Lithium

Ohh. I may have made a bad assumption with my previous post - I kinda glanced at the power and assumed your were running ethanol (which kinda assumes a certain airflow vs power conversion) which would make that power seem perfectly within the G30 770 capacity but actually, looking at the rpm and boost you're right... all things being "typical" your engine is likely to be breathing a heap more than that turbo would want to give at that boost. What fuel are you running on?

Argh also, I missed a point above - it seems that especially with the Pulsar turbos third party dealers seem to sometimes mess up orders. I've seen it (not directly experienced it, but definitely seen it happen to other people) where someone will order something like a GTX3584RS and end up with a GTX3582R, or a "G30-770" turns out to be a GTX3071R etc. If you had a GTX3071R or even GTX3076R or G30 660 and tried to run it like a G30 770 then there could easily be carnage. I've seen people run near 600hp @ hubs on the Pulsar G30 660 on ethanol so it can be done, but probably not super wise.

Seeing as it's a little ambiguous as to why you might be upgrading, I'll give some bullet point answers based off the two reasons you may be: Upgrading because you're assuming the failure is overspeeding: A G30 770, either Garrett or Pulsar version should not be overspeeding at this power level. It's leaning on them a little but should still be in a relatively safe place Any details on how the turbo looked/what broke and when? First time I've heard of a catastrophic failure with a Pulsar, can never rule out a manufacture issue with them (I know people who've had this with Garrett, Borg, Precision etc so Pulsar probably won't be immune) You can also overspeed the turbo without actually trying to make more power than it can support, if you have a restrictive intake or intercooler, or some kind of boost leak then there is the possibility that either the turbo is seeing a much higher pressure ratio than you'd guess based off when you see at the intake manifold - or alternately the turbo could be moving a heap more air than the engine is seeing, both causing it to overspeed while actually giving the engine less air than the turbo can provide if everything is working efficiently. Make sure there is no other issue with your setup that could possibly cause a premature failure, like oil feed blockage or something to that effect ^ Especially #3 and #4, make a seriously good effort in ruling out or identifying any possible cause there because you don't want to spend >2x the cost on a replacement turbo to end up with the exact same thing happening. Upgrading because you're levelling up: How much more power are you after? If you're happy with the power and response you had already, 590hp @ hubs isn't a heap short of what the compressor supports with those so going up an a/r may result in an underwhelming increase in power vs how much extra lag you get from it - imho the .83 seems like a good balance on the 770 even if it may hold it back a little at the top end of it's capabilities. Check out the 6466/G35 900 thread, someone has gone a 1.06a/r T4 Garrett G35 900 on their VCam RB28 and it's a lot laggier than this. There's no magic, if you have a bigger compressor, bigger exhaust wheel, big tubular manifold and larger exhaust housing then twin scroll is not going to offset the response at all.... but it will be capable of an extra 100kw @ wheels safely. If you are after an incremental increase maybe consider the 1.01 T3 G30 900, or if they have it a 1.06 T4 G30 900 - I'd wager that has a good chance of being a sensible in-between if you are concerned about response. It's unlikely that you'll be able to go up in power potential without some cost to response but that is one way that's likely to manage the impact somewhat. Just my thoughts.

PS part of why I did the above is so you can see your setup is likely reaching as high as PR 3.3

K, I've thrown some numbers loosely based off your dyno plot and what you've said into BW Matchbot. I've selected the EFR8474 compressor map because it happens to be an excellent match for what you're actually doing and also funnily enough Borg Warner doesn't have the Garrett data I used turbine flow data for the G35 900 with 1.01 hotside (as the 1.06 T4 isn't listen) to loosely match the turbine data. Very loose but should give a general idea of what EMAP and pressure ratio etc might be doing. https://www.borgwarner.com/go/3I1H4G

2.3PR is around 19psi boost at sea level if you have zero intake restriction - you sure you aren't missing a PR there?

