76GTQ vs 71HPQ billet

[forcefed3.8's]

My turbine wheel is damaged on my 76GTQ. The inside of the wheel is broken/melted. I pulled the wheel out from the DP side of the housing. I don't know when it happened, I had a lean 1/8 mile run, but no melted plug or anything else to show melt down lean, and the turbo showed no spool up difference. The car went 1.52 off 7psi on the lean run, and 1.48 off 8psi 4 months later. Should I get it rebuilt with an HPQ wheel, buy a billet 71HPQ, or buy a 70HPQ? So far I have run 10.20@134 with 21psi and 18deg timing, letting it shift at 5100. I know the rpm's are nowhere near what the turbo and 224 cam want to see. I plan on 6200 shifts this year, and hopefully getting the boost north of 25psi.

I am running a 0 pump Vigilante that stalls just shy of 3000. I was wanting to get a PTC this spring, but now it might not happen. I am guessing spool up can't be any worse with the other mentioned turbos. It wasn't too bad with the 76! What should I do? TIA

 

[Darkcyde]

What should I do? TIA

post a video! lol

 

[SGRIM]

I would think the 71 billet would make close to the same power as the old 76 and spool quicker... That 71 will last past your 109 blocks power capability IMO so that is the way I would go, especially with the costs of rebuilds...

 

[forcefed3.8's]

I was leaning towards the 71 myself. I am worried about boost control issues with a THDP. Is there reason to be concerned?

 

[WSLN 6]

What size is your downpipe puck? I had a Mease 3" pipe that had a 1.44" puck in it that controlled boost well.

 

[SGRIM]

I was leaning towards the 71 myself. I am worried about boost control issues with a THDP. Is there reason to be concerned?

Yes, IMO... At that power level that turn is a problem... Stepping up to such a turbo I would personally consider the external gate option, much more control which is going to be needed with a billet turbo... I am no expert, just IMO

 

[forcefed3.8's]

The puck is 1.375. I keep hearing about issues with the billet wheel turbos and stock style actuators controling low boost. Boost was rock steady with the 76, and the wastegate hole was untouched, the way the housing came from Precision.

 

[forcefed3.8's]

Yes, IMO... At that power level that turn is a problem... Stepping up to such a turbo I would personally consider the external gate option, much more control which is going to be needed with a billet turbo... I am no expert, just IMO

Where is the problem, low boost? How about the 1.625 puck RJC sells? I never cared for external gates, mostly because I never had issues with the stock set up. I am not totally opposed to the idea, just more $$$.

 

[SGRIM]

The puck is 1.375. I keep hearing about issues with the billet wheel turbos and stock style actuators controling low boost. Boost was rock steady with the 76, and the wastegate hole was untouched, the way the housing came from Precision.

These turbos like to run at 28+psi to really see them shine... I hope RJC's puck may fix the issue. It is the best alternative that is for sure...

I guess it would depend on your ultimate goal. If you are looking max power on all levels just look how the heavy hitters do it in TSM...

Along with that puck you got to have a solid controller...

 

[bison]

If your going external then just go 4 bolt tangential or just have your GTQ repaired. You have a lot more room to go on the GTQ if you can keep the wastegate from pushing open.

 

[forcefed3.8's]

I am planning on getting headers for the car, maybe now is the time to go 4 bolt? I am going to call Precision to see how much fixing it will cost. Would it be worth going to an HPQ wheel?
Here are some pics of the wheel:

 

[turbogray]

i had a gtq70 that went lean on a run and looked just like that after

 

[Sam Colalillo]

Here is my opinion.

It depends on your budget; if money is tight just get the 76 repaired.

I am making the assumption you want to hit the 9’s. The 76 should get you there, but I think it would be easier on your engine with a different turbo.

Based up on the equipment you have listed in your signature I would recommend the 71 HPQ billet turbo with dual ball bearings. I wouldn’t tell you to switch to a 4 bolt turbo either. Stay with the headers you have if they are in good shape. TSM has proven the 3 bolt turbo gets these engines into the 9’s no problem.

