Turbo vs. Blower psi?

[ice87]

http://www.hondatuningmagazine.com/tech/htup_0805_500hp_stock_block_b16a/viewall.html
Found this article: 505hp 340lbs Honda 1.6 but it spins to 8,000 and has to be running 24psi. To me that's not that great. Alot of money for not alot of power.

[xjs3667]

After reading a few articles about the differences and similarities I still can not find a definitive answer, but have come to conclude a few things that we all forgot to mention.... and it involves simple science....

A turbo and vortec supercharger are almost always hooked up to an inter-cooler.
What does it do exactly?  it takes the "exhaust" air from the turbo, etc. and cools down to be more efficient in the combustion process.

I have only very rarely seen a roots style blower hooked up to an inter-cooler unless running very low psi, which then itd really just for show.  some are that are mounted directly to the manifold have cooling jackets, for the antifreeze to help cool the exhaust air on them. As we all know what our normal coolant temp. is  180-200 est. I would say it is not the best method to cool it.

Also I know for a fact that on the blower I have the exhaust temps are right around 250-300 degrees, exceeds 300 degrees in full boost, this is only at 6psi !!   

Now the simple science part..... you have to take a loook at the thermodynamic cycle of an engine,  basically the cooler the intake air the more efficient the expansion rate in the combustion cycle.

Cold air is denser than hot air, the molecules are closer together, and hot air the molecules are further apart or expanded.

hopefully you can see the point Im trying to make by now,

If not, well....  what air takes up more "space" air at 300 degrees or air that has gone thru an inter-cooler and is now 120 degrees. 

Thus making a turbo at idk 15psi, putting the same amount of air in as a roots style supercharger at 6psi, ( this is an example guys) I'm sure theres some formula out there.


Now with a roots blower there are things done that can help cool the exhaust air of the blower before it is combusted, perfect example is top fuel drags, they run on pure alcohol, which absorbs the heat of the incoming air and cools it down before combustion.    Another thing some people so is run meth injection/ alcohol injection, this not only raises the detonation point, helps in the cooling process of the air.

I gotta say I might be way off on all this, but it is really the only explanation I can come up with,   Simply it is a higher boost level from a turbo because its exhaust temps. are lower than a blower. thus it is still putting the same amount of air into the engine

this is why there is such a huge argument over which is more efficient, I am not going to get into that   as I am a blower guy




And yes I came up with all this on my own

[Jthomas]

Roots blowers can't be inter cooled. Unless you use a chiller. Chillers and intercoolers do the same thing. They cool the boost giving you a denser air intake charge wich creates more power

[Jthomas]

I know all the science behind all forced air induction. But back to top of page one. How the F can it happen?

[lilred]

Lower compression - > higher boost

[lilred]

Lil ricer motors have a short stroke and low compression. = high rpms and lots of boost

[Jthomas]

Turbos are more efficient yes. But you can't create as much power with one as roots. If not, then why do all the top fastest cars use them???

Blowers are way better. I don't care if it takes a few hp to spin one. But the outcome is better. An roots are all positive displacement. Everything that it sucks in, go out.

[J.C.]

I think they do create as much power, one is off idle(blower), one is after it spools(turbo). Maybe that is why it seems to be different, when really its the same, just at a different time

[xjs3667]

Yes Blowers can be inter-cooled.... When the funds are available to me I am going to be buying a inter-cooler for my blower!!  I know all the science behind forced induction also, It helps a lot to know about in every detail if you want a proper setup.

Please explain to me why you think an inter-cooler can not be used on a roots style blower??

And yes the lower the compression ratio the higher boost levels you can run but to a point.... My compression ratio stock is 8.5:1 and by running 6psi it brings it to 12.1:1  you never want to exceed 14.5:1   but I keep mine around 12:1 so I can stay on pump gas but ideally I should be running 100+ octane but she is fine on 98.....

I know all the science behind all forced air induction. But back to top of page one. How the F can it happen?

as I said before, the air out of a roots blower is hotter, therefore expanded already and has less room to expand more, air out of a turbo is cooler and less dense and has more room to expand when combustion occurs.

