Maximum Boost On -9s With Standard Headgasket And Studs.

[No Crust Racing]

Car makes a bit over 330rwkw on 22psi on e85 - R34 with 86ks and healthy comp.

Has all the usual supporting mods, big exhaust, cam gears, twin turbo pipe mod, Haltech etc.

Was considering bumping boost to 25-26psi or so for a little bit more punch, but don't know enough about how to read comp graphs to tell if there's any point. My reading of this implies that more boost won't actually equate to much additional air flow? Is that correct?

Have also heard about heads being lifted at this boost, is there any truth to that and what are the symptoms? coolant in the cylinders/oil or vice versa? I can put ARP studs in if necessary. For what it's worth, car runs very cool with oil cooler and vented bonnet and guards, oil and water temps are always very stable. I haven't seen above 85 or so deg water/oil temp and 650 deg EGT with spirited driving through the hills. Intake temps are good also.

Was also contemplating switching to those 65mm K&N pods that bolt directly onto the AFMs and running an enclosure, possibly modded to allow me to retain snorkel. This is purely a rice mod for the noise and fun factor, but is there likely to be any power loss in the real world? I do have the vspec intake temp readout on the MFD.

Edited June 9, 2016 by ActionDan

[Piggaz]

Put it on the dyno and see how you go.

[r32-25t]

boost doesn't lift heads, cylinder pressure does and 350kw seems to be that magic number as you've been informed a number of times

As for upping the boost to see more power, reading a compressor map isn't going to tell you anything. Just crank it and see what it does

Changing to pods isn't going to do anything but it's your money do as you will with it

[No Crust Racing]

I should've specified, not boost specifically, cylinder pressure.

No I have not been informed numerous times that 350 was the magical number for that, nor could I find it when searching. SAU search sucks copious cock.

I'm not looking at pods for power, just the fun factor when driving it (noise). That question was more related to any negatives I might encounter, if I can deal with heat management well enough. Something like, I ran K&Ns at that power and they collapsed, etc.

Has anyone spun up there -9s to 25-26?, again, if I could find that easily, I wouldn't ask.

Throwing on the dyno means dropping the front shaft, getting it there for a touch up tune, then seeing what happens. It costs me less in time and effort to at least see if anyone else has done it. I may find that they just shit the bed and pump bulk heat after 23-24psi, I don't know, I've never run these turbos and don't know what if any relevance the comp map has to my question.

Hence seeking the experience of others.

Edited June 9, 2016 by ActionDan

[GTSBoy]

I think you might be misreading the maps you posted. The left map is the compressor map, the right map is the turbine map. The turbine map flattens off at the sort of pressure ratios that you're talking about (2.5 and up) but those pressure ratios you're talking about are boost, not the PR over the turbine. So totally irrelevant.

Unfortunately, to read the comp map and say whether adding some more boost will result in any benefit we have to know exactly where you fall on the map now, which is not really clear. Your PR is clear enough, it's pretty much 2.5. What that means is you must be somewhere on the map to the right of the 17lb/min line on the air flow axis, otherwise you'd be surging. But the problem is knowing exactly how much air you are using to make your power.

Horrible simple maths says 330 / 0.75 / 0.75 = 586 HP. At about 10 lb/min needed per HP and divided by 2 for 2 turbos, you are in the ballpark of 29 lb/min air flow.

On the 2.5 PR line, that is right over on the right hand side of the map. Going up in PR from there takes you off the map and up to massive shaft speeds too. Even if you are not that far over to the edge of the map, say at 26-27 lb/min, then going up to 26-27 psi will take you right up to the top edge of the map.

[r32-25t]

You have been told about the 350 causewe said it in your build thread countless times before you got your car tuned.

If I can push -7s to 24psi without any issue then your -9s will be fine as well

[Dose Pipe Sutututu]

ARP studs are cheap

Changing studs (without removing the head OR cams) is also a cheap/easy process...

