25 Bottom End

[mjscar]

Hey guys,

I don't really know where to post this but anyways, I was just wondering if you guys could shed some light on the difference, other than the compression rate (and if any other), between the 25t and 25 N/A bottom end. I've been trying to look around for this information on the net and site, but I can't seem to find any.

Anyways yeh just wanted to know this info because I want to turbo my 25 N/A next month so I just want to see whether the 25 N/A bottom end is any weaker than the 25t bottom end.

Thanks guys,

mjscar

[Eug]

strength wise there's no difference. however the compression ratio will affect how much boost you can run.

see the turbo charging thread in this section for more details on turbo'ing your NA, alot of guys have done it and all the info you need are in those threads.

p.s. - that pic of clarkson is a bit creepy no?

[GTS4WD]

Oil and coolent lines?

lol.. isnt he talking about some Dutch car?.. something about drugs?

[mjscar]

strength wise there's no difference. however the compression ratio will affect how much boost you can run.

see the turbo charging thread in this section for more details on turbo'ing your NA, alot of guys have done it and all the info you need are in those threads.

p.s. - that pic of clarkson is a bit creepy no?

Yeh I've read the whole "how to turbo your N/A" thread, but it never mentioned the strength of the bottom end so I was just wondering whether there was any difference or not.

While on topic, generally speaking, is there a way to determine how much boost you can have at a certain amount of compression rate? Like most of the guys on that thread are using stock turbo and so are sticking to ~7-8 psi. But I was wondering, most guys with the 25t just change turbo and a few supporting parts (injectors, fuel pumps etc etc) and just up the boost to 17-18psi on stock internals.

Since both 25 have the same strength, if I use all the same bolt-on parts as the guy on the 25t, does that mean my N/A engine can now withstand 10-12psi on the stock internals instead of the usual 7-8psi? Or is everyone running 7-8psi because if we boost it up any higher, irregardless of whether we upgrade the supporting parts or not, will just blow up the engine?

Because at the moment, I'm not sure whether to turbo it with better parts and hopefully get a lot more power, or just use 2nd hand gtst parts to turbo my car.

Hope all that makes sense :S. But anyways, Thanks a lot for your help!

p.s. Hahaha gotta love the ingenious Clarkson

[SHANE666]

LOL @ JC pic.

[Eug]

is there a way to determine how much boost you can have at a certain amount of compression rate?

comes down to the tuner and his tune.

Like most of the guys on that thread are using stock turbo and so are sticking to ~7-8 psi. But I was wondering, most guys with the 25t just change turbo and a few supporting parts (injectors, fuel pumps etc etc) and just up the boost to 17-18psi on stock internals.

i already told you that the compression ratio will dictate largely how much boost you can run. by your above sentence it's apparent that you do not know about compression ratios and how to calculate them.

the 'bolt ons' you mentioned above such as injectors, fuel pumps, etc. may increase the amount of boost you can run slightly, but it again comes down to the tuner.

17-18psi with high compression??? it's definitely do-able, but not without some really really good fuel and a really really good tuner.

i suggest you do some reading up on compression ratios, how to calculate them and what engine parts dictate them.

like i said before, strength wise they are the same - but the differing compression ratios between the rb25de and the rb25det will affect the boost pressure you are able to run.

way easier to buy an rb25det and bolt that in.

Since both 25 have the same strength, if I use all the same bolt-on parts as the guy on the 25t, does that mean my N/A engine can now withstand 10-12psi on the stock internals instead of the usual 7-8psi?

read above

Or is everyone running 7-8psi because if we boost it up any higher, irregardless of whether we upgrade the supporting parts or not, will just blow up the engine?

read above

if you really want that much boost buy an rb25det. why do you want to run so much boost anyway? it seems you're just chasing a number.

i'll state it again, go and do some proper research and learn more about compression ratios, boost pressures and how engines work. then you will be able to post some questions which don't make you look silly.

[mjscar]

comes down to the tuner and his tune.

i already told you that the compression ratio will dictate largely how much boost you can run. by your above sentence it's apparent that you do not know about compression ratios and how to calculate them.

the 'bolt ons' you mentioned above such as injectors, fuel pumps, etc. may increase the amount of boost you can run slightly, but it again comes down to the tuner.

