I know other local guys who have run the above turbo with more cubes and compression and they run really really well.
But the question is WHY? Runs really really well compared to what? A stock cam? A Z06 cam? A 224/224/112 cam? What pressure ratios? What size turbos? With some sound theory you get a whole lot less why's.
if you guys search here you can see as when they lowered the LSA the car picked up power everywhere, each time.
and if people can't understand why Shawn, Kurt, etc. don't want to share their cam specs...
Chad
Picked up power,hp or tq?What do those numbers equate to?How does that power work in a specfic combo?Can you spool the turbos where you want to?is it responsive or have a huge lag?These are all questions that should be asked.Like i said before any cam will make hp in a turbo motor-the right one will make the power you need where you need it without sacrificing much if any top end hp.We have found at the dragstrip the cam that makes the most horsepower doesnt mean it will make the lowest et.Cams with lower overlaps will make more low end tq which make for more boost at lower rpms and faster ets,cam timing also is very valuable,just cause you have the correct cam doesnt mean it will work great out of the box.We have advanced cams as much as 12 deg to make them work properly.
Sorry for not giving the exact info everybody wants,but i do believe i gave some good info.Now you do what you want with it.
__________________ www.virginiaspeed.comcustom engines for street or race,tuning,installs,fabrication. check our our online store-i'm adding new products every day http://shop.virginiaspeed.com/main.sc757-468-5101 1979 Z28 Outlaw 10.5-670bbc twin promod 94's Crew Chief,engine builder,tuner of Phil Thomas's
LSX powered Mustang"The Renegade" 7.29, 198mph-best 1/8 et.4.70 @ 164mph 315 radials at 3275lbs
Picked up power,hp or tq?What do those numbers equate to?How does that power work in a specfic combo?Can you spool the turbos where you want to?is it responsive or have a huge lag?These are all questions that should be asked.Like i said before any cam will make hp in a turbo motor-the right one will make the power you need where you need it without sacrificing much if any top end hp.We have found at the dragstrip the cam that makes the most horsepower doesnt mean it will make the lowest et.Cams with lower overlaps will make more low end tq which make for more boost at lower rpms and faster ets,cam timing also is very valuable,just cause you have the correct cam doesnt mean it will work great out of the box.We have advanced cams as much as 12 deg to make them work properly.
Sorry for not giving the exact info everybody wants,but i do believe i gave some good info.Now you do what you want with it.
Thanks for stepping up and laying that out Shawn. Someone needed to do it. I appreciate all your insight. In addition I can appreciate the cars with your engines laying down the numbers that prove you know what your doing.
Mark
__________________ 2009 combo Kurt Urban Performance 447 CU IN LSX-106 mm Turbo-Best 1/4 7.63@189.5mph----Best 1/8th 5.05@152 (3455lbs)
Picked up power,hp or tq?What do those numbers equate to?How does that power work in a specfic combo?Can you spool the turbos where you want to?is it responsive or have a huge lag?These are all questions that should be asked.Like i said before any cam will make hp in a turbo motor-the right one will make the power you need where you need it without sacrificing much if any top end hp.We have found at the dragstrip the cam that makes the most horsepower doesnt mean it will make the lowest et.Cams with lower overlaps will make more low end tq which make for more boost at lower rpms and faster ets,cam timing also is very valuable,just cause you have the correct cam doesnt mean it will work great out of the box.We have advanced cams as much as 12 deg to make them work properly.
Sorry for not giving the exact info everybody wants,but i do believe i gave some good info.Now you do what you want with it.
Picked up power,hp or tq?What do those numbers equate to?How does that power work in a specfic combo?Can you spool the turbos where you want to?is it responsive or have a huge lag?These are all questions that should be asked.Like i said before any cam will make hp in a turbo motor-the right one will make the power you need where you need it without sacrificing much if any top end hp.We have found at the dragstrip the cam that makes the most horsepower doesnt mean it will make the lowest et.Cams with lower overlaps will make more low end tq which make for more boost at lower rpms and faster ets,cam timing also is very valuable,just cause you have the correct cam doesnt mean it will work great out of the box.We have advanced cams as much as 12 deg to make them work properly.
