Dan, I still disagree. I would prefer to build an engine that does not require boost for street driving. Why go to boost when NA will do the job much easier at lower RPMs? Use the turbo to fill in where a low RPM torque engine fall short.
Many modern turbo cars use small turbos because they want to sell the "turbo feel" with little or no lag, and little or no regard to heat or top end. Which car is faster, the 300ZX or the 911? Off the line it's the 300ZX, but it runs out of steam pretty quick, where the 911 really gets moving. Which onewould you reather canyon cruise in?
Build the engine so that it doesn't need boost down low and you won't know there is turbo lag. The boost comes in smoothly where the NA would start to choke off. With a larger turbo the heat is less, the boost can be less, there is very little probability of surge, and even the wastegate could become a non-issue since it is possible that the engine never be able to push the turbo to high enough boost to require one. I don't agree that small turbos are useful for anything other than a low RPM monster that will never see RPMs above 4k.
I'm not advocating a high boost turbo. I'm advocating, in this instance, a low boost turbo, making no more than 9 psi boost at max power. High boost turbos are a different argument. Especially in a Type 4 engine high boost is difficult. For that reason many folks look at you twice as funny for wanting to turbo a Type 4 than they do just by you running a Type 4. Most say T1 or nothing if you are boosting it.
You don't want to turn 7k on a street engine? The approach is still the same. Make the boost come on just above the torque peak, and come on gently, as in a larger turbo. Flatten out the horsepower peak. Reduce the amount of boost to a level where heat becomes less an issue. Just do it at a lower RPM.
I've been playing with ideas of a triple turbo engine of a completely different sort. It's probably totally unusable, but it's just an idea. One large turbo makes high boost. It splits into 2 other turbos but not used in the conventional method. After the first turbo the air is run through an intercooler. Then the intake air is run through the compression side of the second turbos (parallel twin turbos as the second stage) as normal and into a second intercooler. After that second stage of boost and cooling the air runs through the TURBINE side of the second stage and decompresses. That's right. The second stage of compressors is run by the second stage of turbines. Some boost will still be available, but losses will reduce it to less than 15 psi. However, the volume of air will be large, the density of the air will be extremely high, and the temp will have dropped to below ambient. OK, so it's complicated and radical. Crazy ideas spawn reasonable ones, and maybe some good will come out of it.
Looking to modern conventional cars is misleading when it comes to what is technically sound. Most turbo cars are designed to sell, not perform at peak.
The SAAB has a low boost turbo. The WRX has a low boost turbo. Low boost turbos are coming into their own, and are a totally differnt animal than the 15-30 lb boost monsters many of you are familiar with.
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*** Teach a Man to Fish ***
Searoy
advice on turbo set up, please
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danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
advice on turbo set up, please
>>>I would prefer to build an engine that does not require boost for street driving.<<<
then you should be using nitrous, not turbo power... it's cheaper and easier to install.
>>>Why go to boost when NA will do the job much easier at lower RPMs?<<<
n.a. motors have to work hard to make h.p. at any rpm level, regardless of the engine design... if your motor has a turbo on it, at some point in the rpm range you are incurring exhaust flow losses when the turbo isn't making boost.
in other words, searoy, you want an unused turbo clogging up the exhaust system... a performance liability that decreases engine efficiency... compare that with what happens to a properly designed turbo system, that can, for instance, replace vacuum with positive pressure, even if it's less than one psi while cruising down the freeway... engine efficiency is increased.
>>>I don't agree that small turbos are useful for anything other than a low RPM monster that will never see RPMs above 4k.<<<
????
>>>The SAAB has a low boost turbo. The WRX has a low boost turbo.<<<
they also have high compression, knock sensors, and water-cooled heads that don't rise by 100 degrees on hills... to you know what happens to the octane requirements when the engine heat goes up that much?? you are comparing apples to oranges.
as mark herbert already demonstrated, it's a fool's game to build a pump-gas acvw motor with high compression... i hope that isn't what you are advocating.
you can put a lot more boost to a low c.r. motor, and therefore make more h.p. on the same pump gas... without sacrificing driveability, if the boost kicks in earlier.
dan
oceanstreetvideo.com
then you should be using nitrous, not turbo power... it's cheaper and easier to install.
