Sat down talked w/ machinist RE: 4K drop off

[Joel]

I've been looking for (over the past few weeks) a good cam degreeing kit for OHC motors.

 

Anyone got some leads on a good kit at a reasonable price?

 

I completely agree with your machinist. Sounds like a good man.

 

My motor is going together with all specs in known order. Measuring every peice. I don't want any unknowns.

 

Joel

[backslider]

Does anyone make a adjustable cam gear for our appplication?

[Shelby]

2 yr's ago  i  ran across one that said it was a 6degree  gear  but , lost the  site address,  what would be super would be a way to  fit a jag  cam gear ,  man they have like 360 fine teeth (maybe not quite that many) on the  gear for adj the cam timeing, off set key ways are arround but they  don't alow  for much adj.

deff what we need is a  two  piece cam gear , even the  nissian has  had a  built in cam  timeing  mark system for  yr's  0, +7 and + 7

 

has any one got the cam timeing spec's  lift  point ,  most  aren't at "zerro" lift  because of the   difficulty in getting and exact  point  ,  so they use like  at".020 or .050 lift  to  check the cam at,  i found no referance in the manual for it, so i''m asumeing they  mean at  the point of  first lift, any one have the  exact figures where to check the stock  cam at

[BaltTSI]

Do you know how hard it is to find someone like that ?  you are so lucky , keep this guy happy !  he sounds like he's worth his weight in gold

[Joel]

I was thinking, maybe we could just slot out sotck gear, and tap threads into the cam where the pin usually goes. Mark where the Pin is now as "0", mark out up to 7 degrees both directions, have a slot machined in between those marks. Then upon cam installation, drill/tap threads, degree your cam, and set it where it needs to go.

 

Looks like there is 38 teeth on this cam gear, giving about 9.47 degrees per tooth... So if you needed somehow to go higher then 7degrees in either direction, you jump it a tooth and then dial forward or back from there in the slot.

 

Joel

[TurboRaider]

An adjustable cam sprocket is easy to make....  Drill out your cam sprocket out for an offset bushing.

 

The bushings are easy to make on a lathe.  

 

Also 20º off on the cam?  No way in this world you are off that much.  Do the math, take the amount cut of the deck and the head and add them up.

 

Take the Diameter of the cam sprocket mult it by 3.14.  Divide 360 degrees by the circumferance of the sprocket.

 

Here is a wag at it.......

 

{360º/ sprocket diameter *3.14}* amount you cut off your head = degrees the cam is off.

 

example:

 

360 / 4.5*3.14= 25.53 degrees per inch of head removed....  To get off by 20º you need to cut your head a whole lot!

 

Ok...  say you cut the head and the block a total of.08"  your cam would be off 25.53*.08= 2º.

 

Your rapid torqu increase is due to the cam hitting its power band (normaly asperated same as all motors) and the turbo spooling up.

 

Torque drop off is when you have a constant boost but less time to fill the cylinders.  

 

A longer event cam helps....  more pressure helps.  

 

what you amy want to ask is why is the torque dropping off faster than I like?  Horse power is a funtion of rpm and torque so as long as the torqu does not drop off too fast as the RPm inc you get more power.

 

So what might hold you back?  All the things you ahve looked at..  noting new that I know of.  More intake valve area to reduce the pressure drop across the intake.

 

A larger exhaust housing to reduce back pressure (AR ratio).  Drop the CR to get you out of detonation and pump up the pressure.

 

Do some math for mass air flow..  To see if your numbers make sense.  

 

Kevin C

[Joel]

Kevin, You have any idea where to get a Degree wheel and a dial bore gauge thats optimal for degreeing on an OHC motor?

 

Also... I'm not quiet seeing this offset bushing thing, is there an example somewhere where I could get a better idea of what you mean?

 

Joel

[Boosted_One]

His use of 10-20* was a pullout of the air. With my bare head there and all.

 

What he was getting at was it was off.

