CI and turbos

[V8 Beast]

I know this argument is as old as time, but I figured I would see how people from different car backgrounds think.

 

When it comes to turbos are you a fan of more ci, less, or do you feel it really doesnt matter?

[Mopar]

less c.i. on boost. i have always believed that anything that has a power adder will live longer with a smaller stroke ratio as its less stressful on cylinder walls. but when you start throwing in aftermarket blocks and whatnot that theory doesn't hold much weight.

[ruinms]

depends on vehicle weight. if it needs the extra tq, a big ci turbo motor will make good tq with less lag. they say you dont gotta rev to high with a turbo setup. same as with a big ci motor. makes all the power at mid rpm range. they go good together if its a race motor imo

[V8 Beast]

I think if you have a nice strong block the cubic inches really doesnt make a lot of difference (torque can be fixed with nawzzzz ). If the block and internals can handle the boost then you can make dyno queen numbers no matter what. U guess the argument there is that some think the extra added weight of an iron block isnt worth it.

[ruinms]

what motor are we talking about? honda lsx bbc ? FORD

[V8 Beast]

what motor are we talking about? honda lsx bbc ? FORD

 

All.

[ruinms]

with a big rs ratio your block hates you. r s meaning rod- stroke ratio

[V8 Beast]

Take a 2jz, add a huge turbo and some spray.

take a forged Ls1, add a turbo and some spray.

take a forged dohc, add a turbo and spray.

 

Now drop all of these motors in 3 fd's... what do you get?

[ruinms]

a setup that wont work cause its missing a ford? lol im playing ci is always good. the main thing that matters is power to weight ratio.

[ruinms]

this is why i say its all about tq. tq gets you moving hp keeps you going.

[V8 Beast]

Torque ftw!

 

Another scenario...

 

If a huge turbo'd built to the hilt evo engine is put in a 2004 GTO... Can it run 9's

 

 

 

 

I say not unless its converted to all wheel drive and loses 1000 pounds

[Rally Pat]

Take a 2jz, add a huge turbo and some spray.

take a forged Ls1, add a turbo and some spray.

take a forged dohc, add a turbo and spray.

 

Now drop all of these motors in 3 fd's... what do you get?

 

Tilley's next car.

[ruinms]

yes because its a 4g63 and sheps car is nasty. a gto with a glide behind a 1000hp 4g63. lets hope it makes alot of tq to move it.

[ruinms]

this would be the motor it would need to go 9's. the gto would deff need slimfast. i agree with that.

[Nate1647545505]

I know this argument is as old as time, but I figured I would see how people from different car backgrounds think.

 

When it comes to turbos are you a fan of more ci, less, or do you feel it really doesnt matter?

 

My .02 (engine theory point of view -- don't have much experience in the drag racing realm)

 

Energy is energy. Lower the displacement, higher the cylinder pressure needs to be to achieve the same output. For some engines, like the 4G, 2J, S5x, etc have the sealing capabilities with great combustion chamber design that can effectively handle it (on pump gas, too). There are some notable 80's F1 engines from Honda and BMW rated in the 1000bhp range from 1.5L and 6 cylinders. The thing to keep in mind - these engines made their power from 6k-10k RPM. Great if your application and gearing can take advantage of it.

 

The other side of the story is accepting the physics of turbos, mainly the turbine. There are two accepted components that contribute to spinning it, mass flow, and heat (enthalpy across). Mass flow into the turbine is equal to mass flow into the intake + fuel mass. Squires quotes this as one of their main selling points - but they somewhat abuse it neglecting the other component, heat. Mass flow is the same through out an engine, but temperature has changed from the intake to the exhaust. Having a higher concentration of heat leads to a higher concentration of pressure, which is stored energy that aids the turbine.

 

Back on topic, going to the Smokey Yunick side of things, a larger displacement motor with lower cylinder pressure outputting similar power is going to be generally accepted as the safer choice. Generally, it will have a higher mass flow rate (assuming it's a performance built V8) then a smaller displacement motor. That translates to more mass flow available for the turbine. Hopefully Mark and Anthony with APS TT Vette's at IPS will let us sneak a peak at their dynos - if they do, study it, compare it to similar horsepower smaller displacement engines along with those having less cylinders.

