The design of the aluminum heads is definatley better, and they flow much more. The porting and polishing of the iron heads does make them flow better, but as far as a turbo application goes the design becomes less of a factor the more boost you add and the port work is less of a factor and the polishing is more of a factor. Most heads have little dimples, protusions, mold marks and other, for lack of a better word, chunks of metal sticking out into the flow stream. By polishing the flow path these irregularities are blended in with the metal around them so everything heats up more equally. When you have protusions that can heat up, they can act much like a spark plug and pre-detonate the fuel before it is supposed to. So a good port and polish on the intake, heads and exhaust will make them flow better, but it will also help with detonation. You also use a colder plug which helps.
this is just plain false.
if you have pressure in your intake plenum, all that means is that air isn't getting into the cylinders. a better flowing head will make more power on less boost every time. if you want to use the iron heads go ahead, it's your car, but don't say the flow doesn't matter or isn't a big deal because you're boosting it.
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Originally posted by Vanet: By having a cam with more overlap it bleeds off some compression for a moment until the valve shuts. Then the compression will still build to its maximum, it doesnt hurt your performance, it just acts like a clutch of sorts. kinda like the difference between reving your car and dropping the clutch, and easing the clutch out. Both accomplish the same thing in the end, but one way is much harder on parts. At least that is the way it was explained to me on a different turbo build we did last year. Van
but it does hurt performance, the whole idea is that you want to cram more air in so you can add more fuel and make a bigger bang.
No one ever said that a better flowing head would make more power everything else being equal. What I said is the higher the boost, the less difference the natural flow of the head makes. You are in your words "cramming" the air through it. No longer is air flowing because of vacuum. So the shape become less and less of a difference the higher the pressure goes. It is simple Physics.
As far as boost goes it only matters what your boost is at the time of compression. boost before compression can actually be hinderance. The secret is timing. That is the reason most turbo engines are decompressed some. It allows for more ultimate boost at the right time with out destroying the engine. By your theory you would want more compression because after you boost you would have more power. In reality that is wrong. I think you should do some research on turbos, instead of just blindly making statements. Thanks Van
The 3.4 and 3400 is NOT the same! Newer Gen III blocks have priority MAIN feed oiling, roller camshafts, cross bolted mains and integrated oil pan. I stated this before the pissing match started.
As far as a pissing match, I am still just trying to get information. Not sure why the other fellow keeps picking a problem with various ones, must be history I dont know about. I am hoping some one who has actually turboed a 3.4 or any other engine in a Fiero will come on with some good tips. Really dont need to discuss turbo theory. I have several turboed vehicles and understand how they work. I am just looking for advice on putting together the best combination for this engine in a Fiero. So Thank you for your information and all others who are contributing helpful info. Van
No one ever said that a better flowing head would make more power everything else being equal. What I said is the higher the boost, the less difference the natural flow of the head makes. You are in your words "cramming" the air through it. No longer is air flowing because of vacuum. So the shape become less and less of a difference the higher the pressure goes. It is simple Physics.
As far as boost goes it only matters what your boost is at the time of compression. boost before compression can actually be hinderance. The secret is timing. That is the reason most turbo engines are decompressed some. It allows for more ultimate boost at the right time with out destroying the engine. By your theory you would want more compression because after you boost you would have more power. In reality that is wrong. I think you should do some research on turbos, instead of just blindly making statements. Thanks Van
simple physics? I have no problem breaking it down to simple physics. engines operate based on differential pressure, there is still a vacuum in the cylinder pulling air in when the intake valve opens. the increased intake track pressure doesn't change this. the exhaust backpressure may reduce the vacuum, but there will still be some there.
if you have less resistance to flow, the system can move more air easier, and therefore make more power. you can add more boost to an engine with crappier flowing heads, sure, that doesn't make them flow better, or support more power, the same intake pressure level on an engine with better flowing heads will admit more air into the cylinder, and therefore make more power. all other things being equal the engine with better heads wins. the turbine in the exhaust housing of a turbo takes energy to run, yeah it's more efficient then a typical belt driven blower, but it's not "free energy" as so many people think.
your second statement goes against most everything I've seen done on a street driven turbo car. you want to decrease overlap so you keep more air in the cylinder, again, that's kinda the whole point of turbocharging. if you're worried about destroying the engine, you didn't plan out your build very well.
