Hello,

I am trying to help my brother-in-law with a supercharged (SC) L61 in a boat. I am sorry I need to use your forum, but I could use some help from some L61 experts, and I think I found some here.

This engine was fully functional with full standalone ECU and tuned appropriately. One day the inside bits figured they wanted to see the light of day, and they broke free by going straight through the crank case. They were very cleaver bits of metal as they exploited a fuel pump that cavitates around 60 psi. A Bosch 909 or 910 has been installed to stop any further escapees. Some mechanics were hired to fully dress a new factor crate L61 with all of the original parts. This was apparently done. The fellow how owns the boat was certain all of the components were installed on the new engine to spec for the SC.

Problem: The engine seems to run quite well except it wont start once warm. To get it to start it was found quick flicks of the ignition seemed to get it to fire. This is not always reliable but one in 20 tries might get it to fire up. The other thing is wait.... Waiting several minutes can get it to start too. Two out of five times I was able to get the engine to start when the laptop attached to the ECU was not displaying "Cold Start". Every other time the engine has to have this "Cold Start" enabled. To get it to start without "Cold-Start" I bumped the idle stepper up a few notches (from 7 to 9 and 7 - 11). The other three times I tried this it likely flooded the engine as there was an apparent unburnt fuel smell.

Before this gets out of control: I am looking to see if anyone has experienced:

• A SC L61 with a wrong MAP, Fuel Injectors, Throttle Body, Idle Stepper, Vacuum Configuration.
• Some help with a SC engine not starting a second time.
• Where the stepper position tends to be set and how?
• Knock in these engines with SC.

Warm Vs Hot
I figured heat soak may be an issue. This really doesn't look promising. Fuel lines are far away from any real source of heat (exhaust manifold). Exhaust manifold is in a water sleeve so, it is barely warm to the touch. The engine will start just fine at 18 C. It only reaches a temperature in the 70's C with one recorded peak of 80 C. We need to look into the thermostat or if one was even installed in the boat conversion but heat doesn't appear to be an issue.

Battery Volts
With a quick flick of the key starting the engine sometimes when it doesn't want to start, I figured battery issues etc. The data shows initial cranking volts drop to 9.6 but within 1/2 a second it reads 10.6 V. The engine seems to fire as low as 10.3 V in the limited data I have. I am not sure which coils or injectors are installed but maybe someone can comment on required voltage to coils?

Trying to keep the thinking to what has changed, I am back to the engine and what was brought over from the old engine.

Manifold Pressure Sensor
I have read on here there are some options. With the current engine and supercharger, the MAP sensor reads the following values. I am curios if anyone can comment on whether they look about right or if this may be a sign of the wrong MAP sensor being installed. The idle and 2,500 RPM numbers are similar to where I have seen some N/A engines running so it seems okay... but at the same time I expected the SC to be moving some air.
Idle = 29kPa, 2,500 RPM = 56 kPa, 4,500 RPM = 168 kPa = 10.3 PSI.

Vacuum Issues
There are a few unused ports since there is no brake assist etc. The actuator to, what I assume is, the waste gate moves etc. I would assume this is not an issue but there may be a system that I am not thinking of here. I would assume the fuel pressure regulator would be more noticeable if it were not getting the correct vacuum. This is an area I think could be checked, but I am not sure it would align with the starting issue.

Throttle Body (TB)
I am assume it is possible that the throttle body maybe the one supplied with the crate motor, if one comes with a crate motor. Again, I would assume there would be a much more noticeable issues if there was a different TB on here. This is where I am hoping some of you with some experience may have tried different versions of TB and let me know if the difference could be so subtle.

Idle Stepper
This is a concern. Do any of you know where your stepper is? There are times when the engine wont start and the stepper is in a different position for each attempted start. I don't see any reason for the position either manifold pressure, engine temp and air temp all can be very similar yet the stepper is in a different position.

Fuel Injectors
Now, I have to assume that bigger injectors were on the original motor and they were moved over or replaced. I can't see the engine running so well if the injectors are a different size. Assuming a 42 lbs/Hr injector was installed, and a factory injector was now being used would it only have a starting issue when warm? There is no Lambda sensor as the exhaust is in a water jacket so, no proper way to tell. Does anyone have experience with tuning the factory vs 42's and will either run the same map up to 5,000 RPM? I can't imagine it would start at all...

