Here's what I have gathered in the two months or so that I have researched forced induction (more so turbocharging).

Sure you can stuff a lot of boost thru a motor, like a 300rwhp stock longblock, but like a GN motor, sooner or later the stock long block can't take the cylinder pressure and we lose head gaskets, lift heads, and split blocks (GN).

If we build up FI motors, we build motors that can make more power off motor, and need less boost for example to make 700rwhp. The issue is when are you making too much power from motor vs the power adder.

I subscribe to the idea of making the longblock completely geared for FI performance. That means not overcamming it and coming up with a combo that gets air in and OUT.

Now let's use a number like 700rwhp.

Now a stock longblock will fall apart well before hitting 700rwhp, I think we could expect maybe 500-550rwhp thru a stock longblock for an unspecified period of time (for the bigger rwhp numbers).

So, we end up build a 346-427ci longblock so we can make more power... like 700rwhp.

Now, here are some key questions I have... Assuming that all seekers of 700rwhp would use all the good parts, ie head studs, main studs, pistons, rods, well thought-out fuel system, how will the power characteristics change based on:

-levels of head porting if any and why
-size of valves and why
-amount of cam LSA

Will a guy with stock heads always be hamstrung compared to the guy with stage II 6.0 heads with 2.05/1.60 valves or can the guy with the stock heads just turn up the boost a bit? It seems to me that example number one will run into cylinder pressure issues first but that is really the only negative to doing that is that right?

2nd example, if a guy has ported heads, and a big cam (235/235), and guy #2 has a stock 02 zo6 cam (210/220), what will be the differences in the powerband, will guy number make peak at a much higher number? What if guy #'s cam is a 235/235//114 vs a 210/220/117, what do you happening then?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>


-level of porting if any and why
-size of valves and why

</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">for answers this question read my reply here:
http://web.camaross.com/forums/showt...threadid=28874


</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">-amount of cam LSA</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">combined with a certain amount of duration is going to dictate the amount of overlap your cam is going to have. The reason why many of the guys on the board with smaller duration cams are making more power than those with larger duration cams is because they have less overlap and aren't bleeding off as much cylinder pressure BUT at the same time they have more of a chance of lifting gaskets. Thats one reason why harlan's car still hasn't....he is bleeding off some pressure and just making up for it with more boost and better flowing heads

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Will a guy with stock heads always been hamstrung compared to the guy with stage II 6.0 heads with 2.05/1.60 valves or can the guy with the stock heads just turn up the boost a bit? </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Kinda relates to my respone on cz28. A guy with stock heads will get by, will just need more boost to it. With the LSX type motors and the problems associated with boost from the low amount of bolts holding the bolts on, i'd rather have a better flowing system to keep the boost lower and the power similar

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">It seems to me that example number one will run into cylinder pressure issues first but that is really the only negative to doing that is that right?</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">righty-o, because of the larger boost level. But just realize that this can all be dicated and designed to do it the way you want by using certain wheel/housing combos too. Run a large wheel and low boost to get XXXrwhp or you can run a smaller wheel and high boost to get XXXrwhp, there are pros/cons of each but you pick it for the whole COMBO to run as a whole. COMBO COMBO COMBO is what it takes to get any type (and especially turbo motors) boost motor to run a good number

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"><strong>2nd example, if a guy has ported heads, and a big cam (235/235), and guy #2 has a stock 02 zo6 cam (210/220), what will be the differences in the powerband, will guy number 1 make peak at a much higher number? What if guy #'s cam is a 235/235//114 vs a 210/220/117, what do you happening then? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yes, the first guy will make peak power at a higher rpm due to the added duration and it will have some overlap and bleed off some cylinder pressur and actually be down "some" power to the smaller cam that is in an exact combo. Also the second cam i think has negative overlap that turbos like but i'd rather build a motor for boost with good heads and bleed off some pressure via the overlap of the cam and just make up for it with a few more psi. Again, look at harlan...little bit of bleeding off pressure saves the gaskets and is just made up with a little bit more turn of the wastegate and you can still FLY <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

Just general speak, but for stock cubes, 600rwhp up to 10-12psi I'm not a fan of porting heads unless you are increasing the cc's to lower C/R.

But for your goal of 700rwhp stock cubes or larger I'd def go for the porting, 6.0 Heads.

