So, me and my tuner kept bouncing back ideas of improving my current Ti setup to not have these strange belt issues. Also my wife gave me the thumbs up since I sold the Vette, so it's a matter of time for the world to get it's crap together again.

(Notes in parenthesis is for added context)

*The sole purpose of this build is to be one of the very few convertible Drag Zs. It's what I imagined from the start, and I plan on completing it no matter how much money I waste from it. Being a pioneer can be fun and rewarding!

(For an update or anyone curious on what steps I've done trying to fix it)
- Replaced belt with fleetrunner
- Installed a Timrod radius rod on bracket
- Replaced tensioner
- Added small idler near blower pulley
- Bought pulley laser alignment tool. All pulleys are aligned perfect
- Checked and Tested all other accessory pulleys for any seizing or damage (All fine)
- Gone through 5x belts testing various tensions (all unsuccessful, either too loose to get any good boost or too tight and belt snaps/breaks ribs from sudden decel)
- Rerouted belt, helped a little, but still snapping

Now, I pretty much gave up the idea on building the Ti as much as possible because it's just too much time trying to think of various ways to fix the issue of belt slip/snaps.

One thing I haven't seen much of at all, is any twin-charged Zs.

I thought about playing with compound boosting, but there's not a lot of info about it. (Most twin-charged documentation is based on OEM cars and clutched superchargers, not a lot of info based on higher horsepower applications coupled with a clutch-less centrifugal supercharger)

Before you jump the comments, I'm aware of a lot of reasons why people don't do this. (Mostly from the very inefficient power and piping. But power is power, I'm chasing numbers here)

Reason I mention piping, is that I planned on adding a rear mount setup for the blower to compliment. I'm not really concerned on the piping, as I planned on routing it through the interior of the car and adding an icebox to the convertible top compartment. (I want to make up for lack of efficiency as much as possible with cooling)

Now on to all the technical questions that are throwing me off at the moment.

1. Compound boosting, exactly what is the formula for calculating boost? Torquecars.com made a segment about how they generalize 10 psi + 10 psi = ~30 psi compounded boost. By that reasoning, If a supercharger (s) pushed 20 psi, and a turbocharger (t) was pushing just 10 psi.
Would the equation look like (s x 1.5) + (t x 1.5) = Total boost? Or is it more complicated where the first forced induction modification compounds higher than the latter modification? Is the boost affected by the CFM/Efficiency of the turbo size/trim/etc? But if there isn't any variance, could it really put out 45 psi that easily by that logic?

2. Since turbo lag is pretty much non-existent, especially using a Ti trim, would going twins vs single really matter? Is the only variance I would face is just costs?

3. With compound boosting I would try to avoid 30+ psi for now but I'm also confused about would a boost controller simply fix that issue with external wastegates?

4. Running multiple BPV/BOVs. Would it be ideal to run 2x BOVs? One loaded with a supercharger spring between the supercharger and turbos, and a Turbo spec'd spring on a BOV between the turbo(s) and throttle body. At what boost threshold would 3x BOV be necessary to where two BOV's are needed between the Turbo(s) and the throttle body?

5. Can you wish me all the luck? I'm going to need it doing this....

If there's any other missing complications I missed, I'll try to explain because I've might've thought it through already or let me know so I can know what info I need.

 

I'm def not an expert here but are you running a fluid-damper crank pulley? With the engine combusting only every 60 degrees I can see how that would be hard on belts. Also are you snapping Gates belts?

 

yes it’s running the Fluidampr at about 70% belt coverage as well. I’m using the gates fleetrunners.

 

Pretty sure users BigBlue and OldManZ are running Vortechs in mid 500s without problems. I'm an FI noob at 410.
Really can't advise you on compound boost, def interested in this project!

 

All in my humble opinion and I respect your progress and discoveries on the platform ... so take all of this as only my opinion and constructive criticism. My immediate thought is that you're asking too much out of the supercharger and you can only spin it so hard and put XYZ amount of tension in the belts. Furthermore, as previously discussed that theres a point of diminishing returns on belt driven superchargers.



