Maybe Bruce can help me here

[marleyskater420]

Ok, so I have been DIEING to know what would happen in this situation..

Let say that you have 2 engines, one a I4,and one a V8, the I4 is 2l and the V8 is 6l. Both engines start off with lets say 200hp, or just x for hp.If you put a turbo that would flow 600hp, on each engine, both having the same identical turbo that flows 600hp, what engine would make more power? Both these engines are perfectly designed, so there is no bottlenecks anywhere, so negate any real-world situations. What engine would get more hp and most importantly WHY?

Also, how come import engines with these 61mm wheels and whatnot, make over 500whp and our cars have a horrible time doing so with the same size wheels?

Also, if you have the same turbo, and put it on 2 engines, like the 2l and the 6l, in real life, what would make more power?

What about if you took one of our stock turbos that only give around 245hp stock or so, and ran the proportionatly same boost, on a smaller engine(after factoring in compression ratio and whatnot, so our 14.5psi would be x psi to them, so all is equal) why do they make more power?

Do turbos work that the size and flow of the turbo is proportionate to what size engine it is put on? So a 600hp turbo for a 4l wont give 600hp for a 6l ?

Help me understand about putting the same turbo on different sized engines and how it works and the effects.

thanks

 

[crownvic96]

man this is going to be a can of worms. couple things i'll comment on though.

unless you are talking about like a last gen supra, 300zx or something of the like that came from the factory with a strong bottom end you're not going to get 500+ hp out of a 4 banger and turbo unless you do some serious modifications to the head, fuel system and bottom end to support that much horsepower. also most cars that react well to turbos that are imports are newer and have more engineering, electronics and technology all around to help optimize those motors and get good power. its kind of like saying well my 87 camaro z28 has a 350 why am i not making the same power as those '00 z28's. we both have 5.7l motors......

for your I4 vs V8. the V8 is going to have a broader more usable power band and be less peaky than the I4 because it has more cylinders firing more often and is displacing more air to help the turbo spool up to help make more power...

but for the most part there is going to be too many assumptions, variables and what ifs in your questions for some catch all answer for you.

 

[buickpower]

well if the turbos flow enough for 600hp, then both engines would theoretically make that. However, the 2L is going to have to rev significantly higher to do so, since power is how fast you do work, and less work is done on at the same engine speed with smaller pistons. The 6L will have alot more torque, especially at a sane rpm, because torque and displacement are directly related.

Import motors often make impressive power numbers, at least on the dyno due to the fact that they often have 4 valve heads, which flow very well, and the fact that they rev so high. The high revving thing goes back to what i said about power being the time rate of work. Since torque is directly related to cylinder filling, and power is torque times rpm/5252, you can see that an engine making alot of torque (good cylinder filling due to head design and turbo) at high rpm will make alot of power, and that is what some of the imports do. Torque is a different story however, like I said earlier, as a larger engine will generally make both more peak torque and more average torque.

Basically there are three ways to make more power with an engine, which is an energy conversion device. First, you can increase the size of the energy conversion device (make the motor bigger), second, you can speed up the energy conversion process by spinning the engine faster (assuming the engine can breathe well at that rpm) or having the engine fire more times per revolution (2 strokes), lastly, you can increase the work done per cylinder per power stroke, and this is basically an umbrella statement that includes anything that will improve engine breathing (high volumetric efficiency) to fill the cylinder better (which results in higher average cylinder pressure), including better heads, adding a turbo .....etc.

 

[marleyskater420]

WHOA WHOA WHOA..hold on a minute..

THIS is the situation I wanted to have answered..if the I4 and V8 were both 100% efficient, and the turbo flowed 600hp worth, what engine would make more power, or would they both make the same hp.but the thing is,they both use the SAME turbo, so it will flow enough for 600hp, but does it make 600hp on the 6l, and over that on the 2l since the VE is increased so much?

Remember, these are hypothetical engines that are 100% efficient.

