Rolls

No doubt, I just want to know what will happen. I'm not talking about taking it down to zero, I'm talking about taking it down to say -20mmhg or greater, eg creating a vacuum and literally sucking the exhaust out, not making it zero restriction, creating the opposite of a restriction.

What is the advantage of this over an rb30 with oversized pistons?

Assuming the BOV opens up when you do this would probably be a very effective pre spool!

There are actually companies researching using compressed air as a way of storing energy in a hybrid system.

Be worth dropping it off to ATS to get him to pull it apart and inspect then, Bill is a champ and would do it for cheap no doubt, really knows his stuff as well.

We should kiss now.

Pre ignition pressures don't necessarily directly correlate to combustion pressures though. As if you have really high back pressure you will have poor scavenging, more exhaust gas and less air in the cylinder when the valve closes, same pressure (I think?) but less air+fuel so lower combustion pressure. 20psi with a large turbo is more air than 20psi with a small turbo, yes the pressure is the same in the intake manifold, but the 20psi found with a larger turbo will be much higher combustion pressure as there would be much more air being trapped in the cylinder, hence bigger bang. The 20psi with a larger turbo will also be a much cooler intake temperature which as can be seen in your formula will also increase the combustion pressure. Can you see why I'm saying the boost measured by your boost gauge might as well be irrelevant as far as knowing if it is the cause of your blown ringlands? As with a larger turbo you decrease back pressure (decreasing intake temps, increasing VE) you also run the compressor more efficiently also decreasing intake temps so for the same given boost pressure you are flowing more air, hence when the valve shuts more air (less exhaust gas) is trapped in the cylinder (more air mass) hence higher combustion pressures. I get what you are saying but combustion pressures are what is important, not pre-ignition pressures. Hence what he needs to look at is ignition timing being run and how much airmass he is burning, eg has he reached the limit of what the pistons can handle combustion pressure wise (via det or just purely exceeding the torque levels that the pistons are designed for) not what boost the turbo is running. So yeah what you said is correct but I don't really think it is relevant here, I guess I am just trying to show why what boost pressure he was running is not the issue, it is whether he was experiencing detonation or just simply exceeding the max torque the pistons/ring combo were designed for.

260rwkw on rb25 injectors with standard rail pressure? It could be possible but in most cases I doubt it, you must be making that power at quite high rpm with low torque figures as it is generally the peak torque figure and AFR that dictates how much injector you need. Would also be quite lean maybe 12:1. Everyone I've spoken to sees stock 25 injectors maxing out at ~220-230kw, personally I am making 240kw and I am getting GTR injectors to almost 80% doing that on 18psi, I have the motor tuned very rich though, 10.5 - 11:1 at peak torque. My bad I thought I read chrome wheels lol.

If you can prove you bought it off him, eg you got him to write you a receipt (good practice to do this on anything over $500) then you could technically take him to court and get your money back.

the emblem on the cam cover looks sexy as!

Yeah I wasn't actually proposing anyone build this, was more just interested in what effect creating negative backpressure would have on an engine and how much energy would be required to do so. It is always interesting to discuss things like this as they enhance your understanding of how it all works and keep you thinking. Negative posts that don't even raise any points about the idea serve to just discourage people from thinking about new ideas, in reality the more people you think actively thinking about things like this higher the chance someone will come up with an actual working idea that can benefit people. Mafia seems to really like posts like this, hell even when people are asking genuine questions (like differences between neo and s1/2 rb25) he posts bullshit like that. I like the idea of energy storage, much like the KERS system they are using in F1 and other hybrid energy drives. Would definitely be interested in how effective something like this would be as well. Another option would be to use compressed air stored up from braking etc and then using this to pre-spool the turbo when getting on the throttle. Of course it should have no issues getting rid of it, but it would help get rid of them better. If you reduce backpressure you help exhaust flow, more exhaust flow increases scavenging and helps get more air into cylinders. You can see this effect when going to a bigger hot side, you make far more power for the same boost as you have just opened up the exhaust side of the car much more. If you were to attempt to achieve the same thing via sucking the exhaust out, you could have the gains of going to a larger hot side but whilst retaining the response of a smaller hot side. It all just comes down to how much energy is required to do so, eg if it is more or less than you would gain by reducing the back pressure. if it is less then you have a net gain, eg you make more power, if it is more then you will loose power. Get what I mean? I agree that heat would certainly be an issue, but what if you use a centrifugal design, eg like the compressor on a turbo, there is only one moving part so tolerances are not as big an issue (just look at the rear end of a turbo, they work fine).

