just came in the mail and go figure there is a big "Efi special" most of it is nothing worth mentioning, but they interviewed this guy by the name of T.J. Tracey when one question and response intruigued me

"HRM: Can Efi equal carburetion for peak power?

TJ: The peak numbers are very close, but , with EFI you can increase the range of peak output at high rpm where airflow limitations would cause volumetric efficiency to decrease. When engine speed reaches the point where more airflow through the intake tract is not possible and the engine begins to fall on its face, carburetors usually compound the problem by causing the fuel mixture to become overly rich. Carburetors cannot fine tune delivery to compensate for this. With themore advanced EFI systems, it is possible to program the computer to react to decreased airflow by reducing injector pulse width to maintain acceptable air/fuel metering for a longer period before the limit is reached. As a rule of thumb, we find that EFI provides 300 to 500 more usable rpm at WOT than carburetors. The more advanced EFI systems can also combat reduced volumetric efficiency by igniting the mixture soone. When programmed to do so, the increased timing advance starts the combustion process sooner which makes more cylinder pressure and more useable rpm. A non computer controlled distributor cannot do this"


interesting stuff, though, im sure a "more advanced efi system" isnt neccessary to take advantage of the spark tuning stuff. Should be easy to set up a wot extended spark table such that more timing is added past peak torque right?

I wonder what kind of gains that can add at the track

 

lol i just realized how the guy keeps plugging "an advanced EFI system" when a 7747 can do all of that i would think
but interesting nonetheless i didnt realize that carbs suffered from the fuel thing, and i didnt realize there was more power to be had by more timing up top

[This message has been edited by Pablo (edited January 08, 2001).]

 

It's all about compromizes, EFI just lessens them.

 

I think that the 7747 can be used and worked with enough to do anything any of us would ever want it to do. An efi computer could be faster and have some sort of fuzzy logic and more sensors and make a 1000 computations per second, so that no matter how fast you mash the gas or what level the barometric pressure outside is, you could always have perfect air fuel mix. but i dont think would make all that much difference, maybe a few percent increase in efficiency of an engine, but for what we all could want, we got all we need. we are just in the front of learning how to use it all to our advantage. Good post, thanks for sharing Pablo. I think ill go get that mag, so i can read the whole article.

 

nah the whole article is sorta dissapointing, just that one answer was cool, most of the questions were the same old boring questions about hardware which are pretty basic, there are a few other entertaining articles in it this month but nothing spectacular

 

Actually, this adding additional advance at higher rpms makes a lot of sense when you think about it. The whole concept of ignition advance is to have the mixture fully igniting at the point just as the piston is at TDC and about to begin the downstroke. It all takes a few milliseconds to begin and takes relatively the same amount of time regardless of the engine's rpm.

However, as rpms increase, the amount of piston travel (in degrees revolution) is always increasing in a given amount of time. So, if an engine can handle 36* @ 4,000 rpm, it should be able to handle more at a higher rpm. Obviously there are other factors that limit the amount of advance, or everyone would be increasing their ignition advance in a direct relation to the increase in rpms.

Before getting into eprom burning, I've always been limited to what the you could do with a non-computer distributor, which is control the amount of vacuum advance and the mechanical advance.

But now that I can get inside into the eprom, I can re-explore all this and try adding more advance at even higher rpms. I really have to start "unlearning" a lot things now that I can get inside the eprom.

 

I think in this context he meant "the more advanced EFI systems" compaired to the lesser advanced carburetor systems. The more precise control of fuel and spark is often overlooked by those that down EFI in favor of carbs. Many of these people believe the only reason an EFI system makes more Low RPM power is because of longer runner length. The contradiction to this belief is the BG venturi TBI. You can remove a carb from the intake and bolt up the BG TBI and pick up huge torque gains with no changes in the manifold or runner length. On radically cammed engines it will improve idle & reduce usable idle speed. Peak HP is about the same but the power curves are much broader.
VIVA EFI.
Don't ya just love it when someone suggests to you that "you should ditch that fuel injection crap and get a carb." lol
At the dragstrip I once had a guy tell me "if fuel injection was anygood John Force would be using it instead of a carb" lol lol lol ROFLMAO!!! I had to break his heart and tell him that all nitro funnycars are injected and so are all topfuel rails.
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Tracy /AKA IROCKZ4me

• 355 cid
• AFR heads
• Arizona Speed & Marine hydraulic roller cam w/ AFR hydra-rev kit
• modified SLP runners
• TRW forged pistons/ceramic coated
• fully balanced
• Edelbrock headers/ceramic coated
• SLP cat-back
• Paxton supercharger
• Nitrous Express nitrous oxide

My IROC-Z
EFI Performance Club on Yahoo
Club IROC-Z



[This message has been edited by IROCKZ4me (edited January 08, 2001).]

