I didn't think 4 EGT probes would have the accuracy to calculate adjustments in injector flow. The only time I use one is to detect knock on a car I can't log the PCM.

You may find its much more cost effective to fabricate a return fuel system. Just imo tho.

 

Or use a boost a pump to keep the pressure up.

 

Never used one, do they get the job done decently?

 

Subscribing to this one. This is a good, information bloated thread.

 

Fixed!

 

Exhaust gas temperature Probes Tapped into each exhaust primary. This way you can pinpoint leaner cylinders. http://www.altronicsinc.com/pages/redalert.html
handy little tool. Most aftermarket logging boxes such as the Racepack are able to log egts. Very handy tool if you are running a sequential system Like Fast accel or bigstuff3 where you can add fuel to individual cylinders. For the LSJ putting a bigger injector in the leaner hole will work well too.

 

Thats the route I am taking for my nitrous setup. I talked to a couple ecotec people and they recommend that over converting to a return style for the results I am looking for. Which is being able to keep up with the increased fuel needs of a 75-100 shot.

It's supposed to keep the pump duty cycle down. I don't exactly see how converting to a return style would fix the problem, unless you are upgrading the pump to something bigger and better. If the pump is having trouble keeping up how does the placement of the regulator make a difference? Of course with a return style lets you have an adjustable FPR.

If you don't necessarily want to muck around with fuel pressure I would give that a shot because it's much easier than a conversion.

 

This is all my understanding of how it works, so I might not be 100% in this assumption.

Converting to a return style system allows fuel pressure to be regulated at the rail instead of at the pump. On our cars, fuel pressure is regulated at the pump in the tank and commanded higher or lower by the PCM. With an fpr, that pressure is regulated at the rail and provides a more consistant pressure across all injectors as the regulator is placed at the end of the rail. Its not necessarily commanding more pressure or making up for a lack of pressure due to a maxed pump, just simply allowing for a uniform pressure.

As far as the above post about EGT probes, I understand how they work, as I said, I use one for tuning for knock when I can't scan the PCM, however to actually rescale injector flow rates, I didn't think you would have the pinpoint accuracy that you would need. Those ones linked above I'm pretty sure are made for warning lights when individual temperatures start exceed piston melting range. If they do have decent accuracy between each probe, then the injector idea is definetly a solution to a problem I think a lot of people are running into. Again, this is just all imo.

Let me further clarify what I'm trying to say about the EGT probes. I'm going to exaggerate the numbers to get my point across.

Lets say cylinder 1 is running 12-1 a/f ratio and cylinder 4 is running 13-1. Now your EGT temps may be only a 20 degree difference. How are you going to calculate injector flow rates based on unknown A/F, not being able to tell what the actual difference in a/f burn actually is. Cylinder 1 could be 12.4-1 and cylinder 4 could be 12.6-1 with a 20 degree difference, now which scenario would be correct?

 

I see I'm not the only one who believes in this theory!

 

a turbo is not noticably more restrictive than a stock catalytic converter, which most turbo setups will delete, so parasitic loss is almost nill.

 

The whole return fuel system argument might be a viable argument for why its always #4 cylinder that tends to blow up.

 

really? but they have spent so much time and money.

 

Ah but then you are again talking about changing more than one dynamic of the system. I guess I should have said, all else being the same. I also said that it was minimal.

I was unaware of the fuel rail/AF ratio issue. To be honest my understanding is more towards the mechanical/scientific theory and workings than the specific configuration.

I am a bit confused as to how, if our fuel rails are pressurized and injectors flow matched, how the AF in the cylinder itself could vary from cylinder to cylinder. In a sealed pressurized environment all areas are pressurized equally regardless of their location, correct me if I'm wrong about this, and the purpose of flow matching the injectors is to ensure that each injector inputs the same amount of fuel into each cylinder regardless of it's position on the rail. Again, please correct me if I'm wrong about this.

 

It could be the manifold design that is an issue. On the Ls1 based engines the intake manifold design always has number 7 running leaner than others. Without testing these are just wild claims.

 

This actually makes more sense to me. If the manifold design is flawed allowing more air to flow into a particular cylinder then a lean condition would be created. I still fail to see how a pressure equalized, flow rate matched fuel injection system could introduce less fuel to one cylinder than another.

 

Pretty sad as of over two years, the amount of cobalts out there dont even produce 300hp,....

 

No big company has ever picked up the car, what do you expect? Gm has told everyone how to reach 300hp but not everyone has the means to do so. I'm already half way there with my bottom end done and I'm doing the head during the summer months and then I'll be spraying on top of that so I'll have 400whp on bottle when im done around december or so but theres been alot of planning around my car. Everyone on and off this site need some kind of bolt on something that can make thier car over 300whp and sad to say so but without nitrous or meth on a 2.7" and running crazy timing there really isnt gonna be a solution to this problem. The good thing about turbo cars is "hey you want big power?, here's a better turbo and holy crap it bolts up with no problem" Superchargers aren't that convienent. Maybe Eaton's new line of TVS chargers might change the world with this car but until then or if some other supercharger kit manufacturer feels the need to jump into this car and throw a better blower on it I'm confident in saying a reliable 270whp LSJ is the best your gonna see.

