Turbo Sizing Tips and Compressor Map How-To's

[Kreator]

Ok i have several bovs in mind that i can afford, but since i ain't got no bov experience, i dunnow what to go with. It shouldn't be too expensive (like ssqv) but shouldn't be a piece of crap either.

What i'm thinking about right now:
HKS SQV
HKS Super Blow Off
Blitz Super Sound

From somewhere i heard that SQV is a pos. Is that true? Also i've noticed that many bovs on ebay come with 2" pipes. Now if i intend on running 2.5" piping from the turbo to the intake mani and stick this 2" pipe at some point and use reducers to adapt, will that be damaging performance?

[uiuc240]

apparently a popular BOV on the cheap is the one off a 1g Eclipse.  those can be had for less than $50.

the ones you are seeing on eBay are designed to drop in the SR SMIC stock piping.  that's why they are 2" ID.  if you want bigger piping, just buy a BOV without the premade piping, and weld a flange on whatever piping you need.

BTW, i have a blitz BOV...it's nice. &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/inlove.gif" border="0" valign="absmiddle" alt=''> &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'>

Eric

[Kreator]

Which one do you have? The super sound?
Also i figured out they are for stock piping. I was just wondering if running a 2" piece on otherwise 2.5" piping would be bad. Cuz most used ones come with those pipes and they are cheaper than brand new ones without em <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'> So i'm still gonna get that and cut off the flange and weld to a bigger pipe in a worst case.... if that's even possible

[uiuc240]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Kreator @ Nov. 16 2002,10:23)</td></tr><tr><td id="QUOTE">Which one do you have? The super sound?
Also i figured out they are for stock piping. I was just wondering if running a 2" piece on otherwise 2.5" piping would be bad. Cuz most used ones come with those pipes and they are cheaper than brand new ones without em <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'> So i'm still gonna get that and cut off the flange and weld to a bigger pipe in a worst case.... if that's even possible</td></tr></table><span id='postcolor'>
Yeah, I have a used Super Sound...not the new DD. &nbsp;It's working nicely for me, though. &nbsp;Not very loud, though, if that's what you're looking for. &nbsp;It's more of a "woosh" than a "pfffffft".

Do you have a 2.5" oulet on your turbo? &nbsp;If not, why use 2.5" piping right there? &nbsp;Just start out with 2" and increase to 2.5" after the intercooler...plenty of room for the air.

Eric

[Kreator]

Well, my MAFS and the throttle body are both 2.5" so i will have to adapt somewhere anyways. The only thing i was thinking was that isn't 4 psi different on 2.5" compared to 2"? I mean, the air is at the same pressure, but the amount of it is bigger in the 2.5" pipe... I mean i realize there are trade offs of both setups. 2.5" piping - turbo spooling faster - air gets hotter - less power. 2" piping - volume of the air almost 2/3 of the volume with 2.5" piping - lack of air at top rpms - loss at top rpms.... Also, won't different size affect the actual psi? Like psi in 2" piping would be like only a percentage of that in the 2.5" piping... although now i'm thinking it's the same thing...? Bleh. confused... would be great if someone explained it to me...

As for the BOV, it doesn't really matter if it's a woosh or pffft sound. I'm more concerned about whether it will leak or not and if it's gonna respond quick enough. Thanx for the input.

[uiuc240]

What you really need to be looking at is CFM or lbs/min, not simply PSI. &nbsp;For instance, imagine a small turbo that puts out something like 400 cfm at max flow. &nbsp;This is all it will flow. &nbsp;Period. &nbsp;If you put bigger pipes on, the velocity of the air will change, the temp will change, and the pressure drop will change...things like that. &nbsp;But PSI is fairly irrelevant in the equation. &nbsp;This is one of the reasons that after a certain level, turning the boost up on a small turbo does not give any more power. &nbsp;The turbo simply cannot produce usable airflow (CFM) at that pressure level.

It's probably easiest to talk about the type of air compressors you find at Sears. &nbsp;They have a rating that goes something like this:

6.9 CFM @ 40 psi
4.3 CFM @ 90 psi
2.7 CFM @ 120 psi

Those are made up numbers, but you get the point. &nbsp;This is showing you that if you need something that uses high CFM levels (spray gun, for example) then you need to carefully consider the PSI level that tool requires.