Just change studs and add in as much boost as possible, i.e. still no more power can be made

#e85lifey0

[No Crust Racing]

I think you might be misreading the maps you posted. The left map is the compressor map, the right map is the turbine map. The turbine map flattens off at the sort of pressure ratios that you're talking about (2.5 and up) but those pressure ratios you're talking about are boost, not the PR over the turbine. So totally irrelevant.

Unfortunately, to read the comp map and say whether adding some more boost will result in any benefit we have to know exactly where you fall on the map now, which is not really clear. Your PR is clear enough, it's pretty much 2.5. What that means is you must be somewhere on the map to the right of the 17lb/min line on the air flow axis, otherwise you'd be surging. But the problem is knowing exactly how much air you are using to make your power.

Horrible simple maths says 330 / 0.75 / 0.75 = 586 HP. At about 10 lb/min needed per HP and divided by 2 for 2 turbos, you are in the ballpark of 29 lb/min air flow.

On the 2.5 PR line, that is right over on the right hand side of the map. Going up in PR from there takes you off the map and up to massive shaft speeds too. Even if you are not that far over to the edge of the map, say at 26-27 lb/min, then going up to 26-27 psi will take you right up to the top edge of the map.

Really useful, thanks. So from that I can infer that it will "work" but with a notable increase in required shaft speed to maintain the pressure ratio for a given airflow requirement - if the engine is actually ingesting that many lbs of air per min. So, test it and see... What sort of behavior would I be looking for to know it's unhappy? I imagine I'll have more resistance to surge due to the twin turbo pipe mod, or do you mean surge differently?

You have been told about the 350 causewe said it in your build thread countless times before you got your car tuned.

If I can push -7s to 24psi without any issue then your -9s will be fine as well

Again, only relying on SAU search, but I can't see that mentioned, I tried searching for 350, head lift, head gasket etc. Happy to be proven wrong, but ultimately, even if I was told, I didn't remember, and asking the question in a more visible location isn't going to hurt anyway.

What did you make again on 24?

Edited June 9, 2016 by ActionDan

[r32-25t]

348.5

[No Crust Racing]

Nice, cams or stock?

[r32-25t]

And the money you're planing on wasting for pods I'd be putting toward a crank trigger system. They allow you to push the timing so much closer due to not having any fluctuations in the map there fore more power

[r32-25t]

Stock cams, they are a waste of money replacing them

[GTSBoy]

Really useful, thanks. So from that I can infer that it will "work" but with a notable increase in required shaft speed to maintain the pressure ratio for a given airflow requirement - if the engine is actually ingesting that many lbs of air per min. So, test it and see... What sort of behavior would I be looking for to know it's unhappy? I imagine I'll have more resistance to surge due to the twin turbo pipe mod, or do you mean surge differently?

Suck it and see has a strong element of truth because of the unknowns making it impossible to be too scientific.

More specifically answering your above questions though.....The compressor map pretty much shows where you can use the compressor. If you run off the right hand side, you are generally spinning it too fast and bad things will happen. You start to eat into the mechanical limitations on how strong the wheel itself is, and of course the efficiency drops as you go to the right of the island. You're already only at 65% at the right hand edge. Going further to the right does as you originally asked - it makes hot air.

Keep in mind one thing. Unless you do start to make hot air and actually go backwards, the intention of adding boost is to add air flow. Let's play an imaginary game. Place your operating point on the intersection of the 2.5 PR line and the 25 lb/min line. If you wind the boost up from 22 to 26 psi then your PR goes up to 2.7. But you don't go up vertically, because if you did so you would only be running more boost, not flowing more air. So you have to go up at some angle to the right. If you started at the operating point I described, then at PR 2.7 you might well end up very close to the right hand edge of the map. You also would have fallen off the efficiency island (>76%) and would probably be down in the 72% efficiency region. You'd definitely lose some potential power from that.