 

So are you saying the cam is a 4K issue Kevin?

 

Do you see the 284F cam as being a good cam for the powerbands we are looking for?

 

The machinist thought it was kinda weird the lift was the same for both intake and exhaust on the cam.

[kev]

Yes RPW and TEP make adjustable gears for our cars or you can also make your own as Kevin C. stated.

 

I will have to give you great credit though Kevin C. if this turns out to be the problem.  When Tim, John, and I were playing around with the 284RH cam, you stated "make sure you degree that cam" repeatively.   I think you said it about 6 times on the thread that I have printed out  "the only way to sucessfully get the performance from an aftermarket grind it to degree it to the specs on the cam card".   All quotes from you on this thread I have printed out, hehe.

 

summitracing.com has a degree wheel and dial gauge specifically for degreeing in sub compact OHC cars in the Subcompact catalog.  I think it is $90.  

 

kev

[kev]

Here is an even easier way to make an adjustable cam gear for only a couple bucks as obtained from the engine mods forum.

 

http://www.starquestclub.com/index.pl?boar...;num=1024680213

 

kev

[chiplee]

 Also he said don't get all caught up in the dyno run numbers. Use them as a guide but remember  to always note how the car feels. Sometimes a car is faster with the previous setup than it is with the new setup despite the added power..

 

Ok, I like your machinist too, it's hard to find people that can even "seem" genuinely concerned with your issues let alone go out of their way to show it.  Because I find what I've quoted to be exceptionally insightful I have to expand on it.  I'm not sure if he's getting at exactly what I'm going to say/paste   but either way it shows how much he's simply gathered and it may be more impressive if he's never seen it on paper and just figured it out over the years.

 

 "First of all, from a driver's perspective, torque RULES.  Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm.  Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same. In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.   OK. If torque is so all-fired important, why do we care about horsepower?  Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.   For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :-).

 

On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:

 

6 HP.

 

Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.

 

OK. Back to carland, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you :-).

[chiplee]

A very good example would be to compare the current LT1 Corvette with the last of the L98 Vettes, built in 1991. Figures as follows:

 

 

       Engine          Peak HP @ RPM   Peak Torque @ RPM

 

       ------          -------------   -----------------

 

       L98                      250 @ 4000              340 @ 3200

 

       LT1                      300 @ 5000              340 @ 3600

 

 

The cars are geared identically, and car weights are within a few pounds, so it's a good comparison.

First, each car will push you back in the seat (the fun factor) with the same authority - at least at or near peak torque in each gear. One will tend to *feel* about as fast as the other to the driver, but the LT1 will actually be significantly faster than the L98, even though it won't pull any harder. If we mess about with the formula, we can begin to discover exactly *why* the LT1 is faster. Here's another slice at that formula:

 

 

                                           Â Horsepower * 5252

 

               Torque  =       -----------------

 

                                                   Â RPM

 

If we plug some numbers in, we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @ 4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed, and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and anybody who owns one would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point.

On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm, and is happy right up to its mid 5s redline.

 

So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occuring a little earlier in the rev range, but that is debatable, since the LT1 has a wider, flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid range and up, however, the LT1 would begin to pull away. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT1, by definition, has an advantage.

 

Another example would be the LT1 against the ZR-1. Same deal, only in reverse. The ZR-1 actually pulls a little harder than the LT1, although its torque advantage is softened somewhat by its extra weight. The real advantage, however, is that the ZR-1 has another 1500 rpm in hand at the point where the LT1 has to shift.

 

There are numerous examples of this phenomenon. The Integra GS-R, for instance, is faster than the garden variety Integra, not because it pulls particularly harder (it doesn't), but because it pulls *longer*. It doesn't feel particularly faster, but it is.

 

Anyway, this is continued here http://www.vettenet.org/torquehp.html in my favorite torque vs. hp article, but that's more than enough.  

[TurboRaider]

Nice work chip....  One thing I will say is that while Torque is what you feel right out... HP gets you back in your seat when you get going.