>>>Why go to boost when NA will do the job much easier at lower RPMs?<<<
n.a. motors have to work hard to make h.p. at any rpm level, regardless of the engine design... if your motor has a turbo on it, at some point in the rpm range you are incurring exhaust flow losses when the turbo isn't making boost.
in other words, searoy, you want an unused turbo clogging up the exhaust system... a performance liability that decreases engine efficiency... compare that with what happens to a properly designed turbo system, that can, for instance, replace vacuum with positive pressure, even if it's less than one psi while cruising down the freeway... engine efficiency is increased.
>>>I don't agree that small turbos are useful for anything other than a low RPM monster that will never see RPMs above 4k.<<<
????
>>>The SAAB has a low boost turbo. The WRX has a low boost turbo.<<<
they also have high compression, knock sensors, and water-cooled heads that don't rise by 100 degrees on hills... to you know what happens to the octane requirements when the engine heat goes up that much?? you are comparing apples to oranges.
as mark herbert already demonstrated, it's a fool's game to build a pump-gas acvw motor with high compression... i hope that isn't what you are advocating.
you can put a lot more boost to a low c.r. motor, and therefore make more h.p. on the same pump gas... without sacrificing driveability, if the boost kicks in earlier.
dan
oceanstreetvideo.com
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danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
advice on turbo set up, please
>>>Today all Saab cars are turboed... looking at the new cars today tell alot of how to build a strong and reliable turbo engine. the Saab has a flat tourque curve from almost idle... small widerange turbos.<<<
saab is doing some phenomenal things with automotive engineering... variable-length intake systems, for example.
>>>placing the intercooler in the engine compartment is not a big problem, By placing fans to blow through it, it will cool the intake air very well. (i have tried this.)<<<
were you able to get the decklid shut on it??
>>>On my current engine I have placed the intercooler in the rear luggage tray. enclosed in a sealed box with a radiator fan pulling air from above the gearbox. this gives me 30*-35* Celsius chargeair temp.<<<
can you translate that into fahrenheit?
that sounds pretty low to me, you would have to compare it to the ambient air temps... are you blow-thru injected?
dan
oceanstreetvideo.com
[This message has been edited by danimal (edited 09-17-2001).]
saab is doing some phenomenal things with automotive engineering... variable-length intake systems, for example.
>>>placing the intercooler in the engine compartment is not a big problem, By placing fans to blow through it, it will cool the intake air very well. (i have tried this.)<<<
were you able to get the decklid shut on it??
>>>On my current engine I have placed the intercooler in the rear luggage tray. enclosed in a sealed box with a radiator fan pulling air from above the gearbox. this gives me 30*-35* Celsius chargeair temp.<<<
can you translate that into fahrenheit?
that sounds pretty low to me, you would have to compare it to the ambient air temps... are you blow-thru injected?dan
oceanstreetvideo.com
[This message has been edited by danimal (edited 09-17-2001).]
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Searoy
- Posts: 2869
- Joined: Thu Aug 23, 2001 12:01 am
advice on turbo set up, please
A large turbo will add very little restriction to the exhaust path. A small turbo would add quite a lot. Besides, a high torque low RPM engine can use slightly more backpressure than a high RPM engine. That's where you start differently when planning the engine.
You speak of my suggestion as though it's not properly designed. This is where you are mistaken. It is designed properly to give boost were boost is required, and not give boost where it is not. It uses the engine's NA efficiency until it becomes inefficient, then adds boost to bring efficiency back up. Done properly the turbo actually will begin to pick up just past the torque peak, where torque numbers are beginning to go down but horsepower numbers are still going up. However it won't produce boost yet, but instead simply decrease the vacuum. Where the engine would normally have it's NA horsepower peak the turbo will actually begun to make boost and will rise slowly as RPMs climb past the point where the engine in NA configuration ceases to be efficient.
If you design an engine to go to high RPMs NA then a couple of things happen: You lose boost out the tailpipe since the overlap duration is too long for boost, and you have to climb to even higher RPMs for that boost to do any good.
If you design an engine that relies on boost to make power, then you have a pig of an engine until the turbo spools, and a turbo that dumps a lot of heat into the intake air unless conditions are perfect, which they never are.
High compression turbocharged ACVW engines? Sort of. Compression 8.0-8.5:1. Is this a problem? No. There's no boost to complicate things until well past the NA range. Ignition advance moves up normally to the point where it reaches it's mechanical limit. Shortly thereafter a little boost should be available, instead of ignition advance. You use boost instead of ignition advance at that range.
You don't need boost to kick in early if you design the engine so that it doesn't need it early. If you choose to design an engine that requires boost to make power at a lower RPM range then you will require a smaller turbo and make more heat.
Not wrong, just different. I think my way is more efficient.
