# Most likely a stupid question



## DanD (Sep 28, 2004)

Hey i just have a quick question regarding boost pressures in skylines. What is the stock boost pressure that a skyline runs stock? What can the stock engine handle?


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## BigBlueR32 (Sep 29, 2004)

I believe that the stock boost is somewhere around 6 psi.. and stock turbos are good for about 1 bar or 14 psi... something like that.... I'm to lazy to check right now.. its late...


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## Joel (Jun 11, 2003)

depends on the turbo and whether it has the ceramic exhaust wheel and the plastic compressor wheel. A safe boost is around 12psi for a RB25DET for example


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## tougedrifter (Sep 17, 2004)

BigBlueR32 said:


> I believe that the stock boost is somewhere around 6 psi.. and stock turbos are good for about 1 bar or 14 psi... something like that.... I'm to lazy to check right now.. its late...



stock boost is 8 psi. and the block is good up to 30 pounds i believe. first thing you want to do, if you want to go faster, is upgrade the turbos to some high quality Garrett's. GT30's should do fine.


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## GTES-t (Jan 2, 2004)

Stock boost is .7 bar (~10psi). The engine can handle up to about 1.5 bar (~22psi) without upgrading to a metal headgasket and beefed up internals, and I've seen them boost 2.5 bar (~36psi) with better internals.

Now, the important thing to remember, is that you can't just crank the pressure up and assume that it will run it. The ECU is programmed with-in a range. The stock ECU can only provide enough fuel up to about 1 bar (~14psi), usually it can run it up to 1.2, but it's better to be on the safe side. The stock turbos can run up to that same pressure, but keep in mind also, if you install a larger intercooler, it takes away from that. Then you can only go up to about .8 or .9 because it has to work harder to fill the larger space.

To run anything over 1 bar, look at upgrading your AFM (or using an add on AF ratio controller), Injectors (and add on injector controller), Fuel pump and turbo. The add-on ECU components can also just be replaced by a replacement ECU (Power FC for example) or a piggyback ECU (such as Greddy eManage).

Anytime you deal with the boost pressure, you always want to make sure you have the proper amount of fuel. If you don't, it starts to run lean which will start to melt your pistons. It can also cause early detonation which can damage your rods. I would recommend at least using an Air Fuel Ratio gauge or a component that checks your Air Fuel Ratio. A more accurate check is an exhaust temp sensor, but those are expensive (requires turbo with the fitting for the sensor) and only really needed on race use cars.


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## DanD (Sep 28, 2004)

I was just wondering because everyone has a different idea on a lot of boost. I drive a DSM and I have a friend who has a turbo honda, we just got done tuning his car to 18psi and that sunday he raced an r32 with a t51r (i think) only at 1bar, which i thought wasnt much seeing as the t51r is a huge turbo where its efficientcy is probablly at like 20psi+. The good thing was he kept up with the r32 from 60-110.


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## tougedrifter (Sep 17, 2004)

DanD said:


> I was just wondering because everyone has a different idea on a lot of boost. I drive a DSM and I have a friend who has a turbo honda, we just got done tuning his car to 18psi and that sunday he raced an r32 with a t51r (i think) only at 1bar, which i thought wasnt much seeing as the t51r is a huge turbo where its efficientcy is probablly at like 20psi+. The good thing was he kept up with the r32 from 60-110.



must not have been a GT-R


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## jeong (Jul 22, 2004)

tougedrifter said:


> must not have been a GT-R


because the rb20det is an awesome combo w/ t51r


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## DanD (Sep 28, 2004)

I am pretty sure it's the fact that it's a huge turbo and low boost?


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## GTES-t (Jan 2, 2004)

It could have been a GTR, the T51R is a recommended single turbo to replace the twin turbo setup on the RB26. 

