Need a book, just bought Maximum Boost

[weirdstyles.net]

I recently purchased MAximum Boost by Corky A Bell, but by the middle of Chapter One I was lost already. It took a master tech to explain some of that **** to me at work today. Could someone lead me to a good book on engine internals. Like I wanna know from Valve Train to the lowest lowly motherhumper on the engine.

Any good recommendations? I looked in the library, Amazon.com and bn.com but the only worhty ones seem to be like 140.00 and a little over my head...

edit:

Found this:

http://www.amazon.com/exec/obidos/tg/detail/-/007028637X/qid=1064793048/sr=1-1/ref=sr_1_1/102-0644373-2664156?v=glance&s=books

Any good reviews, from your (plural) standpoints? I can only trust the Amazon.com reviews so much...

[weirdstyles.net]

:repost:

Here, I scanned the son of a bitch...

http://home.comcast.net/~weird240styles/compression.jpg

[Bill Roberts]

C/R is a difficult curve to master. It not only depends on the CFM of the piping and the head flow but displacement is figured in. Their is no "real" formula for this. Say you are running the KADE and then you are turboing it at 10Lbs boost. Depending on the flow of the head and how it is ported, and depending on the amount of fuel you are injecting...plus the desired RPM which you want max. horsepower...then with all these variables, I would figure from some of my experience at 10PSI to run 8:1 for a 4 cyl. Now PSI is fickle. What if you have a head that can take advantage of 1100 CFM of intake...and this is at 7PSI. I would then want my C/R around 9:1.


Tempurature and injection angle to the CC is also important to getting a complete combustion at super high RPM of around 7K

the curve is very radically dependant on these varibles:

Max CFM of Head.

Total Combustion chamber CC

Heat of the plugs

Max CFM of the injectors.

Corrective porting of the intake.

Engine management.

Cam angle and duration.


The consensus is to run 12 % less compression per 8PSI from N/A for a sliding set of rules to work from in forced induction. When I say sliding curve, 16PSI does not equal 24%...rather, more like 16%.


You will be quite safe with an 8:1 C/R but rememeber, you want real power, you need slow burning fuel...like 90+ octane. With this, the 9:1 looks more promising.


Get the feel of what is going on??

It is a careful set of balances. We can talk more on this.

[Bill Roberts]

LOL we are on the same page here..


I was typing, you were scanning...cool

As the chart states, as you boost, compression ratio is lighter. no wonder, you have to start somewhere. When you are running 6K rpm, the head is wide open...meaning compression automatically is lower...and more boost, less C/R needed. But the occtane needs to be up there for high compression , high boost...got that?

[weirdstyles.net]

See Im getting old heads telling me 7.5; other wise the motor will go south. I mean, they are dealing with pushrod v8's and all so as me and andrave discussed there are differences which apply.

I plan to be on 92 Octane for daily driving with the boost way down. But race night, Ill pull out that ~$5.00/gallon 100 Octane shizzle, Its all up in the air, I dont even know about fuels and if I have to modify anything to run 100 or 120 Octane and so on. There is so much to learn, and I have to learn Automotive Electronics so I can reloacte all the switches (headlights, wipers, hazards, rear wiper...) to a central panel in the dash and reloacted ALL relays/fuses to two central panels in the glove comopartment for the project car. (Not my present daily driver, this will be done while the engine is out of the new car and being built) Its going to be hell....

There is so much here I need to learn, and I dont expect any one/ten people to sit down and explain it all. I also understand this is a LONG learning process, which I am very excited about. I need a book. About 50% of what you said went in-out and its so god damn frustrating.

Ok;

What is CFM, I know its a measurement, but of what. I heard it applied to air both here and else where (usually morons wanting to but a fan in their intake)

How does the fuel and air flow effect the CR?

1100CFM head? What?

See?! Theres soooo much...and stuff.

[Bill Roberts]

CFM cubic feet/min.

It is air mass loading into the engine.

Air and fuel is a mix. Once the air hits the mist of fuel, it is itomized into a fog.. The intake compresses the air and the head mixes the air to fuel ratio. A ported head allows the air to come in at a proper amount equal in each cylinder. The head meters (restricts) flow. The head also is the unit in charge of the proportanant mix....once the valves open and allow this mix to enter, the spark plug sets it off to either bomb the piston down or press the piston down with continual force. Higher octane is more push..(slower burning) and the valve times they are open...amount and how long, is controlled by the camshaft. Colder spark plugs equal more power.