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*** Teach a Man to Fish ***
Searoy
You speak of my suggestion as though it's not properly designed. This is where you are mistaken. It is designed properly to give boost were boost is required, and not give boost where it is not. It uses the engine's NA efficiency until it becomes inefficient, then adds boost to bring efficiency back up. Done properly the turbo actually will begin to pick up just past the torque peak, where torque numbers are beginning to go down but horsepower numbers are still going up. However it won't produce boost yet, but instead simply decrease the vacuum. Where the engine would normally have it's NA horsepower peak the turbo will actually begun to make boost and will rise slowly as RPMs climb past the point where the engine in NA configuration ceases to be efficient.
If you design an engine to go to high RPMs NA then a couple of things happen: You lose boost out the tailpipe since the overlap duration is too long for boost, and you have to climb to even higher RPMs for that boost to do any good.
If you design an engine that relies on boost to make power, then you have a pig of an engine until the turbo spools, and a turbo that dumps a lot of heat into the intake air unless conditions are perfect, which they never are.
High compression turbocharged ACVW engines? Sort of. Compression 8.0-8.5:1. Is this a problem? No. There's no boost to complicate things until well past the NA range. Ignition advance moves up normally to the point where it reaches it's mechanical limit. Shortly thereafter a little boost should be available, instead of ignition advance. You use boost instead of ignition advance at that range.
You don't need boost to kick in early if you design the engine so that it doesn't need it early. If you choose to design an engine that requires boost to make power at a lower RPM range then you will require a smaller turbo and make more heat.
Not wrong, just different. I think my way is more efficient.
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*** Teach a Man to Fish ***
Searoy
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danimal
- Posts: 958
- Joined: Wed Jun 13, 2001 12:01 am
advice on turbo set up, please
>>>A large turbo will add very little restriction to the exhaust path.<<<
all turbos are restrictive to exhaust flow by the sheer fact that they are there, increasing the back pressure... plus it's nearly impossible to get a tuned-length turbo header for the acvw motor, so the very nature of the turbo header itself is counterproductive to making the max possible n.a. h.p.
>>>You speak of my suggestion as though it's not properly designed.<<<
you speak of your suggestion as tho it is properly designed... yet you have provided no specific information, and you refuse to accept the concept of low boost at low rpm's as being more efficient than an n.a. motor.
>>>It is designed properly to give boost were boost is required, and not give boost where it is not.<<<
all right, what are the exact details that will allow this to happen?
>>>If you design an engine that relies on boost to make power, then you have a pig of an engine until the turbo spools<<<
i think you better go back and re-read steve's post on how his engine performs... then expain why that giant power band is unacceptable to you.
>>>High compression turbocharged ACVW engines? Sort of. Compression 8.0-8.5:1. Is this a problem? No.<<<
searoy, it's probably a waste of time, but i'll leave you with this:
"The problem was I still had 92 pump gas in it and I (thought I barely tuned up the boost. Wrong! Instead of 5 lbs it was at 10 lbs when I dumped the clutch. The car left good but I heard the noise that we all don`t want to hear. Compression leak....I think I cracked a cylinder... thats just too high(boost) for an 8.3 to 1 motor on 92 octane" -mark herbert, 2/01
btw, mark had 10mm head studs... i run 8mm head studs, with up to 15 psi of boost on 91 octane... all day long.
dan
oceanstreetvideo.com
[This message has been edited by danimal (edited 09-17-2001).]
all turbos are restrictive to exhaust flow by the sheer fact that they are there, increasing the back pressure... plus it's nearly impossible to get a tuned-length turbo header for the acvw motor, so the very nature of the turbo header itself is counterproductive to making the max possible n.a. h.p.
>>>You speak of my suggestion as though it's not properly designed.<<<
you speak of your suggestion as tho it is properly designed... yet you have provided no specific information, and you refuse to accept the concept of low boost at low rpm's as being more efficient than an n.a. motor.
>>>It is designed properly to give boost were boost is required, and not give boost where it is not.<<<
all right, what are the exact details that will allow this to happen?
>>>If you design an engine that relies on boost to make power, then you have a pig of an engine until the turbo spools<<<
i think you better go back and re-read steve's post on how his engine performs... then expain why that giant power band is unacceptable to you.