A turbo works the same way. &nbsp;

All I'm saying is that it's not going to change your PSI by going from 2.0" to 2.5" piping. &nbsp;The only thing that *might* change (if there was a substantial restriction) is intake temp and pressure drop (both will decrease).

You need to consider the CFM of your turbo at a given PSI (you mentioned 4 psi...which is low). &nbsp;I would imagine you'd only be flowing somewhere in the 300 CFM range with a T3/T4 at that psi. &nbsp;But that's a total guess.

But if you know what the CFM is at your psi level, then you can figure out what pipe size you need. &nbsp;Get it?

Eric

[Kreator]

Ok i kinda get it, but this question has been buggin me since i bought my compressor but never had a chance to ask. Why if i raise the pressure, the CFM drops? From what i was thinking more pressure => air coming through faster => more output per minute. So why does CFM go down as pressure goes up?

Now lemme get this straight:
CFM - cubic feet per minute - volume of air the turbo flows per minute right?
PSI - Pressure per square inch - pressure of the air inside the pipes(between the turbo and throttle body) correct?

Now say i want to flow 300cfm at 4000rpm. If I use 2.5" piping i get about 19.6si area. If i go 2.0" i get 12.5si area. But since i still want 300cfm flow, won't the turbo have to spin faster so it could push the air faster and thus raise psi?

Oh, and i'm considering a T3 turbo with .60/.63 i/e housing a/r ratio (if i luck out) or .42/.48 in the worst case. I'm going to reread The Book tomorrow (when my friend gives it back to me) so i'll compute the cfm and all the other stuff from there...

[uiuc240]

This is becoming our own personal thread. &nbsp;Hehehe.

CFM drops on a compressor when you raise the pressure level because the pump cannot keep up. &nbsp;Think about it like this. &nbsp;A spray gun needs a lot of air at a fairly high pressure to atomize paint...$$$ compressor. &nbsp;A nail gun needs high pressure, but low flow...$ compressor. &nbsp;Make sense? &nbsp;As for how this relates to turbos:

The turbo has an efficiency range. &nbsp;It is mapped for a given lbs/min and a given pressure ratio. &nbsp;I figured out a bunch of that stuff just the other night for my car. &nbsp;Strangely enough, piping diameter never really figures in to the calculation. &nbsp;I think it basically has nothing to do with the flow potential of the compressor.

Here are my conclusions.

1. &nbsp;CFM is CFM and PSI is PSI. &nbsp;The two are *not* directly related. &nbsp;The reason we use PSI is that it is easily measurable with a boost gauge...a CFM meter is basically the same as reading the voltage on your MAFS (like with an S-AFC). &nbsp;

2. &nbsp;Piping diameter will only affect performance if it's TOO small. &nbsp;Keep in mind that as the air flows through the pipes and the intercooler, it will shrink (thermal contraction). &nbsp;So, I think that even if a 2" pipe at the beginning causes a bottleneck, it'll average out by the time the air gets to the throttle body.

3. &nbsp;However, as always, bigger is better. &nbsp;If you have the room and the money to use big intake piping, it can't hurt. &nbsp;I think the reason the stock SR piping is 2" is just because that's the size of the turbo outlet, and that's really more than you need to flow the CFM of a T25 set at 7psi.

Eric

BTW, what psi do you want to run? &nbsp;I could size you a turbo right now.

[Kreator]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (uiuc240 @ Nov. 18 2002,11:28)</td></tr><tr><td id="QUOTE">This is becoming our own personal thread. Hehehe.</td></tr></table><span id='postcolor'>
I don't mind hehe <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>

I'm still a little bit confused though. The CFM is just hte rate right? So if i'm flowing more air per period of time, &nbsp;i'm compressing it more and therefore the pressure which air is under should rise? Or am i completely off here? I don't know if in yer initial statement you meant different compressors... cuz iirc correctly mine had several marks for psi on a single compressor. Like that that exact compressor would flow this amount of air at this psi...

