Ed Wright

iTrader: (1)

They are certainly spending more on valve springs now. That is not a poor man's class. Last Feb at Pomona, before they added spring oilers, Mike was putting on 16 new springs every pass. Now many springs last two passes, some three. It's insane. An RPM limit would sure help expenses in that class.

Old SStroker

One report said PS valve springs may have 4-5(?) passes in them and the "middle" pass(es) may work the best. I take that as they need a break-in pass or maybe two, then they are at their peak then they start going south. That doesn't sound unreasonable, IMO. It's kind of like scrubbing in tires.

Does that mean you break-in the springs on a running engine or could you do it on a Spintron? It surely doesn't take cost OUT of running.

Ed Wright

iTrader: (1)

Unless something has changed very recently, Mike's springs aren't often going four or five passes. I haven't talked to him since he won St Louis. (Denver didn't go as well) He also has no Spintron to brake them in on. He takes them out of the box, puts them on, and runs them. Year-before-last, a few springs would last all weekend, which is eight passes if everything goes well. <G>
He was using Ti's on the intakes then, some guys ran them everywhere. He used steel springs on exhaust to save a few bucks. Those titanium springs usually just broke when they gave up. After Pomona last year, Frank made spring oilers, when helped as much as anything. A mandatory RPM limit of 8800 or so (that is lower than they were turning them before Greg Anderson & Jason Line came along. <G>) would most certainly lower costs. This last 1000 RPM ran operating costs WAY up.

MrDude_1

iTrader: (4)

if you guys were to design this RPM limit rule, how would you implement and enforce it?

short of having a sealed black box on mandatory ignition electronics, i dont see how you can limit RPM without making costs rise... if you were to say, demand specific rotating or valvetrain parts... then the other parts that are not specified, would go up in cost and become more exotic to handle it.. right?

Old SStroker

Here's Anderson and Line's quotes to Ian Bamsey of race engine TECHNOLOGY, May '06, pg 67:

GA: "In the long run these [engine rules] will hurt the class."

JL: "The inertia loading is getting so high we won't be able to turn the engine speed higher."

AFAIK, Bamsey doesn't make up his quotes. Line has an impressive background especially with Gibbs' NASCAR engine shop.

With a PS piston weighing 460 gm, a 130 gm rod and 35-45 gm of rings, there's nearly 640 gm yanking on the rod with 6500+ gs at 10K. If you do the math it will scare you...it does me anyway.

An IRL engine turning about the same rpm but with a 30% shorter stroke only sees about 4600gs on a 335gm piston/pin/rings mass. A 9700 rpm Cup engine with a piston/pin/ring mass about 525 gm sees about 5500 gs.The PS rod sees about 270% of the inertia load of a IRL rod, and 145% of the Cup rod. Ouch!

Ed Wright

iTrader: (1)

They already have a mandantory "black box", red actually. They HAVE to run a specified part number MSD box. A rev limiter in that box would be no problem. It is programmable, and NHRA has a little nerdy guy that rides around on a golf cart, and downloads all the qualifier's MSD box (after each round at many races) to see what they are running. A rev limiter they can't tamper with would be easy. Mike had used up $8,000.00 worth of valve springs by Houston last summer. About what he spent all season the year before. You have to remember, you don't see all their passes on ESPN2, those guys test every week, besides dyno work, scuffing in new tires and clutch disks. Mike and several others are out here at the Tulsa track damn near every week, or they test close to the next race. The engine rules I believe Jason was speaking to was the engine component min weight rules. Mike got bounced over two grams on his wrist pins last year. Frank's scales were off that much. Didn't matter to NHRA that his pistons were five grams over weight. Not sure how those clowns figured he could move the pins up & down without the pistons. Jason, Greg and others went to bat for him over that deal, but made no difference. You have probably heard Grahm Light (NHRA "Director of Competition") called "Dim Light", there is a reason for that.

MrDude_1

iTrader: (4)

cool..
followup question... if they all had this limiter set, how hard on the engine would it be as they go down the track on the limiter? what woudl the effects of that be? would it be faster to be just shy of the limiter? do you think we would see big changes in the motor, since the rpm window changes? woudlnt this rule screw everyone up if the NHRA kept moving this RPM window around, to "compromise" between issues...?
just thinking out loud here.

Ed Wright

iTrader: (1)

Uhhh, believe me those guys are smart enough to stay off the rev limiters. Any rule change like that would have to be done during the winter, so everybody could get their new combinations worked out. It would have to be set and left alone. MDS made a sealed "tamper proof" box for NHRA Pro Stock after all the crap about Greg Anderson programming traction control into his. Evidently that is how everybody thought he was outrunning them so bad. NHRA at first randomly came around and made racers give up their MSD box, crank trigger and harness, then install one they just issued them. Of course, that didn't slow Anderson down. It seemed to take verybody a while to figure out he was spinning his engine up like that. 9200/9300 used to be the average shift point. That was hard enough on parts. I won't hold my breath until NHRA implements a rev limit, however. I imagine the valve spring mfgrs love it.

racer7088

OldSStroker,

Valvetrain limits RPM in PS. No one breaks rods or pistons much but they do trash springs every pass. Obviously I can't name names (6 in PS) but the guys in PS are limited by the valvetrain and the power is there as well right now. Bigger bores would allow bigger valves but that means heavier valves which must be lifted higher to see real airflow gains. It's all in the valvetrain right now. We have guys that are on spintrons all week long in NASCAR. It's almost replacing the dyno! The heads are there and the bottom end can take it but the valvetrain can't.

