MAMASAIDKOUOUT

I have tried calling every turbo company I can find and they are all unreachable for one reason or another, I need to find out what the best single turbo is to put on my...
383 stroker
pro action heads 72cc 235intake runners 2.08 and 1.60 valves
flat top pistons
victor jr intake
holley 850dp purchased from ati and tested on a 900hp blowthru supercharged camaroc(it handled 15psi ok)
compression is 9.7-1
I dont want to run more then 1bar and i will be running 2 really good intercoolers
I just need to know what turbo to get or how to determine which to get. thanks

Guido

How fast do you want to go?
How much $$ do you want to spend?

Lee7

9.7:1 cr?

thats not good at all for turbo.

MAMASAIDKOUOUT

aorund $1000 to spend but I need the right turbo so whatever it takes maybe just not with all the fancy extras and i want around 800hp, I currently make around 350-375 and I cant run more then 1 bar so maybe I am looking at 700hp? I just need to get the right turbo on there and figure the max hp out later

83 Crossfire TA

iTrader: (2)

Well, first some quick math… a 383 with 72cc chambers and flat top pistons with a reasonable quench distance will usually be around 10.2:1 compression. Did you actually cc stuff and get 9.7? Either way, I really doubt that any iron headed engine with 9.5:1 or higher compression is going to tolerate any real boost without running into detonation problems unless you’re running race gas all the time.

Second, assuming your hp #’s are correct, and assuming that you match the turbo well enough to be at 70% adiabatic efficiency and the intercooler is 75% efficient (both are at the higher end of things, more likely you won’t be quite that efficient) you’d have to run somewhere in the range of 23psig boost (after the intercooler, probably 2 or 3 psi more before) to see 800 hp. I don’t know what fuel you’d need to run to make that work with more then 9:1 compression, probably something along the lines of methanol or straight toluline (117octane).

If you ignore all that and still shoot for that hp on that engine, I’d be looking for something like a T66 or larger… probably a T72 or T76 which would be right in their sweet spots putting out that kind of airflow and boost pressure.

MAMASAIDKOUOUT

yes I cc'ed it to 9.7-1, and it has aluminum pro top line headsand i also said at the most 1 bar, pumped i am only gonna run what i can...maybe 7-10psi?

83 Crossfire TA

iTrader: (2)

Well, that’s a bit more reasonable… I would predict that with aluminum heads and 9.7:1 you’ll probably be safe for about 6-8psig on good pump gas with a good tune… somewhere in the 480-520hp range… That puts you in a different world with the turbocharger sizing, it’s much less pressure for the airflow and will require a larger turbo to move the air. The smallest that looks like it will work for sure would be a T72, but a T70 might work…

The_Raven

1 BAR is what you are running now, 1 BAR equals 14.7 PSIA which is what the air pressure is at sea level, and other factors like humidity (I think the spec is 70%) and a couple other variables. So to run "1 BAR of pressure" is 0 PSI. 2 BAR, is 14.7 PSIG (Pounds per Square Inch Gauge), this is what you would see on the boost side of the boost gauge, and what I think you are refering to as "1 BAR".

MAMASAIDKOUOUT

dude......come on, either help me with my question or not, dont bother with responses like that. 99% of people with a boosted motor know what a "bar" is and that same 99% know what I mean. So for you, the 1%, to post a reply to clear something up for that 1% who dont really understand what I mean is pointless because you are the 1 and only 1%. Get it? I am not being mean but thanks for clearing it up for yourself.

The_Raven

Hey, I was just pointing it out since it seemed like you didn't know...

And as far as selecting the right turbo, it takes more than just asking a question on a BB, there are many variables to selecting a turbo, how the vehicle will be used, type of racing, efficiancy of the engine, daily driver/weekend warrior/infrequent driver, among a lot of variables....

I can't see how someone could sit there with the limited info and say "X" turbo will be right, since even some of the most experianced turbo engine builders out there will tell you, you probably won't find the right turbo the first time, but with enough calculations and research you can at least get it in the ball park.

Besides PSIG is just a measurement of restriction, which is why ported or higher flow intake tracts will through some variables off, and make "the perfect turbo" seem not so perfect, since too many times people look for a certain number on the gauge, instead of proper amount of air flow from the turbo to support the horsepower they wish to make.

MAMASAIDKOUOUT

I need to know how to know what to get. Can one of you guys point me in a good direction, I am buying the book maximum boost for help too

Guido

I feel like I can select a decently sized turbo for most combinations. Get an idea of what the guy is wanting to run and select something in that range.

If I were you, I would look around at what people are running on cars with similar conditions as you. You could put a big turbo on it, and run low boost in which case you wouldlt be leaning on the turbo too badly.