My thoughts were that since the turbo flowed 600hp for the 2l, it will be choked by all the exhaust gas the 6l will push out, so the turbine will be inefficient because of all the gas trying to exit the turbo that was geared for a 2l.

I also thought that since the I4's VE will be greatly increased, so will the power because it will be more air to burn..

I also thought that even though there is more air in the I4,and the VE is up, the same amount of air is going to be in the V8,it will just have less VE because there are 2x the cylinders.

That was hypothetical, this is real world stuff..

Now..are turbos that make 600hp for 6l's going to be 800hp turbos for 2l's? I know a turbo is load based for its rating, but if it makes 600hp for a 6l,then you are going to shoving in WAY more air into a 2l, and more air in a smaller space is more hp,right?This in reference to real world situations.

I mean if you a vortech SC that added 100hp on a LS1, and added it to a 4.6, theoretically, should it make more hp, because there is more air being shoved in a smaller space than the 5.7?

I mean if I took my TE45, would it make more power on a I4,assuming it can take it?And why?

 

[bruce]

Originally posted by marleyskater420
Ok, so I have been DIEING to know what would happen in this situation..

Let say that you have 2 engines, one a I4,and one a V8, the I4 is 2l and the V8 is 6l. Both engines start off with lets say 200hp, or just x for hp.If you put a turbo that would flow 600hp, on each engine, both having the same identical turbo that flows 600hp, what engine would make more power? Both these engines are perfectly designed, so there is no bottlenecks anywhere, so negate any real-world situations. What engine would get more hp and most importantly WHY?

Also, how come import engines with these 61mm wheels and whatnot, make over 500whp and our cars have a horrible time doing so with the same size wheels?

Also, if you have the same turbo, and put it on 2 engines, like the 2l and the 6l, in real life, what would make more power?

What about if you took one of our stock turbos that only give around 245hp stock or so, and ran the proportionatly same boost, on a smaller engine(after factoring in compression ratio and whatnot, so our 14.5psi would be x psi to them, so all is equal) why do they make more power?

Do turbos work that the size and flow of the turbo is proportionate to what size engine it is put on? So a 600hp turbo for a 4l wont give 600hp for a 6l ?

Help me understand about putting the same turbo on different sized engines and how it works and the effects.

thanks

The 6L would win.
Why?.
Area under the curve.

You talking HP, and it's about Torque that most cars actually need.
You can use transmission gearing to take advantage of whatever gear multiplication that needs to be done to move the car.

One other thing, is power per cylinder firing. The v8 would have a steady stream of power to be applied to the wheels. So there would be less Tearing of the tires as the power pulses hits it.

The old turbo F1, and 4 cyl Indy engines were all up at 1,000 HP decades ago. Getting them to live at those levels was the trick. The cylinder firing pulsations were so far apart that it literary hammered the engines apart. Look at the design of an old Miller/Offy Indy engine, and what they did to keep them together.

A little model airplane engine can make alot of instantaneous HP.

HP is based on the 5,250 RPM division correction, so that swings the HP readings in favor of the higher revving engines. For comparison, a 6l engine, at 5,250 RPM at 500 HP, is alot more useful then a 3l engine making 500 HP at 10,500 RPM, when both use a 4 Spd tranny.

That help?.

There's a few other issues that'd fill a couple text books with other details. But, in a nutshell, I think that pretty well covers things.

 

[marleyskater420]

Re: Re: Maybe Bruce can help me here

Originally posted by bruce
The 6L would win.
Why?.
Area under the curve.

You talking HP, and it's about Torque that most cars actually need.
You can use transmission gearing to take advantage of whatever gear multiplication that needs to be done to move the car.

One other thing, is power per cylinder firing. The v8 would have a steady stream of power to be applied to the wheels. So there would be less Tearing of the tires as the power pulses hits it.