Just to clarify, has yours failed or are you worrying about how risky you're playing it?

If you hate Precisions but like some of the "insane power vs turbo size" things maybe worth having a nosy at ApexTurbo, be super interesting to see something like one of their 64mm or so type units on an RB30. They seem to be getting results that seem impossible, even when you consider the latest Precision offerings... most significant Evo/Honda turbo records have already been picked up by things running ApexTurbos and one of the Honda guys "downgraded" from a bigger Precision turbo to a 62mm Apex to try and make it easier to get off the line and ended up making significantly more power at the same time, like they cracked 1000whp which is mad even on a US dyno without nitrous etc.

A Holset HX35 and a Mitsi TD06(/SL2) are *completely* different turbines - you absolutely cannot take what a Holset 10cm divided housing behaves like and try and use that to determine what a turbo with totally different housing and wheel geometry on both sides will do. May as well say they're both loosely based on circles so will behave similar. Hmmmm. I did write a post saying that the only ones I experienced were the bigger ones but decided to verify and there is every possibility I had actually been exposed to TD06SL2 20Gs when they had been referred to as simply "TD06 20G" so I'm actually going to have to not weigh in on that. The only thing I *can* add to the "maybe the SL2 doesn't add as much value as it's given credit for" is arguably the most famous TD06 aside from the TD06(something)-20G is the classic FP Green which was basically a 50-trim T4 compressor paired with a TD06H turbine, and had the reputation of outspooling and out flowing 20Gs of almost any combination... though this potentially brings the whole "compressor vs turbine matching magic" side of things into the discussion. Sometimes the result can't exceed or fall short of the sum of the parts. My memory also probably stretched here, but one of the best 20G setups in the entire RB kingdom was @Roy's RB20... I'm not sure that was an Sl2?

Good call on the altitude, I even thought briefly about that when I posted the comp map but so used to people living close to sea level that I didn't dwell on it... I guess there are a lot of areas people live that are high enough that the relatively "not high boost friendly" shape of the G35 900 map would mean it'd not be hard to over speed them when trying to make their rated power even at not a particularly high altitude. To add to that, there are a LOT of people likely running around out there with boost leaks. Like people think they've gone above and beyond if they've done a solid spanner check, or even smoke tested their pressure sides of turbo setups - before tuning where possible we'll try and pump 20+psi through the intercooler piping and the amount of times we've heard rushing air on a "nah it's definitely all sealed" setups is solid, potentially in the area of 50%+. I'd not be surprised if the reason a lot of the car's my little group have done that have ended up with "better than people expect" for the setups are if anything an indication of how many people are running around with undiagnosed issues. If you're one of the MANY people who are running around with a boost leak then yeah, turbine speed is the only way to be sure unless you pressure test it - I am certain some of the EFR horror stories come from boost leaks, they were basically booby trapped by having a selling point of coming with an internal BOV that just happened to often leak at high boost. Perfect. Re: Precision, yeah I've seen some data from people testing big Gen2 and NextGen Precisions and while the Precisions aren't the most "low inertia" turbos it becomes clear from the turbine speed stuff that some of the "magic" with them comes down to the fact they can actually tolerate a hell of a punishing. Like its not unheard of to have 76mm Precision turbos being run at speeds (as in turbine rpm, not tip speed....) that you should be starting to think about calling it a day with a G35 900 hahaha.

Ok, should have said that was your priority instead of response - a preference because you just like the idea etc is fine. So the TD06-20RX will basically make the power of a 25G but with the spool of a 20G. Turbine is the same so should have the same "Mitsi turbo" exhaust note you're probably looking for.

