1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

dual webber carbed d15 + vtec head swap ?!?

Discussion in 'Civic and CRX - EF' started by EvoTec1, Jun 7, 2007.

  1. EvoTec1

    EvoTec1 Member

    Messages:
    98
    Likes Received:
    2
    Joined:
    Mar 22, 2007
    Location:
    Tacoma, WA
    Hey,

    A friend of mine just got this old ford fiesta ghia, its a german made ford with a built motor and dual webber 40's. I'm in love with the induction noise of it all, and having to goose the gas to get it started.

    No one likes the d series anymore, and it seems like everyone is in a rush to go vtec... or carbed...

    But has anyone ever done this?

    How would you make a vtec head work in such a setup?

    I could only imagine the sound of a mildly cammed d15 hitting vtec and pulling to like 7 grand...

    All the cheap hondas i'm looking at have d 15's, they are pretty good motors, right? Ive heard that even though they lack displacement they can spin pretty high without flying to pieces.

    I'm looking to build a car for the nasa honda challenge. Put this 1.5 liter vtec motor in a 91 non si shell with a si transmission, and the weight break is around 1900 lbs.

    I'm about to go take advantage of the search feature, but in the mean time you should post some d15 builds and timeslips, as Ive never heard anything about built d15's in detail... and what do you guys think about the dual carb idea? We don't have to pop the hood for emissions, and i have a lc1 wideband... so with a cat and a good tune i could pass emissions....right?
     
  2. K2e2vin

    K2e2vin Senior Member

    Messages:
    8,446
    Likes Received:
    92
    Joined:
    Jan 2, 2003
    Location:
    Raleigh, NC
    Dude, done plenty of times ;) check out D-series.org Also, one of the most powerful NA D-series uses carb's also(Bisi E.; non VTEC D15 and D16)

    There are two D15s, the D15B1,B2, B7, etc(non VTEC)....and the D15B VTEC. The non-VTEC ones weren't really built to rev but can with upgraded parts(rods mainly). The VTEC one uses the bigger and longer D16 rod and redlines around 7200rpm stock.

    If you drag race, definitely go with the carbs! Also, check out crxmotorsport's SCCA race car; he's running a built D15.
     
  3. jlicrx

    jlicrx Senior Member

    Messages:
    1,891
    Likes Received:
    65
    Joined:
    Jun 5, 2003
    Location:
    Colorado Springs
    just use rpm switch to activate the VTEC solenoid
     
  4. jlicrx

    jlicrx Senior Member

    Messages:
    1,891
    Likes Received:
    65
    Joined:
    Jun 5, 2003
    Location:
    Colorado Springs
    with the carbs, you have no need for an ECU but you need to have a way to control the ignition timing since the ECU, whose main function is to control the fuel injection, also controls the timing - on our dual Weber DOHC ZC drag only car, we use the MSD 6AL ignition, MSD Blaster 3 External Coil, MSD 8979 Multi-Function Ignition Controller and MSD Crank Trigger Pick-up mounted on the oil pan rail with MSD Flying Magnets installed in the back side of the flywheel - with this you can remove all of the sensors, etc. from inside the distributor and just have the shaft with the rotor on it - nothing else in the distributor housing

    you may have trouble finding a dual Weber intake manifold for the SOHC D-series engine - they are available for the DOHC ZC
     
    Last edited: Jun 7, 2007
  5. phyregod

    phyregod !!YTINASNI

    Messages:
    9,449
    Likes Received:
    225
    Joined:
    Jun 11, 2005
    Location:
    Central Texas
    Other than sound.. Why would you want to go backwards with technology? Injectors are better all the way around. Better power, better response, better gas mileage, easier starts, etc etc.. Perhaps you want to do Independent throttle bodies instead? Keep the FI?
     
  6. K2e2vin

    K2e2vin Senior Member

    Messages:
    8,446
    Likes Received:
    92
    Joined:
    Jan 2, 2003
    Location:
    Raleigh, NC
    Carburetors win in the fuel atomization category, which results in higher peak power. They do lack response and power band; which is why you don't really see them on road course cars. This is how Bisi was able to get away with +15:1 compression....on pump gas. He stated that for fuel injectors to atomizes as well as carburetors; the injectors would have to be back pretty far(longer than the engine bay). Also, someone on HT did a dyno on a B16 and gained like 6whp from just moving the injectors further down the intake tract; which proves atomization makes a difference.
     