As for the turbo, it gotta be a t3 (i want early spool up). Now the output diameter of that is 2" inches as well. But like is said, my maf and throttle have 2.5". So the earliest bottle neck would come at the mafs anyways. And i'm not intending to run i/c. As for the psi, i intend to run something small so i don't max out the injectors. Jeff240sx is running 4.35psi and that's what i'm aiming for as well. He is running a t3/t4 if that helps.

Now couple more questions i got. First, the bov reads the pressure from near the throttle body. And wastegate reads from the compressor (iirc - read hte book a while ago).. will those 2 give the same reading? And the second question, how does psi vary with turbo size? What makes it different?

[uiuc240]

The rating on the compressor is telling you one specific thing: &nbsp;How much air you can flow at a given pressure. &nbsp;It translates to one other thing: &nbsp;How good your compressor is. &nbsp;This is why more expensive compressors have bigger pumps or bigger tanks. &nbsp;If you need to flow 7 CFM @ 90 psi, but your compressor can only handle 5.9 CFM at 90 psi, it won't work right. &nbsp;It'll cycle constantly, and it won't have enough flow to properly operate the tool. &nbsp;Get it?

I ran the numbers for your motor and PSI goal. &nbsp;First off, your temps are in a good spot. &nbsp;No need for an FMIC with your setup. &nbsp;Your inlet CFM will be 273 (18.81 lbs/min). &nbsp;Your pressure ratio is 1.3 (19/14.7 psi). &nbsp;If you take these two values and plot them on charts for the T3 turbos that Turbonetics sells, you're *way* off the efficiency charts.

<a href="http://www.turboneticsinc.com/comp_maps/fig4.html" target="_blank">
Turbonetics Maps</a>

But, then again, more PSI means more temp, which means more CFM, yada yada. &nbsp;I guess I'm just surprised you're going to go to all that trouble to bolt on a turbo and then only run 4.35 psi. &nbsp;Seems like a small payback for all the effort. &nbsp;Why not just do a few necessary upgrades and run 9 psi or something?

About the BOV and the pressure reading. &nbsp;The two spots for BOOST pressure will be different, yes. &nbsp;However, we usually tap into the line by the throttle body because that is actually what the engine "sees". &nbsp;Also, for the BOV, you need to see VACUUM...the one by the TB gets vacuum, the one off the compressor does not. &nbsp;Now the line for the wastegate, that can come from a spot as close to the compressor as possible.

Get it?

Shit, we should archive this when we're done <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''>

Eric

[Kreator]

Yeah it's a shit load of good info hehe, at least i'm learning alot. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>

Anyways, here are the reasons to run this setup right now:
1. I'm still in college. The idea to have a decent, safe car till graduation (13 months left). After that i might be selling the car, so i don't want to spend a bunch load of money w/o getting any of it back (with this i might sell it for a $1000 over the blue book price of the car)
2. I'm trying to do it for under $1500 and if i manage it, the output i think will be much more powerfull than say i/h/e/cams upgrade that would cost the same.
3. the money aspect. JWT ecu - 600. Injectors - 200. IC - 400. so it's 1200 more and that's almost twice the price i'm considering right now.

Now back to the topic <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''> First question, howd u get those numbers? I know how you got the pressure ratio ( (4.3+14.7)/14.7 ), but how did u calculate the CFM? From what i understood, i'm way below the efficient area, and that means i should go with something smaller right? Like a t28? (Do you know where i can find compressor maps for that, can't seem to find any on my own)... Now that i'm thinking it'd make me some problems... I will need a custom manifold since the rev hard uses t3 adapters... how hard would it be to modify the turbine adapter from t28(or t25) to t3?

Also now suppose i substitute a t3 with a t25. What would be the respective psi level? (I'm guessing it's gotta be different)

[uiuc240]

Go to this website:

Turbo sizing website

Basically, take your CID (146) and multiply that by the rpm (I used 6500), and divide by 3456 and multiply by the volumetric efficiency. Awww shit, just go there and run through the numbers yourself. They have it all spelled out <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''> Nice site. I just found it the other day.