I think your achilles heal will be 'complications' ... I would make any FI system as stupid-simple as possible

Someone did a compound turbo / supercharger setup back in the day but it didnt yield anything special...if I remember right it was a stillen roots and single front.

I dont think the problem is making big boost and big airflow. You can do a single turbo that'll hit 30psi / XYZ airflow that'll yeild 800hp without batting an eye. If your in for big numbers and want a project than find the inefficiencies in a turbo setup and go about fixing them.

What you've posted is far too complicated for practical usability - I found this out the hard way with my first greddy twin build (especially as it related to oil cooling and oil lines).

You have way too many fail-points and hoops to jump through. One wrong move and you'll melt the system down.

With all that being said ... when you take this on, do it in baby steps. Do not try to build this all in the same build. Build one FI system at a time, run it for a few months before add the next. This is already overly complicated, overly complex, going to be expensive, and at the end of the day wont yield any results different than a traditional FI build.

my 2cents

 

Agreed completely. Trying to attain as much as possible on a 6 rib becomes pretty pointless when you've exhausted all the resources you can.

Not interested in simple and standard. I more of a person who likes complications (to an extent). I just want my own little unique build rather the typical "norm and practical."

But what turbo unit were they running and what was their power goal? Did he do it for show like most others?

What's inefficient about a supercharger building boost for the turbo faster? I mean sure, it may be inefficient because it sucks up a lot more fuel and robs quite a bit of engine power itself. But the end result is what matters, and I intend to have some fun with it.

I plan on visiting my tuner this week to see what he's been working on. Right now he's building a compounding twin turbo setup just to get a better grasp by using a small turbo to feed a giant chinese turbo (on a VQ no less)

I'll try to grab some pictures to post. It sounds like an interesting build and I haven't seen it yet.

Dedicated trailer car, not worried remotely about practicality. (I planned on handling oil cooling with a dedicated oil cooler and scavenge pump for the turbo.)

And what fail-points are those? I've sorted through quite a lot of them and I'll answer any the best I can.

Eh... the Link G4+ has surprisingly a lot of nice fail-safes that I use already.

Well the first step is getting the biggest pulley I can fit so I can maybe just hover around the high 500/low 600's for a bit. Kinda pointless starting a new build when the old one doesn't even red-line without crap breaking. (Fkking belts)

I want to enjoy this build and actually keep track of it for once. Rather taking like 8 pictures total for an expensive build.

 

Switch to a cog drive. Needs less tension. That's what we always did with the High HP V8 cars. When the belts slip, we go from 8 rib to cog.

 

I'm sure ATi could make me a crank pulley with a standalone cog gear, although I'd also have to tube chassis the front end just to make it fit. At that point, it's better off just going crank driven and up-sizing to a V-30.

 

oh I know! I appreciate that about you...

but just because it's shiny and has pipes and hoses running everywhere doesnt mean it's better...to me - 'complicated' means expensive and gonna break, and gonna be difficult to fix ... case-in-point: all german cars

Make it simple, make it easy and cheap to fix ... case-in-point: Honda K series engine...


Let me find it...please hold!


so you're thinking about a belt-driven supercharger pushing air back to a rear-mounted turbo, then back up to the throttle body?

you're moving a lot of air through a lot of pipe, compressing a lot of air through a lot of pipe multiple times, a lot of bends, a lot of couplers... all which takes energy/power to push and these little inefficiencies will add up. Ultimately this will cost you power from the wheels and time before air:fuel hits the cylinder walls.

so the same problem you are having now with being able to push the blower hard enough to create boost as hard as you want will be amplified but now you have exhaust back-pressure to fight bc you're pushing a turbo along with the supercharger...all which you're introduced multiple inefficiencies along the way.

now youre over-pushing your blower to force air through a turbo that is an exhaust flow restriction, and reducing the power the engine can create, which is reducing the power needed to drive the supercharger, which is now reducing the amount of charge the supercharger can flow, thus reducing the air flow to the turbo

it's a multitude of many things taking power from the crank...death by a thousand cuts...

