Roots or Turbo?
12-09-2012, 09:20 PM
#42
Safety Car
I found a good quote:
"Compare with the previous generation (Gen 5) Eaton superchargers, the TVS has many advantages. First of all, it can provide 20 percent higher air flow, hence higher boost and power; Secondly, it consumes less power at high rev. For example, the one on Corvette ZR1 consumes 75 horsepower at peak power, versus 115 hp on the Gen 5. "
http://www.autozine.org/technical_sc...duction_1.html
Someone correct me if my logic is not right. TVS has 70% efficiency, 10% less than the better turbos. So let's say GM picked turbo instead of TVS. Wouldn't the power gain be only 1/3 of 75hp? Aka, would it be just 25hp gain all things the same. That seems like an awful lot of headache for 25hp.
"Compare with the previous generation (Gen 5) Eaton superchargers, the TVS has many advantages. First of all, it can provide 20 percent higher air flow, hence higher boost and power; Secondly, it consumes less power at high rev. For example, the one on Corvette ZR1 consumes 75 horsepower at peak power, versus 115 hp on the Gen 5. "
http://www.autozine.org/technical_sc...duction_1.html
Someone correct me if my logic is not right. TVS has 70% efficiency, 10% less than the better turbos. So let's say GM picked turbo instead of TVS. Wouldn't the power gain be only 1/3 of 75hp? Aka, would it be just 25hp gain all things the same. That seems like an awful lot of headache for 25hp.
12-09-2012, 09:21 PM
#43
Team Owner
What I really want to know is what happens to an LT1 if I dump 100 octane in it at the nearby track?
I can live with 475hp car daily, and 575hp at the track. Any 335 section street tire will be the limitation at that point and I'm not ever planning on running slicks or special order Veyron Michelins.
I can live with 475hp car daily, and 575hp at the track. Any 335 section street tire will be the limitation at that point and I'm not ever planning on running slicks or special order Veyron Michelins.
12-09-2012, 09:29 PM
#44
Safety Car
It seems reasonable that GM could design the ECM to sense when you are WOT and the traction control isn't engaged, to keep bumping up the timing until it senses knock and then pull a little timing out of it. It could then maintain this until it then senses, at another time, that it is getting knock at that timing and then revert back to the timing tables designed for 92 octane. Just the opposite of what it does now on the C6.
Direct quote:
"The timing isn't excessive it moves -4 degrees or + 4 degrees range when running E-85. This allows for substantive power gains from a more violent combustion and dynamic cylinder pressure = more power. The VVT adds more duration at this time without the increase in EGT = More power on E-85.
And yes... this is speaking relative to the 2014 LT1 N/A form. A range of 40-80hp. Depending on ambient temperature outside. "
Last edited by SBC_and_a_stick; 12-09-2012 at 09:52 PM.
12-09-2012, 10:00 PM
#45
Team Owner
Bigg_gunz said people will be very satisfied with the official figures when the C7 will be announced. When someone asked whether 460-475 hp is reasonable to expect he nodded. Then he said E85 will give the LT1 an additional 40-80hp depending on the environment. He continued by saying it will do so by adjusting timing and duration through VVT with that wicked ECU. So if it can do that with E85 what can we deduce with 100 octane?
Direct quote:
"The timing isn't excessive it moves -4 degrees or + 4 degrees range when running E-85. This allows for substantive power gains from a more violent combustion and dynamic cylinder pressure = more power. The VVT adds more duration at this time without the increase in EGT = More power on E-85.
And yes... this is speaking relative to the 2014 LT1 N/A form. A range of 40-80hp. Depending on ambient temperature outside. "
Direct quote:
"The timing isn't excessive it moves -4 degrees or + 4 degrees range when running E-85. This allows for substantive power gains from a more violent combustion and dynamic cylinder pressure = more power. The VVT adds more duration at this time without the increase in EGT = More power on E-85.
