Steve Wood
Active Member
- Joined
- Jul 18, 2001
Originally posted by RealFastV6
CT... you guys all wonder why we pay so much for gas... well, its Magical gas.
Geez, we make all the damn gas down here and send the good stuff to CT?
Advantages to bigger turbo on pump gas?
- Thread starter GN and Sho's
- Start date
Geez, we make all the damn gas down here and send the good stuff to CT?
Steve Wood
Active Member
- Joined
- Jul 18, 2001
Actually, the blow off valve works better for disposing of the pent up boost that kicks back against the compressor when one lifts off the throttle than they do for eliminating compressor surge which is a completely different animal.
Turbo__Tim
One heck of a Tim!
- Joined
- May 25, 2001
This makes good reading...
http://www.turbobuick.com/forums/showthread.php?threadid=17878&referrerid=2592
http://www.turbobuick.com/forums/showthread.php?threadid=17878&referrerid=2592
REDS HOT AIR
Buick Tweaker
- Joined
- May 24, 2001
i'll make it short and simple on my 49 turbo iwas running 17-18# everyday on 93 octane
on my 51 turbo i ran 18-19# everyday on 93 octane and on cool nights 20-21#
now since the well known turbo problems im back on my stock turbo and the same 93 octane and i pick up slight knock at 16-17# on 3rd gear shift.
all the other settings got 0 knock
on my 51 turbo i ran 18-19# everyday on 93 octane and on cool nights 20-21#
now since the well known turbo problems im back on my stock turbo and the same 93 octane and i pick up slight knock at 16-17# on 3rd gear shift.
all the other settings got 0 knock
GNSCOTT is capable of fighting his own battles, but I've got to jump in here on this one. I bought this block to have as a backup and can only say what it does now. It's the same cam and hyper pistons (bought as shortblock only), my stock unported heads, TE60 in a 3600lb car w/me in it. It went 11.5's on 19psi. I can't say he did, or did not go 11.2's because I didn't see it. From what I've seen and know of these cars, a better 60' and more boost than on my runs would obviously net a better time, don't you think? Now that I'm okay that the motor is fine, it's about to come out, be bagged and stored for future use. I have no reason to doubt his times are bogus based on my experience and from others who have posted to have run 10's on pump gas.
-Bobby
-Bobby
Get a chip that sets your timing to 0. Hell you can likely run 23 lbs like that. (I run 20-21 on the street with 0 timing and absolutely no knock and perfect looking plugs when I pull them)
Or get Alchy injection and actually be able to run timing advance as well.
B
Butch
Guest
The one thing that I didn't see in any of these comments was this...
People talk about size of turbo and efficiency at a certain boost level.
Wouldn't it be more accurate to say that a larger turbo can move the same amount of air (CFM not PSI) as a smaller turbo more efficiently (with less heat). Resulting in more power at a lower boost level.
It's all about how much fuel and air you can get into, and out of the engine, right? And cooler fuel and air is better (Nitrous comes to mind). So the reason you want a larger turbo is to move more air, more efficiently (with less heat).
I am no thermodynamic engineer, but I doubt that larger turbo's are more efficient (overall) than smaller turbos. Unless they are 15 years newer and more technologically advanced.
What I mean is that a PTE-52 is probably more efficient than a PTE-70 up to a certain level, then the lines cross and the PTE-70 begins to move more air (CFM) than the PTE-52 can move efficiently. That is why the entire engine combination is so important. It doesn't do us any good to be able to get more air and fuel into the engine if we cant get it out.
I have other things to add but I will stop here and see what everyone thinks.
Butch
People talk about size of turbo and efficiency at a certain boost level.
Wouldn't it be more accurate to say that a larger turbo can move the same amount of air (CFM not PSI) as a smaller turbo more efficiently (with less heat). Resulting in more power at a lower boost level.
It's all about how much fuel and air you can get into, and out of the engine, right? And cooler fuel and air is better (Nitrous comes to mind). So the reason you want a larger turbo is to move more air, more efficiently (with less heat).
I am no thermodynamic engineer, but I doubt that larger turbo's are more efficient (overall) than smaller turbos. Unless they are 15 years newer and more technologically advanced.
What I mean is that a PTE-52 is probably more efficient than a PTE-70 up to a certain level, then the lines cross and the PTE-70 begins to move more air (CFM) than the PTE-52 can move efficiently. That is why the entire engine combination is so important. It doesn't do us any good to be able to get more air and fuel into the engine if we cant get it out.
