Posted by T.O.O. on April 22, 1998 at 21:44:19:
In Reply to: Excuse me, T.O.O. 2 posted by body on April 21, 1998 at 21:55:24:
The CR-V block is physically almost identical to the B series engines.
The manifold we're currently using on the CR-V is the same piece we use
for the Type R, and DelSol VTEC. We have reduced the runner cross section
16% to provide greater velocity at lower rpm, and some of the water passages
are relocated about .5". We attempted to group the "B" engines manifolds
(except for the GSR) during the testing phases, as it's much cheaper to
simply machine the maniflod to spec. The width of the CR-V engine compartment
relative to the location of the pulleys is also identical to the Integra
/ late Civic platform, so adapting the drive system was also simple. I
have been instructed to not discuss this particular application, however,
I can say this: The test piece we currently have is most enjoyable, and
it has an automatic trans. Personally, I prefer the automatic with the
blower....it's one of those natural and comfortable rides with plenty of
balls. Driving a stocker is a shock, and I wonder: Why would anyone settle
for this.....throttle response and torque tend to spoil you quickly. When
I drove my first Type R home, the Acura dealer called and wanted to know
what I thought. My answer was that the R's comfortable, but simply pulling
my Civic out of the driveway is a greater thrill than the entire "R" trip
to the house. The sales people were pissed, but it's the truth.
As we're putting miles on this CR-V, I believe we'll find any weak links with the trans, as we're running "significant boost" to accelerate "problems". So far we've got 4K very hard miles on it, and everything works great. If you'd never driven a CR-V, and didn't know what was under the hood, typical reaction from non Honda people is "350 Chevy"!
The block is different internally in that the center is similar to a large hunk of cast iron with 4 holes in it. The cylinders are obviously siamesed, but the "deck" is very stable, and as I've said previously, if I were building a Honda from Honda parts, the CR-V block would be where I'd start. It's a very stout piece. I'll make a quick exception to the supercharger rules for you. We're getting 125 ftlbs at 1500 rpm and peak at 209 at 4650. Now that peak is the peak of a very easy curve, so you're within a small % of that number for a wide rpm range.
At present, I'm in the process of designing a drive mechanism that consumes less power than the traditional belt drive. We have had absolutely no problem with the belt system, however, whenever I find something that will provide "free hp" and last 100K miles with no maintainance, I attempt to take advantage of the technology, especially if the price is in the ball park for the application, and this is.
Long rods.... You have absolutely no idea how many hours Smokey and I've spent debating this subject over the years. Rod length combined with crank stroke and rpm dictate piston speed. The rod length relative to stroke also geometrically dictates where in the rotation of the crank you'll see maximum piston velocities, and accelerations....and while on the subject of geometry the rod angle relative to the cylinder bore axis is a direct function of rod length. The severity of the rod angle becomes worse as the rod gets shorter relative to stroke, and therefore attempts to push the piston through the cylinder wall at any angle below 90 degrees either side of TDC. So from this stand point, piston and cylinder wall life are greatly compromised with the short rod. The short rod also causes the piston to "dwell" at TDC and BDC less time, and the positive and negative acceleration rates are higher as well, which cause lots of positive cylinder pressure, especially at overlap which can shove a significant amount of semi-burned gases back up the intake port. As these gases are largely inert, their presence in the "new" inlet mixture is a real negative when looking for an efficient burn. The dwell time the piston spends at or near TDC also dictates the amount of cylinder pressure that's "useful". It also effects the rate of valve opening and closing events.
Now let's go to the "Smokey" notion: The rod should be as long as phssically possible for maximum hp production. I concede that longer rods can lower piston / wall friction, and to a point engines with primative combustion chambers can usually produce slightly greater peak hp in a very narrow band. I'm talking about a 358 cid V-8 producing 800 hp at 9500 rpm. If you sample power at 9000 rpm you'll lose 150, if you sample at 10,000 you'll lose 150 or more. Drop to 8000 rpm and hp would be 450 or less. If you have a twelve speed gear box and can keep the engine in a 300 rpm band, it's great, but I design for the real world, and peaky engines are not in my plan.
Let's go from Smokey's ideal (2+ to 1ratio) to something around 1.75-1. The piston speed is greater, the acceleration rates are higher, the cyl. loading is slightly higher, the piston spends less time at TDC and BDC, and from a package standpoint the engine is shorter. Piston dwell time at TDC is in my opinion not a good thing, especially when the mixture's burning. Smokey contends that we want maximum cyl. pressure at TDC. Well, rotate an engine's piston to TDC and try to push it down....I'll give you a sledge hammer, and you will not rotate that crank because at TDC the rod's in line with the crank journal. I prefer to dictate when the engine will see maximum cylinder pressure, and I typically achieve it at about 25 degrees past TDC....the piston pushes real easy there due to the angle and mechanical advantage you now have achieved with the crank. The 1.75-1 provides the "prefect" acceleration rates for the piston (from a port design standpoint) and the "pumping rate" is not so violent that you hace all that semi-burned gas attempting to enter the intake port. The acceleration rate also is sufficient to allow reasonable valve opening velocities without colliding with the piston. I'm not the only one who has arrived at this ratio....it also allows a nice real world torque curve.
Anything below 1.65 worries me. Honda has obviously used their technology and good materials correctly to run ratios as low as 1.5-1. There small bore is part of the effectiveness, as the rod angle can't become so severe as bore decreases, and they provide excellent breathing with their heads, and it all fits under the hood. But, on the Type R, Honda says the piston speed is higher at 8500 rpm than any of their race engines. The race engines must last at least 2 hours, and at 15,000 rpm, their rod ratio must be considerably "better" than the 1.58-1 on the 1.8's.
This is all a portion of the "World Series", but you might copy it ....I am. ............................T.O.O.. ......................