Are the Trust TD06-20RXs super super cheap? I'm not sure why you'd go a TD06 these days unless it costs almost nothing. From the perspective of someone who has been into RBs/turbos for over 2 decades now - I remember a time where TD06 20Gs were a wicked thing for an RB20/25. Like they cost less, were strong, and performed admirably (for a journal bearing turbo) against Garrett/HKS turbos which cost a lot more back in the day - a 20G would be a solid alternative to something like a Garrett GT3071R or HKS 2835 for sake of argument. That was around 20 years ago. In that time Garrett have since released a GTX3071R, then Gen2 GTX3071R, then the G25/G30 range of turbos - and there are budget equivalents semi-loosely based off all the previous things. This TD06 20RX from everything I can see is basically Trust finally upgrading the compressor wheel (but nothing else) to something comparable flow wise to the improvement Garrett did with the GTX3071R, a turbo that's been available for about 13 years now. If the year was 2010 and this turbo had just came out THEN (and at a sharp price point) then I'd understand threads like this coming up... but in 2023 I just don't have a clue why they'd be a thing anyone would consider. So yeah, short answer - it's something that will spool like a TD06 20G (a 400whp turbo from 1998) but is capable of around 10% more power. But a Pulsar GTX3071R (or the like) will probably cost less and do everything better.

I'm not aware of any "random" failures. I feel like I heard of people running into issues when going on a mismatch combo but it may be from this thread, or associated with the guys posting it - the general agreement at the time is that it due to overspeed which thanks to the more efficient G-series wheels etc it becomes a lot more likely than earlier Garretts so the idea would be to keep within the recommended "area" of these things. To get an idea of if 2bar-ish is a risk, the max wheel speed published for the G35 900 at PR3.0 lines up with around 79lb/min I'd not necessarily expect that line to be a "it asplode when you go past this point" level, but realistically the further you go from that line the risk climbs exponentially. Ironically the anti-Borg Warner silly people chuff at the idea of wheel speed sensors being a good idea as though they're the first turbos to be efficient enough to be able to blow themselves up if you let them keep pumping air, but this is why it's not a bad idea. It's worth noting at that map that it looks like compressor efficiency is actually QUITE solid still at the maxrpm which means it'll be super easy to overspeed one of these things, the common method of waiting until it stops making power easily is likely to get you way off the map if you're going for >2bar. The "next best" idea is estimating your airflow and picking where on the compressor map you land based off that and your intake manifold gauge pressure. My super bro-math way of estimating required airflow with a 2wd car on a hub dyno is relating lb/min to kw with a factor of 7.1.... so if you wanted to know what is a "safe max" point to push a G35 900 on E85 on a hub dyno at bar would be 79*7.1 = 561kw. If you pushed one to say 600kw you could also go 600/7.1 and find you're likely pushing in the territory of 85lb/min of air which is starting to get a bit up there but shouldn't be COMPLETELY insane. Ymmv as different dynos, different tuners etc will give different results A lot of modern ECUs support VE based fuel equations, and if the tuning is done competently (injector/fuel/charge temp etc settings all calibrated accurately) then the ECU will have a pretty good idea of the airmass getting into the engine as otherwise they'd not be able to command the correct injector flow to hit target AFR. If you have a Link ECU for example you can check a value call "airflow per cyl (estimated)" or something like that. If you get that value and throw it at an equation like "(percyl * 6 * rpm / 2) / 453.6" which takes the g/s airmass the ECU is assuming each cylinder it's getting and converts that to lbs of airflow consumed by the entire engine over a minute. I've found it to be relatively on point for cars I've tuned so far... this again should be <80lb/min at 200kpa MGP if you want to be safe.

Fairly sure I've already seen a bonkers NextGen 7275 result, trying to think of where. Could just be another Apex turbo result as those things are just mental

Thought I'd bump this thread as Precision have been superceding their Gen2 units with the "NextGen" range and the updated 6266 and 6466 have just been released, rated at 925 (more than the Gen2 6466) and 1000hp respectively so decent improvements and probably most relevant to people who would be reading this. The NextGen 6670 has also been released, kinda like a 6870 flow (quoted at 1100hp) but sitting between the 6466 and 6870 size wise.