The old turbo F1, and 4 cyl Indy engines were all up at 1,000 HP decades ago. Getting them to live at those levels was the trick. The cylinder firing pulsations were so far apart that it literary hammered the engines apart. Look at the design of an old Miller/Offy Indy engine, and what they did to keep them together.

A little model airplane engine can make alot of instantaneous HP.

HP is based on the 5,250 RPM division correction, so that swings the HP readings in favor of the higher revving engines. For comparison, a 6l engine, at 5,250 RPM at 500 HP, is alot more useful then a 3l engine making 500 HP at 10,500 RPM, when both use a 4 Spd tranny.

That help?.

There's a few other issues that'd fill a couple text books with other details. But, in a nutshell, I think that pretty well covers things.

Id like to learn more, could I ever get in contact with you over the phone to talk, I would love to have a conversation about this.

If its cool, can you pm me your number cuz it would make my day to be able to understand this more.

Thanks!

-Tyler

 

[bruce]

Re: Re: Re: Maybe Bruce can help me here

Originally posted by marleyskater420
Id like to learn more, could I ever get in contact with you over the phone to talk, I would love to have a conversation about this.

Email sent

 

[rtviper]

Bottom line is there is no replacement for displacement if you use the same mods on a big motor and a small motor. Your example of a 2l motor and a 6l motor with no bottle necks to making power will probably have the 6l motor making 600 hp without the turbo and the 2l motor using the turbo to get there. Now you add boost to the 6l motor and you go up from there. Its like when you read of a stage II 272 cube motor making 650 hp using 15lbs boost. The 2l motor will need a lot more mods to heads, intake,etc etc to get close to the baseline of the 6l motor. Reading about a small import motor making huge power is like looking at the large cube motors making 2500 hp and up. Same amount of work and money with huge differences in results

 

[buickpower]

THIS is the situation I wanted to have answered..if the I4 and V8 were both 100% efficient, and the turbo flowed 600hp worth, what engine would make more power, or would they both make the same hp.but the thing is,they both use the SAME turbo, so it will flow enough for 600hp, but does it make 600hp on the 6l, and over that on the 2l since the VE is increased so much?

You answered your own question, again. the horsepower rating comes from how much air mass the turbo can flow, period. Power depends on how much fuel and air you can burn TOTAL per amount of time. So even though the smaller engine has a higher VE, it is still less overall quantity per unit of time, which again is the key. In essence the 2 liter's higher VE is only making up for what it lacks in total quantity, so the 2L would HAVE TO have higher VE to produce the SAME amount of power. So if the turbo can only flow X lbs. of air maxed out, and you have enough fuel to keep the desired A/F ratio, then the 600hp will be all it can make, regardless of engine size or VE.

As far as the choked turbine idea goes, the amount of exhaust gases will be close to the same since both engines would have to burn the same amount of TOTAL fuel per unit of time, however this may not be the perfect case because the four cylinder has fewer input pulses per revolution, as I mentioned previously.

Now..are turbos that make 600hp for 6l's going to be 800hp turbos for 2l's? I know a turbo is load based for its rating, but if it makes 600hp for a 6l,then you are going to shoving in WAY more air into a 2l, and more air in a smaller space is more hp,right?This in reference to real world situations.

you aren't shoving more air, just shoving it into a smaller space, and no just shoving it into a smaller space does not make more power necessarily, if the engines again are again consuming the same TOTAL amount of air.

I mean if I took my TE45, would it make more power on a I4,assuming it can take it?

no, it wouldn't, but since you say this is now a real world scenario, that would totally depend on heads, cam, blah blah blah

 

[buickpower]

To put it differently, say you have a hose that flows a constant amount of water in one minute ( like the turbo). You can either fill 8 large buckets halfway ( like the V8 engine), or you can completely fill 4 smaller buckets (like the 4cyl engine) in order to have the same amount of flow. Since the 4cyl engine is smaller, it has to more completely fill it's cylinders to have the same amount of flow. This means that it has a higher VE, but is still flowing the same amount as the V8, so the power will be the same. But, like I said before, the larger engine will still make more torque.