>>>High compression turbocharged ACVW engines? Sort of. Compression 8.0-8.5:1. Is this a problem? No.<<<
searoy, it's probably a waste of time, but i'll leave you with this:
"The problem was I still had 92 pump gas in it and I (thought I barely tuned up the boost. Wrong! Instead of 5 lbs it was at 10 lbs when I dumped the clutch. The car left good but I heard the noise that we all don`t want to hear. Compression leak....I think I cracked a cylinder... thats just too high(boost) for an 8.3 to 1 motor on 92 octane" -mark herbert, 2/01
btw, mark had 10mm head studs... i run 8mm head studs, with up to 15 psi of boost on 91 octane... all day long.
dan
oceanstreetvideo.com
[This message has been edited by danimal (edited 09-17-2001).]
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Searoy
- Posts: 2869
- Joined: Thu Aug 23, 2001 12:01 am
advice on turbo set up, please
My brain hurts. My eyes are bleary. My boss is wondering where the hell I am.
I just read in the archive a thread called "cams vs. compression." It's not actually a thread. It's a whole damned sweater.
It let me know I'm heading the right direction with my idea, and gave me a little inspiration as well.
Webcam 111 grind. Maybe 8.0-1 is too much. Maybe 7.5:1 is better, maybe not. I'll figure on it some more.
That cam with that compression, all else accounted for, makes a torque monster that won't rev high. It won't rev high because the piston can't pull enough air into the cylinders and continue to make torque.
Add a turbo that is large enough that it creates only minimal exhaust back pressure, and has a large enough turbine that it won't provide boost until the torque curve, and thus the breathing ability of the engine, drops off. The turbos job is merely to increase the pressure of the intake manifold so that instead of more time for the air to rush in it has more force, more speed, and can fill the cylinder more over a shorter period of time, thus maintaining the torque curve higher than it normally would, and creating more horsepower as RPMs climb.
The boost is not used to make more torque really. It's used to extend the torque curve higher in the RPM range without adversely affecting lower RPM torque. Equal torque at higher RPM makes more power.
This would allow a Type 4 engine to be turbocharged, since typically very high compression Type 4s require a 5th stud, or other method of containing the compression. The same, I was told, goes for forced induction Type 4s. The turbo is not intended to increase cylinder pressures in the Type 4 combustion chamber. It is intended to maintain cylinder pressures past the normally aspirated torque peak RPM.
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*** Teach a Man to Fish ***
Searoy
I just read in the archive a thread called "cams vs. compression." It's not actually a thread. It's a whole damned sweater.
It let me know I'm heading the right direction with my idea, and gave me a little inspiration as well.
Webcam 111 grind. Maybe 8.0-1 is too much. Maybe 7.5:1 is better, maybe not. I'll figure on it some more.
That cam with that compression, all else accounted for, makes a torque monster that won't rev high. It won't rev high because the piston can't pull enough air into the cylinders and continue to make torque.
Add a turbo that is large enough that it creates only minimal exhaust back pressure, and has a large enough turbine that it won't provide boost until the torque curve, and thus the breathing ability of the engine, drops off. The turbos job is merely to increase the pressure of the intake manifold so that instead of more time for the air to rush in it has more force, more speed, and can fill the cylinder more over a shorter period of time, thus maintaining the torque curve higher than it normally would, and creating more horsepower as RPMs climb.
The boost is not used to make more torque really. It's used to extend the torque curve higher in the RPM range without adversely affecting lower RPM torque. Equal torque at higher RPM makes more power.
This would allow a Type 4 engine to be turbocharged, since typically very high compression Type 4s require a 5th stud, or other method of containing the compression. The same, I was told, goes for forced induction Type 4s. The turbo is not intended to increase cylinder pressures in the Type 4 combustion chamber. It is intended to maintain cylinder pressures past the normally aspirated torque peak RPM.
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*** Teach a Man to Fish ***
Searoy
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Carsten
- Posts: 67
- Joined: Thu Aug 16, 2001 12:01 am
advice on turbo set up, please
Dan: well summed up on the above posting...
temps in Fahrenheit: 86*-95* F on a 68*F day.
yes its injected, specs: 2276, S/F 44x40, 8.8:1, Haltech F9, modified Td04HL-15G turbo.
Its my daily driver...
all I can say to Searoys and his ramblings is: Do it. build that engine.
For the others that want a reliable powerfull turbo engine: Match the turbo to your engine size, boost and rpm range. And intercool it.
Carsten
temps in Fahrenheit: 86*-95* F on a 68*F day.
yes its injected, specs: 2276, S/F 44x40, 8.8:1, Haltech F9, modified Td04HL-15G turbo.
Its my daily driver...
all I can say to Searoys and his ramblings is: Do it. build that engine.
