Edelbrock MPFI guys, question for ya...

[94Blazer383]

I took the Edelbrock MPFI off my boat last week because I may be selling it. I put the stock carb back on and also pulled out the LT4 cam, I put a stock Vortec truck roller cam in. It was a freebie.

Anyway, my Edelbrock setup has and adjustable regulator and the BB TBI. I was thinking about sticking it back on my truck. I know a lot more about tuning now then I did when I originally built the truck so I am not worried about getting it to run. The ECM and Memcal that I had in the boat are setup to run true MPI.

Will the small injectors with a little more fuel pressure run my 383? I have heard bad things about the Picco injectors on Edel. setups.

[Blue71]

On my setup I push 62# of fuel pressure at WOT on the
19# injectors and have not had a problem getting fuel.
Air yes, fuel No

You might what to port the manifold a little, to help get more
air flow.

Because you know a 383 will suck more air.

[93ChevyTBI]

Originally Posted by 94Blazer383

I took the Edelbrock MPFI off my boat last week because I may be selling it. I put the stock carb back on and also pulled out the LT4 cam, I put a stock Vortec truck roller cam in. It was a freebie.

Anyway, my Edelbrock setup has and adjustable regulator and the BB TBI. I was thinking about sticking it back on my truck. I know a lot more about tuning now then I did when I originally built the truck so I am not worried about getting it to run. The ECM and Memcal that I had in the boat are setup to run true MPI.

Will the small injectors with a little more fuel pressure run my 383? I have heard bad things about the Picco injectors on Edel. setups.

I saw this coming as soon as he said he was pulling it off the boat.............

[94Blazer383]

Originally Posted by Blue71

On my setup I push 62# of fuel pressure at WOT on the
19# injectors and have not had a problem getting fuel.
Air yes, fuel No

You might what to port the manifold a little, to help get more
air flow.

Because you know a 383 will suck more air.

I may give it shot. So I am guessing you have a vacuum line ran to your regulator to lower the pressure at idle?

I ported it out before I put it on the boat, should be good to go.

[Red94Chev]

I dunno, I'm a little more skeptical. I switched to 29# injectors when my datalog showed I needed more fuel at high RPM at WOT with a commanded 12.6:1 AFR. I was running 65 psi at the time. I'm running a 350 with WOT shifts at 5600 RPM. VE tables were maxed out. O2 sensor mV just flopped low after 4000-4500 RPM and the engine felt like it hit a brickwall. Lean like that is a disaster waiting to happen.

Surprisingly enough, changing displacement from 350 to 383 cid does not affect fuel injector selection. Selection is largerly based on hp output of the engine. If your engine output is no more than 330-360 hp (19#/hr injectors at 65 psi, 0.45-0.5 BSCF, 90% duty cycle), I think you will be fine. If you're over that, then time to pony up for larger injectors. Desktop dyno predicted between 380-390 hp for my motor, and it looks like that's where it's heading.

http://www.holley.com/data/TechServi...20Injector.pdf

[94Blazer383]

Originally Posted by Red94Chev

I dunno, I'm a little more skeptical. I switched to 29# injectors when my datalog showed I needed more fuel at high RPM at WOT with a commanded 12.6:1 AFR. I was running 65 psi at the time. I'm running a 350 with WOT shifts at 5600 RPM. VE tables were maxed out. O2 sensor mV just flopped low after 4000-4500 RPM and the engine felt like it hit a brickwall. Lean like that is a disaster waiting to happen.

Surprisingly enough, change in displacement from 350 to 383 cid does not affect fuel injector selection. Selection is largerly based on hp output of the engine. If your engine output is no more than 330-360 hp (19#/hr injectors at 65 psi, 0.45-0.5 BSCF, 90% duty cycle), I think you will be fine. If you're over that, then time to pony up for larger injectors. Desktop dyno predicted between 380-390 hp for my motor, and it looks like that's where it's heading.

http://www.holley.com/data/TechServi...20Injector.pdf

Well, I am starting to lean towards economy...I figure the multi port should atomize the fuel a little better. I might lower my shifting RPM if it looks like it is going to lean. Right now I am shifting at 5500 Rpm. I will take it down to 5000 if I have to.

