Hks Gt-rs Turbo Analysis For Rb-25 Engine

[sl33py]

Nah, I'm talking about the fact that noone would run a 2835 at much less than 16-17PSI (someone tell me if I'm wrong here), because it's out of it's ideal band of operation, so the data below that area is kinda useless information.

300 RWKW using the GT-RS

That is one of the ppl I PMed (Al, I think, cbf going and checking), he had cams and a buttload of other mods. It's not "too high", it's correct. But yeah, kind of useless to the dataset since you're not including that kind of data.

Don't worry, you're gonna have a ball of a time with ur new turbo, as I should next week too Hope you've got all the supporting mods so it can really do it's best - ~280rwkw. I'm looking at about 250-260rwkw with mine.

[Turbz RB-25]

Nah, I'm talking about the fact that noone would run a 2835 at much less than 16-17PSI (someone tell me if I'm wrong here), because it's out of it's ideal band of operation, so the data below that area is kinda useless information.

That is one of the ppl I PMed (Al, I think, cbf going and checking), he had cams and a buttload of other mods. It's not "too high", it's correct. But yeah, kind of useless to the dataset since you're not including that kind of data.

Don't worry, you're gonna have a ball of a time with ur new turbo, as I should next week too Hope you've got all the supporting mods so it can really do it's best - ~280rwkw. I'm looking at about 250-260rwkw with mine.

280 RWKW!

Mate, I'm hoping for 260rwkw at 18 PSI. If I get anything above 260rwkw I'd be over the moon!!

So what boost are you going to run with your GT-RS, 17-18?

18 PSI should get my turbo going good, shouldn't it?

In your opinion sl33py, what's the safe threashold for standard RB-25 internals?

Some people said 250 rwkw, others say 300 rwkw, big difference if you ask me?

[sl33py]

YGPM lol

[Turbz RB-25]

It's not "too high", it's correct. But yeah, kind of useless to the dataset since you're not including that kind of data.

Well, it is too high to include in the data set, he's the only one who's obtained over 300 rwkw (with the GT-RS), thus, being an outlier. That is why I'm not going to include it in the data because it will distort it.

Edited April 2, 2008 by Turbz RB-25

[Turbz RB-25]

YGPM lol

And 'YGPM' means...??

[Sydneykid]

Personally I don't think boost has anything to do with horsepower. So any table linking the 2 is pretty much useless. I can't speak of personal experience with GTRS's, but I certainly can with regard to GCG ball bearing high flows. A simple example, we have made 250 rwkw at 19psi and 265 rwkw at 17 psi and 275 rwkw at 18 psi. The difference? What else is done to the engine (cams, head work, valves etc), what fuel it runs on (all pump fuel) and how it is tuned.

I know I am being repetitive but........airflow makes horsepower, boost is simply a measure of restriction to airflow.

Cheers

Gary

[Turbz RB-25]

Personally I don't think boost has anything to do with horsepower.

.... Is that a joke?

Correct me if I'm wrong, but doesn't winding up the boost, thus, increase air flow the turbo produces, increase your horsepower??

[Turbz RB-25]

A simple example, we have made 250 rwkw at 19psi and 265 rwkw at 17 psi and 275 rwkw at 18 psi. The difference? What else is done to the engine (cams, head work, valves etc), what fuel it runs on (all pump fuel) and how it is tuned.

Of course horsepower is dependant on the car setup, and this was acknowledged before making the table (refer to first post- use ONLY as a rough guide as each car is different i.e different computer setup, different exhaust setup, some have cams, some don't, different tune etc etc etc)

Surely this is not to say however that more boost doesn't increase horsepower???

[sl33py]

Thanks SK, ever knowledgeabe

Nah he's serious Turboz, boost is just a measure of how hard you're having to work to overcome the flow restriction of the engine. In a perfect world you would have very low boost or none (spelt: 'cubic inches' lol). There are engines whose design flow air really well and have unusually low boost levels to get the same amount of power as others who have to really crank it to get as much power (using the same turbo). And as SK said, the other things which REALLY change it are the tuning and other work etc etc.

Edited April 3, 2008 by sl33py

[Turbz RB-25]

Thanks SK, ever knowledgeabe

Nah he's serious Turboz, boost is just a measure of how hard you're having to work to overcome the flow restriction of the engine.

Please do explain this to me further.

I was under the impression that boost (PSI) is the amount of pressure the turbo is producing and sending to the engine? Correct me if I'm wrong, please, I would love to learn more.