And yes... this is speaking relative to the 2014 LT1 N/A form. A range of 40-80hp. Depending on ambient temperature outside. "
I suspect the EGT is lower running E85 then running 100 octane racing gas at the track. 100 octane pure gasoline might not give as big a boost to the horsepower as the E85 does.
12-10-2012, 12:40 AM
#46
12-10-2012, 12:58 AM
#47
I posted this in another thread some time ago:
"Turbochargers and superchargers both have their strengths and weaknesses.
With a positive displacement supercharger (like on the LS9 and LSA motors), you get increased torque throughout the rpm range without added exhaust back pressure. So the torque remains high throughout the rpm range. It takes power from the motor to drive it, however, and thus is less efficient than a turbo. Also, your peak boost typically is lower than what a turbo can provide. This is not so much of an issue with a 6.2 L motor, since the net power output still is high. In smaller displacement motors it is more of an issue.
With a turbocharger, if you choose a configuration that gives a lot of boost in the low rpm range, the exhaust backpressure at high rpms is high, so the torque drops. Specifically, you run a smaller turbine with a lower A/R to get quick spool-up, which is more exhaust restrictive. If you choose a turbo with less exhaust back pressure (i.e., larger turbine and/or A/R), it takes longer for the turbo to spool up - i.e., turbo lag. Variable vane geometry helps in this regard. I suspect the patents on this are expensive to license, though, and do not see GM going in this direction.
In my opinion, a centrifugal supercharger is the last resort. Although it does not restrict exhaust flow like a turbo, it provides much less boost than a positive displacement supercharger, and does not wind up sufficiently until high in the rpm range, kind of like a large turbo, but with much less boost. A properly sized turbo will outperform a centrifugal supercharger across the rpm range, and do so more efficiently. The one advantage to the centrifugal supercharger is that it is, comparatively speaking, an easy upgrade."
**New**
With the increased torque in the mid-rpm range the LT1 provides, I can easily see the advantage of using a twin turbocharger setup with a relatively large turbine and A/R on this motor. This would not create huge exhaust backpressure, but still more than a supercharger setup. Nonetheless, the LT1 excels in mid-rpm range torque, and a twin turbo setup would really enhance the torque at high rpms, without the power losses associated with a supercharger.
"Turbochargers and superchargers both have their strengths and weaknesses.
With a positive displacement supercharger (like on the LS9 and LSA motors), you get increased torque throughout the rpm range without added exhaust back pressure. So the torque remains high throughout the rpm range. It takes power from the motor to drive it, however, and thus is less efficient than a turbo. Also, your peak boost typically is lower than what a turbo can provide. This is not so much of an issue with a 6.2 L motor, since the net power output still is high. In smaller displacement motors it is more of an issue.
With a turbocharger, if you choose a configuration that gives a lot of boost in the low rpm range, the exhaust backpressure at high rpms is high, so the torque drops. Specifically, you run a smaller turbine with a lower A/R to get quick spool-up, which is more exhaust restrictive. If you choose a turbo with less exhaust back pressure (i.e., larger turbine and/or A/R), it takes longer for the turbo to spool up - i.e., turbo lag. Variable vane geometry helps in this regard. I suspect the patents on this are expensive to license, though, and do not see GM going in this direction.
In my opinion, a centrifugal supercharger is the last resort. Although it does not restrict exhaust flow like a turbo, it provides much less boost than a positive displacement supercharger, and does not wind up sufficiently until high in the rpm range, kind of like a large turbo, but with much less boost. A properly sized turbo will outperform a centrifugal supercharger across the rpm range, and do so more efficiently. The one advantage to the centrifugal supercharger is that it is, comparatively speaking, an easy upgrade."
**New**
With the increased torque in the mid-rpm range the LT1 provides, I can easily see the advantage of using a twin turbocharger setup with a relatively large turbine and A/R on this motor. This would not create huge exhaust backpressure, but still more than a supercharger setup. Nonetheless, the LT1 excels in mid-rpm range torque, and a twin turbo setup would really enhance the torque at high rpms, without the power losses associated with a supercharger.
