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from what i have done and what works on the cars i have done work for, short runners with a suitably sized plenum will always work as good if not better than standard length runners with more hp and especilly torque available. hope this helps you decide.

no one has yet to prove when they become restrictive because the two have never been compared so no one will be able to answer the question. i have offered a plenum* in the past to anyone making 300rwkw with a standard one to help prove a point but no-one has taken up the offer.....yet. the magic 300rwkw (400rwhp) mark is always mentioned but also unsubstantiated, just a myth waiting to get busted (i love that show). surely the car can continue to make power, and which car wouldn't, as long as the turbo will support it and you keep on pushing more boost into it. just one thing to say, efficiency is the key when trying to make the most of what you have and with that you will see the benefits. again, thanks Ben for the vote of support. from when you took me for a drive, lag is almost extinct considering the turbo size and i have also noticed this on a rb25 equipped with a gt35/40 with one of my plenums. this is just my 2c worth ps - watch this post get deleted

ben, as always, hope everything is going well with the car. let me know how you go with the next tune. i thinks its time to put some serious boost into it.

pics please

$40 delivered for rb20 inlet manifold. i am only after the runners, not the plenum (top half)

how about $40 delivered for rb25de intake manifold. i am only after the runners, nothing else.

$40 + delivery for lower runners only you can still sell injectors etc seperately

thanks ben steam pipe they are

i wouldnt recommend anyone else if you want some of the best exh manifolds out there. www.6boost.com free plug

nice exh manifold, yes, 6BOOST, good cam (rb30et) yes. i put this package together for a customer and he doubted about going the 1.06 but has never looked back. a total of about 4. dyno time...no. 2 hrs with one tuner ending in a blown headgasket on the dyno and then another 2 with a different tuner...........and i must say i was suprised at its super responsive feel one thing i forgot to mention the rb30 single cam combo is an auto, jatco backed, so imagine what it would do with a manual Ariel

at around 3000-3200. i would never even consider or recommend a 0.82 for anything with a 3l capacity especially as twin cam. the 1.06 is perfectly suited and have plenty of scope for power and torque.

24psi on a rb25 with a gt35/40. not sure exh housing size though. that car made 480+rwhp and another rb25/30 has made 501rwhp on 21psi, slightly bigger turbo than 35/40. just to throw a spanner in the works, not with standard inlet manifolds. maybe its something to do with the standard inlet manifld being good for upto 300rwkw also rb30 with a 35/40 with a 1.06 and a sh1t tune and blown headgasket (customer wont be going back to him again) made 385rwhp on 20psi. since made 493rwhp on 23psi.

xf tb is 65mm at the butterfly and tapers to 68mm at the entry and exit. cubes - from what i have done and tested and feedback from customers, none of them have complained about the 80mm tb. am-performance - ant - please stay away from water/meth injection, this the the new millenium and these are not force fed holden/ford v8's. with a decent tuner and pump fuel, well over 450rwhp is possible on reasonable boost levels.

Q45 is acutally 83mm i have done testing on XF and 80mm tb's and have noticed hardly any difference between the two. obviously power gains were had with the 80mm, not huge but noticeable but its up to you recommend a 3" intake side and 2.5" turbo side for the cooler piping

very impressive SleepingTalon. would like to see logs and dyno readout. i might be wrong but aren't the ratings of fuel differnet in US compared to Oz ?

stall size has more of an effect on torque and when torque is made and to a lesser extent the hp as 2rismo said, depending on the amount of slip. more slip less hp

sydneykid - any luck with egt logs or fuel maps or clarification of your comments ?

these photos can be seen in more detail on "JUN" r32 gtr canberra car in hpi issue no 67 pg 50 onwards

give me an engine and i will show you it shows the ports ability to flow air when the inlet valves are fully open, although not spot on since i have not tested using a head and plenum on a bench. this will be around the corner once i have the bench setup for the rb's head and plenum sorted. what was the actual egt degrees or % difference/variance ? your comments seem to contradict themselves. on one hand #6 requires correction (upto 6% someone mentioned - which is massive considering the the afr's you are talking about) and one would assume this would bring it more closely inline with the other cylinders, if tuned correctly. yet without correction there is "very little temperature difference" which is directly related, amongst other things, to the amount of fuel in the mixture. figures will usually shut me up. maybe a copy of a egt log or fuel map from a computer. this is the whole idea of the thread, theory vs practical and all this from real life experiences go a long way to helping find out the cause of the problem so many people suffer from. thanks again for your input, your posts are always read with much interest. Ariel

have to agree with turbine and dirtgarage and this was what i was looking for when typing up the original thread. r31nismoid - flow test results would show that the rear runner has an inability to flow the amount as the other 5 cylinders do in a rb26. even more on a evident with a rb25. standard rb25 runner flow from 1-6 at 25" is below and this pattern is typical of all plenums with a centre feed throttle body. just look at 3 & 4 compared to 1 & 6, well over 10% variance which can not be good in my eyes. 1 256 2 260 3 283 4 290 5 259 6 260 sydneykid - please dont assume a simple rule of thumb for plenum volume based on engine capacity. it is more dependant on individual port sizes of the head. an overly large plenum can have a negative effect and a smaller than expected plenum can still be a restriction in terms of overall flow available to the engine. i still dont have a formula but a decent idea what is required from different port sized heads. engine bay dimensions and application may not necessarily require the optimum sized plenum which is also something that needs to be taken into consideration. i like the idea of modified water plumbing and certainly something i will look into when i am putting my engine together.

busky2k - in terms of plenum flow yes this is a problem with the majority of factory inlet manfolds, regardless of design, each has their flaws. shaun - no1 might run the cooles, but also has less airflow than that of 3 & 4, i would use 3, but that wouldn't be to hard to change. Turbine has the idea, put them on all exhaust runners. duncan/beer baron - this is also the case with the rb26, but less prenowned, which is why i cant understand why a lot of rb26 owner's bag it out. r31nismoid - well said, but not everyone has a good tuner or a computer capable of individual cylinder trim of injectors. this is about trying to do everything possible so no matter what a tuner does, within reason, it can be fixed cheaply and easily and to the maximum effeciency the engine can possibly run. depends which way you want to look at it, "cure the cancer or prevent the cause". plenum design, water temp and fuel rail design (dam where is that thread again) seem to be the general concensus and all contributing factors to the problem. any other opinions/coments ? Ariel

i agree totally therefore its unbalanced from the start. that would mean the unbalancing is only having a major effect on air distribution when the airflow required for 300rwkw is demanded this may explain why less powerful engines are seeing these problems when combined with 1 or more other influencing problems.

know thats the king of thinking i am after. it appears to be a problem with std and equal length as i have seen it with both std, ebay and reputalbe aussie brand exh manifold but i like the theory and it is something that also needs to be taken into consideration.

just out of curiosity what was their power level probably doesn't provide answers

thats the easy way out and another bandaid solution