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Old 03-06-2003, 03:46 AM
  #46  
Under Pressure Performance
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Sorry to jump in this thread so late, but I have been real busy at the shop lately and have had little time for replying to threads.

Throughout this thread I have read a few comments that I would like to address...

Earlier in this thread someone mentioned that the horsepower from this engine was not all that impressive because it comes from a 968 based engine - Well, truth be told, while there are several differences in the two engines, there are also MANY similarities. You cannot say that this car is no longer a 951 because it has a 968 "based" engine in it, nor can you say a 968 is a 951 if you stuck a 2.5 in it.

Heck, for that matter, virtually ALL 2.8, 2.9, 3.0, 3.1, & 3.2L 951's use a 968 crank, but I huess that is OK?

Truth be told, power is power - I don't care how it is made. While this engine is impressive, it is not the end all be all of 968/951 engines.

Currently I am working on a turbo 968 "based" engine to "replace" its 2.8L 951 "based" engine. The 2.8L put down 520.5 RWHP @ 6600 RPM on 19 PSI - I built that engine in August of 1999 and the date of the dyno run was 12/01/99 (not too far off the engine of topic)

Another example of a mighty 951 engine is one of our (several built) hydraulic lifter 490 RWHP 2.8L engines.

As a fellow ultra-performance engine builder, I have a lot of respect for Bob Norwood. He, like myself, is not afraid to push the absolute limits of these engines.

In regard to Woody's car...

Woody has spent a small fortune on his car. Without question it is an extensively developed vehicle with LOTS of time, effort, and money invested - Woody's money! - So why should he allow folks to sponge up the ideas he spends so much money to R&D? Sure you may get an odd feeling in your stomach when he closes the hood on your prying eyes, but if you want the same technology he has under the hood of his car, all you have to do is buy it. He forked out the money to do it wrong, test, do it a little better, test, do it even better, test, then finally get it right - Why should he give that away?

While I can understand folks wanting to know what is under the hood, or how things were fabricated, or how his turbo is mounted, or how certain things were done, I will say that I FULLY understand Woody's wish to keep as much a secret as possible.

For one, he club races, so ANY competitive edge must be protected. Second, he is fast, so naturally people will gather around to see what they can see, and I am sure that gets old REAL FAST. Third, he paid the money to build the car, so he is certainly entitled to protect his investment.

In regard to balance shafts and crank lightening...

Well, I have a lot to say about each of these subjects, but I will spare you the long winded explination of each and just touch on each in the following paragraphs.

Balance shafts: True, inline four cylinder engines have inherent harmonics, however, most mass produced engines are not zero balanced either. Does that mean that a zero balanced four cylinder engine will not have harmonics? No, BUT a HEAVILY modified four cylinder engine (lighter pistons, rods, crank work, wrist pins) that originally HAD balance shafts in stock trim, can actually develop "worse" harmonics if the balance shafts are retained after the modifications.

We have been building fully prepared engines for years and eliminate the balance shafts in virtually ALL these engines. We were the FIRST to develop a direct bolt-in balance shaft delete kit, and we have been advocates of balance shaft removal for quite a long time. Keep in mind, our prepared engines have lightweight rotating assemblies and are zero balanced - Retaining the balance shafts in this scenario has the EXACT opposite effect of their designed use.

How much power do you gain by removing the balance shafts? Depends. Not the answer you were looking for? Well, that is the truth. Depending on the output of the engine, RPM, grade of oil, and the condition of idler and tensioner bearings, the gain from deleting the balance shafts will vary. OK, so some of the criteria I listed may have a very small imapact on the actual gain, but I bet there are a couple of facotrs you may not have taken into consideration either - Right or wrong?

Lightening the crank...

There are several schools of thought here, and I will not dismiss any view that contradicts my own, but will state that my views are based on MY experience, and my experience dictates that, depending on the application, you may or may not want to lighten the crank and/or other rotating assemblies.

Without giving away any trade secrets, I will give you a couple of scenarios and let you make your own decisions.

Four cylinder engines generally have less rotating mass than larger V6's and V8's - I say generally because you would be surprised at how much heavier the stock 951/968 cranks are when compared to some of the V6 and V8 cranks.

Generally speaking, our engines use heavy counterweights, heavy clutch assemblies and other hefty rotating parts to smooth out the idle, smooth engine acceleration, and mask balancing tolerances.

The flywheel, clutch disc, pressure plate, ring gear, balance shaft pulley, alternator pulley, power steering pulley, and several other parts add significant weight to this already hefty crank. But how does that affect engine performance?

From a consumer standpoint, you would not want your $50,000.00 car to idle like crap and for its acceleration to feel any less refined than your 1988 Yugo - Would you?

OK, now on to when a heavy driveline and rotating assembly can HELP performance...