17-18psi with high compression??? it's definitely do-able, but not without some really really good fuel and a really really good tuner.

i suggest you do some reading up on compression ratios, how to calculate them and what engine parts dictate them.

like i said before, strength wise they are the same - but the differing compression ratios between the rb25de and the rb25det will affect the boost pressure you are able to run.

way easier to buy an rb25det and bolt that in.

read above

read above

if you really want that much boost buy an rb25det. why do you want to run so much boost anyway? it seems you're just chasing a number.

i'll state it again, go and do some proper research and learn more about compression ratios, boost pressures and how engines work. then you will be able to post some questions which don't make you look silly.

Ok I think we have misunderstood each other. I know how to calculate the compression ratio and I know that it has nothing to do with bolt on stuff such fuel pumps and injectors and etc etc. I know that none of these stuff will affect the compression rate whatsoever.

However, what I am getting at is, are people who are running 7~8psi doing so because they can't get enough fuel and etc etc so that they have to run lower psi, or is is this amount of boost (with the high compression rate) the max you can run simply because the engine is at its maximum strength?

Basically, I'm not asking whether bolt-on stuff will change the compression rate. I'm asking whether bolt-on stuff will give us the ability to push the enginer further, closer to its maximum strength, or not. OR is it already at it's maximum at this amount of boost.

Look I'm not trying to chase some magical number here. I just want to know whether it is worth it to spend $5000+ on it, or just do what everyone did and get 2nd hand parts for $3000 and get the same amount of power. Because if I'm getting the same amount of power, I will gladly spend the extra money on other things.

And to be honest, this is my first time I'm going to do something as big as this so forgive me if I have silly questions. I have been researching this for over a year because I had to save up the money in the first place. However, no matter how much you research, there are questions that are not answered in magazines, in forums, on the net (mostly because they talk about the rb25det). Questions that can only be answered by experience, which obviously I do not have. So sorry for my "noobness" but please don't accuse me of not knowing anything about engines. I would not be doing something like this if I had no idea on something as basic as "What affects compression rate".

Thank you,

-mjscar

Oh btw, when I said 17-18psi, I meant on a turbo engine with stock internals. I was just wondering that if they can push a turbo engine this far, how far can we push an N/A turboed engine with the same amount of (ONLY) bolt-on parts. That's all

Edited May 16, 2008 by mjscar

[Eug]

However, what I am getting at is, are people who are running 7~8psi doing so because they can't get enough fuel and etc etc so that they have to run lower psi, or is is this amount of boost (with the high compression rate) the max you can run simply because the engine is at its maximum strength?

it's a fuel quality/tune issue not a strength and/or supply thing. high compression = pinging, plus the high boost = more pinging

you will damage any engine regardless of strength with pinging.

Basically, I'm not asking whether bolt-on stuff will change the compression rate. I'm asking whether bolt-on stuff will give us the ability to push the enginer further, closer to its maximum strength, or not. OR is it already at it's maximum at this amount of boost.

as i said before the limiting factor is the quality of the fuel (and it's tune) not the ability to supply fuel. however that's not to say it's impossible. with any high compression/force induced system reliability (and a very good tune!) would want to be high on the list.

Look I'm not trying to chase some magical number here. I just want to know whether it is worth it to spend $5000+ on it, or just do what everyone did and get 2nd hand parts for $3000 and get the same amount of power. Because if I'm getting the same amount of power, I will gladly spend the extra money on other things.

'worth' isn't a really definitive term. the questions to ask would be how far do you want to go? and how important is it to you?

i think once you pass a certain threshold (what this is no one can tell you) the low compression engine will have far more potential to get more power. people don't normally go down this path as the RB25DET is a proven formula. it costs alot of money to be different now-a-days, if you crave the response (which i personally see as the only reason to go high compression/boost) a supercharger might be a good alternative.

And to be honest, this is my first time I'm going to do something as big as this so forgive me if I have silly questions. I have been researching this for over a year because I had to save up the money in the first place. However, no matter how much you research, there are questions that are not answered in magazines, in forums, on the net (mostly because they talk about the rb25det). Questions that can only be answered by experience, which obviously I do not have. So sorry for my "noobness" but please don't accuse me of not knowing anything about engines. I would not be doing something like this if I had no idea on something as basic as "What affects compression rate".

sorry if i came off a little judgmental. i'm just trying to be realistic here as quite often we get dreamers who think way ahead of themselves. however don't let my realism discourage you, it will help you critically think and assess all options before sinking too much money in. by all means if you think you can do it then do it - it is after all your car.