I was running a 70 HPQ dual ball bearing turbo last year on our TSM car. Based up on several things, including logging back pressure I don’t feel I maxed it out. The 71 billet is newer technology than what I was running. In my opinion the 71 is going to spool up faster than your 76 did and send you sailing down the track faster in the front half. You are so close to the nines, and if your fuel pump can keep up this turbo should get you there with plenty of room to grow. I also think this 71 billet wheel will be able to make comparable boost numbers that your 76 did.

I made a visit to Precision Turbo last week and got to spend some time with Dan Barlog the engineer at Precession turbo. The technology on the new turbo they have developed is really awesome. The new dual ball bearing cartridge they are using resists up to 40% higher temperatures than the previous Garret cartridge. Several new housing which are being cast in the USA are being developed to increase performance. Dan is using a fluid dynamics software package (really awesome stuff, I use the same base software package at my job) to help him design the new wheels and housing they are making. The research and development that is going into these new turbo for performance applications is incredible. I looked at several of the old wheels and compared them to the billet wheels and it is easy to see how this billet stuff will be able to move more air.

In regards to over boosting I cannot accurately say. I run an external gate on our car. I do think you have a chance making the internal gate work if you port match the puck to the turbo housing. Like I said, this is just my opinion. Good luck with your ride.

 

[forcefed3.8's]

I was thinking the 71 would be stronger in the first half. I think my car is weak there because of the low shift point too. The car would have hit 9's at 25psi, but my second fuel pump wasn't kicking on, and I let out, then had tranny problems, so couldn't run again that day. The 10.20 was only at 21psi, because that is all it would make, possibly from the burnt wheel, or I think I hurt a head gasket on that 25psi run, and it finally showed itself trying to turn up the boost. I know the 76 will do more than I need it to, it has been deep in the 9's@147+ on a friends car. My headers are stock cut apart, ported, welded around the ports. I think they are cracked again. I want a set of TA's. I am on the fence if headers are even worth anything in a 3 bolt application. I have only made 6 passes with this combo. I was wondering if the smaller 70gtq/hpq turbo would run better in the rpm and boost range I am going to run.

 

[bison]

I am planning on getting headers for the car, maybe now is the time to go 4 bolt? I am going to call Precision to see how much fixing it will cost. Would it be worth going to an HPQ wheel?
Here are some pics of the wheel:

Id go 4 bolt and HPS not HPQ and BB. You will be able to pick up a lot of power at high rpm and at lower boost than the 3 bolt choking setup. What were your charge air temps vs. ambient with the 76 compressor? Im curious since ive never seen a datalog with an old tech 76 comp wheel. Cant imagine you were anywhere near maxing out that wheel. What was your eighth mph?

 

[forcefed3.8's]

It is nowhere near maxed out, this turbo has gone 150+ in a local GN. I had no way of logging inlet temp. With the GEN2 translator, the IAT doesn't display right. My 1/8 was 106@21psi, and 109@25psi running super lean. I am sure letting it shift at 5100 slowed down the first half alot.

 

[bison]

It is nowhere near maxed out, this turbo has gone 150+ in a local GN. I had no way of logging inlet temp. With the GEN2 translator, the IAT doesn't display right. My 1/8 was 106@21psi, and 109@25psi running super lean. I am sure letting it shift at 5100 slowed down the first half alot.

Id want that combo over 5500 all the time. Imo you converter should flash higher than 5100@25psi which would make it impossible for it to shift at 5100. What springs do you have? What is your gross lift? Id look at getting that converter adjusted or switching to a PTC 9.5" after you get a handle on what went wrong. A datalogging device is a must here.

