Does Anybody Really Understand Our RPM Limitation?

So on fuel only, how many crank degrees do you think we have to EFFECTIVELY inject the fuel and make power? This thread is a technical discussion and anyone with non-technical comments like "my brand x injectors make power at 4000 rpms" will be deleted at my request. The data flushed out of this thread will play into the next thread discussing nitrous and why it makes more power.

I am not talking about hitting the bowl or not hitting the bowl either..... Taking that out of the equation completely - how late do you think we can inject the fuel and still convert that into power vs just smoke and heat? You have decreasing cylinder pressure fighting the increase in cylinder volume on the power stroke.

From my observations:
30 degrees ATDC - good to go with slight smoke
40 degrees ATDC - diminishing returns with heavy smoke
50 degrees ATDC - looking like a dodge with a smarty

Anybody want to refute these numbers?

There is 18 degrees per millisecond eclipsed at 3000 RPMs.
There is 24 degrees per millisecond eclipsed at 4000 RPMs.
Injector delay= somewhere between .6 and .7ms on typical injectors at 3000 PSI.

So lets say we have an actual injection timing (not electrical) at 3000 rpms of 10 degrees. That would give 40 degrees of crank rotation to "do the deed" and make power. Pulsewidth commanded in that case would be 40/18 or 2.2ms (window) + .7ms (delay) so around 3ms of PW.

The same thing at 4000 is similar but i will throw in 5 degrees of timing extra so we will have 45 degrees of "window" at that point so 45/24 = 1.88 with the timing delay of .7 making 2.58ms total commanded the place to be for optimal injection there.

This make sense to everyone?

You have injector opening delay - you have that figured in - but you don't have injector closing delay figured in.

45* of a total injection event is OK at lower RPMs - but at higher RPMs is WAY too much for effective power especially when you figure in the burn rate of diesel fuel. This can be easily seen if you look at the changes and developments being made on the mechanical injection side of the sport with larger diameter plungers and barrels and fast fill cams that are being created not to increase the overall volumetric size of the pump(even though that is a result) but to increase the actual injection rate and allow them to shrink the injection window more. There is a reason that p-pumped motors can sing down the pulling track at 6-7K RPMs one a setup that is built and dialed in perfectly. 5-6K RPMs is common.

Hotrodtractor said:

You have injector opening delay - you have that figured in - but you don't have injector closing delay figured in..

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So does the closing delay cancel out the opening delay, or is it added to the total PW? If it cancels it out, wouldn't the delay be adjusted with timing?

Hotrodtractor said:

You have injector opening delay - you have that figured in - but you don't have injector closing delay figured in.

45* of a total injection event is OK at lower RPMs - but at higher RPMs is WAY too much for effective power especially when you figure in the burn rate of diesel fuel. This can be easily seen if you look at the changes and developments being made on the mechanical injection side of the sport with larger diameter plungers and barrels and fast fill cams that are being created not to increase the overall volumetric size of the pump(even though that is a result) but to increase the actual injection rate and allow them to shrink the injection window more. There is a reason that p-pumped motors can sing down the pulling track at 6-7K RPMs one a setup that is built and dialed in perfectly. 5-6K RPMs is common.

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Agreed on the higher RPM stuff, but we are not talking about this at the moment.
The cylinder pressure is going to stop flow faster than what you will see on the bench but my point to this is that you will never want MORE than what I have calculated and the numbers are generous. With HEUI, 4000 RPMs are all we are worried with at this point so I didn't see the need to talk about what you are trying to accomplish which will change the game hopefully.

Big Bore said:

So does the closing delay cancel out the opening delay, or is it added to the total PW? If it cancels it out, wouldn't the delay be adjusted with timing?

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Frank, all this means is that the injector stays on a bit after you tell it to turn off, further telling you that the numbers I calculated were conservatve and more PW isn't the answer.....

