Safe boost levels for -9 Equipped R34 GT-R

[NAB 8]

Safe boost levels for -9 Equipped R34 GT-R

Hey guys, 

I recently purchased a pair of GT2859R -9 turbos due to the stock ones having blade damage and needing a full rebuild. I was wondering since the new turbos provide more flow, what boost levels would be considered to be 'safe' on a completely stock RB26? I previously ran 1.00 bar on the stock turbos and the car seemed to run fine although I did notice the injector usage getting close and hitting 100% which makes me slightly concerned for the new turbos. Do you think the stock boost of 0.8 bar would be fine or possibly even less?

Cheers, Nick.

Edited June 27, 2017 by NAB 8
Changing format

[Hadouken]

3 bar

[No Crust Racing]

Compressor map shows 22-psi is about max efficiency.

https://turbochargerspecs.blogspot.com.au/2011/03/garrett-gt28r-gt2859r-56-trim-310-hp.html

Approx 2.5 Pressure ratio on the graph.

HOWEVER, people argue that the limiting factor to the turbo's longevity is actually the turbine flow/heat and as you can see from the graph, the turbine starts to choke before the compressor does. Choke = heat, heat = premature wear etc. 

So how hard you run them depends on the type of usage and your appetite for risk. 

20psi should be fairly "safe" on both fronts, but 22-24psi squirts are not going to hurt a healthy turbo in a street application. 

Other variables come into play here also, fuel type use? E85 has lower EGTs = happier turbo. Size of dumps and exhaust? Bigger = more flow, less backpressure and less work for the turbo. Etc etc. 

We ran out of fuel pressure on the dyno at 373kw at 20psi on -9s in my car so this week we should see if it will happily hold 20-22psi. Keep in mind this is with N1 manifolds, 3" dumps into 3.5" exhaust, E85 and Kelford L182A cams (springs and head studs for insurance) with pods (proven to make more power at this boost on the dyno) and a Plazmaman intercooler. 

To run 20psi+ on these turbos you will also need fuel pump, injectors, an ECU to make use of it all, and quite likely AFMs if you stick with those rather than going MAP (which would also mean needing a MAP sensor). 



 

[NAB 8]

10 minutes ago, ActionDan said:

Compressor map shows 22-psi is about max efficiency.

https://turbochargerspecs.blogspot.com.au/2011/03/garrett-gt28r-gt2859r-56-trim-310-hp.html

Approx 2.5 Pressure ratio on the graph.

HOWEVER, people argue that the limiting factor to the turbo's longevity is actually the turbine flow/heat and as you can see from the graph, the turbine starts to choke before the compressor does. Choke = heat, heat = premature wear etc. 

So how hard you run them depends on the type of usage and your appetite for risk. 

20psi should be fairly "safe" on both fronts, but 22-24psi squirts are not going to hurt a healthy turbo in a street application. 

Other variables come into play here also, fuel type use? E85 has lower EGTs = happier turbo. Size of dumps and exhaust? Bigger = more flow, less backpressure and less work for the turbo. Etc etc. 

We ran out of fuel pressure on the dyno at 373kw at 20psi on -9s in my car so this week we should see if it will happily hold 20-22psi. Keep in mind this is with N1 manifolds, 3" dumps into 3.5" exhaust, E85 and Kelford L182A cams (springs and head studs for insurance) with pods (proven to make more power at this boost on the dyno) and a Plazmaman intercooler. 

To run 20psi+ on these turbos you will also need fuel pump, injectors, an ECU to make use of it all, and quite likely AFMs if you stick with those rather than going MAP (which would also mean needing a MAP sensor). 



 

Cheers for the quick reply Dan, I appreciate the effort too. Yeah I plan on getting injectors, ECU and a fuel pump later down the line but I will definitely keep this in mind . In regards to running the -9 turbos on my current stock setup (stock injectors, pump etc), should running 0.8 bar be safe in terms of fitting within the stock injector's/pump's limits? even though it seems as if they were maxing out on the old stock turbos?

[No Crust Racing]

Remember PSI is just a pressure reading in the manifold and tells you nothing about the actual air flow being put out by the turbo/ingested by the engine. 

For safety sake, you will want to put it in a dyno at a bare minimum and not be getting into boost until you do.

Make sure the AFRs are safe. As -9s are a step up in size compared to stock, they flow characteristics are quite different. 

Usually, people do turbos with an ECU/injectors/pump etc as you can't make good use of the turbos otherwise. 

Are the current turbos actually stuffed? Minor chips in blades is not a big eal at low boost and could allow you to get the other bits together and do it all at once properly. 

 

[NAB 8]

4 hours ago, ActionDan said:

Remember PSI is just a pressure reading in the manifold and tells you nothing about the actual air flow being put out by the turbo/ingested by the engine. 

For safety sake, you will want to put it in a dyno at a bare minimum and not be getting into boost until you do.

Make sure the AFRs are safe. As -9s are a step up in size compared to stock, they flow characteristics are quite different. 

Usually, people do turbos with an ECU/injectors/pump etc as you can't make good use of the turbos otherwise. 

Are the current turbos actually stuffed? Minor chips in blades is not a big eal at low boost and could allow you to get the other bits together and do it all at once properly. 

 

Yeah the old ones are pretty far gone :/. I might just install the -9s then and keep the car off the road for a little longer until I can get injectors, ecu etc. Thank you for you help though