Carb to EFI
 

Hey , I’m fed up with the dominator always rich at idling want to go EFI.
individual throttle body’s or plenum with single body ?
and was going with fueltech as efi

need to hear you comments

If you mean 8x ITBs like a hilborn (which is what I have), then no, don’t do that. It’s lovely, but a fair bit of setup to get just right and give no vacuum signal which makes the efi system a bit harder to sort.

But for example, a 4 barrel TB to replace your carb - I have one of them too. It’s a nice piece of kit (with injectors into the manifold, not on the TB) and is straightforward. I have no experiences of the 4 barrel TB setup with injectors on the TB.

But if I was building my engine again, I would go with a full plenum and single throttle
body setup. You can get nice long runners on them to support good torque, simple throttle setup and good vacuum signal for the ECU.

Read up on some of the Daytona Sensors discussion on here lately. A lot of carb guys love those.

And if you go with a smaller 4150 base/flange size carb, then you will most likely not have the problems you are experiencing with a Dominator size carb. I once had Dominator size carbs on my 468cid engines that were on those engines when I originally bought the boat---after having a local guy try to tune them a little he kind of gave up and said they still just want to run too rich and gave me a black transom and throwing raw gas out the tailpipes. It got old very quickly---not so much that they could not work, but getting them to work properly was a hassle and just not user friendly in my opinion.

So when I built my 540cid engines I went with a Holley 4150 size carb---830cfm initially, then to a 950HP. Both worked great. I may get some push-back from you guys about properly tuning the Dominators, but anything can be fairly easy when/if you know what you're doing and those were Doms from about 30+ years ago and carb tech has come a long way since then.

I love the simplicity (for the most part) of a carburetor, etc.---I am more of a carb guy.---but I will try to find a way to make those 4150 size carbs work before I try to use a 4500 size Dominator ...and I will admit, when it comes to FI those Hilbonre FI with those velocity stacks are awesome looking.

For what it's worth it's Just my experience and .02 guys---doesn't mean I am right.

What is your timing at idle ?

https://cimg7.ibsrv.net/gimg/www.off...af1ee1a5f.jpeg
I am thinking something like this with fueltech What you think ?

Might be helpful if you told us your engine, boat, application, and goals…
I’ve put a LS in my boat, using the TBSS with upgrades 92mm throttle body.
Holley, fueltech, etc were all back ordered during covid. I went with a ligenfelter trg-002 to convert my gen4 58x/4x into a 24x/1x with a basic brain so I could get dbc vs dbw on throttle body. It works great on the cheap. Just charge the battery before starting. It gets picky on low battery starts. No issues when running, so far.

Lots of guys swear by fueltech. I prefer Holley but to each his own. My next upgrade would be Holley efi that’s fully potted for the tuning capability.

that intake looks solid to me. I’d go with a fast lsxrt if I needed a different intake.but power goals may dictate a high ram intake for you.
i Don’t know your application but here’s the biggest pain on this whole project… fuel pressure.
I have dual 55 gallon tanks then into the fuel/water separators into control valves through the pump, regulator/filter/return, and up to fuel rail.- this is a formula for fuel pump death when offshore. Will it work, sure. Will I have a pump fail? Probably faster than I should per tech support.

ive opted to add a fuel surge tank so I can have a low pressure pump pull it from the tanks through the fuel water separators and into the surge tank. From there a high pressure pump will take over and my return will be plumbed into the surge tank. I’ll still carry a spare pump just in case….

I love efi… so many advantages but the fuel delivery piece has been a pain for me.

https://cimg5.ibsrv.net/gimg/www.off...6cb17cc1a.jpeg
This is my motor . 572 Dart big m block merlin heads stainless marine gen 3 exhaust running full dry . Ignition system still stock with MSD coil only . Cam specs attached

Have you considered this

https://www.holley.com/products/mari...er_efi_marine/

Who makes that intake, your biggest issue with this particular style intake and I DO love them is thermostat housing clearance/flame arrestor clearance on a single engine. You CANNOT put a 90 degree elbow on one front of one of these NA and not kill off serious hp. Id like to see a intake like you pictured with about 2' longer runners (about 8"). I have made some OUTSTANDING hp numbers with modded Edelbrock proflow intakes/ throttle bodys that are very similar to what you pictured, did lots of flow development / dyno testing on various things bolted to the front of the throttle body with almost shocking results. Ive made HP numbers (680+) with a Edelbrock proflow ) on 509/515 engines with 89 octane BUT was hard (almost impossible) to implement in that config in a single engine boat, Smitty

I would look at the Holley EFI. Here is a very good read.
\
EFI for everyone - Offshoreonly.com

I saw these and was my first choice but you know how we are 😂 ……We need to complicate and spend more $$$$ for 1bhp

you have a picture of yours ?

