TTRotary

Thanks for the pointers Mr Mojo, and sorry to cause a ruckus. I'll PM you tomorrow, if that's OK, to make sure I don't step on any toes in the future on this topic.

Lastknight0

Very informative answer Thanks, now i have a much better idea of what i want to do

baf2000_1

TTRotary,

This would be a great for those of use that like the rearmount system strong points:

- Ease of install/uninstall
- Good power gain without taking the engine apart.
- Reduced cost
- Potentially more reliable since there are fewer parts added.

I think if STS had a $3995.00 kit for the Vette like the other kits they sell, they would sell quite a few. Though I like the idea of a Twin Turbo, I do not need that much power.

I too have thought about this and have gone so far as to read the STS patent papers. Some engineering changes I might suggest:

- A self contained Oiling system
- A more production like intake system
- Perhaps an longitudinal under the car intercooler


JMHO...

TTRotary

I totally agree, these would be flying off the shelves. There is this erroneous perception that Vette owners want to pay more for a "premium" system, but that approach is costing tuners a LOT of business, IMO. All that happens is they get lots of drooling, but in the end, people are just turned off by the high prices.

I am working on the contained oil system. This is safer for the motor also. The question is whether the journal bearings (which use a pressurized oil layer) can function at pressures lower than the 40 psi an engine provides.

A stock intake appearance is a primary goal.

Undermount intercooler is not feasible because the tubes are fragile and would be ruined by debris very quickly.

IwishIhadAvette

Any thoughts on using a turbonetics T62?

TTRotary

This application requires a compressor to deliver 51-57lb/min at a pressure ratio of 1.45. If you look at the T62 compressor map, you will see the best it can do at 1.45x PR is 40lb - nowhere near the airflow requirements needed. The T76 is barely adequate, delivering 55lb at the requisite PR, but you are right on the choke line. This is the same story with the GT4202. The difference is that the GT delivers 65% efficiency whereas the T76 delivers an unacceptable 48% efficiency. What this means in practical terms is that the T76 will produce a much hotter intake charge than the GT will. This is why I do not want to use the older T-series Garret / Turbonetics stuff.

None of this would matter that much if our operating parameters conformed to a more normal part of the typical compressor map (higher PR's against lower HP). Here, we have a low boost (turbos less efficient), high flow application. In essence, we need a big fan with some pressurizing capability - i.e. your typical centri S/C application.

The last problem we face is packaging. Big turbos like the GT42 and T76 are dimensionally huge - imagine the compressor side the same size as a Vortech V-trim S/C head unit - and you see you have a barrel-shaped object 11 inches long and 10 inches in diameter. This CAN be packaged at the rear of the C6, but is is heavy and bulky.

The main limitation is compressor air flow. I am still reviewing custom housings with Garrett dealers and won't have anything until Monday. Plan B is smaller twins, which may cost less in the end anyway (the GT3571s are $675 apiece against the $1,400 GT42) so we'll see where this goes.

I have made progress on the remote oiling system. The journal turbos need at least 25 psi of oil pressure. That is no problem for oil cooling-circuit pumps from Mocal or Weldon. That entire system, including tubing, pump, and the radiator, can be had for $500-600. Not cheap, but less than the prepackaged Ford or GM differential coolers (referring here to the GM T-1 cooler for C5s.

0Cajun @ Edgyvette

This is going to be very interesting! I will stay in touch TT! Glad to someone who has the knowledge and the motivation to take on a project like this as it could benefit all of us immensely! Thanks bro

Cajun

IwishIhadAvette

Another Idea (Probably a far fetched one) is two small low cost (journal not ball berring) turbos arranged sequentialy so the waste gate of the first dumps into the second hotside and the waste gate of second goes to ground. In theory it would spool faster then one big one and still support high flow with low pressure. It might also fit into a spot that one big one wouldent because you could position one behind the other. Note im not saying run the cool compresor side sequentialy I am saying vent excess gas from turbine 1 into turbine 2 thn turbine 2 to exit. Not sure Im thinking about it right but thought I would run it past you. Might be more expensive, and certainly more complex to fab up.

TTRotary

Won't work because you will stall the second turbo and surge the first one. What happens is: turbo #1 receives full exhaust energy and produces boost (or really airflow). Second turbo gets residual energy and produces low airflow. Airflow from #1, being much stronger, backs up through #2 compressor. (the compressors HAVE to share air path, even if exhausts can be 100 separate). You stall second turbo, so all air goes thru 1st one. It surges. This works if you have true sequential, but that is an engineering nightmare. Toyota and Mazda spent millions on sequential turbo systems for the FD3S RX-7 and Supra MKIV and never quite got them to perform reliably.

One thing that is not a problem on this application is boost lag. There is so much exhaust flow and base torque with this motor that you'll never see any lag. The challenge is finding a compressor big enough to move all that air efficiently.

Nothing yet from the turbo guy...

0APS

Just a word of caution and I hope that this helps you with your endeavours.

Most if not all of the large GT42 sleeve bearing turbochargers (not GT series dual ball bearing gasoline turbos) are designed for diesel applications (much lower exhaust gas temps) and therefore have lower spec material in both the turbine housings and turbine wheels (not inconel turbine wheels).

