_zebra

... because 90% of the people on this forum are completely against any ideas like this, but my flame suit's on & ready for action!

and before you even start, yes i searched to find only a couple of discussions (here or elsewhere), and even then, they're outside the stupid 45 day window mandating yet another thread on the same topic.



on to the meat & taters of the subject...

TWIN CHARGING / COMPOUND BOOST (whichever you prefer to call it)

it seems to be a sensitive subject among forced induction crowds. i understand some of the pros & cons of it and am wondering if anybody has actually tried it on a LS engine Corvette. i've seen UPP's VR-4, Hellion's production kits for GT500s, a drift Nissan Silvia, MTI's new Camaro, Cummins trucks, Hennessee's Ford GT packages, a home-built Silverado, and even a BBC Gen1 Camaro. every one of them have had widely varying results (most being positive but a few pretty bad).

i know these setups ain't gonna extract the last ounce of power from a build - but that ain't what they're designed to do. it's all about making a metric crap-ton of torque consistently across the entire RPM range of the engine without working either booster very hard.

expense & complication aside (which can be mitigated a few different ways in both categories), how feasible would this seem to be on my (or any other adventurous soul's) C5?

what i'm thinking would be a forged engine with say a TVS2300 and STS twin kit. the TVS kits have proven to be quite reliable & great performers considering their constrained design parameters, and the STS, although not the best Corvette turbo solution out there, has done decently for itself as well as it'd help distribute the added weight across the length of the vehicle instead of adding it all at the front. it also has the dual A/A intercooler option behind the bumper which shouldn't interfere with the A/W heat exchanger of the 2300.

as for the design concept, the Maggie would be to deliver off-idle grunt & get the turbos spinning a little quicker than a standard engine would, and then the snails would start picking up the mid-range then make up for the PD's deficiencies on the top end... theoretically.

i understand that the TVS has proven to actually sometimes be a top-end restriction by as much as 10% compared to turbos alone, but one thing that would help work around that would be to find a way to increase the size of the bypass valve inside the manifold and have that re-open once the turbos start outflowing the Maggie so that air mostly flows past the lobes allowing the blower to freewheel (with the understanding that it won't 100% work that way without a bypass roughly the size of the throttle body - which there ain't room for). match that with a SD tune, 102 TB, ported lower manifold, a phenolic spacer (to reduce heat soak & IATs), an upgraded radiator, the appropriate fuel upgrades, and a drivetrain built to last, and i think this would really tear some people up!

picture this:
a forged 390 pullied for about 6psi with the turbo wastegates set for 10. that'd roughly create about 20psi max to work with and wouldn't be driving either charging system that hard at all. add a splash of meth to that combo & i'm thinking you're in for the ride of your life without waiting on your engine bay to explode.

maybe i'm off my rocker here , but i think it could work with the right engineering applied to it.






alright... let me hear it

breecher_7

I was gonna do it with a cts-v, it makes sense for a heavier car. For a vette it's kind of pointless in my opinion.

optimum01

_zebra

helped a Camaro set a new speed record of 205 (202.x was in a standing mile). they're roughly only 700lb more

breecher_7

Only????

As I mentioned, it makes sense for a heavy pig such as a camaro. The camaro is a portly bitch.

FunCool

Just spay it!!! Thats what I did!!!! You cant use anything more then 600 to 700rwt daily any ways. Hit the spray when you need 1000rwt to win a race. Lots of guys are doing it.

danieloneil01

Sounds like you have to much money.

_zebra

if only i had that problem...
my car sure wouldn't've basically just sat all year without getting nothing done to it while my wife sucked me dry

_zebra

so to speak

realcanuk

I agree these dual setups probably make more sense in heavier vehicules. My shop is currently experimenting on a Dodge Ram pickup with this gear driven dual procharger setup...



And just to make sure it's the fastest truck around a little dual stage direct port juice on top....



The results should be interesting, and the tuning a nightmare.