Porting the head is the ultimate in controlling the air flow toward maximum push of the pistons. My port and polish job in my mafs, intake and the head yielded over 70 more HP from a KAE. The head is the key to power. Professional head folks and valve bowl grinding folks and porting/polishing, this is where the rubber burns up the road. In turboing, you are litterally cramming air under pressure down the throat of the intake ports and if the head is modded correctly, you can get enormous unimpeaded airflow into the head. As long as you have the gas flow mist to back it up....super power.

Do you realise their are SOHC KA24E's with over 300HP to the rear wheels being built with no turbo? 100 Shot of NOS, 400HP, turbo...close to 500. A damned KAE can do it. Less moving parts...but serious head work and intake porting, valve porting, lots of expensive mods and 112 octane, and 13 to one c/r

Well enough of the ramble.

Question (since I don't remember...what do you want to have the car to do when finished)? What HP? What quarter times? what RPM you want it to come together?

Those Questions are the most important to getting the package to do it's job.

I am quite happy keeping up with 330i's and being able to hit a solid 90MPH inside a block and 1/2.

So what you want to the car to do for you is much more inportant at this stage. You want to run 10's? 11's, 12's?? 13's??

Name your goals...and the goal will be reached.


If you simply want to have 400HP...this is doable. More than that...well dirty tricks.

[SimpleS14]

I bought this book also and I'm confused as fcuk on some of the content. However the goals (HP or PSI) being used in this book is not what I'm going for. At the most I will go 10 PSI (7 PSI daily)...so I will keep stock internals. However I'm still lost on fuel management....:confused: oh well....back to more reading and searching!

[Bill Roberts]

Ask, I will answer in as much laymans terms as I know. One thing for sure, if I have not dealt with it or experienced it, No BS here.

[weirdstyles.net]

Part 1
In reality, I want to be as fast as a dd can be. But in the REAL reality, I wanna hit mid to low 11's on a daily driver. But during the daily grind, I would like to turn to boost setting so the car would have roughly the same HP output of a stock DOHC, which I doubt is possible...

Part 2
Peak power? Is that aka Power Band?

Part 3
Is Inertial Force; Force against the cyl walls laterally?

Part 4
Confused about a part in this book, but I think it was explained.

Maximum Boost: Page 2, Paragraph 5, Line 2

In other words, when the piston is above the center stroke, it will always be accelerating downwards. When it is below the center stroke, even at bottom dead center, it will be accelerating upward.


How is this possible, if the piston is travling upward past the center line during the compression and exhaust strokes, and travleing downward past the center lineduring the intake and power stokes?

edit: becase i suck

[Bill Roberts]

The crankshaft does a variable acceleration of the piston.
Visualize this:


Piston is at top. Flows slowly away...increases its acceleration toward mid stroke...slows down at the bottom.......comes up and acceletates to the top...slows down and then proceeds to travel down acceleration.


Power band.

This is the rpm range in which the engine is in its maximazation of output. usually between 4400 and 6600. You have Horsepower band and torque band. T-band happens at lower RPMS...and HP band at higher RPM's.


Inertia force:

The force of the moving unit including flywheel and transmission and differential and rear tires and gearing and moving car body +direction of travel.


Inertia is what is left over force due to what is already turning. Force due to turning masses and control thereof.


That shed light?...I am with ya.....

What is part 4 you are confused of??

[weirdstyles.net]

Dont really understand this wording

The crankshaft does a variable acceleration of the piston.
Visualize this

Bands
So the TORQUE and HP bands are at two differnt "sections" of the RPM range? And tourque is generally lower than the HP right? So having torque at 3000 would be cool? No...maybe? Please...?


Inertial Force
How does that apply to the piston? Is this, in very basic terms, what is pushing the piston back up? Like if piston X is moving downward on its power stroke, its pushing the crank which will push piston X up for its compression or exhuast stroke?

Piston Movement (up/down)
Part 4, the quote, how is this possible? Like it HAS to travel upward PAST the centerline of the chamber to compress/exhuast.

[Bill Roberts]

Yes, low RPM torque and high rpm HP is preferred.

Two different curves indeed.

Other pistons push the pistons back up. When one is traveling down, another is on its way up. It is a balance of the operation. The more pistons, the more balance. A 6cyl RB is smoother than a 4cyl "anything" If you look at the whole stroke, pistons are moving in different directions based on the cranks journals putting them in different positions.


