Air Fuel ratio
 

1997 502 Mag with a M3sc Procharger running 7 lbs. boost.

At 5000 rpms and 7 lbs. of boost I have an AFR of 13.0. I think I am a little lean. What does everyone think?

I also believe i am maxed out on my 42lb. stock injectors?

At 5lbs. Boost I have an AFR of 11.5 which I believe is safe.

42lb not going to cut it...we run a 509, procharger, our own custom EFI and we run 90lb injectors...yes lean

13 is way too lean on a boosted boat. I run 11.5- 11.9 at 8 lbs. I would not be comfortable with anything over 12 cause I like to get on it and not worry.

Who did the tune? Good chance you are out of injector like stated above. Boost referenced regulator? Fuel pressure gauge on the dash?

I know its not a whipple, but Dustin at whipple has but together some great tunes for guys using prochargers. If your ECM is stock, and you are using the pro charger "cheat" method I would suggest letting someone get in there and tune the BPW to boost table, at the very least

I took ECM to Tyler Crockett last week and he added more fuel in the upper RPM ranges. (Runs perfect until I get above 5 lbs. of boost). I have a feeling that I am out of injector now.

I am using Bell Cartech Boost referenced regulator with Autometer fuel pressure in dash. I also have the MEFI1 computer.

Running 80lbs. Fuel pressure at WOT

Not sure if I can upgrade my injectors on the 1997 502 Mag MPI Fuel rail but if I can find some that will be my next step. Till then Ill keep her at 5lbs. Boost and under

Why not go back to Crockett and ask his opinion? The guy knows his stuff.

How much boost can those old MEFI units read? Any chance that anything about 5 psi is out of range of the MAP sensor?

80lbs is off the charts!

Yes I am definitely going to talk to Crockett. He has been a great help.

I dont believe the MEFI1 can read Boost at all.

Well....that can be a problem :D It can read zero vacuum however, you can program a dump there but then you have problems. If you get it under 12 at WOT 7lbs it will be crazy rich at 1-4 lbs, no way to program a curve.

Have you asked him if he has a mefi3 laying around to program and switch out? This will give him a boost table to write to.

Junk the mefi1 and the boost-referenced regulator. Crate Engine Depot has a brand new mefi4a with harness for just over $600. You can probably bring the fuel pressure down to 50lbs or so and raise bpw enough to get the afr you want without killing the injectors. I did this on my old 502mpi and never got over 60% on the duty cycle at 6lbs of boost.

Yea man that baby is lean!!!!! Give her some fuel asap!!!!! I would not run until I did....

Several points which echo previous comments.

42 lb injector is not enough. I run 42 lb on a N/A small block.

MEFI 1 is ok for NO BOOST applications. It is simplistic and lacks fidelity but is robust and works. I would follow Griswalds advice RE the MEFI 4.

In my opinion, 13.0 at 5000 rpm and boost is too lean. For reference I'm 12.5-12.8 WOT naturally aspirated (5000-5600 rpm).

You can get bigger injectors to fit the MP/EFI. RC injection is one vendor. I'm sure others will chime in for other sources.

Best of luck.

Talked to Crockett today. "He said stop by tomorrow and I can help you out" Sweet!!

without starting a war here...but this is the issue with the merc MEFI systems and not being able to tune on the fly in the boat for the most of the guys...not to many setups/elevations/etc are the same so sending the ECM out getting a tune done and trying, then repeating is a pain. your 80psi fuel pressure is just a big bandaid that procharger tried to no tune was required..again banaid....you need to change injectors/rails, possibly fuel system(not sure what you have done) then work on tune to get it right...my .02 Rob

Mefi 4s can tune on the fly with Tuner Pro emulator and/or Mefi Burn.

So does that mean you can make changes to all of the maps real time while someone is driving the boat ?

Yes, you can tune real time on the fly. I'll drive the boat with the laptop on my lap and tune it while I drive.

As mentioned, you are out of injector. Being a 97, you have Keihin injectors. There are no drop in replacements. However, we have redrilled the intake and fuel rails to accept long Mototron injectors. You can then go to 65 lb injectors (high impedance) that will support all you want to do. You will also need to make some mods to the rail so that I can be fed from both ends. The main fuel passage way in that rail isn't that large, not to mention you can't feed it with large lines or fittings. That is why we feed it from both ends.

80 psi is really hard on the injectors. The pintle has to close against that pressure and it really takes it's toll on them over time. Go to a Mefi 4B so that it can be tuned properly with a more manageable fuel pressure. Not only are you out of injector, but at 80 psi, you are probably at the upper end of what the pump can do. As pressure increases, the volume that the pump moves decreases.

We have done a ton of them. Let me know if we can help in any way.
Eddie

I understand that, what I was trying to get across was the fact of sending the ECM out to someone to tune off the boat and hope for the best when you put it back on...

Eddie, R/C injection in Torrance has drop in replacements for Keihin injectors in many sizes. I replaced my Keihin with RC units.

Good to know Trash. Thank you!

Tyler Crockett has helped me optimize my current set-up and I am going to run it for the rest of the summer. Running Great!!

I am going to research my options over the Michigan off-season, Which lasts about 9 months, and decide which direction I want to go for future upgrades.

Thank you everyone for the advice, comments, and input! What a Fabulous wealth of knowledge and guys willing to share it available on OSO !

The largest replacements I have seen is 50 lb/hr. We actually flowed some at the shop and they flowed the same as the stock 42's.
Eddie

I personally took my Merc manifold, TB , and fuel rails to their shop in Torrance and we grabbed injectors off the rack and hand installed them on site. Ran stock injectors through the flow bench and their injectors for a back to back A/ B comparison. Checked flow rates and spray patterns. They have stuff that flows way more than 42 lbs/hr. I am not affiliated nor endorsing but simply stating first hand,. onsite, touch the **** myself information. Use it as you see fit.

