The LS1 based engine has a really good exhaust port as far as OEM stds go. For years if an OEM exhaust port was in the mid 60% range it was a good port. Now bolt on an intake to the head and the ratio may go to 67% on the exhaust compared to the intake...because of the restriction of the intake. You would still need to crutch the exhaust port with duration.

Now jump ahead to the LS1, you have an exhaust that flows 74% for agrument sake of the intake. You bolt the LS1 intake on and it reduces the intake by 7% say, now the ratio is 81% of exhaust to intake. This would have to be considered in my world as a canadate for a reverse pattern. Now throw desired powerband and CID into the equation and the camshaft can be calculated by some.

OEM's have crutched the exhaust for years, now we have an exhaust port that flows great air. What to do?

Chris

 

So around 80% is the number for you?

Also, in contrast to what you said, say you add a FAST 90mm intake and throttle body. You would need more duration on the exhaust side, correct?

 

My contact called me back about the intakes, yes they have a new 6.0liter intake manifold "project" in development with production scheduled in about 18 months. So I guess GM is going to address this. With what has been told to me about our project with GM, it only made sense an improved manifold would be need to reach goals of the project.

Chris

 

i don't live and die by DD2003. my problem here is sportside 5.3 is under the assumption that reverse split is the only way to go. he and i have been going at it in another thread in the truck section. comp216/220. he under the assumption the LS series of intakes are so restrictive that you have to have a reverse split cam. i pointed him to this thread. the only ones that have been able to succesfully use a reverse split cam is in high rpm race only type situations.

i have used DD2003 to show what happens when you use certain cams. i don't care what the numbers DD2003 produce. but it is pretty good in determining curves.

he comes in saying the LS intakes are so restrictive you need to crutch it with more intake than exhaust duration. then turns around and quotes a head flow theory of needing more than 75% exhaust to intake flow to want a reverse slpit cam. then he shows me a flow percentage of a 5.3 head showing less than 75%. using that theory say to use a cam with more exhaust to intake duration.

then J-ROD puts up a flow comparison of a LS6 head with both a FAST intake and a LS6 attached to it. with another theory of 7% loss for moderate engines. again proving the LS series of intakes just aren't that restrictive.

i'm just tired of submitting proof of my statements and the only thing he comes back with is the intakes are so restrictive. and doesn't even try to substantiate his claims otherwise. and when called to the carpet about it, he starts backpeddling.

 

ok let's use the flow percentages for the 5.3 head that sportside 5.3 posted up. then i'll add in the results J-ROD put in for the percentage change adding the LS6 and FAST intake.

lift-----5.3----LS6----FAST
.200---72%---73%---74%
.300---67%---69%---71%
.400---69%---72%---75%
.500---75%---83%---84%
.600---77%---84%---87%

the only time the flow percentage is above 75% is at the .500-.600 lift range. and how long is the engine at that lift? for a fraction of time. my point in the comp 216/200 thread was the guys in the truck section have a better manifold than i do in my 99 and 00 formulas. the truck intake flows better on most areas than the LS6 intake. until you reach upper rpms. why spend $800 for an intake that's only going to help in the upper rpms? truck don't need it. and why buy it, if it's only adding about 10-15 hp. why turn such high rpms? especially in a truck. if i can make the same power from 2000-6000 as motors with bigger intakes and TBs make in the 3000-7000 range, why bother turning the rpms? less stress on the motor and drivetrain. longer durability. and better driveability is maintained. i've always done it this way. and i've done equally as well or better than most with bigger stuff.

just like VHP, i concentrate on the torque aspect of the motor. torque produces quicker ET. horsepower produces more MPH. look at the VHP cams, they are making the same power and ET as others with bigger cams. hell, click the pink banner. go to timeslips. look at all the parts installed and then dyno and track tested. the airlid, filter, and MAF ends for instance. didn't do squat for ET. but they definately helped MPH.

 

Chris?

 

Pewter?
I am in and out today...

chris

 

I was wanting to know your thoughts on my last question. I'm just wanting to know if I am getting the jist of it.

 

Pewter your on the right track.

If the intake is the restriction, you add intake duration.

If the exhaust is the restriction, you add exhaust duration.

It all depends on the setup, but that is one option.

Holding the valves open longer to compensate for a lack of flow.