Also when it comes to force induction, remember you will always be limited by how much air you can force into the cylinder, be it from valves to restricted exhaust,  

I've never dealt with turbos and I am limited to the knowledge on if the boost gauge is pertinent to the system, but it is not for a roots blower If system is correctly set up.

boost gauge= useless piece of equipment just to look at ..... if your system is properly setup your gauge will read little to boost untill the higher rpms, and the air starts to build up in the manifold due to the limitations of your engine. your engine no matter what it is can only be efficient with X amount of air, once that limitation is reached there is no way to limit the blower to it since it is direct drive off the rotating assembly of the engine, and excess air is pumped into the manifold there fore giving an artificial boost reading.

Even though a roots style blower is not a compressor, its simply an air pump, there is no need for it be a compressor, as the air that exits the blower is hot and expanded (taking up more space) so kind of compressed in a way. there is no lag in a blower, there is constant output, this is why they have bypass valves, for closed throttle/idle, otherwise the engine will rev up at closed throttle since it is constantly trying to make the engine run at 100% efficiency, the more air you put in the more fuel used= faster rpm=turning the blower faster=runaway engine= not good!!  

Turbos by using exhaust gases are more efficient in this manner as it does not rob the engine of the same amount of power as a blower. There is Lag. It is designed to compress air and cool it down then into the engine, If a turbo were to try and compress hot air it wouldn't work, air can only be compressed so far when hot and when compressing cold air the compression process heats the air and it expands. So by using cold air the turbo can spool and compress the air, the air gets hot in the compression process and is then cooled back down and used by the engine, then it takes more time for the cooler air and more volume of air to equal the same amount of the hot air produced by the blower.

both turbos and blowers have there ups and downs, and efficient in one way but lack in another.


If you still don't follow me with the hot air cold air thing, I came up with a perfect example anyone can try at home while I was typing all this

Get a balloon and blow it up, Think of the balloon as your engine.... You obviously don't want to force too much air into it or it will pop and break. Like wise you don't want to put not enough air into the balloon that it is not holding the full volume of air that it can.(100% efficiency)

*Note* while blowing up the balloon, your kids or wife might think you are planning a party of some sort... notify them there is no such party in the making and it is a simple experiment and you might give them the balloon when done.

Ok take your now blown up balloon and place it in the fridge or freezer, go drink a beer or 2 to occupy your time come back and check on the balloon, notice how it is quite smaller than when you placed it in there?? this is because the air contracted and the molecules squeezed closer together. Now let the balloon warm back up and notice how it gets bigger. Warm the air i the balloon even warmer and it gets even bigger until you reach the limits of the balloon and pop... you just broke something.

*note* you can now give you popped balloon to your child or wife or whoever and tell them I told I would give ya the balloon when I was done.  

as you can see having the air hot before entering the cylinder means same amount of air as cold air to compress yet hotter air has more volume, therefore the cylinder doesn't need as much air to compress to achieve higher compression ratio!!

By using cold air the same amount is there just less volume, so it takes more air to achieve the higher compression ratio.  

I am more familiar with blowers as that is what I run, and don't know this information off hand for the turbos.

but There are mathematical equations to determine what boost you are running, what compression ratio you will achieve and what horsepower and torque ratings that will be achieved.   Also there are equations to know how much to overdrive or underdrive the blower, and what rpm the blower will be spinning at when the engine has reached max rpm.. you don't want to overspin your blower thats not good

If any one would like these equations let me know I'l post em here for ya. but they are only for roots style superchargers.

