riddle me this

2961 Views 32 Replies 10 Participants Last post by Hass828, Jul 11, 2009

terrible_buddhist

Discussion Starter · Jul 8, 2009

the point of fuel injection is to get the fuel as close to the combustion chamber as possible...right? I mean, I know there are other reasons...but that is one of the main ones. right?

So in blown set up, why bother running EFI above the blower?

my follow up question is...in a draw thru Turbo set up, can you run a wet nitrous system into the manifold, or will it not be able to inject say 7 pounds pressure of fuel into a 10 pound pressure of boost and cause a lean out?

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s2k1

· #6 · Jul 8, 2009

You are thinking of EFI as a fuel system. Most "EFI" systems are really engine management systems. They control a lot more than fuel, things like ignition timing, boost control (on a turbo setup), dry NOS, data logging, etc. You could even set it up to measure water pressure in a jet, and log the data. On modern engines, they control things like constantly variable valve timing, drive by wire throttle, etc.
With more control over the ignition, you can really maximize the torque available from the engine by using a timing table that references RPM versus boost, and tune for MBT. Minimum (spark advance for) best torque.
An EFI system won't make more power than a carb, (unless one of them is tuned improperly) but will often make the engine more driveable.

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s2k1

· #8 · Jul 8, 2009

ap67et10 said:
in most aftermarket engine management systems you have a batch or bank fire setup. if it doesn't have a cam position sensor its not fully sequential. however even with a batch or bank fire you will in all cases have better fuel mileage and control of fuel deliver than any carb (givin someone that knows how to tune). in the really high dollar setups i guarantee you can find some lost power as you would have a cam sensor and crank sensor that will allow fully sequential fuel and spark delivery. so now you just created (in a v8) 8 individual engines that can be completely tuned to maximize its efficiency from that specific cylinder. its is crazy the kinds of things they are doing today with engines. but to say that a carb and efi are equal is rediculous. if we did not have computer contolled engines how would we ever have factory production engines that are getting crazy fuel mileage along with 500-600 hp...untouched?...not to mention in far less cubes then all of us do here.

our new jaguar XFR comes with a supercharged 5.0L...thats right 305 ci. and with 11.6pounds of boost puts down 510 hp and 460lbs tq. oh and it gets 15 mpg in town and 22 on freeway

efi is such a generic term, but just as said above a computer controlled engine has so much more to offer...if you know what you are doing. i have seen computer controlled setups becoming really popular in the last few years in the aftermarket...however there for a little while all i heard was neg feedback, and all of it was because the engine builder, tuner, or customer had no idea what they were doing and caused tons of dollars to be waisted. carbs are pretty simple and very effective, but given the right resources computer controlled is most definately my vote.

AP

If you are referring to my post, I said power, not driveability, emissions, or anything else. And, I was only referring to peak power.
Trust me, I am an EMS advocate through and through. Just finished wiring up a BITD 7200 race truck with a MoTeC M600 system yesterday.
Also, there are other ways to do sequential than with a cam position sensor.

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s2k1

· #24 · Jul 9, 2009

Hass828 said:
Ya want to bet ?

You guys check out this link from a well respected carb builder
http://www.pro-system.com/scoop92102.html

I read the link. Some info makes sense. For instance, intake air temp and emulsion of the fuel.
However, many are focused on A/F when talking about power. A/F doesn't make power, ignition timing does. A little rich or a little lean from your target A/F will not effect power too much. However, a few degrees of ignition timing will have huge effects! With an EMS, that is where one of the advantages is. The ability to control the ignition with much more detail.
For any of you that are afraid of EFI, or don't understand how it works, check this place out......
www.efi101.com

The people at Sterling Engines answered the very same question when I asked it. It's because with out running the blower wet, they ran into problems with the seals frying almost instantly.

I don't have much blower experience, but this is what i've always been taught is the issue. Not sure if that is the same case for the screw blowers or just the roots style huffers.

Oh yea, and an MSD 7AL3 wont light it off on the nos, needs to be a mag, good luck, Hass

It is pretty common for an MSD to be unable to light of the chamber in an engine running a fair amount of boost. The mag is not the only way either. A good CDI from a company like www.autronic.com.au or from www.mwignitions.com would be an excellent option for an engine using an EMS.

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