MelloYellow

I know that traditionally a Reverse Split is preferred for a Turbo, but would a 216/224 have any noticeable impact on a Turbo setup? It is a 114 LSA at least.

Black LS1 T/A

I'm no cam expert, but I don't see how anyone could argue against that cam profile for a non-custom cam setup.

A specific custom grind for your application is always best, but the cam profile you portray seems reasonable to me.

MelloYellow

Thanks. Ya, it's not too far off. It's already in installed the engine too. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

I know ideal turbo cams have more Intake Duration and mine has more Exhaust Duration. Not extremely off an ideal cam. Just wondering how having the durations turbo backwards might affect things..

The extra exhaust duration won't hurt me with a turbo?

<small>[ September 09, 2002, 06:51 PM: Message edited by: MelloYellow ]</small>

MelloYellow

I feel a little better after reading the Lingenfelter Cam is a split duration also.

LPE Turbo Cam 205/212 5xx/5xx 116

flynbludream

iTrader: (1)

Getting set for that Cerra kit eh Mello? <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> What kind of #'s are you putting out now? I still don't get why you would want more intake than exhaust for a turbo setup. Seems like an exhaust bias would help turbo spool up time. <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

neat

Turbo's create a tremendous amount of back pressure. As mush as 30 psi in some applications. With the exhaust valve open for so long, reversion occurs and you pollute the intake charge. A polluted inake charge ceates less power. A bigger intake duration gives the turbo more time to push air/fuel into the cylider. A smaller exhaust duration keeps reversion from occuring. The wide LS also helps create more power, but can sometimes build too much cylinder pressure in the mid RPM range, lifting heads or causing premature wear on the bottom end.

MelloYellow

I believe reversion is more of a problem at SUPER high boost like 12-20psi tho, no?

Also, why the LPE split duration to the exhaust side?

Ya, the Cerra Kit. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> But... Need to come up with the $$. I won't be one of the first ones. Looking like after the 1st of the year. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

Current numbers? Since I'm back to stock heads.. I'd guess 360rwhp, give or take.

<small>[ September 09, 2002, 06:50 PM: Message edited by: MelloYellow ]</small>

AlienDroid

On any boosted setup, overlap is bad, mmmmmkaaaaahhhhyyyyyy. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Keep the valve overlap down and the valves open as long as possible at the same time, works against each other. I'd extend the exhaust duration, rather then the intake duration, but I just came up with that from nowhere, except... This way we can get rid of most of the exhaust then snap open the intake valve and close the exhaust valve as soon as possible because the exhaust will try to re-enter the chamber and excape to the lower pressure head runners and intake. I think it would be best to just delay the intake valve from opening, so we get as much exhaust out as possible (which is hot gas and can cause your setup to be more prone to detonation).

Plus a nice snappy intake duration might help increase mixture turbulence <img border="0" alt="[devil]" title="" src="graemlins/gr_devil.gif" /> , which is good. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

MelloYellow

Learnin' here..
So you prefer a split over a reverse split due to reduced overlap?

I keep hearing about overlap when I ask people about Turbo Cams. Can someone clue me in and define overlap? How can you tell your overlap from general cam specs? Overlap relates to valve timing? How does overlap relate to duration and LSA?

AlienDroid

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong>Learnin' here..
So you prefer a split over a reverse split due to reduced overlap?

I keep hearing about overlap when I ask people about Turbo Cams. Can someone clue me in and define overlap? How can you tell your overlap from general cam specs? Overlap relates to valve timing? How does overlap relate to duration and LSA?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I'm not a pro at reading cam specs but I'm going to guess that the specs like 216/224 indicate a measure of the duration, maybe in degrees of cam rotation. but overlap is the range in degrees of cam rotation in which both the intake and exhaust valves are open at the same time. The exhaust duration is always in the process of closing while the intake valve is in the process of opening.

I think LPE is pretty smart setting up their cam that way. Evil in a turbo motor is detonation not intake duration limitations, I mean after all we force the air in. In a NA engine the air ready to enter the cylinder is under less pressure then outside air pressure already, so if you setup a pressure gauge at the intake mani you'd see nothing but vacumn at Wide Open Throttle. If you're getting say 14.7 psi(1 atmosphere or 1 bar) of boost, you more then double the air pressure at the intake, becuase no NA setup can get 1 BAR(ture pressure thus 1 bar of boost is 2 bar of true pressure) at the intake unless they combine no air filtration and some crazy ram-air.
So in conclusion forced induction can cram a lot more air through the intake valve in less time then the outside atmosphere can.

I think I'd shorten the exhaust duration a little bit and the intake durration a lot more and give it more lift to help out with air flow and port out the heads.

but you shouldn't completely remove overlap, there has to be a middle ground.

<small>[ September 09, 2002, 07:17 PM: Message edited by: AlienDroid ]</small>

AlienDroid

205/212 5xx/5xx 116 <- this is a very good turbo cam. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

this cam still has overlap but not enough to cause problems.

<small>[ September 09, 2002, 07:15 PM: Message edited by: AlienDroid ]</small>

AlienDroid

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong>Learnin' here..
So you prefer a split over a reverse split due to reduced overlap?