4. It is a continual process. It is fluid in nature. The engine is a simple pump. That is all it is. Nothing more, nothing less.


Each piston is 4 stroke. Fire, go down, come up, exhaust, go down, compress, intake, fire, go down. One stroke is one movement. Other pistons are working at different times to keep the cycle continuous.


Got that?


Now...I am surprised at this basics of understanding so far...get the base. You should have gotten that long ago actually. I did at 3 years old on my 2 horse go cart my dad built me. Mom hated me smelling like gas in 1962 going to the table to eat. I had to tie a rope to the engine and pull it then...then I tied it to the steering wheel.


I have been an engine hog for 42 years now.

[weirdstyles.net]

wish I had you experience. I have the basic movements of the engine, its just the terminology I think.

I fell I may have this tensile/compressive inertial load thing down. Tell me if this sounds about right.

My notes

Tensile Interial Loads are loads created by pulling the piston. Such as the upward storkes on the compression or exhaust stoke.

The lowest tensile inertial load is at center line, because at this point the piston is at is fastest pace in almost completely unrestricted.

The most stressfull tensile interial load on the piston/rod assembly is at TDC on the Exhuast stroke because there is no air/fuel mixture to "cusion" or oppose this force.

Tensile compressive loads are loads created by pushing the the piston. Such as the downward motion during the Power/Intake stroke.

The Power/Intake compressive strokes are evenly stressfull on the rod/piston assembly because they are not "cusioned"/


Sound about right?


edit-----------------------------------------------------------------

No god damn thats wrong. Ok, I think I got this. I have been over page 3 like five times, and I think i am getting this.

My New Notes

Tensile and Compressive forces are greatest, and most present, at TDC and BTC. But are present at all stages of movement, but the VERY least at 90* and 270* of the rotaion of the crank. (see below)

Why
Starting the exhuast stroke. The cyl is traveling upward to dispell the burnt mixture. As it reaches the TDC it is forced to travel the opposite direction by the cranks rotational motion. This creates a pulling, or tensile, stress, or load, on the piston and rod. This is the same for the compression stroke, however, the tensile interial load is less because the air/fuel mixutre is there slowing the piston travel. This reduces the velocity of the piston and the pulling, or tensile, stress, or load, on the piston and rod assembly. There for, this is related more over to the relationship of the crank and piston/rod assembly and how the rotational movement of the crank counter acting the natural movement of the piston, things in motion should remain in motion, can cause inertial load, tensile or compressive, on the piston and rod assembly. Compressive Inertial Load being the same effect, but is most stressful, or apparent, at BDC. And as the Sine Wave Graph on page three shows, the stresses are LEAST at 90* and 270* because they are at center line and have yet to be countered by the crank (or the air/fule mixture during the compression stroke). SO this motion is why people would say something along the lines of a piston/rod going throught the head. Because the TENSILE load is too much for the rod, the rod breaks and goes skyward eventually seaking and destorying one of our fine feathered friends.

By George I think he's got it!

[Bill Roberts]

Close!


You wrote...
The most stressfull tensile interial load on the piston/rod assembly is at TDC on the Exhuast stroke because there is no air/fuel mixture to "cusion" or oppose this force.


Well I would say this is where the point of maximum bearing load does occur on the crank bearings...but since the same shaft has other oppisite(sp it is late) forces, this is mostly minimized due to the interaction of the other pistons and quite frankly equalized to a factor of more than 80%. If you get technical, all of the pistons are sharing in this adventure so as to minimize the load bearing nature of said crank bearings. Like I say, it is fluid enertia working. Then you have oil slosh as another dampning component and the turning of the cams as one more. It is balanced within 4% in a normal engine. RB's are balanced within 1%...and KAE's with a single cam are around 1.5%...VS the 2 to 2.5% of a DOHC engine.



Less precise moving parts, the better. KAE at 9 grand sounds lovely.
It all is connected. Even the tranny plays a role as does the driveshaft and even TIRE BALANCE!!!!


Feeling it yet?


Better to whisper than shout.....I got ways to make you tell me all about it!


Flow with da zen.

[weirdstyles.net]

Originally posted by Bill Roberts


I edited that post in a MAJOR way, check it and reply.... i think I seriously got it.


If you tell me I'm wrong, I am going to cry and beleive that I am right just because if I dont, I will NEVER finish reading that book. EVER!

