PLEASE HELP ZZ383/425 with TPI/MPI tuning help.

[Mr Hyde]

Hi,

I am new here and have a problem..I found this site while trying to find answers to my questions on-line.

Here is what I got. A 1963 Chevy C-10 Stepside. Motor is a GM crate ZZ383/425, 700R4 tranny, 9" with 355 gears and a Street and Performance MPI unit with 2 1/2" riser blocks. It has a 1227730 computer. Currently has 24 lb injectors.

PROBLEM...truck won't run. Street and Performance sent me what they call a start up tune.

I put a wideband on it and at idle it dies A/F ratio over 18...it will stay running at about 2k rpms and A/F is around 13.5 to 14.3.

I have changed plugs, installed new wiring harness, 8mm plug wires etc...and still no dice.

Where do I go from here? Are 24 lb injectors big enough?

Any help would be greatly appreciated.

john

[randeez]

welcome to the site, you will probably want to post in the mpfi section (subforum under this one) for related limits of injectors or in the open performance forum... i am not familiar with the ecm supplied, but you'll need to modify the tune for your set up- hopefully it came with some sort of tuning software or can be loaded with modified bins by tunercat, etc.- with the wideband reading an afr of 18 you'll need more fuel at idle (obviously) have you calculated how much fuel pressure you will need to achieve 400+ hp with this set up?

[Mr Hyde]

Randeez,

Thanks for the information wasn't real sure where to post this thread.

Unfortunately they sent no software with this system. Street and Performance recommends a fuel pressure from 40 to 45 but at this point I am not really sure that is correct.

In my very layman opinion I don't really think they actually know either. I have been " Told" that 24 lb injectors are good for crusing but nothing else and it will starve the motor for fuel at higher RPMS.

The problem is that this is an outdated system for performance motors and not alot of people know or work on this type. I thought after spending a TON of money with Street and Performance that this would not be an issue. Really disappointed in their product, cust service etc.......It looks good but I like function as well. I really think they sent me a stock 350 tune and it just ain't working.

[randeez]

as it may be the "start up tune" is possibly just a stock bin loaded onto it, you'll wan to research what provisions the ecm has for tuning, if none- you can get chips a burner and socket, an emulator, or a complete tunable ecm- such as the ebl flash. a lot of the software is free (donations accepted) and there is plenty of bins (tunes) out there you can try. thirdgen.org is a great resource for gm tuning, imo- they as a community have busted gm obd 1 open and explained it very well. moates.com has a lot of obd 1 hardware and software. tunercat.com has a bin and xdf modifier that a lot of people use.

[Mr Hyde]

Well funny you should mention that....I went to 3rd Gen to see if anyone had a tune close to what I needed and didn't get much response, matter of fact I went to alot of forums and searched with no luck.

I decided to become a member here since I am a Chevy nut and own a 2006 2500 Duramax, 2010 Camaro SS plus a few other older Chevy's.

I do have a friend who is trying to help me on this truck as it has been a NIGHTMARE....A long story for a different time..........problem is that most of his tuning stuff is for Honda's, he is a Mod on 3rd Gen and he searched awhile with no luck. I was hoping someone may have a close Bin File.

Once I get it running correctly I will post some photos of it.....Unsure if they have a member area for vehicle here, havent really looked all over this site.

I am thinking that ZZ383 with a min of 425 horse will be plenty enough to get the old 63 Chevy Stepside a moving....

Matt is pretty good at this stuff but without the right equipment and knowledge it just takes a LONG time.

[randeez]

well hopefully you'll find the help you need, sounds mechanically like you've got a stout set up - there are a few members here running obd 1 mpfi , but most obd 1 are tbi because thats what came in era trucks

[Mr Hyde]

Well in my ignorance I went with the S& P fuel injection because of looks.....Chrome sure does look good under a hood, LOL

If I had it to do over I would put a LS3 in it and be done since they are alot more prevalent nowadays but hindsight is 20/20.......

