Sniper EFI for boat.

[DaveH]

only upon key off/on for most marine and aftermarket systems as they take their atmospheric pressure reading from the MAP sensor at key on. They can't change on the fly.

good efi systems have a dedicated baro sensor.

 

[Shlbyntro]

No MAF because cams with bigger overlap can cause air reversion which translates to bucking or inconsistent power delivery at lower RPM and load. If you’ve ever driven a cammed vehicle with a MAF you have likely felt it buck.

Also a MAF needs to be placed in a long straight tube because smooth airflow is key to it functioning properly. This is the biggest hurdle.

MAF engines are actually way more responsive to cam swaps than MAP/speed density engines. MAP engines require tuning with cam changes. MAF is way more forgiving and will run just fine without the need to tune. That's why the 89-93 5.0 Mustangs were more desirable than the 86-88 5.0 Mustangs with hotrodders. That's when Ford switched from MAP to MAF on the Mustang

 

[Shlbyntro]

good efi systems have a dedicated baro sensor.

almost all marine fi engines do not. I'm willing to bet neither does the sniper. yes, most modern cars do now at this point and I'm sure the higher end aftermarket stuff does too.

 

[LargeOrangeFont]

MAF engines are actually way more responsive to cam swaps than MAP/speed density engines. MAP engines require tuning with cam changes. MAF is way more forgiving and will run just fine without the need to tune. That's why the 89-93 5.0 Mustangs were more desirable than the 86-88 5.0 Mustangs with more popular with hotrodders. That's when Ford switched from MAP to MAF on the Mustang

On the old Ford stuff yes it’s quick, I can tune one of those in about 30 mins on the road. I think this is because the sampling is more coarse. Its been about 5 years since I’ve been in one playing with one tuning a 347. I’m going to have to do it again soon for my friends 363.

On a lot of the modern GM stuff the MAF turning is more involved than the SD tuning because the car can use both MAF and SD. Mainly because of the air reversion I spoke of, MAF tuning/scaling and VE changes are needed for a cam.

The Holley stuff is way easier to tune than the factory ECU in a modern car.

 

[Shlbyntro]

On the old Ford stuff yes it’s quick, I can tune one of those in about 30 mins on the road. On a lot of the modern GM stuff the MAF turning is more involved than the SD tuning because the car can use both MAF and SD. Mainly because of the air reversion I spoke of, MAF tuning/scaling and VE changes are needed for a cam.

The Holley stuff is way easier to tune than the factory ECU in a modern car.

well then that a disagreement between your MAF and your MAP, not a problem with the MAF

 

[LargeOrangeFont]

well then that a disagreement between your MAF and your MAP, not a problem with the MAF

The switchover is what the OE intended and is tunable.. which is nice because you don’t have to have to buck your way across a parking lot with that choppy cam you can just run speed density, at just off idle, and run MAF after you get going.

Or you can turn MAF off my RX7 is full Speed Density in open loop. It does not even run 02 sensors.

MAP, air temp, water temp, TPS and Idle air control are the only sensors on the engine.

 

[monkeyswrench]

The switchover is what thenOE intended and is tunable.. which is nice because you don’t have to have to buck your way across a parking lot with that choppy cam you can just run speed density, at just off idle, and run MAF after you get going.

A guy up did this with a prerunner 1500 pickup. About the only NA 6.0 I thought sounded pretty cool. It was SD until 1500-1700rpm. I thought it was a pretty interesting workaround.

 

[77charger]

I wanted to go sniper route in my old carb 350 mag but have also been readin more negatives with it. These are cars too I know boat would have trouble with 02 sensor location.

Reading this is making me stick with carb. Like said they are simple and work. IMO they are a if it’s working don’t fuck with it or it will begin to act up.