[weirdstyles.net]

Originally posted by Bill Roberts
My above post is correct. The other pistons counteraction disposes the forces that would be present if it were a single cylinder. Based on the clockwork of the engine, no problems due to counteraction. If counteraction were not present, the crank wear would be much more advanced due to this. Single cyl engines are designed around this...and the finest engines are designed around the abuse of single cyl operation as well. This is how we get hundreds of thousands of miles out of our cars in even abuse situations./

So all of this is sort of supposing there is no counteracions by the other 3 cyl. reacting on the crank. Hmmm, that does make sense. Kinda of like they will help each other out. Because if there were no other pistons, then the movement would rely soley on the Power Stroke, and I suppose gravity to a MUCH smaller effect. Wow Bill, it took dedication on both our parts to get this. I had to read and reread this son of a bitch to figure it out, and you kept poking me with a stick. You are by far the MOST helpful member on this board. [shout] Would someone get this man a mother f*cking Trophy?[/shouting] I hit page 27 tonight, and its all cause of the Bill man. Much appreciated good buddy, I will return with questions as they arrive.


Originally posted by Bill Roberts
Bed time, pick this up in the AM.

Damn straight, 1:34AM feels later than normal. Im hitting the sack...

[Bill Roberts]

Still up damnit..


But...remember this...




WS, lets make this a mission for you to post things in that book you do not understand and let folks chime in! Not only will the book get proper usage, but all that gives a care will learn in the process....so go ahead...where did you get lost..???????????~~~~~~~


I do mean what I say...and lets rock this thing!


PS, PM me, I got some news...
You may want to know about it.

Their are 17 folks on this board that I grow aqualnted with on a level of good vibes.

This is some special sh it

[sykikchimp]

Originally posted by Bill Roberts
CFM cubic feet/min.

It is air mass loading into the engine.

Air and fuel is a mix. Once the air hits the mist of fuel, it is itomized into a fog.. The intake compresses the air and the head mixes the air to fuel ratio.

Intake does not compress air. The combustion chamber is where the air/fuel mix is compressed. Again, the area under the head in the combustion chamber does most the mixing. specifically, as the piston is rising in the cylinder, it will smash the air/fuel mixture into the quench pads, and the air/and fuel get "swirled" into the center of the combustion chamber. This is where most the mixing occurs. The mixture is still actually mixing as the spark plug is fired. The fact that the mixture is swirling around is what allows it to aid in the burning process, so everything gets burned evenly, and completely, and you get maximum power.

A ported head allows the air to come in at a proper amount equal in each cylinder. The head meters (restricts) flow.
A non-ported head does the same thing. A ported head will remove restrictions and turbulence that are caused by the intake port being smaller than the runner's port. Basically you remove a small edge that protrudes into the intake flow. Less turbulence equals more air flow (cfm).

The head also is the unit in charge of the proportanant mix..... as I said, the mojority of the mixing occurs IN the CC. The fuel is initially introduced into the incomming air in the intake runners. Air and fuel are not even introduced to each other until the valve is open. if you advance or retard intake cam timing, then the valve MAY open slightly before, or after the fuel is sprayed into the intake runner. If you sprayed the fuel to early, the heat from the backside of the Valve could detonate the fuel in the intake runner. obviously, a bad situation.

once the valves open and allow this mix to enter, the spark plug sets it off to either bomb the piston down or press the piston down with continual force. Higher octane is more push..(slower burning) Higher octane burns slower. yes. But it doesn't have more "push". Using a fuel that burns slower allows you to keep the a/f mixture from burning too fast, and causing the explosion to "detonate" on top of a rising piston. Higher octane fuel is used to prevent detonation.

and the valve times they are open...amount and how long, is controlled by the camshaft. Colder spark plugs equal more power. Colder spark plugs don't equal more power. Again, they equal detonation resistance, because they will allow for a slower a/f mixture burn.

Porting the head is the ultimate in controlling the air flow toward maximum push of the pistons. My port and polish job in my mafs, intake and the head yielded over 70 more HP from a KAE. first, you don't port MAF's. "Porting" by definition is matching the size of the intake/exhaust ports on the head to the same size as the manifold ports. It has nothing to do with your MAF. I suppose one 'could' hone an MAF out, but you would need either proportionately larger injectors, or additional fuel management. Second, you did NOT get 70 hp with a port/polish job. you are hallucinating. ****, you still have the stock air intake system on your car. Either post a real dyno, or stop BS'ing.

The head is the key to power.
should say "Real Ultimate Power" lol.. anyways.
on an N/A car, sure. Not on a turbo car, you can over come head defeciencies (to an extent) with more boost..

