TTRotary

Fellow members, after much reflection on the matter, and having reviewed all the forced-induction systems out there, I have decided to initiate work on a single-turbo system for my C6. The objective is simple and specific: to deliver C6 Z06 acceleration levels for no more than $5,500 installed and tuned, which in turn enables the owner to keep the total upgrade budget for their car under $10,000. I will report progress and detailed information as I go so that others can follow and adopt.

This system is NOT intended for those wanting flexibility to add significant power, nor is it intended for those who seek the cachet of a “Twin Turbo Corvette”. Target power levels will be right at 480 RWHP and will be achieved via 5psi of intercooled boost with excellent boost response on a stock-motored car, at minimal cost and complexity. This profile reflects my belief that: (1) a stock LS2 cannot be safely operated at sustained power levels if the motor sees more than 5psi; (2) the driveline (the differential in particular) is similarly limited; (3) any additional power will require, at a minimum, a Z06 clutch and bigger tires / wheels to hold and put the power down. These items alone will realistically add nearly $3,500 to the price of the engine upgrades. There is therefore no point in investing in a complex twin-turbo system if the owner’s TOTAL budget is limited to $10K or less and 5psi. Again, prospective acquirers of this system would have to understand that 480-500RWHP is about it and be happy with that decision.

My objective is to keep costs at or under the $4,000 range for the system itself, including tuning. That would not include cost of installation, but I plan to design the system so as to minimize installation labor and time. Tuning is possible through any reputable tuner.

This would be a rear-mount setup, but that is where similarity with any existing system ends. This system will use a single Garrett journal-bearing unit (to avoid the need for water cooling) and will probably be a GT42 or GT60 unit – whatever the smallest turbo is that I can use to achieve 5 psig of boost on a stock motor. Analysis of the compressor maps actually favors the GT60, but I will have discussions with Garrett on this point to see if I can get away with the smaller GT42. Another option I am considering is to employ remote oil and water cooling (to avoid tapping off the engine) and so I can go to a ball bearing unit (like GT42 BB option) if necessary. This is feasible since the heat load on the remote turbo is minimal, and it avoids reliability issues of running oil lines under the car. The system will employ a Greddy BOV and a Greddy pop-off valve as extra insurance, an integral wastegate, and a Spearco air/air intercooler. I have my eye on one of their OEM tube&fin (rather than bar&plate) designs as the former usually results in 0.3 psi pressure drop across the core at the expense of thermal efficiency. I do not expect the remote turbo to introduce any significant heat at the 5 psi level, so tube and fin is the way to go, to minimize boost stress.

The kit will be designed to be virtually undetectable in the event of a California-style visual inspection, which includes under-the-hood and kneeling to place the probe in the tail pipe. Emmissions will not be interfered with since the cats remain in their stock location. I will use the transmission tunnel to route pipes, which is possible because of the conversion to single exhaust after the cats. The system is designed so that dual exhausts can be retained at the rear for visual appeal.

FYI, I don’t normally toot my horn, but I have a LOT of experience with turbocharging and have owned, modified, cried over, and learned a lot about 6 turbo cars in my past. These include two RX-7 Turbo IIs, two third-gen (twin-turbo) RX-7s, a MKIV Supra TT in between, and my first car, an ‘88 300ZX Turbo. During this time, I got to know a lot of vendors and people in the turbo turbo community, including most of the turbo shops in SoCal. So I know what I am doing, I am not crazy, and I know this is a 100% feasible project.

I welcome input AS LONG AS it is constructive and is based in technical knowledge. I also want to hear from those seriously interested in this, not just thumbs-up props. Those with negative feedback – please start your own thread because I know this can be done and nothing you say will change my mind. Finally, I want to be clear that I am not doing this for profit. Think of it as a club – the single turbo C6 club.

Thanks for reading.

Edit to correct turbo size typo------------------------

Edited - again - to remove any content that could cause reader to misconstrue me a plugging a product.

Please note: I AM NOT A VENDOR, there will be NO MONEY coming to me. THIS is merely a project I want to share with others.

valdeztke

under 5500? Hmm well if thats right then .... Im in!!!!

0APS

One major flaw in your planning. A GT 35 will only produce approx 300 flywheel HP at best at 5 PSI boost pressure (30 lbs per minute mas air flow). You would need a massive turbocharger capable of at least 60 lbs per minute mass air flow at a 1.35 pressure ratio (5 PSI boost pressure) to produce around 480 WHP on the Corvette.

A GT 32 is even smaller than the GT35 so you're way off track with your early analysis, hope this helps.

Peter

TTRotary

Sorry, that was a typo... meant to say GT42 or 60. :o :o

Thanks for catching that Peter.