 

[rtviper]

Using the water hose example you are putting the 6L motor at a disadvantage. It has the potential to be filled to the top while the 2L motor is filled to the top. If you assume the 2L will take all the volume from the 600 hp turbo you have a small motor making max hp and the 6L is at 1/2 its output. Put a 900 turbo in the equation and the 2L cannot take the extra volume and the 6L will continue to put out additional power as it will fill its cylinders more completely. I still think the 6L is putting out more power from the start to maximum boost with the 600 hp turbo. In the n/a state the 6L will have way more power before boost is added. Just because you use a 600 or 900 or 1000hp turbo it doesnt mean the motor will put out that much power

 

[marleyskater420]

Thank you all for the answers.

Thank you Bruce for taking the time to talk to me, even when I talked in circles at moments.

 

[bruce]

Originally posted by marleyskater420
Thank you all for the answers.

Thank you Bruce for taking the time to talk to me, even when I talked in circles at moments.

Your welcome,

 

[VadersV6]

If a 500 cubic inch motor and a 150 CI motor were both 100% efficient, and running the same turbo thats capable of flowing 600hp worth of air, the bigger motor would shine in every area.
A 4cyl 150 inch motor would need heads that can flow 600hp worth of air, efficiently. Fitting a port/valves that size on a small motor is not easy. Even if it is a 4valve motor. You can get ports that can flow 600 hp worth of air. But, they are extremely inefficient at lower rpms because they will be the size of a storm drain. It would have to be spun to ridiculous rpms for the air charge to reach sonic speed (which is where torque always peaks). In other words, both the 500 inch and 150 inch motors can have heads and turbos that flow an efficient 600hp worth of air, but the smaller engine can only displace a third (wild guess) of the amount of air that the 500 inch motor can. So, the only way to get that extra 3 times the air in, is to have ports, of the proper length, where the cross sectional area is large enough to peak torque at an rpm condusive to pumping 600hp worth of air, and ultimately, spin it to that rpm. Pray to God that the oiling system and parts can hold up.
You can crank the hell out of the boost on the small motor, but now we dont have equal efficiency. Im trying to keep efficiency equal between the motors. I'm also saying that the 2 turbos flow an equal amount of air at 600hp, and the motors have the same compression.
Now you also have to have an extremely short runner to take advantage of resonant tuning. Both the huge area of the runner(not volume), and the short runner, absolutely destroy the power curve. To reach 600hp worth of air flow, the rpms would have to be ridiculous. you would probably have to peak torque at about 10,000 rpm, and the runners would have to be about 5-6 inches long, to take advantage of the stronger 3rd resonant wave. Resonant tuning works with ALL motors. Not just naturally aspirated ones. Resonant tuning also works in a very narrow range. If the runner length is condusive to timing the resonant pulse at say, 11,000 rpm, at all other rpms it will work against efficiency (this could be offset a bit with a smaller diameter runner, but we cant run one on the small motor). It will have the opposite effect. Now that you have a huge rpm band, you have an awful lot of area where the resonance is working against making power. There are points lower in the rpm band where you are getting some resonant tuning, but its worthless cause the runner diameter is so large. On the bigger motor, the runner diameter is smaller, and the runner length is kept long......because you CAN reach your 600hp goal on the bigger motor, with the longer and smaller runners. If you can keep the rpm range limited, you have less area where resonant tuning is working against you. You have a stronger curve.
I know it seems like I got off base, but I really didnt. Lets say we're pumping 600hp worth of air on both motors. But, velocity and air charge timing control the power curve.
Sure, the 150 inch motor and the 500 inch motor both can produce 600hp. But the rpm range where velocity and air charge timing are condusive to pumping 600hp worth of air, varies by a huge margin between the 2.
Ive spent countless hours of research and experimentation (ALOT of dyno pulls) with intake manifolds, and in the process learned alot more about engine dynamics than I knew back when I was an engine builder. I used to do custom intake work and modification for people all over the country. I had an article lined up for me 5.0 magazine, but I had to stop doing intake modifying, because of a hectic work schedule. Hopefully one of these days, I can pull those fluid books out, find my flow works CD, and get back on track with it. I'd love to try some things with the turbo buick. The TB intake is far from matched with the rpm band.

