Lithium

Thought I'd randomly bump this thread because of a strange unfolding of events. As I implied here, a Holset HX35 was my "first choice" for my R33 GTS25t but at the time it was not so easy or cost effective to get an aftermarket exhaust manifold which would suit my needs and I was kind of interested in seeing what I could do with the IWG GT3076R and had quite a bit of fun with that. When I decided to move on from the car I sold the GT30R setup to a mate and reverted the car to a stock turbo before selling. Some time down the track the new owner of my car asked about it and was thinking of replicating what I had done, and I mentioned that I probably wouldn't do the same now as I hated the IWG setup - and after a mix of "things falling into place" etc he ended up doing the setup I would have done in the first place. There are aspects of this setup which are better than what I had (ID1000s instead of Nismo 555cc, G4+ Link controlling everything instead of V5 Link and Apexi AVCR, GReddy intake manifold and Sinco exhaust manifold instead of stock manifolds, and a NZ Wiring cam trigger setup) but other than the ECU and injectors everything else would have been doable at the time I did it back in 2006. We didn't push it especially hard, it runs the smaller T3 undivided exhaust housing and I was starting to see hints of climbing EMAP - the aim was a responsive 300kw @ hubs on 98 so we called it a day at just over 310kw on 20psi. The wastegate opens around 3300-3400rpm, and the thing basically drives like a stock turbo. I've mapped target boost against throttle angle and if you're over 3500rpm then the target boost and actual boost track almost like it's an NA style log, the thing would have murdered my old GT3076R in terms of response and made a good 20kw @ hubs more. Kinda makes me wish I did go the Holset in the first place, and really I think even though it is using an old "truck" turbo the result still stands up pretty well for things making this kind of power on 98.

9280. Powertune were corrected and never updated the post.

I've never said it was the dumbest idea, I just made it pretty clear I questioned the spool claims for it and stand by that - given that even @reaper wasn't seeing full boost by the rpm claimed. I'd be interested in the results, I actually have a feeling I may already know someone who has done a 2.8 with a 6870 too. It's going to give away response to the 6466, and I had mentioned that nitrous would allow you your cake and eat it too if you were only occasionally going to aim for more power. I'd also personally go an XR9569S hahaha, but 2.8 + Vcam + 6870 sounds like a potent setup to me if you were going to do it.

Wow, that's pretty eye opening. Definitely when a conversation about it came up at the time it felt like I was saying something crazy suggesting that a 6870 would be fine streetability wise on a 3.2+VCam - wouldn't have considered the 7275 would be a viable parallel to an EFR8374 on a 2.6, and feel like if someone had showed up and claimed that at the time they'd have been looked at like they were an alien. Times have changed a bit Well done on an epic build anyway, been good seeing it in the Coota videos - absolute beast. Hard not to build something at that level without going through a few challenges and learning stuff along the way.

That's insane, nice work Its on a 7275 now? The old 2.6 EFR setup is still kinda the benchmark for RB26s for me, never experienced one anything like it.