I just picked up the manifold that Smitty was talking about for my Holley EFI engines. And spent my Saturday morning talking with him about the performance. I'll be switching to these from Cutler/Holley Multi-Port single plane intakes.
https://cimg1.ibsrv.net/gimg/www.off...ec03cd0960.jpg
https://cimg2.ibsrv.net/gimg/www.off...f44cacbdb9.jpg
https://cimg3.ibsrv.net/gimg/www.off...a3b24b28a2.jpg

I am going to 3D print an adapter flange to get the TB and arrestor away from the thermostat housing. And then I'll have JimV (Valako) blend the inner area of the intake.

Rookies got a good pic of the rect version, Ive used both the oval port and rectangle. Heres a brief summary of my testing on 3 different ones on 3 different engines, these are approximate numbers (dont have time ATM to go back and find exact numbers) but close so youll get the idea:
engine one was a 509, AFR 300 ovals, Bob M cam. Cam was in the 238/242 @.050 range. Intake was ported to match the tb and runners. Testing the 90 mm E tb we found even though it was claimed to flow 1150 or so, it flowed less then a 1000 out of box.
on my dyno engine had great BSFCS for being just over 9-1, on 89 octane made in excess of 680 hp on its best pull in dyno trim w headers w mufflers using J607, torqye wasnt as fabulose as the Hp, our goal was 650/650, instead we saw around 620 tq and 680+ hp. In boat there was barely no room for even a short cone filter directly on the TB so we used a 90 dgree elbow, it killed the power, boat was a heavy ass turd that was water logged (29 ft envision) so it was far from a rockstar
engine 2 was a 515 short block from Ron Sporl, customer bought it done from him vs having me build one to speed things up. Another set of AFR 300 CNC ovals, compression approx 9.3-1 if I remember right. My Dyno partner Norm also modded the 90 mm TB like first one, thinned shaft, cut down leading a and trailing edge of blade, ground out the drivability bump they put in for throttle response on the street. We did further testing and found that a 20$ Spectre transition piece/ volute going from 4.5 to 6' greatly enhanced the flow of tb on flow bench, talking sub 1000 box stock, just under 1200 moded and over 1500 w volute. I also bought just about every clamp on 4/4.5" cone filter and 6" cone filter that I could lay my hands on. Custom Cam from Bob M again, we focused on building more cylinder pressure/tq with a little less yet duration and moving intake Cl, etc. cam was like a 236/240 or so. om 89 octane on the dyno it made around 650 hp w no air horn, dropped to 620 give or take with short 4" clamp on cones, similar results we saw on flow bench and we had tested a 90 on flow bench which knocked flow off face of earth too. When i put the volute on, and retuned for it, got power back in the 680 hp range. Tried various 6" cones, found that a used KN 6" gave it virtually no hp drop. Thats all great BUT in the boat the volute hit the thermostat housing and there was no way possible to use the big KN either so that goes back to the importance of what goes in the front of these intakes. 90's absolutely kill the flow NA and hp, the wrong size and transition cone filter kills them too. They really want that volute and a very large KN staraight out front. On singles it hits the back seat.
3rd engine was a hot rod build 454 stroked to 496, afr 305s, large cam that was inappropriate for any inboard boat, just shy of 11-1 compression. Again, in round numbers it made around 675 hp with a VIC JR and modded holley 4150 that flowed around a 1000 CFM, tq was in the 610/620 range (DISMAL). We tested a rec port proflow on it w modded tb/volute, a cobbed up Mefi3 harness and ecm, made about 50 MORE hp and a tiny bit more tq. Weve never made the tq we expected from one BUT have exceeded the hp that even my dyno sim shows which rarely happens, FWIW, Smitty

Rookie, m using a desk top computer so I dont have access to my pics w/o alot of BS but post up the TB pics I sent you, Smitty

I just dynoed one of my engines with pro flow xt intake 92mm throttle body with smart coils. Was the first time using Holley efi very user friendly and the system worked great. Still working the tune but it did make 660hp at 5900rpm and 630 lbft of torque.

