ChevyKen

iTrader: (1)

I've got a "new" ECM on the way that has a prom from a 350TPI vette in it - can I use it, or at least try it on my 305TPI, or will I get problems?
Im trying to track down some problems with my car, and it would be great if I could use the prom in the new ECM to check if there are any problems with the stock one.


Thanks,

Ken

V8Astro Captain

iTrader: (1)

"Work"...yes. Work well...not at all.

ChevyKen

iTrader: (1)

Thanks,
Care to share what kind of problems it might result in?


Ken

kevinc

Depending on what year Vette it came from, it probably has VATS (Vehicle Anti-Theft System, resistor in the key, sensor in the keylock, won't start without it). If this is the case you're out of luck or in for some nontrivial wiring hacking to bypass it.

If VATS isn't there and it starts, you'll probably be running way lean. The 350 software is configured for injectors flowing 22lb/hr, your 305 has 19/hr injectors, which means they'll be flowing much less fuel per millisecond of open time than the computer thinks they are flowing.

I'd sell the Vette memcal and not bother with it.

ChevyKen

iTrader: (1)

Hey, thanks kevinc - that makes sense!!
BTW, the VATS is disabled in it.

As a sidepoint - I more than likely will get bigger injectors shortly, so I might just hang on to it and try it at that point if that is the only thing that will bother it.

Thanks again,



Ken

Grumpy

<sigh>
let's see, a 350 is about 16% larger then a 305. A 22 #/hr injector is about 16% larger then a 19.
If you want to use logic, might look at the larger picture.

I'm by no means endorsing using the wrong memcal, and I wouldn't even try it, but just correcting the notion of lean as in being a major problem.

There are even other issues like the battery voltage corrections, and if MAF then the scalers (as applicable). So there are so many issues, that it would be easier to just start with the *most right* calibration.

james_85Z28

You can still use the memcal, just not the current data on the PROM. To make life easier for yourself try one of Craig Moates adapters, buy a new EPROM, and go from there. And if you have the equipment to change data on the EPROM you can quickly change the vette PROM data and use the bare memcal as a standard backup.

ChevyKen

iTrader: (1)

Well, Im not too strong in the ECM & Prom terminology, and not ready to start making my own stuff at this point.
But I totally understand the warnings regarding the differences in the engine. I'll just try the new ECM with my stock prom, and if I still have problems, I'll go for a custom prom after that to accomodate my mods.



Thanks a lot for the inputs, I very much appreciate it!!


Ken

Kevin91Z

iTrader: (1)

The biggest problem I had when trying a 91 Corvette bin in my car was the Oil Temp Sensor. F-bodies dont have one, and the Corvette prom looked for one. So I got an SES light Code 52 every time I got on the freeway for 10-15 minutes. That was annoying, so I found an f-body bin and used that. This was a long time ago before I started doing my own chips... And yes I used a 305 5-speed bin in my 350 5-speed for quite a while. No problems to speak of.

Grim Reaper

Chevy Ken, is the new ECM/Memcal SD or MAF - it makes a big difference.

For SD, as Grumpy and Kevin both pointed out, you can actually get by with a 305 SD eprom on a 350 (and vice versa). This is because the difference in the displacement and injector size are both 16%. Thus a 305 with 19#s actually result in pretty much the same fuel metering as a 350 with 22#s. However, if you are running different injectors on either, then you will need to adjust the eprom accordingly.

With MAF, this will not work. This is because the MAF actually compensates for fuel based on air flow - the ECM doesn't know (or care) what size of engine it is - the MAF does it all. What is important is your injector size. Thus if you have a 305 Memcal in a 350, you will need the 19# injectors on the 350 or you need to adjust the injector size in the memcal. Conversely, if you run 350 MAF memcal on a 305, you would need the 22# injectors on the 305 for the same reason above.