Lol guys this is just a thought experiement. Seriously though it would work the same way a normal supercharger works except in reverse. Instead of forcing air into the engine it would create negative exhaust back pressure causing massive scavenging which would increase VE and cause more air to get into the cylinder. You would put it post turbo, eg after it so it would suck exhaust out, would probably help with spool but mainly at higher load where backpressure is high improving top end. Being as it is a thought experiement I'd just assume it was powerful enough to suck the gas our and create negative backpressure, eg it wasn't a restriction. I'm not the first one to come up with this idea, do some googling there are quite a few discussions on the same idea. I think the main reason it would fail is it has to suck out fuel AND air, where as a charger has to only push air normally. Has to move more than twice the volume of gas so would require far more energy. Still fun to think about things like this, keeps your brain working you negative nancys. Or you could use this and get negative backpressure, that was the point, get it below zero. No you'd be assisting the exhaust stroke by sucking the exhaust out, this would aid in cylinder filling and get more air into the engine. That is just an engineering problem, you could use a shaft from the front area that runs to the end of the exhaust sucker. Mafia you are probably the most negative person I have ever met, I've never seen anyone else post such negative bullshit in threads.

Instead of a supercharger supercharging the air going into an engine what about sucking the exhaust out of an engine. You would put this post turbo on a turbocharged car as these are the type of engine that would greatly benefit from lower back pressure. Has this ever been done, would it be effective? Discuss.

Hypergear, any word on this?

Still don't really think this is the case, imo boost level is fairly irrelevant. Eg with a bigger turbo that makes the same torque at say 10psi as a small turbo does at 20psi the combustion pressure is the same isn't it. Two of the reasons why is because the bigger turbo has less back pressure causing high VE as the air can fill the cylinder faster, also the compressor is operating at a higher efficiency level hence less heat (denser air). There really are so many factors that I would go to say boost level really doesn't tell you much at all. Really need to look at the airmass that is being allowed into the cylinder. You fit more air into the same sized space and hence you get higher pressure > higher combustion pressure. Airmass is really the only factor that matters.

I don't think I'm confusing them, I am explaining how it is airflow (or more correctly airmass as you said) that dictates the combustion pressure and hence torque (I meant torque not power when I said that earlier) that can be made (what you said basically) What probably killed his motor was too high combustion pressure (once again what you also said), however this was reached I do not know, too much airflow or detonation, it isn't the boost persay as he could have reached the same combustions pressures with a much larger turbo running say 10psi. I don't really agree, sure the valves are shut but depending on how much air mass is flowing you are going to get more air in the cylinder per stoke. The boost pressure doesn't dictate how much air mass there will be as can be seen with a stock turbo running 12psi vs a TO4z running 12psi, one has shitloads more air mass than the other. If you keep the turbo the same then yes increasing boost increases combustion pressures, but if you are comparing different turbo's then it does not necessarily do so, this is all I was trying to get at with my earlier post. Look at the peak torque figures, intake temp figures, and ignition figures, not the boost number, boost number is irrelevant if you know the others. edit: Actually we were saying the same thing all along, I just misunderstood what you posted on the last page. My bad, I just get annoyed when people say you can't run more than x psi or you will pop your motor, or 'oh you cant run 20psi that will destroy it!' without knowing what turbo and hence what torque it is making, I know no one really said this, I was just ranting. Continue on! lol

Yeah but if you run 36psi it doesn't make it 1218psi, it will make it much higher! so whilst the two numbers are miles apart, it does make a big difference if there is large airflow. I guess what I was trying to say is the main factor for combustion pressure is ignition and airflow, airflow is affected by boost, but big boost doesn't necessarily mean big combustion pressures.

Just run a big intercooler, tune rich and conservative and it will not be an issue.

It is airflow + ignition which affects chamber pressures, not boost pressure, as you can push the same air with 18psi on a small turbo as you can on 6psi with a large turbo. Higher boost for the same airflow results in higher temperatures which will cause the engine to be more prone to detonation, if you need higher boost for the same airflow usually means more restrictive exhaust side as well which increases backpressure + heat which compounds detonation.

Unless you are aiming for over ~220kw and have changed to aftermarket/gtr injectors then there is no point upgrading, it will give you less tuning resolution for no good reason.

No doubt you have the tune and temps under control, these things are crucial when running big power/boost with stock pistons.

Do you ever do any grip racing simon?

If he has stock injectors and afm and hence is limited to 10-12psi then yes it sounds completely normal. My gcg highflow made 210rwkw on 12psi and 240kw on 18psi, depends on what turbo has been used and what wheels it has. Injectors, fuel pump, afm and a retune shouldn't set you back much over $1500, though if you are buying a car why not just keep looking and find something that a) makes the power you want, and b) doesn't have gay ass chromies on it.

You dont need an EBC with a stock turbo, with a free flowing exhaust and rb20 spring youll run over 10psi anyway.

Why don't you just get your money back?