OK I know I may be chastized for this, but I did spend a lot of time searching and found some info but am still left with questions. I Have a pretty aggressive 305 setup and am trying to get it tuned out. I just got all my stuff for Prom burning/ editing.
Now with the MAF setup what tables are your main fuel tables? The MAF tables? I basically have a well idling and cruising car, but when you floor it the air fuel ratio spikes lean to the point where it almost falls off the gauge. Not losing fuel pressure, everything seems OK just seems like it isn't getting even close to enough fuel when under heavy load. Any ideas?
Could it be more than state of tune issues in the ECU?
I am running a Walbro 255lph HP pump so I don't think I have fueling problems? Is it possible that the Big cam/headwork and bigger valves change flow enough to make it stumble under load and lose power to to an overly lean cond.?
LT4 cam
305 with ported heads, Bigger intake valves, lots of head work etc..
Need to get things figured out. Again it idles well, and cruises well, but any hard acceleration makes it lean out bad. Just want to know if I have a mechanical gremlin like a fuel flow issue or if it is a function of way too much motor on a stock 89 chip.

 

Stock injectors? You may have stepped out of their range of ability.

 

Hook a volt meter to the pump (at the pump), and make sure it's at about battery voltage.

If you double the HP, you should be running an injector double the size of the stockers. Why people try making a zillion HP with the stock injectors is beyond me. GM spent a couple bucks figuring out what injectors an engine needed.....

In my lil v6, I'm running 60 PPH injectors, and two Walbro 340 pumps (staged), with *nice* wiring to the pumps to insure proper fueling.

Look at a data log, what's your max Gm/Sec?. If pegged how close to max HP is it, lots of folks have run well, with pegged mafs, but it's a learning curve. *well* meaning in the 9s.

 

I am running 26lb injectors But with the ecu chip burned to run 26's I am sure they really don't do anything more than the 19's did with the stock ECU settings. I know about fueling and injector sizing I have a heavy turbo 4cylinder background. I am not trying to make a gazillion HP with no fUELING TO GO WITH. Since the Stock motor was a 200-230HP rated motor, and 300HP is probably more along what I will see. Or at least shooting for, aprox %30 more HP aprox %30 more Injector 19lb = %30 aprox 25lb injector. So I wouldn't think I am far off.
Know the pump is in good order. It was installed new, used for 10K turbo charged miles in the same Car, probably pushing 180whp~ Give or take. The pump had no issues there, I know I am consuming more fuel But I would think Walbro High Pressure 255lph could handle 300hp with ease? I don't think the voltage should be off? I will check, but when I did the turbo install and the pump, I also put a larger wire to the Pump and a relay to make sure the Voltage stayed up. When you are running 100+psi you don't want the pump having voltage related drops and frying a motor cause of something easily corrected. PLease remember this is a Miata not a Camaro, but should have absolutely no impact on my issues? Unless 5/16" fuel feed line would be enough to cause a restriction at high flow rates, but I don't think that would be too much of a problem at the goals I am looking at. I have not the ability to Datalog yet I am waiting on my Moates hardware and the lending of a laptop. Might get to that this weekend, I was more looking for mechanical gremlins that I should check before datalogging that I might be overlooking. I have a custom rail with adjustable FPR I can set my fuel pressures up or down from stock too so I have a bit of flexibility.
I guess Iam really looking for info on why it would crap out on power and starve for fuel so bad under heavy acceleration, If thats normal with a stock ECU and cams etc then good deal I know whats wrong. If someone in the know says hey no way should that happen even with all that, Then I will look to other avenues to find my issues. I am new to tuning GM's Kinda have an idea but am really tryiing to gain all the knowledge I can about the tuning process. I have read about the BLM watching in the datalogs to see where you are at, but does it not go off of the O2 sensor? Is that not an inaccurate way to tune when under heavy throttle? Is everyone using a wide band, or am I overlooking something with the whole BLM's thing? Just looking for good solid info. I think it is a case of the ECU stock base fuel Maps just being horribly far off from what the car is actually flowing.But I am not an expert nor do I have the experience to say yes that is the case, or no there is something else at work here......
I do appreciate anyones input on the sbject.
Stephen

 

After spending hours hours and more hours reading on what it takes to tune these, I understand what you are talking about now Grumpy(mostly from your "final answer" comments pages). I was trying low buck tuning but now understand that it just ain't gonna work. (Low Buck that is) I invested in the hardware to datalog and am looking at getting a budget laptop this weekend. I will be investing in a WB O2 in a week or two.