SD and MAF don't work the same when it comes to running Memcals from other engines. MAF only is concerned about Injector Size and doesn't know a THING about the engine size. While SD needs to know both. And, as Bruce pointed out, SD 350s and SD 305s just happen to "match" in that the increase in displacement matches the increase in injector size.

ChevyKen

iTrader: (1)

Thanks Kevin and Glenn,

The ECM is a 16198259, which I was told was a direct replacement for my 1227165 - which is a MAF car as Im sure you all know.

My 305 has a CompCam, headers/cat-back, SLP runners, WP S/R Torquer heads, and a few other minor mods - but still the stock injectors. I've considered going up to 22 lbs injectors as Im experiencing hesitating at around 2-2500 rpms when hitting WOT, and Im thinking it *might* be lack of fuel as I tend to get the lean O2 sensor error when this happens.

Im a little confused now from the replies - would changing the injectors actually solve the mismatching problem with the 350 prom since my car is MAF, or will other differences still make it unusable?

Thanks again - sorry Im a slow learner on this subject...



Ken

Grim Reaper

With MAF, the injector size in the eprom MUST MATCH what you are actually using. If you have a 350 with 19# injectors, you can use a 305 (though you might risk running lean). A 305 with 22# injectors can use a 350 eprom. Anything else with MAF and you need the injector size in the eprom changed. You can't compare it to SD, it works differently - so I won't discuss it further to avoid any more confusion.

But, to get the optimal spark tables (which are the real key to power in eprom buring once you get the mixture right), you STILL must burn your own eprom since it requires a LOT of testing to find the optimal spark advance.

NO CUSTOM EPROM written by someone WITHOUT access to your engine will be able to give you that optimum spark table. There is only a few degrees THROUGHOUT the ENTIRE spark curve (and you need to look at the entire curve) between an eprom that performs: reasonably okay (like stock), great (like a well tuned eprom), causes detonation or runs like a dog. It can almost be unique as a "fingerprint" between two otherwise identical engines.

Forget "plug 'n play" solutions - they are a "compromise" at best, and a compromise generally does NOTHING right.

grumpygreaseape

hi-heres my first post on this board. how i found thirdgen was while searching the net about improving the performance of my car thru working the computer. what i found out there (mainly here) was a mindboggling array of new info and ideas to get a grasp on, and up till last year or so, i thought myself pretty bad a-s cuz in 89 or 90 i got my iroc running pretty good with a 406ci motor-it astounded the naysayers in my peer group-and it was cool for awhile, well then i started reading posts by GLEN91L98GTA and grumpy-nice name-and suddenly i was so small i couldnt even see myself, so here i be with the first inquiry-up till yesterday, when i read GLEN91's post that seemed to semi, well actually completely to an extent, support working a maf system to an acceptable performance level (maf to speed density. any dis advantages?)ive been gearing up to ditch the ole' 870 and have already procured the ecm, a 730, knock sensor, map sensor,basically most all stuff in my 85 z28 and eprom project website calls for even have the pre-requisite schematics hanging everywhere in the room where im typing this. HERE IT IS-would it be worth it even as a)a learning experience or b) an actual keeper of a modification, to work my 870's chip and see what i can attain with it? im willing to switch ecms but if and when i do, it will be to a 730 and not a 165. tunercat is what i will use either way and to purchase another definition file ($1F) isnt going to break the bank. i wish (kind of) that i didnt hear good things about a maf system at this stage but maybe if you think its worth a try for me, keeping in mind my experience level, ive searched and do understand generally an 870 isnt a good first try set-up-but my iroc isnt a daily driver so no pressure there, whats the consensus among those in the know? should i give it a shot? any input is welcome. thanks, frank

Grim Reaper

TunerCat does have a TDF for the 870, it just isn't that well defined. But, as a "starting point" (and it's only $20...everything else is "re-useable"), it not a bad way to learn. This way you can do some experimentation and see how things affect it.

Then, when you are ready, you can swap the ECM and you'll have a little "tuning" under your belt.