I don't think you should change to a T2 flange. Leave it with the T3. It will work fine, you're just not going to be using it with maximum efficiency. But the good part is that you'll have a T3 flange and if you want to get a BIG turbo later, you're all set. I would like that right now. I'm sticking with a T2 for the time being...upgrading to a T28 BB from an S14 SR in the summer. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''>

Oh, and one more thing. T25 and T28 maps are basically impossible to find. No one will post them. Bastards!

Eric

[Kreator]

Well, you forgot to put the efficiency in the equation <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''> I got 254 and used .85 efficiency and 7000 rpm.

Well, i just got my book back and went into reading. It said that if i'm not running the i/c, my compressor efficiency got to be above 60%. With the t3 "60" i'm gonna be in the 70% area, so i guess i'm fine. From what i calculated at 70% efficiency i'll be providing air of about 165*F to the intake manifold at 4 psi. Is that fine/reasonable?

Now i've gone back to calculate where will i hit full boost. I assumed about 3000rpm and it came out that i will need 107CFM (7.38lbs/min) of flow. Plotting that against the graph - still in the 70% area. So i guess i'm set. I'll be out of the 70% efficiency area only at 14lbs/min => 203CFM => ~5653RPM. And thats about 100-200 rpm after most people shift.

Also, what does the lower bound of the compressor map mean. Suppose, i run like 2psi of boost - 1.13 ratio. That is below the compressor map completely. What will happen? Will the turbo just never spin up to produce any valuable boost?

Also, the numbers on the compressor maps (t3 "60" in this case) - like 56,400 , 78,800 etc - are these the rpms of the turbo? If so, that means that the turbo won't be boosting till it spools to 56400 right?

Another question - the compressor efficiency means (ideal temp rise)/(actual temp rise). Suppose now the pressure ratio of 1.6 on a t3 "60" compressor map. How come the tempreture while flowing 7lbs/min is hotter than when flowing 15CFM when the turbo is supposed to spin faster. How does this work?

Finally, what does the trim stand for? Like what is "60" trim? Is this the a/r ratio? Like .60 => "60" trim or something? If not, is there a way to determine trim from the a/r ratio?

[uiuc240]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Well, you forgot to put the efficiency in the equation &nbsp;I got 254 and used .85 efficiency and 7000 rpm.
</td></tr></table><span id='postcolor'>

I used .85 for the VE and an rpm of 6500...the rpm was the difference. &nbsp;I forgot the KA24DE has a rev limit at 6900...sorry.

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Well, i just got my book back and went into reading. It said that if i'm not running the i/c, my compressor efficiency got to be above 60%. With the t3 "60" i'm gonna be in the 70% area, so i guess i'm fine. From what i calculated at 70% efficiency i'll be providing air of about 165*F to the intake manifold at 4 psi. Is that fine/reasonable?
</td></tr></table><span id='postcolor'>

That doesn't sound too bad. &nbsp;But why not just get a Starion IC or something? &nbsp;If you're having piping made, plumbing that in won't be that hard. &nbsp;Or get an SMIC from someone with an SR (like me <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''> ).

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Now i've gone back to calculate where will i hit full boost. I assumed about 3000rpm and it came out that i will need 107CFM (7.38lbs/min) of flow. Plotting that against the graph - still in the 70% area. So i guess i'm set. I'll be out of the 70% efficiency area only at 14lbs/min => 203CFM => ~5653RPM. And thats about 100-200 rpm after most people shift.
</td></tr></table><span id='postcolor'>

Sounds like you've got a nice match there.

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Also, what does the lower bound of the compressor map mean. Suppose, i run like 2psi of boost - 1.13 ratio. That is below the compressor map completely. What will happen? Will the turbo just never spin up to produce any valuable boost?</td></tr></table><span id='postcolor'>

I'm not sure about that. &nbsp;You're probably right that it would never make boost. &nbsp;Check out this website: turbo site &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/crazy.gif" border="0" valign="absmiddle" alt=':crazy:'> &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/crazy.gif" border="0" valign="absmiddle" alt=':crazy:'>

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Also, the numbers on the compressor maps (t3 "60" in this case) - like 56,400 , 78,800 etc - are these the rpms of the turbo? If so, that means that the turbo won't be boosting till it spools to 56400 right?
</td></tr></table><span id='postcolor'>

Yes, those are impeller rpm numbers. &nbsp;I would assume that until it reaches this point, you will not build boost. &nbsp;But, again, not sure...