 

Okay,
if you added a fast intake to. . .for example 346CID and plan on a max of 6400 rpm and the exhaust to intake ratio was in the 73% range then a duration split of a couple degrees favoring the exhaust would be in order. Note I like to see flow numbers with the header primary size to be used bolted on the head and flowed. This will tell you how good the VJ is.

Chris

 

Yeap, that is one of the reasons my Stealth II (Cam only) 224/220, .581/.581 116+0 lsa (XE-R) has done very well in my A4, 404rwhp/383rwtrq, FULL bolt ons.

 

Predator.

Nice numbers. Do you have a dyno graph? How is the power under the curve with the wide lsa.?

 

mrr23:

You haven't been here long enough I guess, but the reverse cams were heavily researched and proven over 2 years ago. Check out this thread fro April of 2002.

https://ls1tech.com/forums/generation-iii-internal-engine/64678-tr-230-224-reverse-split-cam-dyno-results.html

Basically a case of "been there, done that".

 

hey sportside 5.3, someone found the thread for you. so, the dyno in that thread http://www.converter.cc/TR230-224dyno.jpg did exactly what my DD2003 model did when i reversed the VHP047 cam. loss of power below 5500 rpm. then picked up over 5500 vs a standard split. yep been there done that. sacrifice low end to gain top end. all it did was move the rpm band up and add a little more horsepower. then and only then after peak did it start to make alot more horsepower. and this is comparing a single pattern cam vs a reverse split. they upped the intake duration and lift, and raised the lift. did exactly what i've been trying to say. by adding more intake duration, you raise the rpm at which it starts to make more horsepower. and some guy here (sportside 5.3) laughed at me when i said that earlier in this post. now there's indisputable proof of it.

now if you are looking to make maximum horsepower, it looks like the way to go. but at what price? now you have to turn the motor to almost 7000 rpm to take advantage of the added power. i need more gearing. need a better intake. for an automatic, may or may not need a higher stall. for someone not wanting to do that, the reverse split just isn't the way to go. again i state, why turn more rpms for the added power?

cliff notes: a reverse split cam just doesn't make any more power than single pattern cam until really high rpms. unless you are willing to turn 7000 rpms, it's not worth it.

 

here's something more to chew on when considering intake restriction. the restrictions measured were based on a fully ported head that should out flow the intake. i wonder just how much of a restriction the intake is with a stock unported head?

 

mrr23<

You must not have read the thread or you are absolutely clueless...my 230/224 cam gave me the same bottom end power as my 224/224 cam, the same driveability as my 224/224 cam, but it made LOTS more power up top. Why? Because it was better matched to my combo. Great exhaust flow, so-so intake. That was the whole idea behind using it back in 2002. We didn't have LSX intakes and 90mm TBs back then.

Oh, and by the way...Horsepower wins races, not torque...any real racer knows that.

 

i would also want to see that. but with the entire length of the header tube. shorty, mid, and full length. with all the bends associated with the headers for a f-body, corvette or truck header.

 

Mrr23.

You just proved, box cam A which happened to be a reverse split isn't as good as box cam B. And automatically jump to the conclusion that reverse splits are designed for top end power?

One cam should meet the criteria for the setup. Throwing 2 box cams at it, and one works better means....
Outta compare more than .050 specs also.

 

i read and have a clue. no patrick it didn't. are the two lines on top of each other? was it enough to matter? no. again, it only helped the way upper rpms. was that what you needed? i'm guessing yes. but for a guy with a truck and a 5.3 towing a boat? no. now go put that cam in a guy's truck and see what happens. it'll make no difference what so ever to him. or might even take some low end away. patrick, in your application, you have a higher than stock stall, may have more gear (not in sig so guessing). a guy looking to improve the power without spending so much extra money to make it work (intakes, gears, TBs, etc) just doesn't need it.

no horsepower doesn't wins races. they both do. any REAL racer knows that. let me show you how that works as well. i put an electric cutout on my 00 formula. wow i should go quicker. better flowing exhaust right? dyno showed a 11/13 gain. now i go to the track. here's the results. and this was with 200 hp n2o. it cost me low end to gain mph. no ET change. horsepower creates MPH.

distance ------- closed ------ open
60ft ----------- 1.987 ------- 2.074
1/8 ------------ 7.902 ------- 7.912
mph ----------- 93.20 ------- 93.97
1/4 ------------ 12.102 ------ 12.080
mph ----------- 117.12 ------ 118.06

 

eh....