So you dont want to drive it? You dont want to take it to a track/drag strip/event? You just want a shiny, overly-complicated engine bay, with oil lines, and charge pipe that makes 500hp?




​​​​​​​Indeed link has many fail safes - it's why I jumped from Haltech! Many scenarios that the link (or any other ecu) cant predict. But you'll find it!


​​​​​​​(Take this the right way - I say this kindly and with respect, I'm not being dick) your 500-600hp build isnt fully functional and you have basic issues that are halting it's progress, what makes you think you can add another FI system to the mix and have it not only work, but work better than the supercharger now?

crawl before you walk
walk before you run
run before you sprint...


​​​​​​​​​​​​​​Make a build thread...I take too many pictures! but...a picture says 1000s words...

 

My daily is a Benz, and let me tell you about it......




Okie dokie!

This part I'm confused about. I don't understand how I'm pushing the blower further when I'm going with a larger pulley to reduce boost from the centi. Guess I'll find out when the time comes.

Also, on the exhaust back pressure. This is where I'm hoping to get some good advice from those that are highly knowledgeable on finding the right Aspect Ratio to get the right balance and use the high back pressure to my advantage.

With there only being maybe 6 inches of piping, effectively making the downpipe just a dump, I'm not too worried about back pressure in that area. As for the block to the turbo, I'm currently running PPE long tubes and a Motordyne TDX 2. I'd imagine I might have the opposite problem of not having enough backpressure.

Regardless, when it comes to it, I'll measure the back-pressure to see where I'm at. Hopefully it wont be necessary to go to any extremes such as a 1.32 A/R.

​​​​​​​500hp thats mean lol. I made that on the Sci with meh amount of boost.

But I meant it as trailering to events. (drag strip, if I'm not lazy MAYBE cars and coffee)



​​​​​​​Best thing ever. Wished I dropped the uprev a long time ago.


​​​​​​​I think you misunderstand what problems I'm facing with the current setup I'm trying to confunkle.
Essentially it's like this:

Too little tension, belt slip and boost stuck at 16 psi and just stays stagnant. (you can feel the belt slip, and I haven't tested the textured coated pulleys yet. At this point, it probably wont help fix the problem.)
Too much tension, ~ 4-5k rpm @ 20-25 psi (varies), the belt says nope, I'm out.
Went through too many belts trying to find a middle ground.

​​​​​​​Yeah I gotta make another one. I'm still deciding if I want to go with twincharging or test different tech.

Compressed air supercharging looks very interesting, but the fact one 1/4 run will drain the entire system kinda needs work. (Or I could just throw like 8 tanks in the car)
Unlikely choice, but who knows.

 

The turbo always comes first in a compound setup.

Vortech has cog drives for all of their head units, along with cog idlers. Only part you should need made is maybe the drive pulley.

 

I can't find that damn supercharged/turbocharged Z ... I'll keep poking around for it...

back pressure is a myth on FI ... it has it's time and place for NA and 2 stroke vehicles but no on FI.

Running a 1.32AR blower is a fools-errand, you'll only spool it when you're at redline...You're compounding the problem even more! You're gonna push the supercharger hard only to have a turbo that's getting in the way...

If you ask me - you're asking too much from the supercharger ... it sounds like 16psi to 18psi will be your ceiling if you want longevity.

I'm all about seeing this take shape and come to life so I'll simmer down on the criticism and let you do your thing and be as helpful as I can.

 

Not correct at all actually. The experimental kit for the Vortech Ecoboost mustang routes the discharge of the centi into the intake of the turbo. So routing the blower into the turbo works as I'm hoping.

This is actually what brought up the idea.

That's the thing, when I bump up my pulley sizes to an easily manageable size it'll push out 16-18 psi to the turbos itself. The biggest problem I'm facing is the absolute lack of information.

This is why I wanna try it so I can see for myself if there can be any interesting gains. Like I mentioned earlier, it's not really about how much power I'm losing, it's more of what power I finish with.