[94Blazer383]

What fuel pump are you guys using? I still have the same one in my truck that came with the Edelbrock kit. Will it work? at 65 lbs?

[Red94Chev]

Installing larger injectors won't affect your fuel economy as long as you change the fuel injector flow rate to match. The computer just changes the injector pulse width to maintain commanded 14.7:1 AFR in closed loop. So for larger injectors, the injector pulse width is shortened (relative to smaller injectors) and the same amount of fuel is delivered. You can improve your fuel economy more by enabling "lean cruise" as well and running higher AFRs at cruise. Lean cruise is also independent of injector size for the reasons above. The '7427 has this capability, but it was never enabled from the factory when EPA got wind of it. Changing the AFRs to values other than 14.7:1 also changes emissions as well. Leaner mixture produces more hydrocarbons and a slight rise in NOx emissions. NOx eventually falls off as AFR leans out even more, while HCs continue to rise. 14.7:1 AFR was chosen for that reason, a balance of fuel economy, power, and the low emissions.

There is a theorectical limit, of course, but this mainly affects idle since this is where your engine has its lowest air requirements and therefore the shortest PCM-commanded injector pulsewidth. My BLMs at idle are 127-130 (with re-calibration of VE tables) with the larger 29#/hr injectors installed, so it won't be a problem.

[Red94Chev]

Originally Posted by 94Blazer383

What fuel pump are you guys using? I still have the same one in my truck that came with the Edelbrock kit. Will it work? at 65 lbs?

Yes, I'm using the one from Edelbrock. No issues at 65 psi. Maximum pressure good up to 100 psi according the Summit: http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D3581&N=700+ 400065+115&autoview=sku. 65 psi is probably max pressure I'd run to the injectors. No reason why, just common sense I guess. The injectors were designed for 45 psi. I really don't have a good sense how higher psi changes the injector properties, but there probably are some differences.

[1Bad454]

What are you guys tuning with? I'm going to upgrade my injectors to 44#.

[Blue71]

94Blazer383, Yes I have the vacumm line ran to the regulator
to control the fueling at idle.

from where it was stock(45#s) HaulnA$$ had me set it to 60#,
made a big difference. He also told me that the 29# injector
would be to big for my engine, a 383 I don't know about.

When I had it on the Dyno I was running out of fuel, could not
get below 13.5 AFR at WOT, VE tables were maxed out, bumped it
to 62# gave me a little more room to play with, 12.1/12.5 with
no problem.

I can tell you the pump that comes with the kit will push 80#
or a least mine will.

Red94chev, what kind of map you pulling at 5600, 100% ?

1Bad454, TunerProRT and the Ostrich here.

[94Blazer383]

Originally Posted by Blue71

94Blazer383, Yes I have the vacumm line ran to the regulator
to control the fueling at idle.

from where it was stock(45#s) HaulnA$$ had me set it to 60#,
made a big difference. He also told me that the 29# injector
would be to big for my engine, a 383 I don't know about.

When I had it on the Dyno I was running out of fuel, could not
get below 13.5 AFR at WOT, VE tables were maxed out, bumped it
to 62# gave me a little more room to play with, 12.1/12.5 with
no problem.

I can tell you the pump that comes with the kit will push 80#
or a least mine will.

Red94chev, what kind of map you pulling at 5600, 100% ?

1Bad454, TunerProRT and the Ostrich here.

Cool, thanks. I have a mallory regulator with a vacum port, so I will try that.


I am using TunerPro RT, Autoprom, and Inovate LM1.

[Red94Chev]

Originally Posted by Blue71

Red94chev, what kind of map you pulling at 5600, 100% ?