 

In response to the fuel pressure debate:

You're trying to flow 4 times the amount of fuel in one end of the rail as you are the other, theres going to be a pressure drop at the end of it.

Some GM based V6 PCMs allow for an option to "skew" each injector to correct for differences in flow in the injector, rail, and manifold. See attached pic of a 3800 V6 tune.

 

ok, admittedly, I'm confused now. How is a set of flow matched injectors attached to what is in essence nothing more than a pipe with holes in it, trying to flow more fuel at one end than at the other?

That came out condescending and it was not meant to be, I really am confused.

It is my understanding that the fuel rail is pressurized. That pressure is maintained by the fuel pump. The release of said pressure is when the injectors open to flow fuel into the cylinder. Now... given that the pressure in a closed system is equal at all points in that system and the flow rate of the injectors is matched, how can one injector input more or less fuel into a given cylinder than another based solely on it's location in the closed system?

 

yes it is....lmao three people have me quoted in their sigs now.

 

You have to understand the difference between a return and returnless style fuel system and how they work.

On our setup, a constant fuel pressure is maintained, regulated completely by an in-tank regulator. As a higher pulse width is commanded from the fuel injectors, the regulator allows a higher flow rate to maintain the preset pressure. However, the entire fuel system acts as a flow restriction at some point, lines, hoses, and fuel rail included. As you upgrade to larger injectors, you're demands on the fuel system increase as well as the increased boost the injectors also have to flow against. Because the system becomes a bigger flow restriction as the flow requirements increase, the difference of what is regulated at the fuel pump to what is seen at the last injector at the end of the rail, begins to grow. Now our PCMs can overcome pressure differences by simply commanding a different pulse width, which is basically what an IFR table is setup to do. However, the delta pressure value between injector one and injector four will increase as fuel pressure drops from the feed line. The fuel pressure drop is because of the increased restriction as flow demands increase as mentioned earlier.

Now on a return style fuel system, the regulator exists on the fuel rail itself. A key component to this system is the regulator that adjusts fuel pressure based on manifold pressure. It always keeps "X" amount of pressure above manifold pressure no matter what. Since the regulator sits on the end of the fuel rail, flow restrictions such as small feed lines don't have as a negative effect on the regulators adjustments, since they exist between the regulator and pump. If small lines present a significant fuel restriction, the regulator simply commands more fuel until the restriction is overcome and the desired pressure is achieved.

This can only be accomplished on our setup if the regulator in the tank is removed from the system and the fuel pump can flow what the new regulator allows.

This was how it was explained to me by people much smarter than I. If anyone finds anything incorrect, feel free to comment.

 

Exactly, no company will EVER bother taking the dedication to the cobalts, its too longgggg, considering that its easier to work on the Scions, Civics, Lancers, SRT-4's, Mazda rx-7 or 8 etc, acuras........

Even cars that dont have any superchargers or turbos get more boost


My Personal opition....
Its common fact that GM needs to rethink a brand new structure of the ECOTEC 2.0. Make it look different, MAYBE BIGGER?

 

I think that trumps everything for the most ignorant statement on this site.

It's not that its easier, they think the cobalt looks ugly they had a dog run over by a cobalt. That doesn't matter. It goes down to the simple fact that none of the big wigs at companies that matter think that the investment they will put into making stuff for the cobalt will make money for them. Companies arent in business to make your car go faster they're in business to make money. They want to sell you crap and for the most part guys with Redline or Cobalts are too cheap. I could personally name all the guys on here and on the RLF that are putting money into thier cars. These big companies want lots of people to buy thier crap, not 20 or 30 guys.

 

I don't disagree with that at all, if you are flowing more fuel you might see a pressure drop at the end of the rail. If however you boost up your pump to be able to keep up with the pressure drop it might fix the problem.

Without lots of tools and data logging that I don't have it's impossible to tell.

 

Ok then, and your responce?


[/QUOTE]It's not that its easier, they think the cobalt looks ugly they had a dog run over by a cobalt[/QUOTE]


Are you sure your not speaking for yourself? or did i miss this quote off a Super Street maganize? I want to see a link from any company that thinks cobalts are "dog run over".

and...

when i say EASY, "Its eaiser to gain 500 hp off a scion Supercharger". thats all, it was an example.

Many Companies modefied other compact sport cars like nothing, Their having a hard time adding at least 80 hp off a stock 2.0 ecotec S/C.

Still,

My Personal opition....
GM needs to rethink a brand new structure of the ECOTEC 2.0. Make it look different, MAYBE BIGGER?