Professional head folks and valve bowl grinding folks and porting/polishing, this is where the rubber burns up the road. In turboing, you are litterally cramming air under pressure down the throat of the intake ports and if the head is modded correctly, you can get enormous unimpeaded airflow into the head. As long as you have the gas flow mist to back it up....super power.
I will agree that there are gains to be had in F/I with a port, and polish. But they are not necessary on even a 350hp turbo KA, or even 400-450hp SR's. Sure if he wanted to build a 500-600hp drag monster, then yeah, he would need to do extensive head work. But this is still not where the majority of his power would come from.

Do you realise their are SOHC KA24E's with over 300HP to the rear wheels being built with no turbo.. 100 Shot of NOS, 400HP, turbo...close to 500. A damned KAE can do it. Less moving parts...but serious head work and intake porting, valve porting, lots of expensive mods and 112 octane, and 13 to one c/r? I haven't heard of anyone doing 300hp N/A KAE's since the early 90's with the IMSA cars.. and they certainly didn't run NOS or Turbo's as thier 13-14:1 compression ratio would not have even come close to handling either. Their highly overlapped cams would have also created serious amounts of blow-by with a turbo. Please, again, stop lieing.

Well enough of the ramble.
finally...

[sykikchimp]

Originally posted by Weird Styles
Dont really understand this wording

Bands
So the TORQUE and HP bands are at two differnt "sections" of the RPM range? And tourque is generally lower than the HP right? So having torque at 3000 would be cool? No...maybe? Please...?

Horsepower is a function. it is torque x rpm /5252. Corky explains this later I believe. My copy is on loan. Torque always peaks before horse power b/c Horsepower and torque curves MUST cross at 5252 rpm due to the above function.


Inertial Force
How does that apply to the piston? Is this, in very basic terms, what is pushing the piston back up? Like if piston X is moving downward on its power stroke, its pushing the crank which will push piston X up for its compression or exhuast stroke? "inertial force" as Corky is speaking is the load placed on the rod from the changing of direction of motion of the piston/rod combo.


Piston Movement (up/down)
Part 4, the quote, how is this possible? Like it HAS to travel upward PAST the centerline of the chamber to compress/exhuast. Imagine this from the CRANKS point of view. If you are looking at the crank from the front, and the crank rotates clockwise, then all motion of the crank from right centerline on the crank is devoted to upward acceleration, and all motion from the left centerline is devoted to downward motion.

[sykikchimp]

since you made corrections, I'll start here (see my notes in bold):

My New Notes

Tensile and Compressive forces are greatest, and most present, at TDC and BTC. But are present at all stages of movement, but the VERY least at 90* and 270* of the rotaion of the crank. (see below)

Why
Starting the exhuast stroke. which starts on the crank at 90*. (see previous post) The cyl is traveling upward to dispell the burnt mixture. As it reaches the TDC it is forced to travel the opposite direction by the cranks rotational motion. This creates a pulling, or tensile, stress, or load, on the piston and rod. Correct This is the same for the compression stroke, however, the tensile interial load is less because the air/fuel mixutre is there slowing the piston travel. correct, acting as a cushion This reduces the velocity of the piston and the pulling, or tensile, stress, or load, on the piston and rod assembly. There for, this is related more over to the relationship of the crank and piston/rod assembly and how the rotational movement of the crank counter acting the natural movement of the piston, things in motion should remain in motion, can cause inertial load, tensile or compressive, on the piston and rod assembly. Compressive Inertial Load being the same effect, but is most stressful, or apparent, at BDC. And as the Sine Wave Graph on page three shows, the stresses are LEAST at 90* and 270* because they are at center line and have yet to be countered by the crank (or the air/fule mixture during the compression stroke). The air/fuel mixture only acts as a cushion. The crank is still the counteracting force that changes the inertial loads from tensile, to compressive. SO this motion is why people would say something along the lines of a piston/rod going throught the head. Because the TENSILE load is too much for the rod, the rod breaks and goes skyward eventually seaking and destorying one of our fine feathered friends. you got it!!

[sykikchimp]

Originally posted by Bill Roberts
Close!


You wrote...



Well I would say this is where the point of maximum bearing load does occur on the crank bearings...but since the same shaft has other oppisite(sp it is late) forces, this is mostly minimized due to the interaction of the other pistons and quite frankly equalized to a factor of more than 80%. If you get technical, all of the pistons are sharing in this adventure so as to minimize the load bearing nature of said crank bearings. Like I say, it is fluid enertia working. Then you have oil slosh as another dampning component and the turning of the cams as one more. It is balanced within 4% in a normal engine. RB's are balanced within 1%...and KAE's with a single cam are around 1.5%...VS the 2 to 2.5% of a DOHC engine.



