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millerje78
Samba Amishman
Joined: October 16, 2005
Posts: 2445
Location: Holmes County, Ohio
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 Posted: Wed Apr 07, 2010 7:34 pm Post subject: |
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| Jake Raby wrote: |
| Tuning for max output is the most common mistake made by tuners. |
I think he was talking about full-on drag engines, not streetables.
also, what are the dates of your seminar in July?
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always seeking a better way
my 73 standard project
do your research, consult with experts, and buy quality parts. you won't be sorry |
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Andrew
Samba Member
Joined: October 27, 2000
Posts: 5865
Location: Who in the what now?
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| Posted: Thu Apr 08, 2010 12:15 pm Post subject: |
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| mondshine wrote: |
I'm glad I waded through the pissing contest 'till I got to Jake's post.
Makes me want to drive my Thing down to Georgia this Summer; not because I tune my cars that tightly, just because it sounds like fun, and I always like to learn something new.
Looks like it's just under 700 miles.
Jake- early or late in July? |
| millerje78 wrote: |
| also, what are the dates of your seminar in July? |
I'm going to agree with this. I think I might have to see about going as well... Where can we find some more information, Jake? 
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-Andrew |
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Thu Apr 08, 2010 7:22 pm Post subject: |
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| millerje78 wrote: |
| Jake Raby wrote: |
| Tuning for max output is the most common mistake made by tuners. |
I think he was talking about full-on drag engines, not streetables.
also, what are the dates of your seminar in July? |
I don't even tune full race engines for max output. I generally find the best BSFC numbers coupled to the tune that provides the broadest power range with the peak power at the target RPM.
Our race engines are not 1320' wonders, they either have to run a full mile at WOT singing to 9,000 RPM (Land Speed Racing), or they are seeing 7,200-8,500 RPM for a 45 minute SCCA race. The fastest way to melt one of these engines down, and even make LESS power is to tune for peak output.
I've gained a full second on the stop watch by tuning the engine for peak efficiency Vs peak output. The numbers don't matter- the engine has to TELL YOU what it likes and you have to be wise enough to listen and apply those settings. Thats how you go fast and make it to the finish line.
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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millerje78
Samba Amishman
Joined: October 16, 2005
Posts: 2445
Location: Holmes County, Ohio
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| Posted: Thu Apr 08, 2010 7:57 pm Post subject: |
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| Jake Raby wrote: |
I don't even tune full race engines for max output. I generally find the best BSFC numbers coupled to the tune that provides the broadest power range with the peak power at the target RPM.
Our race engines are not 1320' wonders, they either have to run a full mile at WOT singing to 9,000 RPM (Land Speed Racing), or they are seeing 7,200-8,500 RPM for a 45 minute SCCA race. The fastest way to melt one of these engines down, and even make LESS power is to tune for peak output.
I've gained a full second on the stop watch by tuning the engine for peak efficiency Vs peak output. The numbers don't matter- the engine has to TELL YOU what it likes and you have to be wise enough to listen and apply those settings. Thats how you go fast and make it to the finish line. |
I still think he was talking about 1/4 mile engines, even if you aren't. I know you don't believe in building "1/4 mile only" engines, but a lot of people do, and in the case of the 1/4 mile, tuning for max output seems like the only logical thing to do for such a short lived run, especially when you begin the romp with the tachometer pegged out.
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always seeking a better way
my 73 standard project
do your research, consult with experts, and buy quality parts. you won't be sorry |
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klatin
Samba Member
Joined: December 22, 2009
Posts: 32
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| Posted: Fri Apr 09, 2010 9:24 am Post subject: |
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Jake is right, even for 1/4 mile racers.
The only exception would be a nitromethane top-fueler that does not change its rpms much during a run, but uses controlled clutch slip to accelerate. All others still run through an rpm range to accelerate.
Max hp is only a fairly meaningless number. It's reached when the fall-off in torque with rising rpm falls of faster than the rpms rise. It does not mean anything else.
Torque is what accelerates the car, not hp. And having a high torque number over the used rpm range makes the car accelerate faster over the entire run.
And best BSFC at a given rpm is usually reached when the engine converts the most of the fuel energy into mechanical energy.
Think of an extreme case (to illustrate my point):
Two engines, both reach max hp at 5200-5300 rpm, but tuned and outfittet differently.