 

[bruce]

Originally posted by VadersV6

Now you also have to have an extremely short runner to take advantage of resonant tuning.

Resonant tuning works with ALL motors.

Resonant tuning also works in a very narrow range.

True, BUT, while they work in specific ranges, in the grande scheme of things do they actually improve the area under the curve in the areas that the engine uses?.

From what I've seen, lately, runners in a Turbo Application are about meaningless, for *our* cars. Hemholtz in off boost is an aid, but when in boost, meaningless, in *our* cars.

The latest of the SM intakes also some to prove that it's about PMP, rahter then tuned volumes.

Again, IMO.

 

[VadersV6]

Its been proven, that a longer runner will improve power under the curve, in any and all forced induction applications. All we are dealing with is pressure changes. Ambient is 14.7psi. You cram another 20psi in, and in reality you have 34.7 psi. What worked at ambient pressure will work at another pressure. Even negative pressure (vacuum).
Helmholtz occurs in an N/A form, and a forced form. The resonance characteristics change with pressure, but it is still there. Its like a spring that has been pulled back, and snapped loose. It compresses, extends, compresses, and essentially resonates. Forced induction, or simply increasing pressure, is like increasing the mass of the spring. You pull on it and snap it loose, and it will resonate like the smaller spring; just at a lower frequency.
Resonance occurs in the exhaust as well. If you crimp the exhaust half closed, and increase the pressure, the resonance is still there. Same goes for the intake.
Even though the turbo can keep making power up past the runners tuning frequency, it doesn't mean that we can't get much more out of it with the proper manifold.

 

[bruce]

Originally posted by VadersV6
Its been proven, that a longer runner will improve power under the curve, in any and all forced induction applications.

The best I've seen mentioned is a *boost* of 3-4 K/Pa. That'd be the equalilant of about 4% of 14.7 PSI, if I'm not mistaken.

The downside is that above or below the tuned improvement range, the engine is slower to change RPM, due to runner lenght.

What you've said has been proved on dynos. But, it's been my experience, that shortening the runners, and increasing the plenum size on even a stock manifold leads to a perforance gain, in car.

For every ying, there is a yang. Engineering is about comprmises. To universally state a longer runner will improve power under the curve, infers that there's no runner that's too long. The *goal* is to have an engine breathe as well as possible, and that's the exclusive realm of a true IR system <speaking N/A here, since it can't be done in a boosted application>. Which is mostly about in the T/C world meaning the more plenum the better.

 

[VadersV6]

Originally posted by bruce
The best I've seen mentioned is a *boost* of 3-4 K/Pa. That'd be the equalilant of about 4% of 14.7 PSI, if I'm not mistaken.

The downside is that above or below the tuned improvement range, the engine is slower to change RPM, due to runner lenght.

What you've said has been proved on dynos. But, it's been my experience, that shortening the runners, and increasing the plenum size on even a stock manifold leads to a perforance gain, in car.

For every ying, there is a yang. Engineering is about comprmises. To universally state a longer runner will improve power under the curve, infers that there's no runner that's too long. The *goal* is to have an engine breathe as well as possible, and that's the exclusive realm of a true IR system <speaking N/A here, since it can't be done in a boosted application>. Which is mostly about in the T/C world meaning the more plenum the better.