Another issue going to efi is modifying rest of fuel system especially with dual tanks adding return lines high pressure pump new filters and hose. Yeh my carb is sounding great

 

[Nanu/Nanu]

This has been a great thread so far @Rajobigguy. Im not a carburetor guru but for me i live in a small remote town so for me to wrangle a good tuner for a vehicle would be tough let a lone for a boat. So i just use the resources Edelbrock provides for proper jetting. Honestly a lot of these carb companies have done tons of research over the years and seriously you need only a Phillips and flathead screwdriver and and torx bit to tune them. A good carb guy can get it super dialed for sure, but you can definitely get satisfactory results on your own going by the box recommendations and making small changes one trip at a time.

I personally would consider the switch if there was a company who literally offered the whole shebang for a marine application headers, intake, throttle body and computer/wiring harness but i dont think the industry is there yet.

Im a lake Powell boater and a simpleton. So if my boat is running crummy i can make simple changes on the water. I personally dont want to be worried about having cell service to call someone to make adjustments or come up with ideas outside the box.

If i could have it my way and money wasn't an issue i would just swap to an EFI motor.

Everyones situation is different. But the feedback here has been awesome from both sides.

I guess what it comes down to is figuring out if the juice is worth the squeeze to alter a good motor or if you would be better off just waiting for a motor to give up there ghost and just go with an EFI motor.

Seriously this is the basis of performance boating!

i thank everyone for their input as i have even pondered some points brought up here from the EFI side.

 

[Racey]

only upon key off/on for most marine and aftermarket systems as they take their atmospheric pressure reading from the MAP sensor at key on. They can't change on the fly.

You can't really change altitude between the course of a normal key on/off in a marine application so it's irrelevant from a tuning standpoint pragmatically.

Also Baro compensation is (mostly) limited to exhaust scavenging, as inlet pressure readings are absolute. They have a greater effect on turbo charged systems where exhaust delta p can have a great effect on turbo efficiency.

It's definitely a nice feature to have, but not a make or break in a marine environment.

Now in a car, different story.

 

[LargeOrangeFont]

I wanted to go sniper route in my old carb 350 mag but have also been readin more negatives with it. These are cars too I know boat would have trouble with 02 sensor location.

Reading this is making me stick with carb. Like said they are simple and work. IMO they are a if it’s working don’t fuck with it or it will begin to act up.

Another issue going to efi is modifying rest of fuel system especially with dual tanks adding return lines high pressure pump new filters and hose. Yeh my carb is sounding great

The high pressure fuel pump deal is pretty easy to solve with a small surge tank. That makes it pretty simple.

 

[Bigbore500r]

I wanted to go sniper route in my old carb 350 mag but have also been readin more negatives with it. These are cars too I know boat would have trouble with 02 sensor location.

Reading this is making me stick with carb. Like said they are simple and work. IMO they are a if it’s working don’t fuck with it or it will begin to act up.

Another issue going to efi is modifying rest of fuel system especially with dual tanks adding return lines high pressure pump new filters and hose. Yeh my carb is sounding great

The ROI converting your 5.7 carb motor to EFI in a boat is pretty dismal….I agree, stick to a carb and spend some time to dial it in 100%.

Adding a wide band O2 isn’t a bad idea, you can gather some data about how it’s running at idle, getting on plane, cruise, WOT etc and then make some tweaks to get jetting optimal. Kits are available for $300, you just have to figure out how / where your gonna add the 02 bung. That, combined with a vacuum gauge, will reveal a lot and give you the power to get your carb dialed easily.

 

[wet hull]

As stated earlier in this thread I did go from carb to Holley HP multiport injection system. It was not easy, it was not cheap but with it dialed in now I could never go back. Luckily my boat, mechanic and Brian Macey are all in Havasu otherwise it would have been even harder. The pics below show the system as well as my O2 bung extender Brian recommended to keep moisture off sensor, 2 years now and zero moisture on sensor and I run in closed loop. The hardest part of this project was getting all the correct parts such as injectors, distributor, fuel system. Once all this was acquired it was plug and play.

Once system was in from Flat Tops, pressure tested and ran on hose for awhile to allow cpu to start making adjustments in was lake time. I met Brian at launch ramp, he got on boat and we started the tune. He is the nicest guy you will ever meet and his knowledge of tuning is beyond nerd level!

