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I do not really understand the problem, the LT1 makes almost the same amount of torque as a L98 330 ft/lbs compared to 340 ft/lbs. It is a flat torque curve compared to the peakier torque curve of the L98 so the L98 appears to hit harder when in reality it does not. Just change the torque converter to be around a 2000 stall or change the gears to something slightly more aggressive. You will have just as much low end power as a L98 and it will not be rev happy on the highway. You can still shift at just as you do now.
I already showed that to him in another thread. He don't "get it". Trust me...you want to leave this one alone. "He's got this!"
I do not really understand the problem, the LT1 makes almost the same amount of torque as a L98 330 ft/lbs compared to 340 ft/lbs. It is a flat torque curve compared to the peakier torque curve of the L98 so the L98 appears to hit harder when in reality it does not. Just change the torque converter to be around a 2000 stall or change the gears to something slightly more aggressive. You will have just as much low end power as a L98 and it will not be rev happy on the highway. You can still shift at just as you do now.
Here is the dilemma, I am using 3.42 gears on an M6 and I want more SOTP torque WITHOUT having to lower the gears in order to force my motor to operate at higher RPM. This is why I want to build the motor to behave like an L98.
Yes, the LT1 has the same torque as the L98 but don't forget, the LT1 has higher compression than an L98! Give an L98 the same compression as my LT1 OR, allow me to throw on a TPI intake and L98 camshaft and you will see how much higher that torque curve shifts up the curve! This is where I am debating on whether or not to go hella crazy and spend the money to get a TPI intake on my LT1 and to use the necessary camshaft with all other supporting modifications!
The easier route is to keep my intake and have a custom camshaft made to give me something close to what I seek. Then again, if I can can get my LT1 torque curve to peak like the L98 at a much higher level, AND use a custom grind like the ZZ4 on my LT1, I should be plenty happy with the build. Again, this will likely give me more headaches, and the engine builder, and the custom cam maker, to figure out how the hell to build an LT1 correct with a TPI intake. The L98 is the reference but everything else is unknown from there...
I do not really understand the problem, the LT1 makes almost the same amount of torque as a L98 330 ft/lbs compared to 340 ft/lbs. It is a flat torque curve compared to the peakier torque curve of the L98 so the L98 appears to hit harder when in reality it does not. Just change the torque converter to be around a 2000 stall or change the gears to something slightly more aggressive. You will have just as much low end power as a L98 and it will not be rev happy on the highway. You can still shift at just as you do now.
Here is the dilemma, I am using 3.42 gears on an M6 and I want more SOTP torque WITHOUT having to lower the gears in order to force my motor to operate at higher RPM. This is why I want to build the motor to behave like an L98.
Yes, the LT1 has the same torque as the L98 but don't forget, the LT1 has higher compression than an L98! Give an L98 the same compression as my LT1 OR, allow me to throw on a TPI intake and L98 camshaft and you will see how much higher that torque curve shifts up the curve! This is where I am debating on whether or not to go hella crazy and spend the money to get a TPI intake on my LT1 and to use the necessary camshaft with all other supporting modifications!
The easier route is to keep my intake and have a custom camshaft made to give me something close to what I seek. Then again, if I can can get my LT1 torque curve to peak like the L98 at a much higher level, AND use a custom grind like the ZZ4 on my LT1, I should be plenty happy with the build. Again, this will likely give me more headaches, and the engine builder, and the custom cam maker, to figure out how the hell to build an LT1 correct with a TPI intake. The L98 is the reference but everything else is unknown from there...
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Originally Posted by Phoenix'97
Then again, if I can can get my LT1 torque curve to peak like the L98 at a much higher level, AND use a custom grind like the ZZ4 on my LT1, I should be plenty happy with the build.
Uh...Mad-Scientist Guy...If you LEAVE the LT1 intake on, it WILL peak at a "much higher level".
If you are FOR REAL, you need to get your terminology straight and/or be MUCH more precise with this mumbo-jumbo. If you ARE for real, you contradict yourself all day long...which makes you sound schizophrenic.
Mind you, we don't discount that probability.
I have to ask (again, if you are for real) why you take advice on what cam NOT TO USE from "another forum" when that SAME forum would steer you AWAY from an L98 intake.
