Modifying the Ultimate (be prepared)...

[myclone]

Before you guys flame me off the planet hear me out...

Is it poss to have the ultimate (mine in particular) modified so the "overboost" fuel cut off is eliminated?

I have a little cicuit I whipped up that uses another 3 bar map that cuts the IGNITION instead of the fuel. Its nothing high tech. Just an 741 comparitor with an adjustable reference V which drives a switching transistor that actually kills the primary coil voltage.

Anyway, can the "overboost" feature be removed from my ultimate? If so, who can/will do it?

TIA

 

[Daron]

I think there is actually a logical reason to cut the fuel, as opposed to the ignition. If you cut the fuel, there is no chance of the mixture self igniting. Cut the ignition only and you are still spraying fuel into a hot combustion chamber, and some pretty healthy cylinder pressures at full boost.

_________________
Daron
1992 Typhoon Blue/Gray
1991 Syclone Best 1/4 12.42 @ 106.1
Member Of Freakin' Ohio (MOFO) SyTy

<font size=-1>[ This Message was edited by: Daron on 2001-11-30 17:33 ]</font>

 

[myclone]

Daron,

Point well taken.... BUT (aint that always the case??). Whats the diff, as far as detonation, between cutting the fuel at a high boost and say... running out of inj capability and running lean.

Now, correct me if Im wrong here... Id rather have raw fuel dumped into the comp chambers with nothing there to light it off (other than cyl pressure) than too LITTLE fuel as would be found when a "fuel cut off" condition occurs..

I have, as much as I hate to admit, bounced off the "over boost" feature of the stock chip. I pulled the plugs and saw the lovely silver piston sprinkle decoration. On the ultimate I got into a little stop light war with a BMW (killed it) but forgot I only had 1/4 tank of fuel. Truck nosed over in about 40ft due to fuel starvation. Plugs had the same "piston decoration"..

Back to the subject... Again, correct me if Im wrong here. IMO (repeat... opinion) I feel safer dropping the ign during a "lean" condition instead of taking even more fuel out of a already lean, and dangerous, condition.

I know you guys have put a lot of R&D, time, etc into the reasoning for cutting the fuel off and prolly have very good reason to do so instead of cutting the ign. If you could take a moment to lemme in on why then Id be forever in your debt.. :grin:

TIA for any info..



<font size=-1>[ This Message was edited by: myclone on 2001-11-30 15:21 ]</font>

 

[smeagol]

I have no way of killing ignition thru the ecm. I'd rather do it that way though.

I haven't heard of anyone blowing up a motor due to fuel cut, though I'm sure it's possible.

You might be able to achieve your goals with a Hobbs switch and a relay setup.

Brian G

 

[myclone]

Brian,

Thanks for the input... Much appreciated.

Hobbs switch would work fine but I did the little ckt thingy cause thats what I do for a living. Got 12 hours to sit around "bread boarding" stuff. The ckt also allows me to mount the pot inside the truck for ease of adjustability/packaging..

How bout the getting rid of the "overboost" feature??? Can it be done simply? I know I cant do it due to my inability/lack of knowledge to "reburn" the chip..

Again, "thanks" for you guys taking the time to let me pester ya with my ramblings..

 

[leroy]

You ever turn your key off and back on while driving? It's great for scaring people and blowing up your exhaust. BTDT.

You won't have ignition without fuel.

Jim

 

[myclone]

On 2001-11-30 16:31, leroy wrote:
You won't have ignition without fuel.

Jim

Jim,

Your point well taken too. What I am concearned with is the few moments that the fuel is "leaning out" before the pressure drops off in the fuel system once the relay for the FP is dropped out. I know this is a VERY short time period but it HAS to be a few ms of extremely lean/detonatious (is that a word??) condition. Only takes a little time to pound out a rod bearing under detonation in my experience.

As for the ing on/off deal... Yep, BTDT too.. Used to do it in a company truck I drove years ago. It was a carbed ford ranger so I wasnt hurting anything worth a damn..

2nd gear low/med RPM, go WOT for a second or two, turn ign off while letting off the gas, wait less than a second, ign on... KA-BOOOOM!!! I swear the truck felt like it came off the ground.. It was known around work as the "fire breathing ford".. Till it died... Immagine that.. :grin:

 

[leroy]

I'm not positive the fuel pressure relay is cut. I remember discussing this with Todd Austinson a long time ago. He thought the injectors were cut. That should give you a quicker reaction time. I think the manual says the fuel pump relay is cut, but the manual has been wrong before.

To answer your original question though, it would be possible to raise the fuel cut to the maximum value to virtually eliminate it, unless you run some crazy boost. Easy to do with a chip programmer and an editor. I could do it, if you decide to go ahead.

Jim

Jim

 

[jwaller]

yes it is possible to cut out the ovr boost flap in the ultimate...BG or I or michael can do this for you just send me your chip and we'll take care of it.

