1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

[superseahorse]

I just received a boat at the shop which the customer changed out a 5.0 chevy to a 5.7. The block was cracked from a delayed winterization last year. The engine reman co. told him the engine would hook up the same and everything would work ok. He put the engine in and it doesn't run smooth. It hesitates and possibly runs lean. The first thing i am checking tomorrow is fuel pressure and timing. But if that is good, can the ecu be programmed for a 5.0 and starve fuel ratio to the 5.7? And can they be remapped or does the ecu need replacing?
Any thoughts? I haven't run into this situation before with someone updating engines with different HP and keeping same fuel systems and ecu. Thanks, John

 

[Danny Mc]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

I have done this swap, if the sensors are ok the ECU will correct the fuel curve for the TB.

 

[rodbolt]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

no it wont. it simply CANNOT.
the 5.7 moves more air than the 5.0.
hence the designations.
the whole thing about EFI over a carb is keeping the air to fuel ratio at about 14.7/1.
the 5.0 ECU cant tell that now it is feeding 5.7 liters of air for every complete cylce of the pistons.
its also why the ECU part numbers are different.
aaaahhhh the internet.
my sisters ex husbands cousin once once fixed a john deere, he must know all.

 

[Aloysius]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

With no O2 sensor, the preset fuel/ignition curve will be wrong. Get the correct ECU/PROM!

 

[twistedshadows]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

the harness and sensors should be the same (well maybe not the maf) so you may just need to swap in a ecu for a 5.7 (normally for toyota swaps i do the harness and sensors are all the same and you just need to switch out the ecu) if you have a boat with the right ecu sitting around in the shop swap it out and see how it runs. betcha it fixes it if not try also swaping the maf (well not sure if merc uses maf or map if map then your not gonna need to swap sensors)
joe

 

[SuperNova]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

I hate to say it, but most of this is wrong info. with the possible exception of the ECU being different. The real culprit of the lean issue is the fuel injectors. The 5.7 uses larger injectors. The ECU is part of the issue, but the injectors will do more to solve it than the ECU will. Been there, done that .....several times.

 

[Don S]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

I hate to say it, but most of this is wrong info. with the possible exception of the ECU being different. The real culprit of the lean issue is the fuel injectors. The 5.7 uses larger injectors. The ECU is part of the issue, but the injectors will do more to solve it than the ECU will. Been there, done that .....several times.

Kind of amazing how the 5.0Gi and the 5.7GSi in 1998 (BY model) both used the same part numbers for the injector kits, but had different PN's for the ECM's. So I would have to assume that the injectors were not larger. Didn't even see an option for injector kit PN 3857398 offering large or small.

The ECM is what deterimines how many MS the injector will fire for and how much fuel is delivered.

 

[Aloysius]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

Kind of amazing how the 5.0Gi and the 5.7GSi in 1998 (BY model) both used the same part numbers for the injector kits, but had different PN's for the ECM's. So I would have to assume that the injectors were not larger. Didn't even see an option for injector kit PN 3857398 offering large or small.

The ECM is what deterimines how many MS the injector will fire for and how much fuel is delivered.

That's exactly it. Essentially on a boat the ECM controls only 2 functions..spark advance and pulse width on the injectors. With no O2 feedback, it works off a multidimensional MAP with inputs from the TPS, rpms, the "other" MAP, and temperatures. What's the term..speed density?

 

[SuperNova]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

Kind of amazing how the 5.0Gi and the 5.7GSi in 1998 (BY model) both used the same part numbers for the injector kits, but had different PN's for the ECM's. So I would have to assume that the injectors were not larger. Didn't even see an option for injector kit PN 3857398 offering large or small.

The ECM is what deterimines how many MS the injector will fire for and how much fuel is delivered.

Can't argue with you an part numbers etc. What I CAN state, based on direct, been there, done that experience, is that the injectors are what made the engine run right, NOT the ECMs. Now I know you are the factory-trained Guru here and have access to all that factory info, but I seem to remember having difficulty figuring out what the problem was, even after the "correct" ECM didn't fix the lean running. Unfortunately, it's been 10 years and a couple of shop changes since then...so no better info than my own failing memory. Sorry.

Speaking of Guru...Don I would've thought you'd know better than to assume ANYTHING by now..lol

Edit: Did some more research (I googled it) and came up with pretty much all the same solution...injectors. Seems the 305 injectors are around 40 lb/hr units and the 350 requires around 55 lb/hr units....but I could still be wrong. All I know is mine ran right when I was done...

 

[Don S]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

Can't argue with you an part numbers etc. What I CAN state, based on direct, been there, done that experience, is that the injectors are what made the engine run right, NOT the ECMs.

It may very well be it took changing the injectors and the ECM to cover up what your REAL problem was, have no idea. But the fact remains. The OEM injectors are the same, only the ECM changes.

Speaking of Guru...Don I would've thought you'd know better than to assume ANYTHING by now..lol

Are you kidding, on forums, you have to assume a lot of things a lot of the time, mostly because you NEVER have access to all the facts.

 

[SuperNova]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

It may very well be it took changing the injectors and the ECM to cover up what your REAL problem was, have no idea. But the fact remains. The OEM injectors are the same, only the ECM changes.

