While we're on turbos

[William]

what turbo will give me 350rwhp at around 18psi?  How much will it cost?  Will I need a manifold?  My friend just bought an 18g with a manifold for $811 off of ebay.  This will give him about the same power at the same psi.  Is there a value out there like this for the red top S13 SR20DET?

[crazycuban]

Why 350 at 18psi?  Is it impossible for you to go higher?  I know that my stock turbo at 16psi will only make 260-270 crank hp;  unless bigger turbos flow more air at lower psi, I don't see how you could make 350 on 18 psi...and thinking about it, the more air you flow, the higher the pressure - which means you really can't make 350 rwhp on 18 psi.  Anyways, a pretty big T3/T04 would do it...for the manifold, go with South Florida Performance.  You won't find a kit or package or anything, but their manifolds are beautiful.

[crazycuban]

Was a repeat, deleted it...don't know how to delete the post...don't think I can...

[William]

I've been studying turbos for the past year, have read Corky Bell's "Maximum Boost", and every article on turbos EVER.  And what you just said didn't make any sense.  350rwhp is about the limit of the SR20DE, according to lots of people.  Why couldn't 350rwhp be attained at 18psi on a particular turbo?  A T-66 at 15 psi will flow a whole lot more cfm than a T3 at the same psi.  Psi is relative to a point, you also have to look at cfm.

[crazycuban]

Yeah, I'm not the know all/end all about turbos, which is why there was kinda a train of thought there...like as in I'm not sure.  But if you're such a turbo expert, go to www.turbonetics.com and look at the compressor maps.  Why take up a post when you can find out for yourself what you want in a few mins.

[crazycuban]

And to answer your questions, because you are the turbo god, you would know that the T-25 can't flow enough air, or even boost up to 18 psi, so yes, you would need a new manifold. The flanges on turbos are different, and the stock manifold has a T-25 flange.

Not tryin to be all pissy and shit, but try and be a little more humble...you're new here, you can be a little more polite when you disagree, or know that I am wrong And no, you have not read every article on turbos EVER.

As far as psi vs. cfm, explain...I thought the two would be related.  If you flow more air, then the air coming into the throttle body would be more pressurized...hence more psi.  Not bein a dick, just curious...

[William]

sorry, I didn't mean to be a bitch about it.  The reason someone might not need a manifold is if they buy an HKS GT turbo.  Some of those have t-25 flanges and can support well over 300whp.  The problem with them is they cost around $3,000.  Plus, I didn' mean to ever claim that stock turbos could last above a certain psi, I never meant to talk about stock turbos at all.  The reason I posted was more about "deal hunting" than anything else.  Just to know what other people have done that has worked.  Thanks for your replys.

[crazycuban]

'sall good...

A guy named Greaser on fa has a GT3037S, which is supposedly good to 400 rwhp.  Taka kaira, j-spec and heavy throttle all have it...a little less than $2000.  Uses a T-25 flange too...my bad, forgot about the GT's...I'm pretty sure you'll have to get a new manifold anyways, though, because a turbo that big has clearance issues in stock location - at least greaser uses a log.  

And yeah...I'm still curious bout how a bigger turbo can flow more air at lower psi <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>...

[AceInHole]

First off... I've seen SR20DE's go above 400whp on stock internals. &nbsp;The SR20DET should definitely be capable of more. &nbsp;At that point, besides a larger turbo, you'll need more fuel. &nbsp;The stock system will be way beyond maxed out.
Greaser might've built his own manifold for clearance, but I think it was for the use of an external wastegate. &nbsp;Yury's car has an HKS turbo, and an HKS manifold or something like that. &nbsp;It's equal length and looks extremely nice, and is still bottom mount I think (the white valve cover was blinding me when I was looking in his engine bay). &nbsp;The stock turbo has the wastegate built in, so the manifold has no flange for an external wastegate. &nbsp;Aftermarket turbos generally don't use external wastegates, which is really the reason you'll want a new manifold.

Also note that larger turbos will spool later, making their max cfm higher in the rev range. &nbsp;Remember that power is a product of RPM times torque, so a turbo that makes a particular boost level at a higher rev range more efficiently will make more power. &nbsp; It's not necessarily just the PSI... you have to remember that it's where that PSI is made that will make the difference.

[William]

think of it this way. &nbsp;A T-66 will flow X amount of cfm at 5 psi. &nbsp;A T-25 will flow less cfm at 5 psi. &nbsp;Here's the kicker. &nbsp;For the sake of argument, let's say a T-25 on your typical SR20 will make 5 psi at 3000rpm. &nbsp;It'll take a T-66 until 4500rpm to put out the same pressure. &nbsp;So a T-66 will flow more than a T-25 at any given psi, but won't get there as soon. &nbsp;So at 300rpm, you'd rather have a smaller turbo, but at 5000rpm, you're thanking god for your T-66. &nbsp;Comprende?

