Preferred Dyno Pull RPM Range w/Data

[ERA2076]

Hey Brent - please just follow your normal protocol with mine.

x-chr

[blykins]

Cliff,

I'm gonna load yours down around 1200 and see if I can add some vertical gas ports to those pistons.

[Dimis]

Mine too.

[ERA2076]

Originally Posted by blykins

Cliff,

I'm gonna load yours down around 1200 and see if I can add some vertical gas ports to those pistons.

Well if your going to screw it, just make sure it doesn't survive - er - in your shop - not my car.

[rodneym]

To answer the original question, I wasn't really sure from what RPM I wanted to see the pull start.
Perhaps to add to Brent's point, my engine was dyno'd from 3500, at least that's what the charts show.
That's my single vote on the poll for 3500 - simply because it's what Tom Lucas did, not because I know anything .
Hey, people don't pay me to build engines, so I trust my builder.
But any question I had, from the cam to oil weight, was explained to me in detail, especially because some of it seemed 'off' to my 'expert' eyes . In my case, a little knowledge is a VERY dangerous thing.

[750hp]

A few years back, I had a supercharged stroker 351W engine built in the States, then shipped it out to Australia and had it tuned over here. The dyno guy was a well respected tuner, but I went in there full of bravado, initially saying that I wanted to see "x" horsepower and I wanted him to do what was necessary to get there.

The way Brent has explained his thought process in this thread is really similar to the way the dyno guy explained it. To highlight his point, he said I could beat up the motor at the low end and high end of the rpm range (with the chance of me taking it home in pieces) just to get an impressive dyno chart, or he could do it his way and supply me with a perfectly tuned, reliably, understressed motor.

I quickly chose to talk less and listen to the expert...

[Barry_R]

Back before I acquired my own dyno I used to pretty much follow the other place's procedues - something of a courtesy since I was in "their house". Now that I have my own DTS cell I get to decide.

Much of my process comes from Engine Masters procedures, and I sort of stick to that range for consistancy's sake. Depending on the year, they go from 2500 or 3000 on up. Even with my water pressure cranked up to 70+ I can have a hard time holding a torque oriented engine down to 2500 - so 3000 is a better and smoother place to go from and I don't go lower any more unless its a mild street deal. It's hard to hear detonation in a dyno cell, much less a car before you've already done some damage. A styrofoam coffee cup on a 20 foot long piece of copper tubing bolted to the engine and routed up near the console will really startle you - it's a rattle amplifier.

I have a non-FE mounted to the dyno right now that will probably not load below 4500...

[AL427SBF]

Barry, to further the discussion ...

Parameters -
1. All engines are in the car and are registered for the street
2. All engines run on pump gas, figure 92 octane max, means Cr probably no greater that 10.5:1
3. Expected peak BHP is ~1 for every cubic inch, e.g. 427 CID is expected to have ~427 BHP
4. Motor was put together properly and broken in with > 2000 failure-free street miles

If a customer came to you for a dyno and requested you measure as much of the power band as is reasonably safe to do, what would be your starting RPM to record data?

Client could have motor sizes of -
a. CID < 351, RPM Start = ?
b. CID 351-427, RPM Start = ?
c. CID > 427, RPM Start = ?

Certainly not Engine Master candidates, but right in-line with good performing street builds.

[Dimis]

Mate, I don't understand your angle.

The pros, who have vastly more experience than most of us combined have politely tried to explain it to you, But you're still barking...

In case you missed it.

Originally Posted by 750hp

I quickly chose to talk less and listen to the expert...

Ps. Why anyone with a street build would really care about a few hp/tq point at 2000 rpm dyno chart is beyond me.

[DAVID GAGNARD]

Originally Posted by AL427SBF

Barry, to further the discussion ...

Parameters -
1. All engines are in the car and are registered for the street
2. All engines run on pump gas, figure 92 octane max, means Cr probably no greater that 10.5:1
3. Expected peak BHP is ~1 for every cubic inch, e.g. 427 CID is expected to have ~427 BHP
4. Motor was put together properly and broken in with > 2000 failure-free street miles

If a customer came to you for a dyno and requested you measure as much of the power band as is reasonably safe to do, what would be your starting RPM to record data?