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Another question - the compressor efficiency means (ideal temp rise)/(actual temp rise). Suppose now the pressure ratio of 1.6 on a t3 "60" compressor map. How come the tempreture while flowing 7lbs/min is hotter than when flowing 15CFM when the turbo is supposed to spin faster. How does this work?
</td></tr></table><span id='postcolor'>

Well, if you just take a quick look at the map, you'll see that this is outside the prime efficiency range of this turbo. &nbsp;It's create unnecessary backpressure and not working where it wants to work. &nbsp;Sort of like that unhappy sound your engine makes when you lug it in 5th at 1500rpm. &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Finally, what does the trim stand for? Like what is "60" trim? Is this the a/r ratio? Like .60 => "60" trim or something? If not, is there a way to determine trim from the a/r ratio?</td></tr></table><span id='postcolor'>

Trim is the ratio of the inducer to the exducer (small to big radius of the impeller). &nbsp;A/R relates to the area of the housing. &nbsp;Umm...I think. &nbsp;Don't quote me on that.

I'm still learning too.

Eric

[Kreator]

Well, i was looking around for a cheap smic (around my place cuz shipping would kill the whole cheap deal thing) but haven't found one yet. But won't i/c make pressure drop? Like some percentage of psi drop due to the presense of the intercooler? I'm just not sure if that pressure drop would defeat the benefit of the cool down of the air coming in.

Do you know of a way to figure out the trim? Like what should be divided by what? I have a turbo in mind, but the guy doesn't know the trim. So is there a way he can figure it out by mesuring something on the turbo itself?

[Kreator]

well from all that i know, any sr injectors are a direct bolt on. For any injectors that performance companies are making (MSD, Apexi and so on) you will need custom fuel rails. I'm not sure if any other nissan injectors are a direct bolt in.

[uiuc240]

damn. &nbsp;I wanted to keep this going, but I just flatout ran out of things to say <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/sad.gif" border="0" valign="absmiddle" alt=''>

Eric

[Kreator]

Well i thought to make it even more FAQ worthy, I'll just add some more stuff i found out <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>

Ok, the ultimate turbo for a KA running 4-10psi would be t3 with a 60 trim. The .42/.48 ratio is good for lower psi and .60/.63 would really benefit for higher boost settings.

Now about fuel. The stock KA injectors will max out at 4psi at 6000rpm. In order to go above, you can do several things. The easiest (and expensive) is getting the injectors and getting a afc or reprogrammed ecu. Harder but what still might work is getting an afpr and setting the fuel pressure higher (you'll be pumping more gas each duration on stock injectors). The tough part that comes in is that when not under boost you'll be running rich, and at some point will have a very crappy idle. It's probably possible to got 2-3 more psi (6-7psi overall).

Hmm... that's it for now. I'll add if i remember something else.

[Kreator]

Ok, got couple more questions that i need answers to <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''>

First of all, uiuc240, do you curculate your bov back to the intake or dump the air out? I just heard that you have to make it run to back to the intake, so needed to make sure.

Second, what companies make good boost gauges? I don't want to buy an expensive one, but since i'm going to be running very close to the limit of the injectors i'll need one that shows exactly. Also, how bad is the variance in boost gauges anyways? Like approximately? .5psi? 1psi? And while on the topic. I'm going to run an internal WG that is set to 8psi. I was told i could adjust the actuator so it would run 4psi. My question is: how can i set that to the exact pressure? Right now, i'm thinking of doing it with a boost gauge hooked up to the intake and adjust the actuator till the boost gauge shows 4psi. But what if i'm going to be like 2 psi off? That would be deadly... So are there any other ways? I was looking at autometer gauges, but since u say it sux... just wonna know how bad it is <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>

also, is pivot a decent company? I'm looking at their turbo timer on ebay. Looks decent, but the price is pretty cheap. On the other hand, a timer is a timer. Not like the performance of different types would wary alot....