I have other things to add but I will stop here and see what everyone thinks.
Butch
G
GNSCOTT
Guest
Bobby, glad to see the short block is running well.
Bob James. Ask your new buddy Jim Hooper if my car was running 25psi wth 94 octane, he drove the car before and after the heads/ turbo upgrade, and they both ran the 25psi with 94 octane. Lying would be telling the town that you were not running an auto shop out of your garage.
Ask Jack Cotton if my claims are true. He trailered me up there to race an we got there after the fuel was closed and i ran an 11.4 on 94 octane , 25psi. He has also test driven my car cuntless times at those levels.
I know i gave at least4 other board members a ride in the car to prove it to them because i thought there was something wrong with the car. I changed knock sensors, boost guages and did everything i could to make it knock. Finally at 26 psi it began to detonate, and upping the timing made it knock like crazy.
Bob James. Ask your new buddy Jim Hooper if my car was running 25psi wth 94 octane, he drove the car before and after the heads/ turbo upgrade, and they both ran the 25psi with 94 octane. Lying would be telling the town that you were not running an auto shop out of your garage.
Ask Jack Cotton if my claims are true. He trailered me up there to race an we got there after the fuel was closed and i ran an 11.4 on 94 octane , 25psi. He has also test driven my car cuntless times at those levels.
I know i gave at least4 other board members a ride in the car to prove it to them because i thought there was something wrong with the car. I changed knock sensors, boost guages and did everything i could to make it knock. Finally at 26 psi it began to detonate, and upping the timing made it knock like crazy.
Richard Inglett
Member
- Joined
- Jan 22, 2002
Don't Do It!
GNVAIR,
Please do yourself a favor. Don't even try. Although it is difficult to say for sure, I believe the TE45A is equivalent to a stealth 63. It is a big turbo (at least for most us). It will not perform with same injectors and programming that works well with a TA49. If your lucky, all you'll do is blow a head gasket but more than likely, you'll spit out your crankshaft.
Strikeeagle's comment about compressor curves is valid and Steve Wood's comment about cylinder pressures nails it. First, some of the larger turbos are actually less efficient than some smaller ones. This equates to more recirculation in the turbo and thus, more heat. Second, CFM is a huge factor on cylinder pressure. With a high enough flowrate, 15 psig can be more harmful than 25 psig from a smaller turbo. Especially with 93 octane gas.
There is more to it than just swapping from a smaller to a larger turbo. Your TA49 swap was a definate upgrade to a better turbo and more than likely, a more efficient turbo. Your next swap is more serious and will demand larger injectors and programming to make it work.
One last comment. The larger the turbo gets, the more important porting & exhaust become. With stock unported heads and assuming 85 percent efficiency, our engines can only move about 195 cubic inches of air every two revolutions. Trying to force more air than this will cause surging. Rarely an issue at higher rpm's but some cars will shake & shudder at low rpm's (ex. 2000 rpm @ 5 psig). Review of a compressor curve makes it easy to see why. The operating point will be to the left of the surge limit line. Higher rpm's will usually keep the turbo to the right side of this line but it doesn't necessarily correspond to an efficient operating point. In short, bigger turbo is not an automatic increase in efficiency and therfore does not always mean cooler air temperatures. You have to have the combo matched and have plenty of fuel. Otherwise, you will learn the hard way.
GNVAIR,
Please do yourself a favor. Don't even try. Although it is difficult to say for sure, I believe the TE45A is equivalent to a stealth 63. It is a big turbo (at least for most us). It will not perform with same injectors and programming that works well with a TA49. If your lucky, all you'll do is blow a head gasket but more than likely, you'll spit out your crankshaft.
Strikeeagle's comment about compressor curves is valid and Steve Wood's comment about cylinder pressures nails it. First, some of the larger turbos are actually less efficient than some smaller ones. This equates to more recirculation in the turbo and thus, more heat. Second, CFM is a huge factor on cylinder pressure. With a high enough flowrate, 15 psig can be more harmful than 25 psig from a smaller turbo. Especially with 93 octane gas.
There is more to it than just swapping from a smaller to a larger turbo. Your TA49 swap was a definate upgrade to a better turbo and more than likely, a more efficient turbo. Your next swap is more serious and will demand larger injectors and programming to make it work.