Oh btw, when I said 17-18psi, I meant on a turbo engine with stock internals. I was just wondering that if they can push a turbo engine this far, how far can we push an N/A turboed engine with the same amount of (ONLY) bolt-on parts. That's all

VERY RARELY will you hear of stock RB engines taking those kinds of boost levels (17~18 psi) reliably. 10~12 psi would be pushing the stock turbo, anymore and you start to see failure. exhaust wheel failure is ok, compressor wheel failure obviously a big no no.

since we are on the topic of internals let me just say that there are too many factors which contribute to piston, rod, crank, bearing failure, etc. have a look at what power levels people start rebuilding with forged items, that's a good starting point.

if your internals are up to par the 'weak point' just shifts over to the next component. both high compression and high boost are the main culprits for exposing the weak links within an engine

[mjscar]

it's a fuel quality/tune issue not a strength and/or supply thing. high compression = pinging, plus the high boost = more pinging

you will damage any engine regardless of strength with pinging.

as i said before the limiting factor is the quality of the fuel (and it's tune) not the ability to supply fuel. however that's not to say it's impossible. with any high compression/force induced system reliability (and a very good tune!) would want to be high on the list.

Thanks for that. This is basically what I wanted to find out, what the limiting factor was for people going only a certain amount of boost.

'worth' isn't a really definitive term. the questions to ask would be how far do you want to go? and how important is it to you?

i think once you pass a certain threshold (what this is no one can tell you) the low compression engine will have far more potential to get more power. people don't normally go down this path as the RB25DET is a proven formula. it costs alot of money to be different now-a-days, if you crave the response (which i personally see as the only reason to go high compression/boost) a supercharger might be a good alternative.

How far do I want to go? Well to be honest, as far as I can go with what I currently have in hand. That's basically why I've been asking about the limiting factor of people only doing a certain amount of boost because if I there is a certain "fixable" factor that can be fixed, then I will fix it if I have the money to do so. Obviously the limiting factor isn't really "fixable" so now I can have a more realistic expectation of what can be achieved from the engine and therefore will spend an amount of money that I believe is "worth" the results.

Also I agree that the RB25DET would be the better, sensible path to take. But to be honest, I want to see how I can better what I have rather than just chuck it away and start from fresh. Its probably a stupid trait I have, and I'll concede it has got me into some stuff that wasn't worth the effort, but I'm going to stick to it and see where it will lead me.

sorry if i came off a little judgmental. i'm just trying to be realistic here as quite often we get dreamers who think way ahead of themselves. however don't let my realism discourage you, it will help you critically think and assess all options before sinking too much money in. by all means if you think you can do it then do it - it is after all your car.

Realisticlly speaking, I will probably (more like most definately) have one hell of a long time trying to bolt the turbo on and getting it to work. However, it will also be one of the best times when things finally go on right, and also, what better way is there to gain experience than to just dive in and do it. My car will probably be off the road for a while, but hopefully with the help of my mechanic friends, I can get it to work.

VERY RARELY will you hear of stock RB engines taking those kinds of boost levels (17~18 psi) reliably. 10~12 psi would be pushing the stock turbo, anymore and you start to see failure. exhaust wheel failure is ok, compressor wheel failure obviously a big no no.

since we are on the topic of internals let me just say that there are too many factors which contribute to piston, rod, crank, bearing failure, etc. have a look at what power levels people start rebuilding with forged items, that's a good starting point.

if your internals are up to par the 'weak point' just shifts over to the next component. both high compression and high boost are the main culprits for exposing the weak links within an engine

What I meant was a stock RB engine with upgraded bolt-on parts (turbo, injectors, ecu, etc etc) running 17~18psi.

Also I understand what you are saying about the internals. I guess what I fail to realise is that the engine was not built perfectly and so there will always be a weak point in the engine (even if its a minor one) that will lead to the failure of the whole engine.