 

Just so there is no confusion, bleeding off intake pressure is not the same as bleeding off cylinder pressure. And a lower flowing head with more boost pressure will not have more cylinder pressure if horsepower remains the same (not taking into consideration the heating of the intake charge)

Take for example (hypothetically)-

stock 346, 15lbs of boost, 530rwhp


stock 346, except stage 2 ported heads, 10lbs of boost, 530rwhp


The engine with ported heads is more efficient than the one without. You have less restriction to flow, you so have a lower actual intake pressure (boost #) at the same CFM into the cylinder. Combo #2 is better because you are making the power more efficiently, therefore heating up the intake charge less and having less possibility of detonation. (you also have more HP potential per certain fuel octane)

Another example (hypothetical).

Stock 346 with 210/220 cam and 12lbs of boost, 500rwhp.

Stock 346 with 235/235 cam and 12lbs of boost 500rwhp.


The ZO6 cam does have negative overlap, and IMO the type of cam that should be used in a FI application. We aren't going to blow any of the intake charge out of the exhaust, but some argue that a little overlap is good.

The 235 cam has alot of overlap, so alot of CFM is going out the exhaust during that time. This cam would make less power than the Zo6 cam (IMO) because in order to get the same boost pressure you would have to pulley up the blower, and even at the same boost level, you may not have as much cylinder filling due to the overlap.

Cylinder filling=cylinder pressure=horsepower.

You are talking about high cylinder pressure like it's the cause of lifting cylinder heads. The higher the cylinder pressure the more horsepower you will have as long as it's a controlled burn (no detonation).

The only time you will lift a head due to excessive cylinder pressure is because of detonation.


-level of porting if any and why

In my opinion, if max horsepower is of concern and not low engine RPM response, a large volume intake port with high flow is what you are after. Whereas velocity is a big concern in a naturally aspirated setup, I think overall maximum flow should be of primary importance on a FI setup.


-size of valves and why

I think anything over 2.08/ 1.65 is not necessary on an engine with around a 4.0 bore. I wouldn't skew the valve sizes to favor intake or exhaust flow either way.

-amount of cam LSA

I think that's not as relevant as how much overlap. A 235/235 with 116lsa will have alot of overlap, whereas a 214/222 with a 116lsa will not.

So, I guess you really can't just say that a certain LSA is what you want to go with. Duration, lift, ICL, LSA all have to be considered at the same time and not independent of each other.

 

Thanks for the responses.

Intmd8, what are the main differences then going to be for a motor with the following cams?

227/224/111
220/220/114
236/236/114
210/220/117

Now if cylinder pressure = horsepower, then I need to go with a big intake valve setup or big exhaust valve setup?

I am also coming from the land of 505 ft lbs of tq by 4200 rpms so I don't mind if I lose some lowend tq. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

I don't think the very few guys who have made big power with a ls1 are an end all of discussion on head lifting.
I don't care what anybody says. I believe a lot, if not all of the problems with heads lifting are from detonation.
Now consider the fact there are 4 cylinder 2.0 liters making 900-1000hp out there in the ricer world.
Not only do they have only 2 liters or so, but heads that flow less than a stock ls1 port in most cases.
Boost is king. Knowing how to control it and making smooth power is the issue.
You don't need more cubes and you don't need any heavy porting of the heads to make big power and you don't need to rev up the motor like N.A.
Put all your time and thought into the fuel system and tuning and crank up the boost/airflow to make the power.
Sure it gets tricky to do this.
That's the fun part.
Steve

 

I totally agree with Steve... Imports stuff 20-30 lbs of boost thru Nissan and Honda motorsa and run in the 8's with liteweight cars...

I'm leaning towards using some good ported heads that anyone can get, and some excellent head studs.

 

PSJ, FWIW I am getting a stage one kit H/C from ARE in a few weeks. I wasn't planning on it, but my buddy won the package and sold it to me for less than half price. We told them that is was for forced induction - I have a powerdyne right now but eventually want to get a turbo. Wade at ARE recommended a Comp Cam 224/224 .561/.580 with 114 LSA. He did say that this cam was OK for a supercharger but that it would shine with a turbo.

I'll get it tuned and dyno'd in March, and I'll let everyone know how much I gained - should be interesting.

-Geoff

p.s. Is somone planning a turbo buildup? Lots of questions about boost recently John...

