2.7 CIS to Carbs - how much HP loss? Options

[naro914]

This is a good discussion....

I have carbs. I like them, but have thought about something different for Huey and relatively daily street use.
I'd like to stay away from CIS - heard too many horror stories
Not big on MFI just because again, it seems a bit more tempermental
So what's the deal with EFI? what are the choices, costs, peoples experiences, etc?

Not something that's happening anytime soon, but just for info...

[ArtechnikA]

Yeah,yeah, some folks go all gaga over the MFI setup.

I wasn't recommending MFI, mind you - it was just an observation that a big part of its power increase is the lack of intake restriction. It can achieve this because it does not measure airflow. The downside is that it 'knows' how much air is flowing because its cam is matched to the engine displacement and camshaft.

For a period in time where real-time computer control was unknown, it's pretty cool. Nowadays your average iPhone has more than enough CPU power to run a full engine management control system. MAP's and MAF's have essentially zero restriction (taking away one of MFI's last few advantages). Add in closed-loop feedback with an O2 sensor and there's no reason why you wouldn't want an EFI system - if you were starting today.

I'm keeping (and uprating) the MFI in my application because I am building a replica/homage of an earlier car for my own enjoyment - not because I believe it offers any kind of performance advantage.

[J P Stein]

This is a good discussion....

I have carbs. I like them, but have thought about something different for Huey and relatively daily street use.
I'd like to stay away from CIS - heard too many horror stories
Not big on MFI just because again, it seems a bit more tempermental
So what's the deal with EFI? what are the choices, costs, peoples experiences, etc?

Not something that's happening anytime soon, but just for info...

If I hit the lotto......

Jeff Gamroth has an EFI set-up that produces an astounding amount of HP & torque.

http://rothsport-racing.com/

Our latest Parade AX winner has this set up on his car, a 2.8L, and makes 285 HP and is tuned for autocross. G Fordahl told me that they gained 30ft/lbs of torque across the range but only 10 HP....they bumped it back for more torque.
How about an all stock internal 3.0L @ 250 hp.....the EFI & exhaust are the only changes...the motors are blueprinted, of course.

Around 8k installed & dynoed, I understand.

[IronHillRestorations]

As long as the carbs are optimized for the engine, you shouldn't give up too much or any HP over the CIS.

The CIS engine you've got is by comparison, low compression, and cams with virtually no overlap. It works well, but it's not the highest performance branch on the tree. CIS is a decent system for a street car, and doesn't have idle jets to clog up.

CIS and MFI have been lumped together, which from a performance perspective isn't correct. CIS and MFI are totally different systems. With MFI you can run a high compression engine, and cams with more overlap. The MFI pump puts out about 240psi at the injector which gives you killer throttle response, but the lack of any vacuum or intake pressure sensing can result in surging throttle response, ie part throttle down hill (low load) compared to part throttle up hill (load).