Yup, tuned resonance only works in a narrow range. Above or below it, it works against you. BUT, not that much farther above or below. With an engine making peak power at 6000rpm, you can actually tune a runner (that actually fits under the hood) to benefit from the 3rd, 4th and 5th wave, all in the useable rpm range. The 5th will hit at say 2000, the 4th at 3500, and the 3rd at 6000. I dont know the exact numbers here. I'm just saying that you wont make a sweet number at peak, and it will suck everywhere else. It can achieve passive supercharging at multiple points in the curve. Whats that do? It increases the area under the curve. It only takes a 13-14 inch long runner to do this.
Shortening the runners and increasing the plenum volume does not always lead to more performance. It may be the trend on the turbo regal (which doesnt obey the laws of physics I guess), but it applies to just about everything.
Of course you can have a runner too long. If you could harness the 2nd harmonic with a 40 inch long runner, it would make some killer power at 3000rpm, but the throttle body would have to be 3 feet above the engine. To get the most VE out of the motor, the runner length must be matched to the rpm range you wish to peak hp at. Like I said, the turbo is continuing to force more air in, despite the runner mismatch, but it can still gain by optimizing length. The entire point of this is to increase area under the curve. How long are the TR runners? Intake and head port combined, maybe 8 inches? That length is tuned to hit the 3rd harmonic at 11,000 rpm. You can hit the weak 4th harmonic at 8200rpm. I guess theres always the 5th at 6600rpm, but by this time, the return pulse is so weak it doesnt matter. Of course you can still make mad power with the existing technology. Just force alot of air in, no special science involved, and you can make great power. But you could still make more if it was engineered better.
By the way, this 1/2 a psi you mentioned is not the case. I gained 60rwhp on my cobra at 6800rpm, by going 2 inches shorter and altering the plenum design. Every other guy out there on the market was gaining maybe 30-40, and losing power down low. I only lost 3 lb ft. and kept the entire curve intact. That was the result of about 12 or 13 tries, and on a motor only producing 322 at the wheels.
1/2 psi is not going to give another 60 at the wheels.
I made a 7 inch runner intake (12 is stock), with a plenum double in size. I lost 40 lb. ft of torque across the curve and made no extra hp at the top end. Later, when I had my blower on, at 13psi, the stock length runner made a ton more power across the curve than my shorter runner intakes. Try 55rwhp and 30lb ft.
Just because its a cobra doesnt mean squat.

 

[marleyskater420]

So resonance tuning is the science of figuring out what size/length of the runners work best with each application.

So what is this waves you talk about? 5th, 4th, 3rd wave?Explain further.

Are you saying that bigger plenum with short runners equates to more top end power? And visa versa for low-end power? If not, please explain how the different sizes effect power.

 

[bruce]

Originally posted by VadersV6
Yup, tuned resonance only works in a narrow range.
Above or below it, it works against you.
It only takes a 13-14 inch long runner to do this.

Shortening the runners and increasing the plenum volume does not always lead to more performance.
It may be the trend on the turbo regal (which doesnt obey the laws of physics I guess), but it applies to just about everything.

By the way, this 1/2 a psi you mentioned is not the case. I gained 60rwhp on my cobra at 6800rpm, by going 2 inches shorter and altering the plenum design.1/2 psi is not going to give another 60 at the wheels.

I made a 7 inch runner intake (12 is stock), with a plenum double in size. I lost 40 lb. ft of torque across the curve and made no extra hp at the top end. Later, when I had my blower on, at 13psi, the stock length runner made a ton more power across the curve than my shorter runner intakes. Try 55rwhp and 30lb ft.

Did you record the MAP values before and after?. A 1/2 PSI difference on a N/A engine is a fair amount. 1/2 PSi on a car running 28 PSI of boost wouldn't see as being as such a big deal as the N/A engine.

I didn't say it always did, I said in what I've done, meaning on my TR, it did matter.

Are you into actually discussing this?, or going with statements like the Regals don't obey the laws of physics?. While your experience may have lead you to one set of conclusions, others may have differing results/ conclusions.