Ball joint

iTrader: (6)

The subject preety much explains it. My engine is starting to go and I have set aside quite a sum of money so I thought what the hell might as well make a street monster. So I want to know what iam going to need to get to run 15lbs on this turbo. I know its a huge turbo but iam crazy like that . Any info would be great.

btw I have a 94 touring mostly stock.

Icemastr

iTrader: (2)

20K ought to do it, heres your shopping list: rebuilt motor, maybe get a street port and some 2 or 3mm seals, and in order, downpipe, catback, Power FC, boost controller, midpipe, Greddy 3 row FMIC, ACT Clutch, pressure plate, Kaaz LSD, shocks and springs, fat tires, heat range 10 spark plugs, ignition amplifier, 1600CC secondary injectors, fuel pump, fuel pressure regulator, maybe 850CC primary injectors, pulley kit to remove air pump, remove emissions stuff, install HKS T51 Turbo Kit, dyno tune it.

allrotor93

iTrader: (126)

no need to go with a turbo that big for only 15 lbs. waste of money. you need to be in the 20+ range for that turbo.

teamstealth

not necessarily...that turbo will flow much more air @ 15psi than say a T04s @ 20psi.

Poweraxel

ill agree on this..i had the T51R KAI before and its truely a race turbo... 20+psi is needed to really get in the sweet spot of this turbo... if you looking for 15-20 psi then your better off with something smaller in the 61-66mm compressor series

good luck

Marshall

...virtually impossible. Pressure is pressure. The T-51 may give slightly cooler air at 15psi and have a bigger hotside -thus increasing hp, but the compressor won't "flow" any more at a give pressure.

enzo250

Such a misconception... SO and SO turbo will flow more at the same psi... YEAH OK...

Pressure is pressure. 15psi is 15psi. I don't care if it's a T51 or the stock turbo. 15psi is still 15psi.

It's when the turbo is more efficient that makes the difference.
15psi at 80 degrees is not the same as 15 psi at 180 degrees

mjw

iTrader: (1)

Uhhh, actually it is not a misconception. Have you studied compressor maps at all? Efficiency does have a lot to do with it, but so does the wheel trim/size and housing. 15psi on a KAI and 15psi on stock turbos is not even CLOSE to the same thing.

Marcel Burkett

At work we have a HUGE pump run by a 15000hp 4160 volt motor that moves 8,000 000 gallons per hour at 10 psi , we also have a tiny one that moves 3000 gals/hr at 150 psi using a 480 volt motor ................... go figure .

RICE RACING

I have to agree totaly, what is a common misconception is the influence of Volumetric Efficiency, this combined with Mechanical Efficiency, and Thermodynaic Efficiency of various sizes of turbos makes an astronomical difference in power in some cases to esentially very similar "block" spec engines. All running the same pressure ratios.

Big Turbos offer improvements in many areas all which equal more power at the same boost levels.

Some thing thats not on a compressor map is the effect on Ve% ("flow restiction" caused by the compressor/housing/turbine wheel/housing) and this has the greatest effect on an engine in terms or giving extra power while not increasing the pressure ratio. This flow restriction or lack there of comes at the expense of low rev response or "lag" so its a balance, but thats a different topic.

Definatley 15psi is not 15psi at all in my books

RICE RACING

When you do your basic cacls on how much flow goes through the engine (to select the right size turbo or "compressor map") many many people forget that the turbo hooked up to the engine (+ other ancilaries such as IC intake manifold etc etc) ALL change the CFM the engine makes at a certain calculated range, regardless of pressure ratio.

The turbo is NO DIFFERENT it chokes the engine via the turbine/exhaust housing, it restricts the breathing potential in the same way via the compressor wheel and compressor housing.

Which equals big differences in Ve% and therefore flow or CFM through the engine at any given pressure ratio. When the big turbo does finally come onto boost it is a much more efficient device which flows a hell of a lot more for the same give pressure ratio compared to the smaller unit. SIZE does matter Later technology (design of housings and wheels) makes a bit of difference but not huge amounts (less than 10% in the best cases) and alot can be determined by physical size.

Pressurized

Ball joint - i am in Columbus and just got done upgrading to a T51, if you're in this area sometime, let me know, i'll be more than happy to show it to you.

i wouldn't reccomend this turbo for a street car, let alone only using 15psi. we haven't even really gotten the car into boost yet, and there is considerable lag, plus it is a very LOUD turbo, for a street car i'd reccomend the 35/40 or T04.

