My 300rwkw Adventures

[The Mafia]

ok, sorry about lack of appearance - I'll try and answer most of your questions:

Hey Mafia, 300rwkw sounds very nice!!

Ive got a Bosch 044 intank in my 95 S1.5 R33, yes they are noisy, they whine but only really noticeable when idling or your out of the car. . .

The 044 is intank and was reccomended to me and installed by Hyperdrive Motor Sport (WA), the difference between the 040/044 is in the pickup style and outlets + terminals.

basically the R33 tank does not have a flat bottom and the 040 has a mesh bottom inlet whereas the 044 has a thread so you can attach the standard sock and get the correct pickup height. which means you can use the whole tank as with an 040 you MAY get surge issues at a low tank lvl,

if you rubber mount it it should quieten it down a lot i reckon!!

good luck

Thank you very much mate, I appreciate your help and will look into it. I think I might just get the 044 to be safe.

Very interesting read.

Just a few questions,

what size tyres do you run? What diff gears? Would like to know rpm rather than speed.

Your car is manual right?

Do you plan on taking it to the drag strip? It would be interesting to see what trap speed you end up with. I would estimate 123mph with a weight of 1450kg including driver.

Congrats on tuning it yourself as well. I do the same on my car and it is great to see other people doing the same.

ok

1. Tyres are 18 inch, 235 wide, 40 profile

2. Standard Diff Gears

3. Yes I do, as soon as I sort out the fueling issue

4. Thanks man, appreciate it. It feels good to know that I did this all myself.

Aren't you worried about the water washing the oil off the bores and causing excess wear and tear? Especially pushing a stock bottom end to 300rwkw.

lol, first time I have heard this. Did you see a few posts back about how much water is actually going in? Also, water can't wash oil away. Fuel is worse for this. The water and methanol is actually better for your engine.

1. The water retards the burn, and slows it down, allowing the burn to push the piston for a longer period of time, supressing detonation.

2. The methanol drops inlet temps by about 15 degrees.

Hey mafia, wondering if you could recommend any changes to this combo to suit an rb30, only hoping to make the same power, or a little less, but without the WI(its a friends car and he doesn't have the $$$)How much do you think the WI gained you in KW?

RB30 -

1. GT35 - 0.82a\r rear. Not sure on the rest of the turbo. Depends how much power you want. That setup should have a RB30 on boost before 3900rpm, and you won't notice the lag due to the extra bottom end torque.

2. WMI - Get the boost cooler kit, and run that same nozzle as me. Run a 375ml min nozzle then go back to a 225 ml min, and see if it pings or changes at all. I did this, and didn't have to touch the tune so the 225 was plenty. There are calculators that can help you with this on the snow performance website.

Water injection I reckon gave me anywhere between 20rwkw and 40rwkw. I was able to add 12 advance to full load. Thats a f**king lot of timing. Before the WMI, If I added 1 degree is would ping its ass off.

All this and your not running with splitfires??? I didn't see them mentioned. Does the WMI cooling help to stop the spark from blowing out?

I would have thought splitfires would be a must.

Bl00dy good result though.

Yeah, I'm running splitfires with NGK BKR7E's at a 0.8mm gap. Coppers of course.

Thanks

If you've got more timing up your sleeve then I would be playing with exhaust cam timing to bring the turbo on even sooner and then try to get the timing back in the top end so you end up with the same power but even better response. Or you could just increase the compression - have found that this usually helps if you have an unreactive chamber - as you have.

Dont know about bending rods, as has been said - they are only short little f**kers. But I would definately be monitoring exhaust gas temps will leaning out the mixtures.

I'm attemping a WI install at the moment with an xede - semi closed loop ie feedback from a EGT sensor to determine final water injection amount.

already attempted a gain for the EX cam gear before the WMI. Didn't make much difference. Not sure if it would now either. Care to expand on this? Dale FZ1 also tried and had very little luck for the effort.

What do you mean by "unreactive chamber"?