 

Yes, I am building a turbo setup for 2003.

Does it make sense to go with smaller or biggerl valves for a turbo setup? I was told smaller to keep up velocity.

 

You can't really look at the lsa as a value in and of itself - it really only tells you something in the context of the cam as a whole (e.g. you need the rest of the specs).

As for head porting, I would get as much head porting as you can afford - now the porting itself may follow a different strategy than a NA setup, but it will still be beneficial. Worst case you make the same power at a lower intake pressure, so everything lasts longer. Realistically you will make more power at a lower pressure as you have reduced pumping losses, etc.

INTMD8 made an excellent point on pointing out the distinction between cylinder pressure and intake manifold pressure - cylinder pressure pretty much equals the torque value at that rpm, while manifold pressure is just a function of CFM and restriction.

Sure the stock headed guy can run more boost and make up for his poorer heads, but when he turns up boost until power levels are equal he will be at higher pressure (working compressor, valvesprings, etc. harder, as well as hotter intake charge, etc.).


When you go FI you are basically forcing a fixed amount of air through your engine (per unit time). This basically fixes your horsepower potential. How close you get to the theoretical max depends on how efficient your setup is. Basically the point of everything here is to minimize restriction. In an NA setup the engine "sucks" in as much air as it can, so your CFM is essentially a function of the engine itself. With a compressor in front the CFM is fixed - now your engine just determines what you do with that air.

For a turbo setup I would first determine your hp, etc. goals and spec out an appropriate compressor(s). Then I would go for the biggest motor you can get away with without sacrificing to much strength. Pay close attention to your piston height - most of the big 4xx motors are running pin heights smaller than I would want on a FI setup. The motor will basically spec itself out when you maximize it within those constraints.

I don't think you can really go to big on the valvesizes with a FI (barring anything stupid) but you will definitely hit a point of diminishing returns.

You are also going to want to consider detonation reduction considerations - such as ceramic coating, polishing, etc. If you prevent detonation you shouldn't have to worry about lifting heads, etc.

As for specing out the camshaft, I would call some place that has experience with turbo setups in particular - they have different requirements from na and supercharged applications.

Only other suggestions would be get a good intercooler, and a good boost controller if you want it to be a very streetable ride.


Chris

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong> Yes, I am building a turbo setup for 2003.

Does it make sense to go with smaller or biggerl valves for a turbo setup? I was told smaller to keep up velocity. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The intake valve size has very little to do with 'velocity' in comparison with the intake port size and shape. That being said, I would run valve sizes that correspond with your bore size.
(Meaning if you have a larger bore and you can unshroud a larger valve, do it).

The imports do make a ton of hp, but at 30lbs of boost, you are going to be running race gas all the time.

As Chris said, you should be looking at overall efficiency.

I think alot of people don't pay attention to detail with a forced induction engine because they figure if it doesn't make the power they can just turn up the boost.

 

i'd set the engine up to get it to run around town the way you want it to, with the driveability and response you are looking for, after you take care of the above mentioned essentials.

after that, just put the boost to it until you meet your goal or hit the detonation/head sealing barrier.

your post is exactly why i only did a street port on my heads.. there just really isn't a need.

hp=air in the cylinder not air pressure in the intake and if your goal is 700, and we know you can get it by big heads/low boost or high boost/small heads.. why not do it the cheap way? the intake temperature rise is taken care of with the appropriate intercooler.

thats what i think anyways.


ps is 505 by 4200 supposed to be a lot of low end torque? check the link <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
http://www.ls1motorsports.com/707Dyno.htm

 

So many options.. ChrisB are you saying to use a bigger engine and boost to accomplish a 700rwhp goal?

 

How much boost was ls1motorsports pushing to accomplish that 707rwhp/730rwtq #..?

 

check out the Feb 2003 issue of Turbo& hi-tech performance mag.
They have a very good article on a pro car.
It runs a 2.3 ford 4 banger.
Heads only flow 284/215 cfm.
Uses only 1.89" intake and 1.59" exhaust valves.
So that's less than most decent ls1 heads flow and they only have 4 cyls.
Copper head gaskets with o-rings.
29lbs of boost and 12-1 compression!
They use a T-76 turbo.
1000hp on alcohol.
Sure it's a wild setup.It has to be to make a 1000hp with little valves, hardly any cubes and mild heads.
But it shows how boost makes the power.
Tuning is everything. That is how you make such an engine survive.
A big cube ls1 with giant flowing heads will just be easier to tune to make similar power.
But the point is, you do not need the cubes and you do not need any trick super high flowing heads.
What you do need is serious skill with tuning,a turbo or blower big enough to flow the air you need, a good intercooling system to make sure the charge is not so hot it gets impossible to manage and a hell of a fuel system.

