precision 76gts?????
10-05-2005, 10:31 AM
#21
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I would have to agree with JET and EngineerMike, the air consumption of the engine making 1000HP is very similar to a smaller on making the same power, given the same AFR and similar BSFC's. This tells me that a given turbo will make a given amount of power (ROUGHLY), reguardless of displacement. Obviously you will need to set the hot side up correctly with the proper A/R and wheel, but the compressor should be able to stay the same. I am nearly finished with the stroker engine I have been putting together for myself, and we shal see what the GT76 Qtrim with a .96 A/R will do, I may have to step up the A/R even more though as I am running a .80 on the stock engine now with good results, but we will see. I have been told the GT76 will support 1000 hp and I intend on getting as much as I can out of it! I will let you all know how it goes.
-Bryan
-Bryan
10-05-2005, 11:13 AM
#22
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Guess compressor maps are worthless then eh...lol?? What happens to the pressure ratios.....are we just going to neglect those?? Does the efficiency of the compressor itself not matter....lol. You are neglecting the essential part of the compressor wheel and that is efficient compression of air vs the outlet pressure. Also backpressure will play a role as well. You have to distribute it over the cylinders since its a counter force. Mike I believe you yourself elaborated on this at one point as well. And it also is a valid point.
I would love to see a big cube 400+ ci LS1 with T3/T4 turbos. It has been done....will make power, but at the sacrifice of huge exhaust backpressure (2.5 to 3:1). Kills power, glowing headers, reversion in cylinders, lifting heads...etc..etc.
Jose
I would love to see a big cube 400+ ci LS1 with T3/T4 turbos. It has been done....will make power, but at the sacrifice of huge exhaust backpressure (2.5 to 3:1). Kills power, glowing headers, reversion in cylinders, lifting heads...etc..etc.
Jose
10-05-2005, 11:33 AM
#23
This thread has me ROFLing.
I reject your reality and substitute my own in it's place.
Go grab some of the VE charts off of forcedinductions.com for a 408 and a 346 and start doing some plots on the compressor maps for a 76. Won't be exact but will get you in the ball park. Also gives a nice visual representation of what is happening.
My motor has followed the calculations very closely on both my 67 and my 76.
I reject your reality and substitute my own in it's place.
Go grab some of the VE charts off of forcedinductions.com for a 408 and a 346 and start doing some plots on the compressor maps for a 76. Won't be exact but will get you in the ball park. Also gives a nice visual representation of what is happening.
My motor has followed the calculations very closely on both my 67 and my 76.
10-05-2005, 12:47 PM
#24
Jose when i go to your website and look at the compressor map for the T76 its just a generic T76...does it make a difference or affect how the graph would look having a Q or S trim?ie i know the S trim is supposed to handle more but are the compressor maps the same for all T76's?
10-05-2005, 01:21 PM
#25
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It will shift it somewhat but not by much. You may see an additional 10-15 lbs/min more of air. Which is where the rating from the PTE was based on. They have never been offcially tested on a TC-test stand under J1826 standards though. Hence why their is no compressor map for those units.
Jose
Jose
10-05-2005, 04:44 PM
#31
Jose, you're right, I had a good explanation about a larger cid engine having to work harder against the same backpressure, but have since convinced myself that that's not the case. A larger engine will ingest more air, thus make more power, for any given amount of boost. This offsets any added pumping losses.
The only explanation I can buy is that the same turbo on a large engine will run at a lower pressure ratio, perhaps in a less efficient spot on the map. This would further heat the boost, and require more work from the turbine (higher backpressure). However, we're talking a few percentage points in efficiency, not the hundreds of horsepower that people perceive the difference to be.
The only explanation I can buy is that the same turbo on a large engine will run at a lower pressure ratio, perhaps in a less efficient spot on the map. This would further heat the boost, and require more work from the turbine (higher backpressure). However, we're talking a few percentage points in efficiency, not the hundreds of horsepower that people perceive the difference to be.