Apparently these rods are only good for 280rwkw. But I don't think its that. Its the ramp rate of the power that kills them. Think about it. If a rod is moving slowly, and you force huge power upon it, it will bend. If it is moving slowly, and you apply moderately increasing weight on it, it speeds up, and is able to take more once moving at a decent speed.

mafia there are a few good threads on the actual flow rates of walbro's when they are pushed on turbo cars.

the rating of 255L doesn't take into consideration fuel rail pressure plus whatever boost levels you are running. additionally they are rated with 13ish volts so if you are using the standard wiring your pump will be seeing 11 or so volts. you are most likely to be getting a fair bit less than 255L.

I checked my pump, its getting 13.8 volts. Earthed to the chassis, 14.2 volts. Plenty there. The "standard wiring" theory is based on the R32s. In the R33, the Battery is right there (in the boot) with the pump.

About controlling combustion chamber temps not combustion temps ? I must be missing something here .

David Visard did some interesting write ups on water and water/methanol injection . He mentioned that Spearco used to do a sort of programmable type system that only fed the fluid in when the engine was likely to detonate . I have to wonder what distribution between the cylinders would be like even with a fine misting system , multi point would be best but more complex to apply . I think there would be a chance to actually lose some power by injecting water if it wasn't doing anything ie no detonation . Before I go any further if possible its best to find out why your engine is detonating because as I'll show you may find some power lurking behind whatever was causing it .

Only because Dale can't sleep at night : Drum Roll ....................

Twin scroll turbine housings and properly designed pulse divided equal length exhaust manifolds .

Make a pot of coffee because this'll take some time .

I'll start with the exhaust manifold because they get discussed a lot but the people who make or obtain them swear by them .

The reason behind having all the runner lengths the same is that the time it takes the slug of exhaust gas to reach the turbo needs to be the same in the engines sequential order ie 153624 . If you have a manifold with different lengths the short ones take less time for the gas slugs to travel between the exhaust valves and the turbo and vise versa with the longer ones . The best situation is when they are evenly divided so you get a sharp pressure/velocity rise at the turbo followed by a pressure drop then the next cylinders event etc etc . The aim is not to have them overlap when avoidable because a cylinder blowing down into an area of higher than avoidable pressure will lose some of its velocity attempting to overpower the raised pressure in its path . A non divided manifold is not very efficient because it does a good job of tyring to pressurise every other exhaust port . The turbo (turbine) much prefers to have slugs of gas rather than a constant feed so to speak to benefit from the highest pressure/velocity just as the exhaust valves first crack open . With a divided exhaust manifold on an in line six the exhaust ports are grouped together 123 and 456 , with the firing order being 153624 the exhausting cylinders alternate between the front and rear groups in theory timing the gas slugs evenly to the turbos mounting flange . When you have a divided or twin scrol turbine housing you are separating the two groups all the way to the turbine nozzle - actually there are two nozzles . So we get the high pressure/velocity gas slugs evenly time feeding pulses as widely but evenly divided as possible doing the expansion thing into and through the turbine blades . You don't tend to get a cross feed occuring between the parallel nozzles because the exhaust gas finds it difficult to flow backwards through the turbine blades .

There are some important things to understand about divided and undivided turbine housings of the same family and A/R size . If you had for example a .82 A/R divided housing its really more like two .41 A/R housings in a common casting . This is why you need to increase the A/R ratio with divided housings compared to non divided ones because while yes the combined area is similar the same sized engine cylinders have to flow through them and .41 A/R is a bit restrictive .

So ideally the gas slug leaps from the cylinder out of the port and through the split manifold into an area of lowish pressure not losing to much velocity and barrels into the turbine blades via the divided nozzle . The divided housing was say 1.20 A/R giving ~ .60 A/R so again not a lot of velocity robbing restriction in the separated passage .

Wastegating needs to be done properly ie separate gas flow paths from the manifold or turbine housing all the way to the wastegate valve other wise you lose the pulse effect at the turbine .