They don't understand your desire to maximize idle to 1500 rpm torque -- like WE do. We understand it well because we ALL focus on that rpm...as well as driving our vettes in the snow...as well as avoiding having a second vehicle...as well as trolling multiple forums in pursuit of solutions to "build" a motor -- without actually making it powerful.
Now...take a DEEP breath and ask yourself if the paragraph above doesn't meet your "in all sincerity" criteria? If not, how much of it do you see as coming STRAIGHT from posts YOU'VE made? I say all of it.
If you disagree, you need to reread all the rambling, incoherent, contradictory, combative stuff YOU'VE written.
In short, you are ALL OVER THE PLACE AND LACK CREDIBILITY BECAUSE OF IT.
There is a DIFFERENCE between asking questions and learning vs. acting like everyday is a new ACTUAL build. And we know you are NO WHERE NEAR doing anything.
In ALL sincerity, if you are going to "ping-pong" yourself between forums of people that ALL think you are nuts, don't be surprised if we end up enjoy TREATING you like a ping-pong ball!
Yes, the LT1 has the same torque as the L98 but don't forget, the LT1 has higher compression than an L98!
So what? The LT1 is a better engine in every possible way than the L98 ever was. It has the same torque (although there's no reason anyone should care about torque at the crankshaft), more power, a much wider usable powerband, and better economy.
Give an L98 the same compression as my LT1 OR, allow me to throw on a TPI intake and L98 camshaft and you will see how much higher that torque curve shifts up the curve!
There are reasons that an L98 can't safely operate at LT1 compression ratios. One major reason is that intake. Read that again. The resonant tuning effect of the TPI intake tries to pack the cylinders with air/fuel the most at the same rpms as the cam creates peak torque. The result is cylinder pressures that are over the moon high, ergo you get detonation very quickly. But at other rpms - especially anything higher - the engine has very poor volumetric efficiency and low cylinder pressures, ergo much less power.
By switching to a short-runner intake that doesn't ram-tune at any usable rpm but also doesn't create a restriction, GM was able to increase the CR quite a bit. In the LT1 you have an engine that can achieve much more even volumetric efficiency across a wide range of speeds, and because of the higher CR (among other things) it gets better fuel economy too.
The L98 is the reference but everything else is unknown from there...
This, right here, is the root of all your problems. Anybody that thinks the L98 is a good reference to build a motor is starting off on the wrong foot. You have chosen a reference that is demonstrably inferior to its successor in every possible way.
So what? The LT1 is a better engine in every possible way than the L98 ever was. It has the same torque (although there's no reason anyone should care about torque at the crankshaft), more power, a much wider usable powerband, and better economy.
The LT1 and L98 get the same fuel economy! Only the LS1 sees a bump in fuel economy but this is owed to the combo of higher compression (LT1) and it's mid-length runner intake (quasi-L98). The LT1 is only "better" than the L98 in terms of compression, but that is it. The LT1 is great for racing but I notice the lack of torque on the low end with my driving style and it sucks to have to rev higher to get more torque. I have no plans to swap in an L98 into my car because it would require a host of additional mods to get it to work right. The logical solution is to build my LT1 like an L98 which involves the TPI intake, and then using an L98 style camshaft knowing what is involved with TPI motors.
Originally Posted by MatthewMiller
There are reasons that an L98 can't safely operate at LT1 compression ratios. One major reason is that intake. Read that again. The resonant tuning effect of the TPI intake tries to pack the cylinders with air/fuel the most at the same rpms as the cam creates peak torque. The result is cylinder pressures that are over the moon high, ergo you get detonation very quickly.
Are you sure the compression issue is not a result of cooling and head material? The LT1 has reverse-flow cooling which permits a higher compression ratio in combination with aluminum heads, from what I have managed to learn about it. So, I don't see a TPI intake being the sole issue on an LT1 so long as it has the correct camshaft and tuning to allow for it to operate just as smooth as it would with its short runner intake manifold and complimentary camshaft. Am I wrong in this assumption?
Originally Posted by MatthewMiller
But at other rpms - especially anything higher - the engine has very poor volumetric efficiency and low cylinder pressures, ergo much less power. By switching to a short-runner intake that doesn't ram-tune at any usable rpm but also doesn't create a restriction, GM was able to increase the CR quite a bit. In the LT1 you have an engine that can achieve much more even volumetric efficiency across a wide range of speeds, and because of the higher CR (among other things) it gets better fuel economy too.