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Originally posted by Vanet: As far as a pissing match, I am still just trying to get information. Not sure why the other fellow keeps picking a problem with various ones, must be history I dont know about. I am hoping some one who has actually turboed a 3.4 or any other engine in a Fiero will come on with some good tips. Really dont need to discuss turbo theory. I have several turboed vehicles and understand how they work. I am just looking for advice on putting together the best combination for this engine in a Fiero. So Thank you for your information and all others who are contributing helpful info. Van
if you think I'm an ******* , whatever, I don't really care, like I told lou, I call out BS when I see it, if it offends, I'm not sorry.
FYI, my car is a turbo 3500, I don't mind sharing tips, but I'm not going to waste my time either.
Talk to whoever did your turbo for you, so they can help you with the physics. Until then, I do appreciate your uh "tips", but all i have really seen from you is attacking one person or another who doesnt happen to agree with you.
This is not a thread about which heads are better. You win!! the aluminum heads flow better. The newer engines are better built and make more power. (why do you think they changed them? duh) Happy now? So go crawl back under the rock you came from and leave us alone. IF you ever have any real, positive, helpful advice by all means post it. BUT if all you want to do is fight about weather an engine with old technoligy is better than an engine with newer technoligy is better, I DONT want to hear it. I made my decision and dont care how you feel about it. I am lookng for some advice from people who want to be helpful, on how to make this engine and turbo combination work the best. So piss off. Thank you and have a nice day! Van
HP = .2575 x CFM (@ 28" of water) x number of cylinders
So we have iron heads that can flow 182 cfm when fully ported and polished, hence there is peak potential for 282 hp. It doesn't matter if AL can flow about 300+HP's worth as we're not building racing motors here that spin to 8000rpm, but street motors. Heads are not the restriction. It comes down to cam, intake and exhaust. "Stock", AL head motors have better supporting parts, but putting those motors in our cars is more of a hassle and it's just easy to machine the stock Fiero parts to flow more air. That has always been my view. Comparing builds is useless since no two are alike.
Build the motor you are comfortable with, no one else's opinion really matters.
Everyone seems to just skip over the fact that an aluminum head engine can handle more boost due to the combustion chamber design. They are much less prone to detonation, and there is just nothing that can be done to iron heads to equal the aluminum heads in that area. The crank and rods are the same in the 3.4 and 3400, the pistons are the same design, only different to take into account the different volume of the two different combustion chambers. Also, boost does nothing to get the exhaust out of the cylinders, except obstruct it some due to driving the turbo and having a cam that is ground to compensate for the losses you end up with in the exhaust. If you want the best iron head 3.4 you can build, start with a 3400 block and put the 3.4 pistons in it, you can then use either a flat tappet cam or a roller cam and you get better oiling etc, but you will never make as much power as if you did the same amount of work on a 3400. Larry
Talk to whoever did your turbo for you, so they can help you with the physics.
I built my car, for the most part, I don't pay people to do things for me. I do them because I enjoy making something from more or less nothing.
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Originally posted by Vanet: This is not a thread about which heads are better. You win!! the aluminum heads flow better. The newer engines are better built and make more power. (why do you think they changed them? duh) Happy now? So go crawl back under the rock you came from and leave us alone. IF you ever have any real, positive, helpful advice by all means post it. BUT if all you want to do is fight about weather an engine with old technoligy is better than an engine with newer technoligy is better, I DONT want to hear it. I made my decision and dont care how you feel about it. I am lookng for some advice from people who want to be helpful, on how to make this engine and turbo combination work the best. So piss off. Thank you and have a nice day! Van
I'm not trying to fight about what heads are better, I know what heads are better, I understand why certain heads are better, I'm trying to understand some of your posts and some of the info you have posted. Maybe I should just ask you why the heads/port design doesn't matter on a turbo car, this statement in particular doesn't add up to me
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Originally posted by Vanet: but as far as a turbo application goes the design becomes less of a factor the more boost you add and the port work is less of a factor and the polishing is more of a factor.