 

The largest problem with displacement usually means an unfavorable bore/stroke ratio, or a large bore. That can really drive up weight and stresses in the rotating assembly, which often limits the max engine speed. So, how do you combat this -- increase the amount of cylinders. There's a reason the Veyron uses 16, and carries a healthy displacement of 8L.

 

Like anything, I think there's a healthy balance between the two.

[Shearer]

There is still no replacement for displacement. Disregarding any any sort of class rules for this question it all comes down to how much money you have and if you are willing to spend it.

[sol740]

This question is hard to answer cause you have to take into account what the vehicle is being built for. A lot of people think more HP = faster and that's not always the case. Straight line ? Road course ? Rally ? Driver mod first, power second imho. Regardless, if you just mean making huge numbers on a dyno, displacement + FI will net positive results if the motor is built for it. I persoally love my 4g63s power and i'm only mildly modded. Though I bought the car because the way it hugs corners.

[phil]

im putting a skyline motor on pauls bike with the giggle juice, and watch him fly

[twistedfocus1647545489]

I'd say that if you have the money to spend to make the bigger engine last - you'd only come out ahead.

 

Look at Pro Mod, they run huge engines and power adders. Actually, Look at Troy Coughlin's GTO Pro Mod... up until this season it was a twin turbo Big Block (which I thought was 540ci or larger, I don't recall) then a supercharged Big Block. As I recall, I think they even upped the displacement on purpose when the rules were juggled around a bit for the FI cars. I don't think they'd go that big unless there was some tangible benefit. They put alot of research into building for these racing classes... it's not F1, but I bet it's close.

[2highpsi]

There is still no replacement for displacement. Disregarding any any sort of class rules for this question it all comes down to how much money you have and if you are willing to spend it.

 

Yes, there is. It's called volumetric efficiency. Anything can be made fast with the proper setup. All the displacement in the world wont do anything if its not used to its full potential.

 

All things being equal ofcoarse a larger engine CAN make more power. I agree with ya on it coming down to how much you are willing to spend.

[Nate1647545505]

Yes, there is. It's called volumetric efficiency.

 

Very good point. With today's and tomorrow's engines we are seeing technology like variable valve timing, cam phasing, and soon - variable cylinder to cylinder valve event timing.

 

Couple technology, forced induction, and displacement and you can rule the world - or atleast a few highways on it.

[Mensan]

The largest problem with displacement usually means an unfavorable bore/stroke ratio, or a large bore. That can really drive up weight and stresses in the rotating assembly, which often limits the max engine speed. So, how do you combat this -- increase the amount of cylinders. There's a reason the Veyron uses 16, and carries a healthy displacement of 8L.

 

Another problem is getting air into the cylinders. This is why the smaller OHC engines can make a lot of power on forced induction. It is also why the DOHC Ford engines make so much under boost (more valve area). Once you start adding cylinders, then you have even more cfm through the intake spread across more intake valves. If you look at a 5L V8 and a 5L V12 the main difference in power is head flow, not number of cylinders.

[Nate1647545505]

Another problem is getting air into the cylinders. This is why the smaller OHC engines can make a lot of power on forced induction. It is also why the DOHC Ford engines make so much under boost (more valve area). Once you start adding cylinders, then you have even more cfm through the intake spread across more intake valves. If you look at a 5L V8 and a 5L V12 the main difference in power is head flow, not number of cylinders.

 

I agree that valve area is generally a good thing. If the 5L V8 and 5L V12 have the same total head flow - the total potential airmass is going to be similar. If the V12 has higher flow on a cylinder to cylinder basis, it will of course, make more power.

[86GT]

I like a small block more but you can make power with just about any engine. I would say that the more C.I. the easier you are going to be on parts. You will have to lean on small block alot more that big block. A 4cyl will have to run 50psi+ to make big power versus a V8 running between 25psi-30psi making the same power. I would say spool up time would be alot faster with more C.I. but other than that I don't think it matters all that much.

[blueG60rado]

you want to avoid backpressure, so don't undersize your turbo