I found out the hard way a few years ago when turbine wheels and turbine housings started to melt and crack frequently on a large V8 gasoline single turbo applications, not fun. :o

Even with the turbo mounted in a remote rear position the exhaust gas temps will be much higher than a diesel engine generates and hence beyond the specifications of the sleeve bearing GT42 diesel turbocharger.

Best to insist on a large turbocharger with both inconel turbine wheel and Niresist high temp turbine housings, it's much cheaper in the long run for a gasoline turbo application, good luck.

Peter

TTRotary

Hmm, I was not aware of this. Big thanks for the heads-up Steve. Oddly, this was not brought up by the Garrett dealer I am speaking with. He and I are still waiting for info from Garrett on whether a big single is feasible. They are appraently prepping their race car for next month, and are slow to answer tech questions

I may wind up using twin GT3271's anyway. They package better and are operating in a better part of the compressor map when combined. Besides, I found one retailer selling them for $675 apiece! The other neat thing is they accomodate an integral wastegate ($100 more each). So even though using two, I am under the cost of a GT42.

I am actually very pleased with the prices I am finding for parts. $500 for the IC (from Racerwholesale - looks like same one STS uses for the GTO), $250 for a BOV, $500 for my remote oiler (Mocal pump, fittings, and exchanger core), and $250 for a Kenne Bell Boost-a-Pump.

That's right at $3,000 for the major mechanical bits. I know there is much more $$$ in fabbing the pipes, but I think I can get this done for $500-1,000 in aluminized. It won't be show quality, of course, but that is not important to me. Tuning and dyno time is the unknown, but there are already plenty of 5-7psi tunes out there, so this is not uncharted territory. We'll see.

Aside from all this, your kit is gorgeous. Truly looks all-pro. Can't wait to see pics on the first CF member install.

chempowr

First off, I love to see people with motivation make there own mods to cars. I would like to warn and emphasize what APS has stated that building a turbo kit is more expensive than you think. You may have experience with turbo cars but converting a naturally aspirated car to forced induction gets pricey quick. I have personally converted a 5.0 Mustang and just recently 1959 Chevy to turbo and although I saved alot of money doing almost everything myself and exhausting my and my buddies shop, tools, and wholesale connections, I still went way over budget. Friends of mine with Grand nationals and supras have it pretty easy when they want to upgrade their cars but we have to worry about upgrading and FABRICATING EVERYTHING.

In the end, I have been very happy with the performance of my FI cars but I also have alot of worry about part failure, running lean, popping head gaskets, and yes melting pistons (which does happen with good tuning and sophisticated electronics/fuel systems). So looking back, I would prefer buying a kit over fabricating my own.

0APS

No problem. When dealing with Garrett or a large Garrett dealer you need to ask the right technical questions otherwise you may easily be mislead. I know this as we at APS have been dealing with Garrett for many years and the correct tech information certainly exists if you can reach an experienced Engineer within the corporation.

Bottom line, you need to clearly state that the intended turbo application is for a gasoline engine other wise you may well end up with a low spec diesel turbocharger not designed for gasoline operation, produced from lower grade materials designed to operate at much lower exhaust gas temperatures.

Peter

TTRotary

Progress report as of 2/25:

Unfortunately haven't got very far due to being very busy at work. Still no word from the Garrett people, but this really does not matter any more as I am 95% sure that twin GT 3271s are the better way to go. The good news is I have a fabricator who, after looking under the car and poking around for 1 hour, says he can do the piping for $600 or less. I asked if he would agree to $300 up front and $300 on completion, MAX, and he said "yes" and that the second installment would likely be even less. This is in aluminized, of course. I have seen his handiwork around the shop and his welds are excellent. He does mostly SuperVee and desert racing frames, so he knows his stuff, and is highly regarded by the desert racing crowd.

I am getting closer on the fuel system. Best I can tell, it would be best to install a second OEM pump in the tank running parallel to the first, to ensure flow at the higher pressure. I will move up to Bosch 911 33# injectors, and the KB Boost-A-Pump will provide boost-indexed fuel. Looks like I will need 6 Bar fuel pressure to provide adequate fueling at 5psi where I am in the 11.0 range. That is at .65 BSFC in case anyone is wondering. The big question mark right now is whether the OEM fuel line is adequate. Looks like it is, but I need to confirm.

So this is coming along and is looking better and better cost-wise. The problem is time. I am travelling next 3 weeks and will have no time for this. Maybe Garrett will be back to us by then.

Chempower RE: your second paragraph - I hear ya man. That's the area where I get nervous. Then again, we know its worth the trouble when things are running right.

Bruce

As some one has mentioned hidden cost. I sold my D1SC custom cog setup and decided to try rear mount turbo experiement. When I did my rear mount turbo C4 383LT1. I estimate cost around $3500max. I end up spent almost $6000 all say and done. 16g 304SS cost $74 a bend and or 321SS cost $94 a bend. I spent about $500 just for the hot pipe. just a thought. My turbo is a T6 flange and flow 130bls/min at 25psi I should hit 1000rwhp.