Boost question
#2
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Car: 87 Iroc
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Re: Boost question
As much as you're willing to risk
Assuming no smoke or problems to begin with, and a good tune, it would very reliably handle 12-13 psi intercooled without any problems. You could have some luck and get away with 14-16 psi for a long term. Beyond 16 psi you are definitely starting the timer, but even then there are some guys around that have done so without problems.
Assuming no smoke or problems to begin with, and a good tune, it would very reliably handle 12-13 psi intercooled without any problems. You could have some luck and get away with 14-16 psi for a long term. Beyond 16 psi you are definitely starting the timer, but even then there are some guys around that have done so without problems.
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Car: 83Z28 HO
Engine: Magnacharged Dart Little M 408
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Re: Boost question
Not if it's timed/tuned properly. But as ZZ3Astro said - - A decent overall engine and tune is critical. Even at 6 pounds of boost, if the tune is way off, it can destroy the engine. For instance, I thought I had my engine dialed in pretty well (it ran awesome) until I put it on a Mustang dyno and found out that I was detonating like crazy in the upper RPM's. But yeah, that's a bunch of boost to begin with, but note that ZZ3Astro said "intercooled" boost.
I'd personally limit myself to 5-8 pounds using pump gas on a stock bottom end. No real reason why....but you'd need to back off on a whole lot of advance at anything above that on pump gas. If nothing else it's a bit less stress. You'll feel a huge improvement nonetheless.
"Assuming no smoke or problems to begin with, and a good tune"....
I'd personally limit myself to 5-8 pounds using pump gas on a stock bottom end. No real reason why....but you'd need to back off on a whole lot of advance at anything above that on pump gas. If nothing else it's a bit less stress. You'll feel a huge improvement nonetheless.
Last edited by Confuzed1; 08-12-2011 at 12:39 PM.
#5
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Re: Boost question
Originally Posted by 86yellowirocz
How much boost can a stock 305 take?
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Re: Boost question
Seems high but I speak from 10,000 miles of experience turbocharging a stock 5.7 with the numbers I posted. I've always felt that the 5.0 is a bit more more durable so I actually consider my numbers a tad conservative.
You will hear stories about people blowing up stock engines with 7 psi and yet other people succeed with 20 psi on the same type of engine. The difference is the person 99% of the time. One cuts corners and tries to run a stock fuel pump, injectors, etc with a FMU. The other builds a supporting system of properly sized injectors, a good fuel system and a properly tuned fuel/spark control system. One blows up and the other lasts for years. Of course you'll only hear about the one that blew up, because that's more exciting to talk about on the forums.
As an illustration of this.. I have a friend with a Vortech on a stock engine. It's blow-thru and do you think he has a WB02 on it? Reminds me of the old days with an 8-71. Blast down the road, come back and remove the plugs. Oops looks rich, lets try smalller jets. Detonation? Couldn't hear that if we tried. Just have to run a conservative set of springs & weights. Oops got a head gasket. Damn that 8-71 is H-E-A-V-Y to lift off the lower intake! Been there
You will hear stories about people blowing up stock engines with 7 psi and yet other people succeed with 20 psi on the same type of engine. The difference is the person 99% of the time. One cuts corners and tries to run a stock fuel pump, injectors, etc with a FMU. The other builds a supporting system of properly sized injectors, a good fuel system and a properly tuned fuel/spark control system. One blows up and the other lasts for years. Of course you'll only hear about the one that blew up, because that's more exciting to talk about on the forums.
As an illustration of this.. I have a friend with a Vortech on a stock engine. It's blow-thru and do you think he has a WB02 on it? Reminds me of the old days with an 8-71. Blast down the road, come back and remove the plugs. Oops looks rich, lets try smalller jets. Detonation? Couldn't hear that if we tried. Just have to run a conservative set of springs & weights. Oops got a head gasket. Damn that 8-71 is H-E-A-V-Y to lift off the lower intake! Been there
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#8
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Re: Boost question
As much as you're willing to risk
Assuming no smoke or problems to begin with, and a good tune, it would very reliably handle 12-13 psi intercooled without any problems. You could have some luck and get away with 14-16 psi for a long term. Beyond 16 psi you are definitely starting the timer, but even then there are some guys around that have done so without problems.
Assuming no smoke or problems to begin with, and a good tune, it would very reliably handle 12-13 psi intercooled without any problems. You could have some luck and get away with 14-16 psi for a long term. Beyond 16 psi you are definitely starting the timer, but even then there are some guys around that have done so without problems.