Spark Plugs
These are also specific to the super charger and are likely replaced.

Fuel
This is running high octane pump gas. It is not for racing. It is for fishing. The tune is set accordingly. The system has been checked for soft lines sucking shut with the new pump. This would also manifest in a different way than only on starts. Checked that the fuel line is not sucking shut in the fuel tank and that some sort of foam / screen is on it so it can't suck to a floor or wall etc. So, fuel just doesn't seem like it. Unless the system is rapidly siphoning dry... Anybody seen this? It is uncertain if the fuel system is running a scavenge pump and a main pressure pump. I have the guys looking into this. Also, it wouldn't explain why stabbing at the ignition would cause a start and cranking doesn't. Cranking for a long time at any temperature will not start.

• At this time the positioning of the stepper is suspect to me, not knowing its normal behaviour.
• What can be different on these L61's? Are there different heads with different flow etc?
• How do you identify the different throttle bodies?
• Would the engine run if any of the above were stock instead of the bumped-up version for the SC?

I programmed an analysis program for this unknown custom ECU. I have attached some screen captures I found interesting.

L61 SC Data Stepper Position


L61 SC Data No Start

Knock
I believe this is okay but maybe a person more experienced with smaller brand ECU's and super chargers could give an opinion. I assume the number of knock events is okay as it is while the throttle is moving and not at static throttle... There are knock counts into the 80's happening here. I am more accustomed to Bosch, Magnetti, MoTeC ECU's and I assume the filtering is much more intelligent as this seems high to me. The manual says that there can be knock events and only is a concern when the number gets "very high very fast" ... that is very subjective. Is this an issue? Yes, throttle calibrates to 300 in this ECU.

L61 SC Data Knock

 

one big thing here first off, our cars all run drive by wire throttle systems, so we dont have idle control motors as the ecm just alters the throttle blade position. very few people here run aftermarket computers, and almost all of them still run drive by wire, i think im about the only active person here with an ecotec on a stand alone with a mechanical throttle/idle control. our cars are also returnless fuel system (unless converted) and we dont have a fuel regulator on the rail, its in our fuel tank. that being said, it sounds like your combination may be closer to the j-body (cavalier/sunfire) gm supercharger kit than a cobalt, however none of that really matters for a starting issue.

first off, what engine management system is on it?

going through your list:

battery voltage- dropping to 9.6 volts seems like its pulling it down pretty far, thats getting into the area where you can end up with computer resets. if you are able to id try either a new battery, or just adding a second battery with jumper cables just for testing.

map sensor- the important thing here will be your map sensor reading with the engine not running, this tells you if its the correct sensor or not. it should read close to 100kpa at sea level. have a look at a weather report and it will tell you what the barometric pressure is, and thats roughly what the map sensor should read with the engine off. to add, i doubt this is wrong, you would have lots of engine running problems if it was, and there is no reason to remove the map sensor from the intake manifold during an engine swap.

vacuum issues- as long as all unused ports in the manifold are capped there shouldnt be issues. in this case, the fuel regulator should hook to the port on the intake manifold between the blower and fuel rail, and the top port on the bypass actuator should hook straight to the port near it on the blower. the brake booster port on the blower inlet should be plugged.

throttle body- its hard for us to know whats going on here. its possible its running one from a j-body, it could be ls1 based, really dont know. it really shouldnt matter much for a hot start issue.

idle stepper- really hard for us to know. my car has the stepper around 90 steps open for a hot start, about 160 steps open during cold start, but none of that really helps as we dont know how that translates to your computer. maybe 1 position is 10 steps, in which case 9-11 steps sounds ok, but we really dont know. what you can do is while cranking try feeding it a little throttle, if it all the sudden starts there isnt enough idle motor opening.

injectors- if they wernt the ones the boat was tuned for you would know. the stock l61 injectors are 28lb/hr, 42lb/hr are 33% larger, so it would essentially be 33% too little fuel and likely wouldnt even run when cold. you could always have a look at the plugs to confirm, if they are wrong they will show very lean. also you can post a pic of the fuel injectors, or part numbers and we could try to identify them.

spark plugs- make sure you have the correct plugs, lots of people toss in a 3/4" reach plug, these engines require a 1" reach plug. there arent many choices of a colder plug for these engines because of that. should be something like an ngk LTR-7ix-11 or an LTR-6ix-11.


there are a few things id recommend right off the start here. the first thing we need to figure out is whats stopping it from starting, spark, fuel, or both. when its in a no-start condition, try spraying something flammable in the throttle body (ether, flammable brake clean, etc) to see if it tries to start. if it starts we know its a fuel related issue, and if not i would pull the ignition cassette out and check for spark.