_zebra

hmm... so the belt drives one gear which in turn, spins both centris? and i'm guessing they're drawing from separate air sources then pumping into a common intercooler before heading to the intake?

interesting. definitely seems a little easier to build than some of the twin PD setups i've seen

breecher_7

Tuning it really isn't any different then any other blower and nitrous setup. Thanks for posting that, it's cool looking.

realcanuk

No belt on this. Its gear drive directly off the crank. I havent seen the intercooler setup yet so not sure on that part.

bradenW

The blower will become a restriction at a point, but if you aren't trying to push past that and have the cash to do it I vote YAY! Search Mullet Ford GT on youtube.

Juhatee

I don't comment to any other aspects but the Maggie bypass won't need to be opened if you're compressing already compressed air. PD blower won't be the restriction point when the inlet air is already pressurized. It makes the same amount of work, same heat transfers to air and it only takes the same amount of hp from the belt. Only the outcome is same amount higher that was fed into the blower. This is the way boost is built in very high boost applications.

You could plan that PD makes steady 10 psi pressure and you can choose not-so-early spinning centri to help with top end by 5-10 psi more.

0CK@UPPCOS

^'s right. The PD will never become a restriction, it simply multiplies whatever it's fed. Alot of people have a hard time grasping this, but it's the same as a PD works at altitude the same as at sea level, just better at SL because the air is denser to start with. You'll have the same result, the turbos will make dense air, the PD will make it even denser.

You've seen our Triple Charged VR4, so hopefully you've taken the time to watch the whole video on the results.



Because my next question to you would be WHY do you want to do this?

It's "cool", it's loud, and it get's attention! If that's what you're going for, by all means. But if you're wanting to make power.....that's a different story.

The SD uses power to spin it period! Unless you clutch it, with bypass valves and the whole 9 yards, which are nothing short of impossible to tune correctly. So you compound it (like we did). Then you can't stop spinning it. And spinning it takes power. In our case it was to the tune of 100hp. (721whp on TT, 620whp on TT + SC). The cross over point was ALWAYs 4K RPM's. So no matter what boost we compared 10, 15, 28, it was always a cross over at 4000.

We could spool 30psi by 1500RPMs, but 30PSI at 1500 really isn't as cool as it seems. Nothing like OMG the wheels are being blown off! At 1500 we were so far away from peak tq on the cam that 30psi didn't make all that big of a difference. And with the power we lost up top....not too much worth it.

If you want boost down low, Anti-lag. I can have 30 psi on tap waiting to go, while still sitting stopped at a light. I can also have it on the fly for roll on races.

You want stupid amounts of tq down low? SPRAY IT! The TT + NO2 vs TT + SC wasn't even comparable. The NO2 makes almost a vertical line in the tq when it comes on. Spools the turbo's instantly, and at some points in the graph makes 600+ ft/tq.....and that's only on a little 75 shot!!! And we only use the nitrous for ~1 second just to get the turbos to spool. It comes on at 2K, and shuts down by 20psi, which is virtually instant! So the 10lb bottle lasts forever!

If you want to go fast TT+ NO2. If you want to be the cool kid with all the bells' and whistles....

....only problem with the bells and whistles, is everyone expects the car will be retarded fast, most are disappointed when it can't live up to those expectations.

If you do decided to continue, watch the IAT's, as we were seeing 260+ at IDLE!!! A bypass valve will help this, but you really almost need to vent to atmosphere, as re-circ you're just pushing hot air around. Also you need a way to IC the air after the SC. Which either means a complicated piping setup to a FMIC, or an FMIC with a W/AIC, after the SC. Either way, it's alot of crap to cram in there.....


CK

Blitzkrieg

I don't hate you, I'm going to Bora Bora for 17 days, leaving in the morning!