The properely designed divided system achieves pretty much what twin parallel turbos do , two separated groups of three cylinders pulsing into separate nozzles but this time with one turbine and one compressor . Twin GT28's obviously have their own integral wastegates but the same thing can be achieved with two vent paths and integral flat valves in one turbine housing . Toyota did this with one version of their CT20 turbo on some GT4's , Mazda did it I think on an RX7 Rotary and more recently Subaru have it on some Rexes and Legacy's (JDM USDM Liberty) . I've got some pics of IHI's (MHI) VF36/37/38 and for emissions clean cars they make pretty good torque . Current JDM Legacy GT makes 430 Nm at 2400 rpm from a 2 Litre 4 .

The people that get this system right and tune the engine properly tend to REALLY pull up the bottom end torque and generally make more torque and power everywhere - right throughout the range . They do this with much lower exhaust manifold pressure and EGT and the engine suffers a lot less of a thermal thrashing when worked hard .

At the moment firms in the US like Full Race Motorsport and ATP Turbo can sell you a real GT3071R or GT3076R with a T3 flanged divided housing and FRM (see above) is doing some for the GT3582R AKA GT3540R . Last time I spoke to Brett Lloyd I asked him if Garrett was going to make divided turbine housings for the GT30 and 35 turbine based GT BB turbos and he said no , the high temp resistant iron is difficult to cast reliably so none in the near future . Their loss I reckon because the aftermarket is already modifying workable generally Diesel divided housings and the results speak for themselves . Who would have thought a twin scroll GT3071R could help crank 400 ft/lbs out of an SR20 at 4500 rpm with porting better cams and injectors etc . I think its entirely possible to make an RB25 feel a lot better than they normally do without lifting the engine out of the car . I still think porting and mild cams help a lot but how close to a mild RB30DET can we get the RB25 ?

Night all .

Discopotato - I have looked at this. its interesting, yet expensive. I highly doubt you'd have change from $4,000 after doing this, yet the gains are less than 15%. I'm not entirely impressed on bang for buck. The WMI, only $850 proved its weight in gold.

There are a few dyno plots I have seen on a particular forum that you are also discussing it on, and they have a little more mid range, same top end, and bugger all low down spool. Maybe it was the particular setup on that particular car, but the figures did not impress me against the cost.

I don't mean to rain on your parade, if you were doing a full rebuild an changing the turbo and manifold, and had extra cash to get external gates etc, then it might be feasable.

But for people that don't earn massie amounts of money, this seems to be a very expensive way to do it. And as per Dales post, I doubt this system would allow for leaner mixtures, and more advanced ignition timing. It can't lower Intake temps, or retard the burn of the fuel mixture.

I am keen on Garrets new turbo technology though... The electrical spool up etc... These are looking very interesting indeed.

I think I have covered it all.

Thanks again guys for all your support, I'll grab a Bosch 044, and get her to the strip on friday the 18th, and see what sort of terminal speed it does.

Edited May 11, 2007 by The Mafia

[chris davey]

70 2500

90 3200

100 3450

110 3900

130 4600

150 5300

170 6000

190 6700

This is what I get for a 1:1 gear ratio in 4th, 4.11 diff gears and 235/40/18’s. Does this look about right? So full boost around 3500rpm then? And then slowly goes up from there.

Also here is some comparisons I have done with a mate of mine who runs a gt3076R on a 1jz auto.

Ben Mafia

Power (kw) 304 295

Rpm 6200 6700

Engine 1jz-gte RB25DET

Capacity 2.5L 2.5L

Trans auto manual

Stall converter 2800 n/a

Turbo GT3076R GT3076R

Comp exducer 76 76

Comp trim 52 56

Comp inducer 54.97 57

Turbine inducer ? 60

Turbine trim ? 84

Turbine a/r 0.9 0.63

Turbine exducer 53.6 ?

