About turbos

[Toughguy]

I came across this thread http://forums.gtrcanada.com/viewtopic.php?t=508 and I realise that I don`t know much about turbos. I mean, I know how they work but as far as how to properly size one for a specific power curve I am at a complete loss. I don`t even know what A/R is! Do you guys know any good reference sites that go into the technical details of turbocharger opperation? I want to learn all about the theoretics of turbocharging as well as the real world data from actual experiences. Please don`t send me here:

http://auto.howstuffworks.com/turbo1.htm

Although it did link me to these sites,

http://www.turbointernational.com/

http://www.turbofast.com.au/twin351.html

http://members.aol.com/TurboHonda/info.html

http://unitedturbo.com/basics.html

http://www.honeywell.com/sites/ts/tt/

http://www.turbochargers.com/

and these last were quite helpful but they are still somewhat lacking in technical info.

My conservative goal would be to have an RB26DET put out 400hp to the wheels on a stock bottom end. From what I have learned sofar, that is not too lofty but I would like as wide a powerband as possible at the same time.

Specificaly, I want to find out if the stock turbos need to be upgraded or if a single turbo would be better? I need to know how different cam profiles affect power output? How big of an intercooler I will need and if this is at all possible on 92-93 octane fuel? What will need to be done about the engine management? (new ECU, reprogramming or complete aftermarket setup) What`s better, a mechanical boost control or an electronic one? What other gizmos are recommended for controling and monitoring engine vitals on a turbo motor?

I need to become knowledgeable about all these things before I dive in head first with the purchase of a GTR so if you guys have answers or websites with answers post them up.

Thanks in advance.

Toughguy

[Unlucky Menace]

Thanks. Moving to FAQ

[Super_Dude]

I'll try to answer as many questions as I can with what I know. I might be wrong about a few things so feel free to correct me.

I'm assuming you know what A/R is now because you said "I didn't even know" and that sounds like you got I figured out.
If you want as wide a powerband as possible than probly HKS GT-ss would get you there and spool very quick.
cams mostly affect where the power is at. you could have alotta power outa cams but you loose low end power. I've heard the stock intercooler is good for 400 hp but a bigger one would help. I've heard that our octane here is better than japans and that 94=100 in japan or about that so you should be fine on 93. The stock computer maxes out at 1.2 or 1.3 Bar so I think you will need a standalone or atleast a piggyback. also you will need new MAFs because the stock ones max out (Z32 are a good replacment.) Now boost controllers, neither does its job better than the other. Mechanical you have to pop the hood and fiddle with it to adjust boost. Electronic can be controled inside the car. Also electronic is more expensive.th You might also a turbo timer-these keep the oil flowing through the turbo once you turn the car off. If you just let it sit it could cook the oil around the shaft and **** ur turbo.

I hope I helped

[Toughguy]

I'm assuming you know what A/R is now because you said "I didn't even know" and that sounds like you got I figured out.

Thanks Super Dude. I finaly got the gist of what the A/R is from reading this article. From Hot Rod magazine online of all places! http://www.hotrod.com/techarticles/e...bo/index1.html

Ok so now I know what that is and why it`s important. I`m going back in to soak up more turbotalk!

Toughguy

edit: Out of curiosity, does anybody have the specs for the turbos on an R32 GTR? Who makes them? Nissan? What`s their A/R? What`s the max theoretical HP they can support?

[Toughguy]

Re: About turbos

My conservative goal would be to have an RB26DET put out 400hp to the wheels on a stock bottom end. From what I have learned sofar, that is not too lofty but I would like as wide a powerband as possible at the same time.

Interestingly enough, I came across this article that gives insight on what it will take to accomplish my goal.

http://www.autospeed.com/cms/A_1930/article.html

Toughguy

[satan_gtr]

Maximum Boost by Corky Bell

all you need to know

[Toughguy]

Ok, I`ve been busy, to say the least.

After spending some time getting aquainted with turbo systems in general, one finaly realises that there are many components that can be changed or altered in order to produce more power. What`s not so easy for the average enthusiast is quantifying the effect that each component has on the overall power output. Therefore, I am going to use a systematic approach to figure out how I can reasonably achieve my goal of a 400whp RB26DET(T) with a powerband that will average 75-80% of peak power over a 3000-3500 RPM spread. In other words, if peak is 400whp at 6000 RPM, I want the motor to produce no less than 300whp starting at 3500RPM all the way to 7000-7500RPM. If this is completely unreasonable for a stock block RB26 on pump gas, feel free to tell me. If you can back up your opinion, you will undoubtably save me much time trying to figure out turbo maps, intercooler flow rates and such.

