Turbo-Geist

With the stock engine, it had a range of 550 to 900rw. With this build, I wanted a range of 850 to 1200rw. It's been stated throughout the build. I knew what engine size and exhaust size I was going with from the beginning. I was up front with Race Engine Development, U.S.A. Racing Engines, Lunati, the multiple companies I consulted with for a camshaft design, etc. I told TTi my plans when I called and ordered the turbos.

Let's get specific about which system works and controls boost with mufflers and the maximum boost only power it will make.

Yes, a 347 with 6265 turbos, 2.5" downpipes, 2.5" midpipe, and 2.5" Borla exhaust system will allow for ~ 550 to 1000 rwhp (to be determined). The 6265s should be good for at least 68lb/min with a 'B' cover, 90 degree discharge outlet, 5-bolt 0.81 A/R housing. Therefore they should support ~1200 rwhp if not slightly more. What is your highest boost only dynosheet with these turbo's? Are there dyno numbers showing the progression of manifold pressure vs. rwhp for this system?

Precision 6265 Data for TTiX with 347
18 psi ---- xxx rwhp
20 psi ---- xxx rwhp
xx psi ---- xxx rwhp

Chris Stewart

I haven't turned mine all the way up yet, and don't have the data you're looking for there, but we have the same turbos and a local guy with 427 as well. Both of us run 2.5" pipes with mufflers and have no issues turning down the boost. I seriously doubt 3" pipes would throw things off that much, but definitely believe removing the mufflers could do it. As an experiment, this weekend I can pull my mufflers and go for a drive on 10psi setting and see what happens. Fwiw I didn't see a big gain going from 57/62 to 62/65. Made a little more power, but much less than I expected. If nothing else I hope these Precisions are more durable than the Turbonetics, and not have to rebuild them every couple years.

Chris Stewart

Test is done, and not the results I expected. Turned my controller all the way down. With full exhaust it made 11.8psi. (It's ~40 degrees out) With mufflers removed it made 11.2psi. This is 2.5" pipes and no cats. Apparently I was wrong and that 3" exhaust makes a big difference!

Turbo-Geist

Any details on the 427 combo? What is the max power it has made on its highest setting? What kind of control range does it have? Is there a restrictor in the inlet? Links to the build?

You made the same power at 3 psi less with the 62/65 compared to the 57/62 and IATs were lower. You were almost maxing out the 57/62s and this is why they didn't last very long. Your combo hasn't even scratched the surface of what the 62/65s are capable of producing. 880 rwhp on a 347 is roughly 46 lb/min of airflow each. These things are very capable of making > 60lb/min each on your combo. It will take 30 psi, but you won't get there on the 2.5" setup. It's too great of a restriction.

Turbo-Geist

I'm not surprised. On this full 2.5" exhaust system the restriction isn't largely at the mufflers. I just went and measured the I.D. of my old down pipes. They are 2.25" ID. Dual 2-1/4" exhaust on a high performance twin turbo V8? I wonder what the back pressure is in your housing and the measured resistance at the turbine wheel?

You would be amazed at what you are missing out on by sticking with the 2-1/4" down pipes.

Chris Stewart

Well at least we got one more data point for the puzzle. I was thinking the limitation could be the B covers. Another idea is to fit E covers like highpockets. I don't know if he ever fully tested it though. To make a big jump in power, that's why I was looking into the new Huron kit with full T4's and S covers. Since mine did 1000 with A4, and the highest I've seen anyone make on the C6 forum in the 1100's, figure I'm not missing too much.

Mookie TTix build. No restrictors, he has run it from 10-21psi for 1020hp.
https://www.corvetteforum.com/forums...tix-build.html

JDS99

I want to say the guy that bought highpockets kit modified for E covers was installed by Lethal Performance. Blue car? There is a thread in here where he made almost 1300? Grasping at straws here with a rum and coke in hand. Not good at searching on my phone.

I agree, Ben. Then 3" makes it a more efficient system and there's not much way around that, as I know you know. Without any overthinking, it's just pressure differential. The more you increase pressure pre turbo, and decrease it post turbo, the faster the turbo is going to work.

Just sell it and let's build you a new kit (after you go run an 8)

JDS99

Looks like my phone knows what I was looking for

https://www.corvetteforum.com/forums...e-build-3.html

Turbo-Geist

Thanks, Jon. Time to extract some numbers from this build. I'm going to try and finalize the tune on the street tomorrow and if all goes well hit the track in early December. If the clutch is still holding (fingers crossed) I'll get on a dyno for final stats.

Turbo-Geist

More tuning this past weekend. It's now holding 20.5 psi all the way to 6500 rpm in 4th gear. I'm really enjoying this 427 TT combo now that things are getting lined out.

I activated the boost controller for a test and saw 20.5 psi at 4500 rpm but had to let out. It was way too much power too early for the 18" drag radials. The car was all over the road. I'm looking forward to getting on a track with the Hoosier slicks soon.

ajrothm

You on E85 or still pump/meth?

I can't wait to see you dyno it..

Turbo-Geist

Pump/meth; just turned the meth on this weekend. Only 12 degrees of timing currently. This combo seems to be very tolerant from a forced induction/pump gas standpoint. I've also splashed in 5 gallons of MS109 a couple of times for safety. I've got 50 "free" gallons left and then it will be back to 93 and meth.

I may try E85 out at some point, but we only have a couple of stations in the area. I'm not planning to install a sensor anytime soon unless someone comes up with a good way to make it work and also unsure if I have enough fuel system for it currently.

If the clutch holds up this weekend, I may try and find a place to make a couple of pulls just to get an idea of what kind of power it makes.

schpenxel

I don't think gen 3 ECM's have any kind of flex fuel sensor input do they?

5 Liter Eater

Not to my knowledge.

Turbo-Geist

I think you are both right. It looks like Vengeance has figured it out on at least one vehicle, but not sure what it took. For the way I like to use the vehicle, it just doesn't make sense right now. Going with a full Pro-Efi setup would make it more feasible, but I'm not interested in going that direction either. The car is operating just fine now.

schpenxel

I think I remember reading about them swapping out the ECM for some specific model that supported it, but of course details were not given out

Had this bookmarked
http://ls1tech.com/forums/pcm-diagno...-write-up.html

JDS99

Glad you're out enjoying the car again, Ben. Hopefully that clutch hangs on for a little but longer!

StealthFRC

my car is a blast on 14psi, i couldn't imagine going right to 20+

inspector12

LOL! See I told you it was usable and a blast. You just have to keep working on it to find your sweet spot! Congrats!!!

Turbo-Geist

Agree, it's very enjoyable and the engine seems to be solid. Now I'm going to explore the limits of the drivetrain on slicks this weekend if the weather holds.

This wasn't the original plan but I've managed to make it work. With a 6 psi spring in the gates and the controller off, it is very predictable with a ramp to 20 psi. It's almost like being on a progressive with two kits, one small and one large. However, it's a handful on the street with the controller on and 20 psi very early.

Thanks, you were right. It still needs a few tweaks but everything is working out. I think I may still need a different tire for the street to maximize the potential.