He plugs his laptop in, I fire the boat and he starts on trailer. Immediately making changes. He never looks up from his laptop through entire process. You can already hear a difference at idle. We then go through each rpm and he adjust. Start at 1000,2000,3000,4000,5000. We do this 2 times. Boat would sound great then fall on its ass then back to great. Very weird to experience in person. Finally we go wide open and he does final adjustments to make sure we are not lean or rich, locks it in and we are done. Took about 30 min. He then went into software and put safety parameters in place. Oil psi, voltage, temp and I believe MAP. The boat will go into limp mode if these are hit but allow me to go up to 1500 rpm if needed to get back to trailer. This is the most important part of the whole system. It worked following season when oil pressure dropped. Kept me from grenading my engine

To wrap up, bad ass system and worth the headache to get it done right. Having a expert tuner dial it in is a absolute. Finally I bought the dash monitor that allows me to see everything in real time.

 

[Jonas Grumby]

And Brian Macy is a very well respected and knowledgeable guy in EFI, In fact he taught the EFI Advanced class when i went through it probably 15 years ago. If he can't get it to work......

Those cheap boxes have fundamental software issues. The software is the most important part of the box, Electronics have become ubiquitous, so the actual chips, drivers, and ADCs are rarely problematic. Most issues are the result of bad software.

Brian Macy sells and recommends all the Holly efi stuff.

 

[farmo83]

As someone who is 2 years into trying to get my tune right don't do this. Leave a carberator on it and roll around.

 

[LargeOrangeFont]

As stated earlier in this thread I did go from carb to Holley HP multiport injection system. It was not easy, it was not cheap but with it dialed in now I could never go back. Luckily my boat, mechanic and Brian Macey are all in Havasu otherwise it would have been even harder. The pics below show the system as well as my O2 bung extender Brian recommended to keep moisture off sensor, 2 years now and zero moisture on sensor and I run in closed loop. The hardest part of this project was getting all the correct parts such as injectors, distributor, fuel system. Once all this was acquired it was plug and play.

Once system was in from Flat Tops, pressure tested and ran on hose for awhile to allow cpu to start making adjustments in was lake time. I met Brian at launch ramp, he got on boat and we started the tune. He is the nicest guy you will ever meet and his knowledge of tuning is beyond nerd level!

He plugs his laptop in, I fire the boat and he starts on trailer. Immediately making changes. He never looks up from his laptop through entire process. You can already hear a difference at idle. We then go through each rpm and he adjust. Start at 1000,2000,3000,4000,5000. We do this 2 times. Boat would sound great then fall on its ass then back to great. Very weird to experience in person. Finally we go wide open and he does final adjustments to make sure we are not lean or rich, locks it in and we are done. Took about 30 min. He then went into software and put safety parameters in place. Oil psi, voltage, temp and I believe MAP. The boat will go into limp mode if these are hit but allow me to go up to 1500 rpm if needed to get back to trailer. This is the most important part of the whole system. It worked following season when oil pressure dropped. Kept me from grenading my engine

To wrap up, bad ass system and worth the headache to get it done right. Having a expert tuner dial it in is a absolute. Finally I bought the dash monitor that allows me to see everything in real time. View attachment 1252332 View attachment 1252333

That looks clean!!

 

[Racey]

Brian Macy sells and recommends all the Holly efi stuff.

I think there is a pretty big difference between the Sniper and the Terminator/Dominator

 

[DaveH]

As someone who is 2 years into trying to get my tune right don't do this. Leave a carberator on it and roll around.

two years? something is way wrong. If you go tune and it seem right, only to come back around and now its "off"......you are going in circles chasing an issue that has nothing to do with the computer and/or tune.

 

[Racey]

two years? something is way wrong. If you go tune and it seem right, only to come back around and now its "off"......you are going in circles chasing an issue that has nothing to do with the computer and/or tune.

Well maybe, it's a holley

 

[Blackmagic94]

So as far as tuning the sniper setup, what’s involved with that. Can you manipulate the settings with the handheld device that comes with it or do you need a laptop with Holley software?