[crazycuban]

Straight...I was wondering whether the HKS manifold fit...

Yeah, I see what you're saying, but I still don't see how you can have higher cfm without higher psi...by my logic, more air=more manifold pressure. &nbsp;Is it because the pressure is lessened because the engine is flowing more air too at that point?

[White240sx]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (William @ Mar. 05 2002,3:51)</td></tr><tr><td id="QUOTE">-what turbo will give me 350rwhp at around 18psi? How much will it cost? Will I need a manifold?

-I've been studying turbos for the past year, have read Corky Bell's "Maximum Boost", and every article on turbos EVER.</td></tr></table><span id='postcolor'>
Just out of curiosity: If you've read every turbo article shouldn't you be able to read compressor maps and decide what turbo will allow you to reach your power goal?

[William]

Here's another way of thinking about it. &nbsp;Think of a penny on the ground with a tube 1 foot long, with equal diameter, going up from it. &nbsp;Then apply 10 psi of boost pressuredown the tube and to the penny. &nbsp;That penny represents a T25's outlet. &nbsp;Now do the same setup for a Kennedy half dollar (or a quarter). &nbsp;That we'll have represent our T66. &nbsp;At the same psi, which tube contains more air (cfm). &nbsp;Now are you with me?

[crazycuban]

hehe sorry, but no...

Alright, my boost gauge measures the pressure in the manifold. &nbsp;No matter how big your compressor gets, the manifold never gets bigger - so if you increase the amount of air in the manifold, you increase the pressure...when you make a bigger turbo, sure, the turbo is bigger, but where it flows all that extra air to isn't bigger, which in my mind would make more pressure...or psi.

[Boostaholic]

Ok, to settle the dispute of psi change on a smaller/larger turbo here is my explanation. 15 psi on a t-25 and 15psi on a t3 are completely different, although they still equate to having the same manifold pressure. For example, on my GSX I can run the stock t-25 all day long and it is only good for about 275 hp at its max. Now if I threw on a t-66 and ran 13 psi I would probably end up blowing my motor. You have to look at both psi and cfm's on a turbo to completely understand how much power you are running through your motor, 450cfms at 15psi on the t-25 and 900+ cfm's on a t-66 at 15psi is a HUGE DIFFERENCE.

Blah blah blah, I have to get back to work and this probably wont make any sense because Im sneaking a sentence here and there so I dont get caught at work, but Ill write more later.

[Boostaholic]

1 other thing that I forgot that is kind of unrelated but is very important. If you ARENT looking at compressor maps and just look at the numbers "400hp @ 18psi", you could be being mislead. The redline on silvia engines arent as high as a supra or a dsm with the rev limiter cut back. Although larger turbos are much more efficient in the upper rpm ranges, and some hit their peak effeciency island around 7500-9000 rpms. If your engine isnt going to be able to rev that high then there is no point in buying that large of a turbo, it will just have more lag and push more hot air than a little bit smaller turbo to fit to your desired rpm range. Just to keep in mind...

[AceInHole]

did anyone even read my post concerning larger turbos making more power with similar boost levels??

[William]

okay, here's a third way. At 5 psi a T66 operates more efficiently than a T25, as a result the intake temps are cooler and more air is in the intake charge. Eh? This gets into how bigger turbos operate more efficiently.

"Smaller turbos tend to be less efficient than their bigger brothers because of the wheel-to-housing clearances. The bigger turbos have slightly larger clearances between the housing and wheels than their smaller brothers. This clearance causes internal leakage, which reduces efficiency of both the compressor and turbine. Since the clearances and leakage are proprtionally larger on the smaller turbos, they are less efficient..."

Read it three times, then it will make more sense. &nbsp;This isn't the ONLY reason bigger turbos are more efficient, just one.

[William]

speaking of me looking at compressor maps, done anyone know the typical volumetric efficiency of an SR20DE?

[crazycuban]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (William @ Mar. 05 2002,6:19)</td></tr><tr><td id="QUOTE">okay, here's a third way. At 5 psi a T66 operates more efficiently than a T25, as a result the intake temps are cooler and more air is in the intake charge. Eh? This gets into how bigger turbos operate more efficiently.

"Smaller turbos tend to be less efficient than their bigger brothers because of the wheel-to-housing clearances. The bigger turbos have slightly larger clearances between the housing and wheels than their smaller brothers. This clearance causes internal leakage, which reduces efficiency of both the compressor and turbine. Since the clearances and leakage are proprtionally larger on the smaller turbos, they are less efficient..."

Read it three times, then it will make more sense. This isn't the ONLY reason bigger turbos are more efficient, just one.</td></tr></table><span id='postcolor'>
I UNDERSTAND NOW!!!

Sorry...that took a lot more effort than it should have. &nbsp;I was thinking mass of air, not density of oxygen...

The volumetric efficiency is kinda tough to find...I doubt anyone would know it. 90% is the right ballpark, though. I was going through compressor maps earlier today...all I've found so far is that its a whole lot of guesswork...

