EFI to carb wiring.

[totheredline]

Not really sure where to start but basically I decided to ditch megasquirt1 v2.2 and go with a Holley 4bbl+euro manifold for my high comp m30 build. Does anyone have experience with this kind of conversion. I'd like to keep the stock fuel pump, fuel level senders and gauge, speedo and blower motor/switches.

[nando]

the DME has nothing to do with the fuel level sensors or gages, other than the tachometer. it has nothing to do with the blower motor either.

The problem will be the fuel pump. you can easily jump the relay so it's always on with the ignition, but that's not really safe. you really only want it running if the engine is running.

[jalopi]

The fuel level senders/gauge, speedo and HVAC stuff should continue to work just fine even without the megasquirt. As far as the fuel pump goes, depends on how the P.O. set it up, though if it was fucked with all you have to do is wire the (purple?) wire up to the ignition switch. Either that or run it to a toggle switch in the dash.

Also, you'll have to get a fuel pressure regulator for carbs. Any one will do, I think my Holley one was $20 from Summit

But why are you switching from EFI to carb? Especially from a Megasquirt? Unless you're trying to out-hipster other peoples' builds or the Megasquirt isn't working right I don't see the point. Starting when it's cold will suck, fuel economy will suck, doing any sort of non linear spirited driving will suck. I had a carb on my 302 e30, but that was only because I didn't have any EFI parts and it would've cost me 3x as much to do a Megasquirt/EFI setup. IMO if you have a working (not to mention easily tunable aftermarket) EFI setup there's no reason to swap to a carb

[totheredline]

The fuel level senders/gauge, speedo and HVAC stuff should continue to work just fine even without the megasquirt. As far as the fuel pump goes, depends on how the P.O. set it up, though if it was fucked with all you have to do is wire the (purple?) wire up to the ignition switch. Either that or run it to a toggle switch in the dash.

Also, you'll have to get a fuel pressure regulator for carbs. Any one will do, I think my Holley one was $20 from Summit

But why are you switching from EFI to carb? Especially from a Megasquirt? Unless you're trying to out-hipster other peoples' builds or the Megasquirt isn't working right I don't see the point. Starting when it's cold will suck, fuel economy will suck, doing any sort of non linear spirited driving will suck. I had a carb on my 302 e30, but that was only because I didn't have any EFI parts and it would've cost me 3x as much to do a Megasquirt/EFI setup. IMO if you have a working (not to mention easily tunable aftermarket) EFI setup there's no reason to swap to a carb

Thanks for the replies guys.

I have my reasons for going carb. Mostly just the ease of tuning. I'm leaving for boot camp here in November ish, and I've still got a lot of work to do on the car. The PO kept the car stock so I was going to have to convert the car to MS controlling fuel only. Really the only things I had to run MS was the box, and a mechanical dizzy setup from an Ljet car. I still needed injectors, sensors ect. I know that this carb setup isn't going to make as much power, get better fuel economy, ect. Butttt I can dial in a holley in a day or two, I don't have to wire up a MS harness ect. With the carb I'll be able to have fun over the summer with the car. After I get through training I'll be converting it to a real standalone EFI system. I just don't have the time or money right now...


As far as wiring goes.

I should be able to get the stock temp gauge, level sensor and speedo to work? Can I tap the senders into the C101?

And for the fuel pump I can just use a manual switch in place of the relay?

[nando]

most of those have nothing to do with the engine. they will work without doing anything.

the only ones you'll need are the coolant sensor and a tach output. should be able to connect the tach output to coil -. yes, you can wire them through C101.

you could do a manual switch. that might be better than having it on all the time with the ignition on. but you will want to switch it through a relay, you don't want the pump current going through a switch in the cabin.

[jalopi]

sounds like you want something that you don't have to fuck with all the time - if that's the case and you're dead set on doing a carb, don't get a holley.

holleys are super nice in terms of adjustability and are typically better than edelbrocks when it comes to fuel slosh, but everyone i've known who has a holley is constantly messing with it. then again, the smallest carb edelbrock still makes (or has made, to my knowledge) is a 500cfm, which might be too big for your application

[totheredline]

most of those have nothing to do with the engine. they will work without doing anything.

the only ones you'll need are the coolant sensor and a tach output. should be able to connect the tach output to coil -. yes, you can wire them through C101.

you could do a manual switch. that might be better than having it on all the time with the ignition on. but you will want to switch it through a relay, you don't want the pump current going through a switch in the cabin.

^would run a relay and fuse for sure. Alsmost burt my 318is down when I wired the fuel cutoff switch directly to power instead of control.

So hold on, the tach imput goes through the C101? Ive heard that theres a connector under the Dash for tach imput as well. For the stock tach of course. May be easier just to pull the stock tach out of the cluster and get an aftermarket one to fit in the same spot.

