raise the RPM ! i would like to go for that way!
i hate big turbos.. i'm not a drag racer so the evo

 

I hate them too. This car lost about 50 ft-lbs of torque at 4000 rpm with the bigger turbo. I hope they can recover some of this lost power with tuning.

 

wouldnt the best design for a high revving motor be under square.

 

Nice!! Good to see that Vivid got this project on lock! Can't wait to see the various results/compare and contrast. Good job guys!

 

Incorrect. Square bore and stroke engines have the best balance betwen low end torque and high revving ability, and the least amount of vibration of the three options: under, square, and over. In any case, you've got it backwards. Here is a full write up that explains the difference between the two:

Oversquare
A piston engine is oversquare or shortstroke if its cylinders have a greater bore (width, diameter) than stroke (length of piston travel). This is generally considered to be a positive trait, since a shorter stroke means less friction and less stress on the crankshaft. An oversquare engine is generally more reliable, wears less, and can be run at a higher speed; though with the aid of modern technology, the disadvantages of undersquare or longstroke engines have been overcome. In oversquare engines power does not suffer, but low-speed torque does to some degree, since torque is relative to crank throw (distance from the crank center to the piston pin center)—the leverage, essentially. An oversquare engine cannot have as high a compression ratio as a similar engine with a lower bore/stroke ratio, and using the same octane fuel. This causes the oversquare engine to have poorer fuel economy, and somewhat poorer exhaust emissions. Engines can be modified by being "de-stroked", shortening the stroke to increase maximum rpms and top-end horsepower, at the expense of low-end torque.

Oversquare or shortstroke engines have a tendency to overheat, but modern designs usually compensate for this tendency. Oversquare engines are lighter and shorter than similar undersquare engines along the direction of piston travel, but they are wider in directions perpendicular to piston travel. As the length is not a large problem, these engine types are highly favored by many manufacturers because of their power and compact size.

Formula One engines have a bore to stroke ratio of approximately 2.5:1 (very over square) and are capable of revving to 19,000 rpm.


Undersquare
A piston engine is undersquare or longstroke if its cylinders have a smaller bore (width, diameter) than stroke (length of piston travel). This can be a negative trait, since a longer stroke usually means greater friction, more stress on the crankshaft, and a smaller bore means smaller valves which restricts gaseous exchange; however, with the aid of modern technology, these are not the large problems that they used to be. An undersquare engine usually has a lower redline than an oversquare one, but it may generate more low-end torque. In addition, a longstroke or undersquare engine can have a higher compression ratio with the same octane fuel compared to a similar displacement engine with a higher bore/stroke ratio. This also equals better fuel economy and somewhat better emissions. An undersquare engine does not overheat as easily as similar oversquare engine. Engines can be modified with a "stroker" crankshaft, which increases an engines stroke from stock, increasing torque.

Undersquare engines typically are, proportionally, shorter in length, heavier, and taller than equivalent oversquare ones, which is one of the reasons why this type of engine is not generally used.

Many British automobile companies used undersquare designs through the 1950s, largely because of a motor tax system that taxed cars by their cylinder bore. Therefore, many of the most famous cars of that era use this design. This includes the Austin A-Series engine and many Nissan derivatives.

The Chrysler Slant-6, in the most common 225 cubic inch (3.7 L) version, is a massively undersquare engine with a 3.40" (86 mm) bore and a 4.125" (105 mm) stroke, producing most of its power right on the peak of its torque curve. The achilles heel of this engine, otherwise known for its exceptional durability, is being over-revved by inexperienced drivers. Red line for a factory engine is under 4,500 rpm; red line with aftermarket connecting rods is about 5,500 rpm. On the other hand, a well-maintained Slant-6 can be made to idle as low as 75 rpm (though this is *not* a recommended speed, neither the alternator nor the oil pump will function adequately). In some circles, the Slant-6 is nicknamed "The Stump-Puller" for its diesel-like low-speed torque. Appropriate gearing and driving skill is required for performance use.

****** also used mostly undersquare engines, in fact the L134 and F134 engines, with their fairly small 3.125 inch (79.4 mm) bore and 4.375 inch (111.1 mm) stroke, are probably the most undersquare engines ever built.

Nowadays, undersquare engines tend to be quite rare, but this form of engine is still used in some applications. For example, a modern 8.4 liter Valmet 645 inline-6 tractor diesel engine is a longstroke/undersquare engine, but has an output of over 300 horsepower (224 kW) with turbocharger and intercooler. The popular Mazda Miata also uses an undersquare engine.

GM's infamous 2.5L I4 "Iron Duke" engine was used in many economy cars in the 80's including the Pontiac Fiero. It is commonly believed that the engine is undersquare due to the low redline of 5000 rpm. However the bore is 4" and stroke is 3", making it a fairly oversquare engine. The redline is so low because the crankshafts were cast without piston counterweights and the connecting rods were poorly cast. The Fiero suffered engine fires in the 1984 model due to connecting rods snapping either due to overreving or suffering from oil starvation. Iron Dukes in the Fiero also caught fire because the height of the engine required a smaller oil pan to fit into the Fiero engine compartment. Low oil levels frequently led to overheating and engine fires. Even with a highly oversquare design, it is very important to point out that the bore ratio is not the determining factor in determining the maximum redline for an engine.

Hopefully this helps you to better understand the benefits of the design of the 4b11.

 

^^^ nice...

 

but rasing the RPM just puts a gater demand on the turbo meaning you need a larger trubo. otherwise the engine will choke really abd and fall on its face at these higher rpm!

its all about proper sizing of the engine and trubo for what you are doing!!

Chris.

 

Sick car!

 

Because those manifolds had issues, we teamed up with the guys at AFI to creat the best manifold on the market!

5000 RPM on a VIII with single scroll and no mivec is to be expected with a 35R...

 

Yes there is always a down side for seeking more power... We hope to try different turbos on this car to see how the X reacts to each one. Like you said... Tuning will tell

Evan Smith

 

Once again, keep us updated!

 

For the 4 preliminary kits for $4850 +shipping will include:

Manifold
Turbo
upper ic pipe
02 pipe+ Down Pipe
all necessary oil/coolant lines and fittings.
Twin wastegates

Intercooler kit will be separate...


AFTER THE FIRST 4 KITS ARE SOLD AND INSTALLED THE KITS WILL GO UP IN PRICE. LET ME KNOW IF YOU WANT TO BE ONE OF THE 4 THAT GET THE KIT. THANKS

EVAN SMITH

 

Does this include the two wastegates?

I am guessing it doesn't include larger injectors either...

still a great deal!

 

^^^ Fixed.

Injectors are not included as its dependent on the turbo you select. We will make them available to you.

 

Great Job Guys!
Once you get the cam timing dialed in after the prelim stuff and you get some better weather I think you're set.