Gearhead said:

Frank, all this means is that the injector stays on a bit after you tell it to turn off, further telling you that the numbers I calculated were conservatve and more PW isn't the answer.....

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Right, and maybe I'm wrong but assuming the delay for closing is the same as the delay for opening, then wouldn't you just advance the timing for the injection event enough to compensate for the delay? IOW if you have a PW of 2.2ms, and opening delay is .7ms and closing delay is .7ms, you still have total PW of 2.2ms.

Gearhead said:

Agreed on the higher RPM stuff, but we are not talking about this at the moment.
The cylinder pressure is going to stop flow faster than what you will see on the bench but my point to this is that you will never want MORE than what I have calculated and the numbers are generous. With HEUI, 4000 RPMs are all we are worried with at this point so I didn't see the need to talk about what you are trying to accomplish which will change the game hopefully.

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I'm lost.... If we are talking about "Understanding our RPM limitation" - then why is higher RPM application not applicable? Its one of those further extremes that are NECESSARY to understand and convey the subject at hand. I'm not worried about 4K RPMs - I did that on 200% tips on the sled pulling track in 2007 and 2008 - how do you think the red truck would have liked today's current crop of off the shelf 400% tips and fast flow mods?

I do agree that cylinder pressure limits injector flow - if you're running enough timing and a short enough injection window - you could put in all the fuel BTDC - much like what is being done today on some of the common rail stuff at the track - then it is much less of an issue than when compared to someone with their injection event centered over TDC - so that plays a big role as well - but even though that does decrease the pressure differential across the injector tip - at worst case it might limit flow say 15% under WOT conditions.

Hotrodtractor said:

I'm lost.... If we are talking about "Understanding our RPM limitation" - then why is higher RPM application not applicable? Its one of those further extremes that are NECESSARY to understand and convey the subject at hand. I'm not worried about 4K RPMs - I did that on 200% tips on the sled pulling track in 2007 and 2008 - how do you think the red truck would have liked today's current crop of off the shelf 400% tips and fast flow mods?

I do agree that cylinder pressure limits injector flow - if you're running enough timing and a short enough injection window - you could put in all the fuel BTDC - much like what is being done today on some of the common rail stuff at the track - then it is much less of an issue than when compared to someone with their injection event centered over TDC - so that plays a big role as well - but even though that does decrease the pressure differential across the injector tip - at worst case it might limit flow say 15% under WOT conditions.

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So was that engine making more power at 4000 than it was at 3500? Was that at a normal ICP range if so? Show me a 200% nozzle that makes more HP at 4000 RPMs than it does at 3500 RPMs at mortal ICP levels.

Also with the big cubes, do you think we will ever need to spin the motors at 5k or more in an inducer limited class like 2.6? I've often pondered this.......

Gearhead said:

So was that engine making more power at 4000 than it was at 3500? Was that at a normal ICP range if so? Show me a 200% nozzle that makes more HP at 4000 RPMs than it does at 3500 RPMs at mortal ICP levels.

Also with the big cubes, do you think we will ever need to spin the motors at 5k or more in an inducer limited class like 2.6? I've often pondered this.......

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Ideally - I would have geared the truck and loaded it up so it would run down the track at 3800 RPMs - I can tell you that it DID make more power there than at 3500 RPM from track history. No matter how hard I loaded the truck up at the pulling track it never went below 3800 RPMs without dropping like a friggen rock. That was with mere "mortal" ICP values as well - there is not a single video on the net that I am aware of where my truck was running extraordinary ICP values - I have not begun to show what immortal powers I possess to the public. oke: Just good old fashioned 200% tips on some massaged B-codes (true B-codes for Charles sake) and a good balanced platform of parts meant to work together at my intended target.

4500 RPM launch carrying 3900 or so down the track:

YouTube Video

High rpm? Injection rate.

Injection rate? Oilflow.

Oilflow? A) limited poppet travel.

Limited poppet travel? Limited coil gauss.

Limited coil gauss? limited driver voltage. Alt) Limited coil turns.