You could put a small turbo and to get the flow out of it, you may have to run high boost to get what you want. In which case you are going to have some trouble keeping all your gaskets dry unless you have a good vacuum system.

15psi. Hmm. Youd probably be able to get by with a 64-70mm compressor wheel. That will make for decent mid range power out of the turbo and with good gas and maybe water/alky injection you can keep from burning holes in your pistons.

You will also want to decide what type of fuel you run. 15psi with that kind of compression, I would run C16 at the race track or anytime you are going to see full boost, simply for precationary measures.

Or as someone else mentioned, you could step up to a larger turbo, and lower boost. Perhaps Im talking out my *** here and someone needs to correct me. LOL

good luck.
it wouldnt hurt to try again to get in touch with a shop that knows what they are doing. That is what I did.

83 Crossfire TA

iTrader: (2)

FWIW, you’re both wrong. 1.01bar = 1atmosphere = 14.7psi. One bar = 14.5psi. If you’re talking atmospheric pressure you should probably be specifying absolute or gauge pressure (ex: psia or psig) to clairify if you’re including atmospheric pressure in your numbers.

The compressor side mostly ignores all this. It’s just dependant on intake air flow which should be proportionate to the hp produced. Assuming that his current hp predictions are accurate, my recommendations are accurate.

The turbine side is greatly effected by the factors that you’re stating, as well as engine tune, turbo manifold/header construction and his exhaust. That is the reason that I didn’t bother recommending a turbine side since I do not have enough info to decide that (for that matter, that’s usually an educated guess anyway)

as I’ve stated in this forum many times before, boost pressure is just a measurement of restriction, nothing more and nothing less. Like in my above explanations, you do not make power because you’ve got a certain amount of boost, but because you’re moving a certain amount of air and you’ll probably see some specific amount of boost due to the restriction that the engine will pose to that amount of air flow. Like I’ve also already said, you can predict the amount of airflow that the engine is capable of based on his hp #’s. If his numbers are off (exaggerated, whatever) then my predictions are off and may not work. If his numbers are accurate so are my predictions (which were made on the conservative side, if anything, if his numbers are accurate, he will likely have slightly better results then I predicted, but there is no use in getting someone’s expectations up)

The_Raven

83crossfire:

I have pondered what you said for a while and all info I have seen/read, etc. says that 1 BAR equals 1 atmoshere, which is 14.7 PSI (at sea level, etc, etc), where did you find this info out ?I'd be interested in seeing more.

Also the compressor side (again) from the info I have read/seen, etc also has a dependany on use, not just a direct relation ship, if you look at superchargers (centrifugal ) you will see a varition on sizing, trims, and drive ratios for similar applications, so this supports that theory.

I do agree turbine side is a little trickier to decide on, but I'm sure there is some calculation somewhere that would get you into a close balpark as well.

The compressor maps, do only account for displacement and PSIG that is desired to read, but even after that, most people will say they are just a close guide, not nessisarily the "end all, be all", I haven't see a way to read them that takes into account actual VE, runner length/size, or other things that may or may not effect the outcome.

Best way I've found to get at least close with a turbo size, is look at what other people/manufacturers are using for a similar/same set-up and use, and base yours off that, with maybe a little bit educated guessing, as to "improve" upon that.

At no point did I say that what you wrote will not work, just that I don't see how that it would be "best" without knowing everything about the car.... *shrug* It may be the best combination ever, who's to know without trying it?

Just my $0.02

The_Raven

Oh and for finding approximate turbo sizing, I used to use this site, but now they just list Garret GT series turbos for all applications, but it does still list some compressor maps.

Might give you some ideas though.

Some calculators

83 Crossfire TA

iTrader: (2)

Not sure that I’ve got a specific location, it’s just a known conversion factor.
1 bar = 14.50377 psi
1 atmosphere = 14.69595 psi
1 atmosphere = 1.01325 bar

I donno, do a web search for conversion factors, someone out there will probably have it right.

they’re not as close a comparison as you expect. The wheels in them are designed with a significantly different profile and most work best in the 30-60Krpm range, where most turbos use a profile that works best in the 80-150Krpm range.

To be honest, I’m not positive that I understand what you’re getting at with this anyway. I understand that there are subtle differences in the shapes of compressor maps which could make one turbo a significantly better match to a specific application then another even though both may move the same amount of air. But that is exactly what I took into account. I took into account his best description of what he has and what he wants and gave him an answer based in the turbos that people can commonly get. Notice that when his responses changed slightly so that he needed to move LESS air at a LOWER pressure, I actually recommended a larger turbo. That was because of the shape of the compressor map and where those needs fell on the compressor maps.