Client could have motor sizes of -
a. CID < 351, RPM Start = ?
b. CID 351-427, RPM Start = ?
c. CID > 427, RPM Start = ?

Certainly not Engine Master candidates, but right in-line with good performing street builds.

What you really need to do is go to a shop that has a dyno and spend a few Saturdays there watching and learning......You obviously have never had an engine dyno'd and I'm guessing never even seen one on a dyno,much less watched an engine going thru it's paces on a dyno......

[Jerry Clayton]

Plans are for me to tune a stroked 427 with KC ported Edelbrock heads in a Shelby GT500 Monday morning-------

Some of the issues we will be working with are drivability ------------smoothness at low speeds in traffic conditions---has light flywheel------------

We built this engine 2 or 3 years ago and he has broken a clutch disc so he would like a tune refresh now that the shop has it back together---I will see if I can post some sheets------

[AL427SBF]

Originally Posted by DAVID GAGNARD

What you really need to do is go to a shop that has a dyno and spend a few Saturdays there watching and learning......You obviously have never had an engine dyno'd and I'm guessing never even seen one on a dyno,much less watched an engine going thru it's paces on a dyno......

That's pretty funny, I have witnessed a couple of dyno pulls from different shops and each shop does them differently based on equipment and capability. What you propose is ill thought, a sample size of 1 shop to determine a trend = foolish. You can also glean quite a bit of info by watching the many vids out there that take you through pulls on different dynos, builds and motor sizes. I was asking one builder's opinion on how he would test mainstream street builds, you obviously missed that key ingredient in the post.

[Cobra #3170]

Originally Posted by DAVID GAGNARD

What you really need to do is go to a shop that has a dyno and spend a few Saturdays there watching and learning......You obviously have never had an engine dyno'd and I'm guessing never even seen one on a dyno,much less watched an engine going thru it's paces on a dyno......

Amen to that!

[DanEC]

[quote=AL427SBF;1240897]Alarming that these expensive tight clearance well balanced builds can't take throttle at 2500 RPM. Road course guys must be walking on egg shells every time they exit the apex and roll it on to WOT @ 2800 QUOTE]

With most road courses wouldn't this be the difference in rolling into WOT in 2nd or 3rd gear versus in top gear? That is quite a difference in load on the engine. I'm not a road racer but I wouldn't think that many race car drivers would be rolling out of a corner lugging the engine at 2800 rpm in a high gear, instead of downshifting.

An enigne dyno is basically running in high gear for the whole pull.

[DAVID GAGNARD]

[quote=DanEC;1241725]

Originally Posted by AL427SBF

Alarming that these expensive tight clearance well balanced builds can't take throttle at 2500 RPM. Road course guys must be walking on egg shells every time they exit the apex and roll it on to WOT @ 2800 QUOTE]

With most road courses wouldn't this be the difference in rolling into WOT in 2nd or 3rd gear versus in top gear? That is quite a difference in load on the engine. I'm not a road racer but I wouldn't think that many race car drivers would be rolling out of a corner lugging the engine at 2800 rpm in a high gear, instead of downshifting.

An enigne dyno is basically running in high gear for the whole pull.

100% spot on,on a road course,one downshifts to whatever gear is needed coming off a corner.....I don't know too many road racers that stay in 4th gear for an entire lap!!!!!!!!!

Road racing and a dyno pull is like comparing an apple to a watermelon.....

David

[blykins]

I don't understand what kind of validation you're wanting here.

Displacement doesn't matter, except in the fact that some dynos have trouble offering sufficient torque to hold big stump pullers....thus Barry's comment on water pressure and big torque engines.

What does matter is compression ratios, cams, ignition timing, combustion chamber shape, etc, etc.

I told you that I built a 408W that was less than 9.5:1, had about 7.5:1 DCR, a slower ignition curve, EFI, etc. that I wouldn't mind to pull down to 2500 or so. However, that was essentially a *truck* engine, designed for towing/hauling.

I don't understand the extreme desire to see what your engine does at very low rpms. Actually, I'd like you to tell me why, because to everyone else, it just really doesn't matter unless you're towing a load. If you're cruising at that rpm, you're not at WOT. If you're at WOT throttle at rpm, you're just there for an instant. And again, WOT on the road is nowhere near WOT on a dyno!