PSA: seems FullRace have limited stock of one of the best turbos you could put on a car that also happens to be one of the hardest to get: https://www.full-race.com/borgwarner-efr-8474-turbo

Yeah, I've actually tuned a car using the S257SX-E "smaller brother" running a 1.15a/r divided hotside on a 2.3 4G63 and that made ~390kw @ hubs and was JUST hitting 1:1 exhaust vs intake manifold pressure at that point - definitely more in it but we called it there as it'd hit the target for the setup but the thing is an absolute beast, response etc is awesome. Here's a clip of it in action to give an idea:

That may well be partly to do with cam timing though I'd not rule out the possibility that it's the hotside. I've seen a good number of EFR7163 results with divided housings which seem to choke up a bit, and realistically that turbo is not necessarily ever going to be ideal for an engine that flows reasonably well compared to a more mild SR20DET (like an RB25) but as much of a divided housing fan I am, I'd be super concerned about a divided EFR7163 working well on an RB25. EMAP seems likely to get up a bit, and with internal gates that can turn into a super big pain in the a55. I feel the cost and expense of a twin scroll EFR on an RB25 aiming for "only" 300kw may not age well and would be more inclined to go with an open housing 7163 if that was the direction. There isn't a lot out there, I personally am not a super big fan of the EFR7670 relative to the rest of the EFR range. The only RB25 EFR7670 I've experienced was a T3 open one so not the best example - however I'd not recommend it for what it sounds like you're after, it was definitely lazier than I'd hoped or expected <4000rpm and I'd say a small G30 or the likes would actually be a lot more rewarding if you're only aiming for 300kw (hubs or wheels?). As I mentioned above, I feel like the healthier flowing 7163s I've seen are ones with open housings - here is a dyno plot from a car over here in NZ running BP98. This is a 4WD Primera running an SR20VE (someone can probably correct me but I get the impression the VEs drive turbos a little less at lower rpm but hold on WAY better at high rpm compared to their DE siblings?) and a vband open housing. Despite being the VE head I think this is a pretty decent spool for this kind of power on pump gas: Being able to support that kind of power on pump on low 20psi boost makes me suspect it would be very nice on an RB25 in terms of not being excessively small, but also can imagine it'd stand up NICE in the sub 4000rpm range. As has been mentioned elsewhere in here, the boost threshold on EFRs isn't necessarily where they really impress - it's how responsive they are to throttle when in their boost threshold area. This kind of setup has potential to be hilariously fun on a 25 you want to stand up well from low rpm. As an aside, despite being WAY off topic here and probably an unpopular viewpoint - I went for a drive in an EFR7670 car and also drove my old Skyline which now runs a Holset HX35 and the Holset setup made the EFR feel lazy as f**k. Granted, it was comparing a ~50lb/min turbo with a ~62lb/min turbo - but the Holset was making 320kw @ hubs which is a nice spot for a pump gas RB25 street car and it drove hands down better than any other RB25 I've driven. Full boost around 3200rpm/3300rpm from memory, insane transient response, and sounded awesome. Annoyingly that was my original choice for that car when I owned it but I went GT3076R to make things simpler and go stock manifold but that turned into a nightmare of trying to make boost control stable. At least I was a guinea pig for people doing the same thing in future But yeah, my old car makes more power than when I had it and spools almost like it has a stock turbo.... I suspect a huge amount of people over the years who have looked into RB25 turbo upgrades would actually choose that turbo in an instant if they experienced it - especially when you consider how cheap they are. On what kind of dyno? On a hubber I'd expect so, spool should be pretty respectable but it's obviously a journal bearing turbo - the Airwerks range are decent but not the most (or least...) responsive under foot so it kinda depends on what you're comparing to. Given the turbos aren't even in circulation yet it's hard to say how seriously they should be considered but if it helps, I'd not go for one if I was counting on it being all in under 4000rpm - but I'd also hope not too much later than that either.

