Mercury EFI, Opti info

I’ve kinda been looking at some different engines, and of course, I know I’d love an Opti. But I think some of the Yammys are good too. With Yammys, they have the HPDI and OX66 fuel injection. The question is, is the HPDI comparable to the Opti, and the OX66 is comparable to the EFI?

Also, on Yamaha’s site, they have tests that show how many GPH some of their engines used during the tests. Does anyone know if there’s any kind of info like that for Mercs? Thanks!

To me the direct injection is the ulimate,it is the “simplest”.No intake plenum,no mixing or swirl, nothin.Just the proper amount of fuel delivered at the right time.It’s a heartbeat away from diesel type technology(no ignition system ).
Having said that ANY fuel injection that relies on maps(computor programs) instead of real time sensors is inferior.So to me if fuel delivery id my sole criteria for judging I go sensors not maps.(that will tick the Harley boys off).

The only truly independent reviews I’ve seen were for the 115’s,it’s the only class where all the majors produce a motor…
The results..they are all good from Nissan,Suzuki,Yamaha,Mercury,Evinrude/Johnsin,Honda etc.
As a rule the Hondas have a slight fuel advantage but they are heavier,so tit for tat.

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ANY fuel injection that relies on maps(computor programs) instead of real time sensors is inferior.So to me if fuel delivery id my sole criteria for judging I go sensors not maps.

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So you’re saying that EFIs have the mixing in the plenum (with the MAPs), and the Optis are direct injected (sensors)? Same with HPDIs vs. OX66?

I don’t know who has maps or censors,but I’d find out before laying out 12K or so.
Any direct injection will not use a plenum for the mixing of fuel/air…that will be done in the chamber in the head,it’s as close to goof proof as you can get with gasoline type fuel.Close in ability is any injector pr cylinder system(one injector pr cylinder,near the chamber).Any system that has an injector servicing more than one cylinder,or a single injector serving all cylinders is not quite as good.
As a side note,the fellas who pioneered direct injection own a carb shop in Eau Claire,Wi.They were sponsored by Buick and developed the system on a dragster.The little naturally aspirated six cylinder they developed was sooooo good they were not allowed to use their times as “official”.This was late eighties and into the early nineties.

As I read my own post I found something that I need to clarify.Direct injection doesn’t mean there won’t be an intake plenum,the plenum will just have air…no fuel.
If an intake valve has to let a fuel/air mix into the chamber it’s not direct injection.(four stroke)If the intake valve allows only air into the chamber now it’s “direct injection”.

http://www.yamaha-motor.com/outboard/feat_hpdi_2006.aspx

censors and direct injection…waaaay cool

http://www.yamaha-motor.com/outboard/feat_vmax_series2.aspx

fuel maps not as cool

http://www.honda-marine.com/modelDetail.aspx?modelGroup=BF150

“programmed injection”…fuel maps,not as cool.

http://www.mercurymarine.com/engines/outboards/optimax/thepower.php

direct injected,but Merc doesn’t specify maps or sensors

What are you guys talking about? Are you saying efi is a bad system?

No sir,EFI in my opinion is better.There are differences in any injection system.Some(most) rely on a computor program for fuel/air mix.So far the only sytem that I can say for certain that does not use MAPS is Yamahas’HPDI.
Some fuel injection uses one injector/pr cylinder..that is a positive.Some EFI systems inject fuel directly into the chamber,some do not.
EFI is different in many ways,it’s not just EFI or not.

225 mercury efi

25 yamee..carbed

Thanks for those great links. The two for Yamaha look the same to me, can’t really see the second one too well.

I used to have a 91 Silverado with a 350 in it. It had the ‘throttle body’ on it, which, as I understand it, meant the fuel was injected into the body, mixed with air, then sent to the cylinders. A step up from that would be direct injection into each cylinder.

So can you look at this as EFIs and OX66s being a ‘throttle body’, and Optis and HPDIs being direct injected into each cylinder?

So that would probably naturally mean your HPDIs and Optis will be better with fuel over the others?

Just trying to get this all straight in my brain.

EFI simply means that an electronic brain(ecu or ecm) dictates when and how much fuel is delivered.
EFI can be incorporaterd into a single injector serving multiple cylinders.Your early Chev may have been an example.EFI can be used in “muti port”,one injector serving two intake ports,thus a V-6 would have 3 injectors.EFI can be incorporated into injector pr cylinder systems,each cylinder having it’s own injector.
The throttle body you mentioned is to control the air.On early EFI systems that is where the single injector was placed.When EFI evolved to muti-port the throttle body was still there to control air but the injectors were moved to the intake manifolds.As EFI continued to evolve,the throttle body remains to control air,the injectors are again moved to a new location in the intake manifold(one pr cylinder).As EFI continues to evolve the throttle body still controls air,the injectors are once again moved.This time it’s from external position (manifold) to INSIDE the cylinder, hence ….direct injection…

” The two for Yamaha look the same to me, can’t really see the second one too well”
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If you read the specs for the HPDI it states that sensors control the fuel air mix.The V-max states programmed or mapped fuel.
I’m findin that the 0S66 was a joint venture with Suzuki and Yamaha,and early versions were….welll…they had some issues.The later versions seem to have better reviews.

The HPDI coordinates information gathered by engine sensors to adjust fuel delivery and ignition timing. Yamaha HPDI is unique among DFI systems because it uses an exhaust oxygen sensor to gauge the presence of unburned fuel. Unlike the Mercury Optimax and Evinrude Ficht DFI systems, Yamaha HPDI doesn’t run in a super-lean stratified mode at low-engine speeds, so it doesn’t match the ultra-low emissions and fuel-use levels of its competition between idle and 2500 rpm. Yamaha claims its HPDI motors meet the EPA 2006 emissions level without stratified combustion.
Well I got into this deeper than I had planned,but there it is.The only real time EFI system is HPDI,all the others are programmed or mapped systems.