Boost 23 18

Fuel 100RON 98RON

AFR ? 12.2-12.0 to 13.0 up top

W/I no yes

Other HKS DLI Cam gears

GT3076R CHRA:700177-0011

Neglecting the fact that yours is manual and his is auto with a stally so that will reduce power at the wheels it does seem as though the WI is doing a lot of good. 5psi more with a larger a/r and not too much difference in total power. His car makes 23psi by about 3900rpm so very similar spool up.

[Devils_Advocate21]

I have got to aggree with the twin scroll system, the only downside to this setup is the extreme costs involved, being divided manifold running two wastegates for it and the machining to required to plumb all this into an exhaust pipe, unless it is drag spec related. The benefits would be substantially great as far as i can gather on freshalloy both in power delivery torque and spool up, But unfortunatley if only there was more of a market over here in australia for them the cost is high.

For such older technology im curious to why there is no better market for it yet???

Would be interesting bringing this more into the market for the benefits everyone can grab hold of. Plus there is very limited discussion of these types of setups over here as well

[Dale FZ1]

Split pulse is a good thing. Trouble is the limited commercial availability in the size range required means product knowledge and resulting recognition of the benefits is low. So we see little discussion.

As per previous, it was employed in the 80s on a system engineered for the Falcon. From memory it was claimed at the time that the regular firing intervals of a 6 cylinder lent itself best to exhaust tuning and the split pulse, with the wider intervals of a 4 cylinder offering less technical and practical advantage. Execution of the AIT concept may have moved on, but the idea is still the same. If it was not a low volume/high cost option it would be much smarter to use one. A proper tuned/split manifold is not cheap either.

Toyota has used split pulse/twin scroll turbines on the GT4 Rally Celica, and other models too.

I suspect the difficulty/cost factor in getting the castings right may be a factor in a lack of corporate interest in supplying the general aftermarket, hence the question to Discopotato03. Perhaps IHI, Mitsubishi or Borg Warner have something already on the market in a suitable size for the performance target being discussed?

Edited May 11, 2007 by Dale FZ1

[Devils_Advocate21]

Really dont mean to whore your thread mafia, but dale these castings are available over in the states its just the short availability over here in aus that makes the limiting factor, Imaging the capabilities of this setup with say a twin scroll housing say a/r of .82 (maybe too small) 1.12 T04Z the full function of its capabilities would be able to be made earlier in the peace, rather than how it is now but with the main market of looking at 2.2g US for a twinscroll manifold from full-race say 1500US for the turbo then in aud 600 each wastegate x 2 piping from turbo to cat with full plumb of waste, Say 1000 AUD Although the price we are looking at is upwards of 6.5 G aud already, In the long run it would work extremely well but for price you pay for ultimate power you can do much better with cost wise with just the single waste better manifold and piping say for 4g....

Ive only really seen the benefits in text form of what they have achieved over the US, i could not gain a dyno chart from there system, Part from added benefits of much or as they say "Instant" spool up from there turbos and much beefier torque levels out of them with increase in power..

Wanna sponsor me in this setup id love to try it out, but the added cost factor is extreme, not only that it doesnt yet include dyno time and tuning to gain the full potential of the setup.

[Dale FZ1]

We're on the same page here. Note I used the word "limited". It's not that they're NOT available, but a case of to what extent. The castings are evidently made available by ATP only, so it seems they have done something off their own back. The freshalloy discussions seem to highlight the troubles those blokes are having getting exactly what they want - order a particular housing and another turns up without explanation? Doesn't sound good considering they are living in the land of consumerism let alone here.

My comment was aimed more at the extent to which Garrett, IHI, Mitsubishi, B-W or whoever have focused any efforts at producing (for their own turbochargers) this style of housing for the sizes needed to cater for Mafia's performance targets. I'd like to be able to call my Garrett (or other brand) dealer and order a specific turbocharger, with that specific housing and know they can deliver it in a certain time frame rather than wait on an elastic calendar, with the chance that they will send something with the wrong A/R. It smells of VERY limited production runs of those ATP castings, with most being accounted for very quickly.

Cost-wise I agree. I wonder if someone (Mafia?) could do a direct side by side costing for what he's running, vs the split pulse setup. For me, this is an essential part of the cost:benefit analysis in deciding what to run.