Don't get confused here, I wasn't asking for advice - I've been tuning built and stock bottom end turbo cars for over a decade with NVCS or some kind of constantly variable cam timing and have not yet broken one despite being purely adjusting cam timing to suit the real world performance of the car. I've not heard of anyone sizing or adjusting static cams in regards to bottom end longevity, either. I'll pay attention next time, but I'm pretty sure there has been a very very close correlation between the torque developed and fuel consumption at any given rpm when changing cam angles... which suggest there is no major variance in mechanical efficiency when adjusting the cam timing at WOT, which is realistically the only thing which could result in more cylinder pressure being required to achieve the same torque level.... so realistically there will be pretty much the same amount of air and fuel in the cylinder at the time the fire is started whether you use cam timing or boost to try and achieve the torque level, the valves will all be closed at the time so the burn should progress in pretty much the same way, so it really gets a bit hard to explain how there could be any difference in the force the bottom end goes through. To me it seems to go back to being sensible about how much torque is delivered when, which you have a combination of cam timing, ignition timing and boost control available to help you manage.... whichever way suits your tastes or situation better. That sucks to hear, gutted you had so many issues - otherwise sounds like a potent setup. The bottom part makes complete sense. The trick with comparing how it went with the 6870 with and without the boost coming in as hard as it could is it is possibly a false economy type of comparison as how much torque it made down low was not really maintainable, if you'd never had that then it wouldn't necessarily feel like it was lacking. If the boost curve was brought in a bit more progressively then the shape of the curve would also make it look less like its fallen off a cliff at 7000, and arguably look/feel like a more conventional kind of power curve... albiet MEATY. It would still have been a complete animal of a road car, would still be very responsive down low etc.... just not quite as psychotic as I'm sure it ended up being. I think the discussion was at the time that you wanted >600kw without giving anything away down low to the 2.6/EFR8374 - I'm sure it would have been able to do that without going full send from the start of the rev range, albeit while possibly not having the EFR-esque transient response.

Wut. I'll try one last time, but I feel like I'm being trolled or something. OK, so lets assume this. A "workshop" has tuned an S15 which still has VCT on and with the current tune is making 500nm at 6500rpm at the given boost level. Timing/fuelling is optimised, but because of silly old "workshop" using VCT it throws its insides out. The engine is rebuilt to EXACTLY the same specs it was prior to throwing it's insides out. Lets assume that its identical in every way, pretty much as though Dose Pipe went back in time and pushed "workshop" tuner out of the drivers seat and did the tune instead. This time the engine is tuned with VCT off at 6500rpm, timing/fuelling is optimised for the conditions, but is running an appropriately different boost level to continue to make 500nm of torque at those rpm. Are you saying the identical engine which is Dose Pipe tuned is more likely to survive?

Where does the extra cylinder pressure come from, and why are we seeing no more torque as a result of it?

I'm not sure all the rationale or limits you are considering here, but just to pluck a random number out of the blue - what is the difference on the bottom end between making 500nm at 6500rpm with VCT on, or 500nm at 6500rpm with VCT off but running more boost?

The effect vcam has on power and torque is negligible compared to the boost targeting and ignition timing. It may make it easier to hit the high torque levels earlier, but you are not obliged to make use of that. There are MASSIVE amounts of setups running around which would be capable of doing this kind of thing with variable valve timing which are perfectly reliable. I feel like going to laggier/less streetable setup to avoid cracking blocks when all you have to do is exercise some restraint where it could be a risk is very very strange, though I could be missing something.

Snap, pretty much what I was getting at with my above post - just a bit confused about why you're blaming vcam instead of blaming the boost target/ignition timing which have far more direct influence on the kind of failure you're talking about

I'm bringing up a couple points not to be a dick, or even defend the fact I've suggested that this kind of combo is good - just like to investigate things which have either turned out well or not... it kinda helps both understand what is working and why to help all of us get better results. With the info you've presented so far I feel like blaming VCam is a mistake, especially if you have it and you're looking at spending money at moving away from it when its probably not the cause - at least all by itself. Peak cylinder pressures happen when the intake and exhaust valves are closed, some time after the spark event happens. There is absolutely zero influence that valve timing has on this all by itself. The cylinder pressures are going to be everything to do with the compression ratio, how much air/fuel combo has been forced into the cylinder, when the spark has been lit and how stable the combustion process is after that point. It is VERY possible with a given static cam head setup to exceed the cylinder pressures achieved using a variable cam head setup. Not doubt Vcam (and the turbo setup used) could be making it easier to create a situation where cylinder pressures get to a point the block can't hold it - but blaming vcam for a cracked block is a bit like blaming a Porsche GT3 for being too fast if you don't brake for a corner and throw one off the road. Things that improve torque naturally have the ability to put more stress on the parts which have to hold the associated forces, its up to the builder to ensure things are best setup to ensure the best chance of sustaining those forces and in this metaphor - the tuner/owner have to decide where to draw a line in terms of how far its pushed so they have less chance of overcooking the combination you have. By all means remove vcam if it makes you feel better, but it won't necessarily lose you the ability of cracking the block due to excessive cylinder pressures if you were pushing things hard enough to achieve that. There may be other reasons you are looking at changing as well, but realistically - if the only reason is due to cylinder pressures then perhaps it should be considered to hold back torque where you think it has caused a problem and keep the nice responsive drive that VCam provides while not compromising reliability. Modern ECUs/control systems make it not particularly hard to target the torque you want, so instead of building the car to be inherently laggier in all situations it is possible to have your cake and eat it too.