RICE RACING

Have to agree, my step up to a T51 ("larger" than HKS version) is because I want to run 20psi minimum !

If you find the HSK alternative laggy you can get full Garrett versions (from any turbo shop that distributes Garrett) with divied exhaust housings that will improve this side of things.

1.05 divied will be alot better tahn the 1.00 single entry HKS supply, though you will need a good tuned "split" header to take advantage of this.

Cheers!

how can you say 15 psig is 15 psig regardless? Pick up any fluid dynamics text book anywhere and the first thing u learn is bernoulli's principle / equation.

Assuming we are dealing with incompressible fluid (for simplicity)



So what i'm trying to say is that the most important part is flow rate.

one of hte variables of flow rate are pressure, as well as x-section

so u are saying that if i put a differential pressure of 15 psi through a straw, the amount of fluid flowing through the straw would equal a pipe that has a cross sectional area of say 100 meters squared with 15 psi pressure differential??

RICE RACING

Yup it all depends on the size of your straw

Marshall

No, but you have to be careful here, the biggest part of the "straw" is the engine itself, which remains relatively unchanged. If you took a T51, dynoed it at 15 psi, then took a T04S, swapped in on the same engine, and dynoed it at 15 psi, you'd probably see pretty similar peak numbers. You're dealing with a closed loop, wastegate controlled system, not some arbitrarily open straw.

enzo250

No cheers i wasn't saying that... it's clear that 15psi thru a straw and 15psi thru a large pipe will not be the same.

What i meant to say is if everythings the same(same ports, intake manfolds,same throttle body, same piping, etc,etc, etc) and your measuring boost by pressure in the intake manifold.

15psi of boost is 15 psi of boost.

SO where does the difference in power come from?

RICE RACING

Your wrong my friend

Imagin a 10" pipe, on either end it is governed by a straw ........ It does not matter how big the pipe in the middle, if its "governed by a restrictive straw on its inlet or exhaust you change the Ve% of the system, simple as that.

I am not sure what dyno graphs you have seen, but the ones I have seen on many different engine types confirm what I am saying.

An engine system is the same in that a restrictive turbine can cause adverse pressure effects on the engine which will limit its flow, this can be relieved by wasting more gas via a larger WG but this amplifies the pressure differential across the intake to exhaust manifold and this on every engine costs power on some it is more noticable than others. It costs more compared to a bigger sized turbo thats for sure.

Again the size of your straw is important my son

RICE RACING

If every element of the engine package was the same and all you did was swap the turbo (small TO4 to full house T51), this element will effect the Ve% of that engine package independant of the pressure ratio. And hence the flow will go up for a given pressure ratio, therefore power will go up too

sub note: the only exception to this is if that something else in the system prevents the increase in Ve% offered by the larger turbo (IE. stock Intercooler for example, or stock std exhaust system)

machinehead

For all you big turbo people out there, isn't compressor surge an issue? If we go back to the idea of the turbo being a pump, isn't there such a thing as having too big a pump? I mean what if you hooked up a huge pump to a little straw? Not very efficient. The pump is trying to push all that air through a little straw and at the realatively slow speed it needs to turn to pump that small amount of air the air will push back against the comperssor... the compressor has no momentum at those slow speeds, hence, comperssor surge. So bigger isn't always better. If that was the case then why do we study compressor maps and surge lines? Now if we want to run 3 bar then we have to choose a compressor that will flow and be efficient at that pressure ratio possibly at the cost of compressor surge at low boost but we have no choice. However if 3 bar is not a goal then a smaller turbo is a better choice... IMHO.

"At work we have a HUGE pump run by a 15000hp 4160 volt motor that moves 8,000 000 gallons per hour at 10 psi , we also have a tiny one that moves 3000 gals/hr at 150 psi using a 480 volt motor ................... go figure ."

I am curious if these two pumps are hooked to the same size pipe?

RICE RACING

Too true.

A T51 will not surge on a 13B street port engine

And yes bigger is better (for flow), and yes you can go too big.

Marshall

true, but if the straws are 11".......