Could you please explain this, and I'm not trying to be an as s, if I come off that way, I guess I just have an abrasive personality. I'm honestly trying to figure out what you mean by this.
if you're saying you can increase the boost pressure to compensate for the lower port flow, this is true, but you could do the exact same on any boosted engine and net a gain. the problem starts to arise when you increase pressure to high you start to reduce the efficiency of the turbo and just heat air up instead of compressing it, or start surging.
[This message has been edited by ericjon262 (edited 04-22-2014).]
Originally posted by Vanet: What I said is the higher the boost, the less difference the natural flow of the head makes.
No longer is air flowing because of vacuum.
As far as boost goes it only matters what your boost is at the time of compression. boost before compression can actually be hinderance. The secret is timing. That is the reason most turbo engines are decompressed some. It allows for more ultimate boost at the right time with out destroying the engine. By your theory you would want more compression because after you boost you would have more power. In reality that is wrong.
The higher the boost, the MORE difference good heads make. Flow through as tube is proportional to the square root of pressure difference... At high pressure differences, the extra boost counts for a lot less that a change in cross-sectional area and discharge coefficient of the tube.
Air never flows into an engine because of vacuum. It always flows in because of manifold pressure.
A 10:1 turbo engine running 15 psi of boost will make more power than the same engine with 8:1 compression running 15 psi of boost. That's the nature of the Otto cycle. The only reason turbo engines are built with lower compression is fuel quality. The 8:1 engine doesn't need as much octane as the 10:1 engine to avoid detonation.
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Originally posted by Vanet: I have several turboed vehicles and understand how they work.
Talk to whoever did your turbo for you, so they can help you with the physics. Until then, I do appreciate your uh "tips", but all i have really seen from you is attacking one person or another who doesnt happen to agree with you.
Could you please explain this, and I'm not trying to be an as s, if I come off that way, I guess I just have an abrasive personality. I'm honestly trying to figure out what you mean by this.
if you're saying you can increase the boost pressure to compensate for the lower port flow, this is true, but you could do the exact same on any boosted engine and net a gain. the problem starts to arise when you increase pressure to high you start to reduce the efficiency of the turbo and just heat air up instead of compressing it, or start surging.
In Flow dynamics, the resistance that is exerted on the air from the surface of an object doesnt change. It is a constant as the volume and pressure are raised more air flows. If you are compareing 2 different objects that have different flow charactaristics they will both always have there same resistive effect on the air. Now if you are concerned with volume as you are with an engine, you pump air in one side, and you get air out the other side. As long as you can supply enough fuel the more air you supply the more HP you will get. In a NA engine the air, the resistance to flow and the fuel are in relation to each other fairly constant. so small changes to the flow of a head make a difference. Once you add an air pump the amount of air that can be pumped in is a lot more, but the resistance to that air is still constant. A basic formula would be lets say the iron head is a 1. The aluminum head is a 2 that means the AL head is twice as good as the iron head. I dont know if that is true, but this is very simplistic as an illustration. Now if we call the ambient air on a NA engine a 1 also, and then add them together you get 2 for the iron head and 3 for the aluminum head. The aluminum head is 33% better than the iron head. Now lets say we add a turbo and the air now becomes a 10. Now we add 1, the iron head, to it and we get an 11. We add 10 to the AL head and we get a 12. The iron head will never catch the AL head it isnt as good a design but now look at the % of difference now it is only 8 % instead of 33%. And the higher the flow rate the closer they will get.
Now I can already hear some of the more math and science inclined yelling BS. They are right in the real world there are a bunch of factors that would make this way too simplistic. However the relationship of air to resistance will always follow the relationship noted above.