B) limited oil pressure.

Limited oil pressure? Limited poppet pre-load

Limited Poppet pre-load? Limited coil gauss.

Limited coil gauss? Limited driver voltage. Alt) limited coil turns.



So....


Run a big old P&B.... pre-load the poppets to hold 4000 or so, and then offset your ICP table across the board to make up for the increased poppet pre-load.... that makes up for the decreased hydraulic ratio..... that makes up for the insufficient oil flow...

Charles said:

High rpm? Injection rate.

Injection rate? Oilflow.

Oilflow? A) limited poppet travel.

Limited poppet travel? Limited coil gauss.

Limited coil gauss? limited driver voltage. Alt) Limited coil turns.


B) limited oil pressure.

Limited oil pressure? Limited poppet pre-load

Limited Poppet pre-load? Limited coil gauss.

Limited coil gauss? Limited driver voltage. Alt) limited coil turns.



So....


Run a big old P&B.... pre-load the poppets to hold 4000 or so, and then offset your ICP table across the board to make up for the increased poppet pre-load.... that makes up for the decreased hydraulic ratio..... that makes up for the insufficient oil flow...

Click to expand...

It sounds so simple when you put it that way. LOL The added benefit of a lower hydraulic ratio is the reduction of the pressure loss of the HPO flowing across the poppet - lower flow rates means lower pressure drops.

Matt - why do you think that Charles and I are such proponents of using a 200% tip on hybrid injectors for most guys that are looking for a "do all" injector?

Hotrodtractor said:

Matt - why do you think that Charles and I are such proponents of using a 200% tip on hybrid injectors for most guys that are looking for a "do all" injector?

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The benefits are real, but there are some concessions I am not willing to make on a customer's behalf.

so is a 12 valve w/ 5x18s or 5x16s that makes say 600 hp as driveable as a common rail w/ 90 horse nozzls? Less smoke? less heat? you can give a million if ands or buts or scenarios, but the answer is NO, its not nor will it ever be.

Id rather have higher nozzle pressures than larger tips, for the same amount of power.

Chris said:

so is a 12 valve w/ 5x18s or 5x16s that makes say 600 hp as driveable as a common rail w/ 90 horse nozzls? Less smoke? less heat? you can give a million if ands or buts or scenarios, but the answer is NO, its not nor will it ever be.

Id rather have higher nozzle pressures than larger tips, for the same amount of power.

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Large tips do NOT have to be smokey pigs - its like anything else its the entire combo of parts that make an individual setup work or not work - WE have the advantage of being able to tune our electronically controlled engines and adjust fueling and timing to better meet circumstances - that is something that a 12 valve can not do. A p-pump with static timing and a ground fuel plate is full of compromises on tuning - we can refine better than that.

It was a very vague comparision but i was hoping someone would understand the point im trying to make.

200 percent nozzles can be made very driveable, but there are a few, even small, compromises with them. Like i said, if you could have 600 hp with 100 percent nozzles or 200 percent nozzles, all by running the same duration, what one would you rather have?

Very interesting topic. Hoping to learn some more.

Chris said:

It was a very vague comparision but i was hoping someone would understand the point im trying to make.

200 percent nozzles can be made very driveable, but there are a few, even small, compromises with them. Like i said, if you could have 600 hp with 100 percent nozzles or 200 percent nozzles, all by running the same duration, what one would you rather have?

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If I had 200% nozzles and 600Hp - why would I want it to have the same duration as a 100% nozzle? That defeats the purpose of the nozzles - and furthermore doesn't contribute to "Understanding the RPM limitation."

Charles said:

High rpm? Injection rate.

Injection rate? Oilflow.

Oilflow? A) limited poppet travel.

Limited poppet travel? Limited coil gauss.

Limited coil gauss? limited driver voltage. Alt) Limited coil turns.


B) limited oil pressure.

