What hurts a RB25DET motor? Boost or Power

[Robo's]

Ok, i have 2 scenarios, which one is going to cause more internal damage to a RB25DET motor;

1) A smaller turbo running very high boost but producing less power or

2) A bigger turbo running less boost but producing more power

Remember both turbo's will be tuned well.

Exactly, how much boost can these motors handle or do we base it on RWKW

[bigcarl]

yeah id ld like to know the answer to this one also, my engine tuner reckons my rb25 with gt30 500hp internal wastegated turbo can handle 25psi!!! stock internals too.

[PHATR32]

i would have thought, detonation and bad/no oil would kill an engine.

steve

[LANFOH]

G'day,

I dont think the size of the turbo is what you have too worry about in regards to the damage of the engine, of course there are limitations of boost but I would be more concerned with a good tune, fuel supply and cooling to support your chosen application. I know the standard internals can support around 250rwkw you would be pushing it going much higher.

My 2c

[cameron]

The Stock headgasket are at their max at around 18psi.

The stock cast piston will melt as they cannot take this sort of heat (25psi) for too long periods and you don't want to be making mistakes while tuning because at this boost level many standard things can brake, stock valve springs aren't strong enough the standard cam's don't have high enough lift to let 25psi of air out in and out of the engine.

At 25psi you will be making a fair decent amount of power, the stock con-rods also wont handel the pressure & load on boost.

The RB25 is a strong motor for what it is but once you turn the boost up things start to go wrong.

Robo,

A bigger turbo will cause more dammage as it can physicaly flow a greater mass of air than what a smaller sized one would, eg: If you were running 18 psi through both turbo's and you got a boost spike of 23psi the smaller turbo has more chance of running out of its efficency range their for won't make much more power but a bigger turbo will keep going.

To answer you'r question, i'd would say boost, because with out boost you don't got no power but it also comes down to tuning, alot of the time this is what kills engines.

I'm sure SK will let you know what the RB25 is capable of.

[Kinks]

A smaller turbo running high boost and producing less power will be pushing fairly hot air into the motor, which makes detonation et al more likely.

I'd go for the larger turbo, less boost, more power. Part of the power gain comes from lower exhaust restriction with the bigger turbine, so don't forget that. It's probably better to push a larger volume of cooler air through the motor, ultimately more power will mean higher cylinder temps, but I'd rather be making a given figure with a bigger turbo than a small one (assuming the little one is being driven to the limit of its efficiency range).

Lag, of course, is another story

[bigcarl]

i know of a stock rb25 making 265 rwkws at 22 psi with stock head gaskit, i thought this was a good result.

[dangerous_daveo]

I've been told many a time only a poor tune and heat will kill an engine. Add that to miss treatment and revs. Technically the way it was explained to me boost wont kill an engine as such, it would just blow a gasket if anything.

[Robo's]

My situation is, i got a 2530 cheap and im running 18.4psi. Im quite impressed with the results and i wouldnt mind pushing it further as i know the HKS will push more than 18psi. Yes we are dropping down to 13.5psi above 6000rpm which tells me the turbo is ineffeicent. However i am very impressed with mid range torque this turbo is pushing and if i can get some more in it in the mid range i will try. Tuning is done on the dyno to get the A/F ratios level and of course ive always got my ear out for ping.

[bigcarl]

robos, i ran up to 20psi with my gcg 450hp turbo no probs, are you running an adjustable wastegate actuator?

[Robo's]

Yeah running an adjustable HKS actuator too hold boost, but i have screwed it up that much im wondering whether im limiting the travel the wastegate opens. I might put it in the proper position and use my bleed valve.

[race_snooze]

no fuel will kill a motor so if you lean out you will melt a piston I have seen a rb25 running a to4 with a waste gate welded in the standard manifold the car was running around 270rwkw till it melted a piston due to lack of fuel

[DaGr81]

dangerous daveo, wat do u mean by miss treatment and revs? i know here and there i do push my car to atleast 6000rpm (but never redline), because im scared of damage, now how much of this can my rb25 handle?

[dangerous_daveo]

dangerous daveo, wat do u mean by miss treatment and revs? i know here and there i do push my car to atleast 6000rpm (but never redline), because im scared of damage, now how much of this can my rb25 handle?

I mean holding it on the limiter with little to no air flow (ie cooling), it really wont like it.

[Wazz]

your main problem is fuel.. at cameron said.. running stock internals.. shit load of boost.. you'd want to thinking in the low 11's for AFR's while on boost but from wat i've heard the stock rb25 rods are only good for up to 250rwkw.. after that it comes down to how often it gets the shit reved out of it.. chuck a set of tomei pon cams in.. you'll notice a big difference all over the rev range like you see some people doin a shitload of mods.. yet there lacking power? half the time people have just ignored cam's.. but yer best bet is ask sydneykid

Warrick

[Sydneykid]

Poor tuning kills engines:cheers:

[R31Nismoid]

exactly.

Also, having a lot of power, and having the motor @ prolonged high RPM will also have an effect is the motor is not tuned very safely. Stresss on the rods is what will kill em.

[paulr33]

i remember reading heat kills engines, its better to make same power with less boost

more boost means more heat

[teejay]

timing also doesnt help so dont go bashing that cas

its better to run as little boost as possible to make the power you want, simple

but there is so much more then this... tuning, support systems such as fuel , ecu , cooler etc make the difference in the long run

i abused the hell out of my 25, it hit limiter pretty much all the time, and its still going hard.

[Roy]

Rb25s also have a higher compression ratio then RB20s and RB26s, so thats another thing that may mean ultimately you wont want to be running excessive boost.

There is always talk that HKS / Trust this and that turbos love big boost? Has anyone ever actually put an RTD / temp probe in their piping to see what the compressed air temps are?

I think you will find the 2530 is flowing all it can on an RB25 at around your current boot level. The fact that it has so much low/mid stomp, i wouldnt be too worried about running 1.4bar of boost and only reving the thing to 6,500rpm.

On the street i think your more a chance of running higher boost as really how long can you keep the thing on boost and hold onto your licence. If your nailing it for 10 minutes and wide open throttle there is no way id run more then 18psi.

LOL...i suppose its a matter of are you willing to lose an engine by leaining on it:), just keep the revs as low as possible if your going to wind more boost into it