Nah, this was on a few different swaps....common denominator was the injectors...couldn't make 305 injectors run in a 350...even with a custom programmed chip.....got to the point where I don't even fool with the ECM anymore, I just change the injectors. In fact, I just pulled a 350 out of a converted truck where they didn't change the injectors, just the ecm and that engine was burnt up internally from having been run too lean for a year or two. Blew the head gasket and melted the crowns of a couple pistons a little. I didn't do the original swap, I just fixed it after it fried.....new 350 and correct injectors. Guy never understood why it didn't run quite right. Now he's thrilled.

How many of these swaps have you done, Don?

 

[Don S]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

How many of these swaps have you done, Don?

Only 1. Changed the ECM during the upgrade, and as far as I know the boat is still running fine.

 

[SuperNova]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

Well, I see what you mean as far as the part numbers, though it seems odd to me that they are labeling the 305 as a V6. The listings I'm finding list the injectors for 305-V6 and 350-V8...must be a typo.

Anyhow from what I found of my own notes, if you look at the top of the injectors, they should be color-coded. Geen and white are 40 lb/hr 305 injectors. Orange and black are 55 lb/hr 350 injectors.

But you should probably listen to Don and go for the ECM change first, he has access to better information.

 

[Aloysius]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

40 lbs/hr is about 6 gallons. Therefor, they should be adequate for 45-50 gallons per hour for the engine. I'll bet the bigger injectors are simply a bandaid to cover up the fact that the 305 injector pulse width is inadequate for a 350. The bigger injectors flow more per hour, so obviously they flow more per millisecond of opening, and THAT is what the PROM controls.

 

[SuperNova]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

40 lbs/hr is about 6 gallons. Therefor, they should be adequate for 45-50 gallons per hour for the engine. I'll bet the bigger injectors are simply a bandaid to cover up the fact that the 305 injector pulse width is inadequate for a 350. The bigger injectors flow more per hour, so obviously they flow more per millisecond of opening, and THAT is what the PROM controls.

You're sort of right, but you are looking at it backwards. You need the bigger injectors to keep the pulse-width short. There is a NORMAL injector opening time that applies across the board for ALL engines....say 4 ms. at idle. You then size the injectors to the engine, this gives you a rough starting point, and the ECM makes small adjustments to the time interval to fine tune the fuel delivery. I've been to countless hours of training on this stuff. You can believe what you want, but I am telling you how it works. I can plug in to ANY engine and expect to see certain parameters which are considered normal operating parameters NO MATTER of brand or engine size....and fuel injector "on" time is one of those constants...it doesn't vary by engine make or size.
This is due to the simple fact that engine mechanical timing doesn't change and certain events have to happen within certain time windows and this includes your injector pulses. You just don't have the time to double your injector pulse-width. You might get away with it at idle, but you'll certainly lean out at a higher rpm where there are even smaller time windows. As I've said before...been there, done that......multiple times. And I am telling you in no uncertain terms....the injectors fix the lean issue, not the ECM. But since this is not my project or problem, I am willing to see how it plays out doing it Don's way.

 

[wire2]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

....
the 5.0 ECU cant tell that now it is feeding 5.7 liters of air for every complete cylce of the pistons.
....

Physics dictate that a naturally aspirated engine will never move a volume of air equal to the mechanical displacement. The throttle plates, runner size, valve restriction will limit flow at all speeds. Even at wot, there will be less than 1 atm in the combustion chamber when the intake valve closes. MAP or MAF sensors are there to monitor the changes.

However, I will concede that, obviously, a 5.7 will move more air than a 5.0.

 

[rodbolt]

Re: 1998 volvo 5.0 changed to 5.7, enough fuel to throttle body?

this system doesnt use MAF, it simply uses a MAP.
all the MAP does on that system is give the ECU information on engine load and baro pressure at key on.
dunno about this guys issue, the only upgrades from the 5.0 to the 5.7 I ever did we used the 5.7 injector part numbers,TB kit and the 5.7 ECU.
typically marine ECM's dont monitor the baro pressure they lock it in at the start of the key on cycle and use that as the standard for the rest of that cycle.
no need to constantly measure baro as most boats dont change altitude much in a single key on cycle.
its all about keeping the A/F mix at about 14.7/1.its also why motors now have pre and post catalyst O2 sensors.
while marine ECM's are dinosaurs compared to the automotive world they are gaining fast.
its ALL about moving air.
thats all an articulated rod internal combustion engine is, its an air pump.
so if the injectors and ECM are set up to provide the 14.7/1 air/f mix for moving a theoretical 5.0L of air and suddenly without anyother changes you move the theoretical 5.7L of air you just altered the air to fuel ratio towards the lean side.
remember,MEFI1,2 and 3 cannot and did not monitor MAF just intake pressure to sense engine load.
so the injectors size,the fuel pressure and the airflow through a known throttle into a known cubic liter displacement are all mapped into an ECU.
the design engineers were pretty good. but yes the basic injector on time is a design function of piston travel time,fuel rail pressure and injector size.
its also why the Z3.3L yamaha engines use 1100 PSI on the rail.
we simply dont have enough time at 50 PSI to move that amount of fuel,ignite it and get it out in about 1.5" of piston travel.
at 5000+ RPM.
look up the parts for both the WT model 5.0 and 5.7.
if the injector part numbers are the same then they are the same injector.
think of the TBI as a precision fuel sprayer.
also pay attenion to the spray pattern.
dirty injector filters and nozzles can make it dribble instead of a nice cone spray.
that motor doesnt like dribbles.