I've been running these injectors, my motor, self tuned, for over 3 years now (180 hrs run time). No complaints. Offering this merely as a data point for those in need.

+1 Its all about duty cycle and you are way beyond it with a stock injector at 80PSI.


You havent mentioned your test method. What type of O2 system are you using? Werent you going to fabricate something that is inserted thru the rear? I am curious of test results, repeatability and accuracy. Tell us more about test equipment and test procedure so we are sure you arent swaying the data.

Yes i was working on a sniffer pipe set-up made out of copper tubing. I was making some progress with it when I came across a guy selling a used Port side Lightning header very cheap.

I have Lightnings on my boat but did not want to cut and weld on them. ( They have the mild steel outer pipes with a ceramic coating ). So I welded a bung into the used header and hooked up an AEM Wideband Air/Fuel UEGO gauge.

I seem to get an accurate reading with this method.

I am still learning alot about Fuel Injection and plan on researching a whole system approach that will work together that I can possibly self-tune. If it is even feasible for a novice like me to self-tune? This would be something I will install during the off-season.

Well, I stand corrected. I haven't looked for replacements in a while since we have been replacing them. Thanks for the info, That's good to know.
Eddie

Absolutely, theres a couple FAST systems on the market that you could install the ECM and wiring harness on your engine, answer some questions on the hand held tablet that comes with their EFI system, start it up and let it tune itself.

I have never used that system personally but it cant be that much different than tuning MegaSquirt EFI. You could go MegaSquirt as well, only thing there is that you would need to make your own wiring harness.

You would hook your current O2 sensor (as long as they support the AEM, which I believe most do) to the ECM so it reads the air/fuel ratio and basically go drive the boat (or have someone do it for you). After a couple hours of that the tune would be close enough to run on, and then you can use your laptop and make fine tune adjustments where necessary.

Having EFI will really shine where you can get it to idle at say 12.5:1 AFR, cruise at 3500 at 13.0:1 for fuel economy, and then whatever ratio you want while its under boost.

The FAST system sounds very interesting. I would think installing larger injectors without any machining work necessary, then hooking up the FAST system could be a good direction for me to go in.

No worries. I had a tough time doing the Keihin injector research when I did my rebuild since I wanted minimal changes to the EFI rails etc. When I found this place I was elated. No drilling or modding at all. They don't do much marine work but were more than accommodating to my situation. Again, I'm not affiliated nor endorsing them as the be all - end all EFI source but they did provide a solution to my problem.

Do you know what size injectors they offer? I am very interested in replacing my injectors and going wirh a self learning EFI controller.

I am currently running a Procharger at 7 lbs. on a stock 502 mpi with Keihin injectors. Hoping they have something that will work for my application.

They offer quite a few different size (flow rate) injectors and injector dimension. I don't remember off hand what the biggest injector was but they have a web site that shows most of their products. I know some of the injectors will not work due to body size and/or they were low impedance peak & hold style, but they had quite a few that fit the stock application.

This is their web site : http://www.rceng.com/index.aspx

I don't know what HP you are at, but for 800 hp with a BSFC of .55, 43.5 psi fuel pressure you'd need a 69 lb injector assuming an 80% duty cycle. If you are making less HP that size injector gives you a little headroom. You could also bump the fuel pressure a little (50 psi) for some additional flow but I am not a fan of bumping fuel pressure above 43 psi. RC has a 71 lb injector with Denso and Honda style tops and one other. Those might fit the bill.

I hope this helps.

Thank you !!

also keep in mind, the rails, lines, fittings everything are not good on the factory stuff..

I just couldn't wait till the off season to redo my efi system. I ordered the new Holley HP efi controller from Haxby. It is a self learning unit. Then I went ahead and ordered the 71 lb. Injectors from RC injection in California. I have already upgraded fuel lines, filter head, etc.
I think I should have a nice piece once I install these last few things.

Keep your eyes open for a couple of Boost referenced regulators soon to be listed in the Swap Shop!

Thanks for everyones help on this !!!!!

Give us feed back on how things went. I earnestly hope we steered you in the right direction.

Injectors arrived today. Looks like they should drop in no problem. I may have to do some minor Die grinding on #1 and #8 on the intake manifold because of the Injectors slightly larger diameter.
I really like the way Eddie Young mounts the electronics on a carbon fiber plate on the back of the motor. I wanted to do something like that with my Holley HP,but I am very limited on space back there so I am going to mount mine on the Port header where the stock ECU was mounted. I do not have any real carbon fiber on hand but do have plenty of 3/16 aluminum plate and carbon fiber replica "formica" so I am going to fab up a fake carbon fiber mount.
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Fuel pressure regulator mounted on its own "carbon fiber" plate.
I have been having great luck with this old Lightning header that I welded a bung into.
Also RC Injection flowed the injectors before shipping and included print out. I should be back on the water soon as my Holley HP system arrives.

Holley HP arrived today. Time to get to work and get this thing back on the water.

interested to see how user friendly that setup actually is..good luck Rob

Cool deal Hadley, good luck and im looking forward to hearing what the Holley efi is like.

Thanks guys, Installed new injectors tonite and removed old wiring harness. Holley system looks pretty nice so far. Just started a bit of wiring.

Took the boat out yesterday for the first run with the Holley HP system and larger 71 lb. injectors. Runs awesome!!
Datalogged the run and my A/F was spot on throughout the entire RPM range. Alex Haxby emailed me a base tune that worked awesome.
Install and set-up was very easy even for a Fuel Injection amateur like myself.
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Awesome to hear, your carbon panel looks killer !