 

[smeagol]

Fuel cut, pulsewidth = 0 milliseconds

BG

 

[Daron]

On 2001-11-30 15:19, myclone wrote:
Daron,

Point well taken.... BUT (aint that always the case??). Whats the diff, as far as detonation, between cutting the fuel at a high boost and say... running out of inj capability and running lean.

Now, correct me if Im wrong here... Id rather have raw fuel dumped into the comp chambers with nothing there to light it off (other than cyl pressure) than too LITTLE fuel as would be found when a "fuel cut off" condition occurs..

<font size=-1>[ This Message was edited by: myclone on 2001-11-30 15:21 ]</font>

It is my opinion that the fuel cut is not like a lean condition, or promote the onset of a lean condition. When a mixture goes lean you have a situation where fuel is being injected into the intake and it is mixing with air to make up a highly volitile mixture, that when burned, burns fast and hot. When the fuel cut hits, it does not inject fuel, so half of the equation for a lean burn doesnt exist. Injectors are able to turn on and off rather rapidly, so I am compelled to think that they wouldnt let any fuel out after being commanded not to. I have been wrong before though.

An interesting topic. If you get your project going, maybe we could change its intended use and make it a staging light "ignition cut" to help the maintain a certain RPM at the lights.

Take care,

 

[myclone]

On 2001-12-01 09:54, Daron wrote:

On 2001-11-30 15:19, myclone wrote:
Daron,

Point well taken.... BUT (aint that always the case??). Whats the diff, as far as detonation, between cutting the fuel at a high boost and say... running out of inj capability and running lean.

Now, correct me if Im wrong here... Id rather have raw fuel dumped into the comp chambers with nothing there to light it off (other than cyl pressure) than too LITTLE fuel as would be found when a "fuel cut off" condition occurs..

<font size=-1>[ This Message was edited by: myclone on 2001-11-30 15:21 ]</font>

It is my opinion that the fuel cut is not like a lean condition, or promote the onset of a lean condition. When a mixture goes lean you have a situation where fuel is being injected into the intake and it is mixing with air to make up a highly volitile mixture, that when burned, burns fast and hot. When the fuel cut hits, it does not inject fuel, so half of the equation for a lean burn doesnt exist. Injectors are able to turn on and off rather rapidly, so I am compelled to think that they wouldnt let any fuel out after being commanded not to. I have been wrong before though.

An interesting topic. If you get your project going, maybe we could change its intended use and make it a staging light "ignition cut" to help the maintain a certain RPM at the lights.

Take care,

Daron (and everyone else),

Thanks for the info.. I was under the assumption that the ECM dropped out the FP relay not cutting the PW to the injectors. If that is in fact what happens (inj pw=0ms) then the very short lean condition Im thinking happens actually doesnt. Well, its VERY short if it does and is prolly negligable..

On to the ing cut thingy Im tinkering with... In my experience most tracks that I race at wont let you use a starting line "rev limiter" or other ign cut device in the "foot brake" class. Only the pro cars are allowed to use it. Needless to say I am WAAAAAAYYYY too slow for the pro classes.. :sad:

The above idea is actually a second use I came up with for the extra 3 bar. The original idea was to use it for boost indicators (LEDs) I could mount to my helmet in the line of sight so I could concentrate on the tree.

Basically (theres a little more to it but I'll save you the boredom), I have a small alum bracket mounted to the windscreen on my helmet with 3 LEDs in such a way they are in front of my left eye. One yellow, one green, one red. Yellow is set up to come on .5 lb below my target launch boost. Green is set for the actual target boost and the red LED comes on at .5 lb above target launch boost.

Once staged I can watch the tree and the LEDs at the same time easily. No glancing at the boost gauge and back to the tree if I get stuck in the left lane.

Just came up with it due to me having trouble cutting good RTs consistantly due to trying to keep up with the boost gauge and the tree all at the same time. Just my old senile mind getting overloaded I guess... :grin:

I have yet to install it on the truck but I have tested it out in my electronics shop at work using pressurized/regulated nitrogen for my "boost". Seems to work ok.

Its a very simple ckt to make.. Prolly cost less than $5.00 in parts.. If you can solder, have a DVM you can make and set it up.

If you have other uses lemme know as I have just about an endless supply of analog electronic parts(op amps, transistors, gates, scrs, etc..) to play with and 12hrs a night(usually) to play with them.

 

[JoeLutz]

For there ot be a instant of lean condition due to fuel cut, wouldn't that mean that there is still a small amount of fuel coming from the injectors, even though the injectors are completely denergized (0 ms pulsewidth)? And if so, wouldn't that mean that the injectors are leaking? Under boost, the fuel pressure is much greater than at idle or normal operating conditions, so wouldn't that make the injectors more likely to leak a little under that high fuel pressure condition? Just a couple thoughts, please no flames.