But a bump I put here, should a Walbro 255lph through 5/16" line be enough to support 300-350HP ? Not that I think I will make that much but just wondering, I can make new fuel lines but it will be a PITA. I am more wondering what most guys think is "enough" when it comes to supplying fuel. So many make it a big deal to go to 3/8" feed and others say it is overkill?
I guess I need to make a run with an extension line and a pressure gauge and check?
Any good links to good MAF tuning tips/hints for AE and PE for a true beginner in the EFI tuning realm can't learn from. I get what all the tables are and do for the most part. I get what each function does, but Am still slightly confused on where the magic lies in tuning for heavier breathing cars.
From what I gather without datalogs, a wideband O2 and tons and tons of time I may be defecating in the wind, uphill, without a raincoat?
So anyone who wants to point me towards really good MAF $6E stuff would be greatly appreciated. I don't mind tinkering for months/years on this project but need to get it running well enough to get it registered and through AZ emissions as soon as I can.

 

Can't help you with the MAF stuff, but I believe the 5/16th fuel line is a bit small. If I remember correctly, my stock dual cat 305 TPI set up used a 3/8ths feed line and a 5/16ths return line and it was only rated around 235 HP stock. The pump you have sounds plenty big enough. Tape a fuel pressure guage to the windshield and go for a little drive. See if the fuel pressure drops at the higher loading. If it does, and you know the fuel filter is good (as well as the pump - they do get old and "tired" just like the rest of us LOL), then it almost has to be the fuel line size. Sure there aren't any kinks in the fuel line somewhere?

 

Not abnormal to see a lean spike when you slam the throttle. The point is how quickly does the fueling recover and get you to your desired AFR.

 

Running LS1 26lb injectors. Figured they could feed an LS1 they could feed my car. But Maybe they are too small> I will really start finding out soon with the datalogging etc..
I don't have any "kinks" but there are a lot more bends, I had to re route a lot on this car. I will do the windshield trick, that should tell me a lot. I have all the stuff for that anyway from the Turbo days on the car.
I will post the results I have just been at work so much lately getting time to mess with this has been limited.
Domonic
When I slam the throttle it doesn't lean spike it lean craps out. It stays off the board lean and is just starving for fuel and thus making no power at all.
New filter, 12ga short run wire directly to the batt(batt in the trunk like 2ft from the pump) and a nice relay setup so the pump sees plenty of voltage. It is about two yr old pump with about 10k miles on it, should be fine.
Again I will post the results of teh test drive hopefully tomorrow I will get time, with the fp gauge on the window to see if it is a fuel delivery issue? If it is then my answers are easy and not that big of a deal.
Thank you all for your input.,

 

Also one ??
Since the LS1 Injectors are in a returnless system that runs like 55psi or higher are the 26lb ratings actually false and more like 24lb when in our lower pressure systems? I mean I can jack up my fuel pressure anyways but was just wondering. An injector cleaning flow testing shop told me that they were rated at what they ran in the car making them actually less in most others with lower pressure. I was trying to get a set of injectors flow tested from a motorcycle that I am turbo'ing and had the LS1's in the picture for reference to show him. ???????

 

Yes, the LS1's injectors are rated at 4 bar (58 psi) so running 26 lb. LS1 injectors at 3 bar (43.5 psi) makes them 22 lb. injectors. This will definetly cause a lean problem if the ECM thinks it has 26 lb. injectors when they are actually only at 22 lb. HTH

 

Ahh thank you one issue solved.
Anyone have suggestions as to what injector size I should be running?
I mean waht kind of HP are people really making with a Hotcam, ported heads, bigger valves etc, on a stock lower end?

 

26's would be about right. But you could get away with 22's. An AFPR can get some of that flow rate back. Are you using a stock TPI?

Did you set the injector constant to 22, and did it fix the problem? If not, I'd say your MAF is faulty, but for your sake, I hope the injector constant is the big problem.

With $6E MAF, there's pretty much just the MAF tables and scalars, and the ever important injector constants, but with a stock MAF, the tables and MAF scalars shouldn't need much change, just the inj consts.

 

I Will test drive tomorrow after changing the constants. I have ported the Tpi plenum and runners slightly and have a brand new MAF sensor. I have a feeling it is the constants too. They are 26 Lb LS1 injectors and teh constants are set to 26 so I know that is a big part of my problem.
Picking up a laptop this weekend and will start datalogging with the new constants. I will post the results. The fuel rail is all modded too and I have almost infinite AFPR. So I have a lot of room to work. I could even jack the FP up and let it say they are 26's to test it out.
58psi is the stock LS1 pressure?

 

Don't know if anyone was still following, but I finally got my datalogging setup working, having issues getting tunerpro to datalog but winaldl works great, will fix that when I have time. But I changed the constants for the injectors down to 21lb/hr to be on the safe side. Datalogged a short drive and all my BLM's are still in the 158+ range, however the car runs really well compared to before, now is just a matter of time and patience.
What is the best driving method if on a short (2mile) deserted road for trying to get as much datalog info as possible? Great info, seemed a little short on BLM and other info at other than very low load conditions.