Jim85IROC

iTrader: (2)

Ken... just to illustate how poorly a car can run with the wrong chip, my 85 IROC has 24lb/hr SVO injectors on top of a fairly well modified 350. I'm still running the stock ECM and chip that's set up for 19lb injectors. The car has run a best of 16.1 so far. Hell of a time for a built 350, hey? The car had other problems (Like a slipping trans and no traction) but the car is a pig.

Either track down a stock 305 chip (I'm sure plenty of people will be willing to donate their unused chip) or start burning some!

ChevyKen

iTrader: (1)

Thanks again Glenn and Jim,

Well, seems like the way to go initially is to just swap the ECM's (using the stock 305 prom) and see if that fixes the problems Im encountering, and if not - I will have to figure out what to do with the chip.
The thing is, Im in my last semester in college so I have zero extra time to start figuring out the prom burning stuff at this point - yet the Camaro is the only car the wife and I have, and the car is still having enough issues that she refuse to drive it (may not be a bad thing, ehe?).
So, if it doesn't straighten out now - I probably *have* to settle for a custom burned prom from Ed Wright or something - do you all consider that a complete waste, or is it a chance it would run decent with it?

There are always different opinions on when/if to replace the prom. I've asked numerous people if I should after last fall's engine upgrades (cam/heads/runners/headers/catback), and the answers are pretty much divided. Some say no need to until extensive mods, other say "hell yeah" I need to get a new prom.
All I know is that I have had problems since these mods were installed.

For those who have not read other posts regarding my problems in the other forums, the main things that are still bothering it are:
1. If going WOT from a roll the car will hesitate strongly around 2500-3000, then pick up very well but throw a code 43.
2. When starting up when cold (as in over night), it will not run on idle OR by holding it at i.e.1500 rpm. It will just die. However, it will run, but rough, when varying the rpms by pumping the gas.
BUT, what really throws me off is that once I get it in drive without killing it and start rolling down the road - it is perfectly fine.


Im at a toss with what can cause it, but my guesses have been ECM, prom or injectors (size?).
I got the ECM for a decent price and thus decided to try that first.

Thanks yet again,

Ken

grumpygreaseape

i dont think its a prom\ecm problem-code 43 is an esc spark timing malfunction-kind of works along with the symptoms of hesitation that you describe. have you set base timing
? with black\tan wire disconnected? balancer has not spun? it also sounds like a classic maf sensor failure behavior-does driveabilty improve when maf is disconnected? what is the year and mods done on the car?

ChevyKen

iTrader: (1)

Thanks grumpygreaseape,

Well, I've tried nearly everything that I can think of:
* Timing is set at 9° with blk/tan wire disconnected
* Replaced timing unit in distributor
* New plug wires
* New plugs
* Balancer is new
* No improvement by disconnecting MAF
* New TPS
* New alternator

Car:
1986 IROC-Z convt
305TPI
TH700R4

Mods are as follows:
* CompCam (12-256-4)/lifters
* World Products S/R Torquer Heads
* JHC Edelbrock TES headers
* Edelbrock RPM Cat-back
* CatCo cat
* SLP runners w/portmatched plenum* K&N's
* +airfoil, !MAF screens, !airfilterbox

Still have stock:
* ECM
* PROM
* Injectors

Also occationally get a code 44 with the 43.

Thanks,

Ken

grumpygreaseape

fuel pressure is tolerable 35-45 psi? balancer has been eyeballed with the original to ensure matching timing marks? 44 is a lean exhaust code. fuel volume is ok? pint in 30 seconds? i believe 6 degrees is initial- no biggie-vacuum leaks are not, not an issue here correct? either internal-egr or external injector o-rings, all gasketed joints in the tpi intake system,pcv valve isnt hung,power brake booster isnt leaking internally, cannister purge is good,whats the condition of all intake ductwork after the maf-any cracked rubber,loose clamps that are allowing false air (unmetered) into the engine, bass ackwards maf installed arrow to air cleaner,all ecm system grounds are in place and showing minimal voltage drop? to get 44 you ARE seeing closed loop-1 good thing out of this so far- and are you able to get your hands on a scan tool? blm #'s should be showing up around 150 or so in the range where 44 is set-are blms high across the board? lemme know if scan tool is happening for you.

