Changed 383 TBI to BBC Injectors - Looking for direction...

[Chewy1576]

I went for a long drive yesterday and logged a bunch of data running with cleaned up 5.7L injectors (55 #/hr). I know it was running lean and I hoped a new EP381 fuel pump would help with that. After getting back home and looking over the log, it's still running lean. Today I changed the injectors out for a set of the early 7.4L injectors (90 #/hr) just to see what would happen and logged some more data. Not surprisingly, now it is running rich. I have attached the ADX and XDL files to look over.

So here is where I am at - I am working on getting the equipment to start doing my own tuning. I have been in contact with Blueprint Engines to get a copy of the .bin file used to make the chip that came with my engine, but no word if they are going to give it up yet. I'm looking for some guidance on where to start tuning this beast. Once I have the 1228747 ECM modded for the new chip, is it better to begin tuning with the 5.7L injectors and try to add fuel, or leave the 7.4L injectors and try to remove fuel? Or would you start with the stock .bin (Mine was AKWH) and start from scratch? I am using the stock small block TB and it's sensors. I would like to avoid switching to a big block TB to keep from having to remove the intake and have it bored out for the bigger TB.

[Roadknee]

Looking at the datalog with the 5.7 injectors it looks to be lean by about 14%. I think it would run pretty good if you reinstalled the small injectors and increased fuel pressure about 30%. If you're currently running the stock spring fuel pressure regulator spring, try an 18 psi spring.

It's definitely pig rich on the big block injectors. BLM's are buried at 105. Some of the cells are close because the O2 does occasionally cross count.

If you don't plan to rev the 383 above 4,000 rpm I think you can get by with the small injectors with increased fuel pressure. Otherwise use the large injectors and adjust the injector constant in the Bin.

If Blueprint Engines won't cut loose with the Bin, you should be able to read the chip they provided you once you get your chip reading/burning hardware.

[Chewy1576]

Looking at the datalog with the 5.7 injectors it looks to be lean by about 14%. I think it would run pretty good if you reinstalled the small injectors and increased fuel pressure about 30%. If you're currently running the stock spring fuel pressure regulator spring, try an 18 psi spring.

It's definitely pig rich on the big block injectors. BLM's are buried at 105. Some of the cells are close because the O2 does occasionally cross count.

If you don't plan to rev the 383 above 4,000 rpm I think you can get by with the small injectors with increased fuel pressure. Otherwise use the large injectors and adjust the injector constant in the Bin.

If Blueprint Engines won't cut loose with the Bin, you should be able to read the chip they provided you once you get your chip reading/burning hardware.

Hey thanks for looking those logs over. I am already running an 18 lb spring in the FPR. I haven't hooked up a gauge yet, but with a fresh higher output pump, new filter, rebuilt FPR with new spring, and cleaned injectors, I feel like I can safely assume that there is 18 psi. I'm thinking about changing that out to an adjustable one for more control over the fuel pressure though. I'm just worried about maxing out the 5.7L injectors, where the 7.4L injectors will be well under their operating limit, with overhead for later mods. I noticed the BLM value buried at 105, and the INT value not much higher. While generating the datalog with the 7.4L injectors tonight, I burned a 1/8 tank of fuel in a 10 mile commute home from work!

I was doing some long accelerations and I don't think 4K will be seen very much, if at all. The dyno sheet from Blueprint that came with the engine says the torque peaks at 405 lb/ft at under 3000 rpm, so 4000 is really unlikely.

I was thinking the same thing, if they don't give up the bin, I can just read it from the chip in the ECM now and keep it in a box somewhere for warranty reasons if anything happens. The Product Specialist I was talking with created a support record and I am waiting to hear from a Support Specialist about it. Hopefully they hand over the bin file and let me tune it myself instead of trying to do a mail order tune. Just looking for a good starting point as a beginner to tuning from someone with experience. I feel like I could start from a stock AKWH bin and get it running pretty well, but if they have done a lot of the homework already, why "reinvent the wheel"?

[Roadknee]

I didn't realize you were already at 18 psi (should verify with a gauge though). Since you already have the BB injectors, might as well run them. You could try them with the stock spring. I think the tune would still be rich, but the BLMs should move off 105 and it will probably run pretty good.

[brian617]

Used one of those "18psi" springs with the same pump your'e running and all it could muster was 17psi before it coil bound. Never assume, hard to tune with unknowns.

