guttedsilvercrx

i hear alot from you guys not to boost much on a stock engine, not over like 10 psi say, if thats on a T-25 and your boosting 10 psi, is that the same 10 psi thats coming out of a say 60-1?

Overblown-Teg

psi is a measure of pressure so yes 10psi is 10psi.. What they are refering too is air density.. the small turbo will be out of its efficiency range and super heating the air making it less dense and there for less hp.

HXMan

a t25 at 10 psi will push a much smaller quantity of air then a 60-1 at 10psi.

Chillinit

10 psi is 10 psi ...true...but you have to remember "FLOW". 10 psi out of a small turbo will flow less air(volume of air) then a bigger turbo running 10 psi...

VTC_CiViC

Just think of fuel pumps. Sure you can push 80psi from a Civic pump... but how much fuel do you think that pump is flowing at 80psi? Now how about a larger high pressure pump at 80psi?

Fluid Dynamics

VTC- who wishes he paid more attention in school

Muckman

iTrader: (2)

This is one of those theories I believe because I have learned from Honda-tech to be a fact but dont understand.

It seems to me that 10psi would equal 10psi across the board. PSI is a measure of resistance. I am aware of the analogy with the straw vs drain pipe. But with engines, psi is a measure of the engines resistance to accept this incoming air.

You say 10psi from a T4 is alot more volume (cfm) than 10psi from a T25. Well the engine is going to resist more air from the T4, causing the psi (resistance) to get pushed up. Thats the part I dont understand.

haggar

Hmm,

10 psi IS 10 psi..

If the T25 was too small, and could not supply enough air volume, it would not be able to maintain 10 PSI. The engine would be inhaling the intake charge faster that the turbo could supply, and the pressure in the intake would drop.

bxsi

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by guttedsilvercrx &raquo;</TD></TR><TR><TD CLASS="quote">i hear alot from you guys not to boost much on a stock engine, not over like 10 psi say, if thats on a T-25 and your boosting 10 psi, is that the same 10 psi thats coming out of a say 60-1?</TD></TR></TABLE>

it's not really the boost pressure that breaks motors, it's horsepower. The don't boost over 10psi on a stock motor is like a rule of thumb in my opinion. If your gonna slap a turbo on a stock motor without any fuel/timing management then yes follow that rule of thumb. Otherwise you can fine tune a stock motor with how many psi it takes until you make the power that the motor itself can not handle like for example you could probably tune a stock motor to close to 2.5 times the power it made without boost, but the internals on that motor would probably not be able to take the horsepower and it would ultimatly start breaking **** at the first sign of detonation. The cylinder pressures increase to points the stock internals can't handle and will just break, but this doesn't necessarily mean it was because it was over 10psi on a stock motor.

Overblown-Teg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">This is one of those theories I believe because I have learned from Honda-tech to be a fact but dont understand.

It seems to me that 10psi would equal 10psi across the board. PSI is a measure of resistance. I am aware of the analogy with the straw vs drain pipe. But with engines, psi is a measure of the engines resistance to accept this incoming air.

You say 10psi from a T4 is alot more volume (cfm) than 10psi from a T25. Well the engine is going to resist more air from the T4, causing the psi (resistance) to get pushed up. Thats the part I dont understand. </TD></TR></TABLE>

If you read my post I think I explained it right.. at 10psi the small turbo and the large turbo are flowing the same cfm.. Because like you said psi is a measure of resistance.. it takes x cfm to make 10psi on a set engine. The difference is in the air density because of how the turbo is heating the air. The 60-1 is probably more efficient than the t25 and there fore is making a more dense air charge.

The straw and drain pipe analogy is more for comparing a stock intake mani and a jg mani. at the same 10psi..

Muckman

iTrader: (2)

I didnt think of the efficiency. You see tons of ppl making huge power from a SC61 at 10psi. I didnt think the density would make that much difference.
Thanks for clearing that up. Good to know I was on the right track.

Edit - I wanted to add, this is why turbos will always make more power than superchargers at a set psi. Just like a larger turbo will always make more power than a smaller turbo at a set psi. Of course thats a broad generalization but you get the idea.

Muckman

iTrader: (2)

One more question: does denser air increase CFM?

Overblown-Teg

My understanding is that the oxygen content changes. I could be wrong though.. there is alot of other stuff going on with coolers chilling the air and what not. I think What it comes down to is efficiency.. You can't always say bigger will make more power.. if an sc61 is size perfect for your setup a T88 won't make more power at the same boost. You will be in the low efficiency of that turbo.. The best thing to do is look at maps and figure out your plans then pic the turbo that best suits your needs.. I played with alot of maps and I found that from 10-18psi the sc61 will be in the peak island for my gsr.. it has the best map for my car as far as I could tell.

I'm sure that doesn't help much.. But I don't know all the technical gargon to through in there or the calculations to prove stuff.

Sohc Driver

well...to make it clear...is the general consensus agreeing that at 10psi on a t25 and 10psi on a t3/t4 is putting the same amount of air into the motor? And the difference will be the temperature/density of the air?

Khoi

mrmonk

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">I didnt think of the efficiency. You see tons of ppl making huge power from a SC61 at 10psi. I didnt think the density would make that much difference.
Thanks for clearing that up. Good to know I was on the right track.

Edit - I wanted to add, this is why turbos will always make more power than superchargers at a set psi. Just like a larger turbo will always make more power than a smaller turbo at a set psi. Of course thats a broad generalization but you get the idea.</TD></TR></TABLE>

Wouldn't the smaller turbo spool up quicker than the larger turbo thus delivering boost faster to the engine.