 

[rockvillespeed]

guys, here's the deal in the aftermarket (mostly ford) world - bear in mind i do this all day long for a living - i would never ever ever ever set up a customer's car (blown or n20) with a fuel base rather then ignition base rev limiter given a choice. if you bounce ino it repeatedly, you absolutely can lean it out for very brief periods. i would strongly recommend using a rev lim built into whatever ignition box you may choose set 100 rpm lower then any fuel cut you may have.
frankly, tho, i feel a rev lim is almost a waste of $ on a syty given their traction....will save the motor in event of, for example, drivetrain failure. mine is set at 5k rpm, and its never been near it (tho, in deference to 195000 plus miles on the motor, i dont spend a lotta time manually shifting - mine changes wot at about 4400 rpm

 

[myclone]

rockville,

Im right with you in the though process and thats why I asked the question to begin with... (dont take that as a slam :grin: .. everyone knows my LACK of thought...)

Judging by your post you understand that rod bearings (along with a few other parts) HATE (repaeat: HATE) detonation..

I dunno but it sounds like you like to watch out for your bearings like I do... Good job.. :grin:

 

[jwaller]

hey with myclone on the prowl your rod bearings aren't the only thing you need to be watching out for.

 

[Daron]

On 2001-12-02 03:47, rockvillespeed wrote:
guys, here's the deal in the aftermarket (mostly ford) world - bear in mind i do this all day long for a living - i would never ever ever ever set up a customer's car (blown or n20) with a fuel base rather then ignition base rev limiter given a choice. if you bounce ino it repeatedly, you absolutely can lean it out for very brief periods. i would strongly recommend using a rev lim built into whatever ignition box you may choose set 100 rpm lower then any fuel cut you may have.
frankly, tho, i feel a rev lim is almost a waste of $ on a syty given their traction....will save the motor in event of, for example, drivetrain failure. mine is set at 5k rpm, and its never been near it (tho, in deference to 195000 plus miles on the motor, i dont spend a lotta time manually shifting - mine changes wot at about 4400 rpm

A fuel cut in a Nitrous system is apples and oranges.

Keeping this topic in context, we arent discussing using a fuel cut to limit RPM. We are discussing the pros and cons of using a fuel cut to stop overboost. Our ECM completely shuts the fuel off once overboost occurs. You cannot "bounce off" the overboost in a SyTy like an ignition cut out. It effectively shuts things down for a few seconds, so your comments there don't apply.

A rev limit at the staging lights was discussed, to assist the launch of a SyTy. Not sure about your Sy or Ty, but if I leave with too many rev's, my tires will light up. It is difficult to maintain a certain RPM and boost level at the light in our vehicles, a rev limit has helped SyTy folks be more consistant in the 60ft by maintaining a set RPM at the line.

Again, we are discussing stratagies to limit boost in a SyTy with stock ECM, that includes a turbo system. We were not debating limiting RPM's in a NOS, or supercharged vehicle.


_________________
Daron
1992 Typhoon Blue/Gray
1991 Syclone Best 1/4 12.42 @ 106.1
Member Of Freakin' Ohio (MOFO) SyTy

<font size=-1>[ This Message was edited by: Daron on 2001-12-03 12:55 ]</font>

 

[JoeLutz]

I've owned a few turbo cars both foriegn and domestic including MR2T, 3000GT VR4, Daytona, and of course the Ty. Anyway all of these vehicle's overboost protection was through fuel cut. There must be some reason for this.

 

[myclone]

On 2001-12-02 08:33, jwaller wrote:
hey with myclone on the prowl your rod bearings aren't the only thing you need to be watching out for.

If youre skeered say youre skeered!! :grin: :razz:

Listen ppl,

I, in NO way, meant for this to become a flame fest between ppl of diff thoughts/opinions.. I learned alot from this thread that might be common knowledge to some but not me.. Sheesh..

"Bouncing off overboost" was just my commedic way of explaining (geeky/nurdy voice ON) "I experienced the symptoms of exceeding the maximum allowable positive manifold pressure at a given internal combustion engine loading scenerio" (geeky voice OFF). If you keep your foot matted then you will get the "feeling" of bouncing off the overboost fuel cut. Similar to a rev limiter. Not as violent or rapid (IMO) but still similar. Trust me... As Im sure most everyone on here has, Ive "bounced" off both of em.. (NOT on purpose BTW)

Now... Whats the deal with the fuel cut at over boost. Looks like we "think" it cuts the inj pw to 0ms.. Does it or does it drop the FP relay out?? The 0ms inj duty cycle seems to me to be the smartest way to do it but we ALL know how GM thinks so IMO it could be either way..

Does someone know for sure or do I have to go out and put a DVM on the FP relay and go bounce off the overboost feature?? (IM J/K!!!)

Later..

 

[smeagol]

I'll say it again :wink:


Fuel cut, pulsewidth = 0 milliseconds

BG