Hey NZ,
This is a little lengthy, so I apologize up front. Anyways, this is like deja-vu. I was doing exactly what you are almost 2 years ago
In any event, I decided to go the EFI route for a few reasons, starting, idling, and lack of maintenance. Any carburetted vehicle I have ever owned ran awesome the first 3-4 months then they required minor carb tweaking and I just don't have the knowledge to successfully do this. EFI isn't as finicky and in the event I do need to tweak it, I can call Tim @ For Hemi's Only and he sends me the file to upload. Oh yeah, don't forget about fuel economy
Anyways, when I spoke with Tim about going EFI, he initially was against the idea. He has been building Hemi's for quite a while and has the perfectly tuned package using the carb setup. After some prodding, I convinced him to give it a shot although he probably thought I was crazy. The biggest problem that he ran into was getting the hemi to breath. Any EFI intake he tried just wasn't getting enough air into the engine and overall the build was performing worse than the carb setup using the Stage V intake, both in overall power and in the power curve.
By this point in time, I could sense a change in his opinion about the EFI as he could definitely see the advantages that I wanted above. So being the fanatic/genius that he is he set off to modifying the Stage V intake in an attempt to get this horse the oxygen it need to really stretch its legs.
So, after a bunch of research and development, including modification of the Stage V single plane dual four intake, adding 2 1000 cfm throttle bodies, choice of the Big Stuff GEN3 PRO SEFI electronics and getting 2 different EFI experts in to program the system along with taking the engine on a trip down to Michigan into the OEM dyno lab, I get the following 2 emails in Dec 2006.
"The EFI we are now using will outperform the carbs we normally use. We made roughly 650hp on carbs, and are 30hp above that now. We are making way more torque all the way through. This EFI allows us to use huge dual 1000cfm throttle bodies without suffering the effects that oversize carbs produce. You will also get fuel economy unheard of with carbs, as we are able to select and adjust the fuel/spark to optimum settings. Carbs have to be over-jetted, as they are not as precise or fast acting."
"A quick update on your engine. We brought in a retired engineer from GM who did all their EFI and race car programming. We first wanted to compare data from Michigan against our own dyno, and they were virtually identical. He wanted to look at our fuel and VE data. With a few of his changes to the computer program, your engine power increased to almost 700hp. He was rather shocked to see how much power a hemi makes with rather mild cam timing. We had to adjust our dyno brake twice to increase the load, as part throttle power was up also."
At this point Tim mentioned to me that he was so impressed with the EFI build he was going to put it into his own vehicle. That to me was the icing on the cake and as Tim put it, he thought I now had the most advanced EFI hemi on the planet.
Oh yeah, there is no curve left in the power curve anymore as you can put a ruler to it.
I hope this helps. Cheers.
dray