So your saying that a tune, cams and other supporting mods, would produce more power gain compared to winding up the boost from 10 PSI to 20 PSI?

[sl33py]

I'm not the best to explain that stuff... somoene else? Check out the FAQ at the top of this section... there's heaps of reading. BTW, YGPM means 'you've got PM' (I sent you one).

[Ionos]

Perfect example of what SK is saying - aftermarket cams. Bigger cams increase airflow by allowing the engine to breath better, therefore for the same or even less boost you make more power. If you're still not sure, think about blowing air through a straw, then blowing air through a short piece of garden hose. You wont have to work anywhere near as hard to blow air through the garden hose, yet you'll be blowing more air through it because it has less restrictions. In the case of the straw, you're probably applying a few PSI worth of pressure yet you'll be moving less air because of the restriction.

All that said, for a standard setup (unopened engine, no cams) measuring PSI vs HP for a given turbo can still be fairly useful as an indication of what power to expect, assuming basic mods (intercooler, 3" exhaust).

Edited April 3, 2008 by Ionos

[Sydneykid]

Please do explain this to me further.

No problem

I was under the impression that boost (PSI) is the amount of pressure the turbo is producing and sending to the engine? Correct me if I'm wrong, please, I would love to learn more.

Half right. Boost is simply a measurement expression of pressure, pressure is created when you have airflow and a restriction to that airflow. So you can increase the pressure (boost) by either increasing the airflow OR increasing the restriction. Conversely, you can decrease the pressure (boost) by either decreasing the airflow OR decreasing the restriction. Keep that in mind.

So if I have a car with lots of restrictions, small pipework, restrictive intercooler, low lift & duration cams, small valves, tiny ports, poor exhaust manifold, small diameter exhaust pipes, compliance cat, quiet muffler etc etc and so it needs lots of pressure (boost) to push the airflow through those restrictions. It makes say 220 rwkw at 19 psi on an average tune using 98 ron fuel. I remove some of those restrictions, better pipepwork, decent FMIC, high flow cat & exhaust etc and stick 100 ron fuel in it and tune it properly. I could easily get 230 rwkw at 16 psi. Less boost and more power.

Why? Because I have removed some restrictions therebye allowing more airflow. It is that increased airflow that makes power, boost is irrelevant.

So your saying that a tune, cams and other supporting mods, would produce more power gain compared to winding up the boost from 10 PSI to 20 PSI?

Maybe, it depends on how many restrictions you remove. The RB25DET in the R33GTST produces more power (270 rwkw) now at 17 psi than it used to (250 rwkw) at 20 psi. Same turbo but with cams, valve springs, slightly bigger intercooler pipwork, forged pistons & rods (lighter), better ring sealing, GReddy copy inlet manifold (not a big contributor) and obviously a fresh engine. Not the least of which is a slightly more agressive tune because I know the engine internals can handle it.

I understand that you have prepared the table based on the the generalisations of FMIC, 3" exhaust etc. But not all FMIC's are the same, not all 3" exhausts are the same and most importantly an untuned Power FC on 98 ron is not the same as well tuned Power FC on 100 ron. I won't get into dyno differences, but they are a consideration none the less. Perhaps I am tainted by guys complaining to me that so and so's car with everything the same makes 10 rwkw more. Vary rarely is "everything" the same and that's the problem.

Cheers

Gary

[PM-R33]

Very true, at the end of the day you have to realise that it is airflow that makes a greater increase in power then simply adding more boost. Obviously adding more boost gives more power (as long as the turbo is in its efficiency rating), but it is no where as much as increasing airflow or taking out restrictions.

Think of a GTRS on 20psi compared to a T04Z on 20psi. Same kind of theory with twin turbo setups, you can run them on low boost pressure but because there is 2 of them you have double the airflow (think about a RB26).

Tuning plays a huge ball game here, that's why it is very hard to compare. How far has the tuner pushed the car? Is he pushing it to an absolute limit where its about to ping its head off if intake temperatures increase by just 5 degrees, or has he made it safe as so you can sit it on limiter in 40 degree weather and not ping it at all. What does the tuner think is a safe knock level? Some tuners will push a car up to a certain knock because it is still relitively safe.

What fuel are they using? 91octane, 95octane, 98octane,100octane plus? How old is the fuel, people are kidding themselves if they think when they top up with 98 octane fuel it is always 98 octane, i know of a BP here in Townsville that got done a few years ago for putting normal unleaded into the ultimate bousers.