I need to go as small as possible to minimize lag. My actual needs at 535HP are 51-56lb at 1.44 PR (subtract 1psi for intake vacuum effect under full load). That is right on the edge of the 42. Only 65% efficiency, but if it spools quicker than 60, that's worth it. I hope the 42 is adequate for my purpose, but I'll verify with Garrett.

ShowcaseC6

WOW 5500 installed and in SoCal! Hopefully it can be done. I'll be looking hopefully around summer if things go well! about 500rwhp is where I am looking to be.

NICK YOSKIN

well spoken, wish you the best. there is a market out there for sure. the guy or gal that wants a turbo that doest want it to spiral into mod after mod deal.
people are, by nature, greedy

TT C6

I think an owner would be better served with a STS, Cartek, or a Kenne Bell kit.
We know the STS kit for the C6 is just around the corner and the the KB kit for the C5 is being released as we speak so I believe a KB for the C6 should be not far behind.

Yes, you might spend a little more up front,
but you have the option of increasing boost down the road.

No one KNOWS what they will want in the future.
I'd be willing to bet that a large percentage of the people that say they will never do it, turn the boost up down the road.

In addition,
"under driving" a blower/turbo which is capable of big boost by running low boost should result in lower intake temperatures which is definitiley a good thing.

Furthermore,
the expandability of your blower/turbo will be a GREAT selling feature to a potential buyer who would like to turn up the boost if you decide to sell your car.

TTRotary

TT C6, I appreciate your view, and expandability may be important for some. For them, I think the STS or APS kits are a great way to go and are a great value.

Many others, however, realize that more boost than 5psi is going to mean significant engine work and a significant jump in expenditures and just don't want to go there. You're now talking about $15,000 and up to redo the motor, and things in the driveline also begin to break. At that point, you're in an expense spiral. Reliability drops, so that the car may no loinger be suitable for long trips etc.

And most importantly, (IMO) once you are over $15K in outlays, you may as well just go to the Z06 and get the no-hassle factory performance.

Those who have thought through all this and have a finite budget, and want a hassle-free system, will be perfectly content with Z06-like power and near-stock reliability at a fraction of the price. Twin turbo kits are cool, but are overkill for a 5 psi application.

I am well aware that more is always better, but at some point, you have to weigh options. For example, I'd love a Mooney Turboprop, but I know my Cessna 172 costs me plenty already and serves my needs, so I stop there.

As far as resale, I think the best approach is to return the car to stock anyway. Having sold a bunch of modified cars, I know from experience that they do poorly in the resale market. Furthermore, most buyers would prefer to buy stock and mod to their liking, rather than "purchase someone else's problem" - at least that is how I think.

Regarding boost potential, you want to size your compressor so that you are towards the right side of the map (inside the choke line) at your target max boost level. E.g. you want the smallest turbo that can deliver target boost. I agree that my selection is good for no more than 5-6 psi and I have warned people of this, but I'll say it again: if you want upgradability, this is not the kit for you.

0APS

No problem my friend, I thought that must have been a typo. The GT42 and GT60 are very expensive turbochargers though the largest GT42 should have sufficient mass air flow for your power goals at low boost pressure.

Given the cost of this large GT turbocharger I'm very much doubt that your predicted costs can be achieved, good luck in any event.

Peter

TTRotary

Actually, did some research this morning with one of the Garrett distributors. The GT42 journal is $1,200, and the BB version is $2,400. ALso, that distributor has a customized version that flows a bit better for my app and is more compact, at $1,700. They call it a 76 GTS.

That, plus BOV/Wg ($600) plus IC $1,000 puts me at $3,200 for basic hardware. The plumbing and ancillaries are the wildcard, but I think I can get there. Maybe $4,500 with tuning is more realistic (remember, this is cost). Either way, it's half the cost of a twin system.

TTRotary

BTW, I'm in this for myself and I'm not making a dime on it and it's time consuming. So if one of the vendors out there wants to develop a single kit, then I'm all for that and would probably be their first customer, if the price were right (about $1K more than what I am talking about). I think there is a lot of REAL demand for a kit in this price range. If not, then I'll just keep plugging away.

The twin turbo kits (yours and STS) are beautiful and they are a steal next to LPE, but they are just too much coin for those wanting to stay at the 530 HP level. Just my $.02 of course.

TTRotary

Clarification: I AM NOT A VENDOR. I am NOT doing this for money, and I am not requesting or accepting money from anyone.

I am simply working on a homegrown kit and sharing that info with others.

Sorry to yell, but my thread in Tech got locked. I can see where some word I used might have been mis construed in a quick read. My apologies to the mods for this.