I have the spectre volute have not tried it yet will be getting that on the dyno session.

Per Smitty's request...
https://cimg9.ibsrv.net/gimg/www.off...d022015a3.jpeg
https://cimg0.ibsrv.net/gimg/www.off...f995999ad.jpeg
https://cimg1.ibsrv.net/gimg/www.off...91ef910c9.jpeg
https://cimg2.ibsrv.net/gimg/www.off...ec66c1a58.jpeg

Very nice blending smooth transition.

My dyno partner Norm did all the TB work, it was also quite surprising how close the Modded 90 mm tb flowed to a slightly modded 102 mm TB without the volute, within 40 cfm of each other If I recall correctly. Then with volute the 102 went up 200+ cfm more then the 90 mm gained with it. It shows us that what gets bolted on front of it is critical. Several of the cone filters I bought to try with this on the dyno even with a attempt by manufacturer to create a sorta volute in the cones filter still killed flow, none of them were blended real great, Smitty

I do have the room for a large cone air filter in front of my engines luckily. I am also running the Holley ls style 92mm throttle body. The intakes have not had any porting done to them.

I bought over 500$ worth of various conw filters to test when I dynoed the second one I used with the soectre adapter. The winner was a ised 6" x 10 or so kn that we had laying arouns.
Im getting close to dtnoing a 4th one soon and otsered this:
https://www.ebay.com/itm/33487813144...mis&media=COPY
to use, it appears to be same one

I will definitely get one of those air filters on the way to try. Going to start working on getting the volute to fit the throttle body. May have to mill down the outer lip of it to slide up on to the throttle bod.

yes, it will take work to get the volute to fit over it, I cut one down w die grinder to get it to fit, the most recent one rookie posted pics of we used mill and rotary table to cut lip down and bored the volute

Really appreciate all the advice on this set up.

I went these intakes over using the factory 500efi intakes after reading some good things about the edelbrock pro flo xt.

https://cimg0.ibsrv.net/gimg/www.off...87064df01.jpeg
Was browsing and saw this 2023 merc 565, i like this plenum did a bit more searching and found the parts diagram. Do you see like me ? It’s like a 525 plenum with 2 TB on the surface instead on the side. Which I think it makes more sense if you are not planning for force induction.
https://cimg1.ibsrv.net/gimg/www.off...9048da82ab.png
Someone knows the size of these TB merc 565 is using ?

I have noticed that as wee on the 565. Looks like two of the mercury 520 throttle bodies on the top. I believe Eddie young did some plenum modifications to 500efi intakes at one time adding a second throttle body and moving them to the top of the plenum as well.

Not sure of the size, but it is the same part # used on all the QC motors and some OB's.

• 1100 QC4V - 0M965965 & Up
• 1350 QC4V - 0M965309 & Up
• 1650 QC4V - 0M965309 & Up
• 565 EFI - 0M967821 & Up
• 200 (3.0L DFI)(DTS) - 0T980000 THRU 1B417701
• 200 (3.0L DFI)(DTS) - 1B417702 THRU 1B504988
• 200 (3.0L DFI)(DTS) - 1B504989 & Up
• 225 (3.0L-DFI)(DTS) - 0T599000 THRU 1B417701
• 225 (3.0L-DFI)(DTS) - 1B417702 THRU 1B504988
• 225 (3.0L-DFI)(DTS) - 1B504989 & Up

From what I have read I believe they are 80mm throttle bodies.

It’s written made in Germany probably bosch .

https://cimg7.ibsrv.net/gimg/www.off...0794de0e1.jpeg
https://cimg0.ibsrv.net/gimg/www.off...00668def1.jpeg
This is the setup that I am running with Holley hp efi and dual sync distributor and smart coils like the 700sci use.
https://cimg2.ibsrv.net/gimg/www.off...cb5fee884.jpeg

What thermostat housing are you using?

I was wondering that myself, looks like one for a jet boat

https://cimg8.ibsrv.net/gimg/www.off...a5877680b3.png
Just divided water outlet from Hardin

https://www.enginelabs.com/news/test...s-on-the-dyno/


I think TB on the surface of plenum is better . Saw this article this morning

I have the customers 548 on the dyno, ordered this to try to gain tstat hsg clearance , the air horns already hitting the only dyno tstat housing I could get to fit at all. Gonna run it with it and without it of course and see what it does to the hp. Attachment 577752

That may be the ticket there to get the clearance for the volute