One last comment. The larger the turbo gets, the more important porting & exhaust become. With stock unported heads and assuming 85 percent efficiency, our engines can only move about 195 cubic inches of air every two revolutions. Trying to force more air than this will cause surging. Rarely an issue at higher rpm's but some cars will shake & shudder at low rpm's (ex. 2000 rpm @ 5 psig). Review of a compressor curve makes it easy to see why. The operating point will be to the left of the surge limit line. Higher rpm's will usually keep the turbo to the right side of this line but it doesn't necessarily correspond to an efficient operating point. In short, bigger turbo is not an automatic increase in efficiency and therfore does not always mean cooler air temperatures. You have to have the combo matched and have plenty of fuel. Otherwise, you will learn the hard way.
Butch -
while a larger turbo has the ability to move more cfm efficiently, it doesn't automatically do so. It only moves what the engine can take.
Take two idnetical engines. Assume that the rpm, boost, IC outlet temperature, and exhaust backpressure are the same. If engine #1, with a stock turbo, is pulling 500 cfm through the turbo, then engine #2 with a TE-63 must also be pulling 500 cfm. That TE-63 may be capable of moving 900 cfm, but just because it CAN do it doesn't mean that it WILL do it. To get use of that 900 cfm flow capacity, you have to rev the engine higher or run more boost.
So, why could there be some gains when bolting on a bigger turbo at the same boost level? Charge temperature is one thing, but I don't think it is as big a player as most people seem to think.
Say you go from a 65% compressor to a 75% compressor at 20 psig discharge. The temperature at the IC inlet may drop from 335 F to 300 F. Which is nice, but then it goes through the intercooler. That 35 F improvement at the IC inlet does NOT make for a 35 F improvement on the outlet. It will be less. Maybe a 10 F improvement, maybe 20 F, something like that. How much power is that worth? The old saw about 10F = 1% hp holds true here at the IC outlet. Actually I think 1.5% is closer. So on a 350 hp GN, that 20 F (if it really is that much) would be worth about 10 hp (a little over 5 hp per 10 F drop).
So, temperature effect alone, a 10% increase in efficiency might be worth only 10 hp. That doesn't explain much.
I think the biggest gains are exhaust side. A better turbine wheel and turbine housing are just like putting on a better exhaust system, losing your converter, going with a THDP, etc... All these things reduce the exhaust backpressure, which leaves less exhaust in the cylinders, which gives more room for fresh charge, which increases power. This will increase the air flow through the compressor and into the engine even though the boost level, rpm, temperature, etc stay the same.
A more efficient compressor wheel takes less hp to turn it, so less exhaust back pressure is required by the turbine wheel to give that power to turn the compressor wheel, which helps out more. A more efficient turbine wheel and housing also require less backpressure to provide the driver hp, which helps too. This is the reason why a 0.82 AR turbine housing would make more hp than a 0.63 housing at the same boost level/rpm/etc. This is the reason why a PTE-52 might be expected to outperform a TE-60 (they both have identical compressor sides by my understanding, it is the exhaust sides that are different). Think about the system as a whole, don't just focus on the compressor side. A big compressor attached to a little turbine isn't going to run mcuh (if any) any better than a small compressor attached to that same turbine.
John
while a larger turbo has the ability to move more cfm efficiently, it doesn't automatically do so. It only moves what the engine can take.
Take two idnetical engines. Assume that the rpm, boost, IC outlet temperature, and exhaust backpressure are the same. If engine #1, with a stock turbo, is pulling 500 cfm through the turbo, then engine #2 with a TE-63 must also be pulling 500 cfm. That TE-63 may be capable of moving 900 cfm, but just because it CAN do it doesn't mean that it WILL do it. To get use of that 900 cfm flow capacity, you have to rev the engine higher or run more boost.
So, why could there be some gains when bolting on a bigger turbo at the same boost level? Charge temperature is one thing, but I don't think it is as big a player as most people seem to think.
Say you go from a 65% compressor to a 75% compressor at 20 psig discharge. The temperature at the IC inlet may drop from 335 F to 300 F. Which is nice, but then it goes through the intercooler. That 35 F improvement at the IC inlet does NOT make for a 35 F improvement on the outlet. It will be less. Maybe a 10 F improvement, maybe 20 F, something like that. How much power is that worth? The old saw about 10F = 1% hp holds true here at the IC outlet. Actually I think 1.5% is closer. So on a 350 hp GN, that 20 F (if it really is that much) would be worth about 10 hp (a little over 5 hp per 10 F drop).
So, temperature effect alone, a 10% increase in efficiency might be worth only 10 hp. That doesn't explain much.