Ahh I see. And you think that the same cylinder pressures would not crack the block if there was a non-vcam head ?

What happened, and how is it related to vcam?

Rightly or wrongly, back when he had talked about that I was definitely pro VCam/6870 for what he said he wanted at the time.

Kinda want to know the story behind this, kinda understand why you maybe wouldn't want to tell it. Do you reckon the cylinder pressures associated with huge boost at those rpm become a general liability - or are you talking about the general power level? Something I've not seen talked about much, but kinda have discussed with mates on projects we've done (not specifically just for block strength, but usability etc etc) is that the whole "full boost by x..." I feel becomes increasingly meaningless as bigger power levels come along, start thinking more about "usable boost"... like how hard it is to get meaningful acceleration to happen. For quite a while I've been into the idea of tuning the target boost curve to suit the capability of the setup and what its going to be used for - like the MAX power delivery potential of a setup all the way may be less beneficial after a point, but what is cool is if the setup is capable of supporting useful power before 5000rpm while also being able to provide off its nut power >6000rpm is the dream imho. Not necessarily meaning that if you can hit 40psi by 4500rpm that you should.

You know, I read threads like this and wonder why more people don't use nitrous for the special occasions. Keep your 6466 as a good street turbo, shove a 150shot of nitrous down it's gizzard for roll races against cars which justify it. A 6466 is more than enough for street and track playing and 6466+150hp or so from nitrous oxide will arguably make the car at least as quick as it would be with a 6870.

It is possibly realistic depending on what boost number he is talking about and what size engine, how long it's loaded to achieve that or maybe how much nitrous. For what it's worth this dyno plot is of a RB32 with VCam running a 6870, it's going to be harder to make a 6870 come on quicker than this on a sensible ramp run on a dyno without nitrous. Definitely not with an RB28

I'd love to hear about any of them having failures if they're that common, as obviously they've caught my attention and so far looking at individuals experiences I've only seen Precision reliability issues (granted, that's probably partly tied to people just sending it with them) and people getting performance improvements going from Precision to Xona. I've not seen anyone have any Xona failures anywhere yet, though they also are not used as much so it's hard to get a failure rate but I definitely don't want to be suggesting something that has any problems. Like anything, any claims without proof or data should be taken with a huge grain of salt.

Interesting, yeah I personally wouldn't swap from a 6870 to a Xona (or vice versa for that matter) - they are both similar enough that it's not going to be worth the money. The reliability thing sounds odd, haven't heard much issue about them at all. Is it definitely the Oz agent, or someone who can get Xona rotors but sell precision? Lol

Oh yep have seen all the stuff there, the EFR7163s tend to make 800-900whp max depending on the dyno (which is consistent with the Xona result) - which is decent, but not any territory outside of what people have made with singles. Sky-Engineering are one of the outfits which use "BHP" so that 1000+hp number is not what it looks like, if you're assuming that's whp and just by reputation I won't really necessarily take results from there as gospel. The video blog didn't show any results, in terms of presentation if you like that then definitely have to weigh that up - but so far I've never seen a legit 1000whp all-turbo from an EFR7163 setup.... let alone on the likes of a Dyno Dynamics dyno. Nothing against them, just strongly suggesting that they aren't the best tool for your job by a long shot.