So, what stands to be gained from an engine with a higher compression ratio, say around 12 using 102 octane bio-fuel using a TPI intake? From what I see with the stock L98 torque curve versus the LT1, if you bump up that torque curve for the higher compression ratio AND you give the motor a very mild baby cam to increase power along it's usable torque curve, I will have myself an LT1 that gives me my instant low end power from idle on up to the mid-range where it will start to drop from around 3,000/4,000 RPM BUT that same curve for the TPI intake and complimentary camshaft will still be higher, until 4,000/5000 RPM, than had I stayed with my LT1 intake and complimentary Lloyd Elliot camshaft. This is where my notion of performance ends with a daily driven street car and that SOTP feel that I am seeking. Does everyone get the gist of what I am looking for out of my LT1?
Last edited by Phoenix'97; 11-15-2017 at 09:59 AM.
Not for the same power levels! The stock LT1 makes 55hp more than the L98, yet still manages 1mpg better in EPA-rated fuel economy. In the real world, the mpg difference is considerably higher than that. Hell, my 396 with seriously ported LT4 heads and a cam with lots of overlap still manages 26mpg on the highway, empirically tested. And it's faster than a stock C6 Z06.
Only the LS1 sees a bump in fuel economy but this is owed to the combo of higher compression (LT1) and it's mid-length runner intake (quasi-L98).
That is simply not true. Runner length cannot improve fuel economy. You don't understand how any of this works! Fuel economy is achieved by making the same power with less fuel (i.e., a better brake specific fuel consumption or BSFC). A tuned intake can only force more air/fuel into the engine at a certain rpm, which does NOT increase BSFC. In fact, by requiring a lower CR, it makes BSFC worse over all, at any any rpm other than that which it is tuned for (and on the street, that's almost any time you're driving). CR does indeed generally improve mpg, but the TPI is always going to be at a disadvantage because it must run a lower CR than the LT or LS, all else being equal.
The LT1 is only "better" than the L98 in terms of compression, but that is it. The LT1 is great for racing but I notice the lack of torque on the low end with my driving style and it sucks to have to rev higher to get more torque. I have no plans to swap in an L98 into my car because it would require a host of additional mods to get it to work right. The logical solution is to build my LT1 like an L98 which involves the TPI intake, and then using an L98 style camshaft knowing what is involved with TPI motors.
That's not a logical solution at all. You've talked about building a 396 before. Just do that and keep your stock cam and intake and you'll move your whole curve lower in rpm, you'll still have a lot more power than an L98, and you'll be getting loads better fuel economy.
Are you sure the compression issue is not a result of cooling and head material?
Yes, especially considering that later L98s also had aluminum heads. The cooling was a minor factor, but only a minor one.
Am I wrong in this assumption?
Yes. You should not be assuming anything! You should be basing your decisions on facts, not assumptions. The internet mythology of the TPI motors being "torque monsters" is just that: mythology.
So, what stands to be gained from an engine with a higher compression ratio, say around 12 using 102 octane bio-fuel using a TPI intake?
Is this a serious question? Whatever fuel you use, you can always build a higher CR and make more power with an LT-style intake than with a TPI intake, if all else is equal. There's no other way to say it. If you can safely build to 12:1 with that fuel and a TPI intake, then you can safely build to 13:1 or higher with a short-runner intake. Stop making this complicated.
Lloyd can answer your question about low end torque, so why are you starting threads here and everywhere about your question?
I am not going to pester Lloyd when I am not ready to buy from him. Plus, I am still researching what it is that I am going to do with my car, and having to sift through unreliable jokes for advice or serious responses. I am not trolling here, and asking questions does help you to learn.
...the TPI is always going to be at a disadvantage because it must run a lower CR than the LT or LS, all else being equal.
Well, haven't guys tried to bump up the compression on their L98s with success?! Unless they were using LT1 style intake manifolds. I still fail to understand why a TPI intake manifold can not handle higher compression if the motor is tuned properly with the right choice in camshaft and higher octane fuel.
Also, there has to be something said for the LS1 intake manifold with longer runners than the LT1 and providing better lower end torque than the LT1. This is why my logic is where it stands right now.
Well, haven't guys tried to bump up the compression on their L98s with success?! Unless they were using LT1 style intake manifolds. I still fail to understand why a TPI intake manifold can not handle higher compression if the motor is tuned properly with the right choice in camshaft and higher octane fuel.