 

haha tracy, i think we can all relate to the sentiment youve experienced


and you are absolutely right about the venturi thing and low end torque

thats pretty much the whole reason i stayed with efi from the getgo, I sat down and hypothesized one day that a given TBI motor with low vacuum signal will have more power than a given carb motor when it has low vacuum signal

then i built the big cam, single plane 305 that everyone said would be a dog down low

It was one with a holley carb
not so with the tbi

 

You learn more every day, Pablo... As you eluded to this board, I donnot have much experience burning PROMS for gm ECU's... I guess the 15+ years of EFI experience I have does not count, huh, even if I did not need to burn chips to get that experience? I said that your spark curve was bad, then you got mad. If you just had the manliness to ask me why I thought so I would have helped you modify yours about 1/2 a year ago and you would have really laughed at that article. I'm sorry I have more EFI experience than you and am also sorry that you would not help me in my GM learning process when I "asked" for help. That's ok, not everyone in this world can get along with everyone...

Anyways, that HotRod spark/tuning info is an item that cannot be checked SOTP, you MUST use a dyno or other driveable torque measuring device (yes, they exist) to tune WOT at HIGH rpm's to get the Spark/fuel tables just right. If you generically add spark at high RPM levels, you WILL have detonation and RUIN your motor in a few minutes, literally. That article just reinforces my statements to GET a scan tool and the MSD ignition advance control??? You can literally drive around and add advance until your ECU shows knock (at all MAP levels, too, not just WOT), then subtract a few degrees to be safe and fill in the cell of your new PROM. I said you would be AMAZED at the amount of spark you will be able to add but you laughed. I also should have said you'd be amazed at the amount of TORQUE/HP/RPM potential it would ad but I thought this was obvious. Maybe I should write an article under a "pen-name" (so you won't think it is me and not read it...) for a magazine (again) and then you will read it and understand me better. Until then, happy tuning and I am still willing to give anyone a NICE spark table, if they just ask... Of course, it will never be correct as it sits but will be easily tweakable and might be better that whatcha got... Again, Pablo, you cannot imagine what my Spark table looks like but I bet you are getting curious, now, eh? But, can/will you ask for help? I bet not.

All you other guys, BE CAREFUL about adding advance! It is/will be the biggest and most costly EFI mistake you can/will make!!! Add it slowly if you do not have/use a scan tool and use the MSD device to do it! IMExperience, you cannot (really) hear knock under WOT with good exhaust and rodd noise! BE CAREFUL!!! Also, be sure that your knock sensor is tuned for your harmonics or that data is useless. After the Spark data is done, redo the entire fuel table becasue spark changes will change fuel requirements in certain areas. Then, check the spark table again. It may take 2-3 iterations but you will be rewarded handsomely.

 

this is growing tiresome... im completely confused now.. are you sure it wasnt some other pablo you spoke to? I have 0 idea what you are talking about perhaps this is all imaginary?

the beautiful part is that you are absolutely right about testing the wot high end spark advance, its not something sotp can tell you as with anything else in the realm of fine tuning. You dont know that from experience with gm ecm though because no gm ecm as far as i know has a spark table that extends to the upper rpm band as it would require a change to the code.

and oh yah i probably would be amazed huh by all the advance i could add right? since you know what my engine wants right?

funny, since the time when i mistakenly posted what I had done so far, to now, ive removed a bunch of timing I must be reading the egt wrong i suppose the rapid temp drops and back and forth movement must be good, and the center electrode edge rounding must be good also, thanks for the heads up ill tune for that

What amazes me is how those racers from back in the old days managed without these new fangled dynos and whatnot! Wow that smokey yunick! what an idiot he was for reading plugs and making changes based on ets!

and no, i totally do not care about any spark table you might provide as its no better than one anyone else can pull out of their ***

FAQ for future encounters with fast broker:

will an msd **** make tuning your part throttle spark easier? sure thats been obvious
Is it necessary? No, course not
Are you going to buy me one as a gift? Nope
Do i have money to spend on one? Nope
Do you work for msd? Probably, from the way things sound
Do you know what you are talking about? not more than anyone else on this board that knows the basics of how to tune and probably less than alot of others
Do i care how many years youve supposedly been tuning? Nope, races arent won by telling the other guy whats supposedly under the hood
can a dyno be helpful? Sure why not, if i had one in my garage with a WB o2
can you tune this wot top end advance on a dyno successfully? Nope, as speed increases you need less advance because load increases, gotta find the best balance for the intended use of the motor. I dont race on dynos
Should Fast broker continue his series of Fairy Tales about his imaginary reality? If he wants to, as long as they dont include me!

Thank you

Pablo

[This message has been edited by Pablo (edited January 09, 2001).]

 

I am not going to get in the middle of this squabble, but does it REALLY matter to anyone how Pablo "analyzes" his car, other than to Pablo?

Personally, I think it is great that Pablo has chosen a route of analyzing his car by means other than relying on a scan tool. There are a lot of people who are interested in PROM burning, and it is really a deterient to learn that to burn your PROM that you MUST have a scan tool.

