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hobbs switch fuel management

Old 08-09-2006, 12:18 AM
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Default hobbs switch fuel management

hi guys

i've been given a free (old) car and have been sourcing some parts for it

i'm going to be running more than factory boost and will of course need extra fuel

now as the car was free, myself and my mate are trying to do this turbo project on a small budget

for fuel management, we were considering using rpm + pressure activated extra saturated injectors (we have some spare saturated injectors laying around already)

i've done some searching but havent got very far in the way of peoples experience using hobbs switch for a bit of fuel management, i was just wondering if people had acheived satisfactory results using them?

cheers
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Old 08-09-2006, 12:24 PM
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Default Re: hobbs switch fuel management

Sounds like I need to get rid of ERL MF2 injector controller so he can do exactly what he needs to do.... Still not as good as chipped ECU but its not all that bad either. Pressure switch wont work well. How will you control the injector flow?
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Old 08-09-2006, 08:47 PM
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Default Re: hobbs switch fuel management

its for an n12 pulsar e15et. i'm from australia and i dont know if you guys have those cars over there, and i'm extremly unfimiliar with the cars you talk about on this forum (are the majority hondas??)

anyhow it is just a rough idea at this point in time

the stock ecu can't be chipped

and there wouldnt be much control of injector flow at all. it would just open when the rpm and the hobbs switch both trigger and dump fuel into the manifold. my mate has a wideband and we were just gonna run with that to try to work out if the injectors are going to be wayyy too big or the rpm trigger too low (adjustable tho).

i thoght this method may have been used before...

considering the car cost me nothing, the entire engine + loom + ecu + everything (minus turbo) cost me less than $150USD, i didnt want to go out and spend $300 on a piggy back ecu, to which i then have to hire a dyno to tune for a similar price. if i'm venturing into new ground, then i'll give it a go. worst comes to worst, i have a tacho i didnt essentialy require

cheers guys
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Old 08-10-2006, 09:26 AM
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Default Re: hobbs switch fuel management

Problem is you wont be able to control the fuel at all rpms. so in your case, you will have a desired rpm and then this pressure switch. when you activate it and then watch your wideband you may have 500 rpms where the car ran real well and then just before that rpm the car was lean and then following that set rpm it was pig rich and bogging until you either had enough boost to lean it out or high enough rpm to consume all the fuel. You basically would only be able to enjoy this car at the rpm in which you find 11:1 -11.8:1 AFR and as said that will only last a short amount of time.

I have an ERL MF2 fuel controller that is rpm and pressure sensitive. It has little trim ***** (pots) inside of it that when the rpm you are at requires more or less fuel you just turn that rpm **** until you get to the next rpm and then you see if that rpm range is good with the wideband. If not adjust that rpm ****. It has rpm ***** from 1000 rpm all the way to 9000 rpm. Currently it controls 2 injectors but the company says it can control four. This is at the least what you would need to control fuel. Then there is the timing side. You will still need to control timiing. A boosted car will have different timing that your N/A car. How will you control this? An MSD BTM would work as a bandaid on your problem. Again, this isnt the best solution as it just pulls the same amount of timing across the RPM range as soon as it starts sensing boost. You set the desired amount of timing to be pulled. Both of these items would run you about $100-200 used and complete. This probably isnt the best solution for you car unless that isnt that much money.
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Old 08-10-2006, 07:52 PM
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Default Re: hobbs switch fuel management

hmm i have always been concerned with this idea that it will run horribly rich for a period of time, or lean but i was under the impression that people had done this before, maybe my info is wrong!

this ERL MF2 sounds quite interesting! looks to be exactly what we want, i've never heard of it in this country! i'll definately be keeping an eye out on forums and american ebay to try to find some at good prices

the thing is, people have run high amounts of air flow through larger turbos @ 15psi (stock pressure is only like 9) with their management being a pump and a reg (1:1.7 ?). run 13 sec passes too!!! stock ecu / injectors etc. i wonder if going down the path of piggy back ecu / more injectors is a worthwhile effort.

i doubt timing is an issue as it will still retain the factor ecu mapped for boost

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Old 08-12-2006, 08:16 AM
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Default Re: hobbs switch fuel management

I have a ERL MF2 that I never used. I would be willing to sell it to you cheap to help you out but how much would shipping be?

Contact me by email if you want more info.... [email protected]
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Old 08-12-2006, 09:11 PM
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Default Re: hobbs switch fuel management

Saturated injectors's don't like being run at 100% duration all the time. A boost pressure switch is going to do nothing more than turn them on at X pressure.
The old standby is using cold start injectors (Which are small flow, but on most small engines using a stock turbo, can give enough fuel for a couple of psi of boost) Or use it to turn on an n2o solenoid & fogger jet.

That's a 100% fine, cost effective way to add fuel... Provided you're staying with the stock turbo & you turn the fueling on before you need it. (And can keep the stock ECU from hitting a fuel cut from too-much boost.) Where it becomes trouble & you need to run real injectors, is when you're using a larger that stock turbo, and wind up needing more fuel that you can tune for with one boost pressure switch.
At which point it becomes a question of, "Would you rather spend the money on multiple switches, and fuel setups, or simply adding an extra real injector, and some form of basic management".





Regardless. You can't run a saturated injector on a boost pressure switch. The injector is not going to tolerate that long term.
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