Sorry for not giving the exact info everybody wants,but i do believe i gave some good info.Now you do what you want with it.
Ok... so based on your information above. Without telling us what cam's you build. Can you tell us what factors in a Cam effect each of those things you outlined?
Example (NOT FACT)
LSA effects top end HP...
Duration can effect...
Reverse split prevents reversion which builds TQ low..
I am a noob to this and Jermey (Zombie) has shed more light on Cam facts then I ever professed to know. There are those of you who fully understand these effects and I understand and appreciate that you are making a living on this business. So dont tell us your secrets (I fully understand)... but instead educate us some if you will!
__________________ PT88 Rear-Mount turbo... 800+RWHP Best time so far... 9.72@145.5MPH in the 1/4 Built and Tuned by LMR (THANKS GUYS!)
The truth of the matter is that there are about a million ways to skin the cat. I bet that if you ask 5 "cam experts" to pick you a cam you will get a full range of different looking cams for the same combo.
__________________ 98Z28CobraKiller 370ci LQ9 + AFR225's + PT88 9.57 @ 142 so far
I bet that if you ask 5 "cam experts" to pick you a cam you will get a full range of different looking cams for the same combo.
Due to a fundamental lack of sound theory. Some info has come out on things that can improve a setup, but with no theory to back them, just a result (which is what most people want, I want an explanation).
You can't generalize, and come up with one turbo cam that works for all.
I gave my example of running the 236/236 Speed Inc. grind. I know three other folks running it. They run 370 cid up to 408 cid engines. Two of the other cars are twins, and one is a big single. Of the four combos, mine was significantly more laggy due (a) running the least amount of cubes, (b) least amount of compression, and (c) a big turbo.
I could ask my friend who also had a butt turbo, who ran faster than you, what cam he had in his car when he was running that setup. Let me know if you'd like me to call him and ask.
But engine size/ compression, turbo(s) size, max rpms, and a lot of other things are going to influence cam selections.
I do recall that Mark K. (blwnta) was at one time running an old Mike Brown OH Boys cam grind last year or the year before. I'm guessing it was a reverse split, with less exhaust duration, and I'm guessing that Kurt Urban or W2W may have had some input into some of those cam designs. I would not be surprised if the intake duration was over 240, maybe even 244 or even 250. But they run big singles and have been running in the 7's for many years. I'm not sure how that info (if I am somewhat accurate) would help you with your rear-mounted pump gas setup.
Jim M. (Intmd8) has dynoed and messed with a lot of different cam grinds and his experience would be very relevant for you, as he's built and dynoed a lot of turbo setups that street driven. He suggested I run more compression, and he was totally right.
You can't generalize, and come up with one turbo cam that works for all.
I gave my example of running the 236/236 Speed Inc. grind. I know three other folks running it. They run 370 cid up to 408 cid engines. Two of the other cars are twins, and one is a big single. Of the four combos, mine was significantly more laggy due (a) running the least amount of cubes, (b) least amount of compression, and (c) a big turbo.
I could ask my friend who also had a butt turbo, who ran faster than you, what cam he had in his car when he was running that setup. Let me know if you'd like me to call him and ask.
But engine size/ compression, turbo(s) size, max rpms, and a lot of other things are going to influence cam selections.
I do recall that Mark K. (blwnta) was at one time running an old Mike Brown OH Boys cam grind last year or the year before. I'm guessing it was a reverse split, with less exhaust duration, and I'm guessing that Kurt Urban or W2W may have had some input into some of those cam designs. I would not be surprised if the intake duration was over 240, maybe even 244 or even 250. But they run big singles and have been running in the 7's for many years. I'm not sure how that info (if I am somewhat accurate) would help you with your rear-mounted pump gas setup.
Jim M. (Intmd8) has dynoed and messed with a lot of different cam grinds and his experience would be very relevant for you, as he's built and dynoed a lot of turbo setups that street driven. He suggested I run more compression, and he was totally right.