 

I agree with everything sharkey said except the plugs dont need to be -11. Ltr7ix has a smaller gap to start with and youll probably want to go smaller anyway. Somewhere in the .030” to .034” range is fine.

 

the -11 does deonte the gap, but im not aware of an ltr-7ix plug that has a different gap. there is an lZtr-7Aix-13 that has a larger gap thats often compared to an ltr-7ix-11, however it has a longer projected tip.

ngk 6510 is the stock number of the ltr-7ix-11.

 

Hi Sharkey and Slowbalt2000,

I am very grateful to you both!

The engine management system is possibly a rebranded unit or their own system. ECS Limited is on the documentation. The casing is a generic aluminum electronics project box. I have not looked inside but I assume we would find a Motorola chip with boost and VVT ability. Therefore, I left the info out… it is basically proprietary, and I can’t find a reference to it online.

Yes, we tried a parallel battery connection, but I ditched it, possibly too soon. I do appreciate what you are saying about messing with the logger / ECU. It has been a concern since day one for me.

I checked the MAP in the data. At times it rests at 88 – 90. Other times it reads 65. This is on the same lake within a 50-meter radius. Given this was in the mountains over 3,600 ft above sea level, I was happy with 88. The 65 is a bit worrisome, that would take me to a perfect world altitude of over 10,000 ft. Being a pressure sensor, my fear is the voltage in different sensors would be calibrated with 100 kPa at the same voltage-output and differing in there kPa per volt scale on either side. I agree to write this off as the data looks reasonable.

There is an open port on the throttle body but everything else is plugged. I will have the guys double check the points you mentioned.

Throttle Body. I am happy to write this off.

I have asked the guys to read the plugs. Brisk RR12S are in there. They were recommended by the seller / tuner. I would be asking them about this, and I have, but they have not responded.

I appreciate the common sense of adding more combustibles to the mix. I had the brake cleaner in hand, but I opted to bump up the cold start value on the ECU (stepper position). I will suggest they go back to basics Air, Fuel, and Spark.

Thank you Slowbalt2000, I was going to get the guys to check gaps on the plugs, but I wasn’t sure what they should run.

I will update when I hear back from the guys. I am 1,100 Km away from the engine, so this will be like playing the telephone game as kids.

Again, I am very grateful to both of you for your time and advice!

Cheers!

 

the map sensor thing is a big concern. a map sensor is linear voltage and kpa. a 1 bar map will have 100 kpa somewhere around 4.5 volts, a 2 bar will have 200 kpa at 4.5 volts and 100 kpa would be somewhere around 2.5 volts. what im trying to get at is 100 kpa is not always at the same voltage. i cant say ive ever run into a non-linear map sensor. i think its safe to say the correct one is being used, but there is for sure an issue with it. the map sensor may be used for barometric correction at initial key on, so if it thinks your at 10,000+ feet it may not have enough fuel to make it fire. i would have a good look over the wiring harness, make sure the pins in the connector are in good shape and clean, check the harness for potential damage, check the ecm connector. also check the map sensor out, make sure it looks physically ok. also check all the grounds.

the map reading need to be 100% rock solid, both key on and with it running. in fact, if the map sensor was a problem before hand it may be the reason the previous engine failed. in the early days of the l61 i blew up 4 engines by accidentally finding the limits of what they would do. the top ring land is very close to the top of the piston, and the ring gap is tight, if you run them just a hair too lean or have a slight bit of knock under boost it will butt the top ring and break the top of the piston. it doesnt take much boost for this to happen either. if the computer is working properly its likely just fine, but as they say, stupid in stupid out. if you have a sensor feeding wrong data it can be a bad day.

no problem with the brisk rr12s, aside from they may be a tad cold of a plug for what your doing, its closer to an ngk 8 heat range. not an issue right now unless they are fouling. should be gapped around the same as the ngk plugs we recommended. the coils should light off a large gap without an issue for starting, the issue with a large gap comes with boost so i wouldnt think that would be your issue at all.