Because at the time of this writing I am still very much a noob in respect to turbocharging, I will take the noob approach and first look at the stock components that make the RB26 the air pump that it is and see which, if any, will prevent such a motor of meeting my expectations.

First, to make horsepower, you need fuel so let`s take a look at the fuel delivery system. We`ll start with the injectors.

Meggala`s site ( http://www.meggala.com/injectorscss.htm ) lists the GTR`s injectors as top feed low impedance Nippon Denso units rated for 440cc/min at 100% IDC (Injector Duty Cycle). Also on this page are some interesting conversions, one of which is converting the flow rating into a potential HP figure for any given injector. The conversion is HP = cc per minute / 5 or 1hp for ever 5cc/min of flow. 440cc thus converts into 88hp. Multiplied by 6 (number of injectors in an RB26) we get a potential output of 528bhp. From these numbers, the capacity to make 400whp sounds promising but let us not forget that we are not only talking about theoretical HP, but also BHP and not WHP. Exactly how much power does an R32 GTR lose through its AWD system? Well remember the bone stock R33 GTR that Brett Clacher dynoed in this article http://www.autospeed.com/cms/A_1930/article.html in a prior post from this thread? From 276bhp to 215 at the wheels suggest a 61hp or 22% loss through the drivetrain. Initialy this sounds quite high for a manual gearbox but let`s not forget we are dealing with an AWD system that uses viscous couplings so the loss is not comletely unbelievable.

So if I want 400 peak whp, I will need how much at the crank? A common mistake is to add 22% to the desired whp but that is incorrect. Instead we need to remove 22% from the actual bhp. The wrong calculation is 400whp*1.22=488bhp (it`s like multiplying the price of a purchase item by 1.15 to reflect the sales tax of 15% in Ontario) This incorrectly factors 22% of 400whp and not 22% of the real bhp value. We thus need to divide the desired whp value by the difference between 100% and the drivetrain loss. In our example, the proper equation is 400whp/(100-22)%=400whp/78%=400whp/.78=513bhp. Well if you`re feeling lucky...... it appears the stock 440cc injectors can support the sought after power level but after dropping $25k on a car, there is no way I would push my luck. Furthermore, this value is at 100% IDC. One Autospeed article I read ( http://www.autospeed.com/cms/article.html?&A=0102 ) suggests, "The flow rates shown in the table are those achieved at 100 per cent duty cycle, that is, with the injectors held fully open. In a well-sized system the injector duty cycle should not rise this high - a duty cycle maximum of about 90 per cent or so is about right." Therefore, at 90%, the GTR`s injectors should be good for 528*0.9=475.2hp. Looks like we don`t need much more right? Maybe something in the 500-550cc range would probably do it. But can it really be that easy? Uhhh......no.

To see if my calculations were correct, I did a search for fuel injector sizing calculators. To my surprise, my calculations DID make sense.......for a normaly aspirated engine. You see, the BSFC (Brake Specific Fuel Consumption see http://witchhunter.com/injectorcalc1.htm for an explanation) was never taken into account and as it turns out, the BSFC is a pretty important factor when determining injector size. Another thing that could potentialy skew my results was the fuel pressure. Injectors are tested at 43 PSI so I needed to verify the actual opperating pressure for an R32 GTR. From page EN-166 of the gtr_32_service_manual.pdf that I got from http://forums.gtrcanada.com/viewtopi...vicemanual+pdf I could see that the GTR does indeed opperate at 43psi. You can see that at idle, the pressure should read 36psi and that pulling the vacum signal hose bumps that up to 43psi. What`s a vacum hose doing on a turbo motor? Consider that at idle, the engine still pulls an intake manifold vacum since the turbos are not spooling yet and the engine really doesn`t require the extra fuel at this speed. As engine RPM goes up, manifold pressure goes from negative (vacum) to positive (boost) and the vacum signal to the fuel regulator disapears and allows the system to overcome boost pressure and reach 43psi net.(net injector pressure as opposed to fuel line pressure which I will explain a little later) Using calculators from http://www.stealth316.com/2-air-fuel-flow.htm , http://witchhunter.com/injectorcalc1.htm , http://www.iroczone.com/calcs/injectorsize.htm and http://www.rceng.com/technical.htm#WORKSHEET (this is just a sample as there are many more to choose from on the net) I get a range of answers from 620 to 700cc/min. These values were obtained using a 43psi fuel pressure, 0.625 BSFC and a maximum duty cycle of 90%. Given that the price difference between a 600 and 700 cc/min. injector is negligible, I would opt for the bigger one. Also, the bigger injector will be able to compensate if your fuel pump cannot provide the neccessary fuel line pressure to maintain a 43psi net. If that last bit is a little confusing, keep in mind that the pressures in my examples are net fuel pressure and not the actual fuel line pressure. If an injector`s flow rating is 440cc @ 43psi and the engine is opperating at 10psi of boost then the fuel line pressure needs to be 43+10= 53psi to compensate for the boost level if the injector is to flow at it`s rated output.

