Area47

you're trying, i'll give ya that.
the fuel pressure does not change in the lsj. it is a static number. how ever the volume changes. it has too. one or the other must.

99% of the "boost a pump" set ups are not recommened for returnless systems.

06blackg85ss

iTrader: (1)

I hear ya man, and I do agree with what your saying. I believe it's only a matter of time now before my stock fuel pump ***** out on me. I do want to run a rising rate regulator and return style fuel system with at least 1 maybe 2 walbro 255's should give me all the fuel I need. For now I'm just trying to find the limits of the stock setup, engine, fuel system, and tranny (thats the reason I"m building another motor goot to 750hp)

mrdoc442

you've monitored your F/P at Idle as well as WOT and it does not change with larger injectors? Impossible. Yep the volume changes alright, without greater fuel pressure to compensate for the larger injectors volume has to go down. If volume goes down you run the risk of running lean/ detonation/ bye bye engine. A static number is hardly going to compensate for the difference. Prove to me it otherwise, and please enlighten me to your acquired expertise in this regard, if you don't mind. Not trying to pick a fight, I've given my background, except I didn't mention 30+years of NHRA drag racing on the professional level, mentioned a few of the vehicles I have fiddled with, I'm just curious about your credibility, experience, and background.

By the by, the GT500 has an electronic fuel injection system, a top quality returnless and sequential force feeder, and " Exclusive Kenne Bell Dual BOOST-A-PUMP™ included with all GT500 kits. Larger pumps, fuel rails, lines etc. not required for the GT500".

Must be in that 1% you are referencing.


Doc

06blackg85ss

iTrader: (1)

I've seen some pressure drop, but not by that much only a few psi, my base fuel pressure at idle is about 62-63psi and at WOT it drops toeh the mid to low 50's

mrdoc442

across to the other gentleman.

I could be mistaken, as I am new to the Cobalt, but boosted is boosted, and my advice to you is to be very careful. With my GN I had 45# @ idle, and 63# @WOT with 18# boost. The rule of thumb there was one extra # fuel for every # of boost @ WOT (18# boost + 45# f/p @ idle = 63# fuel required @ WOT. I melted a set of brand new AC CR42TS spark plugs in my Typhoon trying to get the pressures right. I mean melted very thick ground straps limp as pieces of licorice. Luckily the knock sensor pulled enough timing so that I didn't melt holes in the tops of my pistons or scorch the valves.

I don't see where the boosted or turboed LSJ would be any different. Lean is lean. There is no way the fuel pressure is keeping up if going lower @ WOT.

As I said, I am not a master LSJ tuner, but common sense ususally prevails.


Doc

06blackg85ss

iTrader: (1)

read my other post, stock fuel system is coming out real soon... everything is being taken into account, as I said just pushing the limits of the stock stuff to see what it will handle

mrdoc442

It. Sounds like you have a good handle on what is going on.

The Cobalt system is no doubt different as is the GN from the Sy/Ty, but the boosted principles are still common to forced induction vehicles.

I just hate to see some of these folks thinking that the answer to all their tuning woes is sticking in a set of 60# injectors.

I didn't mean to imply that the "boost a pump" was a direct fit for the Cobalt, but if anyone has the background to figure out what would work with a turbo Cobalt, it would be Kenne Bell.

The GN folks went through the same high performance growing pains over the years as no doubt the LSJ folks will go through in years to come.

Good luck.

Doc

06blackg85ss

iTrader: (1)

I was lookin to go with twin pumps and a nice return system with a rising rate fuel pressure regulator (going for over 550hp with new motor) But yeah a lot of the others don't take that stuf too much into consideration. Hopefully if I have time tomorrow I"ll start doing the math and figure out how to run everything on the car, if worse comes to worse I"ll probably end up running a fuel cell in the trunk, at this point I'm a little stuck on what to do until I go stand alone cause I don't know how the car is gonna react computer wide.
But as you were saying I was looking over some of my logs from this week and I can see it start to lean out away from commanded AFR up top, so that's probably the cause

mrdoc442

an email and asked for some ideas. If and when I hear back I'll shoot you a pm with what he says.