Finding the happy median where you will not damage your engine or your blower, yet have the blower be efficient in all rpm ranges is prudent to whether your engine will last or grenade, perform or fall flat on its face. Installing forced induction is a science and not just something that can be bolted on and go, sure it might work, but you will not be using all of the capabilities of the system that is right under your nose!! And who wouldn't wan't to get everything for there penny when it comes to HP

[Jthomas]

No I completly understand. But I think the "intercooler" you speak of, and a chiller are what we both are thinkin of. It sits on top of the manifold and under the blower and is water cooled. And as mentioned above that both turbos and roots will make the same power. Yes, true. But I want that off the line power. Instant boost. (roots)

And also I don't think you could get as much air in your engine as a 16-71 or 18-71, as you could with turbos,  per 1 revolution.

[Jthomas]

but There are mathematical equations to determine what boost you are running, what compression ratio you will achieve and what horsepower and torque ratings that will be achieved.   Also there are equations to know how much to overdrive or underdrive the blower, and what rpm the blower will be spinning at when the engine has reached max rpm.. you don't want to overspin your blower thats not good

If any one would like these equations let me know I'l post em here for ya. but they are only for roots style superchargers.

Finding the happy median where you will not damage your engine or your blower, yet have the blower be efficient in all rpm ranges is prudent to whether your engine will last or grenade, perform or fall flat on its face. Installing forced induction is a science and not just something that can be bolted on and go, sure it might work, but you will not be using all of the capabilities of the system that is right under your nose!! And who wouldn't wan't to get everything for there penny when it comes to HP

I also have the charts and books on all the math. I have a pretty Penney in just the engine part of my build. I have calculated every aspect of the engine, and have built it to proform for my application. I have a dead line by October for this truck to be driving. I'll post a build thread when it's done. I don't want to say anything to spoil the suprise.

[xjs3667]

cool Ill be waiting for pics!!!   can't wait to see it...

The inter-cooler I am talking about is one for a turbo, I am going to modify it to work for me   I know what your talking about.. the water cooled manifolds for the blowers that bolt to the manifold.

But for my instance I made my own blower kit for my jeep, there is only a couple of actual kits for the 4.0L but are like freakin 5-6k!!!   yea... not for me.... so I fabed up my own using a eaton m90 off of a jaguar, these blowers are "remote mount" not directly bolted to the manifold, instead they have piping going to the manifold. And I fabbed a bracket to mount the blower where the ac compressor was.... And I figure if I got piping going from the blower to the manifold, then Why not try and stick a inter-cooler between the 2?   I figure its worth a shot? I've never really heard it done before, but Ive never seen a blower mounted on a 4.0L like I did either and it works freakin great!!! 

Its all trial and error, if the inter-cooler idea don't work... ohh well, it runs like a raped ape now with out it anyways   if it does work, freakin sweet!!  one more one off custom thing done, And when I fab something up or come up with some thing new its always about functionality first then looks      


you are 100% right tho  for instance  my blower eaton m90 has a max rpm of around 18,000rpm a flow of 90 CID of air per revolution

where as a comparable turbo for the same engine sizes are, max rpm is around 150,000rpm!!! since turbos are different and dont make power untill spooled, normal operating range is around 100k-140k rpm.  with a flow rate of almost nothing per revolution, in fact they measure a turbos flow rate with lbs. per min.   and at 46k rpm the lbs. per minute is like 1.10lbs per min.. 

so now we all can see why there is the lag that there is. 

I personally prefer a blower and probably will never install a turbo on anything I own unless I hit the lotto big and just have money to throw around ..... but until then I will stick to my beautiful whine of a blower and the instant power, and knowing that it is there soon as I put my foot into it a little. and there is lees stuff to go wrong with a blower, they are very reliable.


Jthomas, I am glad that there is some one out there with the same amount of knowledge as me when it comes to the subject, If you are anything like me, once I start leaning about something like this I can't stop until i know it all, which will never happen since people are always coming up with something new everyday  

I know I went a little in detail a lot but not directed towards you or questioning your knowledge,    I figured there isn't much out there and felt like being talkative    so everyone else that doesn't know the subject can learn some. 