The part I'm most excited about is seeing how the powerband behaves. I just hope the Tomei 264's/ported heads flow enough to where I'm not losing a whole lot up top, but it might be better off for the mid-range.

Time will either tell the results, or the catastrophes I'll face. I don't mind being the first to take the heat. I been trying to do as much in depth research I can about calculating what aspect ratio I would need, but I lack the information of what back-pressure I'll have.

Once I have the bigger pulley installed and the car tuned rather delaying it for so long, I'll do some tests and see if I need to think about adding reducers or play around with the exhaust piping.

 

hence experimental and why you dont see everyone mustang on the road with this mod...

so what happens when your supercharger, say at 3000rpm, is pusing 15psi of boost but your turbo is still spooling up? does the manifold see 15psi or does the manifold see 0psi (from the turbo)?

people have done it before but with not enough success to make it 'aftermarket' mainstream and probably why it hasnt been done in the OEM.

Yes, you see compound turbos from Mazda and Mercedes Benz, but not with a supercharger...

I dont think you'll see gains beyond the trouble you're walking in to...but I'm in for results!!

I think youre gonna be disappointed ... the engine will make horsepower but by the time you power the supercharger, deduct the efficiency losses with the amount of piping/bends, and the turbo lag the wheels will see much less power than you are envisioning.

You can have great cams and high-flow heads but if everything before this is provides a restrictions or inefficiencies than it wont matter...

Back pressure on any turbo/supercharger build is a bad thing...adding back-pressure to a FI system is one more restrictions you'll need to overcome and one more thing that will decrease the amount of power getting to the rear wheels.

This smart ... get the car up and running 100% before you start experimenting with a turbo and/or a second / compound FI system...

 

Physics doesn't like this idea. You're wasting energy. Why use the energy of the S/C to spool the turbo? That's what the exhaust is for. The exhaust contains a lot of kinetic energy that's just going to waste. This is why turbos are so popular with the OEMs and Superchargers are almost non-existent any more. Doing it the way you want also necessitates two fresh air pipes in addition to an exhaust pipe. One to bring air from the S/C to the turbo and one to bring air from the turbo to the engine. Running it the other way requires only one fresh air pipe and one exhaust pipe. Using the turbo to help spin the blower also lessens the parasitic drag of the S/C. Every single production compound system uses the turbo to feed the S/C. It's simpler and more efficient.

 

They stated that the kit wasn't idealistic for two reasons. There wasn't much support at the time for fuel upgrades on Ford's Direct Injection system. And the biggest reason was the factory turbo was too small to benefit.

I can see why they wouldn't make these kind of kits based on factory restrictions.

The manifold sees more than 15psi assuming the turbo is building boost and I have enough back pressure to spool the turbo at 3000rpm. I mean, I can only think of how the turbo is being fed air that's been made denser(boosting boost per se).

There has to be some reasoning that someone at Vortech was like "Hey, lets twincharge and make a centrifugal unit feed the turbo on the Ecoboost test car."

The videos of them discussing how it drove and behaved, made me really curious on what would happen if you tried it with units that are a little bigger.

We have a big fuel system, using E85... if there's a weakness, we can throw a little nitrous at it and see what happens.
Honestly hope it doesn't get to that point, mostly because there will be enough pipes and lines.

It's definitely going to be trial and errors. Mostly experimenting with pipe sizing on both the intake and exhaust. I just started welding school so it'll also be good practice and far cheaper labor.

It's tough because I can't say anything without any information yet. Once I can get the back pressure testing done, I'll have a better response on what I planned to do.

[/QUOTE]

Baby steps

Car still runs and drives, just not WOT or 4k+ lol.

I think a lot of people are getting the wrong idea. I never intended this to be efficient. Yes, the setup is probably rare because it's impractical, expensive, over-complicated and such but it would be interesting to see what would happen.

Either I make big power, or just a little more compared to just going single. Time will tell.

 

great way to put it...