For the others that want a reliable powerfull turbo engine: Match the turbo to your engine size, boost and rpm range. And intercool it.
Carsten
-
John
advice on turbo set up, please
[QUOTE]Originally posted by Searoy:
Stock internals will have a hard time keeping up with serious torque and power at lower RPM.
If it can keep up at low rpm, what makes you think it will be able to at a higher rpm? Why build a turbo setup to kick in at 4500 or 5000 rpm, when you rarely drive it at or above that rpm level on the street (except when racing it). It just defeats the purpose of a street turbo setup.
Stock internals will have a hard time keeping up with serious torque and power at lower RPM.
If it can keep up at low rpm, what makes you think it will be able to at a higher rpm? Why build a turbo setup to kick in at 4500 or 5000 rpm, when you rarely drive it at or above that rpm level on the street (except when racing it). It just defeats the purpose of a street turbo setup.
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Bobby74
- Posts: 1747
- Joined: Wed Feb 21, 2001 12:01 am
advice on turbo set up, please
Hello,
A friend of mine just bought a mid 90's Toyota MR2 with the Twin inlet Turbo. What size do you suppose it is? I could only read Toyota 225 (I believe it said). My point is; since I was so impressed looking at this mid-engine sleeper, my friend ACTUALLY let me drive it! Well, it kicks in and Kicks A$$ at about 4-5K up to 7K is how high I took it... and its also a 2.0L so this might be another answer for the turbo donor search
... I'm concidering finding a little older MR2 Turbo for this, in the future. Granted his car is EFI and computer controlled gobilty gook.
Best reguards,
Bobby
A friend of mine just bought a mid 90's Toyota MR2 with the Twin inlet Turbo. What size do you suppose it is? I could only read Toyota 225 (I believe it said). My point is; since I was so impressed looking at this mid-engine sleeper, my friend ACTUALLY let me drive it! Well, it kicks in and Kicks A$$ at about 4-5K up to 7K is how high I took it... and its also a 2.0L so this might be another answer for the turbo donor search
... I'm concidering finding a little older MR2 Turbo for this, in the future. Granted his car is EFI and computer controlled gobilty gook.Best reguards,
Bobby
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Searoy
- Posts: 2869
- Joined: Thu Aug 23, 2001 12:01 am
advice on turbo set up, please
Because the turbo is not increasing the maximum torque, it's maintaining the maximum torque figfure as RPMs climb, making more horspower. For those who have forgotten, 150 ft/lb of torque at 6000 RPM makes more horsepower than 150 ft/lb of torque at 2500 RPM.If it can keep up at low rpm, what makes you think it will be able to at a higher rpm? Why build a turbo setup to kick in at 4500 or 5000 rpm, when you rarely drive it at or above that rpm level on the street (except when racing it). It just defeats the purpose of a street turbo setup.
The stck internals can withstand the strees because it is not increasing the torque number, but rather is maintaining it. If it can handle 150 ft/lb of torque at 2500 RPM it can sure handle it at 6000 RPM.
And I specified a turbo that kicks in at 4000, I think. Read the top of the thread.
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*** Teach a Man to Fish ***
Searoy
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cj011
- Posts: 287
- Joined: Mon Feb 26, 2001 12:01 am
advice on turbo set up, please
heres my idea for your turbo setup. get a forged stock stroke crank with counterweights, put shorter than stock rods to bring up the rod speeds,, forged pistons with total seal second rings and lighten the hell out of the pistons and valve train. get your crank and rod cryrogenic treated, spelling is off and the pistons teflon coated, yes it adds to the price but your motor will run cooler and stronger. as for the heads run valve sizes like 44x40 or 42x42, and keep the ports mild, but remove alot of material from behind the valves and on the exhaust with straight angles, reason is smaller ports with alot of work behind the valve will create a huge flow at low levels and high. screw the aircooled idea and add water pockets to the heads and cylinders, i love aircooled but for big boost this helps cooling and your motor alive. if you are tight on space, inject methanal or water for cooling, it takes considerably less space and can be set in at certain boost levels. use the t04 turbo with smaller ratios, yes off the line you will not torque as much but it will come on like hell. turbo keith at cal look has 1915 with to4 and runs 10.3s with a mild trans. oh and run a mild duratin cam like something similar to engle 120 or 110. remeber this putting on a turbo with little or no motor work is asking for detonation and motor death. oh yea on the combustion chamber and piston tops, get all of the rough edges smoothed and semi polished, it stops heat spots. and computer balance the whole motor, not doing this is throwing away motor longevity. hope this helps, chris.