bigmikespec

...and you will choke the restrictive exhaust side.

What I meant by my comment was the reason why people choose camshafts with longer duration is not because they want to make power later in the rpm range, that is just a consequence of a multiple of engine changes. As I said before, if you have low exhaust manifold back pressure relative to boost pressure (and this is usually in a high rpm engine ith big turbo that won't make a lot of power below 4000rpm... as an example), then you can choose longer duration camshafts to take advantage of scavenging effects during camshaft overlap. XKALABA's result with going from 260 to 250 is not an accident, it makes total sense as he has factory mounted twin turbochargers that have high back pressure relative to boost pressure.

Please don't spread that... the reason for longer duration is not 'when', it just happens to be a consequence of longer duration.

Diesel block? (RD28)

Works for NA's because they have atmospheric exhaust back pressure, when a turbo engine has boost pressure higher than exhaust manifold back pressure then you can choose an NA cam (almost).

Squish and quench (different things) is a whole different discussion. The RB26 does not have a lot anyway (squish area that is) and by the time you fit over size valves and relieve around the heads of the valves for flow there is even less. What you don't want is high squish velocity which creates hot spots where flow is forced around sharp corners. Big power, big boost, high rpm less squish is the way forward! A little around the perimeter of the chamber is probably good to quench that area to help ring seal and blow by.

That is the same thoughtI had up until I talked to some serious enginer builders; I explained exactly that and all dismissed it stating their experiences. It makes the engine more prone to issues with excessive squish velocity and the handful of hp made off boost was offset by the much larger increase in performance by increasing boost pressure. I agree there is a balance, but it would be dependant on application as with most of these decisions.

I don't know why you would do it just to get a handful more hp off boost; you are fuel constrained (or more specifically octane constrained). More info on NYTSKY's mate would be interesting!

What size A/R turbine housing? You want low back pressure with those awesome cams, 12mm lift is getting up there, valve springs will have a hard time. Wicked!

Borg Warner S300SX (S366) with divded 0.91A/R housing, twin Tial 44mm MVR gates, and Tial BOV... all brand new in boxes. Good for 700-800hp. PM for price, etc.

This bloke! Good post.

It is just a manifold, it will make more power with it but won't do so efficiently. A larger volume plenum is better as it allows the air inside to distribute itself better to each of the ports. Are you still using the individual throttle bodies? Greddy is a nice cheap upgrade as it is over 5L which is closer to two times engine displacement.

Yes, great question!

Unfortunately there is less interest in actual development of performance parts for the RB26 as the majority of the crowd that have them want flashy ricey bits for a street car and not motorsport orientated parts. Probably why there hasn't been much work done in this area, especially considering plenum design is often left to OEM's or big motorsport teams. I know Ariel from CPC is doing something really good, I spoke with him and was super impressed but his product is a bit out of reach for me dollar wise as he is develping a top shelf product. I would love to do a Lehmann style manifold, I started messing with a design but got too busy with house rennovations.

Well the short reason is that the head porter would like to move to a single throttle body and ultimately a plenum with larger volume (as do I). Considering the ridiculous price of most aftermarket plenums as a means to get by for the short term I was going to convert the OEM plenum to a single throttle body.

Hello everyone, Just wondering if anyone has converted the OEM RB26 plenum from individual throttle bodies to a single throttle body? I am not interested in the for and against argument as I am well aware of it, I don't want it to turn into a 'why the hell are you doing that for' from a bunch of 5min experts. Just wanted to know if anyone has done it and what were the recorded results if any from doing it? Thanks, Mike

Good work Danh, glad to hear you haven't given up!

Hey fellas, Just need the following stock parts as samples for some custom parts: - stock cast piston - stock rod - gudgeon pin - rod bolt Just need one of each of these, anyone want to give away some old parts? Thanks, Mike 0407801338

Might be, if it is real, lol... Send me a PM if you want to know what I am thinking. Aftermarket jobs like hypertune and nismo just command too much money for performance benefit and good luck trying to get any CFD or other testing from either of those to prove what they advertise.

Thanks for the advice but I won't have a fake and a genuine to compare only the one I am going to look at. If anyone has any dead give away tips feel free

So who can tell a fake Greddy plenum from a genuine? What are the distinguishing features? For those that have a Greddy plenum, does the red Greddy decal come already fitted to the plenum out of the box or do you stick it on yourself?

What is the reason for switching to the twins? I would have thought the opposite as the surge slots bypass air to avoid surge hence efficiency losses.

+1 for Ferrea, and get their +1.0mm valves

What front compressor housing are you using, normal -5 or surge slotted? You will be more at risk of compressor surge with a bigger compressor wheel.

Yes I know you can buy housing separately, it would be nice if you can just buy one direct from BW or even from a Indy team???