LS speed density
 

Hi all I am new to the forum so maybe this post is in the wrong link...Anyway I have an ls3 in my ski boat currently running on a carb and msd box setup, I would like to change it to efi but am having a hard time figuring out how to get around the wet exhaust manifolds (no MAF or O2 sensors), basically running a speed density open loop system. Has anyone run into this and come up with a solid fix? I saw one post from a few years ago by wasted income that was just about exactly what I'm talking about, any help would be greatly appreciated!

Thanks
Will

can be done, but I would leave the carb on...way simpler

I don't know what type of manifolds you have but there are spacers out there that slip into a joint to accommodate an O2 sensor such as the Wags Engineering unit. Or you can get one made.

http://wagsengineering.com/products/...sensor-spacer/

There's various EFI TB setups that will plug and play. FAST, Holley Sniper, etc.

I saw those manifold adapters and actually emailed wags but didn't get a response..I would like to just drop a factory intake harness and ecm in it, if I can run o2 then that makes it easier but I haven't come up with a solution yet, thank you for your responses

Nothing wrong with open loop speed density. Same as the efi merc engines. Use the factory ect/iat tables. You will need to rig up at least temporarily an o2 sensor to get the VE and PE dialed in. Once there you're good.

This may be of use.
http://www.offshoreonly.com/forums/d...setup-how.html

If you're thinking of dropping a factory merc system on there that would be a major pita, and many folks pull those off and put a carb on it.

I tuned my LS jet boat OLSD. I made a temporary dry tailpipe to accomodate a wideband O2 to get the tune dialed in. The good news is that EFI tuning on a boat is significantly easier than a car. You basically have just a diagonal line to tune on the 3D VE map instead of a larger portion of the map since there are no gears to change, so the load vs rpm stays pretty linear.

Was there a reason you decided to go speed density instead of MAF? Space or water intrusion? I am having a hard time finding a tuner that will touch something like that...and I have no expierience in EFI live or hp tuners personally. Kind of stuck at the moment trying to figure that part out, do you know anyone/do you tune for others?

Thanks

I have a LQ4 twin turbo in my boat, running Holley HP EFI in speed density. I would figure out away to get an o2 sensor in place otherwise you are just guessing when it comes to EFI.

If you can get a 02 sensor in place you can running self learn and the boat will "tune" itself.

Holley (among others) makes a really nice fuel injection set-up that just replaces the carb(s).

This is the way I would go
https://www.holley.com/products/fuel...parts/550-511K

You will need todo a elec fuel pump, and strongly recommended an 02 sensor, once you have it tuned in you can disable self learn and just run it off the base map(speed density).

I have mine set-up to only running closed loop above 2000rpm, and only adjust upto 10% of the value.

Personally I went SD instead of MAF because that's the way I've always tuned the boosted stuff I've done. It's easier than screwing around with calibrating the MAF table, and it can be made to run every bit as well. Any good tuner should have no problem tuning a speed density setup. In fact, like Turbom alluded to, some of the big name aftermarket EFI systems (like the Holley) doesn't have the capability to run a MAF....it's all speed density.