[Chewy1576]

I didn't realize you were already at 18 psi (should verify with a gauge though). Since you already have the BB injectors, might as well run them. You could try them with the stock spring. I think the tune would still be rich, but the BLMs should move off 105 and it will probably run pretty good.

I think my plan of attack will be trying to tune with the 90 lb/hr injectors. I ordered the Burn 2 and hardware to install the chip last night. Should be here sometime next week.

Used one of those "18psi" springs with the same pump your'e running and all it could muster was 17psi before it coil bound. Never assume, hard to tune with unknowns.

To both of your points, I will find a gauge and see what my FP is really at.

[Nasty-Z]

I think my plan of attack will be trying to tune with the 90 lb/hr injectors. I ordered the Burn 2 and hardware to install the chip last night. Should be here sometime next week.



To both of your points, I will find a gauge and see what my FP is really at.

For the record , the factory early BBC injectors are 80#/hr @ 13psi , there was never a 90#/hr BBC TBI injector .

I agree on finding out exactally what the F/P is set at , it will make tuning much easier.

What are the spec's on this engine ? Intake manifold ?

TOM

[Chewy1576]

For the record , the factory early BBC injectors are 80#/hr @ 13psi , there was never a 90#/hr BBC TBI injector .

I agree on finding out exactally what the F/P is set at , it will make tuning much easier.

What are the spec's on this engine ? Intake manifold ?

TOM

Everything I have seen about the P/N 5235231 injectors indicated they flow 90 lb/hr so that's what I was referring to, but I could be wrong. Here are the engine specs directly from Blueprint:

HP & Torque: TBI - 280 HP / 388 FT LBS
Compression Ratio: 9.0:1
Hypereutectic Pistons
Flat Tappet Cam
Cast Steel Crank
Part #: BP38301CT

Block:

4 bolt main block bored .040 over
Square and parallel decked
Align honed main bearing bore
Cylinders honed on computer controlled machine to within .0002 straightness and roundness
Cylinders are sonic tested for thickness

Rotating Assembly:

New cast steel crankshaft
Hypereutetic pistons
GM heavy beam rods with 150,000 psi bolts
Hastings Moly rings
Rotating assembly balanced to within 2 grams
Melling high volume oil pump
Flat tappet hydraulic lifter camshaft
Double roller timing chain

Cylinder Heads:

Modified stock heads for improved flow
Hardened retainers and springs
2.02 swirl polished intake valves
1.60 swirl polished exhaust valves
Hardened push rods
1.5 Long slot rockers
3 angle valve job

Cam Specs:

Cam Type: Flat Tappet
.435 Intake .454 Exhaust
209 Intake / 216 Exhaust duration
@ .050 - 110 degree lobe separation

It came with an Edelbrock Performer TBI intake. Still has the stock exhaust manifolds and Y-pipe, but everything after that is high flow and 3" pipe also.

[tayto]

The 90# BB injector was run @ 30 psi from factory. I wouldn't worry about "maxing out" the TBI injectors running them @ 30 psi is a normal thing in the performance TBI world these days. There is a fella on thirdgen.org that apparently is running his TBI injectors @ 50 psi. Saturn ran TBI injectors @ 30-36 psi IIRC... Once you get over 18 psi you'll want to consider using a VRFPR.

[Nasty-Z]

The 90# BB injector was run @ 30 psi from factory. I wouldn't worry about "maxing out" the TBI injectors running them @ 30 psi is a normal thing in the performance TBI world these days. There is a fella on thirdgen.org that apparently is running his TBI injectors @ 50 psi. Saturn ran TBI injectors @ 30-36 psi IIRC... Once you get over 18 psi you'll want to consider using a VRFPR.

Incorrect ,

The only BBC TBI injector that left the factory at a elevated fuel pressure was the 94-95 BBC TBI systems , they were actually around a 45#/hr injector @ the standard 13 psi (These were stamped 17104288) , The 94-95 BBC TBI systems used these injectors at a raised fuel pressure (28-32PSI) to thwart off vapor lock on the hot running 454's of the era. The end result of running this smaller injector at an elevated fuel pressure was around 67-72 #/hr .

The 5235231 BBC TBI injector that is the base injector platform that most , including myself , use in high flow demands is rated 80#/hr @ 13 PSI . There was never and will never be a 90#/hr BBC TBI injector to leave GM . That is directly from inside information at the time of production from GM , not information on the internet.