Edited May 12, 2007 by Dale FZ1

[Dale FZ1]

I have to wonder what distribution between the cylinders would be like even with a fine misting system , multi point would be best but more complex to apply . I think there would be a chance to actually lose some power by injecting water if it wasn't doing anything ie no detonation .

The value of using a multi-nozzle WI setup is something that I’ve looked into. There is a system commercially available, which requires something that looks similar to a fuel rail, but carrying individual water nozzles per inlet runner. Done right, it looks GREAT – check the photo of a custom manifold:

Technically it's superior to the single nozzle, so worth investigating. Problems came up in matching water:fuel delivey ratios, in the rated flow delivery of commercially available nozzles, since they need to be 6 times smaller than a single correctly sized nozzle. After a good hunt around, there was one fogger suitable, but at a high cost. Then the issue of fabricating and fitting a water delivery rail, and retaining the nozzles within some bosses welded into the manifold came up, along with a suitable pressure regulator referenced to boost. It was another case of cost:benefit analysis. Is there a significant water mist distribution problem from using a single fogger that justifies the complexity and cost in going for multiple fogger? Perhaps at levels somewhere above Mafia’s it would be important – 700hp plus? Fuel flow rates at that output would make it easier to match the fogger size. Just an idea.

Proper knock events cause quiet severe spiking in cylinder pressures, nothing like the almost linear rise that adding more fuel brings ( through boost, better efficiency etc) This is why, im a big believer that as long as a motor doesn’t det, you can take a particular combo a LONG way. You better believe the BIG power stock motors you see around have very good tuning, and never det. Its why I believe, all things being equal, Mafia’s motor will live for ever in this state, and will not bend a rod. ( slong as that lecky water pump never dies)

Det being an “explosion†is an interesting term. What’s classed as an “explosion†any way. When is a super rapid burn (and resultant increase in pressure from expansion) an explosion?

I would think its purely a pressure difference over an area or time .. hrmm.

As for WI being an “add on†as Dale and Disco have mentioned, its like saying a correctly shaped head design (that tries to prevent hot spots) being a tacked on design consideration!

Disco talks like WI is there to cure a det issue only, and that really, something like split pulse m.fold should net better over results. I would like to think one could use ALL of these things in an effort to make power, as they are all effecting very different parts of the combustion or fuel -> torque process.

Me thinks, you spend all this cash on good components, to help you rev, move air and make power.. but for fear of detonation, you strengthen components to crazy levels (copper head gaskets?!?) and then retard ignition and over fuel up top to stop it from exploding…

With knock, I use the word "explosion" as a best-fit option. To me, it signifies the lack of CONTROL of the combustion event. Like you say, it happens across a range of fronts, rather than smoothly emanating from the spark plug. Super-rapid combustion is not the ideal event, because it needs to happen over a period of time in order to PROGRESSIVELY do work/apply force to the piston over a certain amount of degrees of crank rotation. Mafia's comment about steadily applying the force to components makes sense here.

The strength of stock conrods is definitely an unknown, but we are agreed that lack of hammering from sharp peak pressures during knock/detonation will safely take them and stock bearings much further. Pistons too – the main reason I see for using forged slugs is because they are much more robust and will take the hammering of slight detonation for much longer without breaking ring lands. So without knock, the stock cast pistons should safely see good service for Mafia.

It was probably a poor choice of words to describe WI as an “add-onâ€, because it’s not something I believe. What I do believe is that it should be considered an essential integrated support system in the same vein as manifold design, combustion chamber design and cam specification . The only real negative I can see is the need to monitor your reservoir levels. Even that isn’t hard when low-level lights are available, and if your reservoir is sized to cater for more than one tank of fuel.

Edited May 12, 2007 by Dale FZ1

[wolverine]

mafia, are you going to install the 044 in-line with the walbro or replace it completely?

[The Mafia]

mafia, are you going to install the 044 in-line with the walbro or replace it completely?