It should be a beast when I get it right....just the inexperience bug is hitting me now.

[907 Chevy]

Those 24# injectors won't feed that engine. You'll need just about 34 lb/hr injectors to support 425hp @ 80% duty cycle.

That's assuming 0.5 brake specific fuel consumption. Your engine may have a slightly lower bsfc since those fast burn heads are probably pretty efficient at making power.
Assuming a 0.45 bsfc the required injector flow rate drops to just under 30 lb/hr.

The formula is pretty simple...

Brake horse power*brake specific fuel consumption/ number of injectors*80% duty cycle

e.g, 425 bhp*0.45 bsfc = 191.25 pounds hour of fuel required
8 injectors*0.80 duty cycle = 6.4
191.25/6.4 = 29.88 required injector flow rate

[Fast305]

Those 24# injectors won't feed that engine. You'll need just about 34 lb/hr injectors to support 425hp @ 80% duty cycle.

That's assuming 0.5 brake specific fuel consumption. Your engine may have a slightly lower bsfc since those fast burn heads are probably pretty efficient at making power.
Assuming a 0.45 bsfc the required injector flow rate drops to just under 30 lb/hr.

The formula is pretty simple...

Brake horse power*brake specific fuel consumption/ number of injectors*80% duty cycle

e.g, 425 bhp*0.45 bsfc = 191.25 pounds hour of fuel required
8 injectors*0.80 duty cycle = 6.4
191.25/6.4 = 29.88 required injector flow rate

The 24# injectors will feed ~400 HP all day long and will feed closer to 450 @ 50psi. Just look at how many bolt-on 400+ HP LT1 engines still have their stock 24# injectors. If you need a touch more fuel, bump the pressure up with an adjustable regulator. As for running lean, sounds like you have a problem with the fuel map they wrote. Luckily for you the 7730 ECM can easily be chipped and tuned with readily made tuning files. I ran a version of the code that was modified to allow an input of a wideband, larger fuel tables up over 6,400 rpm, among other updates. The 7730 can control electric cooling fan relays and an a/c compressor via a relay.

[907 Chevy]

The 24# injectors will feed ~400 HP all day long and will feed closer to 450 @ 50psi. Just look at how many bolt-on 400+ HP LT1 engines still have their stock 24# injectors. If you need a touch more fuel, bump the pressure up with an adjustable regulator. As for running lean, sounds like you have a problem with the fuel map they wrote. Luckily for you the 7730 ECM can easily be chipped and tuned with readily made tuning files. I ran a version of the code that was modified to allow an input of a wideband, larger fuel tables up over 6,400 rpm, among other updates. The 7730 can control electric cooling fan relays and an a/c compressor via a relay.

Huh? You'd have to put over 65 psi to those injectors to feed a 425 horse engine,let alone a 450 hp powerplant.

Anyways,my point was that the op is gonna need larger injectors whether from installing larger injectors or bumping up fuel pressure.

[Mr Hyde]

Well being a novice at this tuning stuff, LOL I went and talked with my friend this weekend who is helping me tune this motor.

I learned alot and really learned I have no clue about tuning...the days of turning a screw is long gone. The VE tables were crazy to look at......

When I started I had no idea what the 7730 would control and the shop who installed this didn't either, they were clueless. I did a couple of things in a different way.

I ran the fuel pump, and cooling fans seperately from the computer. I ran the fuel pump power from the main wiring harness so that I could cut fuel by use of a well hidden switch. I did this as sort of an anti-theft system.

I ran the cooling fan through a relay that comes on at 185 and cuts off at 170. I also wired it so it would run continuously when the A/C came on, it also runs even if the motor is turned off. Since I had to re-wire the entire truck it was pretty simple to do.

Had to order some items from Moates so it will be a few days before we can get back to tuning...one good thing is that we will be able to hook it up directly to a laptop and datalog it once we get the things from Moates.