[William]

I have to thank you too for asking the tough questions. &nbsp;I had to go back to my turbo book to find the really good answers. &nbsp;I figured %90, that's the figure I'll play with.

[boosteds14]

<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/mad.gif" border="0" valign="absmiddle" alt=':angry:'> &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/mad.gif" border="0" valign="absmiddle" alt=':angry:'>
let me clear up any disputes( i didnt read all the post so...)

ok, u can get 350whp at 18psi. as long as u get the right AIRFLOW through the engine, meaning that the back pressure on the turbine is at the right pressure to spin the compressor will increasing intake manifold pressure, if u dont have the right pressure ratios, hp ratings for each pound of boost is not consistent. its pretty hard to explain, also,-someone stated that a t25 cant boost up to 25psi-wrong, hate to tell u but any turbo can boost at any level of pressure. it has to do with your exhaust flow and the ability to spin the turbine faste enough to spin the compressor.

in other words, u can take a t25 and boost 100psi, but u will not be able to reach that only if your engine can flow enough exhaust gas to spin the turbine. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=''> &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/tounge.gif" border="0" valign="absmiddle" alt=''>

so to conclude, the bigger turbo thing has to do with the amount of air it can suck in the compressor and spit out while having exhaust gases back pressure good enough to spin the turbo with out having too much pressure because u will not be getting too much HP that way

[luey02]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (William @ Mar. 05 2002,6:19)</td></tr><tr><td id="QUOTE">okay, here's a third way. At 5 psi a T66 operates more efficiently than a T25, as a result the intake temps are cooler and more air is in the intake charge. Eh? This gets into how bigger turbos operate more efficiently.

"Smaller turbos tend to be less efficient than their bigger brothers because of the wheel-to-housing clearances. The bigger turbos have slightly larger clearances between the housing and wheels than their smaller brothers. This clearance causes internal leakage, which reduces efficiency of both the compressor and turbine. Since the clearances and leakage are proprtionally larger on the smaller turbos, they are less efficient..."

Read it three times, then it will make more sense. This isn't the ONLY reason bigger turbos are more efficient, just one.</td></tr></table><span id='postcolor'>
Not doubting your knowledge on turbos about I dont think that's the main reason that bigger turbo produces more power at the same psi as in smaller turbos. &nbsp;

CrazyC, I know where you're coming from and I think the problem in this argument is in WHERE the pressure is measure at. &nbsp;I think when turbos are rated at a certain pressure, it's measuered in the housing itself. &nbsp;Bigger turbo has bigger space = more air at less pressure than smaller turbos. &nbsp;This makes sense to me since rating a turbo using a standard intake manifold would not be accurate since there are different size manifolds. &nbsp; So in conclusion, same psi in bigger and smaller turbos would relates to different PSI at the same (your) manifold; which is more air => more power. &nbsp;

there's no way with same psi of air in the intake manifold, even bigger turbo, would translate into more power.

[William]

I have to disagree slightly. &nbsp;If turbo A is more efficient at a certain cfm and pressure ratio than turrbo B, it will make more power. &nbsp;Why? &nbsp;Because efficiency of a turbo is measured by how well it can move the air without heating it more than the laws of thermodynamics say it should. &nbsp;So, for the same application, if turbo A is %78 efficient at 18psi, and turbo B is only %60 efficient, turbo A will be packing a lot more oxygen per molecule of air. &nbsp;Oxygen is power.

[luey02]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (William @ Mar. 07 2002,12:45)</td></tr><tr><td id="QUOTE">I have to disagree slightly. If turbo A is more efficient at a certain cfm and pressure ratio than turrbo B, it will make more power. Why? Because efficiency of a turbo is measured by how well it can move the air without heating it more than the laws of thermodynamics say it should. So, for the same application, if turbo A is %78 efficient at 18psi, and turbo B is only %60 efficient, turbo A will be packing a lot more oxygen per molecule of air. Oxygen is power.</td></tr></table><span id='postcolor'>
I would've let this go if you didn't disagree.. &nbsp; <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/mad.gif" border="0" valign="absmiddle" alt=':angry:'> Efficiency of a turbo can only refer to energy of outgoin air comparing to energy of incoming air. &nbsp; that's how you measure eff., using energy, not the amount of oxygen molecules. &nbsp;Energy loses thru heat lost, how well the turbines transfer energy to air (gaining pressure); and even through sound. &nbsp;Atmosphere can not change it's % of oxygen just by compressing and decompressing air so you're wrong there too. &nbsp;Also, if what you say is true, which is not, 78% eff. has exactly 1.3 time more oxygen molecules than 60%eff in same amount of air. &nbsp;that does not translate into the huge HP gain from larger turbos, like I said, not a main reason for it. &nbsp;(even if it's true) &nbsp;

stay in school is paying off... &nbsp;lol..