It also holds true that another thing you could do to if your injectors are just borderline is increase fuel pressure by replacing the fuel pump and regulator. Seeing how aftermarket injectors range in price between $120-$300 each, this option might end up being much cheaper. Nevertheless, for stock 440cc injectors to fuel a 513bhp RB26 without exceeding a 90% duty cycle, you would need to be running somewhere in the neighborhood of 80psi of fuel pressure. If that doesn`t sound like alot, remember that the fuel line pressure would need to be 95psi at 1BAR of boost!!! (1BAR= 15psi) This leads me to believe that although Nissan engineered alot of strength into their motors, the bean counters certainly didn`t allow said motors to leave the factory with anything more than the bare minimum hardware required to reliably sustain the intended power level mandated by law in Japan. But you really can`t fault them as all manufacturers do this as a cost saving measure.

As far as injectors are concerned, it looks like I will need to find myself some 650-700cc units. Realisticaly, 600cc units would do the job but would not give me a safety cushion or leave any room for further improvement should I decide to increase horsepower yet again and we all know that once you get it rolling, there`s no stoping the snowball!

Ok so that`s all good but now can the rest of the system (fuel pump, fuel pressure regulator and fuel lines) keep up? One would think that it should be as easy as adding up the total flow for the six injectors and comparing that with the flow rating of the pump but a search for the flow rating of a stock R32 fuel pump netted somewhat varying results. This site http://www.stealth316.com/2-fuelpumpguide.htm#j7 suggests that Skyline pumps are legendary for flowing up to 310 lph yet there is no hard data to confirm this. Other sources have placed the flow of a stock R32 pump at about 190 lph but does not say at what psi. Nevertheless, Turbo & High-Tech Performance magazine has tested an R33 GTR pump and it flowed 252 lph at 43.5 psi and 13.5 volts. What is amazing for this OEM pump, and possibly why it is so highly regarded, is that it can still flow 180 lph at 85psi! Basicaly what that means is that (and this is completely unlikely) it could flow enough for an engine making 490hp @ 40psi of boost! What is likely though, is that it could flow enough to feed a 600hp motor @ 30psi of boost. What is still yet undetermined is whether or not that pump was used in the R32 GTR as well. Another site I used for their online calculators (especialy for the Fuel Pump Capacity Versus Horsepower one) is http://www.slowgt.com/Calc1.htm

I couldn`t find anything on the fuel line diameter or flow rating for the fuel filter but I did come across this site http://www.gnttype.org/techarea/fuel...nearticle.html . Basicaly, it says that if you have minimum 5/16 inch fuel line you should be fine but make sure the return line is the same size or bigger to minimise the pressure drop. As for the regulator, just get a Type C adjustable. Not sure what that is yet but they used one here http://www.sportcompactcarweb.com/fe...cc_r34skyline/ so it must be good. Interestingly, Motorex claims 400whp for that car despite that it only has 550cc injectors. However, the fuel pump has been replaced so they might be running higher than stock fuel pressure. Not to mention that it has upgraded turbos, hotter cams, aftermarket intercooler and a whole whack of other cool stuff! What`s a Super Suction kit anyways?

Well that`s my take on the fuel delivery system. If I am totaly talking out my ass just correct me.

Next I will be looking at the turbos but I will need to do alot more research so it might take me a while.

Toughguy

[Murphy]

Well you are nothing if not thorough

Here - save you some searching - best turbo book going.

[Turismo]

Thread revival!

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