Yeah. When I saw RB335's comment I had a "I'm SURE we've been through this before and I actually thought it was in this thread" moment. I'm also not talking sh1t when I say some of what I said above, I've actually effectively "put my money where my mouth is" (and convinced other people to make similar educated gambles off the back of it) and convinced people to upgrade compressors while using the same turbine after being told that the hotside is a restriction and suddenly EMAP has dropped and making more power has got a lot easier. What does my head in is that Borg seem to often have the Airwerks range of turbos "a step ahead" of the EFRs in terms of nice compressors - they may not necessarily flow heaps more for the size, if at all, but their maps often suit things like RBs and JZs a lot better than their EFR counterparts. Its like the EFRs are more aimed at 4cylinders, and SX are "for bigger engines". If a 68mm 9180 is not big enough for a RB32 your only choice is a 74mm EFR9280 which fixes the problem but definitely comes at cost in terms of spool *and* you really need to go the 1.45a/r hotside to make the most of it whereas the latest generation Airwerks compressor looks like a thing that would basically be what a lot of RB people who went for 9180s were looking for but didn't get because of their anaemic performance at lower boost levels (and not realising that looking at the compressor maps). Behold the S368SX-R compressor map, same inducer, smaller exducer, is able to flow similar to the bigger EFR9180 compressor at the same rpm so you don't actually have to spin it any faster despite the smaller size: So the red line is where an EFR9180 compressor starts being more useful as a hot air pump, and the orange line (more for interest sake) is where the turbine rpm speed reaches the maximum listed for an EFR9180 if you are at all nervous about the idea of spinning the 80mm turbine faster than the EFR9180 was mapped to. If Borg combined these two I can't see how you'd not end up with what the EFR9180 "should've been" for the bigger engine guys, it'd actually be more responsive than the 9180 and more likely to give the power levels you'd have expected if you spun it closer to that 116krpm zone (the S368SX-R is actually mapped out to 126,000rpm but I feel like it's wise to keep the 80mm turbine not being spun any faster than Borg ever advertised for it).

Nope, 116kRPM is the "beyond this we make no promises about how long the turbo will last here - good luck" point. The red line I've drawn is more the "the turbo is probably able to push a bit more air than this but it ain't gonna be pretty" marker, beyond that pre-intercooler IATs are going to skyrocket and exhaust manifold back pressure is also going to take off as the gate is going to have to shut to try and squeeze more out of the compressor. That funnily enough causes back pressure to go up a lot as the drive pressure isn't being diverted past the turbine. IMHO people have often underestimated how much hotsides on Borg turbos flow because of mismatched compressors hitting this kind of situation. Really its not more turbine that's needed, it's more (or a better) compressor. I've put a cute orange star roughly where @Predator1 sounds to be sitting

I like this discussion. Yeah, those are fair points and some of them circle back to an earlier comment I made on Alpha-N type strategies - they're much nicer if you can actually control the throttles yourself, same goes for TMF type ones where you don't have to worry about anything beyond the throttle itself affecting airflow into the engine. Ultimately seems like we're on a similar page in terms of things we've seen but potentially feel differently about what is acceptable. I have been happy with my experiences with speed density mapping, am aware of it's shortcomings and strengths and it tends to suit the purposes of what I've dealt with but yes. I can't ever see a situation where it's not going to need a lot more calibration effort than MAF does, but then MAF is never going to be as accurate in transient conditions. So far the "best driving" cars I've driven are speed density based but I guess there is the other factor we touched on earlier, some OEMs actually do both to try and get the best of both worlds haha. This definitely gets me wanting to play with M1 Dev again and try dumb ideas.