    1 person likes this.
  7. EvoTec1

    EvoTec1 Member

    Messages:
    98
    Likes Received:
    2
    Joined:
    Mar 22, 2007
    Location:
    Tacoma, WA
    yeah, the fuel atomization process in a carb works almost like water injection, cooling the intake charge.... I come from a background of muscle cars, I once watched my dad's friend convert his 12:1 aluminum headed big block to efi and then battle detonation for an entire season before changing back.

    I think I'm in it for the sound really, I love drag racing and want to road race as well. I just got crome, a hulog and an ostrich so tuning for efi is no problem..... I dunno why I waited to buy all that tuning stuff just to come down with an itch to use webbers.....

    That scca car sounds like it will be right down my alley....

    Is there any way I can just like lock out the fuel table, and still use the ecu to control timing? i know thats probably a dumb question, but I might as well learn why it WONT work....
     
  8. jlicrx

    jlicrx Senior Member

    Messages:
    1,891
    Likes Received:
    65
    Joined:
    Jun 5, 2003
    Location:
    Colorado Springs
    there might be a way to do that, but i don't know what it would entail - however, anyway you slice it, the OEM ECU was designed to give the most fuel economy with the least amount of emissions, and still have decent power - no matter what you do to the ECU, it will still try to perform the functions it was designed for - it will read the O2 sensor along with the other sensors and adjust the fuel and timing - if you want to stay fuel injected, you would be better off using a stand alone system like AEM rather than a band-aid approach to the OEM ECU - on our engine which has all stock internals, with the exception of running Crespo Stage 4 camshafts, the best we could get out of it, using all different kinds of ECUs with various Maps, etc. was 138whp on race gas - getting rid of the injection and switching to the carbs and the MSD 8979 jumped it up to just over 150whp on race gas - this is without messing with the camshaft timing at all - they are still at 0 - our primary reason for going to the carbs was that with the fuel injection, the car on the drag strip was not consistent - we never knew what it was going to do from one run to the next - it could vary by 10 to 15 hundreths - in bracket racing, which is what we run, you have to be reasonably sure that it will run whatever you dial-in - otherwise you will go home early every time - with the carbs it is much more consistent and will run within 3-4 hundreths every time - i am not saying that carbs are always better than the fuel injection, but in our case where it is drag only and only runs at wide open throttle they work better than the injection because we only have to tune it for wide open throttle - for a road course or autocross car you would be better off with the injection - when tuning the carbs, if you want mid-range power you will prbably have to sacrifice a little top end power - as for the carbed engine being hard to start, etc. it is simply not true - ours fires right up and will idle at 300-400 rpm
     
  9. EvoTec1

    EvoTec1 Member

    Messages:
    98
    Likes Received:
    2
    Joined:
    Mar 22, 2007
    Location:
    Tacoma, WA
    Yeah bracket racing...good times. That would be kinda funny seeing a guy running a carb and an automatic in a civic to kill at the wednesday night local series.

    I wasn't trying to keep the fuel injection, i just want to keep the flexibility and datalogging ability of having a laptop controlled timing curve. It sounds like you have some expensive/exotic stuff done to your ignition system... but 150 IS the best number ive ever heard for a N/A D series motor so hey.

    so lets go into that.... how much can be pared from the system before it starts throwing up? (and can't i just delete specific codes at will like I can for the gm ecu's?)
     
  10. jlicrx

    jlicrx Senior Member

    Messages:
    1,891
    Likes Received:
    65
    Joined:
    Jun 5, 2003
    Location:
    Colorado Springs
    with the MSD 8979, we use the laptop to plot the timing curve and to control launch rpm and shift points - simple task - takes longer for computer to boot up than it takes to change the timing - the 8979 has the capabilty to set a timing curve down to 0.1 degree at every 100 rpm - also has capability of running different timing curve for each cylinder, if you want, but that seems like a lot more trouble than it would be worth - you can also have shift lights set at different rpm in each gear, which is great for drag racing - we have the wideband Innovate LM1 with rpm logging which we use for the air/fuel control - we log every run and if needed we just manually change carb jets to get it right - with the Webers, jet change is about 5 minute job - yes, the entire set-up was pretty expensive, but going fast and consistent NA costs money - that 150whp is with all stock internals, except the cams - we have tried upping the compression to different things, even up to 13.5:1 - no significant gain for the money spent - i really don't know how much can be done to the OEM ECU as far as deleting sensors from the loop - i am not a fan of chipped ECUs, too many variables

    Multi-Function Ignition Controllers, PN 8979, PN 8977
     
Verification:
Draft saved Draft deleted

Share This Page