I think the biggest gains are exhaust side. A better turbine wheel and turbine housing are just like putting on a better exhaust system, losing your converter, going with a THDP, etc... All these things reduce the exhaust backpressure, which leaves less exhaust in the cylinders, which gives more room for fresh charge, which increases power. This will increase the air flow through the compressor and into the engine even though the boost level, rpm, temperature, etc stay the same.
A more efficient compressor wheel takes less hp to turn it, so less exhaust back pressure is required by the turbine wheel to give that power to turn the compressor wheel, which helps out more. A more efficient turbine wheel and housing also require less backpressure to provide the driver hp, which helps too. This is the reason why a 0.82 AR turbine housing would make more hp than a 0.63 housing at the same boost level/rpm/etc. This is the reason why a PTE-52 might be expected to outperform a TE-60 (they both have identical compressor sides by my understanding, it is the exhaust sides that are different). Think about the system as a whole, don't just focus on the compressor side. A big compressor attached to a little turbine isn't going to run mcuh (if any) any better than a small compressor attached to that same turbine.
John
The Radius Kid
Active Member
- Joined
- Jan 26, 2002
Exactly John.Couldn't of said it better myself.The compressor surge curves are only half of the story.The other side,as you and Steve said,is the engine and exhaust flow.
I just changed from a stock turbo -I/C,to a 63e-V-1 combo.I can tell you at the same boost levels,ain't No Way a stocker setup is gonna touch that puppy.I was getting some surge around 12-13 lbs. of boost,but found out I overtightened the clamps for the V-1 piping on the upo and was leaking under boost.Of course the connections leaked under higher boost.Expanded them back out,less clamping pressure,and .....voila,it's time to haul heiny.
BTW,I have 50 lber's and a hot wired 340,reworked doghouse with 65 mm T-body,relocated 3" Impy Maf[thanks Bruce!],3" THDP,dual 3" Cotton's exhaust[nice!],boxed lowers,mildly ported heads,cold air kit[that sure works,did mine 5+ years ago],2800 stall w LU[yeah I know,needs a converter change,is getting a Yank 3500 N/L and Art Carr shift kit],relocated heated O2.
Don't have track times,rarely have time to get there.I'm usually doing some sort of work for somebody else's car.I think I'll have to go this year.This could be fun.
I just changed from a stock turbo -I/C,to a 63e-V-1 combo.I can tell you at the same boost levels,ain't No Way a stocker setup is gonna touch that puppy.I was getting some surge around 12-13 lbs. of boost,but found out I overtightened the clamps for the V-1 piping on the upo and was leaking under boost.Of course the connections leaked under higher boost.Expanded them back out,less clamping pressure,and .....voila,it's time to haul heiny.
BTW,I have 50 lber's and a hot wired 340,reworked doghouse with 65 mm T-body,relocated 3" Impy Maf[thanks Bruce!],3" THDP,dual 3" Cotton's exhaust[nice!],boxed lowers,mildly ported heads,cold air kit[that sure works,did mine 5+ years ago],2800 stall w LU[yeah I know,needs a converter change,is getting a Yank 3500 N/L and Art Carr shift kit],relocated heated O2.
Don't have track times,rarely have time to get there.I'm usually doing some sort of work for somebody else's car.I think I'll have to go this year.This could be fun.
REDS HOT AIR
Buick Tweaker
- Joined
- May 24, 2001
finally people who agree with me about the exaust side being the gain...
RealFastV6
Plays with Trucks
- Joined
- May 26, 2001
CLIFF NOTES:
A stock turbo putting out 18-19 psi into a motor with basic upgrades (dp, exhaust, mafpipe, filter, etc) is out of its peak efficiency.
A larger turbo would net REAL LIFE horsepower gains without turning up the boost.
The Horsepower gains would come from...
a) A cooler intake charge due to a more thermally efficient compressor.
b) Greater exhaust gas scavenging in the cylinders.
The End.
A stock turbo putting out 18-19 psi into a motor with basic upgrades (dp, exhaust, mafpipe, filter, etc) is out of its peak efficiency.
A larger turbo would net REAL LIFE horsepower gains without turning up the boost.
The Horsepower gains would come from...
a) A cooler intake charge due to a more thermally efficient compressor.
b) Greater exhaust gas scavenging in the cylinders.
The End.
Keep this in mind: observed boost is a less than optimal way to compare two different turbos.
What matters is mass airflow. Oxygen is what is needed to fuel the fire. You describe amounts of air by weight, not volume. CFM is deceiving. One ft^3 of dry air at 100°F only has about 90% of the oxygen as dry air at 50°F. That 10% can make a big difference in a warmed over engine.