I'd be pretty surprised if it would be so limited that e85 would make a significant difference. I'd expect that the bottom end would fly apart before detonation limits things with a good tune.
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Re: Boost question
Boost pressure is just a measure of resistance. It can essentially be a higher reading depending on how restrictive your intake passages are, or it can be a lower reading depending on how large your intake passages are. Mind you, you will be flowing more air with larger passages and a lower boost pressure reading, so the measure itself is really meaningless. ....
Boost is not a measure of restriction. An engine by itself is not a restriction . dirty airfilter, clogged catalytic convertor,throttle are restrictions.
#10
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Re: Boost question
Originally Posted by daverr
this is a common misconception. Boost is not a measure of restriction.
Originally Posted by daverr
An engine by itself is not a restriction....
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Car: 83Z28 HO
Engine: Magnacharged Dart Little M 408
Transmission: G Force 5 speed
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Re: Boost question
I'm not getting into the discussion about boost pressure (OK I guess I am ), but I can tell you what I've found with my particular setup. The pulley that was provided with my Magnacharger should have provided 5 pounds of boost on a stock engine. My engine was far from stock before I put it on i.e. Comp cam, Dart heads, headers bla.bla...
Anyways, I only managed to get 2.5 pounds of boost with that pulley and had to change to a smaller pulley in order to increase blower speed/pressure. Of course, this is with a roots type blower, but the basics are the same as turbo, centrifugal blower or whatever. Biggest differences being where you see max boost pressures at.
If your engine has the ability to USE the boost, the pressures won't stack up as compared to an engine that can't breath as well. My install instructions for the blower state pretty much the same thing. The vast majority of power gain will be at those lower boost levels. At increased pressures they'll be gains since air is compressible, but they won't raise nearly as sharply as it was at the initial lower boost pressures.
A WBO2 is always a great thing to have with or without a blower. Tuning as far as timing and A/F ratios are a different ball game between roots type and centrifugal/turbo blowers though. There's no WBO2 that I know of that'll tell you if there's detonation occuring at the upper RPM range, or maybe I don't know how to use one properly since I'm a rookie myself at this forced induction thing...but I'm learning.
Anyways, I only managed to get 2.5 pounds of boost with that pulley and had to change to a smaller pulley in order to increase blower speed/pressure. Of course, this is with a roots type blower, but the basics are the same as turbo, centrifugal blower or whatever. Biggest differences being where you see max boost pressures at.
If your engine has the ability to USE the boost, the pressures won't stack up as compared to an engine that can't breath as well. My install instructions for the blower state pretty much the same thing. The vast majority of power gain will be at those lower boost levels. At increased pressures they'll be gains since air is compressible, but they won't raise nearly as sharply as it was at the initial lower boost pressures.
A WBO2 is always a great thing to have with or without a blower. Tuning as far as timing and A/F ratios are a different ball game between roots type and centrifugal/turbo blowers though. There's no WBO2 that I know of that'll tell you if there's detonation occuring at the upper RPM range, or maybe I don't know how to use one properly since I'm a rookie myself at this forced induction thing...but I'm learning.
#12
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Re: Boost question
Originally Posted by Confuzed1
Anyways, I only managed to get et 2.5 pounds of boost with that pulley and had to change to a smaller pulley in order to increase blower speed/pressure. Of course, this is with a roots type blower, but the basics are the same as turbo, centrifugal blower or whatever. Biggest differences being where you see max boost pressures at.
If your engine has the ability to USE the boost, the pressures won't stack up as compared to an engine that can't breath as well. My install instructions for the blower state pretty much the same thing. The vast majority of power gain will be at those lower boost levels. At increased pressures they'll be gains since air is compressible, but they won't raise nearly as sharply as it was at the initial lower boost pressures....
If your engine has the ability to USE the boost, the pressures won't stack up as compared to an engine that can't breath as well. My install instructions for the blower state pretty much the same thing. The vast majority of power gain will be at those lower boost levels. At increased pressures they'll be gains since air is compressible, but they won't raise nearly as sharply as it was at the initial lower boost pressures....
#13
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Re: Boost question
what your really need to be concerned with is the amount of air the turbo can flow .15 lbs. of boost out of a gt 25 is far less air then lets say 15 lbs out of a t88 . bottom line is your timing has to be perfect an you have to have the right amont of fuel for the air coming in .then comes the real problem how much horsepower can your parts handle .i think assuming the tune is ***** on then the real question is how much horsepower a stock 305 can handle before you break the bottom end .
