms of spool will be less pronounced than compared to an open housing.

.

[Psymon]

If I wanted to try a TS rear housing on a 3076, what are my options for housings? Where from etc? I spoked to GCG a while back but they couldn't help.

[raZ1911]

I have seen GTX3071r twin scroll .82 i wonder if the .82 with a RB25 be to small?

[Rolls]

I have seen GTX3071r twin scroll .82 i wonder if the .82 with a RB25 be to small?

No way too small, most people go 0.63 in 71 and 76s

Edited July 7, 2011 by Rolls

[raZ1911]

So with my understanding of twin scroll the .82 would perform like the .63 in response but have more power?

[JonnoHR31]

iirc garrett make a few twin scroll gt30 housings in t3 flange. but the only option for t4 flanged housings is ATP. im running an ATP 1.06 t4 twin scroll v band housing, its an extremely tight fit but works well.

[Psymon]

What's response/power like with the T4 1.06 housing?

[JonnoHR31]

cant really give you a proper answer as i changed housings at the same time as going from 25 to 30det and only got about 300km driving out of it before the motor had some problems which put the car in my garage, where it still sits to this day....

[Rolls]

Johnno is that on a 3L ?

edit: lol how did I miss that, how is the response anyway? what kind rpm does it come on? any dyno? I would have thought 1.06 was big even for a 3L

Edited July 7, 2011 by Rolls

[JonnoHR31]

current 1.06 housing is on a 3l yer. was running a garrett .82 IW housing when i had a 25

from memory (which is very blurred by lots of alcohol since the last time i drove it) it hit 1 bar of boost around 3400-3600 under load (4th gear), but thats with a lot more ignition timing than most people run, which brings boost on sooner time wise but later rpm wise. never had it on the dyno with that setup, do my own tuning so was only gonna chuck it on a dyno once everything was sorted, which hasnt happened yet. imo 1.06 twin scroll is perfect for a 3L, the internal gate .82 was a pretty bad experience for me, all the lag of a gt30 without the power of one due to the restrictive exhaust side.

Edited July 7, 2011 by JonnoHR31