 

[forcefed3.8's]

Gross lift is .598. I am running springs for a solid roller from Weber. They are 1.384 dia and came out to 165 seat and mid 400's open, I can't remember the exact number. The set up of the springs turned into a fiasco of it's own, with keepers and reatiners trying to get enough free travel and to get the installed height over 1.7. Then my rockers didn't clear, and this was all while I was moving, and had to get the car running in 1 month!(all while packing the rest of my junk) I guess it was doomed from the start.

I know at 21psi it is shifting at 5100, 25psi, I have no clue, I just put a tach in the car. I am using a borrowed ecm, so I don't have my powerlogger on it. My ECM wigged out. Once the car hit operating temp, it showed 6375rpm, so went on rev limiter at idle. Man, this car has been a nightmare, afew rocker arms came loose driving to work, balancer bolt came loose after first 1/8 mile run, governer spring came out after first 1/8 mile, 2nd fuel pump didn't come on during first 1/8mile run. It is all ironed out now, then I pulled the downpipe and saw this.

This summer I should actually have time to work on the car. I am trying to budget this. A 4 bolt turbo would be too much of an investment right now, between headers, DP, wastegate, controller, and then I would want a PTC on top of it. I liked the idea of the 71 because I am sure rebuilding the 76 is going to cost almost 1/2 of the 71. But if the 71 ends up needing an ext wastegate and controller, then I am half way to a 4 bolt. I totally agree on the 4 bolt though, I was going to run one from the start, then a friend offered me this turbo at a great price. I pretty much have his old TSE set up. Other than I am running a stroked 109, and have regular GN1's that I gave a mild clean up, everything else is the same, converter, trans, injectors, cam, etc.

 

[bison]

Gross lift is .598. I am running springs for a solid roller from Weber. They are 1.384 dia and came out to 165 seat and mid 400's open, I can't remember the exact number. The set up of the springs turned into a fiasco of it's own, with keepers and reatiners trying to get enough free travel and to get the installed height over 1.7. Then my rockers didn't clear, and this was all while I was moving, and had to get the car running in 1 month!(all while packing the rest of my junk) I guess it was doomed from the start.

I know at 21psi it is shifting at 5100, 25psi, I have no clue, I just put a tach in the car. I am using a borrowed ecm, so I don't have my powerlogger on it. My ECM wigged out. Once the car hit operating temp, it showed 6375rpm, so went on rev limiter at idle. Man, this car has been a nightmare, afew rocker arms came loose driving to work, balancer bolt came loose after first 1/8 mile run, governer spring came out after first 1/8 mile, 2nd fuel pump didn't come on during first 1/8mile run. It is all ironed out now, then I pulled the downpipe and saw this.

This summer I should actually have time to work on the car. I am trying to budget this. A 4 bolt turbo would be too much of an investment right now, between headers, DP, wastegate, controller, and then I would want a PTC on top of it. I liked the idea of the 71 because I am sure rebuilding the 76 is going to cost almost 1/2 of the 71. But if the 71 ends up needing an ext wastegate and controller, then I am half way to a 4 bolt. I totally agree on the 4 bolt though, I was going to run one from the start, then a friend offered me this turbo at a great price. I pretty much have his old TSE set up. Other than I am running a stroked 109, and have regular GN1's that I gave a mild clean up, everything else is the same, converter, trans, injectors, cam, etc.

Id get a set of 1.55 rockers and get that lift down some. I cant see any benefit to it and it is really working those springs hard. Your open pressures are barely adequate unless you are using a really mild custom profile and keeping the boost around 25 or less. If you plan on targeting 135+ with the 71 if you get it i doubt you will have the problems trying to control boost the others are when they try and run a 850hp turbo on a 500hp combo. You will be looking at running 25+ psi most likely and will have plenty power and ex pressure to help your wastegate open without opening the hole up much. PM me your cam specs if you want my input on the cam grind, springs and timing. Include the grind #'s. There is no point in spending $ here unless its going to help you be more reliable and or faster.

 

[forcefed3.8's]

Hey Bison, how can I get ahold of you?