my tuner figured out why my car was running lean.

[ADRENLN]

well, if you guys remember, i had l/t installed and was getting dyno tuned last week. however the car kept running lean between 2000-3000 rpm. he thought my maf was pegging, but we kept think not at this power level.

turns out to be my injectors. the stockers are open all the way, they are completely maxed out. tuner said that any power mod i add after this i will have to go bigger injectors. he can make it work with these now that he knows this is the problem. he wasnt even thinking that was the problem, said he was shocked. he will now raise the fuel pressure and see what we can do.

hope to have it back tomarrow.

 

[RandyStinchcomb]

well I have to dis-agree. the stock injectors will support 300+ hp and wth your mods, I just dont see it being an injector problem, unless 1 or more is bad.

 

[ADRENLN]

yea i was wondering if maybe a bad injector would cause this. then he still might not be able to fix the condition. well i hope he can do somthing with it for now then i can buy all new injector for it next time just incase. id go bigger when i get them cause ill need bigger eventually anyway.

i only have 10,500 miles on my car, do injectors go bad that soon?

 

[RandyStinchcomb]

well, I've seen injectors last 100,000 miles or more. it's possible for them to crap-out early, if they are over worked they can go bad but at only 10k yours should still be covered under 3/36 warranty.

 

[sgarlic]

I also am not seeing the kind of mods that would peg out the stock injectors.. I'm starting to wonder if perhaps your tuner has little to no Mustang experience or something.

 

[jstreet0204]

According to this chart it is crank hp used in the calculation, which would put him in the 100% duty cycle range.

HP vs. Injector Flow Rate

The following chart displays the maximum obtainable CRANKSHAFT horsepower vs. injector flow rate at 100% duty cycle, assuming a BSFC of .55 lbs./hp/hr. For Wankel and 2 stroke engines, multiply max hp in table by 0.9 to compensate for the higher BSFC of these engines. Injectors should be sized for 75-85% maximum duty cycle on engines used in constant high power applications such as race cars, aircraft and boats.

 

[DBMSTNG]

According to this chart it is crank hp used in the calculation, which would put him in the 100% duty cycle range.

HP vs. Injector Flow Rate

The following chart displays the maximum obtainable CRANKSHAFT horsepower vs. injector flow rate at 100% duty cycle, assuming a BSFC of .55 lbs./hp/hr. For Wankel and 2 stroke engines, multiply max hp in table by 0.9 to compensate for the higher BSFC of these engines. Injectors should be sized for 75-85% maximum duty cycle on engines used in constant high power applications such as race cars, aircraft and boats.

i'm betting that's for return style fuels systems and doesn't apply to returnless.

 

[DBMSTNG]

well, if you guys remember, i had l/t installed and was getting dyno tuned last week. however the car kept running lean between 2000-3000 rpm. he thought my maf was pegging, but we kept think not at this power level.

turns out to be my injectors. the stockers are open all the way, they are completely maxed out. tuner said that any power mod i add after this i will have to go bigger injectors. he can make it work with these now that he knows this is the problem. he wasnt even thinking that was the problem, said he was shocked. he will now raise the fuel pressure and see what we can do.

hope to have it back tomarrow.

he's just guessing.

 

[jstreet0204]

i'm betting that's for return style fuels systems and doesn't apply to returnless.

I don't think so. I just checked my SCT tuning manual and they use the same formula and they use crankshaft hp as the reference number. It makes no mention of it being different for the two systems except that the return style system will adjust pressure accordingly, or can be set manually in the EEC.

 

[Don 95Vert]

How lean is lean? Did the dyno run end at 3000? If so, something else is wrong - did it get lean at 3000 and then stay lean to 5000 - if so, it may not be transitoning to open loop or the aircharge switch may not have been changed in the tune as it should.

Return style, returnless, it it doesn't matter, injector can only flow so much fuel. With a returnless, you can raise the pressure drop across the injectors to act like an electronic FMU as long as there is enough pump - and at that HP level, there should be.

If he is an SCT tuner and needs some help with it, tell him to give me a shout, be glad to help him out - and I am NOT saying he doesn't know what he's doing, we all get cars that have problems that make us scratch our heads from time to time and sometimes another opinion helps.

 

[hognutz]

It has to be something else becaue too many people are running that kind of hp with stock injectors just fine.

I can't recall maf or injectors ever being the issue at that power level.

unless there si something unique about your setup. I would email some of the better know tunners and ask for their input on this. if this can happen they should have experienced it before.