[uiuc240]

My new Blitz BOV is vented to the atmosphere. &nbsp;It's really not as much of a problem as people say it is. &nbsp;The ONLY time I have idle issues is when the BOV loses some adjustment and gets too loose (I need a locknut for the set screw....). &nbsp;But it's up to you...recirc is better for the MAFS.

As for boost gauges...I would NOT get an Autometer if you need extreme precision. &nbsp;Get something like a Greddy or Blitz or Defi or something. &nbsp;My Autometer loses adjustment all the time. &nbsp;I basically just use it as a "guesstimate" and it'll tell me if something's WAY wrong. &nbsp;But to use it to tell me if I'm at 6.5 or 7 psi? &nbsp;Useless.

I'm not sure how that wastegate setup is going to work. &nbsp;Are you using an adjustable HKS one or something?

Pivot seems to make decent stuff. &nbsp;However, I'd say skip the turbo timer and spend money on a NICE boost gauge or something else. &nbsp;Turbo timers are really pretty much useless. &nbsp;If you just got done running the piss out of your car, just drive around the block before you park it. &nbsp;Or just sit there and let it idle before you shut it down. &nbsp;It just seems like a waste of $100 (when you're on a budget). &nbsp;I think it's something you can get later.

Eric

[Kreator]

Well the pivot turbo timer i'm looking at right now is going for around $20 used. And i just want to get it cuz it's gonna be annoying to sit in the car sometimes when u have to go somewhere.

The wastegate i'm using is a standard turbonetics internal wg. set at 8psi currently.

Ok, so i'm gonna look at greddy/blitz gauges. The only question though is how accurate are they? Like what might he deviation be? .1psi? .05psi?

and also, blitz and greddy gauges come with kg/cm^2 readings. is the conversion something like 1psi = .065kg/cm^2? And what about hks gauges?

edit: nm the psi to kg/cm^2 question. It's 1/14.7 DOH!

[Foxcolt]

Internal wastegates or external for that matter cannot be set to run a lower psi than the spring installed.

I would reccomend going with the lowest psi spring available and getting a cheap manual boost controller to adjust to your desired setting.

damn Eric I never new you were so turbo savvy <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/laugh.gif" border="0" valign="absmiddle" alt=':laugh:'> Kudos!

I'll declare you king of all turbo theory if you can make me a compressor map for my 2540 <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/laugh.gif" border="0" valign="absmiddle" alt=':laugh:'>

Jed

[uiuc240]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Kreator @ Nov. 22 2002,12:06)</td></tr><tr><td id="QUOTE">Well the pivot turbo timer i'm looking at right now is going for around $20 used. And i just want to get it cuz it's gonna be annoying to sit in the car sometimes when u have to go somewhere.

The wastegate i'm using is a standard turbonetics internal wg. set at 8psi currently.

Ok, so i'm gonna look at greddy/blitz gauges. The only question though is how accurate are they? Like what might he deviation be? .1psi? .05psi?

and also, blitz and greddy gauges come with kg/cm^2 readings. is the conversion something like 1psi = .065kg/cm^2? And what about hks gauges?

edit: nm the psi to kg/cm^2 question. It's 1/14.7 DOH!</td></tr></table><span id='postcolor'>
I'm not sure how accurate they are...I don't have one &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'>

I bet they are way more precise than my Autometer, though. &nbsp;I'd just pick the one that you like the looks of, and buy that...I'm sure they are all as good as they cost. &nbsp;Heheh.

Something to look in to: &nbsp;is the HKS aftermarket wastegate actuator actually adjustable? &nbsp;Or is the threaded rod just something that allows them to use the same actuator for many turbos....Hmmmmm. &nbsp;Not sure. &nbsp;Otherwise, you're gonna need to find a new spring for that actuator you have.

Jed: &nbsp;I wouldn't consider myself king of anything...except maybe Google. &nbsp;hehe. &nbsp;I just looked up that chit and ran some numbers. &nbsp;Kreator knows some good ish too!

You'll probably have as much luck as anyone getting HKS to release compressor maps for that GT2540. &nbsp;When are you putting that in your car?