There are to many variables that people dont list or that are unaware of. Hence why one car can make 260rwkw on 20psi on a GTRS where as others can make 290rwkw on same boost.

[paulr33]

on a side note its amazing how much power and response is locked away in the tune

i spent ages on my ign maps and you should see the car on its throttle response

its coco bananas, the car literally snaps when you open the throttle - its great

[PM-R33]

on a side note its amazing how much power and response is locked away in the tune

i spent ages on my ign maps and you should see the car on its throttle response

its coco bananas, the car literally snaps when you open the throttle - its great

Exactly right, tuning is everything in this day and age regardless of what modifications you have.

[Turbz RB-25]

No problem

Half right. Boost is simply a measurement expression of pressure, pressure is created when you have airflow and a restriction to that airflow. So you can increase the pressure (boost) by either increasing the airflow OR increasing the restriction. Conversely, you can decrease the pressure (boost) by either decreasing the airflow OR decreasing the restriction. Keep that in mind.

So if I have a car with lots of restrictions, small pipework, restrictive intercooler, low lift & duration cams, small valves, tiny ports, poor exhaust manifold, small diameter exhaust pipes, compliance cat, quiet muffler etc etc and so it needs lots of pressure (boost) to push the airflow through those restrictions. It makes say 220 rwkw at 19 psi on an average tune using 98 ron fuel. I remove some of those restrictions, better pipepwork, decent FMIC, high flow cat & exhaust etc and stick 100 ron fuel in it and tune it properly. I could easily get 230 rwkw at 16 psi. Less boost and more power.

Why? Because I have removed some restrictions therebye allowing more airflow. It is that increased airflow that makes power, boost is irrelevant.

Maybe, it depends on how many restrictions you remove. The RB25DET in the R33GTST produces more power (270 rwkw) now at 17 psi than it used to (250 rwkw) at 20 psi. Same turbo but with cams, valve springs, slightly bigger intercooler pipwork, forged pistons & rods (lighter), better ring sealing, GReddy copy inlet manifold (not a big contributor) and obviously a fresh engine. Not the least of which is a slightly more agressive tune because I know the engine internals can handle it.

I understand that you have prepared the table based on the the generalisations of FMIC, 3" exhaust etc. But not all FMIC's are the same, not all 3" exhausts are the same and most importantly an untuned Power FC on 98 ron is not the same as well tuned Power FC on 100 ron. I won't get into dyno differences, but they are a consideration none the less. Perhaps I am tainted by guys complaining to me that so and so's car with everything the same makes 10 rwkw more. Vary rarely is "everything" the same and that's the problem.

Cheers

Gary

Damn good explanation.

I think you just threw me off a little when you said 'I personally think that boost has nothing to do with horsepower'.

In the post above you admitted it does. I understand now that you can get more power by lessening restrictions and lowering boost at the same time, but boost still does increase power.

Thanks for taking the time to explain the above to me!

Edited April 3, 2008 by Turbz RB-25

[Turbz RB-25]

Hi guys, I spoke to sl33py about this, and he said I should be getting at least 260 rwkw with the following mods at 18PSI:

3.5 inch straight through exhaust

GReddy Front Mount Cooler

Splitfire coil packs

Pod with customs cold air intake and heat shield

Bosch 044 Fuel pump

Z32 AFM

HKS GT2835 Pro S

Nismo 555cc injectors

Power FC

S.K, I am interested in your opinion.

Do you think I should hit 260rwkw at 18PSI on a safe tune?

And in your opinion, will this power be safe with my stock engine/internals?

Cheers

Edited April 3, 2008 by Turbz RB-25

[PM-R33]

Yep definetely will get that power, my tune is safe as all hell and im making that much power with a GTRS, so with a 2835 you should be fine, if not making more than that.

Edited April 3, 2008 by PM-R33

[rev210]

I've had a habit of tuning (properly) on lower boost with my cars as a base line for some time now. This is especially the case when I upgrade cams as the improvements to cam timing can be easily missed if the tuner assumes things about boost setting.

Upgraded cams as mentioned have an effect on flow restriction and I've found that rather than bashing in identical boost to the last setup right off , running substancially less than before and gradually bringing it up finds the best tune. As Sydneykid's examples seem to indicate. Dialing cams in at lower boost is a must do I reckon.