Way back in Physics in highschool ( a long time ago for me) they demonstrated this with 2 straws. one was smooth, and the other was one of those bendy ones with the ripples in it from top to bottom. They had us blow through them and measure the air. It was all over the place because we all blew different, but we got a chart top to bottom and averaged it out. The Mr. Jacobs (our physics teacher) brought out a compressor and shot air through the straws. The smooth straw always flowed more than the rough straw, however it was signiffigant when we were blowing through the straw, and almost unmeasureable when the compressor was used.
So what have we learned. The Iron head will alway be inferior to the AL head, and if your goal is the most HP then the AL head will always win. But if you are shooting at a certain number both will get there it will just take a little more boost with the iron head. Look at it in terms of HP. The 3400 makes about 30 to 40 HP more than the 3.4 from what I have heard. At stock levels, that is a big difference. Now lets say we boost them both to 20 lbs. The 3400 will still be 30 or 40 HP ahead of the 3.4 but now they are both making 300+ HP and the difference is less noticeable. Also both engines have probably blown apart at this time. But let say we have super engines that will hold anything. Lets boost them up to 1000 HP. The iron head will still be behind the AL head but now the difference would be almost un noticable.
Again some are going to call BS. And the would be right. The HP difference would be larger as you went up. But you would still eventually get to a place were they were so close you would nt notice. Yes there are hundred of different factors that make these senarios impossible. However the relationship we are talking about is correct. The higher you go in boost the less difference the flow of the head will make.
Let the attacks begin if you must. But I am still just wanting to talk about making real world HP with the 3.4 engine I have on the stand in my shop. Thanks Van
Anything positive to add?? NO, then just move along please. Thanks
Another failure to acknowledge real world technical points that conflict with your ideas.
Your analysis is fatally flawed. You assume all effects are additive. They are not. They are multiplicative. The power difference between iron head and aluminum head engines will be MUCH LARGER at higher boost pressures.
Will your wrong, but no matter how many times we go back and forth it isnt going to get us anywhere, so why dont you move along and we will get back to discussing tips for building a 3.4 for a turbo to get to around 300HP in my application. Thank you for your cooperation. Van
P.S. Did you even read what you linked to, not even remotely on topic. All I have said is restriction of an object that air flows through is a constant no matter how high the volume or pressure go. It is basic HS Physics, no matter how much you dispute it. You cant cross over from air to water for one thing air compresses and water doesnt. But even if you could the site has no bearing on the topic under discussion. Your last name wouldnt be Bowden would it? I had a will by that name in a class one time who was very difficult to teach kinda like you. Maybe just a coincidence.
[This message has been edited by Vanet (edited 04-23-2014).]
Vanet, I think you've oversimplified things to a fault where it's not really applicable anymore. I realize you've made your decision but we can all learn from the discussion. Personally I like where you are going with the build, and I am curious how much power you will be able to get out of the 3.4 and iron heads. But you aren't going to get much help dismissing other forum members.
I am not dismissing the forum members, it is just one or two guys that seem to want to stir something up. And you are right I said more than once that the illustrations I was using were overly simplistic just so those who dont have a science background would understand what I was talking about. I havnt taught physics in years, but I dont remember people being so obtuse.
I have only made up my mind as to what engine I am going to use. I am still open to ideas from people who know the motor as to how best to get to where I want to go with it. I have stated that over and over. But I keep getting these couple of guys who want to debate stuff that has nothing to do with the thread. In doing this they are chasing off people who would actually like to talk about the build. I have already had one person PM me and tell me to start a new thread so I can lose these guys and get back to the topic at hand. But it is my thread, and I thought if I asked nicely they would be man enough to back off and let those of us interested in the build, to continue a useful discussion on building a 3.4 turbo specific engine. So far that hasnt happened.