The thing with turbos, they have a max. boost pressure limit, but that's not the main thing you look at when figuring out which one to use. One of the most important things you have to figure out is it's best RPM operating range for the engine you have. You have to decide if you have one that spools up quick, but then can be running out of it's efficiency range before the higher RPMs. Or you could have one that is slow to boost in low RPMs, but is in it's prime efficiency point in the higher RPMs. Or a good mid-range turbo that boosts a bit later (~3500rpm) and is efficient until a bit before the redline (~6500rpm). Now, keep in mind a lot of this depends on the type of exhaust turbine being used. For this reason, hybrid turbos are often the way to go on the RB engines.

That turbo is honestly a bit large for the RB20 to spool up, so it would be like the second example. It would not be boosting much in the low-mid RPMs, and hit it's efficiency range in the high RPMs.


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## Nismo Skyline (May 2, 2002)

GTES-t said:


> That turbo is honestly a bit large for the RB20 to spool up, so it would be like the second example. It would not be boosting much in the low-mid RPMs, and hit it's efficiency range in the high RPMs.


I agree, WAY too big for a RB20, it would spool at about 7k.

Boost is just a number. It tells you how much restriction there is in the intake system.

My car makes 533 to the wheels on 15.9 psi, which is about 630 crank. You don't need a lot of boost if you do the right things to the rest of the system.

My other car made 577 to the wheels at 27.5 psi, which is about 640 crank (not an RB engine). Which is the more efficient system?


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## DanD (Sep 28, 2004)

I am pretty sure it is RB26 powered. And I am just saying that you can make big power with low boost, but that takes a large turbo to do. If you only plan on running 14.5 psi on lets say a t88, you could get a much better powerband with a smaller turbo with more boost.


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## little240boy (Jan 13, 2004)

what turbo do you recommend for the rb20det? are the turbos from other cars that work well that i could inspect and possibly luck out with at the junkyard? Anyways for a brand new turbo kit, i was lookin for more of a mid range 3k-6k rpm since i think the rb20 redlines at like 7 or something? What are the first engine bolts-ons/recommended parts to tune the engine? The only car i can afford is an rb20 1989 gts-t or gts-4. I'm probably going to have it as my daily driver so are there things that will prolong the engine/turbo life other then the obvious fluid changes? i also read somewhere that on a stock rb20 that 91 octane is not recommended although the FSM says it is recommended? anyone know what this guy is talking about? Thanks

Matt


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## jeong (Jul 22, 2004)

little240boy said:


> what turbo do you recommend for the rb20det? are the turbos from other cars that work well that i could inspect and possibly luck out with at the junkyard? Anyways for a brand new turbo kit, i was lookin for more of a mid range 3k-6k rpm since i think the rb20 redlines at like 7 or something? What are the first engine bolts-ons/recommended parts to tune the engine? The only car i can afford is an rb20 1989 gts-t or gts-4. I'm probably going to have it as my daily driver so are there things that will prolong the engine/turbo life other then the obvious fluid changes? i also read somewhere that on a stock rb20 that 91 octane is not recommended although the FSM says it is recommended? anyone know what this guy is talking about? Thanks
> 
> Matt


you dont necessarily need a brand new turbo kit.. waste of money imo. how much power are you looking for?? the first mods you should do is open up the airway.. intake/exhaust. then you can play w/ the boost a little bit. if you want 250-300hp, you could use turbos from rb25det or vg30det. i dont know about stock fuel pump but stock injectors are good till about 320hp. dont forget to upgrade IC once you exceed 300hp.

higher octane is better but the rb will survive even if it's running on 91


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## Nizmodore (May 9, 2003)

And you just can't shove heaps of boost down the throats of the twin cam RB's.....they have rather high static compression ratios to start with unlike the RB20ET and RB30ET.......(but these motors don't have oil squirters for the pistons....)

Back on topic, Around 7psi for most RB's........ 

I'm not a big fan of the RB20DET.......I prefer something a little larger to work with, the small intake and exhaust ports (compared to the RB25/RB26) and poor flowing inlet manifold, lack of bottem end grunt, haveing to rev the S**t out of them to go anywhere keep me away......I'd personally keep a smallish turbo on them to make the powerband larger......a T3 from a RB30ET is about as big as I'd go....sorry 

Some pics of the RB I'm building.......