[totheredline]

sounds like you want something that you don't have to fuck with all the time - if that's the case and you're dead set on doing a carb, don't get a holley.

holleys are super nice in terms of adjustability and are typically better than edelbrocks when it comes to fuel slosh, but everyone i've known who has a holley is constantly messing with it. then again, the smallest carb edelbrock still makes (or has made, to my knowledge) is a 500cfm, which might be too big for your application

Yeah I think I read somewhere in your build thread that you were experiencing carb troubles when you were drifting. According to the E9 and E3 guys, I need 550-600 cfm. A lot of them run twin Weber 38/38 wich are about 375 cfm each. I really built the car for autocross, back road blasting and street fighting so I need something with mechanical secondaries that can cope with the twisties.


Heres a pic of the manifold

[jalopi]

just keep in mind alot of people tend to run way too much carb too ;)

i'd think 550-600cfm would be way too much on a stock m30, shit i was rocking a 600 on my 302 and it had aluminum heads and a cam. just remember that a bigger cone + a smaller vacuum pump = reduced air velocity which in turn = shittier fuel atomization

also, i didn't have the insane issues that so many other people complained about with carb'd drifting - as long as you kept your foot in it the car wouldn't stall or anything (god help you if you lifted though). the only issue i had was that during drifts my wideband would be all over the place, ranging from 9:1 ~ 17:1. still ran fine though

if you do go with the holley do yourself a favor and get wedged floats for it, i hear those do wonders for fuel slosh issues

[totheredline]

just keep in mind alot of people tend to run way too much carb too ;)

I used this CFM calculator and it said 491 (round up to 500cfm) which seems like a more reasonable number for a 7200rpm m30. I can always play with the jets too The motor is pretty heavily modified. Extensive porting, 10.4ish:1 comp, polish, 1mm oversized valves, 292 cam with 11.3mm peak lift and an LSA of 108. H-beams, chromoly retainers, double valve springs, HD rockers.... Yeah. Should be a beast of an M30. I really wish I could afford a good standalone but time is against me and Im a 19 year old kid who doesn't make a whole lot of money. I know that Im not going to be tapping into the motors full potential with the carb setup.

On a positive note itll probably sound amazing and get lots of people to look at car meets..

[jalopi]

jeez, why did i think this thing was stock, lol

500 sounds pretty reasonable to me as well, should keep your lower RPMs from being shitty

you're not gonna be super displeased with the carb, but please do yourself a favor and get yourself a wideband, it will make your life soooooo much easier when tuning it

also try to aim for an AFR of about 12-13. i know that sounds really rich, but trust me you don't want that shit running too lean through turns with that much compression

[totheredline]

I actual have an AEM uego but I've never used it. I'll probably get a good vacuum gauge to mount in my gauge pod as well. I'm really having a hard time finding a carb. Edlebrock are the only company I can find that makes brand new 500cfm 4bbl's. And its cheap. Would I be seriously disappointed with the eddy?

[jalopi]

probably not, they're not perfect but it'll work well enough for what you want it to do. there's a few things i suggest you do when embarking on this carb journey:

* get the electronic choke version. trust me, it's worth the extra coin

* also get their calibration kit, part ## 1486. you will 100% need it, as-is your car will probably run pig rich with that carb

* buy this fuel pressure regulator. you will be tempted by other cheaper, non-return style regulators on summit. do not buy these. they were intended for cars with low pressure carb-style fuel pumps. the amount of pressure coming from your high pressure pump will blow the diaphragm in the regulator prematurely and without warning

things to keep in mind:

* if you're gonna spin out, push the clutch pedal and r3v the engine just before the car comes to a complete stop. this will keep the engine from flooding and stalling

* plan trips ahead of time, your car will run like dogshit for the first few minutes unless it's 90* out

* you probably won't have any super bad issues with autoX as long as you're not rocking wide ass sticky icky tires

that's all i can think of for now

[totheredline]

Just dropped like $500 on a carb, that fpr, spreadbore adapter a calibration kit and some various hardware. I went with the 500cfm eddy performer with electric choke. After watching a lot of reviews, how to videos, and browsing various forums I think I'll be pretty satisfied with it. Should be stupid simple to get my car on the road now.

[jalopi]

you 100% sure you need that adapter? the edelbrock carbs are drilled for two different kinds of mounting bolt patterns (and they're basically webers [you'll even see the weber emblem on it, lol], so there's a good chance it'll fit on your manifold)

btw the paper carb gasket edelbrock includes in the box is kind of poop. use some fuel-resistant RTV on both sides of the gasket and you'll be gold

let us know how it runs after the install!