That's a slightly different situation though! Lol high altitude stuff can REALLY benefit from compounding. People tend to talk about boost presure in turbos, it's actually presure difference you need to think about. Most turbos can achieve a 3 or 4 to 1 presure ratio. So whatever the presure is at the inlet to the turbo you can times it by 3 or 4 and you will get the presure the turbo could deliver.

Once you start to go higher in altitude you reduce the presure at the intake to the turbo. So you loose the peak presure you can make. By compound boosting it let's you double to presure ratio of the turbo setup. So now you have a presure ratio of 6 / 8 to 1! So even in thin air it let's you make high intake manifold pressures.

This is what RR and Alison did with their aero engines to enable high power at higher altitudes.

It can also be helpfull if you have very high drive presides I think. I believe it halfs the drive presure required to make xxpsi of boost.

Have you got any pics of the engine and the turbo setup?

 

Unfortunately i don't. We kinda lose our jobs if we take any pictures of anything here. I can tell you though, they build the "turbo factory" separately from the engine then assembly it to.the engine afterwards. Its the size of a full.size quad cab pickup lol

 

Yeah I had a google and the turbo "unit" looks huge! Is the stock setup a bank of 4 turbos? Lol

 

A C175 isn't exactly top secret stuff. lol

 

Yeah but they don't look to be compound boosted. I guess the high altitude stuff is a little more secret. Lol

 

Yep, we are doing it for the fun and WoW factor and cuz we CAN! It's a stockish 4.8 (blue printed for boost) with a T4 Magnum t60 as a base and then a T6 BW S480 to feed the 60. Goal is to have it it drive like a small motor 4.8 with the right sizes turbo, but then a big turbo to feed the little one for the big power!

The truck is just a toy and will be E85 feed and probable push it up to the 20psi range.

The top 60mm WG just by passes the T60 once it get to about 6-7 psi and let the big turbo to the work. There is a second 60mm WG Pre both turbos in the cross over for overall boost control.

Trucks not running with this setup yet but will be soon.



I also had a compound turbo/supercharger a few years ago. It worked ok and wish I would have spent a little more time tweaking it.

 

Compound turbos= badass + funfactor+ tons more work. You will probably get nothing but stupid power and torque along with wheelspin. A Sequential is not even relevant given the fact that you can use a twinscroll turbo and quickspool valve to turn your setup into a variable turbo. I thought about using compound turbos just for S&G's on my forged 3800, but the quickspool valve or secondary wastegate setup is just so much more effective and you will always have a better top end.

I have full boost in first gear at around 3500 rpms with the quickspool setup.

 

Its not that the c175 is a secret but i can lose my job if i started posting in-plant assembly pictures. We do have access to any and all blueprints. Those are "secret"

 

The cc175that is in the picture isnt a high altitude nor a compound boost setup. 4 turbos is standard set up on a commercial and truck engine c175s. The high altitude is usually in certain 797F dump trucks.

 

*Haul trucks

 

Off-highway truck s

 

Touche.

 

much more interested in the return of the variable vane turbos as it seems you could vary the boost more efficiently without the complexity of wastegates

I believe the new "pooch" (porsche) has them and the manufacturers seem to be going to more high tech turbos

bmw is announced more turbo engines (all of them in the future) and mclaren and other high end exotics are making huge power from little DOHC v8s.

problem is they are still screamin the motors and not very fuel efficient compared to our "antiquated" LS motors which are lighter, more compact, easier to build power and most importantly CHEAP

I'm still amazed by the "truck bomb" engines. I never would have believed 800+ hp out of stock block engines that live that cost under 1k. but many have proved over and over with the right setup they can deliver incredible power and be cheap and reliable (amazing)

if my TT LS6 (forged) in my Z06 ever expires I'm going to slap one in just to save a buck. if it blows, who cares, I'll have less in the short block than a good set of pistons

amazing.

thanks for this forum, it's fascinating

back to the OP, compound boosting is for diesels IMHO. just not needed.

I actually LIKE the lag I have on the TT Z06 because I can have a prayer of getting the car moving before the "torque surge" comes up and blows the tires away.

if anything, I'd like the turbos to come on more gradually and linear like the cent blower cars do. much more predictable putting the power down.

turbos are "load driven" and the torq spike is very hard to control sometimes.

 

I'd really like to see the aftermarket come out with a line of VGT turbos like all the new diesels have. A standalone controller to be able to set boost ramp rates and levels would be the ultimate in boost control! lol

 

WOW! That's the first time I've heard a turbo guy admit to that. I know the positive displacement blowers are crazy with the instant torque they make, which must anihalate tires on a whim. I love the way my centri blower just continues to pull harder and harder the more rpms I feed it. It at least gives my tires a chance of hooking on the street.

 

Thanks for the info guys. Looks like it's just not plausible for me to run sequential or compound. I thought it might be a good idea but looks like it's more work and money than it's worth. I'll think of a different set-up.

 

I had a buddy that did it on his 4th gen Camaro but he always had problems keeping one of the turbos together if I remember right. It was a long time ago and what I do remember is that he did end up doing a single turbo setup instead.

 

Pretty much the original plan was a single. Figured a compound might help and make it a bit more fun but looks like a lot of hassle for what it's worth. Saw how the RX7's were running them and was wondering if anyone has ever tried it on an LS motor.

 

This would be a great solution. However i feel it might be a while as we need the turbos to become more mainstream (used in the likes of BMW's and Fords) before they will appear on the aftermarket arena.

 

As someone who built a compound setup in a car(MK3 Supra) before and is now putting a 5.3l with T76 I say it is not worth the head ache. I did it because I could and it had never been done before but the theory K.I.S.S=Keep It Simple Stupid never seems to fail in street cars. Don't get me wrong the compound was cool but such a head ache to work on. Proper sized single with a QSV or similar system and you will be so much happier!

HTH,
Seth