Either can be done

 

[DaveH]

Well maybe, it's a holley

BOOM

 

[kurtis500]

I ran the Holley EFi multi-port fuel injection on my 468. I took it off after a few years. The comment to have a good set of oars is about right.
I had issues with the location of the O2 sensor. I put it in the farthest front of the exhaust and still took out a sensor every year or so. You could never predict when it goes out and keeping a spare isnt a solution. When it goes down on the water you are dead in the water.

I put a well tuned 850 dp back on and its all good again.

 

[mattyc]

This has been a great thread, lots of good thoughts and experience. My experience with efi is solely diagnosing and repairing existing systems primarily on OEMs.

When someone tunes / adjusts / sets up an efi system in the boat, with no o2 sensor, a/f meter or egts to provide a closed loop feedback, what are they using to measure or "prove out" their adjustments?

I imagine the efi software requires basic information like cubic inches, expected volumetric efficiency? Does it give you a theoretical window for proper air / fuel mix? I'd really love to learn and get some experience in it. Maybe when I get some free time

 

[wet hull]

I ran the Holley EFi multi-port fuel injection on my 468. I took it off after a few years. The comment to have a good set of oars is about right.
I had issues with the location of the O2 sensor. I put it in the farthest front of the exhaust and still took out a sensor every year or so. You could never predict when it goes out and keeping a spare isnt a solution. When it goes down on the water you are dead in the water.

I put a well tuned 850 dp back on and its all good again.

That's a bummer it didn't work out. Brain loaded my tune as a backup into my software. I can use dash monitor if O2 sensor fails, turn sensor off and put system into open loop with that tune. Haven't needed it yet luckily. This would not he possible without the dash monitor.

 

[Jonas Grumby]

I think there is a pretty big difference between the Sniper and the Terminator/Dominator

Ok, that’s my question, sniper sucks, HP is ok?

 

[Racey]

Ok, that’s my question, sniper sucks, HP is ok?

Yes, but imo there are far better values on the market than any of their products.

You will definitely hear lots of opinions from everyone that uses whatever product they sell.

It's a shame they discontinued the AEM boxes when Holley bought them out because they were about 20x more advanced than the Holley product.

I know many people running Holley boxes, having no issues. But also know many people running carbs and distributors with no issues either.

My opinion on fuel injection is I want an advanced product that has lots of tuning flexibility, advanced software, and excellent data analysis.

These are things that you can't fully understand until you have used a lot of different products. You start to realize how important certain features are that are lacking in in some products.

Bottom line, anyone deciding to do EFI, use a system that YOU have access to GOOD support on.

They are all worthless if you can't get any technical help on.

 

[hman442]

I agree that there is nothing wrong with a carburetor that is taken care of (meaning the gas). Aa far as EFI, the Indmar 350 Chevs seem to work well and be pretty trouble free. Is there any way to add that type of system, or would s guy just have to gather up every piece and put it together ?

 

[kurtis500]

That's a bummer it didn't work out. Brain loaded my tune as a backup into my software. I can use dash monitor if O2 sensor fails, turn sensor off and put system into open loop with that tune. Haven't needed it yet luckily. This would not he possible without the dash monitor.

I did switch between open and closed loop to avoid the possibility of the O2 sensor leaving me dead once again. The EFI setup on modern boat motors is the way to go. I just think converting and old LS6 big block to EFi trying to use existing exhauts and etc. was too much to be consistent. When the parts are all specifically built to be robust in a boat its the way to go without any question. After spending $5000 on the system I was offered $4200 a few years later and quickly sold it. It had the electronic distributor, knock sensors and every bell and whistle possible at the time. Now it runs 95% as good with a well tuned carb but it will never match the EFI when it was running perfect. With 11.25:1 I always liked the comfort of knowing any detonation could be picked up and the distributor retarded while Im driving along and dont notice a thing.

 

[Jonas Grumby]

Yes, but imo there are far better values on the market than any of their products.

You will definitely hear lots of opinions from everyone that uses whatever product they sell.

It's a shame they discontinued the AEM boxes when Holley bought them out because they were about 20x more advanced than the Holley product.