I was gonna say Einstein's 'Energy is never created or destroyed, it can only be transformed or transferred from one form to another' ... no such thing as a free lunch in nature


I have the 3.5 eco in my truck and the blowers fall flat around 4000rpm to 4500rpm...they are sized for max torque, not max hp...which is cool, I dont spend much time at redline anyways!

Let me ask this ... and this is how I understand it

assumptions:
SC makes boost at 1500 (0psi) through 6000(16psi), linearly
SC has a net delta air flow of 0 cfm @ 1500rpm (meaning the engine is consuming as much air as the SC is pushing)
SC has a net delta air flow of 6000cfm @ 6000rpm - I have no idea what cfm a supercharger flows at redline - An assumption of 1cfm per rpm

Turbo makes boost at 3000rpm (0 psi) through 6000 (20psi), linearly enough
Turbo has a net delta air flow of 0 cfm @ 3000rpm (meaning the engine is consuming as much air as the turbo is pushing)
Turbo has a net delta air flow of 12000cfm @ 6500rpm - I have no idea what cfm a turbo charger flows at redline, I'm assuming it's twice as much as a supercharger.

also assuming redline is 6000rpm for ease of calculation


@1500rpm, supercharger = 0psi (1500cfm) (boost threshold), turbo = 0psi (0 cfm) - the manifold sees 0psi and the engine is consuming as much airflow as the SC/Turbo is making...

@3000rpm, supercharger = ~8psi (3000cfm), turbo = 0psi (boost threshold) - the manifold sees ~8psi and the engine is consuming less airflow than the SC/turbo is making, thus 8psi of boost, 3000cfm of airflow

@6000rpm, supercharger = ~16psi (6000cfm), turbo = 20psi (12000cfm) - the manifold sees 20psi from the turbo (or only 16psi bc the supercharger is the limiting factor), but the engine only sees 6000cf becasue the supercharger isnt feeding the turbo enough air regardless of psi.

This is probably why the turbo has to come first...


Indeed baby steps...

runs & drives under 4k rpm is unacceptable if you are shooting for the stars!

The ONLY way this will work is if you are unbelievable efficient...you have no margin for inefficiencies!!

A good documentary you may want to watch is "the truth in 24" ... it's a documentary on the Audi R10 Le Mans Team and their journey on their five Le Mans victories ... and an underlying theme of the documentary is how efficient their entire program is...not just the car but the entire teams from design, manufacturing/fabrication, operations, races ... everything. The team does not waste an ounce of energy. The Le Man R10 car harnesses every ounce of energy in the gas tank.


The last thing you want is to be sloppy with 'efficiencies' ... every wasted ounce of energy is power robbed from the rear wheels. Sorta hard to conceptualize - but if you get it, you get it...

With boost inefficiencies comes heat, heat will rob power as you'll have to retard timing...

it's rare/expensive/impractical/overly complicated because it doesnt pan out in the end...

It will likely make power but not nearly as much as a simple, properly sized, properly built single turbo...

All my two cents, please get going on this soon...in for results...

 

Well, you're missing a big part of the equation.

You're treating the turbo as if it's being fed atmospheric pressure. This is where compound boosting gets interesting and I think people might be missing out on what I'm trying to do here.

Here's part of an article that might explain it better. Note they talk about how the supercharge feeds the turbo, not the other way around.



Now that I really look at it, it's actually really efficient.

With making less boost on the blower, I'm getting less parasitic loss and even better reliability for the blower without having issues of overspinning.

 

^^^ no no no ... I get it, supercharger to turbo...

it's not efficient, you'll see when you put time into this and you'll making less than your 18psi single SC setup (if youve taken that up to redline yet).

but give em hell!

I'd like to see it come together, I really would!

 

First, what makes you think they know any more than any of us? I've got 30 years of building experience, how much do they have? Second, that's not what they said. They said the S/C provides boost at low rpm and the turbo provides boost at high rpm, not that one feeds the other. Third, that only applies to a positive displacement S/C. Your Vortech centrifugal has an even more top heavy power band than a turbo.