ct26 max psi

[3.0 GT]

i was reading about shimming the wastegate on the stock ct26 and it says that if you put about 1.5cm of washers between the wastegate and where it bolts on you can get about 10.7 psi of boost. but what i want to know is what would be a safe psi on a fresh rebuilt 7mgte with new bearings everywhere, new pistons, all gaskets, and new stock headgasket tourqed to 72ft/lbs. (no ARP's)

 

[noah89t]

don't waste your time with that. just save up and get a good electronic boost controller.

 

[Doward]

~12psi on a 100% bone stock motor.

 

[tissimo]

~12psi on a 100% bone stock motor.

rubbish. 20+ psi on a 95% stock engine (upgraded headstuds/Bolts at least) would be fine. (given of course all the supporting requirements are there).

 

[lewis15498]

rubbish. 20+ psi on a 95% stock engine (upgraded headstuds/Bolts at least) would be fine. (given of course all the supporting requirements are there).

the title of this thread is ct26 max psi. Last time i checked a stock ct26 isnt capable of 20psi without cooking it.

 

[TurboFreak]

i'd say around 12-15psi. I cooked mine at around 15-16psi.

 

[tissimo]

the title of this thread is ct26 max psi. Last time i checked a stock ct26 isnt capable of 20psi without cooking it.

It is capable of it though, and thats what the question is.

 

[Doward]

The question wasn't what the maximum pressure the ct26 is capable of -

but what i want to know is what would be a safe psi on a fresh rebuilt 7mgte with new bearings everywhere, new pistons, all gaskets, and new stock headgasket tourqed to 72ft/lbs. (no ARP's)

~12psi

 

[figgie]

It is capable of it though, and thats what the question is.

in what reality?

On the 7m it will NEVER get to 20 psi. No fucking way. The 7m is already out breathing the ct26 at 14psi. as it goes down to 12 psi by 6500 rpm redline.

 

[tissimo]

The question wasn't what the maximum pressure the ct26 is capable of -



~12psi

No, 20+. I dont see why the engine couldn't handle it given all the other requirements are met.

in what reality?

On the 7m it will NEVER get to 20 psi. No fucking way. The 7m is already out breathing the ct26 at 14psi. as it goes down to 12 psi by 6500 rpm redline.

This reality. It has been done. Boost of course will fall off and its pushing the turbo FAR beyond its efficiency island.

 

[SupaMan]

i read somewhere (cant remember if it was here or not) that anything above 15psi it was just blowing hot air.





but what would i know im just n/a HAAAAAAAAAAAAAAAAAAAAAAA!

 

[Doward]

Tissimo, trust me on this - 20psi is beyond inefficient on the CT26. Maybe a 60-1 wheel would do it, but the exhaust side would still be hampering you.

You may have hit 20psi once - but no engineer in their right mind is going to suggest running so far outside normal operating parameters.

You can do ~12psi reliably, efficiently, and all day every day on the stock CT26.

 

[Keros]

I'm not claiming to know anything... but I do notice that on my CT26, the car will pull pretty hard, at WOT, from 3000-5000rpm @ ~14psi, and start to decline at about 5500-6500rpm... basically like it's spinning faster but not really producing the good accelleration compared to the previous 2000rpm of powerband.

I think this is the practical example of IJ's comment about the CT26 "running out of breath". Yes, the turbine can produce 20psi of pressure, but it cannot flow enough air for a 7M to make power above 15psi at higher rpm (where more air is required), as noted above. Horsepower is made by air flow volume (cubic feet per minute), not air flow pressure (pounds per square inch).

 

[tissimo]

Maybe I read the question differently then it was intended. I assumed he was talking about safe boost for his engine. In that case 20+ psi given the he has the requirements to do so. As for max safe boost for his turbo, I would say 15-16 psi is fine. Of course dont expect it to last forever as you're taking a 15+ year old turbo that has lots of mileage on it, and running it near/at full tilt.

 

[figgie]

Maybe I read the question differently then it was intended. I assumed he was talking about safe boost for his engine. In that case 20+ psi given the he has the requirements to do so. As for max safe boost for his turbo, I would say 15-16 psi is fine. Of course dont expect it to last forever as you're taking a 15+ year old turbo that has lots of mileage on it, and running it near/at full tilt.

even if it was brand new. It would not last as you are overspinning the turbo. 20 psi on a stock ct26.. lmfao. To give you an idea.

