Quote:
Originally Posted by Keith58
... Like many others I am considering a switch from carb to EFI as being based in Scotland ...Any real life advice from experience would be much appreciated...
|
Keith (I am guessing from your screen name),
The blind from birth conundrum and the Knight's Templar admonition are unvarnished but just the way it really is.
The number of EFI users who have used more than one fueling model (i.e. Alpha-N, Speed Density or MAF style) can typically be counted on one hand with a lot of fingers missing. The problem is quite similar to the blind from birth conundrum. Most users will be enamored with how well the engine starts compared to carb(s) and loose sight of the tuning for drivability or MBT (maximum brake torque) timing or sometimes even max power.
When you ask the "satisfied user" a simple question about the enrichment strategy they used for accelerator pump replication, you will get a blank stare. When you ask them if they used a time based model, a wall wetting AE model or an EAE model, a wall wetting x-tau model or why they used one over the other, you will get a blank stare once again!
So lets go to another consideration. Ask them if the injectors were flowed to the SAE J-1382 standard blank stare time again. Its a dirty little secret in the industry that not all fuel injectors of the same part number actually perform the same. Sooo, who flowed the injectors, what were the conditions they were flowers under, were they corrected values or raw data, did they get high and low slope values for the injectors, what is the actual flow rate of the injectors, and of course lets not forget their short pulse behavior.
Aside from the blank stares you will get comments like why does that matter (to me) and I am sure the manufacturer addressed that for me along with the "I never heard of that before," commentary telling you quickly how valuable that opinion is.
There is a short way home for you that involves keeping the carb and either learning how to tune it (more time consuming) or buying someone who does (more risky). Alternatively you could get the MS3Pro hardware I described in post #3 which addresses all of these issues and a boasts a lot more (not meaning to terrorize you) allowing you to do a spectacular tune. BTW The MS3Pro lets you choose Speed Density or MAF fueling models, blending Alpha-N where it is better suited than the other two.
Spend $199 and buy Greg Banish's
Advanced EFI Tuning Series DVD's <= clickable. the DVDs have six hours of training, half on prepping the car and half on tuning fuel, timing, air flow and other maps in the ECU. Learn not only what it is about but how to do it right! More importantly learn it from the guy Ford, GM and Chrysler go to when they are in a jamb.
Go buy the MS3Pro ECU and associated gizmo's from DIY Auto tune. Do it yourself and know not only that it is done correctly but how to do it correctly.
BTW, nowhere in any of these posts have I commented on the fail safes the aftermarket ECU brings to the table to protect your engine or in the case of traction control you and your car, or in the case of power adders like nitrous, turbos or blowers the tools to do the job correctly and I've just scratched the surface.
Tony and I are trying to help you avoid stepping on an engine fueling land mine hidden below ground level that is for all intents and purposes invisible. You are currently struggling with a carburetor that is mis-behaving. Tuning a carburetor has fewer tunable variables and is less complex than tuning an EFI system.
Tony's representation of a speed density system as an electronic carburetor is spot on. He did not represent it as inexpensive or anything other than an electronic carburetor. It gives you a digital adjustment capability for what effectively were accelerator pump(s), jets, power valves and air bleeds. It also gives you digital precision and adjustability. Most importantly it does not give you any way to measure the air mass being consumed by the engine which is foundational to the tuning process. Remember AFR is pounds of air divided by pounds of fuel.
Virtually all the speed density systems will provide some level of self learning (read tuning) capability adequate to minimally get the car drivable if not better. That's the condition you need to drive to the dyno shop and get the tune properly done. Once you have the car properly tuned it will perform admirably for the ambient air conditions at the time of tuning.
The further you get from those conditions the further out of whack your tune will become. Ambient air related changes will only affect a speed density system, they will not affect a MAF based system it's really that simple. It doesn't mean speed density does not work, it does! However, when atmospheric conditions change so to will the quality of your tune. This is not be the case with a MAF based system.
You are essentially out on the fringes of the Cobra universe effectively by yourself. That means you will either need to learn how to manage the tune for your engine or you will need to travel and pay money to someone else, who you
hope will be able to help you. This should sound like the pickle you are currently in and stymied by with your carburetor.
Whether you ultimately embrace a carb solution or an EFI solution you are going to need to send yourself to school and learn how to manage your engine's fuel delivery system. If you elect to do this with an EFI system I highly encourage you to use a MAF based system and spend the money to learn how to use it you will be muuuuuch happier in the end.
Choose wisely ...
Ed