zev Posted March 1 Share Posted March 1 (edited) Hey All! I have a 72Z with a 3L Rebello stroker and triple Weber 45’s. The thing absolutely rips, but at low speed I have some drivability issues that I haven’t been able to tune out and I think that’s just the tradeoff of running DCOE’s. I’m considering working with chris at Godzilla raceWorks to have him install their Bosch ITB fuel injection setup but I’m curious how this will affect the overall power and throttle response. I don’t have a ton of experience with fuel injection but my assumption is that the car will have much improved drivability with the tradeoff of the gut-punch immediacy of the Webers? Can anyone advise me as to what the downsides are to making the switch? Thanks. Edited March 1 by zev Quote Link to comment Share on other sites More sharing options...
MONZTER Posted March 2 Share Posted March 2 You’ll lose nothing in my opinion, Fuel injection has a tunable acceleration feature just like a pump on the Webbers. I ditched mine for fuel injection and it was way better everywhere and no hundreds of dollars to make a jetting change, just a few click on the keyboard to make changes and tune it. I would never go back. 1 Quote Link to comment Share on other sites More sharing options...
AydinZ71 Posted March 2 Share Posted March 2 Fuel injection. Next question ☺️😎 Quote Link to comment Share on other sites More sharing options...
Derek Posted March 2 Share Posted March 2 Fuel injection if you don't live within driving distance to a tuner that knows side drafts. I like that I can tweak things myself and quickly revert back to a saved tune when I invariably screw it up:) My tuner has done a very good job with my ITB's and I've never even met him in person. Quote Link to comment Share on other sites More sharing options...
jonbill Posted March 2 Share Posted March 2 Just to be a bit contrary: IF you can find someone competent with dual sidedraughts, I guarantee it will be a lot cheaper to get the webers spot on than to supply, fit, tune ITBs and EFI Quote Link to comment Share on other sites More sharing options...
zev Posted March 2 Author Share Posted March 2 Wow, mostly pro-injection!! Anyone else who wants to contribute I’m all ears. also one other question… if my Webers are 45 with 38mm venturis should the ITB’s be sized at 45 also? Quote Link to comment Share on other sites More sharing options...
jonbill Posted March 2 Share Posted March 2 50s ftw. Quote Link to comment Share on other sites More sharing options...
tube80z Posted March 2 Share Posted March 2 4 hours ago, zev said: Wow, mostly pro-injection!! Anyone else who wants to contribute I’m all ears. also one other question… if my Webers are 45 with 38mm venturis should the ITB’s be sized at 45 also? I have a long history with sidedrafts and used to have tons of jets, emulsion tubes, etc. The advantage you'd see on just a 45 mm throttlebody is that you don't have the auxiliary venturi and the chokes. So you'll see more airflow with EFI than with the carbs. Do you need a larger throttlebody is the question? Do you currently see a vacuum in the manifold? If your engine makes over 300 HP then I'd be inclined to look at a 50s or 55s. I'd call Rebello and ask him for a recommendation as he'd know best. Cary Quote Link to comment Share on other sites More sharing options...
zev Posted March 3 Author Share Posted March 3 6 hours ago, tube80z said: I have a long history with sidedrafts and used to have tons of jets, emulsion tubes, etc. The advantage you'd see on just a 45 mm throttlebody is that you don't have the auxiliary venturi and the chokes. So you'll see more airflow with EFI than with the carbs. Do you need a larger throttlebody is the question? Do you currently see a vacuum in the manifold? If your engine makes over 300 HP then I'd be inclined to look at a 50s or 55s. I'd call Rebello and ask him for a recommendation as he'd know best. Cary Great advice. Thanks Cary. Quote Link to comment Share on other sites More sharing options...
DuffyMahoney Posted March 3 Share Posted March 3 You should try one of my progressive throttle cams first, it might help the street aspect some. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 3 Share Posted March 3 I was under the impression that since you don't need airflow to atomize the fuel, you should go bigger on ITBs. Quote Link to comment Share on other sites More sharing options...
AydinZ71 Posted March 4 Share Posted March 4 On 3/2/2024 at 2:07 PM, tube80z said: I have a long history with sidedrafts and used to have tons of jets, emulsion tubes, etc. The advantage you'd see on just a 45 mm throttlebody is that you don't have the auxiliary venturi and the chokes. So you'll see more airflow with EFI than with the carbs. Do you need a larger throttlebody is the question? Do you currently see a vacuum in the manifold? If your engine makes over 300 HP then I'd be inclined to look at a 50s or 55s. I'd call Rebello and ask him for a recommendation as he'd know best. Cary Same advice given by Jenvey. 300hp+ for the 50’s. As you said Cary, if you don’t measure fraction of PSI static pressure difference between atmosphere and the manifold at WOT, then there should not be a loss of power from restriction. Conversely, too large will reduce flow velocity and as a result, responsiveness, and torque at lower rpm’s. In general, marketing tends to sway people towards bigger. From everyone I have spoken to with experience, 47 is the biggest you would want to go on street DCOE’s (2.8-3L), and even 45 FI ITB’s is probably enough. Quote Link to comment Share on other sites More sharing options...
DuffyMahoney Posted March 4 Share Posted March 4 EFI hardware said 45s are still plenty for my 3.1L. I got the pro version which is a taper bore, so technically the butteflies are 47mm. Quote Link to comment Share on other sites More sharing options...
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