Also, pumping (compressor) efficiency is power delivered to the air divided by power input to the turbine. The whole concept confuses a lot of folks. A PTE51 can move as much air as a stocker at a lower efficiency, and when it hits its "sweet spot" it can move much more air.
What matters is mass airflow. Oxygen is what is needed to fuel the fire. You describe amounts of air by weight, not volume. CFM is deceiving. One ft^3 of dry air at 100°F only has about 90% of the oxygen as dry air at 50°F. That 10% can make a big difference in a warmed over engine.
Also, pumping (compressor) efficiency is power delivered to the air divided by power input to the turbine. The whole concept confuses a lot of folks. A PTE51 can move as much air as a stocker at a lower efficiency, and when it hits its "sweet spot" it can move much more air.
D
Darrens89Z
Guest
GNScott,this does not pertain to this post at all but if you are ever at Cottons while I stop in,could you be so kind to give me a ride in your car?I havent been in a Turbo 6 car in quite some time,especially a sub 11 sec one
and would enjoy it until I get my project completed.Only if the heads have been ported and the massflow is greater than a normal 231 V6. A stock turbo is still pretty efficient at 18-19 psi.
I don't think anyone else in this whole huge thread has claimed this and backed it up with real data. The people that have gone "Faster with a larger turbo" have done so at higher boost levels claiming that the larger turbo allowed them to run higher boost levels on pump gas. Keeping the boost level at 18 psi and below on a stock long block, stock converter car, stock turbo wins (or loses by a .1 or so)
For a) the difference is tiny at pump gas boost levels and would be the difference of .05 -.10 and not allow a 12.5 car to run 11.5 on pump gas.
For b) it would likely have more to do with pumping losses than exhaust scavenging. Compressing air requires work to be done. That work has to be done by something. A larger turbine restricts mass flow less allowing more top end horsepower (at the expense of low end torque)
For some reason I doubt it
Re: Don't Do It!
I never said that I was trying it with the same set up. FYI, the TE45A from John Craig has a 66mm wheel in it. It is not similar to a 63 from PTE. Not even close unless PTE is installing larger compressor wheels now. This turbo I have will be going on another engine with ported heads, 72lb injectors, ME chip and will be installing a mild cam and a 9x11 convertor. I know what I am doing and when I have a problem, I ask questions.
The Radius Kid
Active Member
- Joined
- Jan 26, 2002
Okay,here's one for you.
Let's talk about FUBAR's combo.
CAS V-2
Untouched Champion GN-1's
Hooker exhaust
THDP w/test tube
BFG drag radials
Stock engine w/ girdle and caps
T64e turbo
50 lber's
Lubrant street chip
Stock headers
Connelly's 218 cam
62 mm T-Body with doghouse done by me[no shoehorn]
Cold air kit on the intake
Times?
11.65@116mph w/1.70 short time.
19 lbs of boost/pump gas.
This lad gets it on[58 years old and he still loves having fun].
I can see a low eleven with a better short[he'll get it].
Maybe even a ten with a little more wick.
Lawrence Connelly said it best;"Get it in,get it out,get it to the ground".
Red,you're right.There is something to be said for a good exhaust side.
Somebody was listening when Lawrence spoke.I was too.
I can't see a stock turbo moving enough mass with any kind of efficiency to make 450 hp to the rear wheels.
The times listed are true as is the combo.I know,I was there.I helped him tune it.
Any comments?
Let's talk about FUBAR's combo.
CAS V-2
Untouched Champion GN-1's
Hooker exhaust
THDP w/test tube
BFG drag radials
Stock engine w/ girdle and caps
T64e turbo
50 lber's
Lubrant street chip
Stock headers
Connelly's 218 cam
62 mm T-Body with doghouse done by me[no shoehorn]
Cold air kit on the intake
Times?
11.65@116mph w/1.70 short time.
19 lbs of boost/pump gas.
This lad gets it on[58 years old and he still loves having fun].
I can see a low eleven with a better short[he'll get it].
Maybe even a ten with a little more wick.
Lawrence Connelly said it best;"Get it in,get it out,get it to the ground".
Red,you're right.There is something to be said for a good exhaust side.
Somebody was listening when Lawrence spoke.I was too.
I can't see a stock turbo moving enough mass with any kind of efficiency to make 450 hp to the rear wheels.
The times listed are true as is the combo.I know,I was there.I helped him tune it.
Any comments?
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