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Re: Boost question
Wrong. Boost is a measure of restriction, period. If you are claiming that it isn't a measure of restriction then you are going to have to prove that it isn't, not just label it a common misconception without any clarification....
Wrong. A stock cylinder head is more of a restriction than an aftermarket cylinder head. A stock intake manifold is more of a restriction than an aftermarket intake manifold. A stock camshaft is more of a restriction than an aftermarket camshaft. All of these items directly effect the amount of air that enters into the combustion chambers, and all of these items directly effect the amount of boost pressure being embellished. If these items were not a restriction, then boost pressure would not be effected when modifications are made to the intake tract, but it is of course effected, because boost pressure is a measure of the air tract's restriction....
Wrong. A stock cylinder head is more of a restriction than an aftermarket cylinder head. A stock intake manifold is more of a restriction than an aftermarket intake manifold. A stock camshaft is more of a restriction than an aftermarket camshaft. All of these items directly effect the amount of air that enters into the combustion chambers, and all of these items directly effect the amount of boost pressure being embellished. If these items were not a restriction, then boost pressure would not be effected when modifications are made to the intake tract, but it is of course effected, because boost pressure is a measure of the air tract's restriction....
If boost was a restriction than the more psi you make the less hp you make.
clearly this is not the case.
#16
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Re: Boost question
Yes, if you see 30psi on the gauge at the same airflow as another engine or combination sees 15, then that engine is a bigger "restriction" than the one that sees a lower boost pressure.
In your example, the same engine sees different intake pressure with different amounts of air trying to be forced through the engine. The engine can only flow X volume air, and if you try to force more the pressure has to increase, increasing the air density to get that amount through the engine. The volume stays roughly the same, the engine is a restriction to more flow, but if you increase the density you can increase the mass of air that you can force through it without it being able to ingest any more volume of air.
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Re: Boost question
I'm not sure that I agree with the exact wording that either side of this has used, but getting past that you're wrong.
Yes, if you see 30psi on the gauge at the same airflow as another engine or combination sees 15, then that engine is a bigger "restriction" than the one that sees a lower boost pressure.
In your example, the same engine sees different intake pressure with different amounts of air trying to be forced through the engine. The engine can only flow X volume air, and if you try to force more the pressure has to increase, increasing the air density to get that amount through the engine. The volume stays roughly the same, the engine is a restriction to more flow, but if you increase the density you can increase the mass of air that you can force through it without it being able to ingest any more volume of air.
Yes, if you see 30psi on the gauge at the same airflow as another engine or combination sees 15, then that engine is a bigger "restriction" than the one that sees a lower boost pressure.
In your example, the same engine sees different intake pressure with different amounts of air trying to be forced through the engine. The engine can only flow X volume air, and if you try to force more the pressure has to increase, increasing the air density to get that amount through the engine. The volume stays roughly the same, the engine is a restriction to more flow, but if you increase the density you can increase the mass of air that you can force through it without it being able to ingest any more volume of air.
restriction is based on flow which a boost gauge cannot tell you.
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Re: Boost question
hey one of my boosted engines did that. I put a set of valve seals in it which cleared up the smoke. As for the ticking noise it has right now, well, it always had that noise for over 30K miles and still runs fine with boost.
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Re: Boost question
Dave, Mark,
You guys have a good understanding of how boost works. I am surprised to see two knowledgable people arguing it.
You guys have a good understanding of how boost works. I am surprised to see two knowledgable people arguing it.
#22
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Re: Boost question
To be honest, I don't have the time to pay attention (or argue) around here that I used to, I don't know who dave is (who you are... i don't know, am I talking about you or addressing you in this... I think I'll settle with I'm going to go back and forth) and the fact is that most of what you've written is technically incorrect, and as far as the last post goes if you have a given volume air flow and a pressure you know (can calculate) the restriction, adiabatic efficiency... or if you know the volume flow at 2 pressures (atmo and after the turbo) you can calculate the volume flow, change in density (and again, adiabatic factors also)... or you can look at it a few different ways, but no matter how you slice it you are showing a restriction and it's not hard to calculate.
#23
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Re: Boost question
Dave, I'm not going to argue with you because you are wrong. Boost is most certainly a measure of resistance for the particular engine, and explaining why for you in the greatest detail will do very little because you simply refuse to see it. I have argued this same fact with you in the past before, whether on here or on other websites. Not only do you claim that boost pressure isn't a measure of resistance, but you are also very adamant about saying how blow-thru carburetors don't work, and how it takes $25,000 dollars to build a good turbo setup. You are wrong on all three accounts....
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