I've ordered a Nismo replacement, as the 044 is simply too big, and is external. There is no such thing as an internal 044.

This will fix the problem

(I hope lol)

[BAMR33]

Mafia, do you use the standard air box with performance panel or do you use a pod with cai?

[The Mafia]

nah, pod filter. Engine bay is too interesting to fit a standard airbox in

[wolverine]

I've ordered a Nismo replacement, as the 044 is simply too big, and is external. There is no such thing as an internal 044.

This will fix the problem

(I hope lol)

they list them as external due to the fittings on the end. they mount in-tank with the correct fittings although it is a tight fit.

the nismo replacement is the easiest swap.

[Cubes]

I've ordered a Nismo replacement, as the 044 is simply too big, and is external. There is no such thing as an internal 044.

This will fix the problem

(I hope lol)

Nismo/Tomei is definitely the way to go.

The 044's can 'very easily' be mounted internally with very little playing around.

A few bits of suitable rubber for mounting, couple of suitable hose clamps, a hack saw, fuel hose and fittings from pirtek & either reuse the std sock or grab an aftermarket as dangerman4 did = internal 044.

------

Chris Davey, Absolutely no point trying to compare an auto's spool to the manuals as the auto makes a massive difference.

Dangerman4... rb25det auto + gt35r .82 = all its boost by 4100-4200rpmish and 5-6psi at 3000rpm if I remember correctly.

[jampac]

Chris Davey, Absolutely no point trying to compare an auto's spool to the manuals as the auto makes a massive difference.

Dangerman4... rb25det auto + gt35r .82 = all its boost by 4100-4200rpmish and 5-6psi at 3000rpm if I remember correctly.

I'm the one chris davey is referring to

I can lock the stall converter on my auto and also manual shift it so it's very close to a manual. This was done in 3rd gear (1:1) on flat road not a dyno.

No offence to you guys or to the RB25DET in general, but I find it funny how a lot of the posts here seem to have great concerns about the engine holding together. Just not a problem with 1jz-gte. I have run even higher boost, it just loves it, except i have to pull out masses of timing at anything over 20psi+ on 100ron fuel. Seems the turbo is good for around 25-26psi, but the fuel can't really cope with that boost. It has been interesting reading about the water injection that the mafia has done, especially how he has put in another 10 more degrees of timing. I know my setup on 24psi I'm running about 10 degrees of timing at around max torque, another 10 on top of that would help hugely. We did notice about a 5-6rwkw gain per degree of timing at the 21-22psi mark. I assume however that gain would get lower as the timing got closer to the optimal timing.

Edited May 14, 2007 by jampac

[Cubes]

jampac...

The boost curve comparison you have shown isn't comparable to a dyno boost curve as the dyno's ramp rate IS faster than 1:1 gear on the road lugging the weight of the car up to speed. This gives the larger turbo more time to spool, resulting in what appears to be a better faster spooling boost curve. + differential gearing + according to chris you are running the 52t 76.2mm comp wheel so again that too would improve spool. Too many variables to accurately compare the two.

I think a lot of people 'worry' about the rb25det too much. RB30's have been pushing 400 and in one case I know of 470rwkw on stock rods.

I really think the rb25det's only problem is its highish 9:1 comp ratio that causes problems when pushing high boost on pump fuel... Its either that or the rb25det's really are a weak motor; maybe the rb30's are tough as. Who knows.

I doubt it. People just worry too much, don't have a good tuner and don't setup the motors static comp accordingly for the boost and fuel they intend to run.

Years ago a Steve's RB25det (stock bottom end, baby 256cams, lowered static comp via headgasket) was running a HKS3037S (76.2mm 56t comp wheel) with a .87 a/r housing so near identical to the usual garrett gt3076r. He had all his boost in by ~4000rpm as you do also... BUT.. too many variables.. how is with the same motor one making all its boost near the same rpm as another with a much smaller rear a/r.... variables. We can't compare dyno sheets or take them all too seriously. On road performance is where it counts.