I'm in the middle of popping in new turbo gaskets...what a bitch of a job.

Eric

[platinum240sx]

il hook you all up with BOV sound files
the loudest and by my criteria best BOV is the Turbo XS type-H RFL , im saving up for one of those right when i get my red top in the spring!
http://www.alltrac.net/tuning/blowoffvalve.html
if the site says something bout compacity limtis then just go back in 1 hour. peace
platinum240sx

[Kreator]

Uhh, lemme bring this up back from the dead &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/crazy.gif" border="0" valign="absmiddle" alt=':crazy:'>

I guess this question will go all the way back to the CFM vs PSI part. How come the formula for calculating CFM (CFM = V*RPM*VE/3456) doesnt include boost? Does that mean that at 25psi i will need only as much flow as on a n/a engine? Or is it just cuz CFM is this imaginative figure which is used to calculate the compressor mappings, and if you raise boost u stay at the same CFM and just move up along the y axxis(pressure ratio)?

Basicly trying to figure what'll happen if i decide to run 8psi

[uiuc240]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Kreator @ Nov. 26 2002,09:57)</td></tr><tr><td id="QUOTE">Uhh, lemme bring this up back from the dead <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/crazy.gif" border="0" valign="absmiddle" alt=':crazy:'>

I guess this question will go all the way back to the CFM vs PSI part. How come the formula for calculating CFM (CFM = V*RPM*VE/3456) doesnt include boost? Does that mean that at 25psi i will need only as much flow as on a n/a engine? Or is it just cuz CFM is this imaginative figure which is used to calculate the compressor mappings, and if you raise boost u stay at the same CFM and just move up along the y axxis(pressure ratio)?

Basicly trying to figure what'll happen if i decide to run 8psi</td></tr></table><span id='postcolor'>
All you're figuring out in that first calculation is how much airflow comes OUT of your motor. &nbsp;Then, the turbo, in all its super-efficient glory, turns that in to MORE airflow by spinning the compressor. &nbsp;So yes, in your baseline calc, it's the same if you were N/A.

Once again, PSI really is only part of the issue. &nbsp;You can use it to reference with a gauge, and you can use it for a RRFPR. &nbsp;But that's just about it. &nbsp;The biggest thing for making power is the total CFM that the turbo is producing at the PSI that you select to open the wastegate. &nbsp;If you choose 6 psi, and that's 300 cfm (at 7000 rpm on the engine) on turbo A and 250 cfm on turbo B, turbo A will make more power. &nbsp;Easy, right? &nbsp;

So ya see, PSI is related, but you can't convert between the two.

We took this sooooo far from BOVs...awesome.

Eric

[Kreator]

OK, but if at 7000rpm my engine requires 200CFM n/a, how much would it require at 8 psi? is it CFM*(pressure ratio) or something?

[uiuc240]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Kreator @ Nov. 26 2002,4:08)</td></tr><tr><td id="QUOTE">OK, but if at 7000rpm my engine requires 200CFM n/a, how much would it require at 8 psi? is it CFM*(pressure ratio) or something?</td></tr></table><span id='postcolor'>
Check out this website:

whoa<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/lookaround.gif" border="0" valign="absmiddle" alt=':look:'>

And especially read the part about the Ideal Gas Law...I'm still trying to get it all to sink in and make sense. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'> &nbsp; It's very complex. &nbsp;This site is much more detailed than the other one.

Eric

[Kreator]

Ok i'll be reading that a bit later on (comp sci project gettin the fuckin best of me). On the other hand, a bit off topic: I'm trying to decide on an oil pressure gauge. The stock says im to get 60-70 at 3000rpm on n/a ka. Can i figure out the highest it'll go? tryin to decide should i go with 0-100 or 0-150psi?

edit: <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'> post 999 <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'>

edit2: the aftermarket bovs have the screw to adjust the pressure they open up at right? I was looking at 1g dsm bov, but couldnt' find one.... how do i go about it, and any clue what it's set at initially? (saving up my 1000th post for somethin rlly good <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>)

[luke91]

You could find a used eclipse bypass valve at a junkyard for around $10-20. &nbsp;

--luke