Limited oil pressure? Limited poppet pre-load

Limited Poppet pre-load? Limited coil gauss.

Limited coil gauss? Limited driver voltage. Alt) limited coil turns.



So....


Run a big old P&B.... pre-load the poppets to hold 4000 or so, and then offset your ICP table across the board to make up for the increased poppet pre-load.... that makes up for the decreased hydraulic ratio..... that makes up for the insufficient oil flow...

Click to expand...

Do you mind breaking this down Fred Flintstone style for the knuckle dragger types (like me)? I can grasp the vocabulary, and believe I comprehend the logic...but just to be sure....your time/effort into breaking this down one more level is appreciated.

i.e. High rpm is restricted by rate of injection as the mechanical window of injection stays is the same regardless of rpm, but this window "shrinks" as rpm increases due to speed of the rotating assembly

i.e. Injection rate is limited by oil flow....not sure I can expound on this point effectively. My two guesses would be ICP times 5, 6 or 7 (depending on intesifier to plunger ratio) to 1...and given a ICP limitation of 3000-3500 psi....HEUI is limited to less than ideal injection pressures, for this small mechanical window at upper rpms....My second guess would be a hydraulic limitation of the oil side of the injector...ie...it can't get out of the way of itself between injection events due to a pressure/volume limitation of the HPO system, or a limitation of the oil side of the injector...

i.e. Limited poppet travel...square me a way...

and the rest... :jawdrop: definitely need a lifeline.

Thanks!

Hotrodtractor said:

If I had 200% nozzles and 600Hp - why would I want it to have the same duration as a 100% nozzle? That defeats the purpose of the nozzles - and furthermore doesn't contribute to "Understanding the RPM limitation."

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because in that same duration, youd be burning a higher percentage of the fuel (assuming you injected a smaller quantity) via better atomization or w/ the help of nitrous. The point is IF you could have 600 hp w/ a 100% nozzle, why would you want the 200%. Again, this is if you were wanting to run 600 hp and the same duration. Ill leave alone some "gray area" that also comes to mind about duration for now.

As the comanded/actual pw and crank degrees etc all ties back in with what the injectors do and we get that from what is run on flow benches to the standards I believe all the main injector builders use; the cc/ms that are shown on all the flow charts for each injector set, is this electrical, actual, or what?

My point is that for all of this stuff to tie in well together between what we are told a set of injectors can flow at various time pressure and temp it needs to be at the same standard we are looking at when we speak about what our max injection window is for the actual real world engine or a understood offset.

So to this thread we are speaking of actual pw of what we would seeon an oscilloscope vs what would actually be called for in a tuner program. Is this the same pw we are given with our injectors flow charts? If not what is the offset we have to apply to those flow bench numbers to be on the same page here. I can't see how else a person can pick a proper injector for a specifc goal of fuelintonspecific rpm range and power goals.

Lets tie it all together so for those people that take the time to learn the tech can actualy make the best informed choices.

Chris said:

because in that same duration, youd be burning a higher percentage of the fuel (assuming you injected a smaller quantity) via better atomization or w/ the help of nitrous. The point is IF you could have 600 hp w/ a 100% nozzle, why would you want the 200%. Again, this is if you were wanting to run 600 hp and the same duration. Ill leave alone some "gray area" that also comes to mind about duration for now.

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Why?

Because the one making 600 on a 100% nozzle will be running more timing, more EGT and higher cylinder pressure. It will blow gaskets, melt/crack pistons and crack the heads much faster.


The relationship between flow achieved from increased pressure vs increased flowable area is not linear. It takes WAY.....WAY....WAY more pressure than it does orifice size to acheive the same flow. You simply cannot make a 100% nozzle flow what a 200 will with any practical amount of pressure. Before it flowed equal the tip would have lodged itself into the piston....


I would love to take the same truck with 100's, then 200's. Start with the 100's, then let me switch it to 200's and retune it. It's impossible that you would choose the 100's over the 200's. IMpossible....