 

I had a duster with a  420+ hp rever of a motor....  If you let that thing sing on the highway at 6500 rpm it would flatten you against your seat. ....  HP is the work being done,,,,,  Accelerating the mass of the vehicle.

 

Kevin C

[TurboRaider]

Mike,

 

My 2 cents on cams.....  The cam sets the basic personaltiy of the motor.  It determins the power range it will run in and where peak torque will occur.  

 

IF you drop the boost to just a couple of PSI and do a dyno run it should follow a very similar curve as when the motor is under 15 psi boost.

 

Where you run out of steam under boost is the same as without.

 

Fuel is the major limiting factor in making power...  specificly detonation resistance.

 

You can lower your compression ratio to allow more boost....  The idea is a longer slower burn, making power through a longer period.

 

You do hit diminishing returns and at 4000 rpm you will get to a point where you cant up the cylinder pressure much more without detonation or changing the tuning to the point where each extra psi of boost does not contribute nearly as much to generate power.

 

the other alternitive is to spin the motor faster.  Get more power pulses at a lower pressure to do more work.

 

As RPM increases for both a NA motor and a turbo there is less time to fill the cyl.  This is why cylinder pressure drops at RPM as does torque.....  but since you are turning faster you generate more power even though the pulses are smaller.

 

The power curvewill follow the cam...  a dyno tst at low boost should show the natural curve.  It at high boost it falls on its face look for other problems like fuel delivery, exhaust restriction ect.

 

Cam tuning can get you a few HP. Advancing the cam retarding it and noting how the motor responds can help tell you what way to go for your next grind.  Dont expect a miricle though.

 

If you want to make good power above 6300 RPM you need a bit of cam....  one that wont idle very well and is a dog at low RPM.  

 

Kevin C

[Boosted_One]

Thanks for the info Kevin.

 

What I am after is to broaden, flatten out the curves. Bring the HP and TQ to more of a plateu and not up then down.

 

6K with me is fine as long as I can keep the HP curve going still.

[chiplee]

Nice work chip....  One thing I will say is that while Torque is what you feel right out... HP gets you back in your seat when you get going.

Kevin C

 

Thanks Kevin, I love that article

 

When you get time go ahead and read the entire thing here http://www.vettenet.org/torquehp.html .  I don't want to beat a dead horse but this one isn't quite dead IMO.  HP just doesn't get you back in your seat, the fact that the HP is there is due entirely to the torque.  Torque is what a driver feels, always no matter how fast you're going.  Think of HP as a simple number that factors in the amount of work being accomplished by the engine, it's a nice number to know because if it's high you can easily assume that the motor is making big torque somewhere near or above 5252 rpm which is what we want.  HP in that regard is a better indicator of engine performance, but torque does the work.  I know you weren't debating or aguing and I feel like I'm starting to be a real d***, but trust me,  I only mean to ensure that everyone of us has a clear understanding of the relationship between torque and hp.  If you want me to shut up I will but for now I'll go on until we all talk about it like it's been made painfully clear exactly what is going on.  

[Joel]

Torque is indeed what you feel. HP is still power over time, frequency if you will.

 

300 ft/lbs of torque at a frequency of 5000 vs a frequency of 7000. Which does more? 7000!

 

BUT:

 

If you have HIGH HP (high rpm torque) and no low end to get there, you will never gear up to that level. Torque is required to pull you to that location in the RPM band.

 

You will feel torque, and horsepower will multiply that feeling. But Peak numbers are definately just a salesmens friend only. Higher averages are where one should aim.

 

Joel

[TurboRaider]

Torque is indeed what you feel. HP is still power over time, frequency if you will.

 

300 ft/lbs of torque at a frequency of 5000 vs a frequency of 7000. Which does more? 7000!

 

BUT:

 

If you have HIGH HP (high rpm torque) and no low end to get there, you will never gear up to that level. Torque is required to pull you to that location in the RPM band.