In the mean time, take a look at some of my posts on cooling, thermal heat reflective tape, removing the little sight cover over the fuel lines, removing the rear hood seal-just pops off. The cooler the engine compartment the better for performance. With the rear hood seal on the heat is trapped in the engine compartment, and heat soaks everything. With it off the heat escapes and the engine begins to cool as soon as you shut it off. Take it off, take a drive, and stick your hand up by the bottom of the windshield and see how it flows out whan you turn the engine off. I covered every bit of fuel line/logs with thermal tape, as well as the air tube into the throttle body.

These things aren't the answer to all your concerns, but with cooler/denser air and fuel, you will get the most bang out of whatever your fuel pressure is. Using some Lucas or other good octane boost is a good idea also. I use Isoprophol as well - the red Heet - all year around. A little alcohol in the fuel tends to cool things a little, and helps keep the fuel lines, and injectors clean also. These things might not make a big difference, but could provide a little insurance against harmful detonation. I use Redline SI1 fuel system cleaner religiously too.

My little Cobalt runs pretty darn good for what it is. At my altitude 5000 + (D/A), it will shred the front tires on any kind of pavement at any speed in first gear, halfway through second.

Doc

06blackg85ss

iTrader: (1)

definitely let me know what they say.
As for temps, I dont have the fuel rail cover on the car anymore, but heat is an issue with the turbo, **** gets damn hot under there, looking to get a vented cf hood soon anyway though

Area47

i put 60's in the car because my 42's were cooked. i had pushed them way to far for too long. im not dropping pulleys, im not doing anything radical. i don't feel the need too. traction is already an issue, and i blew my original whp goal out of the water with the 42s.

the fuel pressure is what he said. it does vary vehicle to vehicle. oddly enough it works. scary at times. but it does.

i will be the first to admit, i have not dug into the fuel side enough to have an exact answer on how it works. so you're guess is as good as mine

mrdoc442

Honesty and candidness .

This is for you and 06blackg85ss.

I was rummaging around in some of my old Grand National data and came across some of Red Armstrong's tips. He is a GN Guru who has won and set many GN records at the Buick Grand Nationals held at Bowling Green each year.

I'll put all his stuff in quotes. We sure hijacked this thread - :+) LMAO

Fuel is paramount with boosted applications. Probably the biggest reason IMHO for catastrophic engine damage is running lean. Applies to N/A also but is magnified w/boosted applications.

Keep in mind that this is GN stuff, but the principles are similar for all boosted applications, even if the values/numbers vary a tad.

"For every #you increase or decrease the fuel pressure you increase or decrease the fuel flow by approximately 1.1%. So by increasing fuel pressure 7 pounds, you increase the fuel flow about 8%, which puts 8% more fuel into the engine. This allows you to make 8% more H/P if you maintain the same fuel to air ratio."

"The following 6 items are correct at reasonable pressures and voltages."

" 1. If you go up in fuel pressure, injectors will flow more fuel."

"2. If you go down in fuel pressure, injectors will flow less fuel."

"3. If you go up in fuel pressure, all fuel pumps will pump a lesser volume of fuel."
"(This is not a misprint.)"

"4. If you go down in fuel pressure, all fuel pumps will pump a higher volume of fuel."

"5. If you go up in voltage, within reason, all direct current electric fuel pumps will pump more fuel (especially true at higher fuel pressures."

"6. If you go down in voltage, all direct current fuel pumps will pump less fuel."

"As you can see from the above principles, when you increase fuel pressure or go to bigger injectors, you put a much bigger load on the fuel pump, maybe too much of a load, depending upon the pumping system."

"Voltage is very critical to the pumping capability of any pump. If you go from 13 volts DC to 14.3 volts at the pump, a 10% increase in voltage, you will typically increase the pumping capability of the pump by approximately 20%."

"One of the least understood things about the fuel system is volume and pressure. We need both at the fuel rail."

"Remember if you put more fuel into the engine without changing the boost, you will be richer. If you increase the boost without increasing the idle fuel pressure you will be leaner."