Lastknight0

I think the project is a great idea and if you can pull it off for around 5-6 grand i'd be very impressed. Personally i'm all about high rwhp, but i don't want anything that's gonna keep the car in the shop constantly or prevent me from being able to take a cross country trip with a bud/gf.

do you think that exhaust, headers, and H/C upgrades will cross the line into needing bigger tires, better clutch, etc. or do you think there's leighway with them?

TTRotary

The tires are right at the limit of stock power. Frankly, after my Z06, I am surprised the runflat F1s hold as well as they do. So you are looking at wheels/tires either way.

headers + intake + tune puts you at 375 RWHP, well within the clutch.

the most agressive heads +cam cars are in the 440RWHP range, so you would wear the clutch out pretty fast. The C6 Z06 clutch is a direct swap and is probably good for 550RWHP.

I think 550RWHP is the limit for the rear end, but that is only an ignorant opinion. Andy at A&A assures me that the rear ends are solid and that the only broken ones occurred on hard luanches at the drag strip on prepped surfaces or with DRs.

My problem with headers is they are VERY pricey for tnot much incremental agin, and they flunk visual automatically. Heads / cam is nice, but gets just as pricey as my project and un-install would cost you another $1,500. If you are going to keep the car and you often drive it very hard (as at a track event), H&C is preferrable to any FI setup. Second best would be any rear-mounted turbo system.

Forget the maggie for that.

0APS

I think you have grossly under estimated the production costs of a single turbo system, there are many more hidden costs that you have NOT allowed for in your plans, I'm sure you will find this out over the coming months.

I'm not sure that your statement regarding consumer cost is correct. I very much doubt that any complete reliable single intercooled turbo system with a fuel system to support 500 whp could be sold near the price that you expect. I think you will find that the real cost of a rear mount single turbo will end up being approx $2500 less expensive than a fully engineered front mount twin turbo system and the real world results will be far superior from a turbo system which retains a far greater level of entropic energy (heat and velocity of the exhaust gasses).

FYI we've conducted a good deal of testing with remote mount turbos and the results (power and torque) are very disappointing imho and not worth the investment, better to just go the extra yards and build a real turbo system imo.

I understand that the tooling and engineering costs are far less with the rear mount approach though ultimately the approach has many engineering issues that are difficult if not impossible to solve (though this of course depends on your performance/drivabilty expectations).

The other issue that would worry me is the security of this system design, this we discussed during our own Corvette twin and single turbo development. As one of our engineers stated during a product meeting, the entire turbo could go missing in approx 3 minutes, now that's a real worry imo.

One guy that I know in the US lost his $3000 twin turbos off his F body. All that was left were the burnt exhaust pipes and signs of a quick blast with a gas axe, food for thought.

Security of your turbo system investment is a very real issue to consider, hope this helps and my apologies in advance if I seem to be negative on your remote mount aproach.

Peter

Lastknight0

Interesting info I will RARELY be running mine to a track if ever so that's not too big of a deal.

You think your turbo along with H/C intake and exhaust would go well over 550? :

Mr Mojo

Just be sure that whoever you use to get the pieces from and do the work(if it isn't yourself) is a supporting tuner and/or vendor.

Commercial sales other than those are not allowed.

Just a hint. If a thread on a subject was closed, you really shouldn't start another until you find out why. AT the bottom of each forum is a list of moderators, but you only need to contact one, and that's teh one who responded to your thread and locked it. If it was moved, the Moderator will contact you.

The PM box is your best friend on this forum.

Now I have to read the rest of this thread to make sure I didn't step on any toes of my fellow mods.

Skunkworks

but everyone’s definition of a silver bullet varies. With that in mind, build the best kit you can at a reasonable cost and let numbers speak for them selves and after a $$$ per HP value can be assessed.

Mike

TTRotary

Peter, I accept your comments as constructive criticism with a bias towards front mount approach and I appreciate your willingness to discuss these issues. However, I feel like we are getting into dangerous territory: A known rear-mount vendor is a forum sponsor, and I can see this discussion degenerating. For the record, both designs have great merit and proven performance, but I am not going to get involved in this and have no further comment.

As for me, this is now a personal project and I will simply post detailed updates on it as I go for the benefit of members. The proof will be in the pudding, as they say.

TTRotary

Not with this turbo. Your H&C would increase airflow, which would in turn require a larger compressor to pressurize to the same boost level. You would have to go to the GT60, but that unit may be physically too big to package. Besides that, heads/cam + headers + intake is $6,000 by itself, and puts you at a total outlay of $15,000. For this price, there may be better options, including a twin-turbo setup with its greater flexibility.

FYI, headers won't make much of a difference in flow and HP with a turbo setup. The $1,800 is best spent elsewhere, IMO.