[Eagle-Mark]

Your really going to need to learn how to record data and change the bin file on chip. Since you've been to Moates you are on to a good start. Next thing you need is software. TunerPro is free to try and only $40 to buy and is by far best available for OBDI type ECM/PCM and will be expanding to OBDII soon.

I've done some write ups on how to get started with TunerPro. All files you need for your ECM are available. Do you know your mask ID? Start here:
http://www.gearhead-efi.com/Fuel-Inj...ro-Tuning-Talk

As far as HP and injector size, fuel pressure and BPW needed we also have some great spread sheets that get you where you need to be. It's a real pain to get a good tune going to find out your going lean WOT. Then bigger injectors, more pressure and you start to tune all over again...

[96ImpSS]

Just another comment on injector size. To echo Fast305's point, The people that are making a lot of power and going fast discovered long ago that those injector formulas are conservative to say the least. They simply desregard them and run what works best. You can see over 100% duty cylce reported by a datalogger and yet the wideband doesn't go lean.
More power is to be made by running smaller injectors, keeping them open longer (some speculate that this results in more of the correct spray pattern rather than the "dribble" during injector transients). SVO 30 lb injectors are supporting 500 RWHP and also doing duty in a 450 rwhp roadracer for about 8 seasons with no issues. Some stock eliminator guys run the 24 lb SVO's to over 400 rwhp.
If you get into the low impedance injectors that some huge power setups run, then I can see the heat factor leading to injector failure, but it's just not happening on the typical high impedance injectors.

[Mr Hyde]

Your really going to need to learn how to record data and change the bin file on chip. Since you've been to Moates you are on to a good start. Next thing you need is software. TunerPro is free to try and only $40 to buy and is by far best available for OBDI type ECM/PCM and will be expanding to OBDII soon.

I've done some write ups on how to get started with TunerPro. All files you need for your ECM are available. Do you know your mask ID? Start here:
http://www.gearhead-efi.com/Fuel-Inj...ro-Tuning-Talk

As far as HP and injector size, fuel pressure and BPW needed we also have some great spread sheets that get you where you need to be. It's a real pain to get a good tune going to find out your going lean WOT. Then bigger injectors, more pressure and you start to tune all over again...

Mark,

I really appreciate the information......I have a friend who is real familiar with moates and tuning...but he tunes Honda's and he is helping me with all of this. Basically I see A LOT of math formulas that go into a tune.

The tune Stret and Performance sent me originally simply does not work...It will not stay running as it leans out at idle, runs OK at 2000 rpms but when we looked at the VE tables it said 99% efficiency at 1600 rpms and drop every 100 rpm or so. I have alot to learn about all this and will definitely check out the link you provided. I really appreciate your help.

I do not know what the Mask ID is?

What is that?

Just another comment on injector size. To echo Fast305's point, The people that are making a lot of power and going fast discovered long ago that those injector formulas are conservative to say the least. They simply desregard them and run what works best. You can see over 100% duty cylce reported by a datalogger and yet the wideband doesn't go lean.
More power is to be made by running smaller injectors, keeping them open longer (some speculate that this results in more of the correct spray pattern rather than the "dribble" during injector transients). SVO 30 lb injectors are supporting 500 RWHP and also doing duty in a 450 rwhp roadracer for about 8 seasons with no issues. Some stock eliminator guys run the 24 lb SVO's to over 400 rwhp.
If you get into the low impedance injectors that some huge power setups run, then I can see the heat factor leading to injector failure, but it's just not happening on the typical high impedance injectors.

Pat,

Injector size...I have no clue........From my novice knowledge the only thing I know is that if you lean a motor out then it is not long for the living. The things we bought from moates will allow me to datalog this thing once we get in running.

As with anything , everyone has a different way to do things and I am in the unfortunate posititon of having to listen because of no knowledge.