I guess results all vary, I'm not sure that I've seen a solid EFR twin result yet - like not bad, but nothing to sing out about yet... be interested if you have anything you can point me at though as I obviously like to keep aware of this kind of thing. The Xonas are worth a look for the right situations I think, again I don't think it's the right thing for your needs but they are great. Popularity does not necessarily have any reflection at all on how good or potent a product is. I remember mentioning Precision turbos to people in NZ/Oz for YEARS before they started being used and people basically responded the way people tend to respond to Xonas at the moment, more or less the way you did. Better the devil you know, I guess?

Between this, and me trolling this thread with Xona Rotor propaganda - I happened to have stumbled on a pretty relevant kind of post on Instagram today, dude turned out to have swapped from twin EFR7163s to a single Xona Rotor XR11569S on his RB28. I stand by the 7685 being probably the beast for your aims, but thought this would be interesting info as a point against the EFR7163s.... https://www.instagram.com/p/CKZ0greHgfj/

All sorts going on wrong with that, no least being that Garrett have been gradually adjusting how they provide power estimates for a given compressor flow. Back when I first started reading compressor maps they took the flow at the chokeline of the compressor at PR2.0 and multiplied it by 10 - which in most cases with modern engines/tuning actually resulted in pretty conservative engine hp estimates, ESPECIALLY when E85 was concerned. When the GTX series came out they seemed to stick with the "multiply by 10" strategy for lb/min to hp, but now they pulled the "peak" choke flow for the compressor instead of whatever it was at PR2.0. When the GTX Gen2 series came out they seemed to have changed their multiplier to 11, and they seem to have stuck to that with the G-series as well. That graph above looks like they probably forgot to use the same multiplier across the board, and somehow still let it get to market like that - which looks ridiculous. I can sortof see why they've changed the multiplier as the old one didn't really reflect what most were getting out of their turbos before, BUT where it starts feeling disingenuous is where they've left the previous generations rated using the same old system - which makes it seem like the difference between the old and new Garretts are much bigger than they really are. I guess an example would be if you rated a GT3582R using Garrett's estimate for GT, then for GTX, then GTXG2/G-series it would be respectively 600hp, 650hp, and 715hp. All for EXACTLY the same turbo. On the flipside, if you did the same thing for the GTX3584RS which Garrett rate as good for up to 1000hp - that comes out at around 750hp, 890hp and 980hp. Basically they are claiming it as capable of 250hp more than they would have pre 2010. Ah yeah, its been many a year since I've been around 2.6s with low mount twins and comparing with different things - it will be a beast by comparison, lol

This kind of thing is why I asked all kinds of questions trying to ascertain where you were wanting to go, as you didn't put that across with your original question. The fact you were asking at all, and the fact you highlighted that it would be on pump gas, used on the street and sitting at around 700whp most of the time suggested that you might be quite concerned about the "around town" part of the rev range. Realistically if you are concerned about the 8500rpm part of the rev range then you have to be willing to sacrifice some of that bottom end, which it sounds like you are now - hence we've moved on and a couple of us are telling you to go 76mm Precision Different people like different things, and this is why people are silly to make out like there is one size fits all - there will be people who will shake their head at the big cams and big turbo discussion for a street car that is going on. Hell, it is not the way I'd go personally BUT I understand that different strokes work for different folks. I've seen that Real Street video misses this kind of point entirely to me, in some ways it shows how the 68mm is way better for the street - or that the 72+mm is where you are transitioning into something which is more of a drag/hp hero car. It dulls the car down on the road, but is much faster if you're keeping it on the boil... IF you have the build to keep it on the boil like that. A 72mm+ turbo that does everything at the top end is not going to be the perfect thing for someone who might want to be able to accelerate hard without dropping 3 gears and / or using rolling antilag to make a quick burst of acceleration happen.