I keep hearing about overlap when I ask people about Turbo Cams. Can someone clue me in and define overlap? How can you tell your overlap from general cam specs? Overlap relates to valve timing? How does overlap relate to duration and LSA?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I think the reverse split is good for supercharged cars.
<img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

MelloYellow

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by AlienDroid:
<strong>205/212 5xx/5xx 116 <- this is a very good turbo cam. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> this cam still has overlap but not enough to cause problems.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thx!
LPE also likes a very conservate tune and idle. Which cam do you think would be better? This one or the one I mentioned? I know they are close. Hard to tell if LPE kept the cam mild for street manners or as the ideal turbo cam.

The '02 Z06 Cam might not be too bad for a $ sensitive Turbo/SC cam. Anyone remember the specs?

Or how about Harlan's Cam?

<small>[ September 09, 2002, 09:31 PM: Message edited by: MelloYellow ]</small>

AlienDroid

just got done spying on the turbo buick guys.

A guy with a 204-214 cam is getting very good mph compared to most but he wasn't on slicks so his time wasn't as good. Most of them recommend using lower duration cams like 206/206. Then there's a guy with a 214/210 getting good times but not so good mph. But times depend on torque converter and 60' times with these guys.

I'm going to guess the shorter duration cam is a little like a intercooler in that it's there to raise the boost threshold of detonation and in fact by itself actually lowers hp, however they alow you to run more boost safely on the same octane gas and in the end make more hp at the same level of tune.

JimmyKash

You also have to remember that those guys have cams for 231" vs 346" for you and 355" for me

I got tired of researhing cams and i couldn't find the cam i ideally wanted so i called up Mr. Turbo himself, Kenny Duttweiler, and told him my combination and he speced me out a cam.

I have a hydraulic flat tappet...

232/232 @ .050 .483/.483 (1.5) 114LSA

The lift is low because of the flat tappet design and for more driveability/idle which i wanted. When or if i go to a roller cam, i'll have another cam ground with more lift.

MelloYellow

Thx peeps!

Anyone want to comment on Harlan's 112 Cam? He seems happy with it so far.

JimmyKash

What r his specs?

i can tell you that he went with a 112 so that he doesn't build as much cylinder pressue which is a GOOD thing for the LS1 motors (i feel) if you are using a stock block and studs because the heads like to lift

Bleed off some of the pressure and you'll keep the heads on the car

zturbo

just for reference my old cam

220 229

.543 .510
114

neat

OK, hold on...

The amount of back pressure created by a turbo, is not directly related to the amount of boost. It is related to the A/R of the turbine housing. A smaller A/R will create HELLACIOUS back pressure, even at relatively low boost. I dunno the specs on the turbo in the turbotech kit, or the RR kit, but... I am under the impression that lag is almost non-exsistent with the turbo tech and/or RR kit. If lag isn't an issue, then the AR must be fairly small (someting in .6X-.7X range???), and force most of the exhaust gases through the turbine. This leads me to believe that severe back pressure is a distinct possibility with either kit.

Now, reversion is the enemy. The gases are hot, leading to an increased risk of detonation. It dilutes the AF misture, creating less power. To avoid this, the exhaust duration must be smaller or equal to the intake duration, even with a wide LS of 116. Even if the intake and exhaust valves were somehow never open at the same time, reversion would still occur the instant the piston was past TDC just after the exhaust stroke.

Because you can not have a super large exhaust duration, and still keep the exhaust valve closed after TDC, a smaller exhaust duration is necessary. However, because the exhaust duration is limited, the intake is not. The benefits of increasing the intake duration with out increasing the exhaust are, at best, debatable. this is why stock, sigle pattern cams perform well with turbo's.

So, IMO a wide LS is good. This prevents both valves from being open at the same time any longer than necessary. A kinda small exhaust duration is good, helping to keep cylinder temps down, and a pure AF charge. Intake valve duration is up in the air, I dunno...

As far as a blower cam goes, SC's like pretty much the same thing as a NA motor. Bigger exhaust than intake.

I dunno why Lingenfelter uses a split pattern for his turbo cars. I can not even pretend to know as much as that guy, but neither can most of you. His cars are totally custom, maybe the turbo's are set-up for a single pattern cam, who knows.

My .05. Thoughts, comments, crticisms??? <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

y2khawk

iTrader: (5)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JimmyKash:
<strong>What r his specs?

i can tell you that he went with a 112 so that he doesn't build as much cylinder pressue which is a GOOD thing for the LS1 motors (i feel) if you are using a stock block and studs because the heads like to lift

Bleed off some of the pressure and you'll keep the heads on the car</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">ding ding <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

228/224 .540 112lsa, it's a comp xr grind

my peaks have moved up a bit over the stock cam, as expected. There is a noticable change in the low end power with this cam, but i'm willing to bet the 8.7:1 CR has something to do with that. But once it's spooled it moves right along <img border="0" alt="[Firebird]" title="" src="graemlins/formula.gif" />

with the CR drop and overlap in this cam i'm running 6 to 7 degrees more advance at peak torque now, and pushing close to 13 psi on pump gas.

i'm currently limited by my valve springs and MAF. New top secret R&D MAF thingy got to the shop on tuesday, and i'm hunting springs now.

and BTW, reversion from ovelap actually cools the combustion event. You wouldn't think so, but it does. It's EGR, whether it's external with a valve, or internal w/ the cam it's the same thing. inert exhaust gas dilutes the mixture and cools the event. Not the best for power but...

I went longer intake vs exhaust to get more charge in and try to keep some energy in the exhaust pulse. Close angle for lower mid range pressures. seems to be working so far. Once i get the springs in there i can hopefully get a clean pull on 13+ to see what's up. Damn bouncing intake valves <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />