[wdodge45]

Hi Robert, I'm still waiting for a call back from Tatum but in the mean time ran across this with concerns.
Guy posted selling his GT-K 650's with .86ar's on a turbo built LSX 434 motor due to the turbos ran out of gas at 20psi at 4800rpm on this street driven 2007 corvette....
With that being said, I'm feeling a little nervous! Here we are hooking up 38" paddle tires in the sand with a car weight of 2700# and I run this motor to 7200rpm.
The guy is changing to ur 76 series size...
Any thought or concerns but hopefully u can see my questions before I buy.....

Bill

[Robert]

Originally Posted by wdodge45

Hi Robert, I'm still waiting for a call back from Tatum but in the mean time ran across this with concerns.
Guy posted selling his GT-K 650's with .86ar's on a turbo built LSX 434 motor due to the turbos ran out of gas at 20psi at 4800rpm on this street driven 2007 corvette....
With that being said, I'm feeling a little nervous! Here we are hooking up 38" paddle tires in the sand with a car weight of 2700# and I run this motor to 7200rpm.
The guy is changing to ur 76 series size...
Any thought or concerns but hopefully u can see my questions before I buy.....

Bill

Well as you said before you had to switch to larger turbine housings to keep the boost curve good at the top end and make the top end power without backpressure issue. I don't see any info from that car on what his power goals were or any other limitations. The HP66 compressor is used in a lot of SINGLE turbo kits on LS series motors and for people who do want more power they switch to an HP76 but thats in a single turbo config. Bottom line I don't think there is anything to worry about. Did you look at Ash's post that I linked on the last page? He's running an SBC as well with HP66 compressor wheels and running 6s in the 1/4 mile with little to no lag. Here's a video:

YouTube - willowbank winternationals 2009, twin turbo altered

YouTube - twin turbo sbc altered , willowbank 2009

You might even want to shoot Ash a PM. He's tried a variety of different units on his car (the one in the video) and settles on HP66 compressors. If you want you could always step up to the GT-K 850 or 1000. The GT-K 850 uses an HP72 compressor and the GT-K 1000 uses an HP76 compressor. They also uses a larger F1-68 turbine wheel. The F1-65 will spool up faster (because of size) than the F1-68 turbine wheel but the F1-68 will of course be able to handle even more power. At that point though we are talking in the 2000+ HP range. I still think the GT-K 650s will be great for you. Keep in mind we are already talking about a turbo that is significantly larger than the 60-1 compressors you were just using even with the GT-K 650.

[wdodge45]

Ok Robert,
I had some time this weekend to do a little research and of course have a few more questions arise. I saw a lot of motors Nelson Racing Engines is doing and advertizing. One is his daily driver 402 twin turbo and he runs twin 72mm turbos and states 1100hp pump gas and 1600hp race fuel. The only twins running below that are smaller cu in daily driver with twin 60-1s. His hardcore and race stuff with 427 and 454 's are 76mm and 88mm for racing. With that being said and the other build on the corvette with only making 1220 with the GT-K 650's I'm really considering the HP72 or the GT-K 850 unless you tell me otherwise. I have to believe Nelson has done his homework and builds some increadible engines for both street driving and racing and has it figured out which turbos work with these vastly different type of cars.
I only want to do this once since I'm eating these hardly used 60-1 turbos and want the hp increase and driveablity. Since Nelson uses your turbos, would you know what he uses for AR ratios on the 72mm daily driver motors and do you think I'm going to far or making a mistake going past the GT-K 650's.
I really value your expertise and read almost all your treads posted so I'm looking for the best case here and don't want to get carried away in what I think I want because thats all it is, just my guess. My goal is running 10psi on low boost and making roughly 1500hp on high boost without going past 18psi, what turbo setup will do this the best.....what turbo setup will flow and do well without running higher boost numbers? I know alot of turbos only start to shine when boost increases, I just dont have that luxury with the C5R 4 bolt per cyl. heads.
Thanks,
Bill

[Robert]

Originally Posted by wdodge45

Ok Robert,
I had some time this weekend to do a little research and of course have a few more questions arise. I saw a lot of motors Nelson Racing Engines is doing and advertizing. One is his daily driver 402 twin turbo and he runs twin 72mm turbos and states 1100hp pump gas and 1600hp race fuel. The only twins running below that are smaller cu in daily driver with twin 60-1s. His hardcore and race stuff with 427 and 454 's are 76mm and 88mm for racing. With that being said and the other build on the corvette with only making 1220 with the GT-K 650's I'm really considering the HP72 or the GT-K 850 unless you tell me otherwise. I have to believe Nelson has done his homework and builds some increadible engines for both street driving and racing and has it figured out which turbos work with these vastly different type of cars.
I only want to do this once since I'm eating these hardly used 60-1 turbos and want the hp increase and driveablity. Since Nelson uses your turbos, would you know what he uses for AR ratios on the 72mm daily driver motors and do you think I'm going to far or making a mistake gong past the GT-K 650's.
I really value your expertise and read almost all your treads posted so I'm looking for the best case here and don't want to get carried away in what I think I want because thats all it is, just my guess. My goal is running 10psi on low boost and making roughly 1500hp on high boost without going past 18psi, what turbo setup will do this the best.....what turbo setup will flow and do well without running higher boost numbers? I know alot of turbos only start to shine when boost increases, I just dont have that luxury with the C5R 4 bolt per cyl. heads.
Thanks,
Bill

Bill,
72mm compressors will certainly do the trick. The GT-K 850 will work for that set up too. Strictly technically speaking the 650s will work. But I completely understand your position. Money doesn't grow on trees and the technical side really only proves itself out when you can test several configurations on your motor and determine the best set up for your car in the real world on the dyno. The GT-K 850 will definitely work for you no doubt. A/R wise I don't think you are going to need to run a 1.30 with the 850. It uses an even larger
T4 turbine wheel than the GT-K 650. The GT-K 850 uses a 68mm turbine where as the 650 uses a 65mm turbine. I double checked with a couple engineers at Turbonetics and they agree that with the larger F1-68 turbine wheel on the GT-K 850 the .96 A/R turbine housing is the way to go.

[wdodge45]

Thanks Robert....and do you honestly feel that I can run low boost numbers and achieve my goals and spool time compared to the 60-1/62-1 will be somewhat decent, as I realize with both wheels being larger spool time will be slower but not to the point of driveablity issues?
Thanks,
Bill

[Robert]

Originally Posted by wdodge45

Thanks Robert....and do you honestly feel that I can run low boost numbers and achieve my goals and spool time compared to the 60-1/62-1 will be somewhat decent, as I realize with both wheels being larger spool time will be slower but not to the point of driveablity issues?
Thanks,
Bill

By going down on the A/R of the turbine housing you should be able to keep your spool time where you need it. I think you should be fine meeting your goals with the 850 provided you step down to the .96 A/R. The 1.30 A/R is going to be too big with the larger turbine wheel. I think you are safe to pull the trigger on these.

[wdodge45]

Hey Robert.....sounds great and thanks so much for all the work and patients you have had.....It has helped me tremendously and I really mean that. All I would be doing would be shooting in the dark without your help, thanks again....
Bill

[Robert]

Originally Posted by wdodge45

Hey Robert.....sounds great and thanks so much for all the work and patients you have had.....It has helped me tremendously and I really mean that. All I would be doing would be shooting in the dark without your help, thanks again....
Bill

Bill,
I'm happy to help out however I can! I can't wait to see your videos and pictures and hear how you like the new turbos!

[wdodge45]

Hi Robert,
Decisions decisions....well I'm having a hard time justifing the cost on the GT-K 850's so what options do I have for more reasonable turbos??? T-70 or T-72's ball bearing big shaft or anything else here.
Looked at a lot of other turbo mfg. and I keep coming back to turbonetics, so please let me know what my options are in some other turbos with on center housing that will work for my application.
Thanks,
Bill

[Robert]

Originally Posted by wdodge45

Hi Robert,
Decisions decisions....well I'm having a hard time justifing the cost on the GT-K 850's so what options do I have for more reasonable turbos??? T-70 or T-72's ball bearing big shaft or anything else here.
Looked at a lot of other turbo mfg. and I keep coming back to turbonetics, so please let me know what my options are in some other turbos with on center housing that will work for my application.
Thanks,
Bill

Bill,
You could certainly go with straight up T72s with F1-68 turbines and on center housings. Those should be more reasonable. There's also the TN Series which is a lower cost unit (no polished compressor housing) that still has all the technology minus the ported compressor shroud. Something like the TN800-BB would work.

Heres a link to the TN Series:

TN Series Turbochargers | www.TurboneticsInc.com - Boosting Since 1978 | turbochargers, intercoolers, wastegates, blow-off valves, controls, boosting systems, turbo kits, forced induction parts & accessories


So you could either do the TN Series TN800-BB which is a lower cost unit with the same performance and technology and a little less show. Or you could do straight up T-Series HP72s with F1-68 turbine wheels oncenter. You can think of the TN Series as a regular T72 without a polished compressor cover.