Say you wanted to drag race your 1988 Yugo. Well, it has little HP and TQ, but the car is relatively light. Well, if you lighten the crank, rods, pistons, and so on, BUT you do not increase the HP an/or TQ, then you will have a car that will not want to accelerate out of the hole, BUT once it gets moving, the "engine" will "want" to accelerate rather quickly, but its acceleration will be limited to its ability to push the car forward and overcome rolling resistance and aerodynamic drag.

In drag racing, small displacement engines that make very little HP rely on VERY heavy rotating assemblies. The spinning mass is used to create inertia which will launch the car quite effectively out of the hole. Although the "engine" will "want" to accelerate a little slower, the car will actually accelerate a LOT faster as it will have inertia.

A good example is an old Toyota Starlet with an old rotary transplant. The car with engine and driver weighs about 1700 pounds when stripped, and the rotary has all of 130 HP, yet these cars regularly pull mid to high ten second quarter mile times at UNDER or just above 100 miles per hour. What does that mean? - It means the car is maing all the time up in the first few hundred feet while the intertia is still unleashing. A typical 60 foot time will be around 1.2 - 1.3 seconds. At the three hundred foot mark the car is still accelerating pretty strong, but then the car's acceleration will begin to slow down because the engine does not make enough power to keep accelerating the car. The result, a GREAT 1/4 mile time, BUT a VERY low trap speed.

In contrast, take a fully prepared engine that makes some power. Take it on a road course where you need to accelerate quickly out of a turn and get to your shift point as fast as possible.

What makes more sense to you?

OK, I will make it easier - Take two IDENTICALLY prepared 500 RWHP cars. The ONLY difference, one has a lightened rotating assembly - You and I are going to race for $1,000.00 - Which car do you want?

Again, there are two schools of thought, mine is based on MY experience - I want the car with the lightened rotating assembly! - After I win the race (and the $1,000.00) I will gladly pay for drinks for all in attendance.

Thanks for reading, I hope you enjoyed it!
Old 03-06-2003, 04:03 AM
  #47  
Mike B
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Great perspective and info Scott...Thanks for the taking the time and sharing your experience...

I appreciate it!

PS: When I rebuilt my 951 last year I went with a lightened crank. The thing runs great for the first engine I ever rebuilt myself...Still amazes me <img border="0" title="" alt="[Wink]" src="wink.gif" />
Old 03-06-2003, 08:34 AM
  #48  
Skip Wolfe
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Hey Scott,

Welcome to the forums. I've always enjoyed your posts on the email list and its good to see you on the forums. For all of you who are not active on the email lists and may not know Scott, you're in for a treat. Scott has forgotten more about 951 engine building than most of us will ever know. Even longtime resident forum guru Danno acknowledges Scott is one of the, if not the premier engine builder for our cars.
Old 03-06-2003, 09:05 AM
  #49  
tecart
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i have been told that a built 2.5 944 turbo motor, bigger turbo, boost and fuel will gain 15 rwhp from balance shaft deletion, that is from 2 different engine builders who say they have dynoed the results, i dont think that is too far off from a possibility,
Old 03-06-2003, 09:42 AM
  #50  
Russ Murphy
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Thanks for reading, I hope you enjoyed it! </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Are you kidding? Heck yeah I enjoyed it! Thank you so much for you time and input.
Old 03-06-2003, 11:06 AM
  #51  
CarreraCup03
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Scott,
Can you let us know ... just for informational purposes .. which race winning engines u have built. And if possible the average longevity of these winning engines.

I think the real question here is not just max HP ... as you pointed out ... but a combination of longevity and speed. That is the only way to win races without rebuilding after each race.

I have no doubt that you have been able to make high HP engines as have many other engine builders. Done properly these engines are capable of very high horsepower and torque ... but most of us can not afford to rebuild engines after every race .. or even every season ... so I think most people in this particular thread are after longevity and speed .. not just max HP.

Scott .. thanks for taking the time from your busy schedule to respond to this thread ... that is what makes Rennlist a great forum.

944turbo
Old 03-06-2003, 08:38 PM
  #52  
David Floyd
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I am so glad that you found the forums, Scott

We are in for a treat when Scott replies to a topic.

Like Danno and a very few others, Scott can go into great detail on any subject regarding our cars.
Old 03-06-2003, 09:19 PM
  #53  
Luke
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Balance shafts.

When my buddy was rebuilding his S2 motor, he had long talks with DAVE FINCH, one of the guys that developed the S2 and firehawk motors....