I consider a scan tool a "nice to have", especially if you have a fast baud rate ecm that provides a lot of information. On older ecms, with limited information, I too think that it basically is only useful to help track down a bad sensor.

I personally can say that inspite of having Diacom+, it really isn't that useful on tuning for WOT. I do find it helpful for my part-throttle tables, but I too have to use other methods to determine what is my best WOT settings.

Its like having access to an air compressor an all those neat little tools; great to have, but not totally necessary to work on your car, and sometimes you still have to use a good old fashion "box-end wrench".

To sum it all up, it's Pablo's car and his decision alone as to how he tunes it. Fastbroker, you tune your car your way and Pablo will tune his car his way. Cool?

But I AM interested in your methods/tricks to tune @ WOT using a scan tool. You have my attention.

[This message has been edited by Glenn91L98GTA (edited January 09, 2001).]

 

I had hoped this wouldn't start up all over again. Guess I've got to learn to live with being disappointed.

Oh, well.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

 

sorry jake id like it if trax could delete the flame bait and responses so that it seems like none of this happened as i thought the stuff i posted was interesting, maybe someone coulda posted some real world experience from playing around with high rpm advance

[This message has been edited by Pablo (edited January 09, 2001).]

 

Over rich at WOT with a carby means the Main jet air bleed is too small. Or the carb is to small and at continued WOT starts developing a higher then expected venturi signal (some 2 barrel restricted clases use this to play games with a power valve).

The classic EFI vs carb is pointless. The ultimate difference is timing manipulation, and you can do a work around to get WOT right. But, for divibility a EFI can beat a carby, because of the timing manipulation.
EFI wins the emission choke battle
High RPM HP can be best won with a system that atomizes fuel best. Peak torque can be won with vaporization.
For a given runner design a TPI can flow more air since there isn't fuel displacing air in the runner.
Take a Hilborn IR and convert to EFI, and compare a webered IR manifold with the same tube length / diameter and butterfly size and it would be a draw for WOT.
AND we get back to a poorly tuned EFI will always lose to a properly tuned carb and visa versa.
BTW, I've run 13s with a Q-Jet on a cross fire base, and within a .1 with the dual throttle bodies, and had more left in the Cross fire tuning.

 

, <<<<<<<maybe someone coulda posted some real world experience from playing around with high rpm advance>>>>>

Hi Everyone,
The truth is you can and should increase timing after peak torque as it will broaden the torque band. Peak torque is where the highest cylinder pressure is made. I have verified this on the dyno and can usually gain around 20lbs of torque on a small block at the higher rpms. Grump, I didn't know you knew so much about carbs absolutely correct on the air bleed stuff, emulsion also ties in with this and that 2bl resticted power valve reclosing at WOT when the engine goes back into vacuum can be an aid as well. On a restricted engine the intake starts making more vacuum than the exhaust and EGR's itself, what I have found is if the exhaust closing event is too late, shutting the power valve again works well, but if cam timing is correct it's all air bleed and emulsion baby After about 3" of vacuum at WOT(which is usually around 6000 rpm) the restricted motors like another 8-10 degrees of timing. hth's
-Carl
btw the 7747 computer has a high rpm timing adder. x more degrees of timing per thousand rpm beginning at x rpm. X's being programmable, and it is in use right from the factory(hint).

 

Pablo, I'm sure it was you I spoke to. You admitted to a conversation with me before and now you deny it. WOW, you gotta get your lies straight. (edit: If I knew how to go back and put the post thread here where you admitted the conversation, I would, to show everyone how much of a liar you are. Can someone else do it for me???) Everyone on this board KNOWS we had a phone conversation, which I have thankfully removed from my short and long term memory... I don't work for MSD, FYI, and I thought my UserName was enough to let educated people know what I do. Oh, is your PRESENT BIN posted??? I'd be glad to look at it for you and what you changed from the last one I have from you. Should I post it in the BIN archives for all to see??? Now THAT would be funny!!!!!!!!!!!!!! Keep doing your SOTP tuning for 2 more years and I'll help others do it the EDUCATED way in a week or two. Your choice, I guess. The extra money for the tools to do it fast/right is worth the money to me.

InTech, if you've done some EFI advance work on a dyno, I'd like to discuss our results to compare and contrast someday, if you can find some time. I'm a little busy for the next few days but maybe next weeek or so. I'm having trouble with some knock signal(s) with the OEM knock sensor at high (6000+) revs. I know that dyno tuners use accelerometers tuned to the specific engine but no gots. I guess I'd like to have better high rpm data than what I can get w/OEM knock sensor and ESC. bu-bye

[This message has been edited by FastBroker (edited January 10, 2001).]

 

I am locking this topic. Pablo: Since this is your topic if you would like me to reopen it then e-mail me offlist and we'll discuss.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
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