[DAVID GAGNARD]

Originally Posted by blykins

I don't understand what kind of validation you're wanting here.

I don't understand the extreme desire to see what your engine does at very low rpms. Actually, I'd like you to tell me why, because to everyone else, it just really doesn't matter unless you're towing a load. If you're cruising at that rpm, you're not at WOT. If you're at WOT throttle at rpm, you're just there for an instant. And again, WOT on the road is nowhere near WOT on a dyno!

Zacctly,your cruising in your Cobra in 5th gear pulling 2500 rpms, you come on a slower car and need to pass it, you can leave it in 5th and pass the car,depending on your engine,a Cobra is a light car and most likely will be fine,or if you need to pass the vehicle quicker, you simply down shift to a lower gear to multiply the available power output of the engine.....
Same thing happens when your driving your wife's car/mini van or what ever it happens to be,you stand on the gas and what happens, your automatic transmission will automatically down shift one or more gears depending on the load put on the engine!!!!!!!!!!!!!!!!!!

Can't down shift on a dyno, it has no transmission!!!!!!!!!!!!!!

David

[AL427SBF]

You guys are reading way too much into this, not looking for a validation, just asking some questions. Different builders/racers = different opinions and we've already seen a couple between Brent, Barry and David.

I think you guys exhibit some old school thinking the customer just wants a peak horsepower/torque number so they can feel good and tell their friends. Early dynos were good at that but not much more, well dyno tech has evolved - particularly those with servo load flexibility.

Some test modes available in current dyno tech -

a. This mode is ideal for drivability tests and diagnosis of load related problems such as hesitations and misfires. By inputting a fixed load level (think of it as an infinitely long hill, where you can adjust the steepness of the grade) you can vary the rate of acceleration at will. This load is consistently repeatable and has a very fine degree of adjustment. The load value ranges from practically no load at all, to a maximum load that will stall just about any vehicle. You can now accurately adjust “tip in” fuel or accelerator pumps or any other “transient response” type of device - and any other parameter where rate of acceleration and load is an important factor in recreating the real-world experience.

b. In this mode, you select a specific RPM point where you want to hold the vehicle. We will continuously vary the load to hold the RPM at that point within one RPM at the axle. As long as you are above the minimum throttle setting that is required to achieve that RPM, you can apply as much throttle as you want and the RPM will not rise above that point - all the way up to the full maximum rated torque capacity of the dyno. The dyno will then display the real-time torque and horsepower being absorbed, as well as other real-time relative data.

c. We can precisely control the rate of acceleration to your specification. This is extremely useful for tuning purposes. We also hold the vehicle RPM at the starting point (called initial settling time) for a user specified period of time so the vehicle will be stabilized before starting the run. Once the dyno releases and allows the vehicle to accelerate, it will be perfectly consistent in doing so every time.

Most people would like to know how their motors build power over the drivable RPM range, who wouldn't. The equipment exists and you don't have to "pull the guts out of it" to get that info. I think the real root cause of our opposing opinions here is the ability/capability to provide broadband power information safely. Is your dyno dated? If so, maybe time to dump that obsolete POS and join the 21st century

[itstock]

I chose 2500 and up, but if a dyno operator or engine builder or tuner or...most anyone (because they probably know more than me about it) suggested they start the pull later, I wouldn't think twice. On the loaded chassis dyno they started my car at what looks like 2750. I wouldn't care if they started it at 4500.

[blykins]

"Is your dyno dated? If so, maybe time to dump that obsolete POS and join the 21st century."

You prove over and over and over and over again that you're not experienced enough to be leading this kind of discussion.

Let me pose this question: Do you think a race engine with 14:1 compression would magically pull lower without incident on a "non-obsolete" dyno?

Some guys wanna know what the engine does at other rpms other than peak. I'm one that preaches very loudly about not building an engine for peak hp numbers. However, do you honestly think that 500 rpm would make that much of a difference? If so, again, refer to line #1.

Anyone can cut and paste info they find on the internet, but I'll tell you first-hand that points B & C in your "current dyno tech" will melt pistons quicker than anything if the engine is pulled down too far. That's not opinion, that's fact.

Your "questions" are very similar to arguments.