They tune SD with factory PCM, its the cheapest method and works great.

 

I have and SD tune on a 2002 Z06 using the stock computer. I will be testing one on a highly modified car soon.

Speed density is your car's backup mode. Tuning it to work as primary is what an SD tune is all about. The low speed reversion and airflow issues with a MAF tune go away as all you car about is kpa.

The "Aussies" also have the 8 runner Throttle body setups they make. Harrop is now making a production piece.

With those they run symetrical pattern cams.

Here is the flow of a set of highly ported LS6 heads bare vs them with a FAST 90.

Intake AS LS6 225CC - No intake AS LS6 225CC - LSX Flow restriction
.050 - -
.100 69 -
.150 -
.200 155 154 0.64516129
.250 - -
.300 212 208 1.886792453
.350 - -
.400 259 251 3.088803089
.450 280 269 3.928571429
.500 301 280 6.976744186
.525 - -
.550 313 290 7.348242812
.575 - -
.600 323 299 7.430340557
.625
.650
.700


Same vs an Ls6 intake

Intake AS LS6 225CC - No intake AS LS6 225CC- LS6 Intake Flow restriction
.050 - -
.100 69 -
.150 -
.200 155 152 1.935483871
.250 - -
.300 212 204 3.773584906
.350 - -
.400 259 243 6.177606178
.450 280 260 7.142857143
.500 301 272 9.634551495
.525 - -
.550 313 281 10.22364217
.575 - -
.600 323 293 9.287925697
.625
.650
.700

 

I've had a couple of PM's on what site Darin's post is on.
www.speedtalk.com
The owner/webmaster is an ex-cup guy, Don Terrell, it is full of heavy hitter/innovators in the industry.

Chris

 

what head flow numbers? the 5.3 ones you posted up showing less than 75% exhaust to intake ratio. that when you also posted the theory that more than 75% flow you need to crutch the intake?


no problem. it'll be a couple months before the heads go on the wife's car.

well you keep saying the intake needs help. so start showing why. even with the VHP heads i'll be putting on, the heads percentages are under 75% for most of the time. so, if the exhaust side still isn't up to par (according to old theory), why crutch the intake side?

 

http://speedtalk.com/forum/viewtopic.php?t=321

 

so, looking at the above post from J-ROD, with the FAST intake, we achieve that. even with the LS6 intake, it keeps the 7% until .500 lift. overall the FAST only helps by 3%. and the motor is at .500 lift for a fraction of time. which again explains why the FAST intake is providing much gain on small motors that don't spin past 6000.

so, there blows the intake is such a restriction, that it needs a reverse split cam to crutch it theory.

 

here's the DD2003 numbers i said i would post. i used sequential fuel injection for intake.

 

What about the exhaust?

Also in your test, you just bumped the intake duration by 8* (@ .050) by doing the reverse of the initial design.

BTW, I got word there is a 6* exhaust crutch at .200

 

what about the exhaust? the post from J-ROD is flowing a head with a LS6 and FAST intake.

um yes i did bump the exhaust 8*. and i reduced the exhaust by the same amount. because it's the REVERSE of the original cam. hence the reverse split cam. what do you think a reverse split cam is now? last i remember it's the intake side having more duration than the exhaust.

so, the 047 goes from 8* split to 6* split. hence the accelerated lift technology. i know more about the VHP cams than i let you know.

 

yeah, i was referring to the results. 8 degrees added to the intake side bumped up the power curve as seen.


it doesn't only have to be duration. Take a look at some of Futrals grinds. Theres some thought put into them, seeing how the lifts are reverse of the standard duration split. I'd like to ask him for more details. Been curious, if he uses different lobe profiles on the ex. compared to the intake. anyone know?

sounds great. care to share in stupid man terms for me?

 

which is what we had discussed about in the comp 216/220 thread. about how cams moving power curves around. and why you would need gears, expensive intakes, having to turn the rpms higher to get to the power curve. and i said why do that, when you can use what you have to make the same power without sacrificing durability and driveability.


reversing the lifts doesn't do much for power. the VHP047 has the same lift anyway.

i'm only allowed to talk about so much openly. right now VHP and Crane are working on something that would blow your mind about cam theory. and that's all i can say.

 

you would use the same intake duration, and pull down the exhaust to match flow characteristics given that is the rpm range you want to work with.

 

ok i did that. wait until you see this one. now i went with a 210/206 only 4* smaller. rather than 8*.

hp


tq

 

i think VHP and Crane figured all this out already. but keep the ideas coming.

 

mrr23,
I for one look at the the total engine package. What I listed above is a good rule of thumb but rpm and displacement do play a part in determining the split also. Are reverse splits the only thing for an LS1, no, but in some cases they are an excellent choice. Building any engine, you have to have an open mind. . .thats the way I look at it anyway. . .to many times on these boards the attitude of "well it worked for him" is taken as gospel and the engines aren't close.

Chris

 

You can't live and die by DD. I use EAPro, and the numbers it generates are completely wrong for the dyno tested combos I have. I'm still working on figuring out where it is wrong.

GIGO. DD and other programs are nice, but they make certain assumptions in many cases that are wrong.

You can't say that an LS1 will always like a Reverse split. You can't say it will always like a standard split. What you can say is that if you gather the right data and apply some well tested design principles you will tend to come to certain conclusions.

 

 

 

Has anyone in here actually tested this theory and made great actual dyno numbers or track numbers, not computer simulated dynoes?

Has a VHP cam outperformed anything back to back

 

I’m trying to understand all of this. At least to the point where it can help me make my decision when choosing a cam to match my ported heads. Or at the very least, understand why my tuner or head porter recommends cam A or cam B. I’m sure a lot of people reading this are like me. I really don’t understand all the micro details but I’m smart enough to understand the basics. I’d like to know if I’m following you guys correctly.

So let’s look at my car for example. It’s a 2002 Z28 w/ stock intake manifold, Bauer ported TB, stock MAF, FLP headers and 3” true dual exhaust with x-pipe. It would seem to me, if anything, my exhaust is not the weak link, if anything it would be the intake. I want to stay with the stock bottom end. So let’s say I purchase a set of heads, say TEA stage 2.5. When you look at the intake and exhaust flow numbers, the exhaust flows about 80% to 90% of the intake at most measurements of lift. In such case, if I’m hearing ya’ll correctly, following CStraub’s 7% rule of thumb, I’d still be a little weak on the intake side. In which case a reverse split may help.

OR I could add a FAST 90mm intake and TB, equaling out the intake and exhaust. I say this because unless we purchase a sheet metal intake, the FAST 90mm is the highest flowing intake on the market. If anything, the exhaust would now be the weak link because larger headers are available on the market. In such case, assuming my exhaust is now the weak link, in theory these are my two options:
a) I could stick with my FLP’s and get a regular split cam, like a 232/236, .589/.589, 112.
Or
b) I could get some bigger headers and go with an equal split cam, like the TSP Torquer cam (233/233, .589/.589, 112).

Does the above make since? Am I following along or am I completely lost?

If so, then here is where I’m getting confused...I improved the intake manifold and throttle body flow but the heads still stay the same. Are you still suggesting that because the intake side of the heads flows more than 7% higher than the exhaust side that a reverse split, in theory, is still the way to go?