Help me brake in my 383 cam...........

[kayjef]

So I am new to the site, but have been reading here for a long time. I am a novice when it comes to tuning, but want to try and do it myself.

Truck 88 GMC Jimmy (fullsize)
Motor: 383 stroker (10:1)
Cam: SUM-1105 flat tappet cam. (summitracing)
Aluminum 190cc heads (64cc chamber)
Stock 454 Throttle body (80lb injectors)

My ecm right now is a 7747 and has a stock 350 tune.

I don't want to ruin my new cam by having a tune that won't start up and run good enough to break the cam in right away. I don't need it to run perfect, just good enough at first, and then I can fine tune if from there. I am assuming my current stock 350 tune isn't up to the task, but I wonder if I could do a stock 7.4L tbi tune to break the cam in? I know one guy who successfully did this, but it was with a 350 with a cam. I would assume it would work better with the added displacement of the 383.

I am thinking the easiest thing to do is snag someone's bin for a moderately built 383 who used big block injectors and go from there.
Any help is appreciated.

[dave w]

If you can you burn your own chip, the attached screen shot is the BPW for a '7747 / 383 / 80 lb. injectors.

dave w

[RobertISaar]

a neat trick may be to temporarily setup the commanded idle speed tables to the 2000 or so RPM you'll be spinning the engine at for the break-in procedure.

[kayjef]

Thanks for the quick reply.

Edit: My best guess is about 350hp with this motor. According to some calculations I have done it looks like that requires around 100lb/hr per injector. I have a fuel pressure regulator and it looks like I will need at least 18psi to get close to those numbers. So that means I will need to set a different BPW than that quoted 114 above right?

It probably isn't absolutely necessary to have it perfect to break the cam in, but my reading tells me having the BPW set as close to reality will make for easier tuning.

Thanks.

[dave w]

Very few of the engines I tune goes to the dyno. One of the TBI / Vortec 350 engines I tuned produced 330 RWHP, with a 16197427 PCM (RIP '7747), using 15 PSI fuel pressure and 5235231 (early 454 injectors).

I think a 16197427 PCM and Wide Band O2 Sensor (WBO2) would be almost mandatory for tuning your engine.

dave w

[Chewy1576]

I used a stock bin for a 350/5 speed as my baseline and modified the BPW for 80 lb/hr injectors and 18 psi FP. It was a good starting point.

[kayjef]

I used a stock bin for a 350/5 speed as my baseline and modified the BPW for 80 lb/hr injectors and 18 psi FP. It was a good starting point.

Hey Chewy, I read all your threads and although your cam is a little more mild than mine, everything else is rather similar. I downloaded your 'Blueprint 383 Chip v3.bin' (thanks for sharing ) and holy crap it is a lot different than than my stock bin (ASDU-$42-5.7L-Auto). The VE graph jumps around a lot whereas my stock one is substantially more smooth. Same goes for a lot of other tables. Is this one of the final tunes you did or were these substantially changed past where they are in this version?

If you can't tell I am a noob at tuning, but have been researching like a mother to try and not screw it up. Autoprom and a wideband 02 sensor is in the mail. So I should be operational here in a week and hopefully ready to fire this thing up a little after that.

[Chewy1576]

Hey Chewy, I read all your threads and although your cam is a little more mild than mine, everything else is rather similar. I downloaded your 'Blueprint 383 Chip v3.bin' (thanks for sharing ) and holy crap it is a lot different than than my stock bin (ASDU-$42-5.7L-Auto). The VE graph jumps around a lot whereas my stock one is substantially more smooth. Same goes for a lot of other tables. Is this one of the final tunes you did or were these substantially changed past where they are in this version?

If you can't tell I am a noob at tuning, but have been researching like a mother to try and not screw it up. Autoprom and a wideband 02 sensor is in the mail. So I should be operational here in a week and hopefully ready to fire this thing up a little after that.

That bin was created a long time ago. I have done a lot of improving since then. Also, I'm running a different ECM than you are (Mine is 1228747) so I am using different XDF and ADS files. The addressing between the two could be offset to where the VE table is reading data other than VE data.

[kayjef]

That bin was created a long time ago. I have done a lot of improving since then. Also, I'm running a different ECM than you are (Mine is 1228747) so I am using different XDF and ADS files. The addressing between the two could be offset to where the VE table is reading data other than VE data.

Yeah I think that's it. It's too far off to make any sense. I was using 7747 ADS and XDF files. Rookie mistake...

I love this site, glad I found this thread for some before start up tips...

http://www.gearhead-efi.com/Fuel-Inj...odified-engine

A quote from that thread...