Shows what I've blocked up......










One clean head......










My extractors before I attacked them with a angle grinder (the flange pattern is diffrent on a RB twin cam head, as opposed to a RB single cam head) What no turbo manifold? No I prefer blowers/superchargers, I've gone through my turbo RB days....Still I do have a RB25DET manifold, and a old T3.....I wonder how a turbo + supercharged RB30 Twincam would be like? 










Good bye flanges......










Makeing up a plate to weld the flanges onto, useing a RB25 exhaust manifold gaskit as a template...










The flanges sitting on the head, I had to cut them inhalf because the port spaceing was wrong. I'll clean them up with the grinder.....


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## jeong (Jul 22, 2004)

seems like ur having fun


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## B14Boost (Sep 6, 2004)

*Skyline Boost*

Not sure about the GT-R's boost, but I think the RB25 runs about 8 PSI. It can handle 12 safely. The RB20 Runs 5 under low RPM's and 7 under High. It can also handle 12 safely (Max 1 bar or 14.7 PSI). The stock RB20 block can hold about 400-450 Wheel HP. The 25 block can handle about 500 WHP. And the 26 block can handle somewhere around 800 WHP. Thats all. Cheers.


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## tougedrifter (Sep 17, 2004)

B14Boost said:


> Not sure about the GT-R's boost, but I think the RB25 runs about 8 PSI. It can handle 12 safely. The RB20 Runs 5 under low RPM's and 7 under High. It can also handle 12 safely (Max 1 bar or 14.7 PSI). The stock RB20 block can hold about 400-450 Wheel HP. The 25 block can handle about 500 WHP. And the 26 block can handle somewhere around 800 WHP. Thats all. Cheers.



I believe (dont know)GT-R's run about 7 psi on both.


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## PORSCHEKILLA (Jan 12, 2004)

215hp out of the gtst r32 2L straight six is mad (rb20det)... better than the VL's 150kw out of a 3L and even a bigger turbo...this is aimed at Nizmodore's comments


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## Nizmodore (May 9, 2003)

PORSCHEKILLA said:


> 215hp out of the gtst r32 2L straight six is mad (rb20det)... better than the VL's 150kw out of a 3L and even a bigger turbo...this is aimed at Nizmodore's comments


And no torque what so ever......215hp is around 153Kw.....3Kw? I mean come on 3Kw is nothing....the RB20DET is a ****** off boost (compared to a RB30ET), its hopeless in a day to day car.....You have to rev the **** out of them to get anywhere......a very poor powerband....

I've seen people do conversions into them in VL's away from RB30E's and RB30ET's (they think twin cams are better.....) and most of them either went back to a RB30ET or traded in the RB20DET and purchased a RB25DET.....

I know you have to change the VL's final drive ratio (std for a 3L VL is 3.45:1) to around 4.11 to get the engine up in revs quicker....still.....I mean the R32 Skyline that most of these engines come out of has a final drive of 4.36:1 or sumthing.....and you cant get a Borg Warner 78 Serries diff of that ratio  

All things being even, say one VL with a RB20DET and one with a RB30ET, with both cars haveing a 4.11:1 Final drive the RB30ET VL will kill the RB20DET VL with less power...why? Greater torque....on boost much quicker...There are a lot of kids around here who buy VL's, grab a front cut with a RB20DET in it, chuck it in their VL and expect to set the world on fire....*sigh* been there done that....

You'll have to learn someday that peak power is not the be all and end all.....I mean by your way of thinking, you should ditch the RB20DET and goto a non turbo NEO RB25DE, its rated at 156kw.....but has a poorer powerband again....I mean really think about it.....

The RB20DET's upside? They are a very smooth, very reliable motor and if you can live with the very revvy nature of them (remember there really is no replacement for displacement.....boost can only do so much) A perfect motor for a highly geared lightweight car.....say a RB20DET into a S13 silvia (240SX) etc....

Why do you think I'm building a 3L twincam motor with a blower?


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