I agree with you on the compression... Josh (LMR) was pushing me to raise mine as it was very low with -32cc pistons and 72cc truck heads... but when we replaced the stock ported castings with Trickflow's with only 63cc chambers, car responded amazinly and dyno'd 88 more RWHP at 1.5lbs less boost. So that is yet another factor to performance in cam decision..
__________________ PT88 Rear-Mount turbo... 800+RWHP Best time so far... 9.72@145.5MPH in the 1/4 Built and Tuned by LMR (THANKS GUYS!)
There are so many theories out there....hell, half of the going-ons in a turbo motor is still sketchy. I've seen a certain type of cam work. It doesn't mean its the cam for everyone though. Why did it work in one guys car...I have no idea, but it ran REALLY well for its time. I tried it in my car and it didn't work worth a shit. I think I know why, but it could be other reasons too. I'd like to try some revisions of those cams that didn't work later on. For the moment, I'm using a cookie-cutter grind.
One problem is the dynamics inside of a turbo motor are very very complex
N/A cam theory is pretty well understood...much of which doesn't apply to a turbo car since its running into a substantial head pressure. As boost(power) goes up there's more available pressure residual in the cylinder which is fighting increasing exhaust backpressure. All this air also has mass so you have to consider inertia (air has to accelerate and will resist turning directions, etc)
I believe that the intake closing point dictates the off-boost/low boost characterisitics since this directly controls the dynamic compression ratio...probably why almost every turbo cam out there is advanced to some degree or run a "traditional" split like 112ish
Beyond that, I believe alot of cam profiles are out there as a result of trial-and-error
__________________ 1999 Pewter T/A | Just another slow drag radial car (see here) Virginia Speed 366ci LS2 + big turbo (the little block that could) | 7.99 @ 177.8 (1.36)
Virginia Speed 388ci LS2 + bigger turbo | In Progress
Special Thanks to TheOutlaw1, Phil99vette, Shawn @ Va Speed and MADMAN for all their help
One problem is the dynamics inside of a turbo motor are very very complex
N/A cam theory is pretty well understood...much of which doesn't apply to a turbo car since its running into a substantial head pressure. As boost(power) goes up there's more available pressure residual in the cylinder which is fighting increasing exhaust backpressure. All this air also has mass so you have to consider inertia (air has to accelerate and will resist turning directions, etc)
I believe that the intake closing point dictates the off-boost/low boost characterisitics since this directly controls the dynamic compression ratio...probably why almost every turbo cam out there is advanced to some degree or run a "traditional" split like 112ish
And from out of left field... A THEORY emerges! Thanks Fireball!
There's always some car out there somewhere that theories don't fit well with. What about them? Theory still valid?
depends...I just made a generalized statement...
__________________ 1999 Pewter T/A | Just another slow drag radial car (see here) Virginia Speed 366ci LS2 + big turbo (the little block that could) | 7.99 @ 177.8 (1.36)
Virginia Speed 388ci LS2 + bigger turbo | In Progress
Special Thanks to TheOutlaw1, Phil99vette, Shawn @ Va Speed and MADMAN for all their help
I don't think Zombie is as interested in what cams work well as he is why a cam is designed a certain way.
For instance, it's easy to say, "Joe Bob has a cam that's 240/230-114, +4 and his car runs 8's." Despite the fact that this is basically worthless information since there is no frame of reference, it also isn't helpful because there is no discussion about why particular specs work or don't work.
For instance, take one aspect of cam design, say EVO. An average high performance NA engine with a reasonable E/I head flow balance will work well with an EVO around 60 deg BBDC. Now, add 30-50 psi of exhaust pressure, a compression ratio of 8.5/1, and 2x the mass in the cylinder, and which way should the EVO move, how much, and why? Just an example...
__________________ 1995 Z28
388 LT4, AFR 210's, Home built T-76GTS turbo system
TH-350, Vigilante 10.5", Ford 9"