 

I will have the guys go through the MAP sensor and loom to be safe. The data shows this MAP reading as bounce in the switch or a bit too much action by the human but it will be checked to be safe.

I will have the guys look at the plugs and hopefully they can start reading them when there is a no-start event along with you previous recomendations.

I will follow up when they complete their inspections and next test.

Cheers!

 

In regards to the data above, any thoughts on the knock while throttle is moving? Do you experience this on your engine?

 

Not to derail the thread but the last number does denote the pre-gap of the plug. Im probably thinking of different plugs that have multiple selections for pre-gap spec. It looks like the ltr only has -11 available.

 

i have seen some knock spikes when stabbing the throttle with my cobalt. this is generally caused by other things in the car, not by detonation. stiffer engine mounts can cause this, as well as things like slop in the drivetrain.

the bigger thing is with this ecm, how much time did they spend on tuning the knock detection system. this is one of the hardest things to set up and get tuned correctly in a stand alone system. really the sure fire way to set up a knock system is with destructive testing in a dyno cell, essentially pushing the engine till its audibly knocking it brains out, usually destroying several engines in the process. outside the oem manufacturing world, we dont do that for many reasons. ive found a number of ways to set up a knock sensor, but all of them say it will get it fairly close. so really what im getting at is how well set up is the computer? we just dont know.

that being said, i wouldnt worry too much about it too much. once you get the thing back on the water see what the knock is doing at steady state throttle while cruising, if it shows knock id get a pair of det-cans and have a listen.

 

Brisk Plugs - A+
I am not sure how this site is with brand /vendor chat but, a Brisk RR12S plug was recommended as one of three options by the engine tuner/seller for this L61. I contacted Brisk by email regarding plug gaps, and I was given another tool in solving this issue. I have no affiliation with Brisk, but they went far beyond expectations. There staff were very knowledgeable and helpful.

Plug Info
I sent them a dyno sheet and the engine configuration. They agreed with Sharkey that the RR12S is a cold plug for this application. It is a conservative plug but it would be good at avoiding knock. They also mentioned the plug is a few temperature ranges lower than the NGK plugs that were recommended (as mentioned above by Sharkey). The conclusion was this plug could be prone to carbon buildup when under light load use due to its temperature and the current engine configuration. They also mentioned, this plug may be too cold and may be the cause of the inability to start! (Future Readers: 'Too cold' for this engine configuration, fuel, and intended use, it is not a bad spark plug when put in the proper operating environment.)

Step One: get some Brisk RR14S plugs. One temp range higher than the RR12S. Still a conservative plug to avoid knock especially with the non-projected insulator nose but might be enough to get over the starting issue while being on the safe side for avoiding knock issues at WOT.

Information from Brisk:
NGK to Brisk equivalent
S9PYP4 = Brisk RR15YS
PTR5A10 = Brisk RR17YS
Brisk RR12S gap < 0.032" - 0.034" for this application. ( Good job Slowbalt2000)

Just for fun:
This engine dynoed (by the vendor) at:
252 Horsepower @ 5500 RPM
246 Ft/lbs @ 4700 RPM 90% of Max Torque available from 2200 RPM - 5500 RPM

 

So, they took the plugs out. For a three digit odometer reading, not great... Is this just too cold of a plug or has something changed to give the ECU the impression there is a need for more fuel? This is the question now. The moisture is hopefully from not being used but we are looking into a compression test for the head gasket. There is no sign of steam cleaning in there but it just might not have run enough to get that cleaning effect.

 

So, the injectors are the GB Remanufacturing 832-11207. GBR will not hand out an actual flow rate. From a fitment chart I found on e-bay, it is compatible with a factory Cobalt with Supercharger... Yes, that could be totally worthless information. The injectors are about 15% larger than the factory L61 injector but not 33% as you had mentioned. I am going to see if I can find anyone else with this ECU configuration and see if they have any injector information. That said, from looking at the plugs, this thing is very rich and or the plugs are too cold. Brisk is recommending their Brisk RR14S. So, they have been ordered and for good measure we ordered the 15YS as well.

If this gets too crazy, I may need to PM you, Sharkey. Since you are in BC maybe you can help us find a place to re-tune this thing? It will need an engine dyno not a wheel dyno... or maybe we can buy the same parts you are using and follow your lead... We will see how deep the rabbit hole goes first.