Tell me what you think of this (not from me):

Just to jump in on this thread and throw out some theory:

When we say "15 psi" we are talking about the pressure in the system just after the turbo compressor. If we eliminate pressure drops across the I/C, T/B, and other such things then we can say that the combustion chamber sees 15psi. Therefore, the mass of air in the chamber is proportional to only two variables:

1) The pressure
2) The temperature

(PV = mRT, where V is the swept volume, m is mass and R is a corrected constant for atmospheric solution, or "air")

Pressure is simply a measure of force over area, but it can also be thought of as potential flow (analogous to voltage). The amount of flow between two points is proportional to the pressure. Of course, the engine and exhaust do not present a constant back pressure on the intake system, but that's a completely different subject.

Anyway, what the CFM numbers on a turbo tells you is how much air the turbocharger can pump at a certain pressure rating. Thinking of it another way, imagine if you disconnected your turbo compressor from the rest of the intake. How much pressure could the turbo create? Answer: zero, because the volume is essentially infinite. The turbo would need to flow an infinite volume of air in order to pressurize the volume it is seeing. And that's way outside of it's range.

The nice thing about CFM is that it's already corrected for pressure. To determine whether or not your turbo will work for your engine at a given pressure rating, simply determine the volume swept each minute at the RPM you care about:

7000 RPM * 2.6L * VE = 546 cu-ft (using 85% volumetric efficiency--this may be wrong for rotaries but its the rule of thumb for piston engines)

If your turbo flows at or near 550 cu-ft at 17psi, everything is good. Please note that as you peruse compressor maps on the web, many are expressed in pressure ratios (2:1 would mean 14.7psi) and pounds of air per hour. The latter requires a nasty conversion because CFM has the pressure built in while lb-hr does not.

Anyway, If the required CFM is too large for the compressor, then the turbocharger will have to work *harder* to generate the same pressure. This means less efficiency and more heat. However, if the required CFM is smaller, then the turbo will see too much back pressure which will also raise temperatures and may also cause spiking. For every motor, target RPM, and pressure there is a perfect size of turbo for maximum power. This may not suit your driving style, but again that's another story. The compressor map doesn't tell everything (just like the dyno sheet) but it's an important part of the puzzle.

Ahem. As we've hinted, there are significant advantages to larger turbos in terms of two issues:

1) volumetric efficiency (or the pump-work losses of the compressor, turbine, and exhaust manifold)
2) the thermal efficiency (or how close to adiabatic the compression cycle is)

Both of these issues mean that the twins will generally produce more heat at a given pressure and will have more resistance than a large single, which will mean less power. For reference, a T04S in one of its popular trims running at 17.5psi is flowing about 460CFM at peak efficiency (.75). If you want 550CFM, you drop to about .72 efficiency which is not bad at all (but it does mean more heat).

The biggest gain people see with the "non-sequential twins" modification is a reduction in exhaust port restriction which tends to choke the motor off at high RPM. Remember, the compressors and turbines are unchanged, and yet they pull 30-40 more HP from this mod alone. Think of it as another "porting" job on the exhaust. But you give up low-end response big time from both the porting and by making the turbos act in parallel. But even these guys stay around 15psi. I am not trying to rag on anyone running at 17psi on stockers, but there is no doubt that you're at the ragged edge of the compressor range.

While we're on the subject, you port a motor to reduce pressure losses at high RPM, thus increasing volumetric efficiency. However, it reduces the kinetic scavenging effect at low RPM, thus lowering efficiency for that rev range. It's always a trade off. Unless you have variable-port geometry. (This is what VTEC and such is all about; changing the geometry of the motor to optimize volumetric efficiency over the entire rev range.)

In short, CFM does have an effect, but only when the motor is pushing the turbo out of the high efficiency zone at your working pressure and RPM.

Okay, that's enough blabbing from m

myfc3s

iTrader: (2)

I would also say that yes "Bigger is better" The reason for this. I used to have the S5 turbo. Than changed recently with the T51. And hell big big difference on the same boost.
and the T51 doesnt really have a lag? It actually spools pretty fast. I mean running @8-10 psi feels like im boosting @14-16PSI or more on the S5 turbo.. And yes i do drive this car almost daily and im very very satisfied with this turbo..Also no its not a noisey turbo it's pretty quite until you do dump the throttle and wastegate open's..I have not took it to 15PSi or more because it feels really strong on 10PSi!! "Soon to boost 20+"tough hehe...

BNA_ELLIS

@.95bar my hks t51r produces can't remember exactly approx 427rwhp
What I do remember was full boost .95bar was 4500rpm

myfc3s

iTrader: (2)

How do you guys calculate "bar boost"-----"pounds of boost"?