If what you guys say is true, why would they make smaller turbos in the first place???

Overblown-Teg

Efficiency.. some turbos are effiecent at 88lb/min of air flow and others are at 25lb/min.. Not everyone has a 800hp beast. If you have a sohc trying to push 225hp why would you want an enormous turbo that is barely even turning at 25lb/min and is at 60% efficiency.. when you could run a 14b that is about 70% efficient?

Ri5e

Suppose you have two boxes. Each box has a 2 inch inlet and a 1/4 inch outlet. If you were to connect a T25 to the first box's inlet and a T-66 to the second box's inlet and create a constant 10 PSI in each box, the second box's outlet CFM would be much higher than the first box. Since the T-66 flows so much more volume of air, it doesn't have to work as hard as the T25 to create the 10 PSI. And since the T-66 doesn't have to work twice as hard, it doesn't create as much heat.

That's why you can have a straw sized pipe pushing 30 PSI into the motor and it won't blow up vs pushing 30 PSI through a 2.5 inch pipe.

Ri5e

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Overblown-Teg &raquo;</TD></TR><TR><TD CLASS="quote">Efficiency.. some turbos are effiecent at 88lb/min of air flow and others are at 25lb/min.. Not everyone has a 800hp beast. If you have a sohc trying to push 225hp why would you want an enormous turbo that is barely even turning at 25lb/min and is at 60% efficiency.. when you could run a 14b that is about 70% efficient?</TD></TR></TABLE>

89dxhunchback

I kinda hate the "psi" measurement. Its not very accurate...
One guy on H-T makes like 206Whp@6psi on a SOHC and SVO 60-trim, but I'd bet we've seen the smaller "kit turbos", (greddy, Apexi) that only make like 180whp@10ish psi.

Psi is psi, but CFM should be what people use to measure a turbos output.

The power difference isn't that great simply b/c the bigger turbo makes cooler air, or work "less hard".

I bet a T-25 blows about 40% ( at least, maybe more ) less air at 10psi than a T3 60-trim.

89dxhunchback

volume = CFM
resistance = boost

Would you rather know what your motor isn't flowing ( PSI ) or what your motor IS flowing ( cfm ).

To bad there isn't a "CFM gauge", hehe..

Overblown-Teg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 89dxhunchback &raquo;</TD></TR><TR><TD CLASS="quote">I kinda hate the "psi" measurement. Its not very accurate...
One guy on H-T makes like 206Whp@6psi on a SOHC and SVO 60-trim, but I'd bet we've seen the smaller "kit turbos", (greddy, Apexi) that only make like 180whp@10ish psi.

Psi is psi, but CFM should be what people use to measure a turbos output.

The power difference isn't that great simply b/c the bigger turbo makes cooler air, or work "less hard".

I bet a T-25 blows about 40% ( at least, maybe more ) less air at 10psi than a T3 60-trim. </TD></TR></TABLE>The one making more power with less boost probably is not stock or it could be tuning or any other variables that change things. If as you say the T25 is blowing 40% less air than how is that lower volume maintaining the 10psi of resistance on the same engine? it can't

Lets try a different kind of example and see if it makes sense to you guys. Take an air compressor.. One has a huge tank the other a small one.. and the big one has a 1" line the other a 1/2". You set the regulator at 10psi.. and run it through the same air tool with a small orifice. They will both flow the same amount of air though that tool. It doesn't matter what size line you run if you set it to a certan psi it will flow the same air every time. its the resistance to flow that makes the psi.

Now with the same engine and a big and little turbo.. inorder to maintain the same psi both turbos need to flow the same amount of air.

Overblown-Teg

If what you guys are saying is correct then we should all just go with the biggest turbo made and be done with it.. We will get best results there no matter how much hp you make.. Going bigger will always make more power. That is just wrong.

guttedsilvercrx

ok so like most people say dont boost more than like 12 lbs on a stock motor, if i put a 60-1 on the stock engine can i still boost 12 lbs or will i have to boost less because the 60-1 has muchh more air flow than a t-25?

fulldragcrx

wow, alot of good brainstorming on this topic. but the original question was is 10 psi still 10psi regardless of turbo size? i think this is much more simple than others have made it. YES 10 psi is 10 psi with all other things being equal ( inlet temp, I C piping size etc). Pounds Per Square Inch, its like saying is 12 inches the same on a yard stick as it is on a ruler. PSI is a measurement of pressure and thats it.

FastNFurious

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Overblown-Teg &raquo;</TD></TR><TR><TD CLASS="quote">If what you guys are saying is correct then we should all just go with the biggest turbo made and be done with it.. We will get best results there no matter how much hp you make.. Going bigger will always make more power. That is just wrong. </TD></TR></TABLE>

Sure buddy, get a HUGE turbo so you can start boosting at 7k rpm.......

Johnyquest

I really wish I could help answer these questions, but I'm just as baffled as the rest. It seems that by the time anyone wants to make big power, they go to a big turbo... but is this just for the ability to maintain boost numbers in the 30+ range to redline? it seems feasible that a small turbo wouldn't be able to do that. As far as a psi = a psi from two different turbos, all logic seems to tell me it should. No matter how I think about it, minor efficiency differences aside, it seems to make sense that 1 psi = 1psi at all times, and the only reason for going to a bigger turbo is to allow for higher boost #'s, ie, maybe you can't hold 25psi on a t3 to redline... or can you? Has anyone tried!? That'd be interesting.