A couple of people have told me as long as I don't go over 55 lb injectors I will be fine but 24 will starve the motor of fuel......In all honesty I don't know but am trying to learn.

I will say this that the truck will not be used to race moreover a cruiser that I will get on periodically. Out of the box thsi motor is suppose to have 425 hp/449 tq and that is supposedly a conservative number from GM, based on drivetrain loss I should see around 350 or so to the wheels. Defiitely alot more than the 327 that I took out of it...at least I hope so...LOL

[Eagle-Mark]

Mark,

I really appreciate the information......I have a friend who is real familiar with moates and tuning...but he tunes Honda's and he is helping me with all of this. Basically I see A LOT of math formulas that go into a tune.

The tune Stret and Performance sent me originally simply does not work...It will not stay running as it leans out at idle, runs OK at 2000 rpms but when we looked at the VE tables it said 99% efficiency at 1600 rpms and drop every 100 rpm or so. I have alot to learn about all this and will definitely check out the link you provided. I really appreciate your help.

I do not know what the Mask ID is?

What is that?

The mask ID is what is used to read the bin file on the chip. What is your ECM/PCM number and BCC code? They should be on a sticker on the ECM/PCM. Or open the cover and there will be four letters on chip.

99% VE is really high and your injectors could be going static (never close and glitch, not good) rule of thumb for tuning is stay below 95%. If your BLM are still lean then your going to need more fuel pressure.

Going lean at idle? That's a lot of HP and without cam specs @.050 I am just guessing it's low vacuum which can be tuned out to run fine. But that usually casues rich, not lean. Have you read your plugs yet? I'd also do a good thorough vacuum leak test. Having a vacuum leak near one cylinder will really mess up what the O2 sensor is reading and it will make all the wrong adjustments.

Knowing your fuel pressure and that it is not dropping at WOT is something your going to have to know. No reason to tune idle if you don't have enough fuel WOT and go lean. Once you get connected and get a data log it will tell a lot!

[Mr Hyde]

The mask ID is what is used to read the bin file on the chip. What is your ECM/PCM number and BCC code? They should be on a sticker on the ECM/PCM. Or open the cover and there will be four letters on chip.

99% VE is really high and your injectors could be going static (never close and glitch, not good) rule of thumb for tuning is stay below 95%. If your BLM are still lean then your going to need more fuel pressure.

Going lean at idle? That's a lot of HP and without cam specs @.050 I am just guessing it's low vacuum which can be tuned out to run fine. But that usually casues rich, not lean. Have you read your plugs yet? I'd also do a good thorough vacuum leak test. Having a vacuum leak near one cylinder will really mess up what the O2 sensor is reading and it will make all the wrong adjustments.

Knowing your fuel pressure and that it is not dropping at WOT is something your going to have to know. No reason to tune idle if you don't have enough fuel WOT and go lean. Once you get connected and get a data log it will tell a lot!

Mark.

Here are the cam specs from GM.

Lift .509 intake, .528 exhaust
Duration 222 intake 230 exhaust @ .50
Centerline 107 ATDC intake, 117 BTDC exhaust

Cjhecked all the vacuum leaks and fixed them before we started.

Stuff from Moates should be here anyday.

[Eagle-Mark]

That's a lot of cam to tune for idle in EFI. Your going to have a low vacuum reading and the MAP takes low readings as a load and adds more fuel when you need less! May have to force an open loop idle, after that should tune OK.

Like all the guys said above 24lb injectors are not going to supply enough fuel for 425 hp at standard 43.5 psi. 24lb injectors at 43.5 psi is good for about 307.2 HP. At 43.5 psi you would need 33lb injectors. There are calculaters for this here:http://www.injector.com/injectorselection.php

I don't know what pressure you would need for 24 lb injectors and your HP?

[cancritter]

when my builder did my engine there was mention of lack of vacum if l went with a larger cam..when l swap my present cam out for larger will add electric vac pump to supliment it...was wondering if vacum could be partialy a cause?

