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Non Member
1514
Tue Apr 12, 2005 12:24 am
Nr Chippenham, Wiltshire
David Gentleman wrote:
Well, no..
Its not like you can play around with it on a rolling road to get the best results, which is the only way you are going to know if the modification actually reaps any benefits..Other than that its just hoping its correct..
When I used to take customers Rover Turbos to my local RR, just setting up the inlet and exhaust cam timing by a couple of degrees either way could increase power by up to 15bhp, and bring the turbo in earlier by altering the exhaust cam..
Remember, on the PRV, we can not play with exhaust and inlet timing independantly which would give you maximum torque and power, as its a SOHC motor. All we can do is advance or retard the whole cam timing..
So as I said, we can't bring the exhaust valve timing in earlier with out advancing the inlet side too..
Non Member
1514
Tue Apr 12, 2005 12:24 am
Nr Chippenham, Wiltshire
David Gentleman wrote:
Depends what the turbos are. Small turbos will spool up quick, but then not give decent top end power. If you find the equivalent match in twin turbos to my GT single turbo, it would be twin T3s with 0.48 housings and 50 trim compressors, which will take longer to spool than my single GT3235X.
It helps low end torque, but not not make a higher torque figure than an unrestricted large turbo setup with minimal exhaust restriction (which is what you would have with smaller turbos to decrease lag)
http://www.nissanperformancemag.com/oct ... ask_sarah/
Basically, as the turbo is fed by a gas pulse at a time from the engine, on a traditional turbo, that one pulse has to fill and travel down the turbo housing in order to spin the turbine wheel. With the twin scroll divided flange setup, the housing is divided into two,
so the pulse (from one cylinder head bank) has to fill a void only half the size of the normal housing, before it hits the turbine wheel thus getting there faster and with more energy..
Non Member
5602
Thu Apr 15, 2004 12:33 pm
Fleet, Hampshire
Non Member
3474
Thu Apr 15, 2004 8:10 am
Colchester, Essex
Stunned Monkey wrote:Hold on, hold on, hold on..... First off, that was my point - that the point to twin turbos is that you have a lower inertia and they spool up faster. The right twin turbos will have no problem shifting the same amount of air as a single large turbo and have the added advantage of being closer to the exhaust valves (on a v engine) and a lower rotational inertia. A *properly set up* twin turbo WILL spool up faster and provide the same power as a single turbo in the same application, all other things being equal. I went on to point out that in the case of the twin turbo I've worked on, and indeed most modern turbo engines is that the turbo is placed on the end of a tight cast manifold so it benefits from the turbulence created in a manifold. This helps with spool time even more (and therefore torque) but hurts top end power. If the turbo is carefully selected for the application (as all should be), you will get the optimum result. As to your specific figures, I'd have to see the data but a pair of T3's is a lot of metal for a 2.5 litre engine to spin!
Not quite sure what you're saying but I disagree that twins will be more restictive - happy to be shown data to the contrary though
Errrrr - really not convinced there either because ti would appear from the article you linked to, that it's all about separating the exhaust outlets on the same bank. Specifically the words "When coupled with a pulse converter manifold" - basically a cheap way of getting close to the effect of equal length headers. You can't really apply that logic to the GTA's engine because you're dealing with two seperate banks that are out of phase anyway, and you aren't doing anything to separate the ports on ecah bank
In a nutshell, you want the pressure differential from turbo inlet to turbo outlet to be as large as possible. But you want the exhaust flow from head to turbo to be as unrestricted as possible (for maximum power). I see what you're saying about the chamber in the turbo inlet, but whether it makes a measurable difference at high rpm's is something I'd have to see figures on.
Non Member
3709
Mon Apr 18, 2005 7:11 am
Alpine France
clee wrote:peterg wrote:T3 sized twin scroll turbo thingamy!
Do you want fries with it sir
Non Member
1514
Tue Apr 12, 2005 12:24 am
Nr Chippenham, Wiltshire
David Gentleman wrote:
As for the pressure differential, you only want the maximum difference to aid spool up, not for maximum power, otherwise we would all run tiny turbine wheel, and have a huge differential. This is why the twin scroll works, as for the inital pulses from the engine on spool up, the pressure against the turbine is high thus making it spool up quickly, but the overall size of both scrolls combined coupled with a larger than normal turbine wheel, means that top end flow and power is not hindered.
Non Member
3474
Thu Apr 15, 2004 8:10 am
Colchester, Essex
Non Member
2501
Wed Apr 14, 2004 10:26 pm
Cumbria
gt5 wrote:i thought you have a stage 2 turbo peter personly i would spend my money else where (head,cams,manifolds)and then change the turbo when it starts to run out of puff well thats my plan anyway
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