ChevyKen

iTrader: (1)

* The fuel pressure is right around 42psi,
* The balancer was installed right before the mods and the car ran perfect, so I know it is confirmed correct.
* What exactly do you mean by "fuel voume is okay"?
* As for the vaccuum leaks, I have not been able to confirm that there is no leak. I've tried to ask and search for how to confirm that but have not figured that out yet. Any help on that is appreciated. However, there are NO known vaccuum leaks, and I have gone over all the connections I know of and replaced a lote of the hoses.
* The gaskets on the TPI were fine when installed with the mods, will replace the upper runner gaskets when installing the AFPR though.
* Will check the PCV valve, it is fairly new though.
* Not sure what the internal egr O-rings are?
* Injector O-rings were replaced during the mods, as were those end "caps" (can't think of the correct name).
* Have not checked the brake booster, how can that be done?
* Canister purge, everything connected and the connectors on top get a little warm while running - not sure how to confirm that it is working correctly.
* Intake duct seems to be in great condition, and clamps are tight
* MAF was never off the airfilter duct, so it is in the correct way
* I'm not confident that I know of all the ECM system grounds. That was one of my thoughts as well, and I checked the ground connection on the back of the pass. side cylinder head (towards the firewall) since I obviously had them off when swapping heads. It seemed fine, tight and with no voltage loss. Where are other connections that I should check?
*I do not have access to a scan tool. Are you talking about the ones for laptops etc. or a separate tool?


Thanks a whole lot for all the good inputs,


Ken

grumpygreaseape

fuel volume=quantity of fuel pumped into a graduated container over a specific time interval, this case requires that the pump puts out 1 pint in a 30 second stretch.(minimum) if the pump isnt capable of supplying the pint it isnt up to running the car.pressure\volume 2 different but related measures.
HEY-did you have the plenum off the runners,and the runners unbolted from the base? the mods below were performed and upon firing it up again with the new stuff-that is when the headaches here started? just trying for some history here on this. anyhow back to the runner/plenum/base question-do you know how easy it is to install 2 of the runner bottom to intake base gaskets perfectly backwards? when flipped on install the resulting HUGE vacuum leak has caused a few tears on more than a few wrench spinners. like leaving the air deflector off up front-small detail-big problem. vacuum leaks are safely located using propane fu-k safe-time to fix this car cuz i am the worst freaking typer that i have ever seen and why cant the c--ksuckers put the keys in order like the alphabet? go to autosupply and buy a couple spray cans of good old carb.cleaner. berryman type stuff smells strong and flammable-not gunk type stuff-paint peels when the stuff sets on it, thats what we want. go to car. can i assume that you are aware of the dangers of spraying carb spray on a running motor? be safe, put red extension in place and run motor at an rpm that is stable say 1500-2000-start gently and carefully sprayind carb spray on all the gasketed joints plenum.runners,t-body, you will get the hang-where motor speed increases when spray hits that a vacuum leak-i bet you have gaskets reversed now though-ck.booster integrity by pinching vacuum line to it w/pliers to cut feed to it if an idle improvement is felt then the booster is leaking -use same pinch method on all vac lines to check for leaks. scanner=mt2500 ,otc monitor, etc paper clip is what got you the codes then? till next go around i think that we are drifting away from this forums subject matter and maybe those in command may mooooove our problem elsewhere.seeya


:rockon: ah ha just sunk in you did have the heads off then this started -otay were gettin there

ChevyKen

iTrader: (1)

I agree - we are drifting off to the intentions of the forum, I will post my reply to your last post to the following thread in the General Engine/Tech forum so we can continue it there.

https://www.thirdgen.org/techbb2/sho...threadid=80231

See ya there!!

Ken