It gets worse. On top of all this compressor side stuff, the turbine has to be able to provide the extra power to drive the compressor. It probably can, there's probably well and truly enough power available, but on some turbos you might just end up choking the back end. This all depends so much on the total package or turbo and engine that it is even harder to say without some direct measurement (suck it and see on the dyno basically).

[Hadouken]

Yes there was one person then he sold his car because he ran a slow trap speed but was making "380" kW on -9's

[No Crust Racing]

And the money you're planing on wasting for pods I'd be putting toward a crank trigger system. They allow you to push the timing so much closer due to not having any fluctuations in the map there fore more power

And how many millions of GT-R taxed dollars is that lol

Suck it and see has a strong element of truth because of the unknowns making it impossible to be too scientific.

More specifically answering your above questions though.....The compressor map pretty much shows where you can use the compressor. If you run off the right hand side, you are generally spinning it too fast and bad things will happen. You start to eat into the mechanical limitations on how strong the wheel itself is, and of course the efficiency drops as you go to the right of the island. You're already only at 65% at the right hand edge. Going further to the right does as you originally asked - it makes hot air.

Keep in mind one thing. Unless you do start to make hot air and actually go backwards, the intention of adding boost is to add air flow. Let's play an imaginary game. Place your operating point on the intersection of the 2.5 PR line and the 25 lb/min line. If you wind the boost up from 22 to 26 psi then your PR goes up to 2.7. But you don't go up vertically, because if you did so you would only be running more boost, not flowing more air. So you have to go up at some angle to the right. If you started at the operating point I described, then at PR 2.7 you might well end up very close to the right hand edge of the map. You also would have fallen off the efficiency island (>76%) and would probably be down in the 72% efficiency region. You'd definitely lose some potential power from that.

It gets worse. On top of all this compressor side stuff, the turbine has to be able to provide the extra power to drive the compressor. It probably can, there's probably well and truly enough power available, but on some turbos you might just end up choking the back end. This all depends so much on the total package or turbo and engine that it is even harder to say without some direct measurement (suck it and see on the dyno basically).

Understood, and thanks again. So realistically with the current gear I have, all I can monitor is intake temp, maybe EGT, and that's it? given I don't have a way of measuring turbo shaft speed.

Yes there was one person then he sold his car because he ran a slow trap speed but was making "380" kW on -9's

Sorry what was that in reply to?

[r32-25t]

There are a few versions around, there was for sale on here and would have been all done for under $700, the one I got was 1,000 but requires an aftermarket balancer and there the Ross one that's 2.5k plus

[GTSBoy]

Yup, monitor those things, see if it will make more power.

Measuring exhaust manifold and dump pressures may be educational too, but that is going to quite a lot of effort. A better estimate of flywheel HP would provide some more confidence on where exactly on the compressor map you're sitting. My maths was using a big, rough 25% dyno factor. A few % either way can change things.

[No Crust Racing]

There are a few versions around, there was for sale on here and would have been all done for under $700, the one I got was 1,000 but requires an aftermarket balancer and there the Ross one that's 2.5k plus

OK Cheers.

Yup, monitor those things, see if it will make more power.

Measuring exhaust manifold and dump pressures may be educational too, but that is going to quite a lot of effort. A better estimate of flywheel HP would provide some more confidence on where exactly on the compressor map you're sitting. My maths was using a big, rough 25% dyno factor. A few % either way can change things.

Understood. and thanks for the detailed info.

Hopefully dumps should be up to task, they are the 3" HPIs into 3.5" front pipe and 3.5" all the way from there.

Has anyone else pushed -9s to this level or does everyone stop at 22 because that's where they stop making wasps.

[NISR32.5]

Mate you own a 34, buy a set of head studs and get it back on the dyno. Removing the front shaft isn't that hard and cost of the extra dyno time will be worth it. It's really stuff all cost compared to what you payed for the car and what a rebuild is worth....

[r32-25t]

I've seen another 2 that were reported as making 370s one on 98 and the other on e85