_zebra

CK, you made some good points. i've seen your videos & read through your thread on 3si, but there's a couple things i should clarify...

i understand the blower itself won't be a restriction because so long as it's spinning (which is obviously whenever the crank is turning), it'll keep moving air. the restriction i'm talking about is Magnuson's manifold for our cars. its less-than-optimal design has proven to have a tough time keeping up with airflow requirements in the higher RPMs until you do some decent port work and add a bit of volume to it. that leads me to the spacer i mentioned.

the past year & change has seen quite a few PD builds running a 1/2" to 1" spacer made of phenolic resin between the upper & lower halves of the manifold that not only provides increased airflow capacity but has also shown a good decrease in IATs from the better airflow through/around the intercooler (which, unlike the M90, is integrated into the manifold & has its own heat exchanger up front) as well as having the overall blower temperature (which is already significantly lower with a TVS2300 than an M90 or MP112) go down due to the insulating properties of the phenolic.

another feature of these top-mounts is the built-in manifold bypass valve that allows the lobes to essentially free-wheel under vacuum to minimize drag on the crank. although it's probably too small as-is to serve as the bypass a build like this would need to allow the turbos to completely bypass the supercharger compression by blowing directly into the lower manifold, it's this principle that i was looking to achieve so that there's minimal drag from the blower in the upper RPMs where the turbos should take over because that's when the bypass would open & take most of the load off the lobes due to the upper/lower manifolds having closer-to-equal pressures (theoretically).

as for the pre-heated charge air from the snails, that's why i suggested using the behind-the-bumper A/A intercoolers between the turbos & the intake to cool the charge before it gets compressed again. so in total, there would be the 2 A/A for the turbos, the 1 A/W outside to cool the IC water, and the W/A inside the blower. another technique would be to incorporate meth rails beneath the internal IC (which i was told is a possibility using the spacer) as a final cooling solution.

one more aspect i believe helps this kind of build out this time around is starting with more than twice the displacement of a VR4 & needing less RPMs to achieve the desired effects. this lends to a little less work on the system, less boost needed, and less heat overall.

dude, trust me - i know you ain't no dummy and have been around this block before, and i sure respect your experience. i'm just trying to revisit your original science project from a fresh perspective and using a little newer & different technology that i think could make this setup a possibility and more worth it.

sounds like a blast! and the weather is sure to beat what we've got here.
have fun!!

and is your car done yet? i'm too lazy to dig up your thread right now

chuntington101

I say do it! it has proven to be very sucsessfull in other cars, in fact i cant point you a a hillcilbing evo that is tacking out and out tracket records thanks to he twin charged route he took.

Key things to remember is cooling of the air BEFORE it enters the SC. Also dont forget to size the turbos acordingly. probably best to monitor backpresures to ensure your turbos aren't chocking the setup.

as some have said there will be cheaper way to get the same results. N2O works great for adding power to SC setups when need or to help spooling turbos.

Chris.

0CK@UPPCOS

More power to you! LOL,

If you're looking at a bypass design, you should be looking into clutching the SC as well. No sense in spinning it at higher RPM's if it's not doing anything.

Where you're going to run into the most trouble however is with the bypass valve. At what point/boost/RPM do you open the valve? If you're running a compound setup, the SC is multiplying what ever you feed it, so opening the bypass will show a sudden loss in boost/power, as the turbos try to catch up..... That's where most everyone runs into trouble. Trying to tune the crossover point. Much like the sequential turbo setups with the RX7's and what not. Just to switch from one turbo to two, there's a few solenoids, bypass valves, and even reed valves. Still they produce somewhat of a flat spot in the power band, and they're a pita to keep working properly!

The closest I've seen to this setup was on an EVO. I think he was in Denver? (can't remember). But he had it with the clutch, bypass valves, he even had his AC redirected as an intercooler-cooler! Sub zero AIT's! Do a search for his threads, he's probably the closest one that I know of to accomplish this properly. And even still after a couple years of screwing with it, he abandon it. But if that's the direction you're looking to go, follow up on his work, and take it from there.

CK