I know many people running Holley boxes, having no issues. But also know many people running carbs and distributors with no issues either.

My opinion on fuel injection is I want an advanced product that has lots of tuning flexibility, advanced software, and excellent data analysis.

These are things that you can't fully understand until you have used a lot of different products. You start to realize how important certain features are that are lacking in in some products.

Bottom line, anyone deciding to do EFI, use a system that YOU have access to GOOD support on.

They are all worthless if you can't get any technical help on.

I’m just looking to replace the MEFI3 and get rid of the soot on the transom, they way it was explained to me was the mefi3 doesn’t cut fuel right away as you throttle back, it waits till the rpm’s drop, thus the soot

 

[Racey]

I’m just looking to replace the MEFI3 and get rid of the soot on the transom, they way it was explained to me was the mefi3 doesn’t cut fuel right away as you throttle back, it waits till the rpm’s drop, thus the soot

It's been a long time since i've been in a MEFI 3 computer, but i'm pretty sure it has a full 3D fuel table for 1Bar (Naturally aspirated), so it should have the ability to pull fuel when the vacuum increases in the manifold, not just the RPM. IIRC the main drawback to the MEFI 3 computer was that on anything forced induction you had a single dimensional fuel modifier, so fuel tuning was global across any rpm band as a multiplier based on how much boost you were running. So they never work great on forced induction, they can be made to work, but it's not ideal, and usually results in having to tune fat to stay safe.

Like i said it's been a long time so i may be wrong there.

 

[Jonas Grumby]

It's been a long time since i've been in a MEFI 3 computer, but i'm pretty sure it has a full 3D fuel table for 1Bar (Naturally aspirated), so it should have the ability to pull fuel when the vacuum increases in the manifold, not just the RPM. IIRC the main drawback to the MEFI 3 computer was that on anything forced induction you had a single dimensional fuel modifier, so fuel tuning was global across any rpm band as a multiplier based on how much boost you were running. So they never work great on forced induction, they can be made to work, but it's not ideal, and usually results in having to tune fat to stay safe.

Like i said it's been a long time so i may be wrong there.

Ya it’s running my quadrotor. And it’s fat

 

[Racey]

Ya it’s running my quadrotor. And it’s fat

Yep Mefi3 and supercharged, you would definitely benefit from a more modern system, absolutely, no doubt about it.

 

[johnnyC]

if you look at hot rod tv engine masters has an epsode on the sniper system ...... pretty informative with data they provide , but it was limited, if you havent watched this program you should they dispell many mthys about performance gains

 

[Tyeegs]

I have Holley hp on the LS7 in my Lund 1950 IO. I tuned it closed loop. Run it open loop and check occasionally. Never looked at spark plugs while tuning. Ran great for two seasons. Pulled the engine to switch the cam from stock to 114 deg lsa 120 duration both lobes. Discovered major carbon buildup on pistons and cylinder heads. Wet IMCO exhaust with O2 sensor in spacer between lower and upper manifold. Has anyone else experienced misleading lean reading by O2 sensor in these marine applications thereby tuning unwittingly rich? BTW I have two sensors that I swap out. They read the same way.

 

[DaveH]

I have Holley hp on the LS7 in my Lund 1950 IO. I tuned it closed loop. Run it open loop and check occasionally. Never looked at spark plugs while tuning. Ran great for two seasons. Pulled the engine to switch the cam from stock to 114 deg lsa 120 duration both lobes. Discovered major carbon buildup on pistons and cylinder heads. Wet IMCO exhaust with O2 sensor in spacer between lower and upper manifold. Has anyone else experienced misleading lean reading by O2 sensor in these marine applications thereby tuning unwittingly rich? BTW I have two sensors that I swap out. They read the same way.

02 sensors can be very misleading. bumpy cams, water, exhaust leaks and so forth will rennder less then entirely accurate readings. furthermore it seems like the common sensors just dont last like they did in years past.

due diligence of checking other parameters...things like reading plugs and so forth are required to get the tune correct, and why self learning systems are always a bad idea

 

[bonesfab]

As some tuners say. Numbers are just numbers. You have to give the engine what it actually wants. And they are all different. They actually have more in common with females then we know.