Of course you can bump compression if you choose a cam with more overlap and duration. But you can do that with any engine, including an LT1! Again, all else being equal, an LT1-style intake allows significantly higher static CRs than a TPI, because the TPI will cause a spike in cylinder pressures at its tuning frequency.
You need to understand the difference between static CR and dynamic CR. Static CR is a simple computation of total cylinder volume with the piston at BDC divided by the volume at TDC. Dynamic CR takes into account valve timing. If you increase cam duration and overlap, and particularly if you close the intake valve later, you lower your dynamic CR even if static CR stays the same. So when you say you can raise the static CR of an L98 after you install a different cam, that's true only because the cam you'd presumably install has a later intake valve closing event. So by installing the new cam, you've lowered dynamic CR, and by increasing the static CR you've gained back the dynamic CR that you lost.
Now, the next question here is, "What happens to my fuel efficiency at low rpm with the bigger came and higher static CR (which just retained the original dynamic CR)?" The answer: not a damn thing! The motor only cares about dynamic CR. So by using the later-closing cam and recouping the dynamic CR with a higher static CR, you are back where you started in terms of fuel economy and idle characteristics. You'll just have a higher power potential at higher rpms. But the problem with the TPI intake is that just when that fancy bigger cam is kicking in to provide you with sweet power gains in the higher end of the power curve, your intake is now creating a negative pressure wave on the back of the intake valve instead of a positive pressure. So now, instead of packing the cylinder with extra air like it does at, say, 3000rpm, it's actually starving the engine of air.
So given all of that, you can do the exact same thing with a short-runner intake: use a longer-duration cam to make more power up high, and then recoup the dynamic CR by raising static CR. And again you'll retain stock-like fuel economy and idle quality. But without the TPI's negative pressure wave restriction, you'll make a ****-load more power at the top end. IOW, the same mods come with the same negative effects (none), but the benefits are much bigger.
Also, there has to be something said for the LS1 intake manifold with longer runners than the LT1 and providing better lower end torque than the LT1. This is why my logic is where it stands right now.
Well, the LS intakes are roughly half the length of a TPI intake. Their negative-pressure tuning is still way higher in the rpm range than any typical LS1 will be run. That's why they don't hurt performance on the top end. The TPI intake length unfortunately creates all of its drawbacks (literally and figuratively - hah!), right where you'd like to create gains with aftermarket upgrades. It wasn't a problem in the 1980s, because the factory engines were saddled with teeny cams and no rpm potential, so the long runners weren't hurting the stock performance. And emissions requirements were still somewhat hobbling CRs in stock engines, so it wasn't a sacrifice to build engines at only 9:1 static. And GM didn't care if you wanted to modify the engine 30 years later.
So your logic is flawed. The question you need to ask yourself is: why have no OEMs or race engine builders used intakes with TPI runner lengths in the past 25 years? There's a very, very good reason for that!
So your logic is flawed. The question you need to ask yourself is: why have no OEMs or race engine builders used intakes with TPI runner lengths in the past 25 years? There's a very, very good reason for that!
I am not ashamed of flawed logic, it can always be remedied. The question I now have is, with regards to race engine builders and GM trying to crank out higher HP #s, it is no wonder that the TPI intake is not considered. However, when a daily driver is concerned with the emphasis of trying to maximize lower end torque with limits on RPMs to 5000, wouldn't the TPI intake and it's draw back not be a problem anyways? I don't take my car to the track and I care nothing about maximum top end power, just low end to mid-range on up to 5000 maximum. Would the TPI intake then serve my build purpose?
I am not ashamed of flawed logic, it can always be remedied. The question I now have is, with regards to race engine builders and GM trying to crank out higher HP #s, it is no wonder that the TPI intake is not considered. However, when a daily driver is concerned with the emphasis of trying to maximize lower end torque with limits on RPMs to 5000, wouldn't the TPI intake and it's draw back not be a problem anyways? I don't take my car to the track and I care nothing about maximum top end power, just low end to mid-range on up to 5000 maximum. Would the TPI intake then serve my build purpose?