MAP at 100%TPS is the same as atmosphere (1 atm = 101.325 kPa at sea level). Because I live 2192 ft above sea level, the highest MAP pressures in kPa I can achieve at WOT (100%TPS) is about 93 kPa. There are a few other factors that contribute like air temp, humidity, and dew point, but these only have a minor effect. My last datalog showed 91.2 kPa at 5600 RPM. The highest MAP during the WOT run was 92.2 kPa.

I have TunerProRT, AutoProm, and an Innovate LC1. I prefer to burn PROMs, so I can analyze the data after driving (mostly to and from work to multi-task and save some gas money while tuning). $0D and '7427 PCM was modded for PFI by HaulnA$$. HaulnA$$ is a true genius; I've learned more from him than anyone else. His posts are gold! Fast305 as well.

BTW, Happy Canada Day!! Same goes for you US guys on the 4th.

[Red94Chev]

Originally Posted by 1Bad454

What are you guys tuning with? I'm going to upgrade my injectors to 44#.

90SS, right? Seen your posts on the 454SS forum. Are you running a Procharger as well? Very nice 454SS. I've been following that TrucksTV build on Spike:
http://www.fullsizechevy.com/forums/...-truckstv.html. According to Edelbrock, their 29#/hr injectors support up to 450hp with the BB chevy and 625 hp for the 44#/hr injectors. As you know, these injectors are also used in their Pro-Flo setups for the big block Chevy. Or now called "Pro-Flo2" since they have a new flash-programable ECU that come with these systems. You now have the option of hooking up a wideband O2 sensor to replace the narrowband for closed loop operation. This is now a great upgrade for these trucks, similar to the Holley systems. You're right on the money using 44#/hr injectors. How are you handling boost pressures with the ECM? 2-bar MAP sensor and aftermarket ECM? Or using Procharger's calibration for the stock ECM?

Too bad Ryan from TrucksTV didn't have the Pro-Flo2 ECU. With a wideband O2 sensor hooked up, he would dial-in that truck so fast it would make your head spin. Especially at WOT, which is where the head-to-head showdown for these trucks in Aug is going to come down to "who tuned their truck the best?". They both have the right parts...except the chevy's running the crappy y-pipe and factory stall converter with that high-duration cam. I don't think he'll hit 450 hp on the dyno, mainly due to the exhaust and whoever is doing the tune with Edelbrock's crappy handheld calibration module.

[gmc406]

Originally Posted by Red94Chev

If your engine output is no more than 330-360 hp (19#/hr injectors at 65 psi, 0.45-0.5 BSCF, 90% duty cycle), I think you will be fine. If you're over that, then time to pony up for larger injectors.

I'm confused. Those injectors will support more than that. My 406 has the MPFI setup on it as well. No lean issues.....yet. I'm still running the recommended fuel pressure. I'm in the 12's, though it's never been dynoed, I'm sure the output is more than 330-360hp. I'm shifting at 6000 and it pulls hard all the way. I giggle when guys that hit 14's figgure they need larger injectors.

Maybe I'm wrong.

[Red94Chev]

Injector sizing and the math involved is well known in the industry. Could be the fact that Edelbrock uses the TBI-fuel injection strategy (injectors fire 4 times for one combustion cycle) compared to bank injection (injectors fire twice/combustion cycle). Usually creates a rich idle problem, but it may provide some "extra" fuel. Generally the calculated inj pulsewidth is just divided the number of injection events, so I would think that this would cancel each other out. I was concerned about the injectors with my motor and called Edelbrock. The tech told me the injectors are rated a little higher at 20.5#/hr, not 19. The story seems legit since Edelbrock's own testing published in Offroad magazine a number of years ago listed 20.5#/hr as the injector rating in the article: http://www.off-roadweb.com/tech/0310...tem/index.html. This doesn't explain supporting 330+hp at the recommended fuel pressure. 328hp would be max at 100% DC. This is flywheel hp, not rear wheel hp.