"A few things I do before startup.
Set BPW accoring to your new injectors, and if you have voltage compensation set it too. You would be supprised the difference it makes, particuarly at idle and startup. If you can't find the voltage specs for your injectors, I would suggest sending them out to get them done.
Set a base spark table according to the engine you are running. Most chev's I have done like 34 - 36 degrees total. As mentioned above, cammed engines like more idle timing. You will get away with quite high mid range timing values and it will help to keep the engine smooth. Keep an eye out for knock though. A bit of research here pays off in the amount of time required to tune the engine. Keep the table smooth and transitional. Smooth spark table = smooth runnning engine.
You can get a basic VE map going, remember that cammed engines use less down low and more up high. Try not to exceed 80-85% VE. If you need to, alter your BPW to compensate.
Don't fiddle too much with it until the engine warms up unless it is drastically rich or lean.
If you have fitted bigger injectors, look at your cranking fuel and reduce to suit.
Mask your o2 sensor codes until you get it roughed in. (assuming that you will be using a wideband)
Increase your target idle speed. Cammed engines like to idle a little higher. Watch you don't go too high, particularly with autos using a stock converter.
A richer idle will also keep it smooth so ensure that it doesn't go into closed loop fueling around idle. Depending on the cam, it will idle at lower vaccum so concertrate around 45-55kpa for a mild cam and 60-70kpa for a larger cam.
Oh, and check for codes at key on. Fix the issues BEFORE starting the engine!"

Lots for me to chew over... now if I could just figure out how to actually make all that happen in tunerpro...

[Chewy1576]

Why have I not seen that thread before?! After swapping to a BB TB on my 383 I feel like I'm starting all over. I have the minimum idle screw backed all the way out and the idle speed will barely get down to around 600 RPM. The idle surges and it runs fairly rich. I'm going to be taking a lot of this tips and hopefully this weekend getting it running well again.

[kayjef]

Why have I not seen that thread before?! After swapping to a BB TB on my 383 I feel like I'm starting all over. I have the minimum idle screw backed all the way out and the idle speed will barely get down to around 600 RPM. The idle surges and it runs fairly rich. I'm going to be taking a lot of this tips and hopefully this weekend getting it running well again.

Let me know how that goes. I plan on bumping my idle up to about 800-900. This is an offroad truck only and the quicker the power the better. Plus it helps my ps pump while steering my 44" boggers at idle. I figure that should smooth out the idle. Summit says this cam has a 'noticeable' idle but not lopey so I figure it should be pretty smooth at 800.

[Chewy1576]

Let me know how that goes. I plan on bumping my idle up to about 800-900. This is an offroad truck only and the quicker the power the better. Plus it helps my ps pump while steering my 44" boggers at idle. I figure that should smooth out the idle. Summit says this cam has a 'noticeable' idle but not lopey so I figure it should be pretty smooth at 800.

I'm going to bump my idle to 800 also. I have a chip ready to go, just need to go get the truck.

[Chewy1576]

Got some time after work to try the new chip and make some VE tuning runs. Open and closed loop idle and low speed decel suck again, always dropping RPM and recovering but doesn't die. Idle MAP reading seems really low to me also. Another thing that is happening now that I don't remember seeing is BLM's go to around 140 on decel (probably DFCO, but I disabled it for the last log and it's still happening). Going to need more work but I attached what I came up with.

[kayjef]

Alright guys, I have learned a lot and are still learning.

I changed a lot of things in my bin in tunerpro.

BPW, EGR deleted, bumped up closed loop idle, made some changes that I thought would keep idle in open loop, changed the spark advance table and ve table to what I think would work good with my cam. Basically tried to get info about every parameter in tunerpro, lots of stuff I still have no clue what it does but I feel like I have a decent understanding of the rest.

So I burned a chip with my autoprom and started up the motor. It ran! hooray. I broke in the cam but it obviously wasn't running perfect by any means. Was backfiring out the throttle body on decel at about 1500 rpm. My original scan was showing weird numbers for spark advance and a few other parameters. I learned that I needed to apply the hacks in the $42 asdu 7747 bin. Applied them and then it was scanning good. Also my distributor was set at 5 degrees retard, so once I fixed that it stopped backfiring out the intake.

All my sensors are working good, vacuum is good, and I have a fuel pressure gauge installed showing my stock pump maintaining 13psi.

I learned how to emulate in tunerpro and started making changes while running. Boy does that save some time.

I have only messed with the spark advance table but I flattened the cells where the truck was idling and then started changing the timing in different parts of the table. I feel like it's getting better but here are some issues I am having.

I thought I made changes to keep the idle in open loop (big block settings posted somewhere else on this site) but it is idling closed loop. It idles fine in closed loop but it is really rich and makes it hard to tune. Open loop is not as rich, but haunts around a bit. Any suggestions?

I will try and post my files when I figure out how to attach them to my posts.