12-10-2012, 03:00 AM
#48
**New**
With the increased torque in the mid-rpm range the LT1 provides, I can easily see the advantage of using a twin turbocharger setup with a relatively large turbine and A/R on this motor. This would not create huge exhaust backpressure, but still more than a supercharger setup. Nonetheless, the LT1 excels in mid-rpm range torque, and a twin turbo setup would really enhance the torque at high rpms, without the power losses associated with a supercharger.
With the increased torque in the mid-rpm range the LT1 provides, I can easily see the advantage of using a twin turbocharger setup with a relatively large turbine and A/R on this motor. This would not create huge exhaust backpressure, but still more than a supercharger setup. Nonetheless, the LT1 excels in mid-rpm range torque, and a twin turbo setup would really enhance the torque at high rpms, without the power losses associated with a supercharger.
12-10-2012, 03:57 AM
#49
A single large turbo is phenominal for a car setup exclusively to race, and mostly staying in the high rpm range. It is my understanding, however, for the level of boost that will be used in a street car, twin turbos spool up a little quicker than a single turbo, and thus produce a broader torque curve. Perhaps a quad turbo could do better. I'm not sure, but it may be the case.
12-10-2012, 01:21 PM
#50
Le Mans Master
Thread Starter
Huh! 911s!
That BMW DOHC head is taller than the small block, and yet those turbines are towering over. It will need at least as much hood clearance as the TVS. Then think that 750hp will require much larger turbines. It will be a really tall block.
I would say circuit racing is dominated by all motor applications. If Turbos were so great, there would be virtually no Porsche GT3s sold, only 911 Turbos, and GT2s. I can tell you for a fact there are loads of GT3s on the Nurburgring, probably the most common car there when they rent out the track for Porsche events.
I would say circuit racing is dominated by all motor applications. If Turbos were so great, there would be virtually no Porsche GT3s sold, only 911 Turbos, and GT2s. I can tell you for a fact there are loads of GT3s on the Nurburgring, probably the most common car there when they rent out the track for Porsche events.
Well a already torqued 911 is a grand example of using a power adder road racing on a steel railed track.
Slip a TVS in one and see what you get.
12-10-2012, 01:27 PM
#52
Le Mans Master
Thread Starter
40-80hp on E85!?
What I really want to know is what happens to an LT1 if I dump 100 octane in it at the nearby track?
I can live with 475hp car daily, and 575hp at the track. Any 335 section street tire will be the limitation at that point and I'm not ever planning on running slicks or special order Veyron Michelins.
I can live with 475hp car daily, and 575hp at the track. Any 335 section street tire will be the limitation at that point and I'm not ever planning on running slicks or special order Veyron Michelins.
And speaking of the Veyron. It is another fine example of turbos at work crossing the bounds of performance and economy!
12-10-2012, 01:30 PM
#53
Le Mans Master
Thread Starter
Hope So!
If this is real GM is on it lowering the COG a bit. They do fix things!
Since they are so far along they've got time to go the turbo route, as well. I wonder which one would sell better?:
http://www.lingenfelter.com/engine-p...ce-tvs2300-sup
http://www.lingenfelter.com/engine-p...-hp-twin-turbo
Since they are so far along they've got time to go the turbo route, as well. I wonder which one would sell better?:
http://www.lingenfelter.com/engine-p...ce-tvs2300-sup
http://www.lingenfelter.com/engine-p...-hp-twin-turbo
Last edited by johnglenntwo; 12-10-2012 at 01:45 PM.
12-10-2012, 01:53 PM
#54
Le Mans Master
Thread Starter
But, Check out the Dynos!!!
Way Better!
http://www.lingenfelter.com/Forum/E-...ette%20GT9.jpg 
That fixes this!!!
http://www.lingenfelter.com/Forum/Dy...S3TVS23001.jpg
http://www.lingenfelter.com/Forum/E-...ette%20GT9.jpg
That fixes this!!!
http://www.lingenfelter.com/Forum/Dy...S3TVS23001.jpg
Last edited by johnglenntwo; 12-10-2012 at 01:57 PM.