 

You will feel torque, and horsepower will multiply that feeling. But Peak numbers are definately just a salesmens friend only. Higher averages are where one should aim.

 

Joel

 

You feel the acceleration of the vehicle....  acceleration is dependant on the force applied and the weight.  What you are saying is that you need your power in a usable range, compatible with the vehicles gearing system.

 

The force applied is a funtion of RPM and torque.  They are interrelated, one without the other means no power and no acceleration.  This is simple math and a very simple equation.  

 

Yes a usable power band is needed.  If your gearing does not match you cant get to the power.  The real key is area under the curve, average power beetween shift points.  Maximum area under the curve give the best performance.  This can be had at any RPM band.  Double the RPM, half the torque and get the right gearing and the accelreration will be the same (if power band has the length).  The only differance will be if the inertia losses are higher in the high RPM engine.   It would be reasonalble to assume the a 10,000 rpm screamer would have less inertia.

 

For some real fun study what happens to power at the wheel at time = 0.  By definition since the RPM is zero you need infinite torque to generate any power.

 

There is an interesting bramch of math dealing with this called Laplace transforms.

 

My real world example is again my old Duster....  Lots of high RPM power, I killed the bottem end and a good part of the mid range.  Why was it good?  I used a Richmond five speed with NO over drive, just four reduction gears and a 1 to 1 fifth.  

 

 

 

The faster car will be the one with more average hp as defined by its peak power and how close it shift points are.  Again the one with the most area under the curve.

 

As you knew....  you have to have the gearing to be able to use it.

 

Kevin C

[Tim_C.]

Would it be true to say as the RPM increases, less torque is needed to make horsepower?

I remember my friend's 701HP @8500RPM SBC dyno chart. The torque dropped dramatically after 5800, but the HP went up just as dramatic. He was running a 605 lift roller cam (Comp Cam). I can't remember the real specs of the cam.

 

Tim C.

[TurboRaider]

Would it be true to say as the RPM increases, less torque is needed to make horsepower?

I remember my friend's 701HP @8500RPM SBC dyno chart. The torque dropped dramatically after 5800, but the HP went up just as dramatic. He was running a 605 lift roller cam (Comp Cam). I can't remember the real specs of the cam.

 

Tim C.

 

Exactly.....  Yes.

 

The cam sounds a bit small for the RPM range...

 

Kevin C

[MarioG]

Wouldn't resurfacing the head or decking the block RETARD the cam timing?

[Boosted_One]

Wouldn't resurfacing the head or decking the block RETARD the cam timing?

 

Your right Mario, it should retard the cam timing but on my motor the dowel pin on the cam gear always sat after 12:00 indicating an advanced cam timing, thus the machinists comments on advanced cam timing.

[DJpowerHaus]

I have questions about gearing...

 

Nobody needs to do 140 MPH, but getting to 100 the fastest is pretty important.

 

Why have the gearing set up with a max of 140 MPH?  Wouldn't it be better for everything to gear it down to say a 100 MPH Max speed?  Or did I just not learn anything from reading all of this?

[Shelby]

exactly DJ  but  changeing  gear ratios  is a little pricey,  but   my understanding is  you want to  be at your ideal max'd ( upper end of the power band) out rpm  just past the 1/4  traps,  but  a 100 mph  is a little low, 118 or 120 would be a better   speed for et's in the low numbers,

even if we  do get  into the 6500 rpm power makeing range it won't lower the et's that much  unless  we take advantage of it with gearing,

most of the guys  say they don't get into 4th  untill  just short of the 1/4  trap, but one thing a car  gear'd for the 1/4 mile is no fun to  drive as a daily driver, and while a 3:54 is a  very  good all arround gear it's  deff not the best for the drag strip , unless your  very limit'd on  rpm's , and playing  at the  launch with out slicks is  wasteing  a lot of time, if you think  spining  will get you into the 12's or lower,  check out EIP's  vedio  of their 10 sec quest