One engine produces constant 200 lbft of torque from 2500 rpm on up to 5300 rpm. So it's about a 200hp engine.
The other engine uses an oversized turbo that comes on boost only at high rpm. This engine produces only 50-100 lbft up to ~4900 rpm, and then its turbo comes on boost and torque rises fast to 230 lbft at 5300 rpm. So this is a ~230 hp engine.
It's obvious that the first engine would be faster through the 1/4 mile for the same car, because it can accelerate much harder during most of the rpm range, while the second only produces a kick in the butt at the end of each gear.
The old saying still stands:
"Horsepower sells cars, torque wins races". |
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Fri Apr 09, 2010 9:47 am Post subject: |
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| "Horsepower sells cars, torque wins races" |
thats right.. Just look at how the Diesel TDI Audis and Peugeots have dominated ALMS. They lost HP over the gas engines, but doubled the torque and the cars are faster than the gas powered cars.. They go further on one load of fuel and aren't as hard on parts.
I hate it when all someone is concerned with is horsepower, generally I send them to a competitor.
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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millerje78
Samba Amishman
Joined: October 16, 2005
Posts: 2445
Location: Holmes County, Ohio
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| Posted: Fri Apr 09, 2010 10:57 am Post subject: |
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| klatin wrote: |
Jake is right, even for 1/4 mile racers.
The only exception would be a nitromethane top-fueler that does not change its rpms much during a run, but uses controlled clutch slip to accelerate. All others still run through an rpm range to accelerate.
Max hp is only a fairly meaningless number. It's reached when the fall-off in torque with rising rpm falls of faster than the rpms rise. It does not mean anything else.
Torque is what accelerates the car, not hp. And having a high torque number over the used rpm range makes the car accelerate faster over the entire run.
And best BSFC at a given rpm is usually reached when the engine converts the most of the fuel energy into mechanical energy.
Think of an extreme case (to illustrate my point):
Two engines, both reach max hp at 5200-5300 rpm, but tuned and outfittet differently.
One engine produces constant 200 lbft of torque from 2500 rpm on up to 5300 rpm. So it's about a 200hp engine.
The other engine uses an oversized turbo that comes on boost only at high rpm. This engine produces only 50-100 lbft up to ~4900 rpm, and then its turbo comes on boost and torque rises fast to 230 lbft at 5300 rpm. So this is a ~230 hp engine.
It's obvious that the first engine would be faster through the 1/4 mile for the same car, because it can accelerate much harder during most of the rpm range, while the second only produces a kick in the butt at the end of each gear.
The old saying still stands:
"Horsepower sells cars, torque wins races". |
what you say here makes perfect sense, and I agree with it. I would take a flat torque curve over a high RPM HP figure any day, but you are talking about 2500-5300 RPM. some of these all out drag motors launch at a higher RPM than your stated peak RPM figure, and shift at crazy RPM above 8000. they are always in the upper register. peak HP means something to those guys, thats all I'm saying.
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always seeking a better way
my 73 standard project
do your research, consult with experts, and buy quality parts. you won't be sorry |
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miniman82
Samba Swamp Donkey
Joined: March 22, 2005
Posts: 9515
Location: Southern Maryland
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| Posted: Fri Apr 09, 2010 11:26 am Post subject: |
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Jake cares about a different operating envelope, and a different demographic than most of us are used to. I like low TQ too, but you can't deny the fun of upper-RPM HP. The song well tuned RPM engines make is music to my ears. 
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Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747
| Glenn wrote: |
| satterley_sr wrote: |
I just wanted to bitch but I'm getting no sympathy. |
Welcome to the Samba. |
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Fri Apr 09, 2010 11:46 am Post subject: |
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Its not just Drag Racing that requires high RPM to be effective. In Land Speed Racing we HAVE to make the highest peak power at the highest RPM possible to get any kind of decent results.
Every time we have come home with a new record I have tuned the engine for peak efficiency more so than peak output. We picked up 7 MPH when I finally pulled my head out of my ass and stopped looking for "numbers".
One has to actually experience this type of gain to take the statements I have made here seriously.
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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nsracing
Samba Member
Joined: November 16, 2003
Posts: 9467
Location: NOVA
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| Posted: Fri Apr 09, 2010 9:37 pm Post subject: |
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HP is Miles per hour is what I say.