My only other thought is if your engine's BSCF rating is less than the standard 0.5. At 0.45, for example, 19#/hr injectors will support 337hp at 100% DC, At 0.4, 380 hp. These ratings are specific to each engine. Since it sounds like your 406 is heavily modified, you may have a lower BSCF rating. See the chart in this link: http://www.holley.com/data/TechServi...20Injector.pdf. <---- Read this, it will explain everything related to injector size selection in one page.

Who built and tuned that motor? 12's? Seriously?! Maybe with nitrous or supercharger, a beefier tranny, and the stickiest tires known to man. A 12.99 sec 1/4 run means a trap speed of 103+ MPH and a 0-60 time under 4.5 sec. High 13's I could believe, but 12's? Something doesn't add up here.

[Fast305]

Originally Posted by Red94Chev

You can improve your fuel economy more by enabling "lean cruise" as well and running higher AFRs at cruise. Lean cruise is also independent of injector size for the reasons above. The '7427 has this capability, but it was never enabled from the factory when EPA got wind of it. Changing the AFRs to values other than 14.7:1 also changes emissions as well. Leaner mixture produces more hydrocarbons and a slight rise in NOx emissions. NOx eventually falls off as AFR leans out even more, while HCs continue to rise. 14.7:1 AFR was chosen for that reason, a balance of fuel economy, power, and the low emissions.

As far as the 7427 not having lean cruise enabled from the factory, you are correct in regards to trucks. I have not seen a factory truck calibration with it enabled. However, I have seen 3 different van calibrations with it enabled. Here is the catch there though, most of the cells in the lookup table are programmed to command a 14.7:1 a/f ratio with a fully warmed up engine, save for heavy throttle acceleration and coasting/overun.

[1Bad454]

Originally Posted by Red94Chev

90SS, right? Seen your posts on the 454SS forum. Are you running a Procharger as well? Very nice 454SS. I've been following that TrucksTV build on Spike:

Yup it's a 90 with a Procharger and thanks for the compliments. I was running the stock ECM, stock Edel tune and an FMU. My engine is out right now. I'm having a roller cam put in, getting my intake extude honed and having my Edel heads ported. Edelbrock actually told me that their 44# injectors are rated up to 704HP and that is where my final goal is. As far my ECM and MAP sensor are concerned I am still considering options. I may end up going this route for the ECM though; www.dynamicefi.com

I am a little worried about the "Trucks" shootout. Low compression (under 10:1) and a single exhaust are going to make it a real challenge. I practically begged Ryan to put cut outs on the exhaust.

[Red94Chev]

Originally Posted by Fast305

As far as the 7427 not having lean cruise enabled from the factory, you are correct in regards to trucks. I have not seen a factory truck calibration with it enabled. However, I have seen 3 different van calibrations with it enabled. Here is the catch there though, most of the cells in the lookup table are programmed to command a 14.7:1 a/f ratio with a fully warmed up engine, save for heavy throttle acceleration and coasting/overun.

That's interesting. Edelbrock went one step further since my chip calibration (#3501) also had it enabled. This means that the fuel economy improvement that has been quoted by them in the past is largely due to "lean cruise". AFR reaches 16.0 in the highest vac areas of the table. Pulled the calibration right off the chip with the Autoprom using the Burn1 utility.

[Red94Chev]

Originally Posted by 1Bad454

Yup it's a 90 with a Procharger and thanks for the compliments. I was running the stock ECM, stock Edel tune and an FMU. My engine is out right now. I'm having a roller cam put in, getting my intake extude honed and having my Edel heads ported. Edelbrock actually told me that their 44# injectors are rated up to 704HP and that is where my final goal is. As far my ECM and MAP sensor are concerned I am still considering options. I may end up going this route for the ECM though; www.dynamicefi.com

I am a little worried about the