This is not a simple “he wants X hp, which will require Y airflow which Z turbo can provide.” Although that will probably get you a turbo that could be made to work, that will probably not get you a great fit and will probably result in you pushing the turbo to the ragged edge...

If you know of one or find one I’d love to hear about it. The fact is that I’ve never seen anything besides rules of thumb on this, and pros (those who design and hold patents on them) will usually recommend “choose a turbo that has a few exhaust turbines that are easily available in roughly the right size so that you can select the best combination by trial and error.” The big reason for this is that very small changes in the exhaust before and after the turbo can make HUGE changes in the A/R that you’ll need.

FWIW, you’ll also probably need to find some way to compare different “frame” sizes (ex, a .83 T03 will spool well on something as small as a 3.8L, where a .83 T08 will be slow to spool on a 350), and even worse, some way to convert different manufacturer standards, specifically Holset many others just designate their turbine sizes by nozzle area (the A in A/R) and ignore the radius.

compressor maps don’t have much to do with displacement but airflow (volume or mass, depending on who made the compressor map) on the x axis and pressure ratio on the y axis.

The VE and power band are related (the torque curve and VE curve will have EXACTLY the same shape), and you can use one to predict the other. Harmonic tuning due to runner length and exhaust design does become a variable in this equation, especially since in almost all cases you loose the scavenging effect from exhaust, but typically, the best tuned setup only gains or looses about 7% in this area… something that is more then encompassed in the size of an appropriate compressor map.

OEM’s size turbos with significantly different criteria then what “performance freaks” that know what they’re doing size turbos, (ex, the dinky little IHI turbos used by some OEMs are MUCH smaller then anyone would consider in a performance application) and I don’t think it’s even appropriate to consider that in this discussion.

Copying someone else’s setup is only appropriate if the setup is very similar to yours, and it will only be as close a match as their setup is, which is probably only as close as a combination of how good the advice they got was, how closely they followed that advice and how good a selection they had to choose from. The fact is that in the performance world it seems like anything that gives any improvement (and even a grossly mis-sized turbo would give an improvement) is touted as great by those that spent their hard earned $$$ to buy it an put it on their car.

If you insist on taking that approach then I would suggest that you find the people that get unbelievably good times out of parts that you don’t believe can deliver those times, because they usually know something that the rest don’t, and then copy the combination to the letter. (FWIW, every car that I’ve ever owned has been accused of being a factory freak, and then I’ve been accused of misstating mods… the latest thing that I’ve spent a lot of time on, my brother’s car, using one M90 blower is running mid 11’s at 120mph in a big 4 door, and I guarantee that it will see 10’s by the end of the year. I don’t know of anyone that has run faster then high 12’s in a similar weight car with just an M90. Take that however you want)

I don’t think that I ever reacted like you said that it will not work. My point is that I am fairly **** retentive with details and I’m giving the best information that I can return with the details that I’m given about it. To be honest, if it was my car I’d ditch half his combination, sell off some of the parts and probably use some cheaper stuff that will work better and use a completely different turbo, but I haven’t wasted my time with that since most people aren’t too easily convinced to ditch the combination of “right” parts that they’ve accumulated just because someone else says that you should and the turbos that I would recommend would be difficult if not impossible for most people to find.

83 Crossfire TA

iTrader: (2)

Ray Hall’s site is pretty good if you remember that the calculators have a few shortcomings. Probably the biggest is that his attempts at recommending turbine sizing tend to return numbers that are about one step too large for most people’s combinations. As best as I can figure he either selected them for use in a non-wastegated (old school) combination, or he assumed that people know more and will build better exhausts then 99% of people really do.

bad_turbo

You guys are talking WAY over my head with those figures your throwing out, but I wanted to add my 2 cents. A friend of mine has run as high as 24 lbs of boost on his small block with 10.1 compression, but he is running C-16. His motor has made several passes down the track with no problems.

83 Crossfire TA

iTrader: (2)

Like I said earlier in this thread... 10:1 or higher will work with race gas. C16 is the race gas of race gasses

ozzga

thanks for the explanations, Crossfire. I was actually wondering about some of that stuff.

MAMASAIDKOUOUT

got some responses

Turbonetics said...
T-76 with Q-trim

Innovative Turbo said...
T-72 with Q trim and they said it was actually a GT-72 and they also said they manufacture their own turbos. true?

budda

I gotcha bar, it's about 12" long and has more boost than yo mamma's 1969 hair dryer! So gitcha some of that... with some milk of magnisia and a tube of preparation H! Whatcha think about THAT????

MAMASAIDKOUOUT

ahhhh.......I think you are gay.

bad_turbo

T-netics and Innovative both manufacture their own turbos.

B4Ctom1

Too bad thats not really important...