20 psi on the 7m equals to roughly about 500hp. So according to you. The ct26 can spike to that much power. I am here to tell you, that you are full of shit. Turbos do not magically defy physics.

 

[tissimo]

even if it was brand new. It would not last as you are overspinning the turbo. 20 psi on a stock ct26.. lmfao. To give you an idea.

20 psi on the 7m equals to roughly about 500hp. So according to you. The ct26 can spike to that much power. I am here to tell you, that you are full of shit. Turbos do not magically defy physics.

wow, 20psi = 500hp. awesome! :nono:

Figgie: Sorry... meant to reply not edit.

 

[figgie]

wow, 20psi = 500hp. awesome! :nono:

Figgie: Sorry... meant to reply not edit.

And indeed 20psi on a EFFICENT turbo will infact be that much.

indeed! in the 7m is even worse because of craptacular inefficent VE of the head which are floating around 65% at 6500 RPM from some preliminary data.

See here is some facts based on fluid mechanics and physics
Intake pressure are infact created equal. What distinguishes intake pressure from one motor over the other is the displacement of the engine NOT the turbo. All the turbo does is deliver a set amount of air volume at a given efficency into the motor. To get to 500HP with a petrol/Gasoline AFR of 11.6 takes roughly about 48 lbs/min worth of air WHETHER it is forced induction or Natural Aspirated. This is irrelevant of the engine displacement. What the displacement will effect is the intake plenum pressure, and specifically the relation is as the engine displacement increases, the intake plenum pressure at the same given power DECREASES. So 500hp on a 2.0 4g63 is going to be a heck of a lot higher than a 3.0 7m, which will inturn be higher than a 302. Add to that head inefficeny and it compounds the problem more so.

Any other questions?

 

[tissimo]

indeed! in the 7m is even worse because of craptacular inefficent VE of the head which are floating around 65% at 6500 RPM from some preliminary data.

See here is some facts based on fluid mechanics and physics
Intake pressure are infact created equal. What distinguishes intake pressure from one motor over the other is the displacement of the engine NOT the turbo. All the turbo does is deliver a set amount of air volume at a given efficency into the motor. To get to 500HP with a petrol/Gasoline AFR of 11.6 takes roughly about 48 lbs/min worth of air WHETHER it is forced induction or Natural Aspirated. This is irrelevant of the engine displacement. What the displacement will effect is the intake plenum pressure, and specifically the relation is as the engine displacement increases, the intake plenum pressure at the same given power DECREASES. So 500hp on a 2.0 4g63 is going to be a heck of a lot higher than a 3.0 7m, which will inturn be higher than a 302. Add to that head inefficeny and it compounds the problem more so.

Any other questions?

Too bad pressure != flow. But thanks for playing.

 

[figgie]

Too bad pressure != flow. But thanks for playing.

this is going to be fun!!

unfortunatly for you, pressure IS infact, closely related to flow. The exact reason why the CT26 falls flat on its face from a intake pressure point at the upper end of the RPM scale. The reason it is related to pressure because unlike a true turbine engine, The internal combustion engine creates pulse when the valves are closed which coincidentally happen to be where the valves are most of the time except for when they open to allow the cylinder to injest air. So when the valves are closed, Resistance to the flow is present and as such pressure and flow are related If the turbo can not keep up, like the aforementioned ct26... you have a reduction in pressure as the engine injest more air than the turbo can flow.

any other asumptions on your part? You best better brush up on your fluid mechanics if you are going to tackle this subject because you will not win.

 

[LilMissMkIII]

Not wanting to get involved in the discussion between Figgie and Tissimo, but to the OP and a few others, My car has all the bolt-on mods to support an upgraded turbo (injecors, fuel pump, mapecu2, custom intale, brand new upgraded cooling system etc etc etc), and when I dynoed with the stock CT26, we couldn't/wouldn't/didn't push it above 13psi, because it just fell on it's face.

13psi on stock turbo + all relevant bolt on mods = 300hp at the wheels (for me).