YOu can have gobs of HP but you gotta be mindful of where in the RPM range you are getting it...when and how fast the power comes on.
YOu might make max 150 HP topped at 2500 RPM and no more.... is kind of useless to me if I gotta use the motor in a 1/4 mile run. I cannot use a stump-puller for a 1/4 mile run.
If you have the HP, the torque will go w/ it. I don't worry about torque so much. There is something called a tranmission to convert what I need at the wheels and push the car.
Everything has to be taken into account. Weight of the car, engine size, gearing, size tires, car configuration.
For drag engines, we just need that thing to last the whole day and try to kick ass.
You stick to the things that make HP when you build the engines. I deviate very little from a combination that has proved itself at the track.
But the main ones are machine work accuracy, deck height, CR, chamber vs. pistons designs, rod ratio, crank stroke, balancing, and the suitable topend and exhaust system. |
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teuton
Samba Member
Joined: April 02, 2003
Posts: 334
Location: Abilene Texas
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| Posted: Sun Apr 11, 2010 6:51 pm Post subject: |
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| Quote: |
| why not let fadec control everything? |
That's fine but where to mount the EICAS?
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Sun Apr 11, 2010 8:26 pm Post subject: |
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| Quote: |
| HP is Miles per hour is what I say |
If you would have been at Farmington today you would have seen an engine that I tuned on my chassis dyno roll off the trailer for the very first time with boost and clicked off a 5.86 @126 MPH.
First pass on a brand new engine design/tranny package and less than 2 MPH from the current MPH record in Pro Mod right off the trailer.
It left my dyno not tuned for max output, but still made over 500 RWHP-
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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nsracing
Samba Member
Joined: November 16, 2003
Posts: 9467
Location: NOVA
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| Posted: Mon Apr 12, 2010 12:48 am Post subject: |
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The spread on the record and the chase is not very wide. It is just that iddy-biddy difference that make or break it. There are a lot of guys out there already knocking on the door but only few can enter. A record run.
If am the fella chasing a record, I certainly am not going out there and bring something that still has some left in the jar.
Is this a 1/8th mile run? Oh it is moving alright. What is the 60-foot like on this one, Jake? |
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Mon Apr 12, 2010 12:55 am Post subject: |
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127 60 foot. Yes, 1/8 mile run.
This was the first time this car has made a pass with boost, it literally rolled off my dyno, into the trailer and onto the track. We never planned on putting it on "kill" the first pass out, it just kind of happened.
I was just trying to help add to my point about the effects of tuning an engine in ways other than what makes the biggest peak numbers.
We weren't chasing a record, only someone not very wise would take a brand new car/engine/tranny out and chase a record purposely..
Trust me, the "jar" has a lot left in it.
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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millerje78
Samba Amishman
Joined: October 16, 2005
Posts: 2445
Location: Holmes County, Ohio
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| Posted: Mon Apr 12, 2010 6:38 am Post subject: |
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| Jake Raby wrote: |
clicked off a 5.86 @126 MPH.
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holy buckets!! some driver had him/herself a grand old time driving that car. 
_________________
always seeking a better way
my 73 standard project
do your research, consult with experts, and buy quality parts. you won't be sorry |
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Mon Apr 12, 2010 7:28 am Post subject: |
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Yeah he is happy as hell!
I've had 3 calls this morning so far from people wanting time on my dynojet to tune their engines... Thats odd, because none of the straight line guys generally ring us up 
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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nsracing
Samba Member
Joined: November 16, 2003
Posts: 9467
Location: NOVA
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| Posted: Mon Apr 12, 2010 12:09 pm Post subject: |
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1.20's 60-foot. It can leave too! Very nice. 
A dyno is really a nice tool to have. Takes some money to be in this club. I am still reeling a little from my balancers purchases but I am completely happy.
I am keeping an eye out for a used Stuska.
Nothing like learning from seminars when you have all the proper tools right there.
Very cool, Jake. |
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Jake Raby
Samba Member
Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Mon Apr 12, 2010 12:37 pm Post subject: |
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The chassis dyno is the best tool I have bought to date.. The two engine dynos I have are great, but the variables that exist from the test cell to the vehicle can be critical.
Here is the VRN story about the pass and debut of the car.
http://vwracingnews.com/forums/showthread.php?t=304
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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