 

[DarkHorseRacing]

Just be happy it was rich instead of lean.

 

[monkeyswrench]

As some tuners say. Numbers are just numbers. You have to give the engine what it actually wants. And they are all different. They actually have more in common with females then we know.

You may get in big trouble if a female pisses you off, and you leave her in the garage for a week...
I prefer motors

 

[bonesfab]

You may get in big trouble if a female pisses you off, and you leave her in the garage for a week...
I prefer motors

and I can have as many as I want and one won't take half.

 

[Bigbore500r]

and I can have as many as I want and one won't take half.

But just like a chick . . . running them hard without lube can cause excessive wear

 

[monkeyswrench]

But just like a chick . . . running them hard without lube can cause excessive wear

I ain't re-ringing, sleeving...but maybe line boring...a chick

 

[Tyeegs]

Do any tuners out there have a rule of thumb like “tune wet systems two points lean to get close newbie” or “she’s lean down low and rich up top”

 

[DaveH]

Do any tuners out there have a rule of thumb like “tune wet systems two points lean to get close newbie” or “she’s lean down low and rich up top”

rule #1
TURN OFF self tune or closed loop capabilities

rule #2
take what the 02 sensor says with a grain of salt

rule #3
look at the MAP you are creating graphically, nut numerically. the graph should be smooth and progressive. if the 02 sensor is leading you towards something different, see rule #2.

rule #4
once you have attained a sensible VE graph, look for other indicators to verify the tune. plug color, sooty transom, sluggish acceleration, etc etc etc. all indicators of an overly rich tune regardless of what the 02 sensor says. back to rule #2.

 

[Tyeegs]

After re-thinking the problem, I've removed the engine cover and ebay is helping me with a dry exhaust for the odd cylinder side of the engine. Plan to tune with mufflered dry exhaust and then compare after transitioning back to wet exhaust. Tough to compare apples to apples with prior tune as I've changed the LS7 cam to 114LSA aftermarket to pick up mid-range torque. Got the engine back from my builder last week after he removed the excessive carbon build up and ball honed the cylinders. Likewise it'll be a lot easier to run the engine at a few different load conditions, quickly shut down and read plugs to follow rules 2-4.

 

[ElectroNautical]

MAF engines are actually way more responsive to cam swaps than MAP/speed density engines. MAP engines require tuning with cam changes. MAF is way more forgiving and will run just fine without the need to tune. That's why the 89-93 5.0 Mustangs were more desirable than the 86-88 5.0 Mustangs with hotrodders. That's when Ford switched from MAP to MAF on the Mustang

No...the Speed/Density systems used in MEFI (Mercruiser, Volvo Penta, Indmar, etc.) are completely insensitive to cam changes, intake manifold upgrades, etc because they electronically 'filter' the signal from the manifold pressure sensor such that the resulting input to the EFI controller matches the fuel flow that would be produced by venturi effect in a 'perfectly designed' carbuerator. In theory (and in practice I find) this system works flawlessly. Raylar Engineering (who does more of this than anyone) explains this on their website...

 

[Bigbore500r]

No...the Speed/Density systems used in MEFI (Mercruiser, Volvo Penta, Indmar, etc.) are completely insensitive to cam changes, intake manifold upgrades, etc because they electronically 'filter' the signal from the manifold pressure sensor such that the resulting input to the EFI controller matches the fuel flow that would be produced by venturi effect in a 'perfectly designed' carbuerator. In theory (and in practice I find) this system works flawlessly. Raylar Engineering (who does more of this than anyone) explains this on their website...

Welcome to RDP!

My 2 cents . . .

In that attachment, Raylar is basically stating that they modify the fueling needs of the motor by changing the fuel pressure. They are tuning the motor - but It's an archaic way of making fueling adjustment, and it doesn't account for how the modified engine's VE changes throughout its rev range under different loads.
Which, is probably why Raylar upgraded 496's have a reputation for being time bombs.......