Good luck to ya can't wait to see her when shes done.... my next project in the near future is guna be throwing a 6-71 on a 454 maybe a 572 I'll be building for my dad for a suburban he's restoring

[lilred]

Cool it with propane

[lilred]

I figure the shorter stroke of the ricers enter into it because ya got less mass moving in shorter distance with just as strong of components.. Stays together a little better than a long stroke American truck/suv engine under boost.. personally I prefer superchargers for off the line/low end boost...

[ice87]

as you can see having the air hot before entering the cylinder means same amount of air as cold air to compress yet hotter air has more volume, therefore the cylinder doesn't need as much air to compress to achieve higher compression ratio!!

By using cold air the same amount is there just less volume, so it takes more air to achieve the higher compression ratio. 

ok but i will make more power with colder air. it is true will hotter air your compression would be higher than the same amount of cold air. but with cold air i can put more air into that cylinder and have the same volume but have more oxygen then you. more O2 means more fuel which = more hp
colder air is always better no matter what

[Jthomas]

I figure the shorter stroke of the ricers enter into it because ya got less mass moving in shorter distance with just as strong of components.. Stays together a little better than a long stroke American truck/suv engine under boost.. personally I prefer superchargers for off the line/low end boost...

If you changed the crank maybe. If he had shorter rods, it would have a faster stroke, but also built a lot on heat. I've always used the longest rods I could get away with.

But I was thinking about their low comp ratio and boost. Now I only have a roots chart to refer too, so I'm sure it's inaccurate when talking about turbos. But with 8.5:1 comp, on 5psi is something around 12:1-12.5:1? Off the top of my head? oh and assume this is all on pump gas.

So if these guys are running, say 15+ psi. Now there is now way they are keeping this on pump gas. But that's thinking in terms of a roots. But I'm still baffled.

Im going out on a limb here. They do run that much boost and Push huge hp out of these 4 cylinders....


BUT, the lifetime of these engines is less than a snowballs chance in hell???


Okay and one last thing. If they are running these crazy boost levels. Now even on the built up 4 bangers, how can they get the flow? Hp?

They have 1 head, 4 cylinders, we have double. How can they get the flow to Mach the cfm of the injecter and turbo ect? With one head. and simply, how can they create that much F ing power!?!? YouTube "Nissan from hell"
Go crazy with em.

[lilred]

Here's a good one.... Base is the 4afe (1.6l) same engine that was in my 93 geo prizm. 300hp @ 21psi
http://forum.9000rpm.co.za/viewtopic.php?id=6020
bore 81 mm,  stroke  77 mm

[ice87]

 

So if these guys are running, say 15+ psi. Now there is now way they are keeping this on pump gas.
[/quote]
they are running on pump gas because all the boost is going through an intercooler. This cooler air can be run on pump gas.

[xjs3667]

So if these guys are running, say 15+ psi. Now there is now way they are keeping this on pump gas.

they are running on pump gas because all the boost is going through an intercooler. This cooler air can be run on pump gas.
[/quote]

x2   it is the hot air that causes detonation early, we have to run higher octane or meth injection or straight meth, as I said before to absorb the heat of the hot air not only does it higher octane burn more efficient,produce more hp but it cools the engine, and allows us to advance timing to a ungodly level....

now with the 4 bangers pushing that much hp, they are heavily modified, might look stock on outside but internals is where its all at, THERE IS NO WAY IN HELL  a stock 4 banger can handle 1000hp!!!   

also they are from what I know dual overhead cams, not only does it put less drag on the engine,( the cams directly open and close valves, compared to say a sbc lifters, pushrods, rockers, then valves) but they have 4 valves per cylinder compared to our 2.

yeah yeah yeah they might make 1000hp   but you do know there are V8 making 2000+hp....  just remember hp cost $$$ and lots of it

[Jthomas]

I could just pour a couple gallons of meth in my tanks with pump gas?

And now that I go back and read. All of these big hp 4 cylinders are measured in RWHP!!

That's why they get big power readings, its not measured at the crank. Wimps.
You can build alot of hP and Tq just through your gearing and tranny. Non of the cars I've seen have been dynoed on an engine dyno. Just the tuner kind.