PS. I have rods out of 500 and 600 mile NASCAR races and they are almost in brand new shape. They are within a tenth or two on the housing and pin bores even though they have seem over 9000 rpm all day long. The springs and heads are another story. You do know that LSM does PS stuff and springs right? I don't think Al is mistaken and neither am I.

racer7088

NO not at all. You want as big a bore and as much stroke as you can get and still have a reliable rotating assembly if you are trying to make power and stay reliable.

Bore stroke ratios mean nothing much really except packaging. The actual stroke is what determines HP per Inch usually not the bore stroke ratio.

An engine that has a 3 inch stroke and a 6 inch bore wont make power as high as an engine with a 2 inch stroke and 1 inch bore. One has a 2 to 1 B/S ratio and the other has a .5 B/S ratio.

If the 3 inch stroke engine turns 10,000 then the 2 inch stroke engine can turn 15,000 rpm since they will both aerodynamically exhaust their heads at about the same piston speed given similar designs.

The undersquare engine of the two will make 150 percent the hp per inch or hp per liter and turn 5,000 more rpm!

You will see extremely oversquare engines only in areas where there are rules about displacement so they are cramming as much airflow capability as possible into a given amount of cubic inches and that means the biggest bore they think they can make work with the stroke equalling the cubes for that class.

Whether they are big bore and short stroke or small bore and short stroke they will always be short stroke! The short stroke is what equals more hp per inch by reducing the inches actually under the given heads.

Now what you do need to look at is whether you have enough cylinder length to handle the stroke you are looking at in whatever block you are using. This and the skirt shape can have an impact on the engine over time.

MrDude_1

iTrader: (4)

LOL! thats not what i ment.

what im trying to ask is... well we know they would want to run on the ragged edge of the RPM limit... faster you can spin it, more power potential... so if something happened, more tirespin then expected, strong tail wind, i donno, something.... what would the effect of a limiter be? minimal? or is there a good chance to see something go BOOM when a engine that big, spinning that fast hits a hard limiter...? do you think the faster guys will be the ones that give up a little RPM to stay cleanly under the limiter, or the ones on the ragged edge that tap it occasionally?

lol, re-reading my first post, i see what you thought i was asking... gives me a funny mental image of a PS car going bang-bang-bang on a limiter all down the track..

Ed Wright

iTrader: (1)

Not sure why you think the rev limiter would break an engine. They sit with them WOT on the rev limiter on the starting line while staged.

Adrenaline_Z

REV limiters cut spark to alternating cylinders, it just sounds bad due to the
weaker exhaust pulses during the cut.

Max allowable RPM and peak power aren't necessarily at the same point, so
the driver would never stay close to the limiter throughout the entire run.

If so, I'm sure the engine design and gearing would account for a more suitable
power curve.

Wnts2Go10O

iTrader: (12)

so when looking for more power its better to put as much bore into it as possible to keep piston speed down and still add power? about the skirt shape, sounds liek the skirt is more a piston stability issue and the better the design the more reliable up top it would be.

racer7088

Well sort of....

Piston speed equals power with any given bore size and the highest hp stuff has heads that support the highest piston speeds at those rpms. The hp per inch stuff tries to turn high rpm to make the most power per inch because they usually limit them to a certain weight vs their displacement so hp per inch is the name of the game.

If you are just trying to make a lot of power and go fast with no rules whatsoever the biggest engine with the biggest bore AND the biggest stroke will always win all else equal. Of course thats assuming you have the best heads and cams and all that too! Something will always limit you so you will be the one to pick that if you are the engine builder.

The whole engine has to be thought out and planned for exactly what it's intended usage and target performance is or you will always be disapointed. The pistons most of the time are designed right but there is always more to these things than meets the eye. Generic shelf pistons are just that and they aren't always designed for what people are doing to them.

CamKing

one more thing to throw out there.

When building an engine for a certain displacement, and you are limited to a certain head, too small a stroke can get you in trouble.

If you've got a head that flows 300cfm, and putting a bigger bore under it doesn't increase the port flow, you don't want to go too small on stroke.
If the head will run out of air before the piston speed gets too great, a bigger stroke could be better.
Cam duration is directly related to RPM and Stroke.
The bigger the stroke, the longer the duration to make power at the same RPM. If I can run a 12 degree longer cam to make power at the same spot, I can run a lot more lift before I start destroying the valvetrain.As long as the port doesn't back up at high lifts, more lift will make me more HP.
Now this doesn't work when compression becomes an issue. The bigger cam does require bigger valve reliefs, so if you've got to lower your compression to fit the bigger cam in it may not be worth it.

racer7088

Excellent point as you can only make a cam so radical and still turn it the same rpm.

Adrenaline_Z

For a given lifter type (IE: SR, or HR), what is the typical rate of lift per
degree of rotation? Let's use 8,000 RPM as the max rev.

What sort of advancements have you seen over the last 5 years in terms
of lifter design to allow quick opening slew rates?

CamKing

There's too many variables
Max Velocity
Max acceleration
Valvetrain weight
pushrod flex
Rocker arm geometry
Spring rates
Harmonics
ect.

Right now I'm working on a solid roller design for a new Midget engine.
It's 264/268@.050" with .790"/.750" lift, and it turns over 10,000rpm.
You couldn't do that with a normal "off the shelf" style cam with those same numbers.

Jed Z06

iTrader: (1)

I love that statement!