However I am still trying. So if you want to debate why I choose the wrong engine or how little I know and how much you know, or anything else that isnt Fiero 3.4 swap related just be kind enough to move along and start a thread of your own. It looks like you will get plenty of people to debate with, and we can get back to the matter at hand. Thanks
Meso: thanks, I am not sure exactly how much power I will make, there are too many variables. But I have a good example of someone who has done this build and made 301 HP @ 18lbs of boost on a virtually stock 3.4 with a very mild cam. I am hopeing to free up the exhaust, the intake, and the heads. Go with a little more aggressive cam and maybe get to 300 with about 14 to 16 lbs of boost. Will I? I dont know, but I am going to have fun trying. Thanks Van
I havnt taught physics in years, but I dont remember people being so obtuse.
If you've actually taught Physics at higher than a 2nd grade level, you'd understand the link I posted and why it's applicable. I know a thing or two about Physics, as I have a degree in it.
You'll hit 300 HP with a turbo iron head 3.4... that's not in doubt. Achieving that will happen despite, rather than because of, your "expertise". The community here can help you out with all the online turbo calculators you can use. You should trust that source rather than your own calculations.
Everything I post is to help you learn
[This message has been edited by Will (edited 04-23-2014).]
I have only made up my mind as to what engine I am going to use. I am still open to ideas from people who know the motor as to how best to get to where I want to go with it.
It's sad when a simple question becomes a WW3 debate on a forum.
Build what you will. I'm running what others would never have done as well - and it works!
A 3400 roller cam block, DOHC crank, rods and pistons, topped with Fiero iron head top end. With those pistons, I'm running 9.5 - 9.75 :1 compression ratio. Then I have 6-8 lbs boost ON TOP of that. Those who've ridden in it can't believe the torque and pulling power for a V6. California Kid can attest to that - gave him a short run at the 20th Anniversary Show
Maybe, maybe not. They might look like it, but be better flowing parts. Either way, if it achieves rated power in the original application with those, and they make the swap easier, it sounds like a deal sealer to me.
I have a degree in Applied science. I taught physics in HS for 1 year and college for 2 before deciding teaching wasnt for me. If you do really have a degree in physics, then you are just trying to cause trouble, which is what I thought all along.
So please just move on. I am not an expert at turbocharging or 60' v6 engines, and that is why I am here asking for advice on the best way to do it.
So for the 10th time will you just get a life and stay out of this post so we can move on. Thank you!!!
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Originally posted by Will:
If you've actually taught Physics at higher than a 2nd grade level, you'd understand the link I posted and why it's applicable. I know a thing or two about Physics, as I have a degree in it.
You'll hit 300 HP with a turbo iron head 3.4... that's not in doubt. Achieving that will happen despite, rather than because of, your "expertise". The community here can help you out with all the online turbo calculators you can use. You should trust that source rather than your own calculations.
It's sad when a simple question becomes a WW3 debate on a forum.
Build what you will. I'm running what others would never have done as well - and it works!
A 3400 roller cam block, DOHC crank, rods and pistons, topped with Fiero iron head top end. With those pistons, I'm running 9.5 - 9.75 :1 compression ratio. Then I have 6-8 lbs boost ON TOP of that. Those who've ridden in it can't believe the torque and pulling power for a V6. California Kid can attest to that - gave him a short run at the 20th Anniversary Show http://fierosound.com/34engine/3400details.htm
Sounds like a great build.
Why the mish mash of parts. If the 3.4 and the 3400 is the same bottom end, what was accomplished by changing the crank and pistons in your build? After using the 3400 block, why the iron heads if the AL heads flow so much better? I am planning to completely rebuild the 3.4 and at this time can use what ever parts will work the best with out changing the budget or time frame too much. Thanks Van
the 3.4 and 3400 ARE NOT the same blocks... as stated earlier by sleevePAPA 2x now
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Originally posted by sleevePAPA:
The 3.4 and 3400 is NOT the same! Newer Gen III blocks have priority MAIN feed oiling, roller camshafts, cross bolted mains and integrated oil pan. I stated this before the pissing match started.