I don't know why you'd artificially limit yourself to 5000rpm, when your stock intake already allows higher than that. That's just a silly goal within the context of a Corvette. And here is where people get frustrated with your questions. You are artificially painting yourself into a stupid corner. How about if you build an engine that has more power than can be harnessed by the tires in first gear (or maybe even second gear) AND it also has the flexibility to run well and make lots of power up to 6000rpm or higher? For the same price or less, and with a whole lot less hassle?! For the same cost in both money and time, you could just assemble a 383 or 396, use your stock intake, a smallish aftermarket cam, and have a much more flexible engine.
I guess to answer your question, no, the TPI is still not the best intake from 500-5000rpm. It still will hobble the engine's power at 5000rpm, and it will still require less CR than the same motor with an LT1 intake. So you'll get that impressive feeling little torque spike, but you will actually have worse fuel economy and less power, even within 5000rpm. If you were local to me, I'd love to give you a ride in my 396 C4 with ported LT4 heads and a cam you would consider "big." I can shred street tires even in second gear, it has "torque" from off idle, and pulls hard to 6k. I can still lug 6th gear below 60mph, and I can lug 4th down to 25mph or so. If you had my engine but a smaller cam with an earlier intake closing, you'd have the tow-truck engine you crave, and it would be way more flexible and get better fuel economy too.
i met you you In person, rode in your car auto crossing and have a great amount of respect for you. You are one of the most knowledgeable members here and just a great person in general!
But in all due respect, be done with it.
No when to fold old em buddy....this is a huge bundle of wasted time for you and the other members.
I don't know why you'd artificially limit yourself to 5000rpm, when your stock intake already allows higher than that. That's just a silly goal within the context of a Corvette. And here is where people get frustrated with your questions. You are artificially painting yourself into a stupid corner. How about if you build an engine that has more power than can be harnessed by the tires in first gear (or maybe even second gear) AND it also has the flexibility to run well and make lots of power up to 6000rpm or higher? For the same price or less, and with a whole lot less hassle?! For the same cost in both money and time, you could just assemble a 383 or 396, use your stock intake, a smallish aftermarket cam, and have a much more flexible engine.
I artificially limit myself to 5000 RPM because there is no need to exceed this, and speed limit wise I am already at 50 mph in second gear with my 3.42 rear axle. This is why I am leery about the stroker idea, unless I decide to screw around with a much higher gear like the 2.73. I am still having a hard time believing that the stroker option would be more fuel efficient in terms of city stop-and-go idling, which is why I figured a custom grind by Lloyd would be the better option and possibly better for fuel economy with regards to city driving. I want more lower end torque than what my current stock camshaft offers, and with my stock intake which is optimized for higher RPM performance, I need to find a camshaft that will make my LT1 behave like the L98, give me my SOTP feel from idle on up to 5000 RPM, and be easy on fuel during the city drive.
So, if the stroker is supposed to be the better choice, it will require some really good data. As far as the TPI intake goes, I am reluctant to say I was proven wrong.
Originally Posted by MatthewMiller
I guess to answer your question, no, the TPI is still not the best intake from 500-5000rpm. It still will hobble the engine's power at 5000rpm, and it will still require less CR than the same motor with an LT1 intake. So you'll get that impressive feeling little torque spike, but you will actually have worse fuel economy and less power, even within 5000rpm. If you were local to me, I'd love to give you a ride in my 396 C4 with ported LT4 heads and a cam you would consider "big." I can shred street tires even in second gear, it has "torque" from off idle, and pulls hard to 6k. I can still lug 6th gear below 60mph, and I can lug 4th down to 25mph or so. If you had my engine but a smaller cam with an earlier intake closing, you'd have the tow-truck engine you crave, and it would be way more flexible and get better fuel economy too.
Last edited by Phoenix'97; 11-15-2017 at 03:31 PM.
Why not start with gears, see how you like them and then go with a LE cam.
The only direction I will likely go with gears is higher, not lower. This is why I am going crazy with wanting an LT1 that acts like an L98, I won't need a lower gear ratio if my torque curve shifts to the lower and mid range. If I get the motor stroked, I will probably end up using a 2.73 gear ratio to compensate. This is a balancing act...
The only direction I will likely go with gears is higher, not lower. This is why I am going crazy with wanting an LT1 that acts like an L98, I won't need a lower gear ratio if my torque curve shifts to the lower and mid range. If I get the motor stroked, I will probably end up using a 2.73 gear ratio to compensate. This is a balancing act...
Are you still planning on using this combo in deep snow ?
11-14-2017, 01:01 PM