"All of this stuff only makes sense if the fuel pump is capable of pumping a sufficient
Volume of fuel at the pressures required."

"Detonation is caused by many things. In the case of the GN, it is most caused by the following things: insufficient cool water going through the cylinder heads; too much boost for the octane; too lean a fuel mixture; too much timing; too hot a charge into the engine; or a combination of the above. There are many other reasons for detonation but these are the most common for the Turbo Regals."

So you can see what a can of worms this balanced fuel/boost stuff gets to be when you depart from the factory settings. In actuality, some concepts are just the opposite of what a person would think they would be. I firmly believe that frequently, once folks start modifying their cars with bigger injectors etc., very few take the time and trouble to learn things they need to learn to get everything balanced right. They get caught up in the calibration aspect, and neglect the F/P/Fuel volume/boost issues.

Another thing that comes to mind with my recent experience with my Cobalt is making sure the spark plugs are torqued properly. I don't mean cinching them down with a regular ratchet, use a good torque wrench. When I replaced my factory plugs with the NGK Iridium all of my plugs were barely over finger tight from the factory. I am a little leery about over-tightening plugs going into an aluminum head, so I just cinched the Iridium plugs down tight with a regular ratchet. I checked them a couple days ago and they were all barely just over finger tight just like the factory plug were. The washers were not collapsed as they should be (they weren't on the factory plugs either). So I got the torque wrench out and after snugging the plugs up with a regular ratchet, I torqued them all, in pound increments until I got to 16#. The factory manual recommends 15# and NGK recommends 20# for aluminum heads. If the plugs are not in tight enough, several things happen, all bad. The plugs overheat and the combustion chambers also overheat because the plugs cannot remove the heat properly through the heads/water jackets/cooling system. And we know what this leads to. Yep. Detonation. Very simple exercise, but I wonder how many folks do not take the time to actually torque their spark plugs? Make sure you do not overtighten them, because you can get a lot of snot on a torque wrench, that's why I bumped them up a little at a time. A striped plughole or busted off sparkplug in the head is just plain nasty, and I guarantee it will ruin your day, especially if the head has to come off. I did not use anti-seize. The shop manual says to not use it as it can squewer the torque readings and make it easy to over-torque the plugs. Just make sure the threads in the head and on the plug are clean and you shouldn't have any problem if you don't over-torque them. You guys with high boost and serious mods need to especially pay attention this detail. I also gapped the plugs at a tight .035 with a wire gapper. Kenne bell recommends this gap pretty much carte blanche for modified boosted engines (along with one step cooler). Do not use the stainless steel tappet gauges, they do not reflect an accurate gap. Don't use the round graduated gauge that spreads the center electrode either, if you use Iridium plugs, as the fine, sharp point with the Iridium will catch and break off very easily-experience speaking. My NAPA was gracious enough to let me warranty the plug, but they really shouldn't have, it was my own stupidity.

A lot of my suggestions with cooling, thermal tape etc., are just little things, but enough little things add up to a lot of difference.

Hope some of this helps.

Good luck.

Doc

Area47

i check the plugs, and other little things here and there every week. preventative maintanence. i got this from owning a dsm for a number of years. you get used to it.

mrdoc442

DSM. It could stand for a number of things.

Doc

06blackg85ss

iTrader: (1)

diamon star motors.

Area47

talon, eclipse, laser

mrdoc442

0ff. It just snaps to the black plastic piece below the windshield, comes off real easy, and is easy to put back on. The engine compartment air really flows through with it off, especially when the vehicle is moving, much like heat extractors.

The more I think about you going 18# + of boost, it would be a really good idea to make sure your fuel is as high octane as possible. That is sort of the boost cut off point with turbos and S/C's, where high octane race fuel is required. Of course leaded race fuel will poison your cat conv-if you are running one, and O2 sensors. Most racers run real high octane unleaded if it is available - like 100 with some octane boost - or if race fuel is the only thing available, they just change the O2 sensors when they expire from the lead.

At those high boost levels, harmful detonation is pretty much a given, though keeping the fuel and air cool will help quite a bit, you are asking for trouble without high octane fuel as well.

Doc