I clearly easily get carried away, so I'm gonna restrain myself haha. Basically you have MAP/EMAP as a axis - so the pressure ratio across the engine. It flattens the hell out of the map as the effect on fluid flow from pressure ratio is part of what influences the VE map in the first place and also it effectively bakes in more tolerance for the effects of ambient pressure changes and also general outside influences on the tune (such as transient conditions caused by what the external wastegate is doing etc, can be very interesting looking at that ratio when the gate cracks). That is definitely a popular choice for serious hillclimb cars (like Pikes peak levels of altitude change) fwiw, where it isn't just ambient pressure on the intake side that changes for a given throttle angle but with turbo cars the EMAP will go higher and higher for a given manifold pressure target which can cause serious tune drift for something just focussing on intake air density for the fuel model.

Yeah don't get me wrong, AlphaN I generally view of as kindof a "necessary evil" in almost all the cases where I have used it. As you say, where there is unmetered load changes things can get a bit tricky. For me personally, "throttle based load" systems are best done when you can control the throttle with the ECU. The most recent Alpha-N setup I tuned was a Toyota MR-S race car running a Honda K20A with E-throttle on a MaxxECU, and that works great. The big thing is idle control is done via the ECU controlling the throttle, so you (so long as the tune is accurate) have very fine load updates when idle load changes. As a lot of the things you have mentioned come down to, it will only work as well as the tuner and setup allow - a lot of these things introduce compromises, extra effort etc and really like everything when modifying cars you have to consider what is going to best suit the application. Another good point you raise and one thing I've not really mentioned publicly about a lot of my tuning is that (depending on the application) I've often used estimated mass flow type values for axis on load and AFR tables then if there is anything dealing with temperature swings then that will be done with extra adjustment. It makes AFR target tables (and traces through a pull depending on how you've done it) as well as ignition timing tables look quite different but potentially quite a bit more intuitive - like all things though, this kind of thing relies highly on the work you've put into it being accurate and complete. One of my my mates finished a KP Starlet build a couple of years ago and has mega fussy standards overall and he wanted something that was going to be a mix of oldschool raw but also "sorted" so cold starts, driveability etc etc were like clockwork. Like it had to be raw, but refined, and runs a Link ECU. We had many yarns about how to do go about it hardware wise and while the ECU isn't necessarily the best suited to it, I decided to try wrestling into doing things I'd do with a MoTEC or whatever and basically tuned it with two MAP compensated AlphaN VE maps which blended between based off the airflow error between the minimum and maximum request idle air valve work and did the ignition table based off the calculated cyl filling. I'm not saying this is a great idea or anything, buuuuut the car does exactly what he wanted. It's economical, starts and drives better than a lot of factory cars despite having ~280deg cams and ITBs on a nearly 40 year old base engine so I'd argue that one way or another it's a combination which "can do the job". It has no wideband (lots of wires and obvious sensors partly not in fitting of the feel of the car - cool wee car actually: Toyota Starlet | Kelford Cams) yet he has done road trips all around NZ in it covering a variety of altitudes etc with zero issues in terms of shitty running or anything so it can be done even with a crappy old Link ECU. Throttle response is pretty electric, nothing stupid happens, you would not want a thing like this to be with an AFM only load input for all kinds of reasons. Like everything, it partly relies on how much work you want to do to get it "right" and how well you understand an define things. Your comment on how non-linear the relationship between MAP and actual cylinder fill is when you're "in vacuum" is a whole other wild can of worms haha. I fully agree, I feel like you can often tell if someone who has tuned a purely manifold pressure based speed density tune understands (or at least is as OCD as I am) about a lot of the fundamentals of this kind of thing when you look at a VE map. This whole yarn really makes me think of a rant Paul Yaw (Mr Injector Dynamics) had years ago and is very relevant to especially this part of the conversation - if you haven't read it then this may be of interest: That Big Orange Heavy Thing | Injector Dynamics. The relevant bit is "Math doesn't suck" and check it out if you're in an environment where you won't get awkward questions about looking at a webpage with pics of sexy school teachers on it. One way or another it's worth a look. Nice I did ask before but still curious what the specific ITB turbo idiosyncrasies you're talking about? Another thing on the topic of speed density, ever tried IMAP/EMAP based load?