 

[ADRENLN]

no it doesnt stay lean. its only lean from 2000-3000 rpm. the rest of the way it is fine. i was not at the shop yet, but i think he said it shot up to almost 14 or13.8 somthing like that. i was only on the phone with him, so i really couldnt get all the info.

maybe it not the injectors, but the fuel pressure might just have to be raised. he did say they are pretty maxed out though. i would hope he could tell if an injector was maxed out or not. hes been doing mustangs for a long time.

if we are talking flywheel/crank hp my car is at 320hp now with the off tune.

ill let you guys know what happens

 

[reeber]

320 is a good number. Your getting there pretty quick! I am sure Craig will figure it out. He just usually needs time to think about it a little bit and try different things with the chip to see what the car does. He always seems to find the answer though. I am sure you remember my idling issue... FIXED, but it did take him a bunch of different setups until it worked. I had two other very reputable tuners try to fix it, but Craig was the only one who could.

 

[mrvax]

well I have to dis-agree. the stock injectors will support 300+ hp and wth your mods, I just dont see it b
eing an injector problem, unless 1 or more is bad.

Randy, I have to disagree with you a bit here. (And I have a lot of respect for you.) MJchip, the engineer that used to post here showed that the 19lb injectors went to full duty cycle at just below 300rwhp. They were pegged. I wish I saved off his calculations.


I don't want to imply that the injectors are the problem in this case. He should be fine up to about 295rwhp.

 

[hognutz]

what kind of dyno was it? I was just looking at you sig and it seems like you should have more hp. I would think with your mods you should be in the 300hp range. unless I am missing something.

most cars I have seen with heads, cams, longtubes, plenum tb are all ~290-310hp. that is dynojet though. now mustang dyno or something could scew the resuts a bit.

maybe I am completely stupid but why would it not get worse at higher rpm?

fuel requirments should go up shouldn't they. if it were really injecor duty cycle shouldn't the problem be worse as load increases and more fuel is required?

 

[ADRENLN]

most guys with my mods are 290-310 rwhp, hmmmmm. well, im at 286rwhp with somthing wrong with my tune. i dont know if numbers will increase if we fix it. however even if i stay at 286, i have blower cams. so if i had na cams like most of the #'s you see that are 300rwhp, id prolly be right around 300. its is a dynojet,so its about right.

hey trust me, ill take more power if theres more to be had.

anyway i was thinking the same thing about it staying lean or getting leaner as rpm increased? i dont get why its only in the low rpm

anyone have any ideas?

 

[Don 95Vert]

Guys, it is NOT the injectors - he said it is fine from 3000 RPMs and up - it isn't going to suddenly run out of injector at 2000-3000 and then magically increase in capacity past 3000, in the area where it requires more fuel. My guess is the aircharge switch isn't set right or the OL delay is too long in the EEC. Your tuner should be able to fix that. Or there is an outside chance you have a vacuum leak that is worse for some reason at 2k and seals up past 3k because of air velocity.

BTW: Glad to see that some of you are reading the manual I did for SCT!!

Good luck with it.

Don

 

[jstreet0204]

Guys, it is NOT the injectors - he said it is fine from 3000 RPMs and up - it isn't going to suddenly run out of injector at 2000-3000 and then magically increase in capacity past 3000, in the area where it requires more fuel. My guess is the aircharge switch isn't set right or the OL delay is too long in the EEC. Your tuner should be able to fix that. Or there is an outside chance you have a vacuum leak that is worse for some reason at 2k and seals up past 3k because of air velocity.

BTW: Glad to see that some of you are reading the manual I did for SCT!!

Good luck with it.

Don

I agree, when he said it was running lean between 2 and 3k in the first post, I assumed he meant that is where it started, and kept running lean afterward.

Edit: I know EECV measures pressure drop across the injectors and adjusts the flow rate. Could it be that this is the correction you see after 3000 rpm?

To the original poster, was your tuner datalogging anything? Most of these theories could easily be validated or disregarded with the info in some datalogs.

 

[ADRENLN]

well we know the injectors can handle it now, that is not the prob. you guys are right. we are just trying to track it down . i finally got to see in person the dyno sheet. it runs lean from start all the way up to 4000, then richens up. i dont have any data logging info, but i can post the dyno so you guys can see what i mean.

[/IMG]

 

[reeber]

I have a random guess... Your cams are setup for a blower, so they are looking for a lot more air at higher RPMS and probably giving you a lean spot now that you put the long tubes on because it's letting air out of your engine quicker, leaning it out til the cam kicks in at 4000... Just a guess, without seeing any logs..