[Mr Hyde]

That's a lot of cam to tune for idle in EFI. Your going to have a low vacuum reading and the MAP takes low readings as a load and adds more fuel when you need less! May have to force an open loop idle, after that should tune OK.

Like all the guys said above 24lb injectors are not going to supply enough fuel for 425 hp at standard 43.5 psi. 24lb injectors at 43.5 psi is good for about 307.2 HP. At 43.5 psi you would need 33lb injectors. There are calculaters for this here:http://www.injector.com/injectorselection.php

I don't know what pressure you would need for 24 lb injectors and your HP?

This is the same thing I am hearing about the injectors.... I have some 42 lb injectors on the way so I should alleviate the fuel problem...hopefully

I think you are exactly right about the MAP and the readings we are showing.

when my builder did my engine there was mention of lack of vacum if l went with a larger cam..when l swap my present cam out for larger will add electric vac pump to supliment it...was wondering if vacum could be partialy a cause?

Really don't know ...but will when I get all the computer stuff from Maotes to really see what it is doing when we datalog it.


NOTE......last night we went looking through the tune that Street and Performance sent....Part of the problem is that it had cu in set at 350...not 383...What is really frustrating is that I actually called Street and Perfromance before I bought this system and they said " Oh Yeah" it will work PERFECTLY and now theyt cant seem to send me a good tune....

I do know when we have been checking it that a vacuum guage and A/F guage has been installed. Matt is tellingme that is what the problem is even though I have no clue about the redaings and what they mean.

But what Mark said I remember Matt saying...that it was doing backwards of what it was supposed to be doing.

Matt seems to think once we get the datalogginf Ostrich, cables etc... that he can see exactly what is going on and then fix it....I have no idea.

[Eagle-Mark]

when my builder did my engine there was mention of lack of vacum if l went with a larger cam..when l swap my present cam out for larger will add electric vac pump to supliment it...was wondering if vacum could be partialy a cause?

Just tune the chip. A electric vacuum pump (if one is made big enough to supplement and engine?) is only a patch for idle, the rest of the chip will still need tuned. If not you just put a cam in you will see no improvements, actually worse... cam makers will say it will run on stock chip. This is true! But to see/.feel/notice and even document any increase at 1/4 mile or dyno? You need to tune the chip.

EFI is no differant the a carburated engine. If you change cam you need to changes jets and timing.

MrHyde, these systems are Speed Density (SD) RPM vs MAP kap (vacuum in metric). MAF (Mass Air Flow) systems take a cam swap much easier becuase it notices air flow has changed at idle. SD does not measure air flow, only vacuum/MAP kpa. It expects to see about 19 inches of vacuum at idle on a stock engine. 0 at WOT.

Cam changes vacuum, more so at idle so you are now 15 inches vacuum at idle. MAP sensor thinks there is a load on engine like 1/4 throttle and adds fuel. Then it gets worse when O2 sensor see's rich and wants's to take away fuel... viciousus circle, ECM is confused. It does not perform miracleses, it can only work within boundarieses it was built for. So you need to adjust fueling table VE (Volumetric Efficiency) which is how much fuel injectors are putting out to begin with, to get in the ball park of what ECM/PCM was designed to do.

42lb injectors has overshot your needs by about 10 pounds, your tuning you have done will be worthless and have to start all over. Adjustable regulater and add 10 psi fuel pressure would be cheaper and get you were you need to be. But I do not know if your fuel pump is capable of this pressure or fuel flow needed at WOT... from what guys have said above the smaller injectors, more pressure and Base Pulse Width changes are better.

Either way that is a big cam. There's no way you will get a perfect tune by mail unless you can datalog and retune the starter tune at least once if the guy has a starter tune for an exact built engine already, even then it is no easy task, even if there are no mechanical issues like vacuum leak, fuel flow issue etc... I have rarely tuned a car with built engine or engine conversion without finding a mechanical issue.