10-05-2005, 04:57 PM
#32
looking at the base T76 map on Jose's site a 383 @15#s is barely on the map with about 88lbs/min of air....whereas a T88 on that same 383 would be at 78% efficiency.obviously the T88 would make more power efficiently but for a streetcar the lag wouldnt make it as much fun.whats the conversion for cfms to lbs/min?
10-05-2005, 06:33 PM
#34
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Originally Posted by JZ 97 SS 1500
It will shift it somewhat but not by much. You may see an additional 10-15 lbs/min more of air. Which is where the rating from the PTE was based on. They have never been offcially tested on a TC-test stand under J1826 standards though. Hence why their is no compressor map for those units.
Jose
Jose
Also note the native housing part. There are a lot of wheels that get put into non-native housings and that will change their efficiency. A prime example is the 56 trim GT35 wheel that is used in many turbo's.
10-05-2005, 09:14 PM
#35
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Originally Posted by JETmn
I need a little clarification. How does changing the exhaust wheel change the COMPRESSOR map at all? Compressor maps are for a compressor wheel in its native housing and has nothing to do with the turbine wheel/housing.
Also note the native housing part. There are a lot of wheels that get put into non-native housings and that will change their efficiency. A prime example is the 56 trim GT35 wheel that is used in many turbo's.
Also note the native housing part. There are a lot of wheels that get put into non-native housings and that will change their efficiency. A prime example is the 56 trim GT35 wheel that is used in many turbo's.
.Yes compressor cover A/R's change the flow output, turbine wheel design, and turbine housing size is also a factor. Same reason why Kyle asked about the 76GTS vs GT42-76. Kyle the GT42-76 is kind of up in the air. No one has flowed the 76mm version on a test stand so its hard to say. I dare say it will flow another 10lbs/min over the 76GTS. Also we have a new GT42 coming out VERY soon. Should flow quite a bit more, and it will be larger then a 76
Jose
10-05-2005, 10:07 PM
#36
Originally Posted by JZ 97 SS 1500
Read SAE J1826 standards, then come back....it will explain alot, if you need a copy let us know. My question to you is, how do you flow a compressor wheel without a turbine wheel? You going to spin it at the end of your finger .
Yes compressor cover A/R's change the flow output, turbine wheel design, and turbine housing size is also a factor. Same reason why Kyle asked about the 76GTS vs GT42-76. Kyle the GT42-76 is kind of up in the air. No one has flowed the 76mm version on a test stand so its hard to say. I dare say it will flow another 10lbs/min over the 76GTS. Also we have a new GT42 coming out VERY soon. Should flow quite a bit more, and it will be larger then a 76
Jose
.Yes compressor cover A/R's change the flow output, turbine wheel design, and turbine housing size is also a factor. Same reason why Kyle asked about the 76GTS vs GT42-76. Kyle the GT42-76 is kind of up in the air. No one has flowed the 76mm version on a test stand so its hard to say. I dare say it will flow another 10lbs/min over the 76GTS. Also we have a new GT42 coming out VERY soon. Should flow quite a bit more, and it will be larger then a 76
Jose
Thank you Jose...... I know when me and Stenod were talking to Precision they were saying it should go real well with my 370ci.
When will your new wheels be ready and what all will have to be done to mine to work with it?? If you can PM about how much its going to run.... It awsome to have a option if i ever Max out this turbo...
Kyle
10-05-2005, 11:07 PM
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Originally Posted by engineermike
Jose, you're right, I had a good explanation about a larger cid engine having to work harder against the same backpressure, but have since convinced myself that that's not the case. A larger engine will ingest more air, thus make more power, for any given amount of boost. This offsets any added pumping losses.
The only explanation I can buy is that the same turbo on a large engine will run at a lower pressure ratio, perhaps in a less efficient spot on the map. This would further heat the boost, and require more work from the turbine (higher backpressure). However, we're talking a few percentage points in efficiency, not the hundreds of horsepower that people perceive the difference to be.
The only explanation I can buy is that the same turbo on a large engine will run at a lower pressure ratio, perhaps in a less efficient spot on the map. This would further heat the boost, and require more work from the turbine (higher backpressure). However, we're talking a few percentage points in efficiency, not the hundreds of horsepower that people perceive the difference to be.
I substitute your books for my real word experience.