12-10-2012, 04:38 PM
#55
Advanced
I think that everyone that is saying roots blower is forgetting something very, very important to GM. MPG, aka gas mileage. Look at the epa rating of the ZR1 compared to the ZO6. It is horrible, especially the city figure, but the highway figure is bad too. A turbo motor would allow it to get much better rating on both because while cruising it will be off boost and using much less fuel. So don't underestimate the importance of meeting a particular EPA MPG rating. I think that GM has stated that none of their vehicles will be paying the gas guzzler tax going forward. Remember that was the reason that skip shift was invented, to not pay the gas guzzler tax. So my bet is for a twin turbo motor. GM has been playing with them for a while and even gave Jay Leno a 1000+ hp 7 liter twin turbo for one of his project cars.
12-10-2012, 04:58 PM
#56
Team Owner
I think that everyone that is saying roots blower is forgetting something very, very important to GM. MPG, aka gas mileage. Look at the epa rating of the ZR1 compared to the ZO6. It is horrible, especially the city figure, but the highway figure is bad too. A turbo motor would allow it to get much better rating on both because while cruising it will be off boost and using much less fuel. So don't underestimate the importance of meeting a particular EPA MPG rating. I think that GM has stated that none of their vehicles will be paying the gas guzzler tax going forward. Remember that was the reason that skip shift was invented, to not pay the gas guzzler tax. So my bet is for a twin turbo motor. GM has been playing with them for a while and even gave Jay Leno a 1000+ hp 7 liter twin turbo for one of his project cars.
The cooling effect of the DI, will allow the higher compression ratio, but they will run a little lower boost then if they were running a lower compression ratio engine like the LS9.
E-Force superchargers(599HP) on 10.7:1 CR LS3's have the same highway gas mileage as the stock NA LS3. They just have an additional 165 Horsepower when you go into boost.
12-10-2012, 05:05 PM
#57
Safety Car
Yep. Not an engine cover, the LT1 is released, it does not look like this. It is clearly a supercharger sitting in the valley. If you look at the LT1 you can see where there are bolt holes ready for mouthing the charger assembly on the driver's side of the engine front. LT1 was built specifically for FI, it is now clearer than ever.
12-10-2012, 05:10 PM
#58
Safety Car
It would be nice for GM to optimize one 'Vette for track use, a la GT3. Porsche is a great example of a company who makes a screamer for track use, it knows motorsport. GM did too, releasing the Z06. For the Porsche crowd it doesn't matter that you release the GT3 at end of the generation if need be, people will still buy it. For power hungry 'Vette owners things aren't so clear, what if the zo6 got release after the ZR1? No bueno.
12-10-2012, 05:12 PM
#59
Le Mans Master
Thread Starter
Right On!
I think that everyone that is saying roots blower is forgetting something very, very important to GM. MPG, aka gas mileage. Look at the epa rating of the ZR1 compared to the ZO6. It is horrible, especially the city figure, but the highway figure is bad too. A turbo motor would allow it to get much better rating on both because while cruising it will be off boost and using much less fuel. So don't underestimate the importance of meeting a particular EPA MPG rating. I think that GM has stated that none of their vehicles will be paying the gas guzzler tax going forward. Remember that was the reason that skip shift was invented, to not pay the gas guzzler tax. So my bet is for a twin turbo motor. GM has been playing with them for a while and even gave Jay Leno a 1000+ hp 7 liter twin turbo for one of his project cars.
12-10-2012, 05:23 PM
#60
Le Mans Master
Thread Starter
You did see those dynos, Right?
It would be nice for GM to optimize one 'Vette for track use, a la GT3. Porsche is a great example of a company who makes a screamer for track use, it knows motorsport. GM did too, releasing the Z06. For the Porsche crowd it doesn't matter that you release the GT3 at end of the generation if need be, people will still buy it. For power hungry 'Vette owners things aren't so clear, what if the zo6 got release after the ZR1? No bueno.
The 911 should give way to a mid, but again, packaging has to be easier in the rear eng..