He said, no matter what, USE BALANCE shafts. or your oil pick up tube breaks apart and your ref. sensors stop working. <img border="0" title="" alt="[Wink]" src="wink.gif" />

and the firehawk motors were spun quicker and made 40hp more than factory S2's...
Old 03-06-2003, 09:30 PM
  #54  
Steve Lavigne
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In Firehawk configuration, were they allowed to balance their motors?
Old 03-06-2003, 10:10 PM
  #55  
Russ Murphy
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> He said, no matter what, USE BALANCE shafts. or your oil pick up tube breaks apart and your ref. sensors stop working.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Dude. Didn't you read what Maestro Gomes had to say? If you go in and f#*@ with the crank and rods and the rest of the reciprocating mass, the finely engineered balance shafts are meaningless.
Old 03-07-2003, 12:50 AM
  #56  
Under Pressure Performance
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Darn it!

I just typed a VERY LONG reply and accidentally pressed the back button on the browser and whooosh! - Gone!

Now I am tired and don't think I have the energy to re-type it all tonight. Darn!
Old 03-07-2003, 03:30 AM
  #57  
86944turbo
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When I learned that adding chips, MAF, lgr. turbos, this & that, was not the proper avenue, I spen approx. 1 yr. seeking an engine builder. I placed most of the decision on what I could ascertain about the builders personal intergity. very large H/P #'s out there and most are enhanced. One of the many things I learned was that there are people who build engines and there are engine builders. Yes, I'm a Milledge advocate. For instance' I asked him if he used a 3 or 5 angle cut on the valves. He said that was old school, valves are fully radiused. I asked him about the development of his cams. He explained that lift, overlap, duration are important and that ramping, refining the harmonics and new billet, etc. are also. Everyone uses a Spintron, I was told that it goes far beyond that. Re-shaping the combustion chamber, proper heat treatment, correct head studs (can be used multipe times) which oil passages need enlargent, ex. valve material (face and stem different) and maybe most importantly proper engine management programming. The lambda numbers change every 1000 rpm, to well w/i .01 of what he knows works. Plus, most, if not all of his motors are on the track. Twenty+ pounds boost for 8-12 races a year. Some 3 yrs w/o rebuild (requires head gasket, etc.) He tells me he could build motors for less if it weren't for the expensive machining he requires. Not many Porsche engine builders on the west coast require tolerance to w/i 1/10,000". Enough of that.

I scanned he article in Excellence (600+ h/p). I am by no means an engine builder. The 10:1 comp. seems high w/24lbs boost. Yes, no? Helluva a car!!

Jon had a 2.5L, 16v w/over 600 quitw a few yrs. back.
Old 03-07-2003, 11:18 AM
  #58  
Chris Cervelli
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Balance shafts have absolutely nothing to do with what is commonly referred to as 'balancing the engine'.

Inline engines are hopefully balanced like this:

The crank is balanced to itself. This means it spins perfectly in the main bearings and generates no side forces while doing so.

The pistons all weigh the same, the rods all weigh the same, and the rods are also balanced end-to-end.

This is all a good idea, but has absolutely no effect on whether or not you need balance shafts.

The balance shafts are there to counteract the secondary shaking forces inherent in ANY four cylinder engine. The magnitude of these forces is dictated by the reciprocating mass, stroke, and rpm.

If you reduce the reciprocating mass by 20%, the forces will be same at an rpm 20% higher. Nothing can be done to eliminate the secondary shaking forces.

I am not in favor of removing the shafts because:

When solid engine mounts are used, the extra vibration is objectionable from a comfort and control standpoint.

The extra vibration excites every part of the engine with a low resonance frequency. This includes the P/S and alternator attachments, as well as the oil pickup tube. These components' fatigue life is quickly used up resisting vibration.

Every bolt in the car is now self-loosening. Obviously this is disasterous for reliability.

Points in favor of removing the shafts (in descending order of importance):

lower overall engine weight. There is a nice gain here. You probably can chop close to 20lbs which is almost 1% off the front axle in a light race car. I would kill for this in a serious car.

decreased complexity. Nice, but I doubt anyone has lost a race due to balance shaft failure.

increased power. I measured at 1.3 hp gain on an 83 944 in a 3rd gear dyno pull. This car has the early shafts that churn up more oil than the later shafts. This is pretty much a worse case scenario. Claims of 15hp lost to driving the shafts are ludicrous.
Old 03-07-2003, 11:39 AM
  #59  
CarreraCup03
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Chris,

Thanks for posting ..... no one needs a list of your race winning cars. It would take up the whole post!

944turbo
Old 03-07-2003, 11:36 PM
  #60  
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"....Well, I have a lot to say about each of these subjects, but I will spare you the long winded explination..."

Gee, Scott, thanks for NOT being long-winded! If you went on any longer I was going to put myself out of my misery! <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" /> <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" /> <img border="0" alt="[ouch]" title="" src="graemlins/c.gif" />

Just kidding!

Thanks for summarizing alot of the BS on this thread!


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