When you put iron heads on a 3400 block without changing pistons, you end up with a compression ratio in the mid 7's. Aluminum heads have smaller combustion chambers and the pistons have a larger dish than 3.4 pistons. Using 3.4 DOHC pistons with iron heads raises the compression ratio between 9.7ish and 9.965 depending on your bore and what head gasket you used.
Fierosound's motor and my motor are considered "hybrids" since we combine parts from the Fiero, 3400 and 3.4 TDC motor. The only custom parts needed to make it work are 5.85" pushrods and stud adapters for 1.6 roller rocker arms... A website WOT-TECH sells some high lift roller cams for the 3400 block. I haven't looked in a while but there may be a turbo grind there too.
I guess you could say that the 3400 block is an improved 3.4 block. It has the built in ability to run a roller cam and it has improved oiling. It also has the starter on the proper side for a Fiero. The crank and rods are the same, as are the bearings. Flywheel and front timing cover and harmonic balancer fit. If you had two bare blocks sitting there it would be foolish to choose the 3.4 over the 3400. You can run a flat tappet cam in a 3400 if you want. Larry
Originally posted by Vanet: I am not an expert at turbocharging or 60' v6 engines, and that is why I am here asking for advice on the best way to do it.
You said you were an expert in turbocharging...
If you go to the Wiki link I posted, and find equation (2) under "Incompressible flow through an orifice" and equation (3) under "Flow of gases through an orifice", you'll see that both volumetric and mass flow rates are proportional to the square root of pressure difference, while being directly proportional to the discharge or flow coefficients and directly proportional to the cross sectional area of the orifice. This means that a given percentage change in the cross sectional area and/or the discharge or flow coefficient have a MUCH greater effect on flow through the intake port of an engine than the same percentage change in manifold pressure. It also means that as manifold pressure goes up, each subsequent % of increase results in less and less flow through the port. This means that at high boost, increasing the cross sectional area and/or the discharge/flow coefficients via swapping to aluminum heads or port work has, *relative* to increases in boost pressure, a MUCH GREATER EFFECT.
So, with regard to the flow characteristics of an engine as they related to boost pressure...
EVERYTHING YOU'VE SAID IN THIS THREAD IS INCORRECT.
[This message has been edited by Will (edited 04-24-2014).]
One of the reasons Al heads outflow Fe heads is because the Al heads use 8mm diameter valve stems and the Fe heads use 11/32". The valve stem is an obstruction to the airflow. There is an OEM intake valve, I didn't write down the p/n when I was at the shop (also I forget if it's 1.72" or 1.76"), that is within .02" of the height of the Fiero intake valve and is 8mm diameter which a machine shop told me won't make a difference (height-wise). This would mean only an exhaust valve would have to be sourced and that the iron heads would out-flow what has been traditionally reported.
[This message has been edited by lou_dias (edited 04-24-2014).]
Don't you have a set of racing heads that you try to pass off as stock heads? The 3500 manifolds will fit the fiero without cutting the trunk if you fab up duel exhaust. I made mine out of 2.25 mandrel bends. The 3500 has a cast steel crank if you are going to turbo the car.
[This message has been edited by jdv (edited 04-24-2014).]
The 3500 has a cast steel crank if you are going to turbo the car.
not *ALL* of them, just most. mine has the steel crank, and from whats been reported they also have powedered metal rods, bottom ends of 3500's have held 500+ with boost several times, the 3400's are usually little over 300, at bout 9-10lbs, 18lbs of boost and your bending rods or worse.
i plan on putting a turbo cam, some LS6 springs, and dropping about 8lbs on it... after lots of research, i should be close to 350 or so (might need some porting, but should be close)
Someone showed me the other fiero forum were Will normally plys his crap. While at the same time running down Archie and others that have actually done stuff in the Fiero world. Now I understand. He is one of these wanna bes that lives in his moms basement and hates everybody out doing while he tells everyone how smart he is.
SOOO WILL how is that 7year project to put an LS in a Fiero coming anyway. LOL Thanks for your comments, but several people who are trying to be helpful are doing just fine, so you can move along!