I do however agree on the AVRFPR , it is a productive tuning tool for the TBI system when you need to bleed off some fuel pressure at idle but still maintain fuel at WOT.I as well as others have ran the 5235231 platform injector at upwards of 70+ psi with no adverse effects. Be wary at this pressure or around , better have a capable pump .........


This is Aeromotive 13107 AVRFPR mounted along side of a BBC TBI unit on a 496 BBC ,this particular setup was a 2.2" TBI unit (56mm) , modified Performer intake with a lot of epoxy in the plenum and runners and running around 52 PSI @ WOT :

Attachment 8622

Attachment 8623

TOM

[Chewy1576]

I guess when I say "max out the injectors", I mean I don't want to push an injector to 100+% duty cycle to get the engine to run efficiently. I would rather use a higher flowing injector at say 50% duty cycle to allow the ECM to maximize the power the engine can produce and run as efficiently as possible.

[Fast355]

Incorrect ,

The only BBC TBI injector that left the factory at a elevated fuel pressure was the 94-95 BBC TBI systems , they were actually around a 45#/hr injector @ the standard 13 psi (These were stamped 17104288) , The 94-95 BBC TBI systems used these injectors at a raised fuel pressure (28-32PSI) to thwart off vapor lock on the hot running 454's of the era. The end result of running this smaller injector at an elevated fuel pressure was around 67-72 #/hr .

The 5235231 BBC TBI injector that is the base injector platform that most , including myself , use in high flow demands is rated 80#/hr @ 13 PSI . There was never and will never be a 90#/hr BBC TBI injector to leave GM . That is directly from inside information at the time of production from GM , not information on the internet.


I do however agree on the AVRFPR , it is a productive tuning tool for the TBI system when you need to bleed off some fuel pressure at idle but still maintain fuel at WOT.I as well as others have ran the 5235231 platform injector at upwards of 70+ psi with no adverse effects. Be wary at this pressure or around , better have a capable pump .........


This is Aeromotive 13107 AVRFPR mounted along side of a BBC TBI unit on a 496 BBC ,this particular setup was a 2.2" TBI unit (56mm) , modified Performer intake with a lot of epoxy in the plenum and runners and running around 52 PSI @ WOT :

Attachment 8622

Attachment 8623

TOM

You would be correct except some of the later TBI small block G/P-vans ran higher fuel pressure. Some of the 2 ton trucks also ran higher fuel pressure on the 366/427 big blocks. Also the Marine TBI units ran 28-32 psi in almost all applications as well. The 2" marine small block throttle body I have came off an aluminum L98 head 350 making 320 HP. It had the 46# high pressure injectors in it. My big block 2" marine TBI came off a 405 HP 496/502 and had the 28-32 psi regulator on it and high pressure 61# injectors.

[Fast355]

I guess when I say "max out the injectors", I mean I don't want to push an injector to 100+% duty cycle to get the engine to run efficiently. I would rather use a higher flowing injector at say 50% duty cycle to allow the ECM to maximize the power the engine can produce and run as efficiently as possible.

Actually you really wouldn't want it to run like that. When you have massive injectors its hard to control the fuel delivery accurately. You really should supply the engine with just enough fuel to keep you under 85% duty cycle at your WOT shift points.

[Nasty-Z]

Touché'

some of the later TBI small block G/P-vans ran higher fuel pressure.

Not a BBC , so not applicable here anyway.

Some of the 2 ton trucks also ran higher fuel pressure on the 366/427 big blocks.

The medium duty injectors will not interchange with the normal TBI unit the OP is using . These units were the smaller side feed injectors and most of these TBI units had provisions for PTO hold cables or governors . Not a good comparison.

The 2" marine small block throttle body I have came off an aluminum L98 head 350 making 320 HP. It had the 46# high pressure injectors in it.

Again . a small block , not a big block which was what I was referring to .

My big block 2" marine TBI came off a 405 HP 496/502 and had the 28-32 psi regulator on it and high pressure 61# injectors.

Depending on year this could have been a possibility, these systems mimicked the 94-95 light truck systems. Again , a marine application so it really isn't relevant to the light truck design we are discussing.

TOM

[Chewy1576]

Actually you really wouldn't want it to run like that. When you have massive injectors its hard to control the fuel delivery accurately. You really should supply the engine with just enough fuel to keep you under 85% duty cycle at your WOT shift points.

Do you know of any .ads files that include a readout for Injector Duty Cycle that will work with a 1228747 ECM? Will the 1227747 $42 mask work to display that data?