Is that after the initial TMF implementation? I had wondered how well that worked for the same reason @joshuaho96 mentioned - the impression I had from others is it basically used measured pressure drop across the throttle, but I wasn't certain that you'd get a reliable reading post-throttle in all situations. I don't really know what it was (or is) now so treat the whole thing like I need to really know more about it - definitely consider anything I say on this bit as conjecture I have been told the current Emtron setup works well.

Talking about TMF?: I am talking about something along those lines, yes - though I assume you are talking about Emtron's TMF specifically? That is one implementation of a speed density system that happens to use throttle as an input but I wasn't talking about their implementation. In terms of the the pressure ratio across the throttle body concern, yeah I'd "day dreamed" about alternative ideas for determining airflow and had pondered on pressure across a throttle and ruled it out in my head because of that exact reason. I've never used Emtron, let alone their TMF so I don't have a great understanding of how it works or how well it works so I can't really comment on it in context of that. How many cars use "TMF" style speed density and how well it works: I don't think the E9x series BMWs use it though I'm not 100% sure. And to be clear, I am far from claiming I am any authority on these things - much of it is what I remember from conversations over the years with people much smarter than myself so I'm kinda forwarding on my patchy recollection of how I interpreted what I was told about things. In terms of how well it works, I feel like I already said that from what I understand the new Porsche's use this kind of system. Do you doubt the 991 Series Porsches work well? I've only been in a single 991.2 Turbo S and it went like a bat out of hell, but it very much felt sorted beyond "only WOT" type driving by my personal gauge. Super super competent car all round. Like almost too well behaved. Not a fan of Alpha-N/MAP strategies: Can you elaborate? They can be a headfcuk to deal with but I'm not sure they are broken as such. I definitely prefer the concept of pre-throttle pressure vs throttle angle versus an engine flow characterisation map and feel like that's probably the best answer though am not aware of an aftermarket ECU offering that. Yet. Now for the "my view of the world" ramble, again I am no expert so more than happy to be picked apart on this if there is stuff you (or anyone) knows beyond me so this is just my take and limited experience on this general topic. Please excuse any terrible wording or thinking with this, its been a long day at work and if I were wiser I'd write this when my brain wasn't already done - but it's a fun topic so I'm doing it immediately What I've gathered about at least the 991 series Porsches they use a combination of a boost sensor and throttle area vs angle calibration, though I could be wrong - am definitely riffing off bits and pieces I've been told. I *think* it's the 991.1 that has just a pre-throttle pressure sensor and the 991.2 has one on both sides (the post throttle one being more for diagnostic purposes ?!) - I'm guessing from that there are possibly a bit more like how the Motec R35 GT-R package does things, where it uses pre-throttle pressure and throttle opening vs flow data and engine efficiency data to estimate manifold pressure on the other side of the throttle. So if you think of an Emtron which (if I understand correctly anyway) is solving for mass flow using pre-throttle pressure, post throttle pressure and throttle angle - these guys are effectively solving for MAP by using pre-throttle pressure, throttle angle data and engine flow data. I could be wrong, but if it's anything like that then in my head it's going to get around the situation where there isn't a large pressure differential across the butterfly, but also creates a reasonable amount of calibration work to make it work right. In that sense it makes MAF a no brainer for the K.I.S.S philosophy, but then you were earlier criticising how limiting standalones are vs OEM ECUs. The joy of modern OEMs (and high end stand alones like Motec M1s) is there is a fcuk tonne of calibration to be done to make it work right but if you do then you get something that is super consistent and responsive to transient conditions. I believe much of the reason that the Motec M1 (and I assume modern Porsche ECUs) do this kind of thing is there is a latency between what the MAF is reading and what the engine is actually receiving. I hope this kinda makes as much sense as it can and it doesn't end up looking like wordsalad when I read it tomorrow after a good night sleep.