They absolutely need to be tuned to adjust the fueling and timing appropriately for the new camshaft. The lack of a MAF sensor means the motor only has the MAP (baro) sensor to rely on, and a new cam / cam+head combo can drastically alter the readings the sensor is picking up and applying to the VE table in the ECM.

The ECM does not self regulate fueling like a carb / venturi - it just applies the MAP readings against the existing fueling tables and you get what you get, as there is no way for the computer to know if its rich, lean, etc - It can't measure incoming airflow (MAF) and has no 02 sensor. Once you change the variables, any known results or safety margin that the mfg had built into designing that tune are out the window.

 

[ElectroNautical]

On the old Ford stuff yes it’s quick, I can tune one of those in about 30 mins on the road. I think this is because the sampling is more coarse. Its been about 5 years since I’ve been in one playing with one tuning a 347. I’m going to have to do it again soon for my friends 363.

On a lot of the modern GM stuff the MAF turning is more involved than the SD tuning because the car can use both MAF and SD. Mainly because of the air reversion I spoke of, MAF tuning/scaling and VE changes are needed for a cam.

The Holley stuff is way easier to tune than the factory ECU in a modern car.

Exactly right. I'll go a step further and say that any properly designed Speed-Density based system (MEFI or similar) is easy to tune because they don't really need tuning.

 

[ElectroNautical]

Welcome to RDP!

My 2 cents . . .

In that attachment, Raylar is basically stating that they modify the fueling needs of the motor by changing the fuel pressure. They are tuning the motor - but It's an archaic way of making fueling adjustment, and it doesn't account for how the modified engine's VE changes throughout its rev range under different loads.
Which, is probably why Raylar upgraded 496's have a reputation for being time bombs.......

They absolutely need to be tuned to adjust the fueling and timing appropriately for the new camshaft. The lack of a MAF sensor means the motor only has the MAP (baro) sensor to rely on, and a new cam / cam+head combo can drastically alter the readings the sensor is picking up and applying to the VE table in the ECM.

The ECM does not self regulate fueling like a carb / venturi - it just applies the MAP readings against the existing fueling tables and you get what you get, as there is no way for the computer to know if its rich, lean, etc - It can't measure incoming airflow (MAF) and has no 02 sensor. Once you change the variables, any known results or safety margin that the mfg had built into designing that tune are out the window.

No, the only reason they are increasing the fuel pressure (specifically on the MEFI Vortec 8.1L) is to flow more fuel to their 'built' versions of these motors. All of the marine Vortec 8100's came with the fuel pressure set at 42psi while the smaller GM V8's (which make more HP-per-litre displacement) are set at 60. It's a trivial change and not any kind of 'tuning', as it only requires changing the pressure sensor on the fuel rail...

 

[ElectroNautical]

Welcome to RDP!

My 2 cents . . .

--snip---
Which, is probably why Raylar upgraded 496's have a reputation for being time bombs.......

--snip--

I've seen seven Raylar 8100's over the past 10 years (and done two of those myself, including one I owned -- a 2003 Volvo Penta). The only one that ever had problems was the one where a bonehead decided to 'go for it' using the stock pistons. It was quite satisfying in that case to say "I told you so"...

That said, this is the first I've heard of a less than excellent reputation for the Raylar modified 8100...care to share your experience?

 

[Bigbore500r]

No, the only reason they are increasing the fuel pressure (specifically on the MEFI Vortec 8.1L) is to flow more fuel to their 'built' versions of these motors. All of the marine Vortec 8100's came with the fuel pressure set at 42psi while the smaller GM V8's (which make more HP-per-litre displacement) are set at 60. It's a trivial change and not any kind of 'tuning', as it only requires changing the pressure sensor on the fuel rail...

....which changes the fuel being delivered to the motor.......to add fuel ......for change in VE and additional HP being produced.

So they are adding fuel via a universal fuel pressure change, in lieu of tuning the motor and changing the fueling tables to what it needs at different spots in the VE tables.

I stand by my original post - lol