Steve

 

big bores, medium strokes = great turbo motors

the larger strokes and larger inch engines are just going to add to the un-controllable torque a turbo is gonna make anyway

Look at INTIMD8's 357" motor...and his is even a small bore

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by White_Hawk:
<strong>Wade at ARE recommended a Comp Cam 224/224 .561/.580 with 114 LSA. He did say that this cam was OK for a supercharger but that it would shine with a turbo.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">that sounds like the cam i have on my turbo set up.
IF i had it to do over again i might mo smaller on the exh dur. like a 224/222-114 to help make it a little more street friendly (even though its still not bad)

But if your not going to make a street car id go bigger like a 227/224-114 .600

 

Re: large bores - in an abstract sense you can get into problems running the bore size to big in a FI setup - a larger bore requires more timing simply because there is more area for the flame front to travel over - but that means more of your charge is burning before you do anything with it either - you still get more power, but effeciency is slightly reduced. In a NA setup this is more than offset by other gains - but becomes more noticeable on a FI setup where you don't have to "suck" in the air. With the larger flame travel area plus the much greater charge density, big bore FI motors tend to be more detonation prone than their smaller bore versions.

Now this is all relative, and I would still probably go with the biggest bore on a ls1 that I could get away with structurally.


Re: Larger stroker having to much torque - I disagree with this. The fact that the motor has more or less displacement isn't as relavent as it is NA. NA your longer stroke generates increased piston velocities, which gives you a bigger depression and thus more air, thus more power. The mechanical advantage isn't really that relavent vs. a big bore setup - sure, with a big bore you have less mechanical advantage with the stroke, but the piston area is greater & you have essentially the same combustion pressures, so the force transmitted is proportionally greater (force = pressure * area) - so you end up essentially the same setup with either setup.

Finally, the FI aspect renders that moot. Your low rpm power is going to be first and foremost a function of your compressor setup (how your supercharger is pullied, what turbos you have, where they spool up, and what your boost controller is set at).

Let's take a 348 and 422 with the same CFM profile vs. RPM - at 2500 rpm they will be flowing exactly the same CFM. The 348 will do so at a much higher manifold pressure, so pumping losses will be slightly increased. The 422 will make more power, but not tremendously so (especially if you have a good intercooler, etc.) The 422 will be easier on many of it's systems (valvesprings, injectors (not as much fuel pressure needed), compressor) and the intake charge temp will be comparatively cooler and denser.

It will make more power, but not by the same factor that a NA version of each would.

As an additionaly bonus since Turbo's are used here all you need is a good programmable boost controller and you can simply set your boost profile (pressure vs. rpm / mph, etc. depends on which controller you get) so it's not unmanageable on the street, and crank it up to whatever you need at the track so you get "full" power.


Chris

 

Thanks for the responses, but let's stay away from the "it depends on your combo" responses, if you want to say that, then please give an example of different combos that specifically illustrate your points.

I think when it come to engine configuration, there are limits. So for us Gen3 engine-based folks, a 4.000 stroke is the effective limit in stroke, if we want to keep running ~6.125 rod (vs 6" rod) and use 9:1 pistons.

Our limit with respect to bore right now is 4.100 for the big bore stuff. C5R motors can go bigger but the bare blocks are $6100.

What stroke do some of the turbo race car guys use, like Mike Moran or Lawrence Conley?

 

<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">The intake valve size has very little to do with 'velocity' in comparison with the intake port size and shape. That being said, I would run valve sizes that correspond with your bore size.
(Meaning if you have a larger bore and you can unshroud a larger valve, do it).</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Would you want to go to at least a 1.60 exhaust to increase your exhaust flow? It would seem to me that you don't need help on the intake nearly as much as exhaust. I'm getting 2.02/1.57 in my heads from ARE but I was thinking that I maybe should have bumped up to 1.60's before even installing them.

-Geoff