Less precise moving parts, the better. KAE at 9 grand sounds lovely.
It all is connected. Even the tranny plays a role as does the driveshaft and even TIRE BALANCE!!!!


Feeling it yet?


Better to whisper than shout.....I got ways to make you tell me all about it!


Flow with da zen.

where the hell do you get these percentages?? If your going to guess, say your guessing.

Lets talk about inertial loads again. In an inline 6 (rb) you have 3 firings per revolution. This means 2 pistons are achieving Max inertial load at TDC, while four are rapidly aproaching max at BTC. Since the load increases on an arc in both downward, and upward strokes, the 4 other pistons balance out the inertial load from the 2 firing pistons. Hence smoother operation. V-6's, v-8, and inline 4, all have additional problems with this. Inline 6's still get their fair share of Torsional (twisting) forces.

The transmission, and driveshaft have nothing to do with what we are talking about. They play a role in Torsional vibrations. These are Translational vibrations.

[sykikchimp]

Originally posted by Weird Styles
So all of this is sort of supposing there is no counteracions by the other 3 cyl. reacting on the crank. Hmmm, that does make sense. Kinda of like they will help each other out. Because if there were no other pistons, then the movement would rely soley on the Power Stroke, and I suppose gravity to a MUCH smaller effect.

No.. The inertial loads are still very present. The translational vibrations are what the other inertial loads help dampen.

You MUST increase rod/piston/crank strength as you increase loads on the engine.

Also remember that in a 4-cyl engine, you have at any given time 2 cyl firing. it's never 3 cyl counter acting. just 2 for 2. :)

3 for 1 would cause some crazy things to occur.

...phew! that was a lot of work to correct all that mis-information.

also, Weird Styles, check out http://auto.howstuffworks.com/

[fiebru1119]

I read Maximum Boost a couple of months ago and was confused about this one part regarding intercoolers. Apparently he claims that the long large endtank "vertical" fin intercoolers produce less pressure drop and are more efficient than the traditional small endtank "horizontal" fin intercoolers. If its true, why does everyone still run the horizontal style? The only time I've ever seen the vertical style is on the 787B. Is it a fitment issue? What do you guys think about that?

Heres a ghetto diagram of what I'm talking about:
http://www.imagestation.com/picture/sraid81/p5683b3c2416053fc9e2de11695a0bc1e/faf53aa4.jpg

...and BTW this thread better make the FAQ!

[weirdstyles.net]

:bowdown: chimp:bowdown:

Damn son... thanks fer setting me straight. But I dont think you should be so hurtful toward Bill. He's a great guy.

edit: Chimeth one, did you know theres and edit button? :D j/k

[sykikchimp]

Originally posted by fiebru1119
I read Maximum Boost a couple of months ago and was confused about this one part regarding intercoolers. Apparently he claims that the long large endtank "vertical" fin intercoolers produce less pressure drop and are more efficient than the traditional small endtank "horizontal" fin intercoolers. If its true, why does everyone still run the horizontal style? The only time I've ever seen the vertical style is on the 787B. Is it a fitment issue? What do you guys think about that?

Heres a ghetto diagram of what I'm talking about:
http://www.imagestation.com/picture/sraid81/p5683b3c2416053fc9e2de11695a0bc1e/faf53aa4.jpg

...and BTW this thread better make the FAQ!

I believe that it tends to be a fitment issue. Having one tank on top means you have to run intercooler piping to it. I'm not sure you could fit piping up near the top due to the bumper support. I haven't looked in a long time, so I could be wrong here.

There's also a questions of getting enough surface area. It may be worth it to go to a bigger intercooler with a bit of pressure drop to maintain the cooler temps that having more surface area would provide. these are guesses though, with no facts to back them up..

edit - also, about your original question about how compression relates to the amount of psi you can run..

The reason teh V8 guys can run 7.5:1 is because they have 8-cyl. That low of a CR on a 4-cyl would create really ****ty off boost response, and would cause the turbo to lag horribly. Corky does talk about this. I wish I had my book so I could reference you a chapter and page.

[deviousKA]

It is difficult to have such an in depth and technical discussion without difference in opinion, or should i say difference in factual information.