[DivHunter]

One other thing to throw in the fire is the Variable Vane exhaust housing which garrett said they couldnt make to suit petrol, giving the lowest possible exhaust backpressure necessary to maintain boost, whilst giving the best possible response. There's the reason why im not upgrading my dinosaur HKS T45S yet, i thing the next few years of turbo technology will blow us away compared to the "old" wastegated turbos.

2007 911 turbos are variable vein.

[jampac]

And you can't use a dyno either to compare cause everyone uses different ramp rates. I've seen figures from 10-20 and all in between for ramp rates. The difference between these two figures plays a big part in boost response and eventual power output at the wheels. The big figure for me is how long it takes to build boost on the converter when I'm drag racing as I don't use nitrous. At moment I can build to 23psi in about 4-5 seconds depending on how I use the throttle initially. Electronic EBC has helped heaps in getting it on even faster.

[Cubes]

And you can't use a dyno either to compare cause everyone uses different ramp rates. I've seen figures from 10-20 and all in between for ramp rates. The difference between these two figures plays a big part in boost response and eventual power output at the wheels. The big figure for me is how long it takes to build boost on the converter when I'm drag racing as I don't use nitrous. At moment I can build to 23psi in about 4-5 seconds depending on how I use the throttle initially. Electronic EBC has helped heaps in getting it on even faster.

Definitely... 23psi in 4-5seconds not too bad. What rev's is the stall holding?

[jampac]

Definitely... 23psi in 4-5seconds not too bad. What rev's is the stall holding?

Between 4100-4400rpm for that boost. I can't do much more as the Mickey thompson tyres just can't take it. It's a lot of torque, enough to throw my soarer which is 1720kg with me in it over the 60ft mark in a best of 1.595 seconds so far. That sort of 60ft time on a big single without nitrous is nearly unheard of on a 2.5L engine.

[discopotato03]

Dale I've been thinking about the costing of the twin scroll system and depending on what you pick the bits up for it may not be anything like 6.5K . With manifolds its been seen that the std lump of iron can support 300 odd Kw so all its really missing is the facility for an external wastegate (1) . I seem to remember ages ago JMS did a project car I think called OneEightVia (reverse panel Sileighty) and they managed to weld a section onto the RB20's cast manifold to mount an external wastegate . If you read that thread at FreshAlloy.com you'll remember that Geoff used one gate on the SR20 manifold but the path to the gates valve is divided as well . I think welding techniques have developed to the stage that this would not be the end of the word to do reliably . In the US they do it often to production manifolds and if done properly they don't seem to fall to bits . You may have also noticed that HKS's cast low mount RB20/25 manifold has a divided gate mount as well . Either of these gets the whole shooting match on the side of the head so thats the manifold and gate for what 8-1200 ? A ball bearing turbo from Garrett to support 300Kw /400Hp is probably going to owe you 1500-2000 depending on taxes etc . You won't get one out of the box with a twin scroll turbine housing but they can be supplied with them if required . The idea is to not buy one with the expensive Ni Resist GT housing but to get the TS one instead - it could be line ball or even cheaper depending on the cost of the TS Diesel housing and the machining cost to reprofile it for the GT30 turbine and cartridge . If you'd opted for an IW GT30 turbine housing your up for the cost of fabricating a dump pipe anyway , the twin scroll one only requires a bend and V band flange plus what it takes to plumb the gates outlet back in .

I get the feeling that the numbers chase is lurking again with the question being how little can 300Kw cost . My point is I reckon the twin scroll system done properly will give the RB25DET more of the larger N/A engine type power curve than a single scroll one and not lose any top end . This is a difficult thing to achieve but from an RB six point of view I think its a cheaper option that removing and gutting/replacing the bottom end in the search for larger capacity torque . Sure at very low revs it won't pull like a 20% larger RB30 but it wont cost like one either .

BTW I'm not nocking what Mafias does , great effort and learnt by doing it himself .

Cheers A .

Edited May 14, 2007 by discopotato03