Let me just say, Eug, thank you for taking to the time to reply to all my posts. I know that sometimes, my head churns out questions that are pretty much "overthought", and it is hard for me to transfer what I am thinking to what I am writing.

But anyways, thanks for being patience with me dude. Really, trully appreciate it.

[Eug]

I've been asking about the limiting factor of people only doing a certain amount of boost because if I there is a certain "fixable" factor that can be fixed, then I will fix it if I have the money to do so. Obviously the limiting factor isn't really "fixable" so now I can have a more realistic expectation of what can be achieved from the engine and therefore will spend an amount of money that I believe is "worth" the results.

spot on. however a project like this you will need to decide early on the tuner and his/her ecu of preference. then you will need to sit down with the tuner and the mechanic and discuss on the target compression and boost levels you want to run. each person brings something different to the table.

tuner: the quality of fuel, how much compression, how much boost, ecu flexibility

mechanic: what turbo to match, what needs to be upgraded

you: cost and target

as you can see it's not a single limiting factor, if you want to run high comp/high boost then fuel quality needs to be high. however you can sacrifice high comp for low boost, or alternatively low comp for high boost.

it's all a dynamic package and one needs to compromise for another. however a general rule of thumb in a high comp/boost application is usually fuel quality which affects the tuners ability to do his job.

Also I agree that the RB25DET would be the better, sensible path to take. But to be honest, I want to see how I can better what I have rather than just chuck it away and start from fresh. Its probably a stupid trait I have, and I'll concede it has got me into some stuff that wasn't worth the effort, but I'm going to stick to it and see where it will lead me.

we all live and learn. you can come away from it as a pioneer with an awesome piece of gear or you could come away from it with an empty wallet and starting back from scratch.

what better way is there to gain experience than to just dive in and do it.

got to love it!!!

What I meant was a stock RB engine with upgraded bolt-on parts (turbo, injectors, ecu, etc etc) running 17~18psi.

have a look at this thread: http://www.skylinesaustralia.com/forums/Rb...html&hl=gcg

they are all the RB-DET guys. you might be able to get some idea on the boost levels they are running on stock bottom ends with simple bolt ons. yes there are guys running 17~18 psi with bolt on turbos with low compression, not sure if you'd be able to get that high without a good tuner and fuel.

Let me just say, Eug, thank you for taking to the time to reply to all my posts. I know that sometimes, my head churns out questions that are pretty much "overthought", and it is hard for me to transfer what I am thinking to what I am writing.

But anyways, thanks for being patience with me dude. Really, trully appreciate it.

no dramas.

my personal suggestion.

1. set a budget otherwise a project like this will blow out of proportion.

2. find a really good tuner first, talk to them with about what you want to do and how you want to do it. find their recommendations (ecu, compression, etc.) see where you can compromise and where you cant

3. find a mechanic and work out what's do-able

[Warpspeed]

Hey guys,

I don't really know where to post this but anyways, I was just wondering if you guys could shed some light on the difference, other than the compression rate (and if any other), between the 25t and 25 N/A bottom end. I've been trying to look around for this information on the net and site, but I can't seem to find any.

mjscar

Strength wise, no different. They are built from fundamentally all the same major parts, but there are some differences.

RB25DET has oil squirters RB25DE does not

RB25DET has larger oil pump (to feed the turbo).

RB25DET has extra water and oil connections for turbo fitted to engine block.

RB25DET has lower compression pistons.

RB25DET has stronger clutch.

How much power?

How much safety are you prepared to compromnise.

How much engine life are you prepared to compromise.

Tell me how big I can SAFELY blow up a balloon without it bursting, and I will tell you how much extra power you can get from a turbo RB25DE (safely) before it blows up. There is no definite answer to either question, it is a judgement call, and how much risk you are prepared to take in doing this?

If it lasts six months then cracks a piston would that be o/k?

Some people might be perfectly happy with that, because it went like an absolute rocket for six months. Others might not be too pleased about having to pay for a complete engine rebuild.

If it s running very close to detonation, and you get a load of bad fuel, or the ignition timing moves slightly, it could cost you an engine. That is the problem with pushing things to the absolute limit, especially when you cannot be really sure where the limit is.

Edited May 26, 2008 by Warpspeed